Civilian plutonium is unsuitable for nuclear weapons. Unless China has found a way to separate Pu-239 from Pu-240 and the rest of the junk, that stockpile is useless. Now, it might well be possible or even feasible to do this - there are proposed technologies like laser isotope separation - but such technologies are very closely guarded state secrets. We haven't seen any demonstration of plutonium isotope separation, so we can't blithely assume that China (or anyone else) has this technology."Concerns grow over China nuclear reactors shrouded in mystery | Nuclear Energy News | Al Jazeera"
The reason these breeder reactors are shrouded in mystery is that China, which had been transparent about its civilian plutonium programme until recently, stopped annual voluntary declarations to the International Atomic Energy Agency [IAEA] on its stocks of civilian plutonium in 2017 and has not added the reactors to the agency’s database to date.
That China stopped declaring that stockpile is at best very weak evidence that it intends to use it in weapons in some way.