Evaluation of operation reliability of fast power reactor cores

The reliability analysis of the fast reactor core has a feedback effect on fast reactor optimization calculations. The melting temperature of oxide fuel is the critical variable for fuel calculations viewed from the reliability angle. The actual temperature deviations from the calculated rated values have a systematic and a static character, which also determines the interrelation between the reliable operation criteria and the methods of calculations. The criteria are formulated on the probability basis; e.g., it is envisaged that there is high probability (more than 0.999) that the temperature on the site of the maximal rated temperature will not exceed the critical temperature, the occurence is accepted of a certain maximal permissible number of failures, etc. This permits decreasing the degree of the conservative nature of a reactor design with regard to economic requirements. A system of programmes comprising this approach to the reliability analysis of the core was written and verification calculations were effected for a hypothetical core and for the BN-600 type core. (Z.M.)