Memorandum from Raymond L. Murray and A. C. Menius, Jr. to Dr. Clifford K. Beck

%MurNBcriticalmass080951; ]> Memorandum from Raymond L. Murray and A. C. Menius, Jr. to Dr. Clifford K. Beck Machine readable transcription Murray, Raymond L. Menius, A. C., Jr. 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. 9 kilobytes NCSU Libraries Raleigh, NC Modern English, MurNBcriticalmass080951

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20 October, 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. Memorandum from Raymond L. Murray and A. C. Menius, Jr. to Dr. Clifford K. Beck Raymond L. Murray A. C. Menius, Jr.

2 pp. Manuscript copy consulted UA 105.16

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

The lineation of the manuscript has been maintained and all end-of-line hyphens have been preserved.

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Library of Congress Subject Headings August 9, 1951 English LCSH manuscript 24-bit color: 400 dpi Memorandum from Raymond L. Murray and A. C. Menius, Jr. to Dr. Clifford K. Beck Typescript 2 pp. August 9, 1951 MurNBcriticalmass080951

Aug 9, 1951NCSC-32 TO: Clifford K. Beck FROM: Raymond L. Murray and A. C. Menius, Jr. CC: Arthur W. Waltner and Newton Underwood SUBJECT: Estimate of Critical Mass

A new estimate of the critical and operating mass of the Raleigh Reactor, based on the more recent version of the Los Alamos Water Boiler is discussed.

In summary: It is recommended that the reactor core be made with inside diameter 10 3/4", inside height 11" (1.08" clearance at top), to accommodate 900 grams of U-235 at a hydrogen ratio of 400 (anhydrous uranyl sulfate l0% by weight) solution density ≃ 1.1 g/cm3.

The main differences between SUPO and our reactor are as follows: SUP0RaleighSpherical shapeCylindrical shapeCooling Coil length 60 ft.Cooling Coil length 27 ft.Nitrate solutionSulfate solution (tentative)

The number and dimensions of exposure tubes, control rod sheaths, etc., are enough alike so that it is unprofitable to estimate differences due to them.

An analysis of the effects of changes listed above is given.

Shape. The critical volume (and mass) of a bare cylindrical reactor of given hydrogen ratio is theoretically 1.14 times that of a bare spherical reactor. The effect of a reflector is to reduce this discrepancy somewhat, so that this can be considered as an upper limit.

Cooling Coil. In the conversion at Los Alamos from LOPO to HYPE an estimate was made of the worth of cooling coils that turned out to be quite accurate. The addition of 157" (13.1') of cooling coil made an 80 gram increase in U-235 neces- sary, implying a 6 ft./gram effect. The difference between SUPO and Raleigh cooling lengths is 33 ft., giving a predicted 200 gram charge. This value may be high because a linear extrapolation may be incorrect.

Solution. The critical mass for a nitrate solution is quoted to be 70 grams higher than that for a sulfate solution at 14.7% U-235 concentration.

Estimate of Mass. Starting with the experimental critical mass of SUPO of 870 grams of U-235, the change to sulfate would bring it down to 800 grams. A change in shape brings it to 1.14(800) = 915 grams, but the cooling coil difference cuts it back to 215 - 200 = 715 grams for the critical mass. Adding 60 grams a for the temperature coefficient and 15 grams for excess reactivity, gives a final value of 790 grams for the operating mass.

In the design of the core provisions should be made for the possibility that the effect of cooling length reduction is not as high as linear extrapolation would predict, that the extra void at the top and the void between the bottom of the solution and the graphite introduces loss of reactivity, and that nitrate may be

used instead of sulfate.

Since it is preferable to err in the direction or too large a container size, requiring that the actual solution used be of lower concentration, it is recom- mended that 900 grams be assumed in establishing the core size.

Estimate of Reactor Size. The volume of container will be the sum of the necessary tubing voids and the solution itself.

By the applicable chemical relations, the solution volume is V=(0.0383 h + 1.72) M/ρ for 90% U-235 with ρ = 1.095 k/cm3 at h = 400, and M = 900 grams, V = 14,005 cm3 The total volume of voids is 706 cm3, or broken down as follows; Cooling coils 27.1' of 5/16" O.D. pipe408 cm3Control rods 2 x 9.7" of 13/16" O.D. pipe165 cm3Reentrant tube 8" of 1 1/8" O.D. pipe130 cm3Thermocouple 6.1" of 3/16" O.D. pipe3 cm3706 cm3

bringing the total to 14,711 cm3.

For a bare cylindrical reactor, the optimum height is 1.8475 times the radius, so that the volume is V = πR2H = 5.804 R3 Thus R =

D = 27.27 cm or 10.74" H = (1.8475) (13.635) = 25.19 cm or 9.92"

A space of approximately 1" between the solution and the inside of the top of the container is proposed.

The recommended fixed dimensions of the core are--Inside Diameter 10 3/4", Inside Height 11".

Volume of top space

weight of steel in walls.A=2(πR2) + 2πRH=2[π(5.375)2] + 2π(5.375)(5)=2[π][28.8 + 26.8]=(6.28)(45.6) = 286 in2V=(286)(1/16)=17.9 in3 = (17.9)(16.387) = 282 cm3M=Vρ=(28.2)(8.0)(assumed) = 2340 g = 2.34 kg