in 20.5.1,after the reaction finishes,if I add new nuclear fuel into the reactor,the reaction will not start.When I destory some blocks and recover them,the reaction starts.I'm not sure if something is wrong.

Are you using the samw fuel again, or a different one? Are you waiting a long time before adding fuel again? What fuel and design are you using?

In the old version the reactor can work correctly,it's designed for [NI]HEU-235.After the words turned yellow the reactor still couldn't work.After destorying some blocks and replacing them it may work,but this sometimes doesn't work.

Is the flux the cells are receiving close to the criticality factor? If so, it might be that your reactor is currently neutron poisoned (added in the most recent major version).

If it is the cause,I advice to make it visual to see if the reactor is neutron positioned and provide ways to solve it.

Maybe translating made the tune stronger,I'sorry about it.

You’re definitely right, and neutron poisoning and other important starts will eventually be displayable by fission monitors, but they’re not implemented yet.