Nuclear Energy for New Europe 2009

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No: 902

Conference: Nuclear Energy for New Europe 2009

Title: Potential Retrieval of Buried Spent Nuclear Fuel and Civil Engineering Aspects

Theme: Radioactive Waste Management

Author(s): Radek Vašiček, Jiří Svoboda

Contact : Radek Vašiček

E-mail: radek.vasicek@fsv.cvut.cz

Address: Czech Technical University in Prague, Faculty of Civil Engineering, Centre of Experimental Geotechnics
16629 Prague 6

Country: Czech Republic

The current solution for the disablement of radioactive materials at the end of the fuel cycle is to store them at surface facilities from which they will be subsequently moved to a deep repository. However, only a small number of such repositories are in operation or under construction globally at present, although they are planned in most of those countries with a civil nuclear programme. A deep repository can be situated in several types of geological conditions including clay formations, salt sediments, argillites and tuffitic and granitic rocks. The character of the host rock is the key factor determining the design and exact requirements of several components of such a facility. The future potential retrieval of canisters containing nuclear waste from the repository is a further influential factor. The reason for removing containers lies in the potential development of presently unavailable “perfect” technology for waste reprocessing. Naturally, the decision as to whether retrievability is technically feasible must be made before finalising the design and construction process of the repository. If the decision is made to retrieve, a design which will include all the relevant safety conditions for the potential retrieval of canisters must be determined. The lay-out of the repository, the materials to be used and the design of the various structures of the facility (e.g. access tunnels, disposal shafts, buffer and backfill) are not the only issues to be addressed. The long-term stability of the system as a whole, i.e. of all the components, is crucial. Depending on the disposal concept chosen, the thermal load generated by the waste in the disposal container, saturation by water from the surrounding environment and the loading of the host rock massif will constitute the main processes which will affect the behaviour, safety and future functioning of the repository from the civil engineering point of view. The long-term stability of the lining of disposal galleries is a basic precondition for the safe removal of spent nuclear waste from deep underground repositories. The stability problems of tunnel linings exposed to long-term thermal load have not yet been properly addressed and form the subject of the European TIMODAZ project (Thermal Impact on the Damaged Zone around a Radioactive Waste Disposal in Clay Host Rocks). This paper describes the design, construction and currently available results of a 1:1 scale “in-situ” disposal tunnel model which has been built at the Josef Underground Educational Facility in the Czech Republic.

No:	902
Conference:	Nuclear Energy for New Europe 2009
Title:	Potential Retrieval of Buried Spent Nuclear Fuel and Civil Engineering Aspects
Theme:	Radioactive Waste Management
Author(s):	Radek Vašiček, Jiří Svoboda
Contact :	Radek Vašiček
E-mail:	radek.vasicek@fsv.cvut.cz
Address:	Czech Technical University in Prague, Faculty of Civil Engineering, Centre of Experimental Geotechnics 16629 Prague 6
Country:	Czech Republic

The current solution for the disablement of radioactive materials at the end of the fuel cycle is to store them at surface facilities from which they will be subsequently moved to a deep repository. However, only a small number of such repositories are in operation or under construction globally at present, although they are planned in most of those countries with a civil nuclear programme. A deep repository can be situated in several types of geological conditions including clay formations, salt sediments, argillites and tuffitic and granitic rocks. The character of the host rock is the key factor determining the design and exact requirements of several components of such a facility. The future potential retrieval of canisters containing nuclear waste from the repository is a further influential factor. The reason for removing containers lies in the potential development of presently unavailable “perfect” technology for waste reprocessing. Naturally, the decision as to whether retrievability is technically feasible must be made before finalising the design and construction process of the repository. If the decision is made to retrieve, a design which will include all the relevant safety conditions for the potential retrieval of canisters must be determined. The lay-out of the repository, the materials to be used and the design of the various structures of the facility (e.g. access tunnels, disposal shafts, buffer and backfill) are not the only issues to be addressed. The long-term stability of the system as a whole, i.e. of all the components, is crucial. Depending on the disposal concept chosen, the thermal load generated by the waste in the disposal container, saturation by water from the surrounding environment and the loading of the host rock massif will constitute the main processes which will affect the behaviour, safety and future functioning of the repository from the civil engineering point of view. The long-term stability of the lining of disposal galleries is a basic precondition for the safe removal of spent nuclear waste from deep underground repositories. The stability problems of tunnel linings exposed to long-term thermal load have not yet been properly addressed and form the subject of the European TIMODAZ project (Thermal Impact on the Damaged Zone around a Radioactive Waste Disposal in Clay Host Rocks). This paper describes the design, construction and currently available results of a 1:1 scale “in-situ” disposal tunnel model which has been built at the Josef Underground Educational Facility in the Czech Republic.