The Japanese nuclear weapons program

Discussions on all aspects of the Japanese Empire, from the capture of Taiwan until the end of the Second World War.
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williamjpellas
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Re: The Japanese nuclear weapons program

Post by williamjpellas » 25 Sep 2018 22:42

Genro wrote:
16 Sep 2018 10:48
U-PULVER.
The only authentic record concerning the uranium that I know of is telegraph message from the dockyard referring to the uranium as U-Pulver (U-powder).
Interestingly, in a U-tube documentary we are told “finally the Americans find the cargo manifesto, Item 38; 500 Kg Uranium Oxide”. We are then shown a yellowish faded sheet with a crudely typed manifesto; No:38…560.0 URANIUM OXIDE JAP ARMY.
If this was indeed the German cargo manifesto it should have read; .560.0 URANIUM OXID JAP ARMEE.
The patent filed in America by IG Farben on removing sulphur from petroleum is in English but though out uses the German spelling of ‘oxid’.
Uranium oxide is a generic term and can cover UO2, UO3 and U3O8. The most probable contents was yellow cake, a uranium concentrate consisting of mainly sodium diuranate and for 560 Kg would contain 2.6 Kg U 235. Such a concentrate would pose no radiation or toxic/corrosive hazard.
Alright, then, here's a question for you.

If there was "no radiation or toxic / corrosive hazard", why was the uranium-in-whatever-form packed in gold lined canisters? Surely the logical explanation would be that gold, a very good absorber of neutrons, was used in order to guard against a chain reaction, right? Which would seem to argue against the idea that it was yellow cake. As Carter Hydrick does here:

https://www.youtube.com/watch?v=H1kWVnPNQac

Among the many declassified documents utilized in Hydrick's 27 April 2005 presentation is one dated 27 May 1945. It contains information told to American interrogators by Karl Pfaff, who was the second watch officer on board the German submarine U-234. The report, which appears at approximately the 15 minute mark in the video above, states:

"Interrogation Lt Pfaff Second Watch Officer U-234 discloses he was in charge of cargo and personally supervised loading all...tubes. Pfaff prepared manifest list and knows (what) kind (of) documents and cargo in each tube. Pfaff states long containers should be unpacked in horizontal position and short containers in vertical position. Uranium oxide (is) loaded in gold lined cylinders and as long as cylinders not opened can be handled like crude TNT. These containers should not be opened as substance will become sensitive and dangerous. Pfaff is available and willing to aid unloading if (military acronym I don't recognize) desires. Advise."

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Re: The Japanese nuclear weapons program

Post by wm » 25 Sep 2018 23:05

Gold-lined canisters wouldn't protect from anything, especially from neutrons.
Neutron shields need thickness to be effective and routinely are made as bricks 200mm wide (of parabore-25 or polybore-5 for example, at pinch paraffin is used).

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Re: The Japanese nuclear weapons program

Post by williamjpellas » 25 Sep 2018 23:32

AginAf wrote:
13 Sep 2018 03:53
As I understand it, we discovered at the onset of occupation in 1945, that the Japanese had had two nuclear weapon development programs on going at surrender. As was typical of them, one was conducted by the Imperial Army, and was based at several sites in Tokyo. The other was the Imperial Navy's, and was based in the port Wonsan Korea near the source of uranium in Manchuria.

Our experts were able to determine that the Army program was not very well along - years away from test. But we were unable to determine what the Navy had going because Wonsan and all of North Korea were occupied by the Soviets at the end of hostilities.

Then, in 1950, a Japanese nuclear physicist was granted an exchange with the University of Arkansas in the US' He disclosed that he had worked on the IJN's program during the war, and that they had successfully tested a breadboard bomb in the week between our first strike on Hiroshima, and our second on Nakasaki. US intelligence was unable to confirm this, and the Soviets, out to develop their own bomb thanks to secret data passed them by US & UK communist traitors, were not going to enlighten us.

The US AEC finally drew the conclusion that at best, the test was a low order explosion, but that is a guess

IF this is all factual, and the Japanese were enriching Manchurian U-235, then the IJN would have had no need of the U-234's cargo, because the Sons of Nippon were on the cusp of developing a weapon made from East Asian sources. One wonders how long it would have taken them to develop a weapon they could have loaded in one of their newly developed jet powered Baka kamikaze planes or their new 6 engine heavy bomber, or one of their suicide submarines and popped it in in the 7th fleet anchorage, thus turning the tide of the war.

This is a pretty accurate summary. I have a few "down in the weeds" details to add if it's not too pedantic.

I would generally agree that the IJA's nuclear weapons program was located largely on the Japanese mainland. However, there is also a slim tendril of documentation alleging that the Kwantung Army in mainland Asia / Manchuria was itself working on nuclear weapons. This was as a direct result of Japan's defeat-in-detail at the hands of the Russians at the Battle of Khalkin Gol, during the undeclared border war in 1939, When I visited the US National Archives in person at the Suitland, MD, headquarters, I found exactly one (1) document that made a brief mention of the Kwantung Army project. This came directly from Yoshio Nishina, who was himself the lead scientist of the Army's mainland nuclear weapons project under the supervision of the Tokyo Arsenal and its related Army bureaucracy. Naturally, I had just one photo of this one page document and it was the one that I lost (accidentally deleted from my laptop), out of more than 200 that I took. I do, however, remember the names of two National Archives Record Groups, and Nishina's statement is in one of them. It was either G-2 US Army Far East Intelligence Summaries from the very end of the war and the years immediately afterward, or it was in the files of the 5250th, which was a technical intelligence investigation unit whose members included a certain Captain or Major Kelly. Kelly's interrogation via interpreter of a Japanese technician who had escaped or defected from the Hungnam area is included in the 2nd edition of Robert Wilcox's book, Japan's Secret War.

Anyway, Nishina's statement is in one of those two boxes, if anyone reading this wants to make the trip to the Archives themselves and dig it out again. Nishina was telling US Occupation authorities that he personally knew another Japanese scientist who, during the war, had been working on the atomic bomb for the Japanese Army in Manchuria---presumably for the Kwantung Army---and that this scientist, who is not named in the document, was now working on nuclear weapons for the Chinese Communists. Given that the Communists won the Chinese civil war in 1949 and that Nishina died of cancer in 1951, it would put his statement between 1949 and 1951. There is exactly one (1) OSS document that I know of which alleges some kind of Japanese nuclear test in the Gobi Desert, apparently connected to the Kwantung Army project. It is my understanding at this time that the effort in Manchuria was separate from the mainland Project Ni, though Nishina's knowledge might indicate that the two centers of R&D were somehow connected, since Nishina himself was working for the IJA. It's difficult to say because although the Kwantung formation was nominally subordinate to the IJA high command, in practice it functioned more like a state within a state, similar to what the SS ultimately became in Nazi Germany. According to "machinga", an occasional poster on this forum and in this thread who is himself a very well-informed researcher in this subject, the OSS document is found in a larger group of papers known as "Project Verona". Note that this is not the same as "Project Venona", the US Army counterintelligence program that outed a large number of communist moles, spies, and sympathizers in the US government of that era.

As for Japan enriching U-235, my tentative summary at this time is that I don't think they had enough machinery to produce enough of it, fast enough, to complete enough bombs soon enough to turn the tide of the war. Unless they had a reactor (which would mean U-233 or P-239 rather than U-235), or one or more large separation - enrichment installations buried in the mountains in North Korea, they would have needed help---obviously from Germany---to acquire sufficient amounts of fissile material. As to how much they needed, my initial idea, as I described more than a decade ago in the very early days of this now gargantuan thread, was that Nishina's concept was probably for a gun-type bomb broadly similar to the US Little Boy device, as this would have been far and away the easiest to engineer and to build. However, that was an assessment I made before I got the chance to read a complete translation of the Kuroda Papers, aka the Tonizo Report. The original documents reveal that Nishina was certainly thinking about a U-235 bomb and performed a number of advanced calculations concerning it, but some of his wording---at least as it appears in the English translation I have read---might indicate he had in mind an implosion bomb rather than a gun-type weapon. J. Robert Oppenheimer sent a memo to General Groves immediately after the Little Boy bomb was dropped in which he urged the immediate junking of that design in favor of building modified, U-235 Fat Man bombs. Nishina was certainly and easily a good enough physicist to have realized the same advantages inherent in a much more efficient implosion bomb.

I am curious as to the identity of the Japanese nuclear physicist "granted an exchange with the University of Arkansas". If you mean Dr. Kazuo "Paul" Kuroda, he in fact served on the faculty of that school for many years and was involved in the WWII Japanese nuclear weapons effort, but he worked with Nishina for the Army, not the Navy. If there was another scientist who also came to the University of Arkansas other than Kuroda, that is news to me and I would like to know who that was.
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Re: The Japanese nuclear weapons program

Post by williamjpellas » 25 Sep 2018 23:33

wm wrote:
25 Sep 2018 23:05
Gold-lined canisters wouldn't protect from anything, especially from neutrons.
Neutron shields need thickness to be effective and routinely are made as bricks 200mm wide (of parabore-25 or polybore-5 for example, at pinch paraffin is used).
That is not what I have read, but I'm keeping an open mind. Why did the German nevertheless use them? And what of Pfaff's statement about making sure the gold lined canisters weren't opened during unloading?

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Re: The Japanese nuclear weapons program

Post by Genro » 27 Sep 2018 08:59

.‘However, that was an assessment I made before I got the chance to read a complete translation of the Kuroda Papers, aka the Tonizo Report. The original documents reveal that Nishina was certainly thinking about a U-235 bomb and performed a number of advanced calculations concerning it, but some of his wording---at least as it appears in the English translation I have read---might indicate he had in mind an implosion bomb rather than a gun-type weapon’.
In the Tonizo documents Nishina makes is no mention not even a hint on how the critical mass would that have been assembled. I would suggest you get the services of a new translator but not the chef from the local sushi bar.

With regard to the neutron the shielding effect of gold, I calculate that 10 or more centimetres of gold would reduce the flux to an acceptable level. Which would make the gold more valuable than the uranium !

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Re: The Japanese nuclear weapons program

Post by wm » 27 Sep 2018 10:20

A 10x10x10 cm brick of gold weights 20 kilograms so really it wouldn't be cheap.
A paraffin brick would more or less deliver the same results.

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Re: The Japanese nuclear weapons program

Post by williamjpellas » 27 Sep 2018 23:33

Genro wrote:
27 Sep 2018 08:59
.‘However, that was an assessment I made before I got the chance to read a complete translation of the Kuroda Papers, aka the Tonizo Report. The original documents reveal that Nishina was certainly thinking about a U-235 bomb and performed a number of advanced calculations concerning it, but some of his wording---at least as it appears in the English translation I have read---might indicate he had in mind an implosion bomb rather than a gun-type weapon’.
In the Tonizo documents Nishina makes is no mention not even a hint on how the critical mass would that have been assembled. I would suggest you get the services of a new translator but not the chef from the local sushi bar.

With regard to the neutron the shielding effect of gold, I calculate that 10 or more centimetres of gold would reduce the flux to an acceptable level. Which would make the gold more valuable than the uranium !
10 centimeters would be about four inches thick so yes, that would have been quite expensive. Perhaps the containers were lined with thinner gold plating and the Germans were thinking that some protection is better than none? It's difficult to say without doing a deeper dive into the declassified documents.

Care to respond to the transcription I made of the document referenced by Hydrick in his Oak Ridge presentation?

It is true that Nishina did not mention a specific method regarding how the critical mass would have been assembled. He talked about "ballistic assembly" but that just means that the subcritical pieces would have be fired into each other---regardless of how many pieces there were---in order to achieve an explosion. What jumped out at me was that nowhere did he speculate about the need for larger amounts of HEU to compensate for slower assembly of the subcritical pieces, as was the case in the gun-type Little Boy bomb. This of course is assuming that Japan could not have engineered a better gun-type weapon than the Manhattan Project did, but without seeing an actual Second World War Japanese atomic bomb design or design schematic---rumored to exist but never proven or reliably documented, at least as far as I have been able to determine---I will assume for now that a Japanese gun-type bomb would have faced many if not most of the same engineering hurdles overcome by the Allied project.

Nishina did talk about varying amounts of fissile material, but this was in relation to the purity and not to the method of assembly. Given that he seems to have confined his comments thusly, it appeared to me that he might have had in mind an implosion bomb, since he would probably not have to compensate for a slower coming together of the subcritical pieces with a weapon that was detonated by that method.
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Re: The Japanese nuclear weapons program

Post by williamjpellas » 27 Sep 2018 23:35

wm wrote:
27 Sep 2018 10:20
A 10x10x10 cm brick of gold weights 20 kilograms so really it wouldn't be cheap.
A paraffin brick would more or less deliver the same results.
The Germans did, in fact, utilize paraffin quite frequently in their various nuclear R&D efforts in WWII.

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Re: The Japanese nuclear weapons program

Post by David Thompson » 28 Sep 2018 01:07

Genro -- You wrote:
I would suggest you get the services of a new translator but not the chef from the local sushi bar.

Please avoid personal remarks in future posts, as our forum rules require.

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Re: The Japanese nuclear weapons program

Post by Genro » 28 Sep 2018 13:45

The Tonizo transcripts seem to be the only surviving record of work actually undertaken on the development of Japan’s atomic bomb. They are a record in part of the conversation between Gen. Nobu-uji and Dr. Nishina. They have been written as the meeting progressed by Ishida an engineer (gishi). Ishida is clearly new to the subject and makes a number of mistakes at first including the appropriate Kanji. Nobu-ji struggles with understanding the physics and Nishina resorts to some chemical analogies. Gen. Nobu-uji was head of the chemical weapons factory on Okunoshima Island until 1944.
Nishina description of the physics are clear and without any ambiguity as in the following on the subject of ‘a self-terminating chain reaction in U 235’ as in the Godiva experiments:-

計算によると________即ち反応のため発熱を伴い膨張し、従ってウランの濃度を低下することとなる。濃度うすくなれば反応が止まるまでになるのではないか。しかる場合温度低くなり、再び濃度を増す関係上反応行わる。以上は理想的の場合であって実際は未だ不明なり。

According to calculations______ that is to say the reaction will cause the temperature to rise and will simultaneously expand. Therefore the uranium density will fall, this is what will happen. This will cause the concentration to diminish until the reaction comes to a halt. If this is correct. In this situation the temperature will fall and again, as the density is related to this, the reaction will recommence. This assumes an ideal situation and is not known for sure.
2nd February 1944. Riken Institute, Tokyo.
Many references have been made to these documents by numerus writers which are not true. For example, Tokutaro Hagiwara did not lecture on an Hydrogen bomb, the equipment at Rikken was not held together with sealing wax, Nobu-uji does not want to replace all the U 235 with conventional explosives, Nishina does not propose to make a bomb from just 1 Kg U235, Nishina does mention he has enriched uranium to 10% and he makes no mention of how such a bomb will be assembled ballistic or otherwise.

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Re: The Japanese nuclear weapons program

Post by Genro » 28 Sep 2018 19:20

To clarify this neutron attenuation by gold the neutron capture cross-section for fission neutrons is given as 0.077 barns and for the scatter As 4.3 barns. ( 1 barn = 10^-24 cm2) Neglecting capture which is small in comparison, the attenuation No/Ni with thickness d is given by e^-d N As were N is the number of atoms cm3. N = p Av/Aw, p = density 19.3, Av = Avogadro’s constant 6.022 x 10 ^23 and Aw the atomic weight 197. Putting these together for d = 10 cm gives No/Ni = 0.08 about 10%.

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Re: The Japanese nuclear weapons program

Post by Genro » 30 Sep 2018 14:10

In the meeting of 2nd July 1943, Nishina states that the critical mass of 100% U235 with a tamper is estimated at 10 Kg and adds that does not make a bomb and that ” there needs to be extra”. What appears in so many novels is that ‘Nobu-uji says that 10 Kg of 50% U235 will make a bomb’.
What he actually says is that having achieves 10% enrichment of U235, that it would be no different from 0.7% (the natural level. The critical mass at 10% would be many tons.)
He goes on to say that there would be a considerable difference at 50 % (about 40 Kg) and that 100% is impossible.
Whoever has translated the Tonizo documents has miss led many and made a gross distortion of history.

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Re: The Japanese nuclear weapons program

Post by williamjpellas » 01 Oct 2018 05:48

Genro wrote:
30 Sep 2018 14:10
In the meeting of 2nd July 1943, Nishina states that the critical mass of 100% U235 with a tamper is estimated at 10 Kg and adds that does not make a bomb and that ” there needs to be extra”. What appears in so many novels is that ‘Nobu-uji says that 10 Kg of 50% U235 will make a bomb’.
What he actually says is that having achieves 10% enrichment of U235, that it would be no different from 0.7% (the natural level. The critical mass at 10% would be many tons.)
He goes on to say that there would be a considerable difference at 50 % (about 40 Kg) and that 100% is impossible.
Whoever has translated the Tonizo documents has miss led many and made a gross distortion of history.
Okay, but he is talking about a tamper, which is a neutron reflector. This is a standard feature in almost all atomic fission, boosted fission, and three stage (thermonuclear) bombs. So Nishina obviously knew what he was doing and was obviously working on building a bomb for Japan, even if he was "only" performing the calculations and working on the theory. Well, that and building his UF-6 prototype U-235 separator.

There is indeed "a considerable difference" at and above 50%. It is much more difficult to get to that level of separation - enrichment than it is to take the next step and achieve greater purity from there. The "home stretch", in other words, is much easier.

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Re: The Japanese nuclear weapons program

Post by Genro » 01 Oct 2018 10:02

17th November 1943. Nishina.
“Kayonishta U235 ganyu ritsu 0.7 %, yaku10 % tado ni naru”.
Thus the U235 which was initially at 0.7 %, is now at the level of about 10 %.

“Karui UF6 wo sarani joryu noshuku suru tame ni, bunri-to wo sarani ikki kenstsu-chu de aru”.
In order to further enrich the light uranium hexafluoride, a further separating tower unit is in the middle of construction”.

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Re: The Japanese nuclear weapons program

Post by Genro » 02 Oct 2018 10:23

It seems that work on an atomic bomb was widely known in the army but the enormity of the project and technology required does not seem to have been comprehended.
In the first meeting on 2rd July 1943, the project approved to run for one year and two officer seconded to the project. Most probably recent PhD conscripts. The funding is set at 2,000 yen, given that a bath house was 15 sen and ‘obento’ (lunch box) about 30 sen, in present day money I estimate about 40,000 £ say 30,000 $. A paltry sum for such an ambitious project.

My Early Days at the Imperial University of Tokyo.
Paul Kazuo Kuroda.
At about this time in the fall of 1944, a military officer from the Eighth Imperial Army Research Institute visited me in my office and told me that his group was ready to launch a massive counter attack aimed directly at the mainland of the United States. What the army officer wanted to know was, when the atomic bomb would become available.

No.76, Magic intercept.
At 13311 on 6 Aug the Kure Navel District issued “Hiroshima Air Raid Spot Report *3”, which include the following:
(4) “Research program: Research into the atom Uranium 235, are being* conducted at the Tokyo Imperial University under Army supervision and at Kyoto Imperial University under Navy supervision. [Words missing] have not gone beyond the limits of theory”.
*”Possibly “will be”.
At [place missing], about five months ago, research was made into the [practical] application of Uranium 235, but no announcement have been made since then. However, it is believed that research into the [word missing] of the atom has since been completed and [words missing] research into this is considered to be of considerable value. It is believed that it is essential that this be completed immediately”.

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