Question

Since we started producing nuclear power in 1960, how common are large nuclear accidents (those that resulted in the major release of radioactive material into the environment)?

Answer 1

Very, very rare. Uranium used in power plants is typically only 3% U-235 (the explosive stuff), while bomb-grade uranium is nearly pure U-235. Simply, the concentration of U-235 in reactor-grade uranium is too small to start a chain reaction and detonate like a bomb.