tion; Z 3 : production,the first figure involves the value ratio ofW233 and plutonium; the second derives from the U-~235 cy burn-up. . Fedative value figure contained Dr. Schreiber said that theA an assumption about the neutron velocity in U-233 | which is somewhat uncertain, If Pajarito measurements are correct the velocity may be higher than assumed, and the relative value correspondingly higher, Dr. von Neumann put the argument. for case B ast _ the bookkeeping mainly shows that case B would not make a major upset in. the thermoe-~ 3 nuclear program; for all other ‘purposes case B providess an ‘Amportant degree of freedom, po | o) ; Turning to Mr. Strauss, Dr. Rabi asked "why ask us, since 80 many advantages are evident?" Mr. Strauss replied that the advantages had . previously not been so clear, and that in any case it was an appropriate matter for GAC consideration, . Dr. Libby inquired as to the certainty of the costestimates, Discussion of Case B Mr. G. F. Quinn said that they were the best avallable, although it was true that experience was lacking in large scale thoriunprocessing.” Mr. Murphree asked whether there was a possibility that U-233 Possible U-233 Bomb Test Vee might have some disadvantage in weapons. Mr. Strauss said he had wondered about this and whether one should make a test before rushing into large scele production, Dr. Bradbury commented that a test would certainly be wanted, but that the low neutron background is definite