Procedure for Critical Experiment

%DONRexp071053; ]> Procedure for Critical Experiment Machine readable transcription Murray, Raymond L, et al. Creation of machine-readable version: James M. Jackson Sanborn Creation of digital images: James M. Jackson Sanborn Conversion to TEI.2-conformant markup: James M. Jackson Sanborn ca. 15 kilobytes NCSU Libraries Raleigh, NC DONRexp071053

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Images of the document pages have been included. Procedure for Critical Experiment Raymond L. Murray, et al.

9 pp. Manuscript copy consulted UA105.1

Nuclear Reactor

Prepared for the North Carolina State University Science and Technology Electronic Text Center

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Library of Congress Subject Headings July 10, 1953 English LCSH manuscript 24-bit color: 400 dpi Procedure for Critical Experiment

NCSC-64 This is Copy 53 of __________, Series A.

Pile [unclear] Research Hughes Addison Wesley Pub Co Cambridge 42, Mass

PROCEDURE FOR CRITICAL EXPERIMENT

Clifford Beck with best regards Raymond L Murray A. C. Menius Jr. H. A. Lamonds

Raymond L. Murray & Operating Staff of Raleigh Reactor

July 10, 1953

Department of Physics School of Engineering North Carolina State College Raleigh, North Carolina

Went Critical at 00:59 Sept 5, 1953.with 787.95 gm U235 (93%)

PROCEDURE FOR CRITICAL EXPERIMENT

Raymond L. Murray & Operating Staff of Raleigh Reactor July 10, 1953 General Notes

1. The purposes of the critical reactor experiment are:

(a) To determine the critical mass volume and concentration of U235, at room temperature conditions, without water cooling of the core.

(b) To find the effectiveness of the control rod in terms of flux changes and equivalent fuel mass to determine the value of the shim plates.

(c) To note defects, if any, in mechanical or electrical equipment that should be corrected before the approach to full power.

2. The experiment is to be performed in a manner to minimize the possibility of exceeding the critical mass. Such excess would not be hazardous, in view of the strong negative temperature coefficiant, but could result in the neutron activation of components on which work is yet to be done. to avoid diffi- culty, the following viewpoints are adopted.

(a) The experiment shall be understood fully by all participants. Each person will know his role, including both the operation and the timing of it in the sequence.

(b) All activities will be under the direction of one individual. No par- ticipant is to act without specific instructions from the director. The latter will perform no manual operations.

(c) All actions should be performed deliberately, carefully and reversibly. For example if a portion of solution is added to the core, the operator should be prepared to withdraw that same amount immediately.

(d) The experiment will be performed with a minimum of comment and conver- sation and with complete attention to the operations.

(e) If a participant observes that some step in the procedure is not in keeping with safe practice, he may request that the operating group discuss the matter before going on.

3. The Operating Staff and assignment, for each are listed:

C. K. Beck Director J. T. Lynn(Turner) Addition of Fuel A. P. Sanders Assist in adding fuel; radiation monitoring J. G. Lundholm H. A. Lamonds Control desk and instruments A. C. Menius Source manipulation; recording data R. L. Murray Alternate Director; log book and recording data; Interpretation of results

After start of experiment, Beck or Murray will remain in Control Room at all times.

4. The four phases of the experiment are Phase 1 - CHECK-OUT OF EQUIPMENT Phase 2 - ADDITION OF OF MATERIAL DURING COUNTING PERIOD Phase 3 - FINE ADJUSTMENT OF MASS USING SOURCE AND CONTROL ROD Phase 4 - DE-ACTIVATION

Phase 1 - Check-out of Equipment

The completion of each item below will be reported to the Director and checked off on his list, with the name of the person performing the duty.

1. Assemble group of observers and operating personnel in auditorium to state rules of conduct and outline plans for experiment. (Beck)

List names of observers and participants in log book. (Murray)

2. Assemble operating personnel in contrel room for briefing. Provide seating facilities, writing space. (Beck)

3. Check that film badges and pocket dosimeters are on. (Sanders)

4. Test control room and reactor room monitor alarms with source. (Sanders) check limits on trips 4mm full scale

5. Check filling system. Air pressure, vacuum available. Valves all operable. (Lynn; recheck, Beck)

6. Supply of distilled water, assorted graduates, containers on hand. Rubber gloves for handling solutions. (Lynn; recheck, Beck)

7. Check public address system to and from reactor room and to auditorium. (Lamonds)

8. Source in place. (Menius)

9. Record books, graph paper, data on fuel available, clock or watches. (Murray) Ink supply and replacement pens for recorders, (Lamonds)

10. Check that all exposure ports plugged and locked except source opening. (Menius)

Run with water out of cooling coils 11. See that cooling water valves are closed. Remove valve handles. (Lundholm)

12. Lock all building doors except one designated for exit. Post signs no admittance. Brief department secretary on telephone calls if experiment performed in daytime. (Beck)

13. Lock doors entering to reactor room. Check electrical controls of doors. (Lundholm)

14. Test action of control rod and recorder indication of position. Repeat for safety rod. (Lundholm & Murray) Timing -- Rods up finally

15. Test rod drops. (Lundholm & Murray)

16. Test operation of shim control circuit. (Lundholm & Murray). Time -- Up finally

17. Test trips of PCP channels (Lundholm & Murray)

18. Collect prints of wiring diagrams for reference. Also have necessary tools, fuses, check instruments. (Lamonds & Lundholm)

19. Survey meters on hand and in operating condition. (Sanders) Zinc Sulphide crystals for testing of instruments , [unclear], location

20. Record specific list of operating instruments at time of experiment, which ones connected to alarm, which to trips; location of every instrument. (Lamonds)

List channels by name, location + detector locations, type of trips.

21. Test stabilitv of instruments with repeated counts. B10 #1, B10 #2, Fission chamber, BF3. Record observations. (Staff) also Bg on r channels + its voltage + Auto control reading + PCPs

22. Note response of instruments to introducing source in reflector. Record observation. (Staff)

Check symmetry of source by Auto.

Phase 2 -- Addition of Material During Counting Period

In this phase, the bulk of the U235 is added to the core. Predictions of the critical mass Mc are made after successive increments. The number of counts taken over a fixed period increases as the multiplication of neutrons increases. Thus 1/C approaches zero as the mass approaches Mc. Graphs of 1/C are repeatedly extrapolated to obtain improved estimates of Mc,

The enriched uranyl sulfate is supplied in individual bottles with U235 contents as listed

#1 200 grams 2 200 3 200 4 100 5 100 6 50 7 50 8 50 9 25 10 10 11 10 12 4 Total 999 grams

The chemical concentration is approximately 600 grams per liter. The total volume of solution as shipped is thus 1.67 liters. The final solution volume for the critical experiment is to be close to 13 liters. If the critical mass turned out to be 715 grams, this would mean that about 12 liters of water are needed. At full power an excess of 75 grams over the critical mass will be present. The ratio of hydrogen to uranium atoms then should be between 450 and 500. The addition of water and sulfate solution should be made in such a way that the atom ratio Nh/Nu is essentially fixed.

Assume that 430 is near but below the proper Nh/Nu ratio. To maintain this,

It is to be noted that there is noise in the switches on console + thus spurious counts in scalers. Overload in A.C. lines.

the water addition per 100 grams must be 1.5 liters. In the event that the critical mass is larger than 715 grams the water content should be kept low during the initial stages.

(Predicted critical mass 715 50 grams) 12.46 12.7

1. Initial conditions, Safety rod up, control rod down, shims up.

2. Take two background counts on instruments* with source far from core and no water in reactor. Time, 5 minutes. As the counting rate increases, the time may be reduced, being sure to keep statistical accuracy.

3. Insert source in normal position, centered under core.

4. Take two 5 minute background counts with source in position, Leave source alone.

5. Study reproducibility of data.

6. Add exactly 6.0 liters of distilled water to core. Record at sampling station. Note and report liquid level measurements. Note solution temperature. One person is stationed on shield, one at sampling control board.

7. Take two 5 minute counts. Study consistency of data.

8. Add two 200 gram bottles of fuel solution slowly. (400 grams). Record at sampling station.

9. Agitate solution by air pressure on lower filling tube for about one minute.

10. Take two counts with control rod in. Plot responses in form of 1/C vs. mass on graph paper. Extrapolate to expected critical point.

11. Check for a rise in neutron level. Write appropriate notes on recorder chart.**

12. Retract control rod completely at full speed, watching recorders, Note on chart. Take two counts with control rod out.

*B10#1 **B10#1B10 #2 B10 #2 Fission chamber BF3 BF3 Scintillation

13. Lower control rod in place. Estimate criticel mass with rod out with a separate plot of 1/C vs. mass. (Continuation of these curves down to the horizontel axis yields an estimate of the rod value.)

14. Add 1.5 liters of water to core, slowly, watching recorders. because add H2O would be possible

15. Add 100 grams of fuel solution. Record operation at sampling station, note solution level. Note solution temperature,

16. Agitate solution by air pressure on lower filling tube. Repeat steps 10 - 13.

17. Compute appropriate amount of water and solutien to add in next step, using data on manometer readings at shield end density-level graphs. Ultimate goal: 25.4 cm solution level at critical mass, Nh/N235 between 450 and 500, The corrolation of manometer readings and level may be taken from previously- prepared graphs.

Repeat steps 10 - - 17 as needed until within 5% of critical mass when the control rod is out.

Phase 3 -- Fine Adjustment of Mass Using Source and Control Rod

1. With all rods and shims out, pull source rod until source is back within shield. Note response on recorders. Exponential drop denotes sub-critical condition.

PUT SOURCE BACK IN PLACE

2. Add water and solution as directed, in small increments.

Note: If within 5% of critical, total that will be needed is no more than 40 grams of U235.

3. Retract central rod slowly after each addition, watching rise of flux as measured by recorder. Stop frequently to see if flux levels out. It is necessary to wait a sufficient time to tell whether the level is climbing to establish equilibrum or whether the reactor is exactly critical. At the exact critical point the counting rate climbs linearly. The critical mass is the one for which this occurs with the rod completely out.

4. Pull source into shield after each addition with the control rod out, noting response on recorders. (When flux stays constant without the source, reactor is critical.) PUT SOURCE BACK IN PLACE.

5. Lower control rod in the solution.

6. After critical point is reached, add an excess of one gram of U235 in standard manner. (Recorder traces should rise exponentially with time with the source in place, and exponentially with a longer period with the source out. This is the super critical condition, based on delayed neutrons. To detect the difference between the linear rise and exponential rise, the increases in neutron level in successive equal times are compared.) Put source back in place. Lower control rod until flux level is constant with source out.

7. Lower one shim. Observe amount of flux decrease on recorders, compare with level at a mass prior to the critical point.

8. Raise shim and lower other, to see if any differences exist, lower shim after observation.

9. Lower control and safety rod, interchange roles of the two circuits, then remove control rod to see if the value of the two rods are the same.

10. Check all ports + holes.

Phase 4 -- De-activation

1. Lower control rod and safety rod. De-energize controls and instruments.

2. Close valves of sampling system. Lock storage vault.

3. Close valves to off gas system. Put floor concrete block in place.

4. Remove source rod and store in wall.

5. Close and lock exposure port used for source pull.

6. Check that all other exposure ports are closed and locked.

7. Close valves in sampling lines, replace lid on sampling box and lock, being sure locking bars are in place.

8. Transport all containers involving U235 to safe. Check work areas for spills by survey instruments.

9. Annotate records of critical experiment.

Approval of Procedure by Participants:

C. K. Beck C. K. BeckJ. T. Lynn J. T. Lynn A. P. Sanders A. P. Sanders J. C. Lundholm J. C. Lundholm, Jr. H. A. Lamonds H. A. Lamonds A. C. Menius, Jr. A. C. Menius, Jr. R. L. Murray R. L. Murray