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TIMODAZ – Large-Scale Heater Experiments In Boom Clay
Jan Verstricht 1 , Wim Bastiaens 1 , Xiang Ling Li 1 , Philippe Van Marcke 1 , Guangjing Chen 1 , Xavier
Sillen 2
Summary
1 EIG EURIDICE, Mol, Belgium
2 SCK•CEN, Mol, Belgium
The thermal impact of heat-dissipating, high-level radioactive waste is one of the main disturbances
that are considered in the framework of the geological disposal of this waste. Within
the Belgian research programme, which focuses on the Boom Clay formation as potential host
rock, this aspect has been the subject of several field tests complementing the desk studies. A
large scale integration of the thermal issue is now being implemented as the PRACLAY
Heater Test, a main constituent of the overall PRACLAY demonstration programme. This
programme intends to simulate at real scale (except length and time) a disposal gallery
through all phases: construction (shaft, main gallery, test gallery including gallery crossing)
using industrial techniques, followed by the backfilling, sealing and saturation of the PRA-
CLAY test gallery, after which the heating of the test gallery will be switched on during 10
years. As a preparation to this large scale heater test, an already existing test set-up ("AT-
LAS") has been extended and re-activated. The experimental data obtained have allowed improving
the characterisation of the Boom Clay, for example by incorporating the anisotropy of
the thermal conductivity. The PRACLAY Heater Test will allow confirming these findings at
large scale. The host rock around the gallery, as well as the gallery itself, are extensively instrumented
to this purpose. The test results will constitute an important field database for the
validation of the numerical tools to be developed in the frame of the EC project TIMODAZ,
as well as for the evaluation of the Safety and Feasibility Case 1 (SFC1).
1. Introduction
The thermal aspect has been considered from the very beginning in the desk studies and small-scale
field tests on the research of the disposal of heat-dissipating high-level radioactive waste (HLW),
The temperature increase of host formation strongly influences the hydraulic and mechanical behaviour.
It has further an effect on the chemical and microbiological conditions in the host rock.
The early transient thermo-hydro-mechanical (THM) perturbation might be the most severe impact
that the disposal system will undergo on a large spatial scale and in a relatively short period of time.
Complementing the desk studies and modelling work, the thermal aspect is therefore also the object
of many experimental set-ups at the lab and in situ. With the current evolution in the R&D to integration
and demonstration, the study of the impact of the heating at large scale becomes essential.
For more than 30 years, Belgium has been actively studying the long-term management of highlevel
and/or long-lived radioactive waste. The Belgian Research Centre SCK•CEN initiated the
R&D programme in 1974 following international recommendations to isolate HLW from the biosphere
by disposing of it in a stable geological formation with appropriate characteristics. For vari-
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