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Heat-Pipe Effect on the Transport of Gaseous Radionuclides Released from a Nuclear Waste Container

Published online by Cambridge University Press:  28 February 2011

W. Zhou ,
P. L. Chambré ,
T. H. Pigford  and
W. W.-L. Lee
W. Zhou
Affiliation:
Department of Nuclear Engineering, University of California, and Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
P. L. Chambré
Affiliation:
Department of Nuclear Engineering, University of California, and Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
T. H. Pigford
Affiliation:
Department of Nuclear Engineering, University of California, and Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
W. W.-L. Lee
Affiliation:
Department of Nuclear Engineering, University of California, and Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720
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Abstract

We present analytic studies of the transport of gaseous species released from a spent-fuel waste package, as affected by a heat-pipe of counterflowing liquid and vaporized water in the surrounding rock. A heat-pipe is caused by heating which vaporizes pore water near the waste, releasing vapor into the fractures. Driven by its pressure gradient, the vapor flows away from the waste and condenses where the rock is cooler. Because of capillary pressure gradient due to non-uniform liquid saturation, condensate flows towards the waste through the porous rock. We first develop analytic solutions for the time-dependent transport of energy and fluid from the waste container to the surrounding fractured porous rock. From the mass fluxes of liquid and vapor, we solve the advective-diffusive transport of a gaseous species released from the waste. The major assumptions are quasi-steady-state, local thermodynamic equilibrium, no noncondensable gases, and no sorption. Our results include the extent of the heat-pipe zone as function of time, the vapor velocity distribution in the heat-pipe zone, radionuclide concentration in water vapor, and the flux of radionuclide at the waste surface normalized to the surface concentration. We find that the vapor velocity in the heat-pipe zone is 1000-fold greater than the local air velocity if there were no heat pipe. If the gaseous species release mechanism maintains a near-constant concentration of gaseous species in the gas outside and near the waste container surface, the mass rate of transport of that species would be increased 1.3 to 7 times greater than if there were no heat pipe. However, if the release rate of the gaseous species is affected little by the concentration of that species outside the container, the heat-pipe can have little affect on the transport rate of that species.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 212: Symposium P – Scientific Basis for Nuclear Waste Management XIV , 1990 , 855
Copyright
Copyright © Materials Research Society 1991

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References

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