A comprehensive test program to evaluate nonmetallic materials use in the Hanford tank farms is described in detail. This test program determines the effects of simultaneous multiple stressors at reasonable conditions on in-service configuration components by engineering performance testing.
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A comprehensive test program to evaluate nonmetallic materials use in the Hanford Tank Farms is described in detail. This test program determines the effects of simultaneous multiple stressors at reasonable conditions on in-service configuration components by engineering performance testing.
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The Fracture-Matrix Transport (FMT) code developed at Sandia National Laboratories solves chemical equilibrium problems using the Pitzer activity coefficient model with a database containing actinide species. The code is capable of predicting actinide solubilities at 25 C in various ionic-strength solutions from dilute groundwaters to high-ionic-strength brines. The code uses oxidation state analogies, i.e., Am(III) is used to predict solubilities of actinides in the +III oxidation state; Th(IV) is used to predict solubilities of actinides in the +IV state; Np(V) is utilized to predict solubilities of actinides in the +V state. This code has been qualified for predicting actinide solubilities for the Waste Isolation Pilot Plant (WIPP) Compliance Certification Application in 1996, and Compliance Re-Certification Applications in 2004 and 2009. We have established revised actinide-solubility uncertainty ranges and probability distributions for Performance Assessment (PA) by comparing actinide solubilities predicted by the FMT code with solubility data in various solutions from the open literature. The literature data used in this study include solubilities in simple solutions (NaCl, NaHCO{sub 3}, Na{sub 2}CO{sub 3}, NaClO{sub 4}, KCl, K{sub 2}CO{sub 3}, etc.), binary mixing solutions (NaCl+NaHCO{sub 3}, NaCl+Na{sub 2}CO{sub 3}, KCl+K{sub 2}CO{sub 3}, etc.), ternary mixing solutions (NaCl+Na{sub 2}CO{sub 3}+KCl, NaHCO{sub 3}+Na{sub 2}CO{sub 3}+NaClO{sub 4}, etc.), and multi-component synthetic brines relevant to the WIPP.
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Backfills have been part of Sandia National Laboratories' [Sandia's] Waste Isolation Pilot Plant [WIPP] designs for over twenty years. Historically, backfill research at Sandia has depended heavily on the changing mission of the WIPP facility. Early testing considered heat producing, high level, wastes. Bentonite/sand/salt mixtures were evaluated and studies focused on developing materials that would retard brine ingress, sorb radionuclides, and withstand elevated temperatures. The present-day backfill consists of pure MgO [magnesium oxide] in a pelletized form and is directed at treating the relatively low contamination level, non-heat producing, wastes actually being disposed of in the WIPP. Its introduction was motivated by the need to scavenging CO{sub 2} [carbon dioxide] from decaying organic components in the waste. However, other benefits, such as a substantial desiccating capacity, are also being evaluated. The MgO backfill also fulfills a statutory requirement for assurance measures beyond those needed to demonstrate compliance with the US Environmental Protection Agency [EPA] regulatory release limits. However, even without a backfill, the WIPP repository design still operates within EPA regulatory release limits.
The corrosion and gas-generation characteristics of four material types: low-carbon steel (the current waste packaging material for the Waste Isolation Pilot Plant), Cu-base and Ti-base (alternative packaging) materials, and Al-base (simulated waste) materials were determined in both the liquid and vapor phase of Brine A, a brine representative of an intergranular Salado Formation brine. Test environments consisted primarily of anoxic brine with overpressures of N{sub 2}, CO{sub 2}, H{sub 2}S, and H{sub 2}. Limited tests of low-carbon steel were also performed in simulated-backfill environments and in brine environments with pH values ranging from 3 to 11. Low-carbon steel reacted at a slow, measurable rate with anoxic brine, liberating H{sub 2} on an equimolar basis with Fe reacted. Presence of CO{sub 2} caused the initial reaction to proceed more rapidly, but CO{sub 2}-induced passivation stopped the reaction if the CO{sub 2} were present in sufficient quantities. Addition of H{sub 2}S to a CO{sub 2}-passivated system caused reversal of the passivation. Low-carbon steel immersed in brine with H{sub 2}S showed no reaction, apparently because of passivation of the steel by formation of FeS. Addition of CO{sub 2} to an H{sub 2}S-passivated system did not reverse the passivation. Cu- and Ti-base materials showed essentially no corrosion when exposed to brine and overpressures of N{sub 2}, CO{sub 2}, and H{sub 2}S except for the rapid and complete reaction between Cu-base materials and H{sub 2}S. The Al-base materials reacted at approximately the same rate as low-carbon steel when immersed in anoxic Brine A; considerably more rapidly in the presence of CO{sub 2} or H{sub 2}S; and much more rapidly when iron was present in the system as a brine contaminant. High-purity Al was much more susceptible to corrosion than the 6061 alloy. No significant reaction took place on any material in any environment in the vapor-phase exposures.
Materials Research Society Symposium Proceedings
The design-basis, defense-related, transuranic waste to be emplaced in the Waste Isolation Pilot Plant may, if sufficient H2O, nutrients, and viable microorganisms are present, generate significant quantities of gas in the repository after filling and sealing. We summarize recent results of laboratory studies of anoxic corrosion and microbial activity, the most potentially significant processes. We also discuss possible implications for the repository gas budget.
This paper justifies the need for and describes studies of brine chemistry under way for German and American high- and intermediate-level radioactive waste repositories in domal and bedded salt formation. In particular, it discusses the origin and composition of fluids that could enter these repositories and some sampling, modeling, and statistical techniques used to characterize them. 24 refs., 4 figs., 5 tabs.
This Test Plan describes laboratory and modeling studies of: the chemistry of brines that could enter Waste Isolation Pilot Plant (WIPP) disposal rooms; the effects of anoxic corrosion of metals in steel containers and the waste on the gas and H{sub 2}O budgets of the repository; the effects of microbial activity, especially microbial degradation of cellulosics in the waste, on the gas and H{sub 2}O budgets of the repository, the Eh and pH of any brine present, and the chemical behavior of radionuclides; the effects of radiolysis on the gas and H{sub 2}O budgets of the repository; the efficacy of backfill additives proposed to remove microbially produced CO{sub 2} or prevent the formation of H{sub 2} from anoxic corrosion, and their effects on repository chemistry; the chemical behavior of Pu, Am, Th, and U in WIPP brines; additional development of the EQ3/6 geochemical software package for use in predicting the behavior of silicates and radionuclides in brines. This Test Plan describes studies of the chemical behavior of the repository as currently designed, and the chemical behavior of radionuclides under these conditions. Addenda will discuss additional studies relevant to design modifications, especially reprocessed waste, and chemically hazardous waste constituents. 165 refs., 7 tabs.
The design-basis, defense-related, transuranic (TRU) waste to be emplaced in the Waste Isolation Pilot Plant (WIPP) could, if sufficient H{sub 2}O and nutrients were present, produce as much as 1,500 moles of gas per drum of waste. Gas production could pressurize the repository to 150 atm (lithostatic pressure) and perhaps higher. Anoxic corrosion of Fe and Fe-base alloys and microbial degradation of cellulosics are the processes of greatest concern, but radiolysis of brine could also be important. The proposed backfill additives CaCO{sub 3}, CaO, CuSO{sub 4}, KOH, and NaOH may remove or prevent the production of some of the expected gases. Because of the heterogeneous nature of design-basis waste, the Eh and pH of any brine present in WIPP disposal rooms could vary significantly over short distances after reacting with the waste. The WIPP Project is investigating the consequences of gas production and considering engineered alternatives, including reprocessing the waste, to reduce gas production rates or potentials. Reprocessing would also reduce the range of Eh and pH expected for the repository. 12 refs.