RD&D-Programme 2004 - SKB

Max canister surface temperature [°C]
110
105
100
95
90
85
80
75
Vertical deposition, 1,700 W/canister, bentonite conductivity 1.0 W/mK
Rock initial temperature 15 degr.
Rock heat capacity 2.08 MJ/m 3 K
2.4
2.6
2.8
3
3.2
3.4
3.6
70
5 6 7 8 9 10 11 12
Canister spacing (m)
Figure 19-1. Maximum temperature on canister surface for different assumptions regarding the
thermal conductivity of the rock. The horizontal lines are threshold values that correspond to
different margins to the design criterion temperature of 100°C.
A strategy has been formulated for how a thermal site descriptive model should be developed
during the site investigation phase /19-4/. The basis for the thermal model is the geological and
hydrogeological site descriptive models and direct measurements of thermal and geophysical
properties.
The scale dependence of the effects of rock type distribution has been analyzed as a step in the
development of a thermal model for the Äspö HRL /19-5/. Furthermore, thermal conductivities,
measured or calculated from mineralogical composition, have been analyzed statistically. In
addition, a relationship between density and thermal conductivity has been determined for the
rock types in the Äspö HRL. Based on this, geophysical density loggings have been utilized in
an attempt to analyze the distribution and scale dependence of the thermal properties of the rock
mass at Äspö.
Programme
The analyses that have now been done to determine the spacing between the canisters will be
expanded and coordinated with the analyses that are being done for the canister/buffer system
(e.g. to arrive at an appropriate way to handle air gaps). Furthermore, the calculations will be
broadened to include the effects of relocating canister hole positions with unchanged, or only
marginally increased, average canister spacing. The effects of variations in the thermal properties
of the rock, on different scales, on the determination of canister spacing will be investigated
numerically and analytically.
The work of developing, calibrating and verifying methods for determination of thermal
properties will continue, as will the work of translating the results into thermal models on
different scales.
The temperature measurements in the rock being done in the Prototype Repository and the
Canister Retrieval Test at the Äspö HRL will be evaluated to determine heat transport properties
by back-calculation.
RD&D-Programme 2004 245