Effects of Alpha, Gamma, and Alpha-Recoil Radiation on Borosilicate Glass Containing Savannah River Plant Defense High-L
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EFFECTS OF ALPHA, GAMMA, AND ALPHA-RECOIL RADIATION ON BOROSILICATE GLASS CONTAINING SAVANNAH RIVER PLANT DEFENSE HIGH-LEVEL NUCLEAR WASTE
NED E. BIBLER E. I. du Pont de Nemours & Co., Aiken, South Carolina 29808
Savannah River Laboratory,
ABSTRACT At the Savannah River Plant, the reference process for the immobilization of defense high-level waste (DHLW) for geologic storage is vitrification into borosilicate glass. During geologic storage for 106 y, the glass would be exposed to -3 x 1010 rad of S radiation, -10 rad of y radiation, and 1010 particles/g glass for both a and a-recoil radiation. This paper discusses tests of the effect of these radiations on the leachability and density of the glass. No effect of the radiations was detected that reduced the effectiveness of the glass for long-term storage of DHLW even at doses corresponding to 106 years storage for the actual glass. For the tests, glass containing simulated DHLW was prepared from frit of the reference composition. Three methods were used to irradiate the glass: external irradiations with beams of -200 keV or Pb ions, internal irradiations with Cm-244 doped glass, and external irradiations with Co-60 y rays. Results with both Xe 2 and Pb ions indicate that a dose of 3 x 1013 ions/cm (simulating >106 years storage) does not significantly increase the leachability of the glass in deionized water. Tests with Cm-244 doped glass show no increase in leach rate in deionized water up to a dose of 1.3 x 1018 a and a-recoils/g glass. The density of the Cm-244 doped glass has decreased by 1% at a dose of 1018 particles/g glass. With y-radiation, the density has changed by 106 years storage time. I I Dopant 2M Cm
S
23 9
- -
pu
Rate, a/gd 6.6 x 1015 2.9 x 1011
,I lO-1•
io-2
6
10-3 -
Time for 10 -year dose in the Cm -glass
SI 0
\
" 100
, I 200
LeachTime, days
Fig.
2.
Leach rate decrease for modified IAEA tests in deionized water
at 230 C for SRP borosilicate glass based on 2 4• Cm or 2 3 9Pu. Variations in leach rates are due to replacing the leachant at the various times.
..
686 EXTERNAL GAMMA IRRADIATIONS Samples of the reference glass have been irradiated to 8.5 x 1010 rad with Co-60 gamma radiation. This dose is larger than the gamma-beta dose that the The dose rate of the actual DHLW glass would receive during 106 years storage. Co-60 radiation (1.6 x 107 rad/hr) was determined with thin-film dosimeters 0 Temperature during irradiation due to gamma heating was 85 C. No sig[7]. of radiation on the density or on the leachability in deionnificant effect ized water or simulated brine has been detected. The density data at 8.5 x 1010 rad suggest that the glass may have compacted This very small change, comslightly (
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