Abstract

The strategy of radioactive waste management of Lithuania provides for evaluating the possibilities of disposal of spent nuclear fuel and long‐lived radioactive waste originated from Ignalina NPP in deep geological formations. The initial studies performed in Lithuania during 2001–2004 focused on screening of all potentially prospective geological formations as host formations. Since most information is available on crystalline basement, this formation was selected for the model case studies. Taking into account the assumptions (canister defect scenario proposed by Swedish experts and evaluated by LEI experts), groundwater flow and radionuclide (iodine‐129 as mobile and long‐lived one) transport modelling using computer code FEFLOW was performed according to geosphere conditions and parameters characteristic of the southern part of Lithuania (0,8×0,6×0,52 km far‐field block). The upward groundwater flow through defected canister located in tectonically damaged zone was simulated. The main results of calculations are the following: in the case of upward groundwater flow, the maximum I‐129 volumetric activity in single tectonic fracture above defected canister will not exceed 1 Bq/1, and in the active water exchange zone, it is close to 10−2 Bq/l. These figures show that doses obtained by human recipient via aquatic pathway should be below the dose constraint (0,2 mSv/y). More complicated scenarios and assumptions should be investigated in future studies.

Highlights

  • During the operation of Ignalina NPP spent nuclear fuel (SNF) is produced

  • Since most information regarding deep geological formation in Lithuania is available on crystalline basement, this formation was selected for the model case studies [4,5,6]

  • On the basis of canister defect scenario evaluated by LEI experts, groundwater flow and radionuclide transport modelling, using computer code FEFLOW, was performed in this particular study for geosphere conditions prevailing in the southern part of Lithuania

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Summary

Introduction

Since the beginning of Ignalina NPP operation in 1983, all SNF and operational radioactive waste have been stored at the NPP site. Several alternatives related to safe management and disposing of SNF are being analyzed for the future They are a possibility of having a deep geological repository for SNF and long-lived radioactive waste in any SNFgenerating country, the possibilities of constructing a regional repository by joint efforts of several countries that generate or do not SNF, the possibilities of disposing of SNF in other countries, and the possibilities of extending the storage period in an interim storage for up to 100 and more years. There is an international consensus that high-level and long-lived radioactive waste, first of all SNF, is best disposed of in deep geological repositories using a system of engineered and natural barriers [3]. On the basis of canister defect scenario evaluated by LEI experts, groundwater flow and radionuclide (iodine129 as mobile and long-lived one) transport modelling, using computer code FEFLOW, was performed in this particular study for geosphere conditions prevailing in the southern part of Lithuania

Outline of the problem of spent nuclear fuel
Hydrogeological setting
Conceptual model
Proterozoic- Weathered
Computer code and numerical model
Model calibration and sensitivity analyses
II III IV V
Spatial distribution of contamination plume
Conclusions
IAEA Deep Underground Disposal of Radioactive Waste

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