For the safety of the public and the environment, radioactive gases and liquids are occasionally released from nuclear power plants under carefully controlled and monitored conditions. Radiation from these releases dissipates into the atmosphere or a significant water source, making it nearly impossible to detect any trace amounts.
In contrast, the steel and concrete structures of an operating nuclear power plant shield most of the plant's direct radiation. The rest of it dissipates in a controlled, uninhabited area surrounding the plant, ensuring that no public is harmed in the process.