원자력 발전소 핵연료 재장전을 위한 정지시 방사선준위 저감방법에 관한 연구 = A Study on the reduction method of radioactivity during shutdown for refueling outage at nuclear plant

다국어 초록 (Multilingual Abstract)

During the shutdown of a pressurized water reactor, significant amounts of activated corrosion products were released. The recent recommendations by the Electric Power Research Institute for shutdown procedures aims to remove as much radioactivity as possible from the primary system.
The Young-Gwang Nuclear Plant unit 4 performed a study to establish which conditions are reasonable to reduce the level of radioactivity in the primary system. The measurements include analysis of the reactor coolant, radioactivity in addition to boron concentration, pH, dissolved hydrogen and lithium concentration during shutdown.
From these data estimates of the relation between Co-58 activity and other chemistry parameters (such as boron concentration, pH, dissolved hydrogen, lihthium concentration) have been made. The early removal of dissoled hydorgen and elevated boron concentration at acid reducing condition could affect the Co-58 dissociation rate. At acid oxidizing condition hydrogen peroxide could affect the dissolution of Co-58 which removed from the primary system. By using the purification ion exchanger remaining Co-58 could be removed to the level which primary manways of steam generator's can be open. The activity levels of each steam generator were lowered by 35% compared with that of last year. It indicates that low pH of the system chemistry through early removal of dissolved hydrogen and elevated boron concentration at high temperature accelerated the dissolution of Co-58.