Even leaving aside the question of how much insurance should be required and how to underwrite that, as well as what kind of reserve should be mandated for cleanup and long term waste storage, the economics of nuclear are very rough.
The lion's share of the costs are upfront and the break even period is measured in decades. What is the energy landscape going to look like in 30 years? That's a question that you need to be able to answer with high confidence if you want to correctly price bonds that will be used to construct a nuclear power plant to be paid off from the revenue of the plant. If the potential bond buyers can't answer that question with high confidence then they don't know what interest rate is appropriate for the bonds and they probably won't want to buy them.
The lion's share of the costs are upfront and the break even period is measured in decades. What is the energy landscape going to look like in 30 years? That's a question that you need to be able to answer with high confidence if you want to correctly price bonds that will be used to construct a nuclear power plant to be paid off from the revenue of the plant. If the potential bond buyers can't answer that question with high confidence then they don't know what interest rate is appropriate for the bonds and they probably won't want to buy them.