Evaluation and compilation of DOE waste package test data: Biannual report, August 1987--January 1988 Page: 18 of 184
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phases at elevated temperatures, with and without radiation
is evaluated in this study [Yunker et al. 1986]. After 14
months of exposure, the corrosion rates observed are low,
less than 13 Am/y (< 0.5 mils per year), and these
preliminary observations indicate that the corrosion rate
of the 7 percent aluminum-copper is less than that of the
pure copper. The results on the 30 percent nickel-copper
are erratic, and pitting and crevice corrosion were
observed on this alloy between an alumina washer and a flat
specimen. To a more limited extent, on the other two
materials pitting and crevice corrosion were also observed.
2.3 Groundwater
Present knowledge about the corrosivity in tuff is based on
the chemical composition of water samples taken from a well
near the proposed Yucca Mountain repository site. This J-13
well water has a low concentration of soluble salts, and is
considered relatively noncorrosive. However, in the presence
of gamma radiation from the nuclear waste, water is expected
to undergo chemical changes, some of which may result in
increased corrosion attack on the canister materials and
subsequent increased dissolution of the waste.
Ebert et al., describe a study in which small coupons of
waste glass and Topopah spring tuff are placed in J-13 spring
water in the presence and absence of radiation. The plots
give data taken at each of 5 to 7 periods of exposure, each
lasting from 14 to 280 days. After exposure, the tests were
stopped, the water analyzed, and the coupon surfaces
examined. The results show that nitric acid is formed in the
radiation field, but buffering effects will limit the pH to a
minimum of about 6.4. Most importantly, however, the data
indicate that plutonium can form pseudo-colloids and this may
facilitate transport to the environment [Ebert et al. 1986].
2.4 Glass Waste
Once the canister, the primary barrier, is breached,
groundwater is free to contact the radioactive waste. Thus,
the interactions between groundwater and the radionuclides
contained in the canister and the effects of these
interactions on radionuclide release to the environment are
major 'concerns.
Bates and Gerding describe a test for measuring radionuclide
release rates in which tuff groundwater is dripped onto a waste
glass assembly for 13 and 26 weeks. Radionuclide release rate
is determined from analysis of the water collected and analysis
of the assembly surfaces. The authors indicate that the results
of these tests show that this method of testing provides
reproducible results and realistically simulates repository
conditions [Bates et al. 1985].6
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Interrante, C.; Escalante, E.; Fraker, A.; Ondik, H.; Plante, E.; Ricker, R. et al. Evaluation and compilation of DOE waste package test data: Biannual report, August 1987--January 1988, report, August 1, 1988; United States. (https://digital.library.unt.edu/ark:/67531/metadc691054/m1/18/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.