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Title:
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Immobilisatie van langlevende splijtingsproducten: een literatuurstudie
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Author(s):
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Published by:
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Publication date:
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ECN
NUC
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1998
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ECN report number:
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Document type:
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ECN-C--97-095
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ECN publication
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Number of pages:
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Full text:
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73
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Download PDF
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Abstract:
With present nuclear facilities, the transmutation of long-lived fissionproducts Cs-135, Tc-99 and 1-129 into short-lived, harmless isotopes does not
seem to be efficient. Therefore, appropriate solutions for the ultimate
disposal of these geochemical mobile radionuclides should be developed. At
present, the high-level liquid waste stream that results from the commercial
reprocessing of spent fuel is vitrified using borosilicate glass. This
high-level waste stream includes most fission products, minor actinides (Am,
Np, Cm) as well as traces of U and Pu. However, under conditions of constant
water-renewal in the disposal facility the long-term stability of
borosilicate glass cannot be guaranteed over the lifetime of Cs-135 and
Tc-99. Alternatively, the use of synthetic mineral assemblages such as, e.g.,
SYNROC, for the immobilization of spent fuel high-level waste stream is under
study in various countries. For most geological conditions, this material
seems to have better corrosion resistance as compared to borosilicate glass
with (much) better leaching characteristics of the radionuclides. In
addition, natural analogues studies can be used to assess the performance of
SYNROC assemblages on a geological timescale, including the effect of
radiation damage on long-term stability and leaching characteristics of the
mineral assemblages. At present, with commercial reprocessing of spent fuel
I-129 is disposed of via controlled discharges into the ocean in accordance
with official regulations. For this reason, little effort has been given for
the immobilization of I-129. In order to further reduce the long-term
radiological hazards involved with geological disposal of high-level
radioactive waste it is interesting to study the selective immobilization of
individual radionuclides, most importantly Cs-135, Tc-99 and I-129. It is
anticipated that selective immobilization gives better opportunities to
prevent these radionuclides from entering the biosphere on the long term.
This report summarizes the state-of-the-art in the selective immobilization
of long-lived fission products and actinides. The role of natural analogue
studies in assessing the performance of the waste form under actual disposal
conditions on geological time scale is also discussed. 100 refs.
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