Potential impacts to operating nuclear power plants due to application of revised source term

TID-14844 was promulgated in 1962, and more than 30 years later there has b een a big change of the US NRC's regulatory position in using accident sour ce term for radiological assessment following a design basis accident (DBA) . To replace the instantaneous source term of TID-14844, the time-dependent source term of NUREG-1465 was introduced in 1995, which represents the acc ident source term enveloping all light water reactor plants. In the meantim e, the radiological acceptance criteria for reactor site evaluation in 10 C FR Part 100 were also revised. In particular, the concept of a total effect ive dose equivalent (TEDE) has been incorporated in accordance with the rad iation protection standards set forth in revised 10 CFR Part 20. Subsequent ly, the publication of Regulatory Guide 1.183 and the revision of the Stand ard Review Plan 15.0.1 followed in 2000, which provided the licensee of a o perating nuclear power reactor with the acceptable guidance of applying the revised source term. The guidance allowed the holder of an operating licen se issued prior to 10 January 1997 to voluntarily revise the accident sourc e term used in the radiological consequence analyses of DBA. Depending on i ts type of application, there were suggested full and selective application s. Whether it is full or selective, based upon the scope and nature of asso ciated plant modifications being proposed, the actual application of the re vised source term to an operating plant is expected to give a large impact on its facility design basis. Prior to its actual implementation of design modifications, it is necessary to identify and analyze the potential impact s of each type of application and to derive the considerations taken in eac h application. In this paper, the experiences and lessons learned from its application to Ulchin Unit 3&4 are evaluated and presented. (C) 2001 Publis hed by Elsevier Science Ltd.