The Japanese nuclear weapons program

[williamjpellas]

Having said all of this, and with due thanks and appreciation to you, Genro, for your excellent work and gracious sharing of that work, it appears to be pretty well established that there was NOT a "bomb design" as such in the Kuroda Papers. That is, there was not a bomb design in the nuts and bolts, blueprint, here's-how-we-engineer-this sense of the term. There certainly WAS a bomb design concept, ie, a U-235 gun-type bomb that was very similar to the American Little Boy weapon, even to the point of including 1) a polonium "spark plug", 2) a beryllium tamper, and 3) two sub-critical pieces of HEU that would then be brought together in a split second in a gun barrel---Nishina's "ballistic assembly"---by firing one into the other.


This appears to be where the English translation of the Kuroda Papers leaves us, at the moment, in terms of the historical research into the WWII Japanese atomic bomb projects in general, and the Riken-Nishina-Project Ni effort in particular. There is, of course, still the Navy's Project F-Go, both on the mainland and in Korea, and also possibly a third center of R&D on the Chinese mainland.


There is one last additional piece of evidence of which I am aware when it comes to an actual bomb design blueprint. Although it is anecdotal, I think it is still worth mentioning. This is the story told to Robert Wilcox that is included in the second edition of Secret War, in which a random Army surgical tech in the US Occupation force in Japan named Leon Thompson claimed to have seen an actual diagram / blueprint of a Japanese atomic bomb design. The story is archived, in truncated form, here: http://www.grunt.com/corps/scuttlebutt/ ... -lost-all/ Wilcox's book gives more detail and context.


Thompson obviously did not know much about atomic weapons or bomb physics---as when he confuses plutonium with uranium---but the broad brush strokes of his story are certainly consistent with other aspects of the research into this topic that are well-documented (such as the voyage of the German submarine U-234 to Japan, and the fact that its cargo included some kind of nuclear material intended for a weapon, and that Japanese military planners had already selected targets for a potential nuclear strike). Thompson claimed that a mysterious "Mr. Papps" was surprised by a couple of KGB toughs or other Russians of some sort while he was on the street in Tokyo, or else that he knew he was being followed by them. In any case he (Papps) was fleeing on foot when he encountered Thompson. "Papps"---if that was his real name---immediately introduced himself to Thompson, grateful and enormously relieved to have found an American, any American, who was wearing a uniform. The presence of this bewildered soldier apparently convinced the Russians that they should head off in another direction, presumably to lie in wait for Papps or another intelligence target when the target would be more vulnerable and when there would be fewer or no witnesses. Thompson, in other words, may have unwittingly saved Papps' life, after which Papps explained that he had been in danger from the Russians. In gratitude, Papps supposedly gave Thompson a look at the bomb diagram, which was posted on the wall in his or General MacArthur's office (the wording in the article is not clear on this point). While at first glance this would seem unlikely because presumably Thompson would not have had the necessary security clearance, this was the late 1940s and it was during the Occupation, and US forces in general were rapidly losing their edge and readiness (as German forces did in occupied France) and rules and regulations in general were much more lax than they were in wartime. Just how lax would be demonstrated when fat and happy Occupation troops were subsequently rushed to Korea when the North Koreans invaded; many US soldiers quickly contracted "Bug Out Fever" in the early days of that conflict. So, the notion that he might have caught a glimpse of something that would otherwise have been, to use contemporary terminology, highly classified, is perhaps not as unlikely as would first appear to be the case.


Again, Thompson's story---as the website above on which it is archived indicates---is basically "scuttlebutt". Rumor or anecdotal evidence, though of course Thompson did claim to be an eyewitness. However, it is still intriguing and some of its details are quite accurate. So while it is not a smoking gun it is still a worthwhile footnote, I think.

[williamjpellas]

Came across an interesting find today. I'm guessing that other researchers into this topic may have seen this before, but I've not seen it in this thread or on this site before, so here it is. Below is a link to an article originally published in Life magazine, and dated 24 December, 1945. The article is called "Cyclotron Smashing" and has a number of photos of the actual destruction of Nishina's cyclotrons at the Riken Institute just after end of the War. Nishina had two cyclotrons, the first and smaller one being a virtual duplicate of Ernest Lawrence's machine at the University of California - Berkeley, and the second one built by Nishina himself, with help from Riken staff. Included in the article is a photograph apparently taken literally at the moment that the eminent Japanese scientist was begging the Occupation troops and officials not to destroy his machinery.


But the best and most important feature of the article is found in the text, which claims: "His apparatus could not have been used to make an atomic bomb". Ummm, well, that's a nice bit of linguistic sleight of hand. It was true, sort of, that Nishina's equipment "could not have been used to make an atomic bomb" if by that you mean, "was not the exact equipment needed to machine highly enriched uranium or to assemble sub-critical pieces of bomb fuel into an actual bomb casing". Yeah, that's true. And it's also true that cyclotrons in the small number that Nishina possessed were not capable, in and of themselves, of producing enough fissile material via particle bombardment to have enabled Japan to detonate an atomic explosion. But of course, what the article doesn't tell you is that Professor Nishina very definitely did use his cyclotrons to calculate the neutron fission cross section of uranium to a highly accurate extent, and that that calculation was one of the most crucial ones necessary before a bomb could be built. So yes, he was obviously working on the atomic bomb, and that very diligently, for Japan. And yes, there were quite obviously powerful interests in the United States that wanted all of this to go away quietly, as the article demonstrates with its obvious half truths and spin-doctoring. It would be interesting to learn if LIFE itself was an active participant in the cover-up, or merely parroting what its reporters heard from Occupation or Army officials.


http://books.google.com/books?id=BkkEAA ... nk&f=false


Nishina himself added his own lie when, according to the caption beneath the photo of him pleading with the soldiers, he said, "This is ten years of my life. It has nothing to do with bombs". Sure, now that the War was over, Japan was beaten, and Nishina had returned to his considerable peacetime work, yes, that's right, under those conditions, his equipment "...(had) nothing to do with bombs". Not anymore.

[Genro]

Having now completed the translation of all the 23 pages of the Kuroda documents and analysed them closely, I conclude that the atomic bomb project remained within academia. The vital nuclear parameters were not know to a reasonable accuracy as this would require highly enriched U235 and Nishina was only able to achieve 10%.

As Heisenberg said “ From the very beginning German physicists had consciously striven to keep control of the project___” and so did Nishina in his own way.
From the 1946 Smyth report , Initially many scientists could and did hope that some principle would emerge which would prove that atomic bombs were inherently impossible. As history shows, American physicist relinquished that control to the military.
The American scientific community protested at the destruction of the Japanese cyclotrons but to no avail, the military was intoxicated with victory and hell bent on revenge.

This desperate search for a Japanese atomic bomb is a fantasy no doubt driven by the need for redemption over the bombing of Hiroshima and Nagasaki.
A fantasy possibly for a Hollywood action film not unlike ’ U571’ which I will remind everybody cost the lives of two brave British sailors in recovering the enigma coding machine from U559 German submarine.
Are we going to see Rambo dropped from a B52 over Korea and landing in a paddy field, with out a parachute of course and armed with only a samurai sword. Defeating the Kwantung army, destroying the atomic bomb factory and capturing Tokyo Rose.
It would probably make an exciting film but that’s all it is, reality is some thing different.

[williamjpellas]

No "redemption over the bombing" is necessary or needed. The only way to draw the conclusion that one is needed is if you believe---as I do not---that the Japanese surrender feelers being sent out through various channels in 1945 were good faith efforts aimed at the United States, and that the United States---murderously and with malice aforethought---deliberately ignored the poor pitiful Japanese in order to prolong the war long enough to drop the bombs. I would like to see your "proof" for such assertions. Other than the incoherent ramblings of people like Gar Alperovitz, that is.

The MAGIC intercepts that I have viewed do NOT give the impression that the Japanese were sincere in their attempts at securing some kind of diplomatic exit from the war. That's because the Japanese diplomatic effort, from all that I have read, was NOT being carried out with the goal of direct communication with the United States. Rather, the Japanese were trying desperately to split off the USSR from the Allies. Their goal was to get the Soviets to broker some kind of negotiated peace on terms favorable to Japan, and along the way to avoid "losing face". Failing this, they were determined to prolong the war long enough to force the US and its allies to carry out an amphibious landing in Japan itself in order to draw their enemy into brutal, man to man, close quarters combat. In pursuing this course of action the Japanese leaders put their Bushido concept of "honor" ahead of the lives of tens of thousands and, really, hundreds of thousands of their own people.

The "fantasy" here is the notion that somehow scientists in the various combatant nations in WWII were, taken on the whole, some sort of principled passive resistance leaders who were determined "...to keep control of the project". Except for the Americans, who were specially and uniquely evil, you see. Naturally and of course. This is the very worst sort of deconstructionism and retroactive and selective pseudomoralizing, to say nothing of America-bashing, from where I am sitting. Some, particularly in the United States, did speak out according to their lights, that is true for what it's worth. Funny how the comparatively free and open society in the West, which permitted this kind of open dissent, somehow comes in for more criticism than the comparatively brutal and totalitarian and militarist regimes of Nazi Germany and Imperial Japan---who started the War in the first place, remember?---but okay, I'll play along. The "...(American) military hell bent on revenge"? You couldn't prove that by the practices of the American Occupation of either Japan or Germany. Really, Genro, you can't be serious with either that statement or with your silly and gratuitous reference to Rambo. Oh, wait, I get it: anyone who believes, or merely suspects, that there is more to the story of the WWII Japanese bomb projects is, obviously and was there ever any doubt, an ignorant right wing American nationalist with a juvenile, jingoistic, passé, and altogether and plainly false view of the world. To say nothing of, ahem, unsophisticated, unlike the cosmopolitan intellectual elites. Right?


The Riken - Kuroda - Nishina papers do not prove what you say they prove. Plainly and obviously and for the simple reason that we know beyond any doubt that the Japanese bomb projects continued on well past the date at which the Kuroda Papers cease, a date which you give as some time in November, 1944. That leaves nearly a full year before the end of the war in August - September 1945. What happened during that period of time? Do you, in truth, know anything about the evacuation and reconstitution of Japanese atomic weapons R&D to the Korean mainland? The US conducted several postwar investigations of Japanese atomic weapons research in the years immediately following the war, investigations summarized well by Robert Wilcox in his 2nd edition of Japan's Secret War. It may (or may not) be true that Nishina was unable to precisely solve, for example, Fermi's "Four Factor Equation" to a degree of accuracy sufficient to produce an atomic explosion if a bomb could be engineered. I don't believe this, personally, but alright: it's a possibility. But even if Nishina himself was a dead end or came to a dead end---something that cannot be proven from the Kuroda papers themselves, important though they certainly are to WWII historiography---what about Arakatsu and his future Nobel-winning theoretician, Hideki Yukawa? They were the leaders of the Navy's Project F-Go. What about Project F-NZ in and around Hungnam? Again, you're obviously not serious here, Genro, and that's a real shame because the work you have apparently done with regard to the Kuroda papers is welcome and significant.


For the record, I have never denied my assertions in various places that there has been a concerted attempt in some quarters to hijack and distort the history of the Second World War to further a particular left-leaning political agenda. Even without "a working (bomb) design" as I evidently mistakenly labeled it (here assuming that your translations are correct) in my published article on the subject, "The Japanese Bomb and Why It Matters"---and in making that statement I was relying on the BBC and Japan Times articles on the Kuroda Papers---but even without a working Japanese bomb design, NO "redemption over the bomb" is needed or necessary. I repeat: NO redemption is necessary whether they had or came close to a working bomb or not. Absolutely not. Japan was NOT going to surrender before her last planned throw of the dice, which was Operation Ketsu Go, the "decisive battle of the Homeland". Their plan, which MAGIC intercepts show conclusively to my mind, was to hold out long enough to force the Allies into the planned amphibious invasion, Operation OLYMPIC, where Japan would have the opportunity to bleed the Allies, and particularly the United States, white. The certain slaughter of hundreds of thousands of Japanese soldiers and an even greater number of civilians during this battle was of no concern whatsoever to the militarists who still controlled Japanese government and society right up until the atomic bombings---and even slightly beyond them. No, they were determined to force the Allies to land, after which the ensuing outcry from an American public already war weary following the surrender of Germany would provide the political capital that Japanese leaders were counting on to gain them a negotiated peace on terms more favorable to Japan than they were likely to get otherwise. (Or so they thought: again, the American Occupation was surely among the most benevolent that any foreign power has ever carried out in any conquered nation throughout all of history.) I find it puzzling and frankly infuriating that so many armchair critics of the US and Allied conduct of the end of the war place so much emphasis on the atomic bombings and none whatsoever on the plainly bankrupt and malevolent moral calculus (and policies and actions) occurring in the Axis nations.


By the way, and since you are obviously part of the "they shouldn't have dropped the bomb and how dare they" crowd, betcha didn't know that a number of Imperial Japanese Army staff officers who were part of the detailed planning for Ketsu Go were based at and working in---wait for it---Hiroshima. About 80 of them died in the blast. The atomic bombs thus directly struck Ketsu Go and literally and figuratively destroyed it as an instrument of Japanese strategy. That's because, particularly after Nagasaki, the Japanese---thanks to field analysis in Hiroshima and Nagasaki led by Nishina and Arakatsu---realized that the United States possessed multiple nuclear weapons and had the ability to deliver them from a stand-off posture. These two facts, nuclear weapons mass production and the ability to deliver them on target from a position of near-invulnerability, completely invalidated the Japanese endgame virtually overnight, even though hardliners, unbelievably, still wanted to hold out even after Nagasaki. Ketsu Go evaporated, and Tokyo had no more cards to play other than to beg for the Emperor's life, which---reading between the lines of the government's response to the atomic bombings---she did. The United States and the Allies let Hirohito live in order to help ensure a peaceful Occupation and the entry of Japan into the Western orbit as a bulwark against Soviet expansion in the Pacific.


It's a shame to see you resort to such statements and tactics as you exhibit in this thread, Genro, particularly after the excellent work you've apparently done in achieving a presumably more or less accurate translation of the Kuroda documents into English. I think, or at least would like to believe, that you're capable of better and I hope you will demonstrate that in the future.

[williamjpellas]

I am also curious how you arrived at the "conclusion" that Nishina "...was only able to achieve 10%" enrichment of uranium. Leaving aside the rather shocking notion that the Japanese achieved ANY enrichment of uranium during World War II---something that flies in the face of most established histories---I am curious if notes in the Kuroda papers themselves lead you to your 10% conclusion. Wilcox writes in Secret War that Nishina apparently believed, initially, that he could create an atomic bomb with uranium that was enriched to just 10%. Of course a lower degree of enrichment would have other effects, such as a much larger amount of bomb fuel being necessary and thus a much larger bomb and so on. Perhaps this is what led Nishina, according to you, to tell the military that a Japanese atomic bomb was not feasible. Lt. Col. Tatsusaburo Suzuki, among others, obviously reached a different conclusion, but let's see if you want to speak to this point. Thanks.

PS How can you say that the "Japanese bomb remained in academia" based solely on the Kuroda Papers? I assume, also, that you are not serious with your apparent assertion or at least strong inference---which follows logically from your previous statement---that the Kuroda Papers themselves are in any way the only, complete, or definitive documentation of what went on in Nishina's project, let alone in the totality of the Japanese atomic bomb effort. Are you?


You also state, if I am following you, that Nishina "needed highly enriched uranium" in order to properly calculate the "nuclear parameters". Here I am proceeding on the assumption---correct me if I am wrong---that you mean he needed to have samples (or larger amounts) of HEU in order to be able to calculate how to set off an explosion in the first place. Seems to me that Enrico Fermi, when he successfully initiated the world's first controlled nuclear chain reaction, did not need HEU, at least, not in the sense and to the extent that you are stating here. In fact, uranium oxide will suffice for at least a nuclear "pile" or reactor---the Canadians in subsequent years built a number of large and powerful "CANDU" reactors that originally used natural uranium for fuel--- and the same four factor equation Fermi used in building his pile is also used in calculating the prompt supercritical reaction found in atomic bombs. Further....


In 1941, Baron Manfred von Ardenne decided to circulate an unusual paper by his colleague Dr. Fritz Houtermans. The full title of the paper was "On the Question of the Release of Nuclear chain reactions, by Fritz G. Houtermans: A Communication from the Laboratory of Manfred Von Ardenne, Berlin-Lichterfelde-Ost." 2 The paper is remarkable in several respects, not the least for its revealing table of contents....(the third item in the table was):

III. Chain Reactions through Nuclear Fission with Fast Neutrons

The general outline suggests that Houtermans had already thought his way through the process, not only of initiating nuclear explosions via fast neutrons, but also of the transformation of U235 into higher elements not chemical identifiable with it. This is the first step toward plutonium, and to the use of plutonium rather than U235 as the explosive fuel for a bomb. The contents of the paper confirms that this is what Houtermans has figured out in no uncertain terms:

We are able to envision here an apparatus, that would allow...a certain amount of U235 to undergo nuclear reaction, simultaneously as an isotope transforming apparatus. The advantage vis-a-vis an isotope enrichment apparatus is therefore that the newly-created product, which would have an atomic number of 93 or more, is not chemically identical with uranium, and therefore is separable by chemical methods. Now since much larger amounts, namely 139 times more, of U238 are available, so the amount that would be convertible as fuel for a chain reaction is, from the standpoint of our theme, much more important than isotope separation that would result in mere U235.4

In other words, before the 1942 Heereswaffenamt memo (which not only gave a critical mass of a bomb with U235 as the explosive fuel that is within the range of accuracy, but which also indicates the transformation of uranium into plutonium in a reactor as an alternative fuel returning more bang for the Reichsmark) Houtermans has clearly seen another path to the atom bomb.

That brief section of text is from Joseph Farrell's sometimes vilified book, Reich of the Black Sun, and I quote it here because if you are right, then the obvious inference is that the Germans must have had HEU no later than 1941---something else that is supposed to have been historically impossible. It seems to me that EITHER most mainstream histories have it wrong and the Germans, at minimum, and soon the Americans, began producing true HEU as early as 1941 (1942 for the US), OR you are wrong in asserting that Nishina had to have his own HEU and couldn't have accurately calculated the "nuclear parameters" without it and thus could not have produced a working bomb design because he didn't have any (or not enough, or he had uranium that was not sufficiently enriched, etc). Obviously the Germans were able to produce very accurate calculations of the U-235 critical mass without having significant stocks of HEU, unless---again---they were actually producing the stuff earlier in the war than is generally thought. Which of course opens up an entirely new can of worms that is being discussed in other threads on this and other sites and forums.

[williamjpellas]

I have not leaped to any conclusion. All I know is that Japan never detonated an atomic bomb and that they considered a non-explosive trigger. I'm not asking how Japan DID IT (because they never did it). I'm only asking you what other techniques there MIGHT be, since you have said that Nishina's non-explosive trigger does not suggest photofission.

Was just re-reading this very lengthy thread and something jumped out at me with this post that I had not noticed or considered before. Without going into more detail than I am at liberty to do at the moment---since I have an article about this and I need to preserve some of the ahem, "secrecy" about it so I can hopefully make some money---it is alleged in some quarters that there IS a non-explosive (in the conventional sense of that term) method by which fusion bombs and possibly also fission bombs can be detonated. Yes, I said "fusion" first. I am not confusing these two terms.


So, photografr, a question for you if you are able to answer it at this point in time. Can you give more detail on what the document you viewed says and what you believe the implications to be? Can you give more detail on the non-explosive detonator that you believe Nishina and Arakatsu were discussing? Thank you.


PS Upon re-reading your post upthread in which you included the photo of Arakatsu with his cyclotron, I owe you an apology: the text included with the photo does indicate that the cyclotron was "still under construction". I think my tone with you was more strident than it needed to be, and I am sorry about that. You did try to answer the question I was asking you. My question now is, Did it still work, to a greater or lesser extent? Was it a case of basic functions being online but not the higher functions, or did the machine have to be 100% complete before it could be used at all? I ask because these things were and are massive and I am guessing that it might be possible to use the "base model" even before all of the "options" are installed! But that's just a guess.


If Arakatsu did not have access to this huge cyclotron, did he have the ability to use any of the others that existed in wartime Japan? If not, did he have access to Nishina's cross-section figures, or even to German work in the same direction?

[Genro]

Clusius-Dickel thermal-diffusion column for Uranium 235 enrichment.

Dr. Nishina. 17th November 1944.

Kyonishita U235 ganyu ritsu 0.7 % yaku 10 % tado ni naru.

Thus the U 235 which was initially 0.7%, has now been enriched to 10%.

Measurement of Thermal Diffusion and Determination of the Intermolecular Potential of Gaseous Uranium Hexafluoride.
P. Kirch and R. Schutte The J. Ch. Phy Vol.42, No 3729 – 3730 , 15 May 1965.
Column 3 m long , space 4 mm, the maximum separation factor Q -1 was found to be 4 x 10^-3 . The maximum value of Q based on molecular velocity ( 352/349 )^1/2 = 1.0043.
Thermal Diffusion Isotopic Enrichment and Radiocarbon Dating beyond 50 000 Year BP.
P. M. Grootes. Staats-U. Universitats-bibliothek Hamburg , 25th April 1977.
Diffusion theory based largely on a review of Jones and Furry 1945 and also Vasaru et. al. 1969.
To a first approximation the enrichment can be represented by :- R = Q ^n where R is the enrichment ratio, Q the enrichment factor and n is a function of the length of the column L . i.e. n =e^L .
Initial U235 0.72%, final enrichment 10% and R = 13.88. Let Lo = 3m, then the minimum length of the column is given by:- L*= Lo Ln (log13.880/log1.004 ) = 19.5 meters. Assume L* = 25 m then e^25/3 = 4160 and Q = 10^ (Log13.88)/4166 = 1.0006. The height of the Riken buildings in 1944 is estimated at about 25 meters and therefore capable of accommodating just such a separation tower.

Koregatame gasu dewa ryusoku wo chodai ni suru hitsuyo-ari jikko kon-nan nari.
Because of this, it is necessary to significantly increase the gas flow rate but in practice this is difficult to do. 6th July 1943.

Karui UF6 wo sarani joryu noshuku suru tame, bunri-to wo sarani ikki kensetsu-cho de aru.
17th November 1944
To further enrich the Uranium hexafluoride, another separating tower is in the middle of being built

[williamjpellas]

Clusius-Dickel thermal-diffusion column for Uranium 235 enrichment.

Dr. Nishina. 17th November 1944.

Kyonishita U235 ganyu ritsu 0.7 % yaku 10 % tado ni naru.

Thus the U 235 which was initially 0.7%, has now been enriched to 10%.

So you're saying that the Japanese uranium hexafluoride, gaseous thermal diffusion pilot plant at the Riken Institute actually worked? That's no surprise. Although this was of course nowhere near true industrial scale, it obviously proved that Nishina knew what he was doing and was definitely on the way to a practical, scalable method of U-235 based HEU production.

Measurement of Thermal Diffusion and Determination of the Intermolecular Potential of Gaseous Uranium Hexafluoride.
P. Kirch and R. Schutte The J. Ch. Phy Vol.42, No 3729 – 3730 , 15 May 1965.
Column 3 m long , space 4 mm, the maximum separation factor Q -1 was found to be 4 x 10^-3 . The maximum value of Q based on molecular velocity ( 352/349 )^1/2 = 1.0043.
Thermal Diffusion Isotopic Enrichment and Radiocarbon Dating beyond 50 000 Year BP.
P. M. Grootes. Staats-U. Universitats-bibliothek Hamburg , 25th April 1977.
Diffusion theory based largely on a review of Jones and Furry 1945 and also Vasaru et. al. 1969.
To a first approximation the enrichment can be represented by :- R = Q ^n where R is the enrichment ratio, Q the enrichment factor and n is a function of the length of the column L . i.e. n =e^L .
Initial U235 0.72%, final enrichment 10% and R = 13.88. Let Lo = 3m, then the minimum length of the column is given by:- L*= Lo Ln (log13.880/log1.004 ) = 19.5 meters. Assume L* = 25 m then e^25/3 = 4160 and Q = 10^ (Log13.88)/4166 = 1.0006.

The height of the Riken buildings in 1944 is estimated at about 25 meters and therefore capable of accommodating just such a separation tower.

Is the underlined and bolded part about the height of the Riken buildings your comment, Genro, or is that part of the text in the Kuroda Papers? In Secret War, Wilcox describes the extensive remodeling work the Japanese had to do in order to install the much bigger thermal diffusion separators at the building(s) at the Riken. Also, I note the presence of various scientific papers from the 1960s and 1970s in your post. I mean, I know the Japanese scientists in WWII were really good, but time travel, too?!? I'm guessing you referenced those works as being part of your own research into this topic?

Koregatame gasu dewa ryusoku wo chodai ni suru hitsuyo-ari jikko kon-nan nari.
Because of this, it is necessary to significantly increase the gas flow rate but in practice this is difficult to do. 6th July 1943.

Karui UF6 wo sarani joryu noshuku suru tame, bunri-to wo sarani ikki kensetsu-cho de aru.
17th November 1944
To further enrich the Uranium hexafluoride, another separating tower is in the middle of being built

This is probably a reference to the previously mentioned handful of much larger, much improved (far better metallurgy) thermal diffusion separators built under the supervision of Lt. Col. Tatsusaburo Suzuki in early 1945. These machines were apparently based on Nishina's basic design and were certainly based on his overall concept. Keep in mind that this effort, along with the attempt at constructing ultracentrifuges probably rooted in Professor Arakatsu's work (though possibly also influenced, if not even actually designed by, the German scientist Paul Harteck), was in keeping with a U-235, gun-type bomb project. This is not the only possible atomic weapon configuration that could have been pursued by the Japanese during WWII.

[Genro]

I should be very careful of what novelists write.
Richard Rhodes; The Making of the Atomic Bomb. P 582
“ Significantly missing from the November 17 conference report is any mention of measurable separation of U235 from U238. “

[williamjpellas]

Okay, Genro, now I'm confused. Is it "novelists" saying that 10% enrichment had been achieved, or did you post something from the Kuroda Papers (and therefore from Nishina), or what?

[steverodgers801]

If the single scientist who worked on the project had figured out a basic method of diffusion, Japan had no where any capacity to actually build and start a program. The Us spent three years and a billion dollars in developing their bombs and that was way beyond Japanese capacity. You are not talking just a few physicists, you need chemists, metallurgists and numerous other scientists , not to mention a vast amount of electricity and other materials that Japan simply didn't have. The theoretical work in developing the actual device was as difficult as any other part.

[williamjpellas]

If the single scientist who worked on the project had figured out a basic method of diffusion, Japan had no where any capacity to actually build and start a program. The Us spent three years and a billion dollars in developing their bombs and that was way beyond Japanese capacity. You are not talking just a few physicists, you need chemists, metallurgists and numerous other scientists , not to mention a vast amount of electricity and other materials that Japan simply didn't have. The theoretical work in developing the actual device was as difficult as any other part.

Seriously, Steve, if you're not going to bother reading any of the books or articles on this subject, would you please at least read through this thread before making statements that not only derail the thread, but are also---quite plainly---factually wrong? "Single scientist...(working) on the project"?? Good grief, sir, that's not even in the same universe as factually correct. Nishina, Kikuchi, Arakatsu, Suzuki, Sagane, Yukawa, Kuroda and literally dozens if not hundreds of other first rate Japanese scientists---along with, probably, a few Chinese and also, in the shadows, German---scientists were part of the various Japanese atomic bomb projects (and yes, it was projects with an "S") during WWII. Could you at least pretend to do a little homework before you post here next time? Thanks.

[Genro]

Dr. Nishina's actual words as recorded in the TONIZO report.
Correction; Kyonishita should have been written as Kayonishite

[Genro]

Atomic Bomb Mission. Investigation into Japanese Activity to Develop Atomic Power, 30th Sept.45 Summary A.3 R. R. Furman.

GHQ/SCAP TOP SECRET RECORDS IV
SYNOPSIS
On a Small Side Plant of Nishina’s
NI-Project in Osaka Imperial University

A review of a small plant of Doctor NISHINA’s NI-Project set in the Physics building at the Osaka Imperial University is reported. We could not find any Japanese official records of this plant. The personal recollection can only tell this work. In 1944 the army officer, Mr. Tatsusaburo SUZUKI had put three of Clusius-Dickel type thermal diffusion column in the Physics building with Professor Seishi KIKUCHI’s permission. Dr. NISHINA asked Dr. Tsuyoshi OKUDA for determination of separated ratio of Uranium isotopes. Dr. OKUDA planned to build a Nier-type mass spectrometer for this purpose. Mr. SUZUKI supplied sufficient financial and material support to Dr. OKUDA. The author, Shuji FUKUI, at the time a physics undergraduate was asked to work on this project together with other students of the same class. Due to then Japanese poor industrial and technical background and due to only a few collaborating scientists in NI-Project any physical result had not been progressed. Meanwhile Riken and Osaka Imperial University had lost their working activities due to American severe air raids. When Japan was defeated, almost nothing had been resulted from these projects. However, our physics students engaged to this plant had gotten big benefits of very various knowledge and experience how to prepare and how to perform physics experiments.


Foot note; On 15th August 45 the Clusius-Dickel apparatus was taken to Chikuzen-bashi and thrown into the Tosabori-gawa. ( Shuji Fukui )

[williamjpellas]

You're saying, based on what appears to be a summary from the Atomic Bomb Mission, that Project Ni installed three "Clusius-DIckel type thermal diffusion column(s)" at Osaka University. (I say "appears to be" because it looks to me like there are some typos and incorrect grammar usage in the summary and it is very unlikely that an official the caliber of Furman would have made mistakes like these, particularly in an internal government document as important and sensitive as this one. Perhaps these are your transcription errors?) These would be in addition to the original, pilot (prototype) device that Nishina was using at Riken, north of Tokyo. There were also a handful of much larger devices based on Nishina's first separator that were, IIRC, actually installed at Riken after being built under Suzuki's supervision, though these were presumably quickly destroyed in the B-29 firebombing raid(s) of March-April 1945. Although they clearly show Japanese efforts at scaling up Nishina's pilot plant, obviously these machines were nowhere near enough---compare with the Manhattan Project's S-50 thermal diffusion plant---to institute an industrial process capable of making sufficient fissile material of sufficient purity for a bomb. But that's not what Wilcox is saying. Wilcox is saying that the Japanese Army and Navy projects were amalgamated into a crash end-of-war effort at or near Hungnam, Korea, probably known as "F-NZ", and that if an end of war test detonation, as reported by David Snell, actually occurred, it was the result of the Korean branch of the Japanese nuclear project(s).