The term 'Nuclear Reactor Needs' can be summarized by the crossword solution of 'COOLANTS', which refers to the substances used to cool down a nuclear reactor. Coolants are typically liquids or gases that absorb heat from the reactor core and transfer it away from the reactor, thus preventing the reactor from overheating. Coolants are essential for the safe operation of a nuclear reactor, as they help to maintain the temperature of the reactor core within acceptable limits.