I’ve usually taken it as common wisdom that Japan, if it suddenly wanted to, could build a nuclear bomb in about 6 months. Articles and experts have quoted this figure.

However, there are reports quoting the Japanese newspaper Sankei of an internal Japanese report that puts the estimate closer to 3-5 years. The Japanese government denies the existance of this study:

The Japanese daily Sankei reported that experts at several government organizations concluded it would take at least three to five years to make a prototype weapon.

The experts also estimated that the project would cost about $1.68 billion to $2.52 billion and require the efforts of several hundred engineers, according to Sankei.

The experts did not say whether Japan should develop nuclear arms, the newspaper reported, only what such a project would require. The newspaper published a summary of the document, dated Sept 20 and titled “On the Possibility of Developing Nuclear Weapons Domestically.”

[Do any Japanese readers of ACW, or those with FBIS access, want to take a look for the original report and send us links or a translation if FBIS has it?]

I don’t know, this all sounds a bit odd to me. I am not sure where the 6 months claim originaly came from, and it does seem a bit fast now that I think about it. Maybe it comes from trying to put some numbers to as ‘little as a year’s time’ or maybe from a Septermber 2005 Forbes article which, as far as I can tell, first referenced a Japanese official saying that, it would take 183 days. (Exactly. On the dot. not 182 or 184…. what?!)

But 3-5 years? Why would it take a country with plenty of fissile material, reprocessing techonology, an advanced nuclear science establishment and a healthy economy, 5 years to build a prototype nuclear device? Some are worried that Iran could do it in 5, and they have nowhere close to the capablities and materials access of Japan. With a full industrial commitment, the US and Russia both did it in about 4 years starting from scratch. South Africa began working on a bomb design in 1971, with more intense work starting in 1974 and were ready for a “cold test” (without HEU) in 1977.

Two billion dollars is a lot of money, it is probably not something that would be a limiting factor if Japan wanted a bomb. Also, Japan gets about 35% of its electricity from 55 reactors. Would finding several hundred engineers be much of an effort? A few points of comparison: construction of the Rokkasho-mura reprocessing plant cost about 20 billion and employed 5,000 people.

ITAR-TASS says said that the difficulty in mobilizing the man power would be a moral issue rather than a techinical one: [I was emailed this article, so still looking for a link.]

The authors of the report said Japan possesses enough plutonium to manufacture thousands of warheads but such a project would have to mobilize several hundreds of engineers.

The latter will not be an easy task since the overwhelming majority of Japanese nuclear physicists are against turning their country into a nuclear power, an informed expert told Tass.

—Moscow ITAR-TASS in English 0148 GMT 25 Dec 06

Sure the physicists do not want to make weapons now, but that position is consistant with general public opinion in Japan. If public views were to shift – which would be a major change, but according to some experts, may be possible – I can imagine that the opinions of the scientific community would be just as likely to shift along with other Japanese citizens.