X-822 OAK RIDGE NATIONAL LABORATORY ~ Operated by Diisenof Union Caride Crpretion ORNL Post ? BoxX . | CENTRAL FILES NUMBE_R GO~ 12 - 11 Oak Ridge, Tennessee s S | | External Distribution Authorized I“ - . DATE: December 13, 1960 =~ copv'No.égy/ 2 SUBJECT: Homogeneous Molten Balt Reactors ' TO: Distribution FROM: C. W, Néstor, Jr. Z‘-‘ | . SUMMARY ‘_t ’Multigroup one-dimensional calculations were done recently to obtain estimates of critical masses, power density distributions and fission=- ing spectra for some homogeneous molten salt reactors having outer reflectors and central "islands," placed inside the currently proposed MSRE vessel. For a 5-inch-thick outer reflector and a l-ft-diameter island, both beryllium, the calculated critical mass is 108 kg; 40 percent of the fissions occur at thermal, and the maximum power | density of 3.9 times the core mean power density occurs at the island- salt interface. If the reflector thickness is increased to 10 inches, the critical mass is reduced to 34 kg; 67 percent of the fissions occur at thermal, and the peak power density of twice the core mean again occurs at the core island=-salt interface. } g NOTICE A This document contains information of a preliminary nature - - : _ o . and was prepared primarily for internal use ot the Ock Ridge P National Laboratory. It is subject to revision or correction ’” o : _ and therefore does not represent a final report. The information - is not to be abstracted, reprinted or otherwise given public o : dissemination without the approval of the ORNL patent branch, . o | . Legal and Information Control Department. - - A v HOMOGENEQUS MOLTEN SALT REACTORS - C. W, Nestor, Jr. Multigroup ohe-dimensional calculations were done recently to obtain estimates of criticel masses, powef.density_distributions-andfissioning spectra for*éame homogeneous molten salt reactors having outer reflectors and central“islands,“ placed inside the currently proposed'MSRE véssel as shown in Fig. 1;_ The salt camposition, listed in Teble l, is that of the | Current MSRE mixture.l Results of these calculations are given in Tfible 2,with earlier results for the cgrrent.MSRE.and some results for bare hOmogeneous molten salt re- actors,2 Included for cbmparison..waerdenéity shapes for the reflected reactors are plotted in Figs. 2,'3,7h, and 5. Teble 1. Selt Composition Compound =~ : - Mole % LiF | | | T0 Be32 . | 1 : - 23 UEh o . . . " ad (&s required for criticality) 1w R. Grimes, letter of Aug. 23, 1960. 2 7. A. Lane, H. G. MacPherson and F. Maslan, eds., Fluld Fuel Reactors, Addison-Wésley, 1958 “y Island and reflector material C Be BeO Island and reflector material C . Be BeO Reflector'_ material Cc Be BeO ..Reflector_ , material C. Be Beof Tgble 2 5" reflector thickness, 1 £t island diemeter - | ' '~ Percent Mole % Core critical thermal uranium mass, kg ~ fissions - 0,90 . 206 | ) 13.2 Ry - 168 | ': ho.2 0.54 24 - 32.8 10" reflector thickness, 1 £t islend dismeter Peréent Mole % Core critical ‘thermal uranium | mess, kg fissions - 0.67 . 93 - 332 0.2 3 6T.3 0.28 39 62.0 5" reflector thickness, no island - ' - o Pgrcent Mole % Core critical thermal - uranium _mass, kg fissions .06 25 4.6 0,76 - 186 - 16.0 “10" reflector thickness, no islend - Percent Mole ¥ Core criticel thermal uranium mess fissions 085 130 20.6 0.43 65 k6.5 0.46 n k1.5 Median fissioning energy, ev 100-150 Te5~ 10 20 - 25 MEdian.' fissioning energy, ev 20 - 25 thermal thermal Median fissioning ener ev 150-400 - 50~ 65 - 80~ 90 Median fissioning - ener ev 65-80 - 008'1 ..h- 7 . 5"10 ’ Current MSRE (12 volume percent fuel salt, 88 volume percent graphite) | | | Median Mole %. Core critical ‘Percent thermal fissioning ~uranium mass, kg fissions L energy, ev 0.27 13 | oLk o thermal Bare molten salt reactor (5 £t diameter sphere, 30 mole % L]3<~3F2 + 68 mole % LiF + 1 mole % ThF; + ~l mole % UFA) _ : ' . - Medlan Mole % - Core critical Percent thermal fissioning - uranium ___Dass, kg ~ fisslons ‘ energy, €V 0.94 ' 239 . . 0.040 425 MIDPLANE { UNCLASSIFIED ORNL-LR-DWG. 64772 ¢ (OR 18") ISLAND CORE 33" (HALF-HEIGHT) ‘L—-G"‘—-h*—-—.—— '3" MM '0“ _—-’- (OR 5") REFLECTOR ~ Fig. 1. Reacfpf:Mbdél.:_ POWER DENSITY/AVERAGE POWER DENSITY UNCLASSIFIED ORNL-LR-DWG. 54773 ISLAND - e _ CO'RE g REFLECTO&_' 4.0 Be BeO C 3.0 2.0 1.0 o l— . — _ ' a_— o . - 10 B ‘ 20 _ : -~ 30 | ~ RADIUS, in. Fig. 2. Po'wer-Dje_nsH:y Disiribufloné Associated ‘with a 6" Island and a 5" Reflector. POWER DENSITY/AVERAGE POWER DENSITY 0.5 3.0 2.5 2.0 1.5 1.0 RADIUS, in. o Fig. 3. Power D'\ensii‘y Disiribuiions Associated With a 6" Island and o 10" Outer Reflector. UNCLASSIFIED ORNL-LR-DWG. 564774 tseano | CORE o REFLECTOR c Bel \ BeO | o 10 20 30 - POWER DENSITY/AVERAGE POWER DENSITY UNCLASSIFIED ORNL-LR-DWG. 54775 L b CORE sl REFLECTQR 2.0 7 I 1.5 l Be BeO | \ | BeO o _ ' f AVERAGE |— o= W e | _ - 0.5 ' 8 S — o 10 | 20 30 RADIUS, in. Flg 4, Power Denssty Dlslributions Associoied th a 24" Core cmd a 5" Reflecior POWER DENSITY/AVERAGE POWER DENSITY © N o - - UNCLASSIFIED ORNL-LR-DWG, 54776 m . e yBeO 0 0 AVERAGE 8= = 5 . 0 10 20 RADIUS, in. . Fig. 5. Power Density Distributions Associated ~ With a 19" Core and a 10" Reflector. o | 30 -~ w . 10, ll. 12. 13. l)'l’. 15. 16. 17. 18. - 19. 20. 21, 22, 23. 24, 26. 28. 29. 30. 31, 32. 33, 3L, 35. 36. 3T. 38. v -} L. - S. A. C. E. A, S. RC F. D. W. R. W. Je V. G. Je D. W. A. J. W. W. E. We P. R. B. M. ‘H. We E, W. 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