Talk:Japanese nuclear weapon program/@comment-92.5.22.255-20160528084101

The Ni-go project and Godiva.

Translation of the Japanese Tonizo documents for 2nd February 1944.

Attendants: Dr. Nishina,   Major General Nobu-uji,    Technician Ishida (scribe?)

Nishina;

  ” If not powered gradually, there will be no controllable chain reaction in the 10 kg of uranium. According to my calculations, it is better to operate carefully in order to control this chain reaction. That is to say that the density of the uranium is lowered due to the expansion caused by the heat of the reaction. The lower density makes the reaction come to a halt.*   When this happens, the temperature comes down and increases the density, again enabling the reaction. This assumes an ideal situation and I do not know for sure yet. In any case we need to proceed with further experiments “.



* This is of course a description of 2nd criticality terminating the chain reaction. Criticality being the produce of density and radius. The latter determined by the effectiveness of the reflector.