Japan has already separated large quantities of reactor grade plutonium:

https://world-nuclear.org/focus/fukushima-daiichi-accident/j...

At the end of 2018 there was 9 tonnes of separated reactor-grade plutonium (about 66% fissile) stored domestically, plus a total of 36.6 t in the UK and France. That total of 45.6 t was a modest decrease from an estimated 47.3 t at the end of 2017.

Despite the name, "weapons grade plutonium" is not actually required to make a weapon. Japan could manufacture weapons of modest yield (comparable to those used against it in World War II) on a short timeline from reactor grade plutonium if it were willing to ignore the political reaction.

See this for a relatively brief technical explanation of using reactor-grade plutonium in weapons: "Reactor-Grade Plutonium Can be Used to Make Powerful and Reliable Nuclear Weapons" https://rlg.fas.org/980826-pu.htm

This is a much longer book discussion (PDF) of the same issue: "Reactor-Grade Plutonium and Weapons: Exploding The Myths" https://npolicy.org/wp-content/uploads/2021/06/Reactor-Grade...

> Is this not a multi-year effort

If you have a strong civilian nuclear power program, the ramp up time is minimal (weeks to months), as fast breeder reactors are a dual use technology.

If the country also has a domestic space program, you can safely assume they are also working on building IRBM capabilities

I was originally gonna say that FBRs are in many places phased out (I think Japan's last one shut down in 2017) but if I'm reading right a BWR can work in a pinch, so there's -that-...

My guess with minimal knowledge in the field is, weeks if they have a shut down FBR plant, months if they have a decommed FBR Plant. I feel like building a new one to 'ramp up' would either require more time or perhaps multiple smaller reactor projects working in parallel might do the job...

Japan is restarting it's FBR program [0]

In all honesty, it feels like everyone's arming for something big - from UAE all the way to the US and China, every country is in the process of buying startups and firms working on dual use technology.

Every country seems to have some sort of a 5-10 year roadmap to modernize defense technology and logistics by 2035, yet I never saw this level of concentrated effort globally after 1989.

[0] - https://asia.nikkei.com/Business/Energy/Japan-nuclear-resear...

Side note: always appreciate (and look for) your comments in these threads.

No prob! That means a lot coming from you!!!

That said, I sincerely hope my prediction is just paranoia and that I'm wrong.

It's UAE and Saudi's deal flow that got me worried recently. I'm seeing those guys everywhere in the defense tech space now, and if Saudi and UAE are stockpiling, then every other semi-competent regional power is as well.

Saudi Arabia might have had access to nuclear weapons for a while, as part of an arrangement with Pakistan.

https://www.bbc.com/news/world-middle-east-24823846

https://en.wikipedia.org/wiki/Saudi_Arabia_and_weapons_of_ma...

It's a gentleman's agreement before Imran Khan entered the political arena.

Imran Khan leaned pro-Qatar, which irked KSA, especially because IK turned down joining Saudi's coalition in Yemen.

It was around this time that KSA began charting it's own independent course, just like UAE.

In Japan’s case, depending on what you mean they’ve already got IRBM (indeed, ICBM) capabilities. Their space industry has been building capable solid fuel boosters for a couple of decades.

I assume they haven’t actually tested a precision guided reentry vehicle, but that’s all they’re missing on the missile side.

There's one in Rokkasho-mura in Aomori, ~20mi from USFJ/JSDF Misawa AB. Not officially complete, whatever that's supposed to mean.