%MurNBoakridge021552; ]> Letter from Newton Underwood to Clifford K. Beck Machine readable transcription Underwood, Newton Creation of machine-readable version: Russell S. Koonts Creation of digital images: Russell S. Koonts Conversion to TEI.2-conformant markup: Russell S. Koonts ca. 12 kilobytes NCSU Libraries Raleigh, NC Modern English, MurNBoakridge021552

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 3 November, 2000

Nuclear Reactor Digitization Project

Raymond L. Murray Reactor Project Notebook

 Illustrations have been included from the print version. Scanned by Russell Koonts with Photoshop 5.0 software. Letter from Newton Underwood to Clifford K. Beck Newton Underwood

3 pp. February 15, 1952 Manuscript copy consulted UA 105.16

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

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Library of Congress Subject Headings English LCSH manuscript 24-bit color: 400 dpi Letter from Newton Underwood to Clifford K. Beck Typescript 3 p. February 15, 1952 MurNBoakridge021552

NCSC-49Murray 49 February 15, 1952 Dear Dr. Beck

Everyone was mo st cordial and helpful to me on my recent trip to the Oak Ridge National Laboratories.

the following conclusions and recommendations which I present are the result of my discussions with several different people in both the Y-l2 and X-10 areas and represent a blend of ideas and information obtained on this trip and modified by my overall background of our reactor developement. The people with whom I talked gave me information and ideas freely and generously, but wee reticent with advice. Therefore, the responsibility for the recommendations is mine.

1. If the theoretically computed fastest period of a reactor is of the order of 10 to 50 milliseconds, it is dangerous to assume that these calculations have thereby ruled out the probability of going prompt critical. In which case, a negative temperature will not prevent a disaster.

2. When any new nuclear fuel assembly is being put into operation for the first time, the maximum rate of control rod withdrawal should be such that the maxima rate of increase of reactivity is 1/1000 percent per second. After experience has been gained concerning its behavior, this rate may be increased to 1/100 percent per second. This implies that our control rod mechanism should be made to operate at a slower rate of withdrawal than is at present planned until we are able to judge the wisdom of the faster rate from personal experience with our reactor's behavior.

3. It may be advantageous to come to criticality by introducing a rather dry solution of the uranium salt in increments and watching the multiplication and then add the water moderator in small amounts until criticality is achieved. The information obtained from the Co/C versus mass curve needs to be supplemented by the information that is revealed when the source is removed from the nearly critical assembly.

4. The value of the rods must be carefully determined in the process of reaching criticality. That is, at each state of approaching criticality evaluate the rods before going to the next state.

5. In addition to electrical signal checks at all channels each day before operation, it is necessary to check each channel by moving a radioactive source.

6. The Oak Ridge logarithm circuits work quite well and reliably at least down to 10-10 amperes and the period circuit should afford 5 seconds "e" fold protection down to 1 watt on our reactor. Only one sensitivity range is needed for this channel.

7. it appears as if our automatic control should work down to 25 watts. There is not much value in automatic operation at lower levels.

Boron 10 ionization chambers operating at 400 to 600 volts and at such size that 50 - 100 micro-amperes equals 1010 flux should be used. It is necessary to flow gas through them continually, otherwise their calibration will shift. These chambers have carbon electrodes that have been coated with a boron 10 oil dag and burnt off. Quartz insulation is advisable.

8. One channel must always "see" the source. This had best be a U 235 pulse chamber. This chamber feeds into a pre-amplifier, then into a linear amplifier and discriminator (so that the γ ray back- ground can be suppressed) then into a scaler and rate meter.

9. Hard tube fail safe trips are thought to be better than thyratron trips.

10. The nitrate solution appears to be the wisest choice from the viewpoint of chemical stability.

11. We should build our own equipment which cannot be bought "of the shelf".

12. Indium foils and film badges should be strategically located in the reactor room at all times.

13. Each p erson needs.- two slow neutron ionization chambers, two γ ionization chambers and a film badge.

14. For general monitoring purposes a Cutie Pie is wise. A Zeuto is used for α monitoring. Air must be monitored by forceing it through a piece of filter paper which is measured in a scintillation counter. A frisker may be a better choice for general personal monitoring than a head and foot monitor.

15. Our plan for coating a water-proof Geiger counter with strippable paint and silicone may be all right for a liquid monitor.

16. A thermal flow meter may be desirable in the recombiner system.

17. A liquid depth guauge based upon using the solution as a dielectric which rises into a cylindrical condenser and varies its capacity may work.

A good deal of valuable specific information about apparatus

was obtained which is not appropriate for this letter.

A list of drawings and documents which should be requested is enclosed.

I enjoyed the trip vary much and believe the information obtained will save us a good deal of time and money and result in an overall improvement in our instrumentation.

In view of the fact that secret information was involved in some of the discussions, I as sending copies of this letter to Dr. Callihan and Dr. Jordan so as to be sure that I have not inadvertently included any such information in the letter. To the best of my knowledge and belief, I have not included any secret information. However, I will, await a reply from them before releasing this letter to our general reactor committee.

Sincerely yours, Newton Underwood cc to Dr. Dixon Callihan Dr. W. H. Jordan Mr. Ray Murray Dr. A. C. Menius