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TIMODAZ – Lining Stability under Thermal Load
Jaroslav Pacovský, Ji�í Svoboda, Radek Vaší�ek
Centre of Experimental Geotechnics, Czech Technical University in Prague, Czech Republic
Summary
The TIMODAZ Project is co-funded by the European Commission (EC) as part of the sixth
EURATOM research and training Framework Programme (FP6) on nuclear energy. TIMO-
DAZ is a four-year Specific Targeted Project (2006-2010) investigating thermal impact on the
damaged zone around a radioactive waste disposal vessel in clay host rocks. The TIMODAZ
consortium is composed of 14 participating organisations representing a total of 8 European
countries (BE, FR, CH, DE, NL, ES, CZ, UK).
The extreme long-term functioning of the lining around the disposal vessel is one of the premises
for the safe removal of spent fuel canisters from the engineered barrier. The long-term effects
of heat could well bring about a severe reduction in the stability of the lining caused either
by deterioration in the strength properties of the lining material or by the occurrence of
deformations resulting in a collapse in the shape of the lining.
Research into lining stability under thermal loading at the Centre of Experimental Geotechnics
(CEG) employs physical modelling.
1. Introduction
As part of the Timodaz Project, two physical models of the lining of disposal tunnels have been
built and put into operation – a laboratory model constructed at CEG itself and an “in situ” model
constructed in the underground laboratory of the Josef UEF. The effects of long-term thermal loading
acting on the lining and its stability are being investigated with the help of these models.
The laboratory experiment is designed to allow the deformation of the circular lining. Consequently,
a low degree of stress is generated within the prefabricated lining blocks but the deformation
of the circular lining itself could be enormous.
The model constructed in the Josef underground laboratory has been designed so that the lining
cannot be deformed in the direction towards the rock mass and, consequently, enormous stress is
generated within the lining material.
The laboratory model studies whether the thermal load acting on the lining might lead to a level of
deformation which could lead to a decrease in the dimensional stability of the lining. The “in situ”
model investigates whether long-term thermal loading could result in a level of stress acting on the
lining material that would exhaust its strength parameters causing cracking and the subsequent collapse
of the lining.
2. Methodology
Physical modelling is one of the tools available to researchers in addressing the problems of radioactive
waste disposal in a deep repository. Since such research is of a highly specialised and interdisciplinary
nature, all the relevant tools at hand must be applied, i.e. laboratory, “in situ” experimental
research and physical and mathematical modelling, Pacovský et. al. (2007) [1].
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