Euradwaste '08 - EU Bookshop - Europa

Distance from heater surface (mm)
100
90
80
70
60
50
40
30
20
10
0
0.00E+00 1.00E-03 2.00E-03 3.00E-03 4.00E-03 5.00E-03 6.00E-03 7.00E-03 8.00E-03
Concentration (mol/kg)
197
Initial
1 Day
3 Day
7 Day
15 day
30 Day
Figure 2: Chloride distribution of T-test (initial degree of saturation 65 %)
Tests were also done to investigate the effect of temperature on HM-properties. In one set of tests
FEBEX bentonite was compacted at dry densities 1.50 and 1.60 g/cm3 and saturated with deionised
water under vertical stresses from 0.1 to 3.0 MPa at temperatures from 30 to 80°C while the vertical
strains were measured. In another FEBEX bentonite compacted at dry density 1.50, 1.60 and 1.70
g/cm3 was saturated with deionised water under constant volume conditions and temperatures from
20 to 80°C while the swelling stresses developed were measured. Afterwards permeability was determined
in the same specimens by imposing hydraulic gradients to the saturated samples. The
swelling under load tests have shown that the effect of temperature on the swelling capacity is
smaller than the effect of the vertical load applied during hydration or the effect of initial dry density.
The Febex Mock-up is an experiment at almost full scale and under controlled boundary conditions.
The aim is to know and understand the long-term behaviour of a clay barrier submitted to thermal
and hydraulic gradients, and to validate and verify the near field THM models under controlled
boundary conditions. The mock-up test surpasses the space-scale limitation of the laboratory tests,
by adoption of the actual dimensions of the repository, but it does not prevent the time-scale limitation.
The duration of the test, related to the operative life of the repository, makes it possible to extrapolate
the future behaviour of the clay barrier from the experimental transient state [3] (ENRESA
1997). The final evaluation will be made after the dismantling. However, the test is stilla a valuable
instrument to understand and evaluate the behaviour in the near field, and the generated data-base
has value in itself. In particular, it has verified most of the hypothesis on the THM processes in the
transient phase of the clay barrier, especially in the presence of water vapour.
The Febex “in situ” test consisted of a full-scale simulation of a HLW disposal facility, in accordance
with the ENRESA AGP Granito (Deep Geological Disposal, Granite) reference concept. The
test comprises two electrical heaters, of dimensions and weight equivalent to those of the canisters
in the concept, in a 2.28 m diameter drift specifically selected and excavated in granite. The entire
space surrounding the heaters is filled with blocks of compacted bentonite to complete the 17.4 m
of barrier for the test section. This test zone was closed with a concrete plug. The test was installed