Hitler's Nuclear Weapons by Geoffrey Brooks

Author:Geoffrey Brooks
Language: eng
Format: epub
ISBN: 9781473815186
Publisher: Pen & Sword Books

Dismissing the question of isotope separation on these grounds, he considered it preferable to concentrate on achieving a working reactor without enriching the U235 isotope to do so. Throughout the report he emphasized the importance of using pure metallic uranium to reduce the absorption of transient neutrons by impurities in the fuel which might cause the collapse of the chain reaction.

Moving on to review the various moderators, Houtermans confirmed heavy water as a particularly efficient slowing medium for neutrons, but remarked on the enormous costs of producing it and the difficulty of assembling a large enough quantity for a working reactor.

He indicated the possible suitability of graphite, which appeared to have a favourable cross-section as regards neutron absorption, but expressed a reservation that what was gained by having no absorption losses might be offset by losses in neutron energies caused by graphite’s high mass number. The same applied to carbon in compounds.

However, what had been observed in the course of his experiments with moderators was that the absorption of neutrons by the hydrogen molecules in carbon compounds appeared much reduced at extremely cold temperatures. Now this was of great significance, for it was very probably attributable to the nuclear Doppler Effect. If that were to be brought into the reckoning then it would also bring about:

1. an increase in the fission cross-section of the U235 atoms by virtue of the T½ temperature energy law, thus making fissions much more likely, and

2. a reduction in the width and level of the U238 neutron absorption bands, thus increasing the probability that slow transient neutrons would avoid capture by U238 atoms.

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