This memo discusses the efforts made by NC State to comply with safety suggestions made by the Reactor Safeguard Committee. It covers such areas as water sampling, evacuation procedures and precautions to guard against any exposure.
NCSC-65
On
COLLEGE
This memo reported the agreement reached between
atives of the Commission on a visit of the latter to the College on
was understood by
by the
the visiting group had been handled or were being arranged to the satisfaction of
all parties. The memo of
ments therefore are herewith presented.
1. Recommendations of the
(a) "The meteorological study on the stack gases, particularly under adverse
conditions in the immediate vicinity of the stack, should be continued". Studies
are now in progress on the relationship of exhaust air trajectories as a function
of meteorological conditions and the possibility of hazard from any radioactive
effluent that might be released. These studies will follow two lines: (1) visual
observation of smoke paths from the top of the stack under various weather condi-
tions, (2) area monitoring by radiation instruments when low levels of radioactivity
are present in the effluent.
The results of these studies will be used as a guide to the safe operation of
the reactor at successively higher levels. Any significant conclusions drawn from
these studies will be reported at appropriate
(b) "The open water reservoir of the Raleigh system should be periodically
monitored". The scheduled duties of the
monitoring of water samples from the
reactor operation is established. An interval of 3 or 4 months between sampling
periods is anticipated.
(c) "A direct connection of the tap water to the potentially contaminated line
leading to the coils within the reactor is undesirable. Other possible cross-
connections via the water system should be detected and eliminated." A complete
break in this line has been provided, as agreed. No other connections offering
possibilities of contamination are known to exist.
(d) "It was noted that a procedure for evacuation of the area in event of a
major disaster will be formulated". For initial operation of the reactor, up to a
power level of one Kilowatt, a building evacuation plan already worked out, will be
followed. Upon appropriate alarm signal, all personnel in the building will move by
the nearest door or window exit from the building to the street bounded edge of the
area (about 100 feet from the reactor). Designated persons will immediately begin
a monitoring survey to determine whether any unsafe conditions exist.
The procedure for evacuating the area in case of major disaster at maximum
operation level has not been completely developed. The portion involving evacua-
tion of the building and the area immediately adjacent thereto will be the same as
that described above. The plan for evacuation of surrounding streets and buildings
will involve the cooperation of the city police and fire departments.
2. Suggestions of the visiting committee:
(a) As finally installed, the instrumentation system of the reactor (9 indepen-
dent channels during start up and low level operation, 6 during subsequent operation
at high power) differs somewhat from the plan described in report NCSC-46.These
changes developed through efforts of the reactor staff to develop a more dependable,
safe system of instrumentation. The general plan and philosophy of safety have been
in no way changed. A brief review of the pertinent changes in instrumentation was
given to the visiting group. One change involved the installation of a relatively
slow operating trip of about 2 seconds on the period measuring channel. (This was
offset by addition of fast trips on other channels...to a total of 5 channels).
It was suggested, however, that this period measuring circuit be revised to include
a 0.2 second trip mechanism for reactor operation at lower levels. This change has
been made. It was further suggested that added speed of response "to the smallest
delay practicable" on the trip mechanism be provided for operation at high power
level. This will be done.
(b) A description was requested of the special precautions which will be taken
to prevent a person from being inadvertently exposed to the radiation beam from an
open beam port. In most cases, the reactor will not be in operation when a beam
port is open. After any adjustment of the shielding plugs in the beam ports, a
check of the radiation issuing therefrom will be made immediately after the reactor
is placed in operation again, and before persons are permitted to circulate in the
area. In special cases where a beam port is to remain unplugged during reactor
operation, two general precautions will be taken to prevent exposure: (1) access to
an appropriate area near the beam will be prevented by rope or chain barriers on
which warning signs are hung, and (2) appropriate shielding along the beam path to
prevent hazard from scattered radiation will be provided. The details and extensive-
ness of those two precautions will depend on the circumstances in each particular
case. If a very small beam emerges, e.g. into a small crystal spectrometer adjacent
to the reactor shield, only little shielding will be needed. If a large beam emerges
and crosses the room to the permanent trap in the wall, a tunnel of concrete blocks
along the entire path will be required.
(c) The landscaping plans for the area adjacent to the
the removal of considerable quantities of earth, before grass and shrub planting can
be started. After this grading has been completed a thorn hedge will be planted
around the perimeter of the area. Until the hedge is planted, and until it becomes
sufficiently large to present a serious obstacle to access, the perimeter of the
building itself will constitute the physical boundary of the exclusion area. The
building walls are about 55 feet from the center of the reactor.
(d) The half curie radium-beryllium source obtained for use as the neutron
source in the reactor was found to be too large to fit inside the re-entrant tube
in which it was to have been located. In the alternate plan devised, the source is
inbedded in paraffin in the hollow end of an otherwise solid wooden rod, 3 inches
in diameter and 8 1/2 feet long. This rod fits snuggly in the beam port which
traverses the reactor assembly immediately underneath the reactor core. When this
rod is in place, the neutron source will be just underneath the fuel cylinder, about
1 1/2 inches below the center of its bottom surface. Movement of the wooden rod,
e.g. during criticality manipulations, will present no likelihood of damage to the
source for it is completely enclosed in its protective cavity.
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