Abstract
In order to expand our understanding of the characteristics of radioactive effluent from nuclear power plants under decommissioning, which have not been systematically investigated, a series of source term models of radioactive effluent after permanent shutdown has been established based upon theoretical reasoning on the design and operation features of plants and derived in terms of fifteen arguments. Comprehensive radioactive effluent data have been collected and profiled from twenty-eight decommissioning pressurized water reactors, and annual trends of effluent from each plant have been quantitatively analyzed using Mann-Kendall statistical test. In addition, the characteristics of collected effluent data have been qualitatively interpreted based upon arguments newly proposed in this study. Furthermore, potential decreasing of dilution factor for liquid effluent and its safety implications are identified. The source term models and verified characteristics of radioactive effluent after permanent shutdown developed in this study can be used for establishing more efficient discharge monitoring program for decommissioning authorization.
Highlights
It is reported that 53 pressurized water reactor (PWR) units have been permanently shut down among the 172 nuclear power plant (NPP) units that ceased operations as of 31 December2018, and additional NPPs have ceased operation every year since and the cumulative number of permanently shut down NPPs is expected to continually increase in the future [1,2].Radioactive materials in airborne and liquid effluent are released to the environment from NPPs, and the radioactivity in discharged materials is reported to the corresponding regulatory authority for each radionuclide (RN) or RNs groups [3,4,5]
Based upon the above review, this study aims at more comprehensive understanding of the radioactive discharge characteristics after permanent shutdown (PS), which could be a robust technical basis for effective radioactive effluent monitoring program at decommissioning NPPs
A series of source term models of radioactive effluent after PS has been established based upon eight compartments and potential release paths representing an NPP after PS
Summary
It is reported that 53 pressurized water reactor (PWR) units have been permanently shut down among the 172 nuclear power plant (NPP) units that ceased operations as of 31 December. Radioactive materials in airborne and liquid effluent are released to the environment from NPPs, and the radioactivity in discharged materials is reported to the corresponding regulatory authority for each radionuclide (RN) or RNs groups [3,4,5]. It is noted that the radioactive effluent is released to the environment from NPPs during operation, but after permanent shutdown (PS) as well and even during decommissioning until license termination (LT) [7].
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