PROGRAM ADMINISTRATION AND INSTALLATION DESIGN
OF THE
NUCLEAR REACTOR PROJECT
AT
NORTH CAROLINA STATE COLLEGE

July 5, 1950

Clifford K. Beck
and
Arthur C. Menius (on Theoretical Calculations)

George N. Webb
Arthur W. Waltner (on Instrumentation)

P. B. Leonard
F. H. Stinson
J. D. Paulson (on Drafting)

RESTRICTED DATA
This document contains restricted data as defined in the Atomic Energy Act of 1946.

CAUTION
This document contains information affecting the National Defense of the United
States. Its transmission or the disclosure of its contents in any manner to an
unauthorized person is prohibited and may result in severe criminal penalties
under applicable Federal laws.

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DISTRIBUTION OF REPORT
Series A - 25 Copies
68 Pages: i to vi and 1-62; 13 Figures

	Copy No.
U.S.A.E.C. Joseph Platt	1 - 6
U.S.A.E.C. Herman Roth	7 - 10
U.S.A.E.C. Declassification office	11 - 16
Dean J. H. Lampe	17 - 18
O.R.N.L. Richard Stevenson	19 - 20
Clifford K. Beck	20 - 25

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TABLE OF CONTENTS
• Abstract v
• I. The Nuclear Reactor Project 1
• • A. General Background 1
  • B. Administrative Arrangement 2
  • C. Classification 4
  • D. Safety and Security of Fissionable Fuel 5
• II. The Nuclear Reactor 7
• • A. General Regional Conditions 7
  • B. Building 12
  • C. Ventilation, Sewage, Waste Disposal 14
  • D. Reactor Design 16
  • • 1. General 16
    • 2. Shielding Arrangement 17
    • 3. Fuel Container 18
    • 4. The Cooling System 20
    • 5. The Nuclear Fuel 22
    • 6. Reactor Envelope 24
    • 7. The Reflector 26
    • 8. Second Liquid Catch Basin 27
    • 9. The Lead Shield 28
    • 10. Safety and Control Rods 28
    • 11. Instrumentation and Control 29
    • 12. Operating Level; Radiation Fluxes; Reactivity of Solution 36
    • 13. Thermal Column 39
    • 14. Sample Exposure Ports 39
    • 15. Sampling Replenishing Lines 41
    • 16. Solution Level Indicator 42
    • 17. Gas Disposal 43
• III. Reactor Hazards 48
• • A. Normal Hazards 48
  • • 1. Radiation 48
    • 2. Radiochemical and Radiophysical Hazards 50
  • B. Emergency Hazards 51
  • • 1. Leak or Rupture in the Reactor 51
    • 2. H2 - 02 Explosion 52
    • 3. Inadvertent Removal of Control and Safety Rods 52
    • 4. Failure of Water Supply 56
    • 5. Escape of Radioactive Gases from the Stack 57
    • 6. Effect of Water Removal for the Cooling Coils 59
    • 7. Addition of Water or U235 Solution to the Free Volumes
      in the Reactor 59
  • C. Catastrophic Hazards 60

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TABLE OF CONTENTS (Continued)

Figure	1. Topographic map of Raleigh
	2. N. C. State College Campus
	3. Schematic Floor Plan of Reactor Building
	4. Reactor Shielding Skeleton
	5. Complete Reactor Shielding Assembly
	6. Fuel Container
	7. Reactor Envelope and Sampling Tube
	8. Horizontal Cross Section through Thermal Column
	9. Exposure Ports
	10. Liquid Level Indicator
	11. Decay of Reactor Product Gases
	12. Gas Disposal System - Schematic Diagram
	13. Five Second Rod Removal Emergency

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ABSTRACT

North Carolina State College of The University of North Carolina has pro-
posed that a "water-boiler" nuclear reactor be built and operated on the college
campus as an unclassified tool of instruction and research. A brief statement of
the reactor project objectives and administrative procedure is made in this report.

The main body of the report concerns the general design and arrangement of
the reactor. Most of the design has been based on ideas and extension of ideas
and emperical data from Los Alamos and Oak Ridge reactors. The Los Alamos "water-
boiler" has operated entirely satisfactorily for several years, and the Oak Ridge
"Homogeneous Reactor", though not yet built, has received intensive study. The
ideas and experience with these units have been incorporated into the design of the
State College reactor, with minor changes as necessary and with the addition of
extra features wherever the inherent safety of the machine or its resistance to
sabotage could be improved.

A tabulation has been included of hazards which could result from operation
or misoperation of the proposed unit. Many safeguards have been included to prevent
injury through such obvious and inherent hazards as exposure to radiation from the
reactor and carelessness in handling radioactive materials in routine operations.

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It is demonstrated that pressure rupture or explosion of the reactor by
nuclear reaction is impossible. The "bubble effect" and a large negative tempera-
ture coefficient prevent any runaway whatever, and insure automatic upper limits to
the level of operation, even if all normal and emergency safety devices fail.

The only important danger inherent in the reactor installation lies in
sabotage through non-nuclear explosion, aimed at wrecking the reactor and blasting
the radioactive solution and attendant vapors and gases over the surrounding area.
Even a catastrophe of this sort would cause little damage beyond that involved in
the catastrophic event itself. A number of precautions against sabotage are in-
cluded in the design.

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In recognition of the vital role that nuclear phenomena and processes
flow have and increasingly will have in our society, and in discharging her
responsibility to the students of the State and Nation in providing training
opportunities in essential vocational fields, The North Carolina State College
of the University of North Carolina has initiated a training program in
Nuclear Engineering for qualified students. This curriculum^a1, which provides
training opportunities at both the undergraduate and graduate level, consists
of (1) classroom instruction in theory and basic information, (2) extensive
laboratory practice of nuclear technology, and (3) research facilities and
opportunities for advanced students.

One of the basic units intended for use as the heart of the advanced
instructional and research programs is a low-power nuclear reactor, of the
uranium "water-boiler" type. It has been proposed^a2 that this reactor be built
and operated on the State College campus, by State College, as an unclassified
tool for research and instruction.

In June, 1950, a contract^a3 was given by the Atomic Energy Commission
to N. C. State College, directing that the design of a reactor be drawn up,
together with a description of the proposed method of operation and analysis

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of the potential hazards associated with the machine. The report below contains
the items and information stipulated in the contract.

It is intended that the Nuclear Reactor be designed, constructed,
and operated by North Carolina State College with the consent, advice and
assistance of the Atomic Energy Commission, the necessary finances being
supplied by State College. The Commission will furnish information and
assistance in the design stage; it may furnish certain instruments, materials
and purchasing facilities during the construction period; and will supply the
fissionable fuel necessary for operation.

At State College, the nuclear engineering training program and the
Reactor Project will be a part of and under the direction of the Physics
Department. During the design and construction phases of the project, the
money necessary for these activities from whatever sources obtained, will be
placed in the State Treasurer's office, along with other college funds, in a
separate account earmarked for the Reactor Project, and made available to the
Physics Department for use in obtaining personnel services, supplies, travel,
etc.

Responsibility for operation of the Nuclear Reactor will also be assigned
the Physics Department. It is intended however that the machine serve as a
tool for instruction and research not for the Physics Department only, but
also for a large group of other departments, organizations and institutions,
many perhaps not even connected with State College. It will be necessary

therefore to arrange schedules of operation, assign priorities to projects,
access costs, etc. No definite rules and regulations for handling these
matters can be made at this time. A few general guiding principles may be
stated, however;

• 1. The general responsibility for the entire operation of the Reactor
  will be allocated to a Scientific Director (named in the A.E.C. contract
  as Dr. Clifford Beck, Chairman of the Physics Department). The
  designation of subsequent directors, in general, will be agreed upon
  by both State College and the A.E.C.
• 2. An advisory Committee, selected by the Scientific Director, will
  assist in the establishment of policies, rules and regulations
  governing operations.
• 3. The widest and most extensive use of the Reactor will be en-
  couraged, and its availability for use on acceptable projects will be
  maintained at the maximum consistant with safety, efficiency of
  operation and finances.
• 4. Finances for operation will be available for a specially earmarked
  fund in the State Treasury. Income from sponsored projects involving
  use of the reactor, from charges for reactor usage, and from all other
  sources will be placed in the Reactor Account in the State Treasury for
  subsequent use in the Project.
• 5. Individuals or groups desiring irradiation of samples or other
  use of the reactor, not involving experimentation on human beings,
  must produce evidence to the satisfaction of the Scientific Director
  or his designated representatives that they are competent to handle
  radioactive materials and that their facilities are adequate.
• 6. When projects involve experimentation on humans, prior approval of
  the project must be obtained from the Atomic Energy Commission's
  Isotope Branch, in addition to the stipulation above.

• 7. Careful and complete records will be kept of all reactor operations,
  sample irradiation, etc., and of all individuals participating in
  experimentation involving the reactor.

It is the basic intent that the Nuclear Reactor be operated as a
completely unclassified project, on research problems which also are unclassified.
Provisions will be made within safe limits for public observation of the reactor
and its operation. It will be the intent that students and research participants
having access to the reactor and its radiations, but not to classified operation
or construction details of the installations (if any), may participate freely
in the project upon satisfactory evidence to the Scientific Director and the College
Administration of their American loyalty.

Those persons who, because of their intimate connection with the design
and behavior of the reactor must have knowledge of classified information, will be
investigated by the F. B. I. and be given security clearance by normal procedures
followed by the Atomic Energy Commission.

Despite the desire to operate the Reactor as completely unclassified
as possible, it will be the strong intent of State College to guard vigilantly
against the release of classified information to any unauthorized individuals.
The Scientific Director and several of the college staff members associated with
the project will maintain "Q-clearance" status with the Atomic Energy Commission
and will keep up-to-date on declassificable information. In the course of any
investigation, whether considered unclassified or not, should any classified
information be encountered, this will be declared classified and further disclosure
to unauthorized individuals will not be permitted except through regular Commission
channels. Any information of doubtful classification will also be handled as
classified and submitted for clarification of classification status.

The enriched U235, in either solid or liquid (sulfate) solution form,
will be delivered to State College at the appropriate time for use in the
reactor. At least three separate containers, of less than 350 g (U235) each,
will be used in transporting the material. The containers will be stored in
fire-proof, combination-lock, storage receptacles, with at least 24" between each
container. In all operations involving fissionable material, no more than 350
grams will be handled at one time or allowed to come nearer than 24" to other
fissionable material. These same rules for handling and storage will be followed
at all subsequent times.

The sulfate solution will be placed into the reactor cylinder through
the sampling tube extending to the top of the concrete shield. (Described later.)
When all the solution has been added, the safe-door covering the end of the
sampling tube will be closed and locked. All beam ports and other openings through
the concrete shielding will be closed by combination-lock, wall-type safe-doors
built into the concrete shielding. Every external opening through which access
to the inside of the concrete shield could be gained will be closed and locked.
Thus, the fissionable fuel will be contained in a closed (stainless steel)
system located completely inside massive concrete shielding in which all external
openings are securely closed.

When the reactor is in operation, or when apparatus is mounted permanently
into one of the beam ports, the safe door on one or more ports will be unlocked
and open. At other times, all openings into the shielding will be securely closed.

In addition, when members of the research staff are not present, the
electrical gear at the control console, to all parts of the reactor, to the crane,
and to other equipment relating to the reactor, will be de-energized and the
switches will be locked.

The reactor building, especially the Reactor Room, and the gates in the
external area fence will be locked, and the area around the building will be well
lighted at night. The college watchmen will direct particular attention to this
building on their rounds of the campus.

The design of the assembly, the precautions listed above and the ex-
tremely radioactive nature of the material after initial operation, are believed
entirely adequate to insure the physical security from theft of the fissionable
material. No nuclear fuel, other than that in the reactor itself, will be
located at this site. The danger to be guarded against, if any, is in sabotage
aimed at wrecking the reactor or spreading the radioactive fuel around the
neighborhood by non-nuclear (e.g., T.N.T.) explosive blast. This cannot be
accomplished unless the explosive is gotten inside the concrete shield. It is
proposed that the precautions listed above and the design of the reactor will
be adequate to prevent this. The Atomic Energy Commission may, however, prefer
to place on duty at the site a full-time guard or perhaps a guard on duty when
members of the research staff are not present, in addition to the above pre-
cautions.

Raleigh, North Carolina, lies in Wake County, at latitude 35°-47'-20"
north and longitude 78°-40'-40" west. The population is about 65,000.
Raleigh is the capitol of the State, and governmental business engages a
goodly portion of the inhabitants. Meredith College (for women), Peace Junior
College (for women), St. Mary's Junior College (for women), the State School
for the Blind, and N. C. State College of the University of North Carolina
are located in the city. Convergence of highways and railroads places
Raleigh in good strategic location for a thriving goods outlet and
commodity distribution center of the State. There are few manufacturing
and heavy industries in the the city.

The campus of North Carolina State College lies toward the western edge
of Raleigh (Figure 1). Hillsboro Street extends westerly from the Capitol
Building at the center of Raleigh, and, at distances between 1 1/2 to 2 5/8
miles from the Capitol, forms the northern boundary of the college campus.
The campus thus extends east and west 1 1/8 miles along the south side of
Hillsboro. The north-south dimension of the campus proper is about 1/2 mile.
The tracks of the Seaboard and Southern railroad run through the middle of
the campus, roughly parallel to Hillsboro Street. Between Hillsboro Street
and the railroad, therefore, is an area of 1000 to 1500 feet in width and
1 1/8 miles in length. Most of the college buildings, except new dormitories
and athletic buildings, lie in this tract. The new dormitories and gymnasia
lie south of the railroad.

There are four general functional groupings of buildings on the campus.
At the eastern end, toward Raleigh, are the College administrative buildings

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and the classroom buildings of the Basic Division. Next westward lie the
classroom buildings and laboratories of the Engineering Division, followed
by the buildings of the Agricultural Division. Finally, on the western end
of the campus, are located the structures belonging to the Textile Division.

The land comprising the campus of State College is gently rolling, and
varies between 350 and 420 feet above sea level (Figure 1). "The undisturbed
soil in this area consists primarily of a residual soil developed from
metamorphic rock classified by geologists as Mica Gneiss. This soil is
classified under the Agricultural Soil Survey System as a "Cecil Clay Loam."
It is very plastic, highly impervious, inorganic, red clay-tough near the
plastic limit. In the proximity of Rocky Branch and its tributaries there
occurs alluvial soil of variable nature. The occurrence of natural drainage
ways is limited to Rocky Branch and its tributaries. This stream discharges
into an artificial lake, known as Pullen Lake. The highly impervious nature
of the soil, underlaid with bedrock, precludes the frequent occurrence of
underground drainage ways."^b1

Certain meteorological data have been recorded at Raleigh for about 60
years. Certain of these data of interest in the operation schedules of the
reactor are tabulated below:

• (a) Wind velocities and directions:
• • 1. Calm 11%

• • 2. 4 - 15 mph. . . . . . . 83%
  • • Southwest 14%
    • Northeast 10
    • South 8
    • North 7
    • SSW 7
    • West 6
    • Northwest 6
    • All other 25


• • 3. 16 - 31 mph. . . . . . . 7%
  • • SW 1.3%
    • NW 1.2
    • All other 4.5


• • (b) Precipitation
  • 1. Average yearly rainfall 46.5 inches.
  • 2. Average yearly snowfall 7.6 inches.
  • 3. Average wettest month: July 5.8 inches.
  • 4. Average dryest month: November 2.3 inches.
  • 5. Greatest rainfall in 24 hours: September 1929 6.66 inches.
  • 6. Lowest average humidity: Feb., Mar., April - about 48% at 1 PM.
  • 7. Highest average humidity: July, August - about 58% at 1 PM.


• • (c) Temperature
  • 1. Yearly average daily maximum 70°F.
  • 2. Yearly average daily minimum 50.7°F.
  • 3. Highest monthly average: Maximum 87.9 July.
    Minimum 69.2 July.
  • 4. Lowest monthly average: Maximum 50.9 Jan.
    Minimum 33.3 Jan.
  • 5. Record highest, July 1940 104°F.
  • 6. Record lowest, February 1899 -2°F.

• • (d) Weather conditions (over 60 years), average number of days per year
  • • 1. Clear 133 days/year.
    • 2. Cloudy 118 "
    • 3. Partly cloudy 114 "
    • 4. Rain 0.01 inches or more 120 "
    • 5. Snow 0.01 inches or more 4 "
    • 6. Thunderstorms 41 "
    • 7. Heavy fog 12 "
    • 8. Maximum temp. 90°F or above 37 "
    • 9. Minimum temp. 32°F or below 50 "

Inversion layers and other unusual meteorological effects occur, but data
on the frequency and extent of these conditions are not readily available.
Additional data are being obtained.

The Nuclear Reactor will be located in one or the other of two proposed
positions on the State College campus. The two locations are shown in
Figure 2.

Position A: South of old Zoology Building. It is planned that the old
Zoology Building shall be removed, but this is not likely to occur in less
than three or five years. With the building removed, this site would
constitute the optimum choice for the location of the Reactor Building.
It is intended that the Reactor facility be located in the space south of
the old Zoology Building and north of the railroad, between the Diesel
Building and the Riddick Laboratories. The facility will be so designed
that (a) suitable interim operation until removal of old Zoology can be
achieved and (b) ultimate expansion, after removal of the Zoology Building,
into an optimum facility can be undertaken.

Should it turn out that the space behind old Zoology is insufficient for
an interim Reactor facility, or should further study reveal a strong un-
desirability from the safety standpoint of crowding the Reactor facility
for interim operation into cramped space immediately adjacent to a classroom
building, then the Reactor facility will be located in Position B.

Position B: North of Old Zoology Building. The Reactor will be located
between Daniels and Polk Halls, north of University Drive, if the space
south of old Zoology proves unsuitable. If the Reactor is placed in this
location, a three or four story new physics laboratory building will also
be placed in this area in order to reestablish an architecturally acceptable
landscape plan for this portion of the campus. The new building, as shown
on Figure 2, would extend in an east-west position between Polk and Daniels
Halls, in line with the north ends of these two buildings. Part of the
Reactor laboratories would be located in this new building.

In either of these two locations the environmental conditions are
essentially the same. Six large buildings are nearby: Withers, Daniels,
Riddick, Diesel-Mechanical, Polk, and, of course, Old Zoology. Patterson
Hall is directly north, 1020 feet from Position A and 980 feet from Position B.
The elevation is 410 to 415 feet above sea level: one of the highest
elevations in the entire neighborhood. The general slope is south, east
and west from these locations, 2000 feet to the east and 1500 feet to the west
respectively are located the troughs of north-south surface drainage ways.
In the west trough there is also a small underground water channel. There
are no other known surface or underground flow channels in the vicinity. The
drainage ways from this area lead eventually to Rocky Branch.

The non-college activity nearest the proposed reactor location is a
small shopping center on Hillsboro Street, 2200 feet north. East, south and
west the college property extends 3000, 6000, and 3000 feet respectively from

the reactor site. The nearest college dormitories are 2300 feet southwest;
these are at 40 feet lower elevation than the reactor site. The Seaboard
and Southern Railroad runs east and west at 500 and 1200 feet south re-
spectively of the two proposed reactor sites. The railroad elevation is
30 feet lower than that of the reactor site.

A building is being designed to house the Reactor and the activities
associated therewith. Figure 3 shows sketches of the functional components of the
proposed building. The finished design may have somewhat different floor plan
from that shown, but it is intended that it contain the four essential components
shown:

• 1. The Reactor Room. The octagonally shaped reactor will be located in the
  center of an octagonally shaped room, with 25 feet of clear space between
  any side of the reactor and the nearest wall of the building. The floor
  level in the reactor room (and the bottom of the reactor assembly) will be
  8 feet below ground level. Horizontal radiation beams from the reactor will
  pass through narrow openings in the building walls to underground radiation
  traps buried outside the building. Overhead space in the unceiled room,
  extending to the roof 40 feet above floor level will provide ample space for
  a 10 to 20 ton crane, blowers, filters, and ventilation equipment, and supports
  for the gas-stack which extends above the roof of the building. The wall of
  the reactor room will be of 16" masonry and steel (for the crane supports)
  except on one side adjacent to the Control Observation Room where a large
  16-inch water observation window will be located. Numerous crash-doors
  will provide emergency exits from the reactor room. Blowers will draw in air
  through ventilators in the walls, filter it, and discharge it to the stack
  above the roof. The ventilators will be arranged for outside closure, if

• necessary, so that the entire Reactor Room can be sealed up from the outside
  to prevent other than minor escape of gases from inside in case excessive
  gas contamination should occur in the room.


• 2. The Research Wing. Adjacent to one aide of the Reactor Room a laboratory
  wing devoted to pre- and post-handling of exposure samples involved in
  research projects is proposed. The laboratories in this wing will have
  facilities for radio-chemical work and radioactivity measurements, in
  addition to the usual research facilities. The electronic instrument rooms
  will be air-conditioned. Exhaust ventilation of the other rooms through
  ducts leading to the building stack will be provided. Facilities for
  checking and eliminating radioactive contamination to hands or clothing,
  and for lockers, clothes-changing, scrubbing, etc., will be arranged near
  the normally used entrance to this wing.


• 3. The Student Wing. A second laboratory wing adjacent to another side of
  the Reactor Room (opposite the Research Wing) will be equipped for instruction
  and training of students in a wide range of nuclear techniques. The wash
  room ventilation and laboratory facilities of this wing will be similar to
  these in the research room. Activities of much lower level will normally be
  present in the student wing.
  The laboratory wings will be designed for later addition of second
  stories, if needed.


• 4. Control-Observation-Administrative Area. One uncontaminated area adjacent
  to the Reactor Room will house the control console, the calculations, records,
  operations offices, a conference room, storage rooms (for uncontaminated
  supplies and equipment), an observation room, and one or two offices for
  the reactor staff.

Large blowers located high above the reactor in the Reactor Room will
draw air via ducts from all areas of the building through filters, and
discharge it to the building stack which will in turn discharge the air into
the atmosphere 25 feet above the roof of the highest buildings in the nearby
area. Within the building, therefore, air will flow from areas of low
radioactivity toward the area of highest activity. It is not intended that
the stack will be used for routine disposal of radioactive gases into the
atmosphere. These will normally be handled in other ways as described
below. Traces of activity or occasional inadvertent small gas releases may
accompany or contaminate the ventilating stream of the air through the
blowers to the atmosphere. The stack discharge is placed high in the atmos-
phere to provide safe disposal of these traces and infrequent inadvertent
releases. Careful and continuous monitoring of the ventilating stream will
be maintained. The source of any increase in activity will be promptly
located and handled by prescribed methods.

Radioactive liquids and solids will not be permitted to enter the city
sewage system. Three separate sewage systems will be provided in the
building. (a) Waste from the toilets, storm sewers, drinking fountains,
etc., will go directly into the city sewage system. (b) Drain lines from
the laboratories or any area in which radioactive materials are handled will
go to one of two underground (but accessible) holding tanks, and from there
to the city system. Radioactive solids or liquids will not normally be
placed in these drain lines. It is possible, however, because of their
proximity to working areas, that accidental spills or disposal of radioactive

materials may find their way into these lines. Therefore, continuous
monitoring at the entrance to the holding tank will be maintained; and should
appreciable quantities of radioactive material inadvertently reach the tank
from the laboratories in the building, it will be held there and handled by
prescribed methods, and then be allowed to enter the city sewage system only
under predetermined safe conditions. Meanwhile the drainage from the
laboratories will be switched to the second holding tank. (c) Short-lived
radioactive materials may be dispatched down one or two special drains to an
underground (but accessible) holding tank, which has no connection with the
city sewage system. When the activity has decayed sufficiently, the material,
by positive effort (not automatically), may be disposed of as non-active
waste.

Long-lived materials of solid or liquid nature will be accumulated in
closed, shielded, non-breakable containers designed for safe subsequent
transportation to Oak Ridge, Tennessee for disposal. Radioactive gases
will be accumulated in non-breakable cylinders, or absorbed in liquid or
solid absorbents, and handled as above.

Thus, no activity whatever above trace level will enter the city sewage
system, or be dispersed into the atmosphere or into the ground.

The reactor assembly consists of the reactor itself which is a stainless
steel cylinder containing a uranyl sulfate solution, the graphite reflector,
a limonite or barytes concrete-lead shield, a graphite thermal column, sample
exposure-neutron beam ports, control and safety rods, cooling coils, and
auxiliary apparatus and systems. Each of the major component parts will be
described separately below. The overall design is intended to produce a
simple and relatively inexpensive instrument that will provide maximum useful-
ness and flexibility, and minimum potential hazards. The water-boiler type
of reactor was chosen because of its simplicity, its proven usefulness, its
inherent safety characteristics, and the long experience of satisfactory
operation of the Los Alamos unit. With this type of reactor, a relatively
high radiation flux can be obtained with simple construction and equipment.
The two chief disadvantages of the liquid-type of reactor are (1) the mobility
of the fuel creates a design problem in avoiding loss if leaks should occur,
(though the mobility is also an advantage in that fuel transport, handling,
etc. by remote control, through pipes, pneumatic pressure, etc., is
relatively easy,) and (2) decomposition by radiation of the fuel solution
into gaseous products creates problems of gas disposal and solution replenish-
ment.

Since this reactor will be operated in the relatively populous environs
of a college campus and as an unclassified establishment relatively accessible
to the public, an attempt has been made to incorporate into the design
(1) exceptionally large safety factors against potential hazards and
(2) unusually extensive precautions against sabotage.

The major volume of the reactor assembly consists of concrete shielding.
The shielding is designed to perform the primary function of attenuating to
a safe level all radiations from the reactor and its accessories. It is
intended that a "heavy" concrete will be used; i.e. one in which the usual
crushed stone or gravel aggregate is replaced with a metallic ore which
possesses greater radiation attenuating ability. Limonite (iron ore) or
Barytes (Barium Sulfate-Iron Oxide) aggregates are being considered.

A lead shield (described later) will surround the reactor inside the
concrete shielding. Using shielding data empirically obtained at Oak Ridge
and Los Alamos and calculating the attenuation of radiations expected from
the reactor, it is found that a total of 30 inches is sufficient to reduce
the reactor radiation to a safe level. However, because of various pieces
of apparatus to be imbedded in the shield, and to provide an adequate margin
of safety, the concrete around the reactor will be made 6 feet thick.

The concrete in this particular assembly performs several secondary
functions in addition to the primary function of attenuation; (1) It provides
security of the fissionable material against theft. Hence, the design must
minimize accessibility to the interior in which all parts of the reactor
system are enclosed. (2) It is the primary defense against possible attempts
to sabotage the installation, hence, no openings may be left into which
explosives or other damaging materials could be placed. (3) It houses the
auxiliary systems of the reactor (exposure ports, control, cooling, gas
disposal, etc.) and these much be reasonably accessible in proportion to
their demand for use or maintenance.

Numerous channels and openings are provided in the concrete shield.
The entire shield is octagonal in shape, 17 feet in diameter and 9 1/2 feet
high. The assembly is composed of an octagonal poured concrete base, 18 inches

thick and 17 feet across and two poured concrete super-structure sections
comprising three octagonal faces in each on opposite sides of the base. The
super-structure extends 96 inches above the base slab, (Figure 4). Between
the two poured concrete super-structures a large open channel is left. This
opening is 5 feet wide and 92 inches deep and extends from one octagonal
face across to the other. Inside this volume will be placed the reactor,
the reflector, the gas handling system, the instrumentation-control mechanism,
and the graphite thermal column. The remaining volume will be filled with
slabs and blocks of concrete. Various holes, ports, and trenches are pro-
vided in the poured concrete sections to accomodate various auxiliary apparatus
of the reactor assembly.

When the reactor assembly is complete, the concrete shielding will be
so arranged that no access whatever to the interior can be accomplished ex-
cept (1) through beam-ports which are closed when not in use by combination-
lock safe doors, or (2) by removal of external slabs of concrete, which weigh
not less than 5 or 10 thousand pounds each. The concrete slabs, in addition
to their weight, are interlocked into the assembly in such fashion that
their removal is impossible unless the "cap-slab" on top of the assembly
is removed first. The "cap-slab", in turn, is securely bolted in position
and the bolts are secured against removal by locks. A completed assembly
of shielding components is shown in Figure 5.

Figure 6 shows the fuel container and its attached components. Stainless
steel (18 - 8), type 347 is used throughout the fuel system. and in all struct-
ural parts in contact with the solution or its vapors. Thickness of the
reactor walls is 1/16 inch. The fuel container is a cylinder of 27.2 cm.
diameter and 27 cm. height. (See Nuclear Fuel, below.) There are no

openings in the bottom of the cylinder or on the vertical sides. There
are 13 openings in the top surface of the reactor cylinder.

• 1. Six openings are for entrance and exit to three separate water
  cooling coils inside the reactor.
• 2. There are two 3/4" o.d., 1/16" walled, re-entrant tubes extending
  vertically from points 18" above the reactor to points inside the
  reactor, 8" below the top surface. These tubes serve respectively
  as guides or scabbards, for two control-safety rods.
• 3. One tube, 1 1/2" in diameter, projects vertically upward along
  the vertical axis of the reactor. This tube carries away the
  by-product gases from the reactor.
• 4. One 3/16" o.d., 1/32" walled tube, projects vertically downward
  7" into the reactor. A thermocouple, for solution temperature
  measurement, is carried inside the tube.
• 5. One 3/8" i.d., 1/32" walled tube, projects downward into the
  reactor, very close to the bottom. This tube is used for
  admitting and removing material to and from the reactor.
• 6. One 1/2" i.d., 1/16" walled tube, projects 20" vertically upward
  from the reactor, and carries on its top end a sylphon bellows
  arrangement for measuring height of solution in the reactor.
  (To be described below.)
• 7. One 1" i.d., 1/16" walled re-entrant tube extending 8" downward
  into the reactor and 56" upward to a point just below a removable
  plug in the concrete shielding on top of the assembly. This tube
  is used for exposure of small samples in the interior of the
  reactor where the radiation level is highest.

All re-entrant and connecting tubes are welded into the reactor. All
joints and connections in the reactor are welded. The entire assembly is
built to withstand an internal pressure of 100 p.s.i.a. without rupture

and without leaks detectable with a helium mass-spectrometer leak-detector.
The reactor must meet these specifications by actual test before initial use.
All tubes connecting to the reactor project vertically upward for 18 inches.
At this point, all except the exposure-tube, the control rod sheaths and
the level indicator, turn through 80° or 90° to an approximately horizontal
position. Beyond the bond or elbow, a leak-proof coupling is provided in each tube.

The heat generated in the reactor during operation must be removed.
The cooling system designed to accomplish this consists of three helical
coils of 1/4" stainless steel tubing of 30 feet total length inside the
reactor cylinder. At maximum anticipated power level (10 K.W.), one
gallon per minute of water from the city mains through each of the three
coils, or a total of 3 gallons/minute will dissipate the heat. Since the
coils are immersed in the corrosive uranyl sulfate solution, they must be
made of stainless steel. Water comes from the city system to the three
coils through separate automatic pressure reducing-regulating valves. A
thermocouple indicates the water temperature. The pressure regulating
controls for the valves are mounted on the Control Console. From the
three valves, the water goes directly to the three coils inside the reactor.
Thermocouples indicate and record the water temperature down stream of each
coil. The exit lines from the coils join into one line at a point about
1 foot from the reactor, and through the single 3/4" tube the water flows
downward inside the concrete shield to an underground pipe trench and along
this trench to an underground holding reservoir outside the reactor building.

A small amount of short-lived activity is built up in the water during
its passage through the reactor.

Data supplied by the City Public Utilities Department on water analysis
made over a period of years indicate that the average mineral content
of Raleigh city water is:

SiO2	9.8 p.p.m.		S04	11 p.p.m.
Fe	0.02		Cl	4.9
Ca	8.7		F	0.1
Mg	1.4		NO3	0.1
NatK	4.2		HCO3	14.0
Mn	0.0		CO3	3.9

The number of atoms per cc of water of each of these chief constituent
elements and the nuclear characteristics of the particular isotope of interest
are indicated below. The calculations are based on a 2 second exposure in a
thermal neutron flux of 1012.

Isotope	Atoms/cc of H20	Slow neutron cross section x 1024	Resultant half life activity	Resultant Activ- ity Disinte- grations/cc/sec.
F19	3.4 X 1015	0.01	12s	3.35
Si30	9.8 x 1015	0.12	2.8 hr	neg
Fe54	4.0 x 1013	2.1	4 yr	neg
Fe58	2.0 x 1012	0.32	46 d	neg
Ca44	5.8 x 1015	0.43	15 d	neg
Mg26	5.3 x 1015	4.8	10 m	625.
Na23	1.4 x 1017	0.5	14.8 h	neg
S24	1.5 x 1016	0.26	87 d	neg
Cl35	1.2 x 1017	53.0	2 x 106 y	neg
Cl37	4.1 x 1016	0.6	37 m	9.5
018	7.5 x 1019	0.00022	31 s	110

Actually, the exposure of each cc of water should be less than 2 seconds,
at normal cooling water flows of 1 gallon per minute through the 1/4" cooling
pipe, and the average thermal neutron flux will probably be less than 1012.

The induced activity is therefore probably somewhat exaggerated. Even so,
the resultant activity is less than 1000 disintegrations per second in each
cubic centimeter of water. Much of this radiation is internally absorbed
in the water.

Assuming no shielding and no internal absorption of radiation by the
water, 10 gallons of freshly irradiated water would produce a radiation
dosage at the rate of 0.08R/8hr. to a person standing 5 feet away. After
one hour, this dosage rate reduces to 0.0008R/8hr. at 5 feet.

The water therefore is sent to a holding tank where the activity is
allowed to die away before discharge into the sewers. The 1800 gallon holding
tank is large enough to hold the water form 10 hours of maximum level operation.

Radiation detectors, with indicating meters on the Control Console, are
placed at the entrance and exit of the holding tank. If any increase in
activity should occur, the cause will be determined and escape of active
material from the tank to the sewer will be prevented.

If a leak in the cooling coils inside the reactor should occur, the
water will tend to flow into the reactor solution instead of the converse,
because of the pressure in the coils. Should a leak occur, and sufficient
water enter the reactor for the liquid level to rise, an interlock on the
level indicator will operate and shut down the reactor and close the valves
in the water line to the cooling coils.

The water boiler at Los Alamos operated first with uranyl sulfate
solution and later with uranyl nitrate solution. The change was made
primarily because it was expected that periodic chemical clean-up of the
solution would be necessary, and the nitrate seemed much more amenable to
this operation than the sulfate. After extended operation it has become

apparent that necessity for clean-up processing will be an extremely rare
occurance, hence this reason for choice of nitrate is of little importance.

The nitrate perhaps does have a lesser tendency to corrode than does
the sulfate, but experiments at Los Alamos and Oak Ridge indicate that
sulfate corrosion of stainless steel is extremely small at temperatures
below 100°C.

The solubility of uranyl nitrate is loss than that of the sulfate. Once
dissolved however there appears no difficulty in preventing precipitation of
either the nitrate or the sulfate, provided the solution is kept sufficiently
acid.

There are three chief advantages in using the sulfate solution: (1) the
boiling point is somewhat higher for the sulfate solution than for
the nitrate solution, (2) the radiation decomposition into gaseous
products is much lower, is about half in fact, that of the nitrate, and
(3) the neutron absorption is less in the sulfate than that in the nitrate.

It is intended, therefore, that the reactor described herein will operate
with a solution of uranyl sulfate as the nuclear fuel. Uranium highly en-
riched in U235 will be used. The amount of uranium needed and the dimensions
of the cylindrical reactor are determined approximately by comparison with the
amount and dimensions in the spherical Los Alamos Reactor, with appropriate
conversion factors. A detailed, accurate evaluation of amounts and dimensions
will be made later from considerations of reactor theory and nuclear constants
when exact arrangements of reactor, reflector, etc. have been decided.

The Los Alamos Reactor contains 12,600 cc of uranyl nitrate in which
839 grams of U235 are dissolved. 764 grams are needed to produce criticality
at 20°C, and the extra 75 grams are needed to overcome the negative temperature
coefficients and provide a useful excess reactivity. A cylindrical reactor,
because of its larger surface:volume ratio, requires 1.14 times as much

material as a spherical reactor, other conditions being equal. On this basis,
the cylindrical reactor solution should have a volume of 12,600 x 1.14 =
14,360 cc. Using optimum height to radius dimensions for a cylinder of
H/R 1.848, gives height 24.8 cm, and diameter = 27.2 cm. A cylinder of
27.2 cm diameter and 27.0 height would permit 2.2 cm depth of unoccupied
volume in the top of the cylinder. This depth becomes 2.9 cm when the sulfate
Solution and the difference in cooling coils is taken into consideration.

About 840 grams of U235 in the cylindrical reactor are required to
produce criticality at 20°C, and about 60 grams more, or 900 grams, at 80°C.
The negative temperature coefficient is such that the critical mass increases
about 0.9 grams per degree centigrade. Fifteen additional grams are added
to insure sufficient excess reactivity for useful experimentation. The total
U235 required, therefore, will be about 915 grams.

The stainless steel reactor itself is surrounded by a second envelope
made chiefly of aluminum (Figure 7). The 27.5 cm O.D, (diameter) cylindrical
reactor is enclosed in a 28.3 cm I.D. cylinder which is closed at the
bottom, underneath the reactor, and which extends upward 16" to a flanged
connection in the lower surface of a much larger aluminum cylinder. The
lower part of the smaller cylinder is made of stainless steel, so that it will
not be chemically attacked immediately in case a leak should occur. The
reactor itself rests on and is supported by the lower end of the Reactor
Envelope. The larger upper cylinder, 48" in diameter and 42" high, flange-
closed at top and bottom, together with the connecting smaller cylinder
fitted around the reactor, constitute the Reactor Envelope.

The purposes of the Reactor Envelope are (1) to catch any liquid which
should inadvertently leak from the reactor; (2) to retain for leisurely

disposal any radioactive gases which inadvertently escape from the reactor;
and (3) to serve as a safety volume into which the reactor contents could
expand without wide liquid or gas dispersal in case of rupture of the
reactor system. This envelope-chamber is not absolutely vacuum-tight and
does contain several imperfectly fitted joints through which gases under
pressure inside the volume could slowly escape. The envelope, however,
would reduce any leak to a very low rate so that the ventilation system
could dispose of the escaping gases without permitting the room to become
contaminated. The gases inside the envelope can be pumped out slowly through
purge lines to absorption traps or pumped directly to the stack for disposal.

The volume of the envelope (exclusive of the space occupied by motors,
etc.,) is about 40 cubic feet, or about 45 times the total volume of the
reactor itself, hence any pressure inside the unfilled volume of the reactor
should be tremendously reduced if it should expand into the envelope volume.
The reflector around the reactor will be so arranged that the line of least
resistance for a pressure release around the reactor. will be upward into the
large volume of the envelope. That is, the 16" of graphite on top of the
reactor, inside the reactor envelope is loosely packed powder which would be
pushed aside by a pressure release below.

An atmosphere of inert gas under slight positive pressure will
normally be maintained in the envelope. Periodic sampling will quickly
reveal the pressure of any gases leaking from the reactor. The positive
pressure will retard the escape of gases from the reactor through any leak
which should occur.

The water lines to the cooling coils, the refueling sampling line
to the reactor, the gas disposal tube, etc. from the reactor penetrate
the wall of the reactor envelope through screwed-in, spring-tightened gas

seals. These seals are not vacuum-tight, but will only permit the escape of
negligible amounts of gas unless the pressure inside becomes extremely
large. These tubes are all arranged with union couplings in the lower
4" of the large cylinder of the reactor envelope. If these unions are
uncoupled, and the lower flange seal of the large cylinder is broken (by
removal of screws), the upper part of the reactor envelope, with the un-
connected tubes and pipes, can be removed. This would only be necessary
under certain emergency conditions, described later.

The reactor is not concentrically placed inside the slightly larger
cylinder of its enclosing envelope. The reactor touches one side of its
envelope, which leaves a gap of about 0.8 cm on the opposite side between
the reactor and the envelope. In this space are located (1) a thin strip of
cadmium which moves vertically in a guiding scabbard and serves as a shim-
control rod, and (2) a small tube extending downward to the bottom of the
reactor envelope, to the lower surface of the reactor, which provides a means
of removing liquid from the envelope in case a leak in the reactor develops.
The remaining space is filled with tightly packed graphite powder.

The reactor envelope, immediately underneath the reactor, rests upon a
16" thickness of graphite blocks, and is also surrounded on the sides con-
tiguous to the reactor by 16" of graphite blocks.

The reflector is placed around the reactor (a) to decrease the amount of
U235 needed in the reactor and (b) to increase the value of the radiation
flux at the surface of the reactor. Highly purified graphite, shaped from
4" x 4" rectangular bars to fit snugly against the reactor surface is used as
the reflector. The graphite is placed both inside and outside the reactor
envelope, so that a thickness of at least 16" is present on all surfaces of
the reactor.

Inside the reflector envelope, above the reactor and in the narrow
channel around the sides, powdered graphite to a depth of 16" serves as part
of the reflector. This powder is packed sufficiently to prevent any
effective shifting of the reflector during reactor operation.

If a leak should occur in the reactor, the liquid will be caught in the
bottom of the reactor envelope. Any liquid in the reactor envelope would be
in close contact with the reactor, and part of the same nuclear fuel
accumulation. The control and safety rods of the reactor, therefore, would
serve to prevent inadvertent nuclear reaction because of accumulation of
the leaked liquid.

In case a leak or rupture should occur in turn in the reactor envelope,
a second catch basin for liquid is placed underneath the first. The secondary
catch basin has an upper and a lower part. The upper part is an aluminum
cylinder, open at the top, into which the lower end of the reactor envelope
loosely fits. The cylinder is filled to within 2" of its upper end with
snugly packed graphite blocks. The reactor envelope rests solidly on this
graphite for support. Small channels through the graphite permit any liquid
leaking from the reactor envelope to trickle down through the graphite to
the lower part of the catch basin. Calculations show that a nuclear chain
reacting condition in the graphite below the reactor will not be closely
approached, even if all the solution from the reactor is thoroughly and
uniformly inpregnated throughout the graphite, which is not likely to occur.

The lower part of the catch basin consists of a broad shallow chamber
in which the liquid from above may be caught. There are no control rods in
this vicinity, hence the unfavorable geometry of the flat catch basin is
necessary in order to prevent uncontrolled nuclear reactions in case all of
the nuclear fuel should leak down to this location.

An aluminum cylinder, 52 inches (O.D.) in diameter and 48" high, open
at the top, but lined on the sides and bottom with 2 inches of lead, encloses
the reactor. Holes are cut in the sides for the passage of exposure parts
to the reactor. An additional layer of lead, unattached to the cylinder,
is placed externally around the sides of the cylinder. The purpose of this
heavy metal layer is two-fold: (1) The metal acts as an attenuator for the
gamma radiation from the reactor, thus reducing the amount of concrete shield-
ing needed; and (2) in case the reactor must be removed from the assembly
while it is highly radioactive from undecayed fission products, it may be
removed inside the metal lead-lined cylinder, which then serves as a
shielding container for the transportation or storage of the reactor. The
"port holes" may be easily filled and a cover may be placed on the top to
provide a complete shield after the upper part of the reactor envelope is
removed.

The cylinder serves incidentally as a tertiary catch basin for leaked
solution, in case the first and second catch basins fail.

The reactor is provided with two identical boron rods and one cadmium
"rod". One of the boron rods serves as a safety rod and the other as a
control rod. The cadmium "rod", a 0.02" thick, 2" wide strip of cadmium
mounted flat against the outside vertical wall of the reactor, serves as a
shim control rod. The boron rods each consist of 8" of enriched (B10)
sintered boron ([rho] = 1.5 - 1.7) inside of a 5/8 o.d. thin walled stainless
steel tube. The boron tubes are mounted vertically inside of stainless steel
scabbards which are re-entrant through the top surface of the reactor, 8" down
into the reactor. The boron rods are located 4" from the central vertical
axis of the reactor and approximately 100 radial degrees from each other.

In these positions the boron rods are each "worth" about 80 grams of
U235 in the solution. Thus either rod alone is equal to the total excess
U235 in the solution above that required for criticality at room temperature.
The shim rod is "worth" about 10 or 12 grams.

The stainless steel tubes containing the boron in their lower ends
extend upward inside the (re-entrant) scabbard tubes about 18" to an
electromagnet connection to vertical, motor driven "rack and pinion" rods.
The "rack and pinion" rods may be raised or lowered by signals to their
respective motors from the Control Console. The boron rods, likewise,
through the electromagnet connection, are raised and lowered with the "rack
and pinion" rods. Should current to the electromagnet be interrupted the
connection is broken and the boron rod drops 8" into the reactor inside the
re-entrant scabbard tube. The shim rod is likewise raised and lowered by
motor drive.

In normal operation, one boron rod (safety) is hoisted completely out of
the reactor to a poised position from which it can drop back into the reactor.
The shim rod is partially removed, and in that position oscillates up and down
in response to electronically amplified signals which attempt to move the
shim rod to counteract fluctuations in the operating level of the reactor.
The other boron rod (control) is partially withdrawn to such level as will
cause the reactor to operate at the desired level.

The instrumentation included in the reactor installation is intended:
(1) to provide the operators with knowledge of all relevant conditions and
processes occurring in the assembly and to record such information when
desirable; (2) to furnish the operators with means of guiding, controlling,
and regulating all processes.

The chief components of the instrumentation system are: (1) the sensi-
tive devices: thermocouples, pressure guages, radiation
detectors, etc., in and around the reactor assembly; (2) the signal transmitting system: cables,
pressure leads, etc.; (3) the indicating and recording mechanisms at the
operator's location; and (4) the controlling, regulating devices at the
operator's location.

A control console will be located outside the reactor room in such a
position that an operator at the console can view the inside of the reactor
room through a large water window, 16 inches thick, (as protection from stray
radiation). On the console will be located the indicating, recording, and con-
trol-regulating mechanisms. Trenches under removable sections of the floor,
loading from underneath the reactor to a point underneath the console, will
provide the location of the signal transmitting devices.

The measurement and control of the operating level of the reactor is by
far the most important component of the instrumentation system. Temperatures,
pressures, water flow, gas disposal, monitoring data, etc., are also of vital
importance. The vaious important components of the instrumentation system
are described below:

A. Control
• • (1) Detectors
  • A total of six fission chambers are to be used in measuring and
    controlling the activity of the reactor. These are to be placed
    within the concrete shielding just outside the lead shield, and are
    to be placed symetrically around the reactor core so that any one
    chamber can be used to perform any of the control or measuring
    functions. These chambers are to supply the signals to the
    amplifiers and associated equipment, which normally perform the
    following functions:

• • • Chamber No. 1--indicating and recording neutron flux level
      on linear scale.
    • Chamber No. 2--indicating and recording neutron flux level
      on three decade logarithmic scale.
    • Chamber No. 3--reactor period recording and indication.
    • Chamber No. 4--neutron flux level for automatic rod control.
    • Chamber No. 5--reactor period for automatic rod control.
    • Chamber No. 6--neutron flux level and period for safety trip.
      The circuits of chambers 1 and 4 will also be
      used for tripping the safety releases at preset
      neutron flux levels.

  • Additional channels with proper amplification and metering will be
    supplied for inclusion of scintillation detectors to supplement the
    fission chambers.

    The activity of the coolant is to be monitored continuously
    by means of a scintillation counter which measures the activity of
    the coolant as it enters the hold-up tank. A similar detector is to
    be placed at the exit of the hold-up tank.

    The activity of the stack gases will also be monitored by
    detectors having indicating meters and recorders on the control
    console.

• • (2) Amplifiers and Recorders

  • The associated equipment of the fission chambers will be made
    up of stabilized low-drift D C amplifiers used in conjunction with
    necessary networks to produce the linear logarithmic and period
    functions

    In addition to the above mentioned recorded information, the
    following data will also be recorded automatically:

  • • (a) Position of the control rod and the shim rod.
    • (b) The coolant temperature at inlet and outlet of reactor.

• • • (c) The coolant rate of flow.
    • (d) Radiation level in the coolant before and after the hold-up
      tank.
    • (e) The temperature of the reactor solution.
• 
  
  • (3) Control Process.
  
  
  • The control mechanism consists of a safety rod, which in normal
    operation is completely removed from the reactor; a control rod and
    a shim rod, which can be positioned automatically or manually.
    Separate positioning controls will be available for each rod.
  • (a) Safety rod. The safety rod consists of a lower boron filled
    section, a connecting part and an upper gear drive section. The
    lower portion of the rod is held to the connecting rod by means of
    an A C operated holding coil which may be deenergized by various
    signals to be described later. The position of the rod is indicated
    on the control console. Limit switches, upper and lower, operate
    indicating lights on the panel. The rod is driven up or down by
    means of a two phase motor; the speed and direction of the the motor
    drive may be controlled from the panel. The gear reduction from the
    motor to the rod is such that a predetermined maximum rate of with-
    drawal cannot be exceeded.
  • (b) The control rod is of the same construction as the safety rod.
    The drive mechanism in the manually operated function is the same ex-
    cept for the fact that the gear reduction system has very low backlash
    and the position can be read more accurately. For automatic operation,
    servo units controls the position of the control rod and the shim rod
    so as to maintain the neutron flux at a desired level. The shim rod
    is used to compensate for small fluctuations in the neutron level.

• • (c) The operator has before him at all times a three-decade presen-
    tation of the neutron flux variations as well as an expanded picture
    of the power level at the operating point. The rate of increase
    or decrease of the neutron flux is also metered at the operator's
    position. A galvanometer type of meter will show the operator
    at any time during automatic operation the difference between the
    desired flux level and the actual level. This meter will serve in
    similar capacity during manual operation as well.
  • (d) Besides the above mentioned meters, operation of the holding
    magnets will be monitored so that the operator will know when the
    magnet current is on, and when each of the two rods has been picked
    up by its magnet. Limit switches on the upper and lower travel of
    the rods operate indicator lights on the control panel. This is a
    safety factor as well as a means of checking the position of the
    rods against the selsyn indicating system.
  
  
  • (4) Interlocks.
  
  

  • A system of interlocks is provided to assure proper sequence of
    operation of the reactor.

    The power going to the rod holding magnets is interlocked with
    reactor shield doors, water flow, amplifier rack doors and recorder
    chart motor drive as well as the main power supply to all instruments.

  
  
  • (5) Automatic Safety Mechanism.
  
  
  • The automatic safety mechanism can be divided into two classes:
    1.) safety devices which indicate faulty equipment or sequence of
    operation, and 2.) devices which deenergize the holding magnets and
    give indication when some level or rate has deviated from its normal

• • course. In the first class are the above mentioned interlocks, and
    the following items. In the cases where the signals from the fission
    chambers are amplified as a linear function, their outputs will be
    compared so that indication can be made when one deviates from the
    mean. If desired, this differential can be used to trip the holding
    magnet. Where possible, failure of other primary equipment will be
    indicated on the control console. In the second class of automatic
    safety mechanism are the following functions which can operate to
    trip the mechanism of the holding magnets:
  • • (a) An excessive neutron flux level in the reactor.
    • (b) An excessive rate of rise of the neutron flux in the reactor.
    • (c) A failure of water flow.
    • (d) An excessive coolant temperature differential.
    • (e) Accidental opening of any of the interlocks.
    • (f) Failure in the main power supply.
    • (g) Travel of the control rod to its top limit.
    • (h) An excessive radiation in the coolant.
    • (i) Manual trip from the control panel.
• B. Control Console.
  • The control console consists of three divisions: (1) the central
    primary indicating and control panel, (2) the secondary indicating panels,
    and (3) the recording panels.
  • • (1) The central panel will contain the following instruments:
    • • (a) Indication of the neutron flux level on a three-decade scale.
      • (b) Indication of the neutron flux level on a linear multi-range
        meter.
      • (c) Indication of the rate of change of the neutron flux level.

• • • • (d) Safety rod position control.
      • (e) Safety rod position indicator.
      • (f) Control rod position control.
      • (g) Control rod position indicator.
      • (h) Shim rod mean position control and indicator.
      • (i) Neutron flux level desired.
      • (j) Difference between neutron flux desired and actual level
        indicator.
      • (k) Maximum rate of change of neutron flux desired.
  • • (2) The secondary panel will include the following indicators:
    • • (a) The holding magnet current control and indicator.
      • (b) Interlock indicating lights.
      • (c) Instrument failure indicating lights and differential control.
      • (d) Holding magnet trip indicator lights.
      • (c) Indicating instruments to duplicate the recorded functions.
      • (f) Recorder chart speed change control.
      • (g) All power supply switches and indicator lights.
      • (h) Room monitor level indicator.
      • (i) Reactor solution temperature.
      • (j) Stack monitoring indicator.
      • (k) Coolant flow regulation.
  • • (3) The recording panel will contain the following recorders:
    • • (a) Neutron flux level on a three-decade range scale.
      • (b) Neutron flux level on a linear multi-range scale.
      • (c) Neutron flux power period (or rate of change of flux).
      • (d) Control rod position.
      • (e) Shim red position.
      • (f) Coolant temperature.

• • • • (g) Coolant flow.
      • (h) Coolant radiation.
      • (i) Reactor solution temperature.

All component parts of the reactor involved in determining the power
level of operation (shielding, cooling coils) have been designed to permit
steady state operation at 10 Kilowatts. It is probably that, in actual
operation, power levels in excess of 5 KW may not be desired for a long
time. Indeed, a great deal of work will be performed at 1 KW or less.

Table 1 lists the estimated and calculated radiation fluxes at various
points in and about the reactor at 10 KW power output.

TABLE 1. VARIOUS FLUX DENSITIES AT VARIOUS POSITIONS (10KW)

1. Surface of Reactor Vessel.

From experimental work on a reactor similar to the one described in this
report estimates of radiation fluxes on the surface of the reactor are:

Gamma rays	5.4 x 1011	[gamma]'s/cm²sec.	2Mev.
Neutrons fast	1 x 1011	n/cm²sec.
Neutrons slow	3 x 1011	n/cm²sec.

2. Re-entrant exposure tube inside the reactor.

Based on the neutron distribution in the cylindrical reactor the above
figures would require the following values at the center of the cylinder
which we will consider as the values in the re-entrant exposure tube.

Gamma rays	5.4 x 1011	[gamma]'s/cm²sec.	2Mev.
Neutrons fast	5.5 x 1011	n/cm²sec.
Neutrons slow	1.5 x 1011	n/cm²sec.

3. Experimental Port.

At the external end of port the flux can be estimated by assuming only in-
verse square law acting. This will be approximately true even for [gamma] rays.
On this basis, the calculated values are:

Gamma rays	2.0 x 109	[gamma]'s/cm²sec.	2Mev.
Neutrons fast	2.0 x 108	n/cm²sec.
Neutrons slow	1.2 x 109	n/cm²sec.

4. Thermal Column.

At external surface of column (5 ft from reactor) the slow neutron flux will
be 3 x 107 n/cm²sec. with about 5.2 x 10² fast neutrons, (i.e., 60,000:1).
There will be [gamma] rays which will come from the absorption of slow
neutrons when Cd sheet is in place to absorb slow neutrons.

Gamma rays	from Cd(n,[gamma])	when Cd in place
Neutrons slow	3 x 107	n/cm²sec.
Neutrons fast	5 x 10²	n/cm²sec.

5. Along Thermal Column.

Tabulated below are the neutron flux available at points along column:

Distance from Lead Shield	1 foot	2 feet	3 feet
n(slow)	5 x 1010 n/cm²sec.	1.2 x 1010 n/cm²sec.	3.5 x 108
n(fast)	4 x 106 n/cm²sec.	5 x 105 n/cm²sec.	1 x 104

As the reactor is operated, the fuel solution and surrounding materials
become radioactive. The total radiation from the reactor derives from three
sources: (1) fission of uranium, which instantaneously releases neutrons and
gammas, with relatively fewer alpha and beta particles; (2) fission products,
which are highly radioactive when first formed, and they release a few
"delayed" neutrons and many beta and gamma particles; and (3) radioactive

materials artificially (activated by the radiation from (1) and (2). This
induced activity consists chiefly of betas and gammas. When the reactor is
not in chain reacting condition, radiation is not produced by (1) fission,
but does continue from (2) and (3): fission products and induced activities.
Both these latter materials decay in activity with half lives characteristic
of the particular isotopes involved. The composite total of the half lives
involved results in a characteristic decay pattern for the reactor contents.
The "composite" half life has been found to be about 55 seconds.

When the reactor is brought to a chain reacting condition at a certain
fissioning rate, after a period of inactivity during which the previousl
induced activity decayed to a low level, radiation from the fissioning atoms
is immediately produced and fission products begin to accumulate. Induced
activity in the surrounding materials also begins to build up. assuming that
the fissions continue at a constant rate, the total radiation steadily in-
creases due to the contribution of the fission products and the induced
activities. The increase continues until the decay of the non-fission
sources is equal to the rate of formation. This will require a very long
time, for a small fraction of the fission products are very long-lived.
Thus, a "steady state" condition involves a small but gradual rise in total
radiation from the reactor, even though the fission rate remains constant.

Table 2 below contains calculated values of the total activity of the
fuel solution at various elapsed periods after shut down from various
operating levels. It is assumed that the gaseous fission products escape
from the reactor as they are formed.

TABLE 2. ACTIVITY IN CURIES OF FUEL SOLUTION

Operation Time (days)	Power	Time in Days After Shut Down
		0.001	0.1	1	5	15	20
1	10KW	2.1x104	4.3x10³	3.1x10²	1.8x10²	0.52x10²	0.38x10²
10	10	2.4x104	6.7x10³	2.6x10³	1.0x10³	4.0x10²	3.0x10²
100	10	1.8x105	1.0x104	4.3x10³	2.3x10³	1.4x10³	1.2x10³
1	1	2.1x10³	4.3x10²	0.31x10²	0.18x10²	5.2	3.8
10	1	1.8x104	1.0x10³	4.3x10²	2.3x10²	1.4x10²	1.2x10²

A large portion of the neutrons emerging from the surface of the reactor
are "fast" neutrons, i.e., their energies and velocities are high. A great
deal of interesting research, however, involves the use of "thermal," or slow
neutrons. Fast neutrons may be slowed by collision with light, low neutron-
absorbing atoms, of which carbon is an excellent example.

The neutrons from one side of the reactor, therefore, are allowed to
penetrate several feet of graphite, highly purified to remove neutron absorbing
contaminants and, as they emerge, a large percentage have velocities in the
thermal region.

The thermal column of graphite is shown in cross-section in Figure 8.
Four exposure ports into the graphite are provided. Table 1 lists the
anticipated values of the radiation flux at various positions in the graphite

It is anticipated that several sample ports may be used simultaneously
for exposure of samples to the radiation from the reactor. Also, it may be
desirable to "tie-up" permanently the bean from one or more ports with a

large piece of special apparatus. Hence provision is made for a large number
of exposure-bean ports through the shielding into the region of the reactor,
though only one or a few of these may be in use at any given time.

There are altogether 12 exposure ports. (Figure 9 )

Seven extend horizontally from the outside surface of the concrete shield
inward to the surface of the reactor envelope, along extended diameters,
respectively, of the reactor, of these seven, one runs along the horizontal
axis of the thermal column.

Four exposure ports extend entirely through the assembly, from the out-
side surface on one side through the interior of the assembly, to the outside
of the shield on an opposite side. Three of those four traverse the thermal
column, perpendicularly to the horizontal asix of the column. The fourth
is tangent to the surface of the reactor envelope.

The twelfth exposure port extends vertically downward through the top
surface of the concrete shield to the top surface of the reactor itself as a
one inch tube, which continues downward into the reactor as a re-entrant tube
to a depth of 8". Small samples in this tube are exposed to the highest
possible radiation flux.

In order to achieve economy and convenience in construction, all exposure
ports are standardized to a single pattern (except the 1" vertical port).

A 3.5" i.d. metal tube in the concrete is placed in position and permanently
secured there by surrounding it with the poured concrete of the reactor
shielding. Subsequently, the 3" i.d. "lining tube" is inserted into the
first tube so that it provides a continuous passage from the outside of the
shielding to the surface of the reactor envelope. The "lining tube" can be
removed should it interfere with repair work around the reactor inside the
concrete shield.

The external end of each exposure port terminates in a heavy "burglar-
proof", combination-locked safe door. When not in use, the beam ports are
plugged by inserting successively smaller telescoping tubes inside the "lining
tube" until the passage is closed. The safe door is then closed and locked.

All exposure-ports emerge horizontally from the shielding at a level of
24" above floor level. The emergent beams thus would strike a person who
carelessly stepped into the beam path on the legs, rather than in a more
vital region. Radiation beams from the ports traverse paths across the
Reactor Room 24" from the floor level, to respective openings in the building
wall which lead to underground radiation traps outside the building.

To permit usage of lager apparatus than could be accomodated at the
24" level from the floor, trenches four feet wide and two feet deep, ex-
tending from the respective faces of the reactor to the wall of the room,
are provided. These trenches are normally covered when not in use by
movable sections of the floor of the room.

For the purpose of adding solution to the reactor or withdrawing
solution (samples, or complete removal) a Sampling Line is included in the
reactor design. (Figure 7). A 3/8" stainless steel tube, re-entrant into
the reactor, extends from. the inside bottom of the reactor upward through a
coupling in the wall of the reactor envelope, then at a slight incline from
the horizontal, through a submerged trench in the concrete, to terminate at
a cutoff valve just underneath a combination-lock safe-door in the top
surface of the concrete shield.

By unlocking and opening the safe door, the end of the sampling tube is
exposed. Addition of fluid can be readily accomplished by gravity flow into
the reactor. Also, by simple connection to a vacuum pump, preceded by a
liquid trap, solution may be quickly removed from the reactor.

A second tube, the Liquid Salvage Line, lies closely beside the first,
but extends to the bottom of the reactor inside the reactor envelope enclosing
the reactor. With this tube, liquid can be removed from the reactor envelope
in case of leaks, etc.

For measuring the level of liquid in the reactor two methods amy be used:
(1) The pressure required to bubble air (or other gas) backwards through the
sampling lines to the bottom of the reactor can be measured and, knowing the
specific gravity of the liquid, the solution level can be calculated. (2) A
liquid level indicator is provided for accurate level measurement when the
reactor is nearly full. The latter instrument is described below.

A welder or stainless steel tube of 3/8" inside diameter projects 24"
above the top surface of the reactor (Figure 10). At this point the 3/8" tube
is flange sealed with an insulator gasket to a 2" x 3" stainless steel sylphon
bellows. From the movable top end of the sylphon bellows a 1/8" steel rod
projects 25 inches downward to make contact, on its sharpened point, with
the liquid in the reactor. The sylphon and its attached contactor, being in-
sulated by the gasket from metal contact with the reactor, may be made the
anode of a low voltage electrical circuit of which the reactor and its electro-
lyte liquid is the grounded portion. The sylphon bellows may be compressed
by means of pneumatic pressure inside a sealed-on metal chamber enclosing the
sylphon. When pressure is exerted, the sylphon is compressed and the pointer
lowers to make contact with the liquid. When this occurs, an electrical
signal appears on the operators control console. The position of the pointed
is calibrated against the pneumatic pressure. The distance of vertical travel
is three inches. When the liquid is within 3 inches of the top surface of the
reactor, therefore, its position may be determined with high accuracy.

When the reactor is in operation, a very small volume of gaseous fission
products will be released. These gases result from the fission of uranium
into elements of gaseous nature near the middle of the periodic table. Most
of the gases will be highly radioactive, but most of the radioactivity will
be quite short lived.

Estimates have been made of the gaseous fission products expected
from the reactor, calculations of the total radioactivity expected, and
of the decay of the radioactivity Figure 11).^b1 About 2.5 x 1014 disinte-
grations per second, or 7000 curries, occur initially from the atoms of the
fission product gases produced per kilowatt minute. After 4 hours, however,
the activity is 5.0 x 109 disintegrations per second, or 0.15 curios from a
kilowatt minute of fission product gas, a decrease in activity by a factor
of over 50,000 in 4 hours.

The fission product gases will be accompanied by much larger volumes of
other gases resulting from the radiation decomposition of the water molecules
in the fuel solution into hydrogen and oxygen. The hydrogen and oxygen will
have negligible radioactivity, but these gases do constitute a mixture of
explosive proportions.

The "gas problem" for the reactor in maximum normal operation (5 KW)
consists therefore in disposal of 40 liters per hour of a hydrogen-oxygen
mixture in which a trace of highly radioactive fission products gases are
intermixed. There are several possible means of disposing of these gases:

• (a) The gases can be swept out of the reactor as they are formed with,
  say, flushing air, conducted via ducts and blowers to a stack and thereby

• dispersed into the atmosphere. This is the method used at Los Alamos,
  quite satisfactorily.

  The flushing air dilutes the H2-O2 mixture to non-explosive pro-
  portions; the large blowers at the stack (8-10,000cfm) dilute the small
  amount of active gases to extremely samll parts of the volume blown
  into the upper atmosphere, and the release occurs adequately high (100
  feet or so) to prevent ground contamination. This method, however, is
  not satisfactory as a routine disposal method in a thickly inhabited
  are, for several obvious reasons.

• (b) The gases, undiluted, can pass to an underground holding tank large
  enough to require, say, 10 days for the gases to traverse, and then be
  dispersed via P stack to the atmosphere. The holding tank required would
  need only a 3500 liter capacity, and the gases, at dispersal, would be
  very low in activity. The only difficulty with this method is, the
  gases are potentially explosive, and storage of 3500 liters of an ex-
  plosive gas in an underground tank is not a desirable procedure. If the
  mixture is first diluted with inert gases to prevent explosions, the
  total volume would become at least 6 times as great, or 21,000 liters
  for the holding tank. This is not an impossibility, of course. For
  smaller volume of gas, this method would constitute a very desirable
  means of disposal.

• (c) The gases can be diluted with an inert gas to prevent explosion,
  say, nitrogen or helium, and then the H2 and 02 can be combined, by
  ignition or catalytically. The resulting water can then be condensed
  and removed, and the diluent gas, with its slowly but gradually in
  creasing increment of fission product gas contamination, can be
  recirculated.

  This is not a desirable process, chiefly because the condensing, re-
  circulating equipment, etc. would be rather complex.

• (d) The gases can be diluted with steam to prevent explosion (at least
  3:1 steam; H2-O2 mixture) and then ignited or catalytically combined to
  form water vapor. The diluent steam and the recombined water vapor is
  then condensed and the water sent to a holding tank for eventual disposal.
  The small fraction of uncondensed, non-explosive gases are then sent to
  a holding tank for radioactive decay and eventual disposal via stack to
  the atmosphere. Alternately, after removal of the explosive components,
  the small fraction of remaining gases may be absorbed in activated
  carbon traps and absorbed there until radioactive decay is sufficient.
  Then the gases may be released by heating the carbon, and dispersed into
  the atmosphere.
• (e) It may prove feasible simply to absorb all gases evolved, radio-
  active and otherwise, on activated carbon, hold for radioactive decay,
  and then release to the atmosphere by heat.
• (f) Another very promision method of handling these gases is now under
  investigation. This consists of preferential removal of hydrogen from
  the mixture, and storage of the non-explosive residue until sufficiently
  decayed to permit atmospheric dispersal. The hydrogen can be removed
  by passage of the gas mixture through a vacuum jacketed tube having
  porous walls, the pores being of sufficient size to permit passage
  of hydrogen but not large enough to permit passage of the ether gases.
  This can be accomplished by a thin, heated polladium tube, (which is also
  highly corrosion resistant), though the area needed for complete hydrogen
  removal is rather large. Certain other porous materials are now being
  investigated.

It is quite certain that some method or combination of methods can
be devised to provide a completely satisfactory system of handling the
gases. No dispersal to the atmosphere will be permitted until the
activity is decayed sufficiently to be harmless.

If the system were to be built at the time of the present writing,
the combination of methods described below would be used. It may be
possible to improve the system considerably before the reactor is built
as a result of studies now in progress.

As now visualized, the reactor gases would be handled by one of two
methods (See Figure 12): 1) For product gas volumes below 500cc/min,
which would be the case for a major portion of the "in" time, the gas
would be diluted with 6 times as much air, to produce a non-explosive
mixture, and sent to a 3000 gallon underground holding tank for
radioactive decay. Ten days would be required for traversal of the
baffled interior of the holding tank, during which time the activity
would decay by a factor of 5 x 105 (Section 5 ). The gas emerging
from the holding tank (500cc/min, maximum) would be diluted with
10,000 cfm of air and blown up the building stack. With uniform mixing,
the gases emerging from the stack would have an activity of 2.5 x 10-4
microcuries.

2) For product gas volumes from 500cc/min to 2000cc/min (maximum
for 10KW operation), steam at 100°C is used for dilution, 4:1. The
resulting non-explosive mixture is passed through a stainless steel
wool-packed preheater, where a hydrogen-oxygen combining reaction is
initiated. The reacting gases are swept into a "converter" chamber
where the exothermic H-O reaction is controlled by cooling coils. The
total water vapor, both from the recombined H-O and the dilution steam,
is condensed and sent to a holding tank where the short-lived activity
decays. The small volume of non-condensed gases are then sent (a) to
the 3000 gallon holding tank for radioactive decay before atmospheric
dispersal, or (b) to a cooled activated carbon absorption trap where they
are absorbed until radioactive decay is adequate for atmospheric dispersal.

If at any time an unsafe quantity of radioactivity is found in the
gases being dispersed into the atmosphere, the reactor will be closed
down until the situation is rectified. If an inadvertent power flash
in the reactor should occur (a sustained high power is impossible) and
create suddenly a volume of product gases, these would be diluted with
air and swept to the holding tank where they would be held as necessary
for radioactive decay.

In the routine operation of the reactor and its associated facilities,
certain hazards to personnel will exist. The situation is quite analogous to
that existing in an x-ray laboratory or in a chemicals manufacturing plant where
toxic gases, say, fluorine, is handled. In those and all similar situations,
safety or personnel is insured by (1) proper design of equipment, (2) adequate
monitors and safety devices and (3) continuous education and emphasis on safe
practices. The normal hazards of operating this establishment are listed below,
together with the means of insuring safety of personnel.

Radiation may come from two sources: (1) open ports in the reactor
shielding from which a direct beam may emerge. Anyone entering the path
of such a beam would receive a dose of radiation of greater or lees magnitude,
depending on many factors. The beam of maximum possible intensity as it
emerged from a 3" hole at the surface of the shielding would contain

• 6 x 1010 2mev [gamma]s
• 6 x 109 fast ns
• 3.5 x 1010 slow ns.

This beam would cause a radiation exposure over a 3" circular area of
approximately 2.0x10³R/second. At the wall of the reactor room, due to
attenuation and "inverse square" spreading of the bear, the radiation ex-
posure would be about 1.3x10²R/second over a 12" circular area. If the beam

CONFIDENTIAL

strikes an object in its pathway, considerable amount of scattered
radiation over the reactor room may result. (2) Radioactive sources, e.g.
irradiated samples, etc., could cause irradiation of persons in the vicinity.

The following means, among others, will be followed as precautions
against excessive radiation exposure:

• (a) All beans from the reactor emerge horizontally at a height of
  24 inches from the floor so that exposure, if any, will normally occur
  on the legs instead of in some more vital region.
• (b) Exit holes in the wall of the buildings leading to underground
  radiation traps will be provided opposite each beam port in the reactor.
  Thus, the emergent beams will not be scattered inside the reactor room.
• (c) Occupancy of the reactor room when the reactor is in operation will
  be kept to a minimum.
• (d) The reactor room is provided with 12" - 16" masonery wall, except
  at one place, to prevent scattered radiation reaching personnel in other
  parts of the building. On one side a large water observation window,
  16" thick, permits external observation and simultaneously prevents
  exposure by stray radiation. Openings from the reactor room are pro-
  tected by "Chinese screens" to prevent escape of stray radiation.
• (e) A bank of tubes of assorted sizes project outward and downward
  a height of 4 - 6 feet on one wall of the reactor room (hence
  they are underground externally) in which all radioactive sources and
  irradiated samples are stored when not in use. Thus, persons in the
  area are not exposed to radiation from these stored materials.
• (f) Radiation monitors, equipped with visible and audible warning signals,
  will be placed in strategic positions in the building to provide warning
  when radiation tolerance limits are being approached.

• (g) All personnel in the building will be required to wear personnel
  electroscope monitors, film badges, and other radiation recording
  devices as necessary, to provide knowledge of routine exposure history.
• (h) Constant vigilance and emphasis on safety will be practiced and
  demanded of all persons engaged in activities in the vicinity.

In pre- and post-exposure handling of samples and specimens, considerable
manipulation of radioactive materials, largely beta and emitters, will be
involved. Handling, chemical processing, measuring, weighing -- all these
and similar operations may involve hazards of exposure, ingestion and personal
contamination. Various precautions will be followed to insure the safety of
personnel.

• (a) No person will be permitted to engage in radiophysical and radio-
  chemical activities who has not satisfactorily demonstrated adequate
  training in this type of work.
• (b) The very best type of radiochemical equipment and facilities will
  be provided. Ventilation will provide motion of air from areas of low
  activity toward those of higher activity. In hoods and on chemical
  benches ventilators will move air away from the operator. Adequate
  tools, tongs, shielding brick, radiation monitors, etc. will be provided
  in the laboratories.
• (c) No smoking or eating in radioactive areas will be permitted.
• (d) Lockers, showers, clothing change rooms, scrubbing facilities,
  hand, foot, and clothing monitors will be provided and their use will
  be required.

In this category are listed inadvertent, unexpected, unplanned and ab-
normal occurences and accidents which could or might result in personnel hazard
or area contamination of less than catastrophic proportions.

If a leak in the reactor occurs, radioactive liquid and radioactive
gases may be released. The reactor envelope is provided for just this
occurence. The released