Radwaste in Granitoid Blocks
Geoecological Forecast of HLW Long-Term Isolation in Granitoid Blocks of the Nizhnekanskiy Massif (South-Yenisei Ridge)
Tech Area / Field
- ENV-RWT/Radioactive Waste Treatment/Environment
- OBS-GEO/Geology/Other Basic Sciences
3 Approved without Funding
Khlopin Radium Institute, Russia, St Petersburg
- Lawrence Livermore National Laboratory, USA, CA, Livermore\nDeutsche Gesellschaft zum Bau und Betrieb von Endlagern für Abfastoffe mbH (DBE), Germany, Peine
Project summaryKey goal of the Project is the elaboration of scientifically substantiated forecast of HLW isolation geotechnological system stability and an assessment of long-lived radionuclides migration from this system over a long period of time – 100 thousand of years and more. Substantiation of the Nizhnekanskiy massif selection as the inclosing rock and results of its investigations are set forth consistently in ISTC 0255 (1995-1998) and 1491 (2001-2004) Projects executed by the same team as in the Project proposed.
The goal of the ISTC 0255 project, that is the evaluation of geological formations of the South Yenisei Ridge, have been attained. For the first time in Russia, the large granite massif perspective for disposal of wide range of radioactive waste (including HLW and spent fuel) has been discovered in the Central Siberia. This allowed to concentrate the following researches in the northern part of the massif.
Based on the results of the complex geology-geophysical studies, involving borehole drilling, the following ISTC 1491 Project have revealed two perspective sites of 15-20 km2 on the northern part of the Nizhnekansky massif. Monolith granite blocks discovered in the sites have been recommended for the further pre-project works and construction of underground research laboratory.
The Project proposed is a logic sequel of the two finished projects and will be done by the same team. It will continue the complex investigations aimed to obtain a basic knowledge on geology, tectonic, hydrogeology, geochemistry and petrology-mineralogical properties of the rocks on the discovered sites. The information obtained will make a basis for the geoecological forecast. The works proposed in the Project will coordinate with the plan on creation of radioactive waste repository in the Niznekansky massif designed in ISTC 2377 Project of VNIPIET (leader Gupalo T.A.) and optimized programs of the engineering-geological studies of the perspective sites. The collaboration implies that the proposed studies will be correlated with the designed plan of the 2377 Project and the involvement of VNIPIET team in the proposed investigations. The results obtained will be used in design works. At the same time, the specific feature of the proposed Project is to provide the scientific ground for the long-time geological-tectonic and climatic forecast for the territory occupied by the Nizhnekansky massif.
Development of the long-time geoecological forecast is a separate orientation of science based on the analysis of all the information obtained and the key features of the evolution of the lithosphere and natural phenomena. The major requirement for the forecast is its scientific validity permeating to use the results not only for total estimation of underground isolation safety, but for every distinct stage of the creation of an underground repository (assessment environment impact, pre-project and design works, ecological expertise, etc.).
The existing uncertainty of long-term forecast is an obstacle for final nuclear fuel cycle realization, that is, for HLW underground isolation. The Project separates two types of the underground waste isolation: the storage (300-500 years) and disposal (several hundred thousands years). These two types differ not only by a required period of isolation, but also by requirements for the safety forecasts.
Multibarrier protecting system, the suitability of the host rock to the specific selection criteria and active monitoring ensure safety storage of radioactive materials (irradiated nuclear fuel (INF), as well as of irradiated fuel assemblies (IFA), which are not to be reprocessed, et al.) during initial hundreds of years. In this case the major goal of the forecast is to substantiate the preservation of isolating properties of engineering barriers and to evaluate their possible transformations with the time.
Because of isolation necessity for still long-term periods – 100 thousand of years and more – the priority of safety insurance is transferred to geological formation hosting technogenic. Key problems of safe disposal of HLW ("disposition") are: tectonic stability of the region and a migration behavior of radionuclides in the rocks hosting the repository. A time factor separate two major facility for safe underground isolation of HLW: engineering barriers during the storage and natural geochemical barriers during the disposal. However, if underground objects are complex, that is, an underground research laboratory (URL), a storage facility and a repository are designed at a specific geological site, their interrelation and designing sequence is evident.
In the Project proposed, features and interrelations of principal safety insurance factors in radioactive materials storage (disposition) and disposal (removal) are being considered as applied to the Nizhnekanskiy massif's conditions.
Three interconnected scientific fields are selected to design a long-term geoecological forecast. These are: geologic-tectonic, climatic and migration-ecological.
Long-term forecast will require:
- the knowledge on the basic properties and features of development of selected segment of continental crust, features of its evolution in the past and its present day state and development; main features of climatic changes; migration and barrier behavior of the rocks, etc.;
- foreign and international programs' expertise in natural tests carried out in underground laboratories for similar geological formations;
- accumulated comprehensive information, characterizing the Nizhnekanskiy massif as a geological environment for HLW long-term isolation;
- a use of natural and natural-technogenous analogues;
- a use of optimal methodology and methods to study the state and interrelation of natural, natural-technogenous processes during the time (integrational, deterministic, probability analysis).
The increase of forecasting period (more than 100 thousand years) leads to a higher uncertainty in the forecasted events as well as that of complex geotechnological systems state and their ecological danger in remote future. Solution of long-term forecast problem is most correct in the range of natural collisions manifestation probability, as these collisions influence negatively to a safety of long-lived radionuclides' underground isolation.
Project content is guided by the solution of following principal ecologic-geological problems:
- the substantiation of tectonic stability of the region as a whole and chosen sites in particle;
- determination of migration behavior of technogenous elements worsening the ecological state of biosphere;
- study of the interaction between the rocks incorporating a repository and groundwater containing radionuclides.
The Project takes into account the necessity to publish the safety forecast and to inform the population about comparative assessments of acceptable hazard levels. Problems designated in the Project are the part of general problem of safe disposition of HLW in geological formations, and the solution is aimed to speed up the regional storage facility design in the Russian Federation.
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