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Release of 108Ag from Irradiated PWR Control Rod Absorbers under Deep Repository Conditions

Published online by Cambridge University Press:  27 April 2015

O. Roth
Affiliation:
Studsvik Nuclear AB, Hot Cell Laboratory, SE-611 82 Nyköping, Sweden
M. Granfors
Affiliation:
Studsvik Nuclear AB, Hot Cell Laboratory, SE-611 82 Nyköping, Sweden
A. Puranen
Affiliation:
Studsvik Nuclear AB, Hot Cell Laboratory, SE-611 82 Nyköping, Sweden
K. Spahiu
Affiliation:
SKB, Box 250, SE-101 24, Stockholm, Sweden.
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Abstract

In a future Swedish deep repository for spent nuclear fuel, irradiated control rods from PWR nuclear reactors are planned to be stored together with the spent fuel. The control rod absorber consists of an 80% Ag, 5% Cd, 15% In alloy with a steel cladding. Upon in-reactor irradiation 108Ag is produced by neutron capture. Release of 108Ag has been identified as a potential source term for release of radioactive substances from the deep repository.

Under reducing deep repository conditions, the Ag corrosion rate is however expected to be low which would imply that the release rate of 108Ag should be low under these conditions. The aim of this study is to investigate the dissolution of PWR control rod absorber material under conditions relevant to a future deep repository for spent nuclear fuel. The experiments include tests using irradiated control rod absorber material from Ringhals 2, Sweden. Furthermore, un-irradiated control rod absorber alloy has been tested for comparison. The experiments indicate that the release of Ag from the alloy when exposed to water is strongly dependent on the redox conditions. Under aerated conditions Ag is released at a significant rate whereas no release could be measured after 133 days during leaching under H2.

Type
Articles
Copyright
Copyright © Materials Research Society 2015 

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References

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