Because of the design? None. In fact the Canadian-designed SLOWPOKE reactor (https://en.m.wikipedia.org/wiki/SLOWPOKE_reactor https://en.m.wikipedia.org/wiki/SL

Because of the design? None. In fact the Canadian-designed SLOWPOKE reactor (https://en.m.wikipedia.org/wiki/SLOWPOKE_reactor https://en.m.wikipedia.org/wiki/SLOWPOKE_reactor) is licensed to run unattended overnight - it is only passively cooled and increased temperature results in a negative feedback loop. An unpressurised light water reactor is an inherently safe design. The rate of reaction depends on liquid water being present, steam will stop the reaction. Nuclear power doesn't have to be dangerous, and even now more people die due to coal power (including mining and pollution effects) each year than ever have due to nuclear power.