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Low Temperature Vitrification of Radioiodine Using AgI-Ag2O-P2O5 Glass System

Published online by Cambridge University Press:  10 February 2011

H. Fujihara ,
T. Murase ,
T. Nisli ,
K. Noshita ,
T. Yoshida  and
M. Matsuda
H. Fujihara
Affiliation:
Tokyo Electric Power Company, 1-3 Uchisaiwai, Chiyoda, Tokyo 100-0011, Japan
T. Murase
Affiliation:
Tokyo Electric Power Company, 1-3 Uchisaiwai, Chiyoda, Tokyo 100-0011, Japan
T. Nisli
Affiliation:
Power & Industrial Systems R&D Division, Hitachi Ltd., 7-2-1 Omika, Hitachi, Ibaraki 319-1221, Japan
K. Noshita
Affiliation:
Power & Industrial Systems R&D Division, Hitachi Ltd., 7-2-1 Omika, Hitachi, Ibaraki 319-1221, Japan
T. Yoshida
Affiliation:
Hitachi Works, Hitachi Ltd., 3-1-1 Saiwai, Hitachi, Ibaraki 317-0073, Japan
M. Matsuda
Affiliation:
Hitachi Works, Hitachi Ltd., 3-1-1 Saiwai, Hitachi, Ibaraki 317-0073, Japan
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Abstract

A new vitrification process for radioiodine has been developed for safe disposal of the spent iodine adsorbent generated from reprocessing off-gas systems. The proposed process consists of the following two steps: (1) separation of radioiodine as AgI from spent iodine adsorbent and (2) vitrification of the separated AgI with silver phosphate. An AgI-Ag2O-P2O5 glass system can homogeneously contain up to 60mol%AgI, which leads to high volume reduction efficiency (approximately 1/25). It also can vitrify the AgI without volatilization of iodine because of its low melting temperature (below 400°C). The leachabilities of iodine from simulated vitrified waste forms were evaluated by the MCC-1 static leach test in an anaerobically controlled glove box, which was purged by nitrogen gas with 3% hydrogen. The leaching behavior of the Agl-Ag2O-P2O5 glass system was influenced by the composition of the actual glass, type of leachant, and redox conditions. When the leach test was carried out using simulated ground wateroriginating from rainfall, the leach rate of iodine from 3AgI-Ag4P2O7 glass was 6×10−8g/cm2/d in the early period of the leach test at 35°C under the reducing condition, after which it decreased to 3×10−9g/cm2/d. This glass showed a lower leach rate in the simulated ground water originating from sea water or cement saturated water, since a precipitation layer was formed on the surface.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 375
Copyright
Copyright © Materials Research Society 1999

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References

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