Best-basis estimates of solubility of selected radionuclides in sludges in Hanford single-shell tanks

Harmsen, R.W.

doi:10.2172/781548

Cited by 4 publications

(5 citation statements)

References 6 publications

(7 reference statements)

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“…Cobalt-60 is an activation product of stable 59 Co, which is a common impurity in zircaloy and aluminum fuel cladding and in uranium metal fuel (Harmsen and Schulz 1998). Cobalt-60 has a half-life (t ½ ) of 5.271 yrs (Tuli 2004).…”

Section: A142 Cobaltmentioning

confidence: 99%

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

Cantrell¹,

Zachara²,

Dresel³

et al. 2007

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Companion reports that review other subject matter areas relevant to contaminant transport within the vadose zone beneath the SST WMAs, the IDF, and groundwater have been recently published. The specific subject areas include the geology of the SST WMAs iv contaminants released to the vadose zone exhibit a wide range of mobility behaviors. Many tank waste contaminants have been strongly retarded by adsorption and precipitation reactions (e.g., cesium, plutonium, americium, and europium), while others have remained mobile (e.g., technetium, nitrate, and selenium). Still others show variable, waste-specific behaviors (e.g., cesium [where sodium concentrations are very high], strontium, chromium, and uranium) that are closely tied to evolving composition of pore water in the sediments, and for chromium, a change in oxidation state. The temperature of in-ground tank waste has moderated by heat exchange with the subsurface sediment, and high concentrations of base (OH -) have been neutralized through reactions with sediment minerals and secondary mineral precipitation. Major geochemical features that may potentially affect the mobility of key contaminants of interest in the vadose zone include oxidation state, aqueous speciation, solubility, and adsorption reactions.Processes suspected of facilitating the far-field migration of immobile radionuclides, such as formation of stable aqueous complex formation and mobile colloids, were found to be potentially operative, but unlikely to occur in the field. An exception is the enhanced migration of cobalt-60 facilitated by the formation of highly stable aqueous-cyanide complexes. Certain fission-product oxyanions (e. • Adsorption is suppressed by large concentrations of tank waste anions (e.g., NO 3 -, OH -, and CO 3 2-)• Surface charge of clay-size minerals is negative and will therefore tend to repel anions• Unlike chromium, their less-soluble, less-mobile reduced forms are unstable in oxidizing environments.Laboratory studies conducted through PNNL's Vadose Zone Characterization Project and basic-science geochemical studies are expected to continue in partnership to provide information to further refine the conceptual model used for risk assessment modeling. Results of these studies can be used to help ascertain uncertainties associated with the refinement of the conceptual models for contaminant migration in the vadose zone beneath the single-shell tanks. Results can also provide improved parameterization, such as distribution coefficients (K d ), and mathematical constructs used by modelers to predict contaminant mobility under these conditions, and to decrease the degree of conservatism incorporated in these models.For various reasons, risk assessment models typically use various approximations to represent the conceptual model developed for the site. Adsorption is frequently approximated using empirical distribution coefficients (K d s). Although the use of empirical distribution coefficients can potentially lead to erroneous results under certain conditions where the...

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Section: A142 Cobaltmentioning

confidence: 99%

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

Cantrell¹,

Zachara²,

Dresel³

et al. 2007

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“…An estimate based on Hanford caustic waste has concluded that 98% of the Nb as well as Zr is insoluble and is in the sludge solids. 10 The second way to estimate the activity concentration of Nb93m is to assume that all of the mass detected at 93 could indeed be Nb-93m rather than Zr-93 or Mo-93. Based on this, the maximum activity of Nb-93m, with its specific activity of 283 Ci/g, is 3.76E+07 pCi/mL.…”

Section: Estimate Of the Nb-93m Concentrationmentioning

confidence: 99%

Characterization of Tank 50 Slurry for Saltstone Waste Acceptance Criteria, April 2007 Samples

Zeigler¹,

Bibler²,

DiPrete³

2007

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“…Cobalt-60 is the isotope of primary importance to waste disposal and site remediation. Cobalt-60 is an activation product of stable 59 Co, which is a common impurity in zircaloy and aluminum fuel cladding and in uranium metal fuel (Harmsen and Schulz 1998). Cobalt-60 has a half life (t ½ ) of 1925.1 days (~5.3 yrs).…”

Section: Cobaltmentioning

confidence: 99%

“…Very little is known about the hydrolysis of Co(III) due to its reduction by water and slow reaction kinetics . According to Harmsen and Schulz (1998), Co(III) can also be stabilized relative to reduction by the formation of the cation Co III ( NO 2 ) 6 3+, which is stable in both acidic and alkaline media. Harmsen and Schulz (1998) note that the conditions occurring during the dissolution of nuclear fuels were favorable for conversion of possibly a large fraction of the cobalt to…”

Section: Pnnl-14126mentioning

confidence: 99%

“…• Iron oxide and oxyhydroxides (Means et al 1978b;Ambe et al 1986;Borggaard 1988;Bibak 1994;Backes et al 1995;Bibak et al 1995) • Manganese oxides (Means et al 1978b;Crowther et al 1983;Hem et al 1985;Dillard and Schenck 1986;Backes et al 1995;Bibak et al 1995;Kay et al 2001) • Aluminum oxides and hydroxides (Bibak 1994;Katz and Hayes 1995a,b;Towle et al 1997;Boyle-Wight et al 2002a,b) a Harmsen and Schulz (1998) also discuss the formation of Co III (NO 2 ) 6 3+ in the waste solutions in Hanford's storage. Harmsen and Schulz (1998) state that the anionic complex Co III (NO 2 ) 6 3+ is stable in both acidic and alkaline solutions, but give no supporting reference. b Brown et al (1990) summarizes the results of published XAS studies of the cobalt adsorption on single mineral phases, such as γ-Al 2 O 3 , kaolinite, rutile, quartz, and calcite.…”

Section: Adsorption In the Absence Of Organic Ligandsmentioning

confidence: 99%

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Geochemical Factors Affecting the Behavior of Antimony, Cobalt, Europium, Technetium, and Uranium in Vadose Zone Sediments

Krupka¹,

Serne²

2002

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In developing the Field Investigation Report for the Waste Management Area S-SX at the Hanford Site, 137 Cs was the only gamma emitting radionuclide of concern (Knepp 2002). a However, in WMA B-BX-BY, the spectral gamma logging data identify seven gamma emitting radionuclides, 137 Cs, 125 Sb, 152 Eu, 154 Eu, 60 Co, 235 U, and 238 U (DOE-GJPO 1998). b The geochemical behaviors of several of these radionuclides, 125 Sb and the two europium isotopes, have not been extensively investigated at the Hanford Site. This task was initiated to assure that our understanding of the geochemical properties affecting the environmental behavior of these radionuclides reflects the current state of knowledge. A literature review was conducted to assess the important oxidation/reduction, aqueous speciation, solubility, and adsorption processes affecting the environmental behavior of antimony, cobalt, europium, technetium, and uranium in vadose zone sediments with low-organic matter content in semi-arid environments such as those at the Hanford Site. Technetium-99 was included in this task because of its importance in the long-term risk calculations. This report presents the results of this literature review.

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Best-basis estimates of solubility of selected radionuclides in sludges in Hanford single-shell tanks

Cited by 4 publications

References 6 publications

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

Characterization of Tank 50 Slurry for Saltstone Waste Acceptance Criteria, April 2007 Samples

Geochemical Factors Affecting the Behavior of Antimony, Cobalt, Europium, Technetium, and Uranium in Vadose Zone Sediments

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