POSIVA 99-01

Measurement of thermal conductivity and diffusivity in situ: Literature survey and theoretical modelling of measurements llmo Kukkonen llkka Suppala Geological Survey of Finland

January 1999

POSIVA OY Mikonkatu 15 A, FIN-00100 HELSINKI, FINLAND Phone (09) 2280 30 (nat.), (+358-9-) 2280 30 (int.)

AUTHOR ORGANIZATION:

Geological Survey of Finland P.O. Box 96 FIN -02151 Espoo Finland

ORDERER:

Posiva Oy Mikonkatu 15 A FIN -001 00 Helsinki Finland

NUMBER OF THE ORDERER:

9643/98/AJH

CONTACT PERSON OF THE ORDERER:

Aimo Hautojarlt

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CONTACT PERSON OF THE AUTHOR ORGANIZATION: Ilmo Kukkonen

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Figure 6. a) Temperature records of the cylindrical continuous heating probe constructed by Burkhadt et al. (1995) in the KTB project, b) thermal conductivities determined at four depth values from temperatures responses of different temperature sensors.

23 Kristiansen et al. (1982) described in situ measurements in very shallow holes drilled in outcrops of either Precambrian, Paleozoic and Mesozoic rocks on the island ofBornholm, Denmark. They applied a cylindrical hollow 0.42 m long probe with a diameter of 1.2 cm. Measurements were conducted either in water, grease or air filled holes with the same nominal diameter as the probe. One thermistor was placed at the central part of the probe and heating power was about 20 W m- 1 through an insulated manganin electrical heating wire. Measuring times of up to 5000 s were applied, and thermal conductivity value was derived from the linear approximation for long measuring times. For crystalline rocks, the results were in a tight range, and they were also controlled from estimates based on mineral composition. The agreement was found to be good. Sedimentary rocks showed much more wider range in measured conductivity values. Scroth (1983) presented a probe for simultaneous measurement of natural temperature gradient in the rock as well as thermal conductivity in situ measurement using the cylindrical source method. The probe (diameter 46 mm) was designed for use in shallow ( 0 ~

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