Verification of Source Term Analysis System for Decommissioning Wastes From a CANDU Reactor

Abstract

There are now twenty commercial nuclear power reactors operating as of May 2010 in South Korea. As nuclear capacity becomes higher and installations age, the Korean government and industry have launched R&D to estimate appropriate decommissioning costs of power reactors. In this paper, MCNP/ORIGEN2 code system which is being developed as a source term evaluation tool was verified by comparing the estimated nuclide inventory from MCNP/ORIGEN2 simulation with the measured nuclide inventory from chemical assay in an irradiated pressure tube discharged from Wolsong Unit 1 in 1994. Equilibrium core model of Wolsoung unit 1 was used as a neutron source to activate in-core and ex-core structural components. As a result, the estimated values from the analysis system agreed with measured data within 20% difference. Therefore, it can be concluded that MCNP/ORIGEN system could be a reliable tool to estimate source terms of decommissioning wastes from CANDU reactor, although this system assumes constant flux irradiation and snapshot equilibrium core model as a reference core.

Preliminary Evaluation of Derived Concentration Guideline Level for Surface Soil at Wolsong NPP Site Using RESRAD-ONSITE Code

“…The radionuclides to be analyzed were selected using the radionuclide selection method, applied to the decommissioning of the Rancho Seco [3] and Zion [4] NPPs in the U.S., for 37 radionuclides detected in the Wolsong Unit 1 pressure tube specimens from a study on the evaluation of heavy water reactor source terms [11].…”

“…The calandria tube acts as the pressure and thermal shielding boundary between the heavy water moderator and the coolant channel, whereas the pressure tube supports the nuclear fuel at the pressure boundary and nuclear reactor core to maintain the pressure so that the coolant does not boil. The pressure tube is made of Zr alloy containing 2.5% of Nb, with a total length, inner radius, outer radius, and density of 6.4 m, 5.2 cm, 5.6 cm, and 6.6 g•cm −3 , respectively [11]. According to the Wolsong Unit 1 source term evaluation report, 37 radionuclides were derived from the preliminary evaluation of the radioactivity of the pressure tube using the ORIGEN2 code for 9 pressure tube specimens of the Wolsong Unit 1 [11].…”

“…The pressure tube is made of Zr alloy containing 2.5% of Nb, with a total length, inner radius, outer radius, and density of 6.4 m, 5.2 cm, 5.6 cm, and 6.6 g•cm −3 , respectively [11]. According to the Wolsong Unit 1 source term evaluation report, 37 radionuclides were derived from the preliminary evaluation of the radioactivity of the pressure tube using the ORIGEN2 code for 9 pressure tube specimens of the Wolsong Unit 1 [11]. When considering the License Termination Plan (LTP) of the Rancho Seco power plant, nuclides with a half-life of fewer than 2 years were excluded from the target radionuclides because their effect on the result was considered insignificant [3].…”

“…Furthermore, the sum of relative fractions of the other 10 radionuclides with a half-life of fewer than 2 years was calculated to be ca. 0.56% [11]. In this study, the 25 radionuclides with a relative fraction of less than 0.01% were excluded from evaluation owing to the small sum of their fractions, which exerts a negligible effect on the result.…”