system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the waste produced in a thorium fuel cycle need storage for only 300 years instead of thousands of years for uranium fuel cycle, even though U233 from Th232 had mostly similar fission products as U235?
gpt
This argument is mainly about transuranic isotopes. These are waste products which through neutron capture become heavier. They do not fission at all. To go from U238 to P239 all you need is one capture. To go from U233 to P239, you need a series of captures and there will be plenty of opportunity for fission instead of capture and less transuranic elements will be bred from Thorium.

The fission products are indeed very similar in composition. One notable exception with liquid fuel reactors is that xenon will not be transmuted in the reactor core (as a gas it will bubble out). In that case you get a lot more Cs135 which has a half life of 2.3Ma. But mostly the fission products are essentially the same.

Fission products are either very short lived and those are not a problem, or they are medium lived (10-100years half life) and those are a problem, or they are long lived and those are not that much of a problem (they have low radioactivity).

P239 has a half life of 20000 years and that means it is pretty radioactive and also pretty long lived. Also when P239 decays, it will go through a long chain of maybe a dozen decays before it becomes stable, whereas fission products usually become stable after a single decay.