Japan has already separated large quantities of reactor grade plutonium: https://world-nuclear.org/focus/fukushima-daiichi-accident/japan-nuclear-fuel-cycle.as

Japan has already separated large quantities of reactor grade plutonium: https://world-nuclear.org/focus/fukushima-daiichi-accident/japan-nuclear-fuel-cycle.aspx 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 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_Plutonium_and_Nuclear_Weapons-Greg-Jones_Reactor-grade-plutonium-web.pdf https://npolicy.org/wp-content/uploads/2021/06/Reactor-Grade...