Talk:Japanese nuclear weapon program/@comment-92.5.22.255-20160530084223

Making of the Atomic Bomb. P.582,   [Lost in translation.]

2nd July 43.

Nishina tells Nobu-uji that the new explosive (U 235) requires a minimum of 10 Kg but this will not explodes unless an extra 10 Kg is added. But even then not all of it will explode, only a portion of it, the rest will be lost. Added to that, the bomb would requires an enormously heavy container.

On 2nd Feb 44, Nobu-uji enquires about the extra 10 Kg.

Nobu-uji: “ I understand that in order for the chain reaction of fission to take place, it is necessary to have an extra 10 Kg of uranium at all time but does the chain reaction work also on this 10 Kg ? ”

Nishina’s reply is not recorded but no doubt along the lines of the July 43 meeting.

Nobu-uji then enquires about the enormous container.

  “To use liquid oxygen as an explosive in a battle field, it needs quite a strong’ bombe’ container. Such a strong bombe must be also needed in the case of uranium.”

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif">Nishina: “ That is so but uranium would explode without oxygen or air”.

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif">On 17th Nov.44, Nobu-uji enquires yet again about the extra uranium.

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif">  “ Though the critical mass of uranium is 10 Kg, in the case of a bomb can’t we use conventional explosives instead? ”

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif">Nishina:  “(Sore wa dame.) That cannot be done. The chain reaction will stop if there is not enough uranium. Neutrons would escape if they don’t collide with U 235.When there is 10 Kg, only then do neutrons react successively ( tsugi kara tsugi e ) inside without escaping”.

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif">

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif">Note. Lt. Gen. Nobu-uji’s back ground is in chemistry having been from 1937, in charge of the Tadanoumi Chemical Weapons factory on Ohkunoshima Island ( Rabbit Island ) in the inland sea. While familiar with conventional explosives, the use of the new explosive ( U235)  seems to prove much more difficult to understand.

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif"> Nishina used a number of chemical terms in his explanations as an example, ’ joryu noshuku’ distillation enrichment, to describe the Clusius-Dickel separation technique. Though distillation has nothing to do with the process, it is clearly an attempt to put things in terms Nobu-uji might understand.

<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"TimesNewRoman",serif">In the meeting of July 44, Nishina points out the need of a huge factory that would require a vast amount of electricity. Nobu-uj may well have been chosen for this undertaking because of his related experience. The technology and enormity of the task was apparently not comprehended further up the hieratical command chain.