Why is the cost of nuclear power so high?

While actually achieving a nuclear fission reaction is (relatively) easy, a lot of the cost comes from making the whole process safer. We want to create a controlled reaction, and we want to be able to control the reaction in a way that does not harm people. The best way to do this is to build machines that control all the fission reactor components remotely, you need to invest in radiation shielding and failsafes, you need to have procedures and staff that can handle an accident or a part of the reactor breaking. A lot of the cost of nuclear power is the cost of the facility itself, the highly trained staff, and waste management.