Nuclear chain reaction between being slightly subcritical and slightly delayed-supercritical, but must always remain below prompt-critical. It is impossible for a nuclear power plant to undergo a nuclear chain reaction that results in an explosion of power comparable with a nuclear weapon, but even low-powered explosions due to uncontrolled chain reactions, that would be considered "fizzles" in a bomb, may still cause considerable damage and meltdown in a reactor. For example, the Chernobyl disaster involved a runaway chain reaction but the result was a low-powered steam explosion from the relatively small release of heat, as compared with a bomb. However, the reactor complex
Nuclear power in the United States in 2005, which was still a factor of 14.6 less than the 3.5 number for all manufacturing industries. However, more than a quarter of U.S. nuclear plant operators "have failed to properly tell regulators about equipment defects that could imperil reactor safety", according to a Nuclear Regulatory Commission report. As of February 2009, the NRC requires that the design of new power plants ensures that the reactor containment would remain intact, cooling systems would continue to operate, and spent fuel pools would be protected, in the event of an aircraft crash. This is an issue that has gained attention since