First it requires 10x as much energy to slow down something in orbit until it falls into the sun.

It's honestly a non-issue as there's no reason not to use highly enriched U235/Plutonium fueled reactors like are used on U.S. Navy subs and carriers. They literally go 50+ years with no need for refueling/recycling installed fuel.

It's not like anyone is going to fly up to the moon and steal it lol.