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ST 4.3 –
Gestión de residuos radiactivos
INVENTORY OF NEUTRON-ACTIVATED DECOMMISSIONING WASTES OF
APR1400 REACTOR IN KOREA
Lee, Kyomin*; Kang, Sangho; Lee, Seunggi
KEPCO Engineering & Construction Company Inc.
* Autor responsable, email: kyominlee@kepco-enc.com
The structural material (i.e., reactor internals, reactor vessel) surrounding the core of the reactor
have been exposed to neutron irradiation during lifetime of a nuclear facility, thereby resulting in
high concentration of activation products. Knowledge of the activation extent and level is very
important for planning of cutting, conditioning, packaging, storage and disposal as part of
decommissioning after a permanent shutdown of nuclear plants. In this study, the estimation of
the activation product inventory inside the reactor vessel was carried out based on geometry,
material composition and operating history, and the radiological characteristic for waste
classification was then assessed. The coupled transport and activation code system, the
MCNP/FISPACT coupling system, was used for source term analysis. The neutron transport
calculation for the spatial distribution of the neutron flux spectra was performed with the MCNP
code, which is capable of simulating the transport of neutron in 3-dimensional geometry with
point-wise nuclear cross-section, and the nuclide inventory calculation for the radioactive waste
clarification during decommissioning stage was performed with the FISPACT code using the
activation cross-section data in 175 group “VITAMIN-J” energy group structure. To analyze the
radiological characteristics, the specific activities of the radionuclides of interest in the activated
material, which were calculated as the function of decommissioning time, were compared with
the specified limits of the specific activities listed in the Korean standard, which have been
under revision of radioactive waste classification system with the quantitative criteria since
2013. The results showed that the components such as the baffles and barrels at the immediate
location of the core were classified as intermediate level waste (ILW) regardless of the cooling
time of the waste. It is expected that the source terms and waste classification evaluated
through this study can be widely used to establish a planning and implementation of
decommissioning/disposal strategy for APR1400 reactors.