
New evidence of Japan's effort to build atom bomb at the end of WWII - leephillips
http://www.latimes.com/world/asia/la-fg-japan-bomb-20150805-story.html#page=1
======
sandworm101
I wouldn’t use the phase "attempt to build the bomb". I wouldn't even call
this an effort.

I would label this as discussion or thought experiments. Drawing up a few
blueprints for a centrifuge is no more an attempt to build a bomb than Project
Daeidalus was an "attempt" to travel to another star. See
[https://en.wikipedia.org/wiki/Project_Daedalus](https://en.wikipedia.org/wiki/Project_Daedalus).
The amount of effort necessary to build bombs during the 40s was ridiculous.
Japan didn't have the industrial power. And I mean literal power as the
manhatten project's Oak Ridge facility used something like 1/8th of US
electricity at the time.

"Electric energy consumption, courtesy of the TVA, was 20 percent higher than
that of New York City. Oak Ridge used one-seventh of all the electricity
produced in the United States" [http://www.u-s-
history.com/pages/h1652.html](http://www.u-s-history.com/pages/h1652.html)
(not the best source, but reasonable given the context.)

I'm all for discussion of ALL history but to bring forward claims that Japan
was trying to build a bomb so close to the anniversary of its use against
Japan smacks of guilt-motivated justification. Japan's "bomb" program was of
absolutely no threat to allied forces and therefore should not be part of any
debate over the use of nuclear weapons against Japan. If anything, a Japanese
bomb program would have sucked up resources from other war efforts.

~~~
hga
Eh, the reason we spent so much effort at Oak Ridge is that we tried _all_
vaguely practical methods of getting weapons grade fissionables, and that was
the location for uranium enrichment, thermal, caltron, and gaseous diffusion.

But the most practical method turned out to be breeding plutonium and
separating it, and that was done at Hanford on a vast scale, the largest
single WWII construction project. But not inherently super electricity
intensive, the piles had to be kept cool, and ... I'm not sure anything was
all that power expensive.

Ignoring the minor detail that they had 1/166th of the uranium needed for a
Hanford style pile, assuming that 1,200 pounds was the first large quantity
the might have gotten their hands on ... well, industrially there was no way
they could have pulled this method off, we could just barely do it. They
couldn't build reliable airplane engines with > ~1,000 hp of output.

Niels Bohr dismissed the concept of A-bombs for WWII early on, he thought "you
would have to turn the county into a factory". When "Nicholas Baker" showed up
in the US, he observed we'd indeed done just that.

~~~
sandworm101
I would argue that plutonium breeding is only obvious after you have performed
some criticality experiments with an appreciable-sized block of enriched
uranium. This was new physics at the time, without computer simulations. Bomb
theory, critical mass, could only be understood after you get your hands on
some enriched uranium.

~~~
InclinedPlane
This is very much not the case. Bomb theory and critical mass come from a
fundamental understanding of neutron chain reactions. You need to have good
data on fission properties and neutron mean-free-path distances, but that
requires only extremely tiny amounts of Plutonium or natural Uranium, it does
not require enriched Uranium.

Other than that the other critical factor is coming up with the correct
model/theory for nuclear weapons. Something that the Japanese got right, the
Americans and British got right, and the Germans (specifically Heisenberg)
ended up getting extremely wrong.

Fine tuning critical mass calculations was important in optimizing the bomb
later on but it wasn't necessary to developing the basic underlying theory of
how bombs work or of pointing the way toward implosion assembly and Plutonium
breeding.

------
transfire
I am a bit skeptical of this. Not even the Germans were close to building an
atom bomb and it was their scientists that figured out the physics. If Japan
did have any real plans on the board it probably had more to do with stolen
intelligence garnered from the States.

Also, it is unlikely anyone would have realistically expected uranium to be
delivered to Japan by U-boat in 1945.

~~~
hga
_it was [ German ] scientists that figured out the physics._

Not exactly, although they contributed a lot to the early work. If we start
from "splitting the [heavy] atom", the first practical method, a German
radiochemist was the first to recognize what happened, and the German
physicist he first forwarded this information and her nephew figured out how
it worked. But those two were Jews in exile, and most of the following more
practical stuff was figured out, correctly at least, by scientists outside of
Germany. Inside, they suffered a couple of disasters, a silly failure to get
an higher priority for the project, and an incorrect evaluation of using
graphite as a moderator, limiting them to heavy water. Which we made sure
through sabotage that they couldn't get more/enough of.

But if you put on your alternate history cap, note Heisenberg and Himmer's
relationship from when they were school kids, direct all the V-2 resources
into the bomb, who knows? Many on both sides were legitimately worried the
Germans would get the bomb in time.

As for the Japanese, no way. Besides what you read in the article, thermal
diffusion was all but a failure in the US, among other things required
fantastically too much steam, and was only revived to provide somewhat
enriched feed stock into the caltrons (modified cyclotrons), and later into
the gaseous diffusion plant before it fed the caltrons. ADDED (forgotten while
drafting): centrifuges were of course obvious, and about the first thing we
tried, but were beyond the state of the art then.

1,200 pounds of uranium at the normal 0.72% U-235 would not come close to
yielding one critical mass, and for gun assembly apparently you need more like
3 times the normal pressure critical mass, although it doesn't all have to be
of the highest grade.

~~~
sandworm101
I read somewhere that after being captured by the allies some german
physicists were recorded speaking in disbelief about the bomb. They were under
the impression that any bomb would have needed many many times as much
enriched uranium (think tons) resulting in weapons too big for aircraft. That
was an indication they hadn't done much criticality research with enriched
material.

~~~
InclinedPlane
Google "Farm Hall transcripts", that's what you're thinking of.

But you're quite right. Heisenberg used an incredibly faulty method of
calculating critical mass. And everyone around him simply deferred to his
expertise. His method involved considering a branching tree of neutron chain
reactions inside a sphere of fissile material, and if this tree can grow to
include about 1 mole of material then that should be about enough to release
enough energy for a "bomb". The reality is that it's completely unnecessary
for an entire neutron chain-reaction tree to be encompassed within fissile
material. All that matters is that on average from generation to generation
there is a multiplication of neutrons, which will then grow geometrically
incredibly rapidly. And that can happen even with many "branches" of the tree
leaving the sphere and not contributing to future reactions.

~~~
paulmd
He also "proved" (incorrectly) that graphite was not an appropriate moderator.
Which ruled out bombs pretty much entirely.

In hindsight, he was actually _blatantly_ incorrect. Dude knew it was possible
and convinced the rest of the German scientists it wasn't, for long enough to
make a difference. If you read between the lines, he's almost gloating in that
transcript.

    
    
      "On the other hand the whole heavy-water business, which I did everything 
      I could to further, cannot produce an explosive."
    
      "We wouldn't have had *the moral courage* to recommend to the government
      in the spring of 1942 that they should employ 120,000 men just for
      building the thing up."
    
      "The point is that the whole structure of the relationship between
      the scientist and the state in Germany was such that although we 
      were not *100% anxious* to do it, on the other hand we were so
      little trusted by the state that *even if we had wanted to do it*, 
      it would not have been easy to get it through."
    
      "Well, that's not quite right. I would say that I was absolutely
      convinced of the possibility of our making a uranium engine,
      *but I never thought we would make a bomb, and at the bottom of
      my heart I was really glad that it was to be an engine and not a
      bomb. I must admit that*."
    

That's a Bill Gates level of finely-parsed deposition right there.

------
akilism
America is building new nukes.

[https://www.revealnews.org/article/new-mexico-thrives-on-
nuc...](https://www.revealnews.org/article/new-mexico-thrives-on-nuclear-bomb-
despite-us-pledge-to-reduce-arsenal/)

~~~
gshubert17
This article is about the warhead B61-12; the whole program is estimated to
cost about $11 billion.

This is scary, as the higher-precision guidance and adjustable lower yields
make it more likely to be used; and sad, that President Obama and the various
contractors and New Mexico politicians are pushing this.

~~~
chiph
Nuclear weapons have a definite "shelf life" because of the exotic materials
used. But if you think about things like the screws & bolts used on them -
every time a technician applies a tool to them, there's a little bit of wear
and tear. Over time, these and other parts need replacing because of ongoing
handling & routine maintenance.

The socio-political aspects are a much broader topic. Personally I don't like
them, but I realize that once Pandora's Box Of Technology has been opened,
there's no going back.

~~~
bsder
> Nuclear weapons have a definite "shelf life" because of the exotic materials
> used.

Not only that, but, because of the secrecy and security, many of the processes
for building these exotic materials have been lost.

~~~
chiph
And that the people with the direct knowledge are now 60+ years old.

~~~
dalke
Some decades ago, during discussion about test bans, the people who had
experience from blowing up 1,000+ nuclear bombs were asked if it was possible
to design a nuclear bomb that could be used by future generations that would
be sure to work without additional testing, and bearing in mind changes in
technology. Their answer was "yes".

(I think my knowledge comes from one of Freeman Dyson's accounts.)

I have not heard a clear explanation of why those earlier weapons designers
were wrong, only concerns about how they might have been wrong. That more
nebulous caution sounds identical to the sorts of statements someone might
make as a justification for designing new weapons - for some people designing
nuclear weapons and watching them go BOOM is a lot of fun.

In my very limited understanding of the topic, the largest unknown is the
changes to the plutonium-gallium alloy of the core. Some worry that it has
degraded. Others say "most plutonium pits have a credible lifetime of at least
100 years". Even if it's a problem, one solution is to re-smelt the cores,
though currently we do not have the facilities for that. However, we could
make those facilities without testing new weapons.

See
[https://en.wikipedia.org/wiki/Reliable_Replacement_Warhead](https://en.wikipedia.org/wiki/Reliable_Replacement_Warhead)
and [http://depletedcranium.com/do-our-nuclear-weapons-
work/](http://depletedcranium.com/do-our-nuclear-weapons-work/) for some of
the discussion. Also bear in mind the annoying calculus of game theory. A
higher inability to use a nuclear weapon may make it less likely to be used.

------
e12e
"The uranium seized from the German submarine ended up in the American atom
bombs"

That's what I call cruel irony. I wonder how much of a role those 1200 pounds
of ready-made u235 made for the timetable/viability of the bombs dropped on
Hiroshima/Nagasaki? A few more days/weeks and Japan would most likely have
capitalulated from the terrorcampaign of firebombings among other factors.

~~~
tsotha
Countries don't capitulate in the face of strategic bombing. They certainly
would have been willing to negotiate a peace (as most losing combatants are),
but sans nuclear weapons there would be no unconditional surrender.

~~~
e12e
Looks like we're both right: nuclear bombs are essentially strategic bombing
-- and I misremembered the reason Japan was in the process of capitulating
prior to the nuclear attacks -- but there have been a lot of discussion
indicating that Japan was indeed in the process of surrendering prior to the
attacks, see eg:

[http://www.boston.com/bostonglobe/ideas/articles/2011/08/07/...](http://www.boston.com/bostonglobe/ideas/articles/2011/08/07/why_did_japan_surrender/)

~~~
tsotha
They knew they were losing and would have been happy to conclude a peace
treaty. That's not the same thing as surrender, though.

------
hapanin
A lot of people are talking about Germany's and Japan's nuke programs being
failed wastes of resources. In retrospect this is certainly true, but the
massive benefit of a working bomb outweighed the slight chance of success. By
late 1944 it was fairly clear that both countries were going to lose the war.
Had they devoted the same resources to conventional weapons as they did the
bomb, they would have lost anyway. But they didn't know how hard it was to
build a bomb, and if it had worked, either country probably could have
negotiated a ceasefire immediately. Furthermore, Japan could have
theoretically held out a lot longer than August 1945 due to its extremely
defensible position. The only reason the Pacific War ended when it did and not
after a protracted siege or invasion of Japanese home islands was, of course,
that the US built a bomb first.

~~~
caf
"of course" is a bit too pat. Tsuyoshi Hasegawa has used Japanese sources to
argue that the Soviet invasion of Manchuria and the threat of Soviet
occupation was at least as influential in the surrender decision.

------
asanagi
Even if Japan had made a bomb in time, by 1945, they had barely any navy or
air force left to deploy it. By then, the fantastically inept IJN leadership
had squandered all their best assets in strategic blunders. The only way they
could have used the thing would be to drop it on themselves.

