prompt critical

Adjective

prompt critical (not comparable)

1. (nuclear physics) In a state where the prompt neutrons produced by a nuclear fission chain reaction are just sufficient to sustain the chain reaction on their own (past which changes in reaction power occur on a timeframe of milliseconds, too rapidly for a human operator to control).
   • The number of fissions in the two prompt critical excursions was estimated from (1) the doses received by the operator and shift supervisor and (2) the measured exposure rate from fission product gamma–rays (1.5 mR/s at 3 m from the vessel, 1 hour after the last excursion).2000, Thomas P. McLaughlin with Shean P. Monahan, Norman L. Pruvost, Vladimir V. Frolov, Boris G. Ryazanov, and Victor I. Sviridov, “I. A. 17. Mayak Production Association, 10 December 1968”, in A...