MELCOR adaptation and validation for modeling of N reactor core phenomena

MELCOR has been adapted for use in modeling the N Reactor core as a part of the recently completed N Reactor probabilistic risk assessment. Significant adaptation of MELCOR was required because of the horizontal, water cooled, graphite-moderated nature of the N Reactor core. The generation and verification of the revised N Reactor core model are described in this paper. A hydrogen production and core damage benchmark calculation is presented in which all significant parameters calculated by MELCOR agreed with those in the reference calculation to within approximately 10%. The reference calculation required many CRAY CPU hours, while the MELCOR calculation was completed in less than 20 CPU minutes on a VAX 8700