Antonyms for the words "Nuclear Reactor Accident" include safety, stability, control, prevention, and security. A nuclear reactor accident is a catastrophic event, which can lead to serious negative consequences, including contamination of the environment and human health risks. Safety measures are put in place to prevent such accidents, and the proper functioning of the nuclear reactor is ensured through periodic maintenance and control measures. Stability in the nuclear power plant is maintained through proper system design and trained personnel. Prevention of accidents is ensured by following safety protocols and maintaining a high level of security. In summary, the opposite of a nuclear reactor accident is to have safety, stability, control, prevention, and security in place.