[leonidasrup]

In the US reprocessing of civilian nuclear waste was stopped not for technical reasons, but for political reasons. The primary reasoning was that: US reprocessing of civilian nuclear waste would encourage other non-nuclear weapon states to build nuclear reprocessing capabilities which would make easier access to plutonium - nuclear weapon material.

"On April 7, 1977, President Jimmy Carter announced that the United States would defer indefinitely the reprocessing of spent nuclear reactor fuel. He stated that after extensive examination of the issues, he had reached the conclusion that this action was necessary to reduce the serious threat of nuclear weapons proliferation, and that by setting this example, the U. S. would encourage other nations to follow its lead."

https://www.pbs.org/wgbh/pages/frontline/shows/reaction/read...

Commercial fusion reactors could be used burn (transmutate) long-term transuranic waste, on the other hand they will produce short-term nuclear waste, like neutron activated steels.

[cyberax]

Yeah. My former coworker was researching ways to make steel less "activatable". Turns out that the most problematic contaminant is niobium, so he was working on possible ways to remove it completely.

The proliferation risk was real at that time, but it's now a moot point. The details of plutonium refining are well known.

[leonidasrup]

Principles of plutonium separation are well known (https://en.wikipedia.org/wiki/PUREX), but preventing non-nuclear weapon states from having access to nuclear materials usable for nuclear weapons (Plutonium, Highly enriched uranium) is still cornerstone of US foreign policy. See the current events in Iran. Or the discussions with South Korea:

"The U.S. State Department did not give specific responses when asked if the U.S. was open to changing the agreement and what sort of discussions it had agreed to, but a spokesperson said: "America has a longstanding policy to limit the spread of enrichment and reprocessing capabilities around the world and to seek the highest nonproliferation standards achievable in all 123 agreements.""

https://www.reuters.com/business/energy/south-korea-us-agree...

This also the reason for monitoring and inspections by International Atomic Energy Agency in all facilities handling nuclear materials (nuclear reactors, fuel manufacturing, nuclear waste storage) or capable of producing nuclear materials - in non-nuclear weapon states.

https://www.iaea.org/topics/additional-protocol