Evaluation on 14C emission patterns of various PWR types in South Korea and effectiveness of inventory reduction driving (IRD)

Abstract

In this research, we investigated to examine the emission characteristics of radioactive carbon emitted from three types of pressurized water reactors. And we examined the possibility of 14C inventory reduction by changing operating conditions of one of the nuclear power plants. Results showed that 14C inventory in the reactor coolant system (RCS) remained constant before the overhaul (O/H) period and more than 90% of the radioactive carbon was found to be organic form. At spent fuel pool, the 14C chemical form of the liquid phase during the O/H period was also dominated by the inorganic (14CO2) form as in the case of the RCS due to the acid oxidized state. We applied gas stripper (G/S) and VCT purge operation to perform the 14C inventory reduction operation for Combustion Engineering type. In the case of gas strippers, approximately 50% of 14C inventory was reduced in the first year and then about 97% in the second year. Unlike our expectations, in case of VCT purge operation, 14C reduction effect was not showed greatly.