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Summary of Results From the Series 2 and Series 3 NNWSI Bare Fuel Dissolution Tests

Published online by Cambridge University Press:  28 February 2011

C. N. Wilson
C. N. Wilson*
Affiliation:
Pacific Northwest Laboratory, P. O. Box 999, Richland, WA 99352
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Abstract

The Nevada Nuclear Waste Storage Investigations (NNWSI) Project is studying dissolution and radionuclide release behavior of spent nuclear fuel in Nevada Test Site groundwater. Specimens prepared from pressurized water reactor (PWR) fuel rod segments were tested for multiple cycles in J-13 well water. The Series 2 tests were run in unsealed silica vessels under ambient hot cell air (25°C) for five cycles for a total of 34 months. The Series 3 tests were run in sealed stainless steel vessels at 25°C and 85°C for three cycles for a total of 15 months. Selected summary results from Series 2 and Series 3 tests with bare fuel specimens are reported.

Actinide concentrations tended to saturate and then often decreased during test cycles. Uranium concentrations in later test cycles ranged from 1 to 2 μg/ml in the Series 2 Tests versus about 0.1 to 0.4 μg/ml in Series 3 with the lowest concentrations occurring in the 85°C tests. Formation of a calciumuranium-silicate phase identified as uranophane in the 85°C Series 3 Tests is thought to have limited uranium concentration in these tests. Americium-241, Pu-239 and Pu-240 activities measured in filtered solution decreased to less than 1 pCi/ml in the 85°C tests. Preferential release of fission products Cs, I, Sr and Tc, and activation product C-14, was indicated relative to the actinides. Tc-99 and Cs-137 activities measured in solution after Cycle 1 increased linearly with time, with the rate of increase greater at 85°C than at 25°C. Continuous preferential release of soluble fission products is thought to result primarily from the dissolution of fine particles of fission product phases concentrated on grain boundaries.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 112: Symposium P – Scientific Basis for Nuclear Waste Management XI , 1987 , 473
Copyright
Copyright © Materials Research Society 1988

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References

1. Wilson, C.N., Results From Cycles 1 and 2 of NNWSI Series 2 Spent Fuel Dissolution Tests, HEDL-TME 85–22, Hanford Engineering Development Laboratory, Richland, WA, May, 1987.Google Scholar
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