Modeling of Radionuclide Releases From the Geological Repository for RBMK-1500 Spent Nuclear Fuel in Crystalline Rocks in Lithuania

Abstract

During 2002–2005 the assessment of possibilities for disposal of spent nuclear fuel (SNF) in Lithuania was performed with support of Swedish experts. Potential geological formations for disposal of SNF were selected, disposal concept was developed, reference disposal site was defined and preliminary generic safety assessment was performed. Performing safety assessment the analysis of radionuclides migration from the repository as well as their impact to human and environment were also very important issues. In this paper results on the analysis of the radionuclide releases from the reference geological repository site for RBMK-1500 SNF in crystalline rocks in Lithuania are presented. For radionuclide migration in the near field region of the repository integrated finite difference method and the concept of compartments were used. For radionuclide migration in the far field the discrete channel network concept was used. The assessment of radionuclide migration in the near and far field region was performed using computer codes AMRER4.5 [1] and CHAN3D [2]. The results of analysis show that most of safety relevant radionuclides of RBMK-1500 SNF are effectively retarded in the near field region. The exposure due to possible release of the radionuclides from the crystalline rocks would be dominated by 129I firstly while after app. 250 thousand years 226Ra is dominating already.

Uncertainty and sensitivity analysis of radionuclide migration through the engineered barriers of deep geological repository: Case of RBMK-1500 SNF

“…Based on the preliminary assessment, the reference canister would be of 1050 mm diameter and 4070 mm length. For Lithuanian SNF disposal purposes about 1400 canisters should be employed [13]. In this study the engineered barriers comprising the near field are being considered (SNF matrix itself, disposal canister, surrounding bentonite layer).…”

“…Preliminary studies on the radionuclide transport through the engineered and natural barriers of the conceptual repository for RBMK-1500 SNF were performed and presented in [10], [11], [12]. Considering the mass flux and radionuclide radiotoxicity, it was observed that radionuclides 129 I and 226 Ra (in the long-term) are the dominant radionuclides in the release from the engineered barriers.…”

Pažanga įgyvendinant radioaktyviųjų atliekų atliekynus Lietuvoje ir jų saugos vertinimas

“…Analizuojant PBK šalinimo Lietuvoje galimybes, atliktas giluminio atliekyno įrengimo kristalinėse uolienose išlaidų įvertinimas bei pradėtas bendrasis atliekyno saugos vertinimas [30]. Tęsdami saugos vertinimus, LEI Branduolinės inžinerijos problemų laboratorijos mokslininkai analizavo atliekyno evoliucijos scenarijus, atliekyno aplinkoje išliekant dabartinėms sąly-goms, joms keičiantis, esant nesandariam vienam iš šalinimo konteinerių, įvertinta įvairių veiksnių įtaka radionuklidų [31][32][33][34][35][36][37] ir dujų [38][39][40] sklaidai bei tarpusavyje susijusių šilumos mainų (T), fluidų (dujų ir vandens) pernašos (H) ir mechaninių procesų (M) įtaka atliekyno saugai [41][42][43][44]. Geologijos ir geografijos instituto tyrėjai vykdė požeminio vandens tekėjimo ir radionuklidų sklaidos iš PBK atliekyno kristalinėse uolienose pietrytinėje Lietuvos dalyje skaitinius vertinimus [45][46][47].…”

“…Darbe [32] nagrinėta radionuklidų sklaida iš Lietuvos PBK atliekyno kristalinėse uolienose, esant vertikaliam ir horizontaliam konteinerio patalpinimo būdui. Gauti rezultatai parodė, kad abiem atvejais daugelis saugos požiūriu svarbių radionuklidų yra efektyviai sulaikomi inžineri-niuose barjeruose ir skirtumai dėl konteinerio patalpinimo būdo yra nežymūs.…”

Uncertainty and Sensitivity Analysis at Low Value of Determination Coefficient of Regression Analysis: Case of I-129 Release from RBMK-1500 SNF under Disposal Conditions

“…Up to now, not much research has been done on RBMK type SNF behavior under deep geological repository (DGR) conditions, the potential for contaminant migration, and the subsequent impact on humans and the environment. Some deterministic assessment results were published in [17][18][19]. Radionuclides I-129 and Ra-226 (in the long-term perspective) were identified as dominating the mass flux and radiotoxicity flux from the engineered barrier system (EBS) of DGR under the canister defect scenario.…”