Fast neutron exposure calculations for the surveillance capsules of a boiling water reactor

The aim of any reactor pressure vessel (RPV) surveillance program is to monitor the neutron-induced material degradation of the RPV wall and to provide data periodically for adjustment of certain operational parameters to ensure continued safe operation. Surveillance capsules are usually installed in nuclear power plants prior to startup so that they attain higher fast fluence exposure than that of the RPV wall peak position. This paper calculates the surveillance capsule lead or lag factor for a currently operating boiling water reactor (BWR) (designated as REACTOR-B) using two neutron cross-section libraries (SAILOR and ELXSIR). In addition, the total displacement per atom (dpa) through the pressure vessel wall is compared with that of the fast flux and with the attenuation functions given in US Nuclear Regulatory Commission Guide 1.99, Revs. 1 and 2. A detailed synthesized three-dimensional transport analysis was performed and American Society for Testing and Materials standards were followed to the extent practical