Passive ALWR source term

The purpose of this report is to provide technical support for the physically-based source term which is proposed as the licensing design basis fission product release from a major core accident for the Passive Advanced Light Water Reactor (ALWR) in Volume 3, Section 5 of the ALWR Requirements Document. A substantial body of new research motivated by the Three Mile Island (TMI) accident is maturing, and the ALWR Requirements Document provides an opportunity to incorporate this experience in an updated source term. This update will provide a more rational basis for Passive ALWR accident mitigation system designs, particularly where the designs afford opportunities for improvement and innovation. Great attention has been paid to accident prevention in the ALWR Requirements Document which will reduce the likelihood of core damage by an order of magnitude or more compared to earlier LWR designs. Nonetheless, for defense-in-depth the Passive ALWR source term is based on evaluation of a core damage event. Selection of this core damage event and the associated quantification of the fission product release were done in a conservative, yet physically-based manner so as to provide significant margin to the expected releases, given an ALWR accident, while avoiding non-physical assumptions which could produce mitigation system designs not well-suited to the important accidents. The physically-based source term presented in this report is intended for use in ALWR design basis analysis defining the radiological environment for plant systems and equipment and evaluating the offsite dose for emergency planning considerations. 100 refs., 18 figs., 44 tabs