Reaching criticality is a normal goal for the operators of a controlled nuclear reactor (nuclear power reactor unit; research reactor; etc.). A reactor that has

Reaching criticality is a normal goal for the operators of a controlled nuclear reactor (nuclear power reactor unit; research reactor; etc.). A reactor that has reached criticality is usually one that is operating normally. For example: http://www.google.com/search?q=%22initial+criticality%22 http://www.google.com/search?q=%22initial+criticality%22 The JRR-4, which reached initial criticality in 1965, had contenued to aperate safely until 1996 using uranium of a high concentration of 93% [...] Unit 1 reached initial criticality on March 8, 1988 and went into commercial operation on August 25. Unit 2 reached initial criticality on March 12, ...