title: Modeling of irradiated graphite (14)C transfer through engineered barriers of a generic geological repository in crystalline rocks.
abstract: There are two RBMK-1500 type graphite moderated reactors at the Ignalina nuclear power plant in Lithuania, and they are under decommissioning now. The graphite cannot be disposed of in a near surface repository, because of large amounts of (14)C. Therefore, disposal of the graphite in a geological repository is a reasonable solution. This study presents evaluation of the (14)C transfer by the groundwater pathway into the geosphere from the irradiated graphite in a generic geological repository in crystalline rocks and demonstration of the role of the different components of the engineered barrier system by performing local sensitivity analysis. The speciation of the released (14)C into organic and inorganic compounds as well as the most recent information on (14)C source term was taken into account. Two alternatives were considered in the analysis: disposal of graphite in containers with encapsulant and without it. It was evaluated that the maximal fractional flux of inorganic (14)C into the geosphere can vary from 10(-11)y(-1) (for non-encapsulated graphite) to 10(-12)y(-1) (for encapsulated graphite) while of organic (14)C it was about 10(-3)y(-1) of its inventory. Such difference demonstrates that investigations on the (14)C inventory and chemical form in which it is released are especially important. The parameter with the highest influence on the maximal flux into the geosphere for inorganic (14)C transfer was the sorption coefficient in the backfill and for organic (14)C transfer - the backfill hydraulic conductivity.
authors.affiliation: Nuclear Engineering Laboratory, Lithuanian Energy Institute, Breslaujos st. 3, LT-44403 Kaunas, Lithuania.
authors.forename: Povilas
authors.initials: P
authors.lastname: Poskas
authors.affiliation: Nuclear Engineering Laboratory, Lithuanian Energy Institute, Breslaujos st. 3, LT-44403 Kaunas, Lithuania. Electronic address: Dalia.Grigaliuniene@lei.lt.
authors.forename: Dalia
authors.initials: D
authors.lastname: Grigaliuniene
authors.affiliation: Nuclear Engineering Laboratory, Lithuanian Energy Institute, Breslaujos st. 3, LT-44403 Kaunas, Lithuania.
authors.forename: Asta
authors.initials: A
authors.lastname: Narkuniene
authors.affiliation: Nuclear Engineering Laboratory, Lithuanian Energy Institute, Breslaujos st. 3, LT-44403 Kaunas, Lithuania.
authors.forename: Raimondas
authors.initials: R
authors.lastname: Kilda
authors.affiliation: Nuclear Engineering Laboratory, Lithuanian Energy Institute, Breslaujos st. 3, LT-44403 Kaunas, Lithuania.
authors.forename: Darius
authors.initials: D
authors.lastname: Justinavicius
mesh_terms: D002250:Carbon Radioisotopes / Q000032:analysis; D019015:Geologic Sediments / Q000032:analysis; D006108:Graphite / Q000032:analysis*; D060587:Groundwater / Q000032:analysis*; D008097:Lithuania; D008956:Models, Chemical; D055848:Nuclear Power Plants; D011834:Radiation Monitoring; D011850:Radioactive Waste / Q000032:analysis*; D064091:Waste Disposal Facilities
chemical_list: D002250:Carbon Radioisotopes; D011850:Radioactive Waste; D006108:Graphite; C000615234:Carbon-14
keywords: DGR; Near-field environment; RBMK-1500 reactor; Radiocarbon flux; Tornado diagram