Ferrocyanide safety program cyanide speciation studies FY 1993 annual report

Bryan, S.A.; Pool, K.H.; Bryan, S.L.; Sell, Rachel L.; Thomas, Lothar

doi:10.2172/10137423

Cited by 12 publications

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“…The en/EDTA solvent dissolved all of the IF-lB starting material, while the NaOH solution did not. As previously discussed, aqueous NaOH does not dissolve "Cs,NiFe(CN)," or other phases containing cesium (Bryan et al 1993;Lilga et al 1993), and this insoluble phase also prevents dissolution of a fraction of the Na,NiFe(CN), phase. The AA analytical results for iron correspond to soluble ferrocyanide ion.…”

Section: Materials and Methodologymentioning

confidence: 84%

Ferrocyanide safety project ferrocyanide aging studies FY 1995 annual report

Lilga¹,

Alderson²,

Hallen³

1995

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SummaryThis annual report gives the results of the work conducted by the Pacific Northwest Laboratory in FY 1995 on Task 3 of the Ferrocyanide Safety Project, Ferrocyanide Aging Studies. Aging refers to the dissolution and hydrolysis of simulated Hanford ferrocyanide waste in alkaline aqueous solutions by radiolytic and chemical means. The ferrocyanide simulant primarily used in these studies was driedIn-Farm-lB, Rev. 7, prepared by Westinghouse Hanford Company to simulate the waste generated when the In-Farm flowsheet was used to remove radiocesium from waste supernates in single-shell tanks at the Hanford Site. In the In-Farm flowsheet, nickel ion A d ferrocyanide anion were added to waste supernates to precipitate sodium nickel ferrocyanide, Na,NiFe(CN),, and co-precipitate radiocesium. Once the radiocesium was removed, supernates were pumped from the tanks, and new wastes from cladding removal processes or from evaporators were added. These new wastes were typically highly caustic, having hydroxide ion concentrations of over 1 M and as high as 4 M. The Aging Studies task is investigating reactions this caustic waste may have had with the precipitated ferrocyanide waste in a radiation field.In previous Aging Studies research, N%NiFe(CN), in simulants was shown to dissolve in basic solutions, forming insoluble Ni(OH), and soluble Na,Fe(CN),. The influence on solubility of base strength, sodium ion concentration, anions, -and temperature was previously investigated. Destruction of ferrocyanide anion by hydrolysis to form ammonia and formate ion was found to be promoted by gamma irradiation. Increasing temperature and gamma dose rate increased the rate of hydrolysis, as indicated by the amount of ammonia formed with time. Ammonia was found to be radiolyzed in the gamma field. The change in concentration of formate ion generally paralleled that of ammonia but was three to four times less concentrated. Total soluble iron concentrations were found to decrease in what appeared to be a pseudo-first-order fashion. The nickel concentration tended to increase, sometimes to 90% redissolution. Aluminum added to the hydrolysis solution had relatively little effect and may have slightly promoted hydrolysis.. In FY 1995 Aging Studies work, temperature and gamma dose rate effects were further investigated. Consistent with prior work, as the temperature or the gamma dose rate increased, the rate of hydrolysis also increased. As an approximation, ammonia production with time was described as being linear. Rate constants for ammonia production followed a linear Arrhenius relationship and also increased linearly with increasing applied gamma dose rate. Rate constants for ammonia production at other conditions could be predicted with use of the temperature and dose rate relationships.Ammonia was found to be destroyed in the gamma environment. Rate constants of 1.1 x Mlday at an applied dose rate of 1.07 x l@ Rad/h, and 2.1 x lo4 Mlday at 8.91 x 103 Rad/h were measured for this process. Formate ion destruction was found to occur at...

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Section: Materials and Methodologymentioning

confidence: 84%

Ferrocyanide safety project ferrocyanide aging studies FY 1995 annual report

Lilga¹,

Alderson²,

Hallen³

1995

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“…The In-Farm-2 simulant preparation included a small amount of cesium nitrate, indicating that either Cs,NiFe(CN), or NaCsNiFe(CN), would exist in the sludge. The dissolution solution used in this experiment will dissolve both the sodium and cesium fbrm of nickel ferrocyanide (Bryan et al 1993). Thus, the measured concentration of N+NiFe(CN), in the In-Farm-2 sludge will be approximately 2.5% to 5% high (as discussed in the previous paragraph).…”

Section: Results Of Fitr Determination Of Nanife(cn) Content In Simmentioning

confidence: 99%

“…Appropriate amounts of NhFe(CN), 10 H,O were dissolved in 25.0 g of dissolution reagent (Bryan et al 1993). The dissolution reagent consisted of 5% EDTA and 5% ethylenediamine in deionized water.…”

Section: Cyanide Filr Standardsmentioning

confidence: 99%

Ferrocyanide tank safety program: Cesium uptake capacity of simulated ferrocyanide tank waste. Final report

Burgeson¹,

Bryan²

1995

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DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document.The objective of this project is to determine the capacity for 137Cs uptake by mixed metal ferrocyanides present in Hanford Site waste tanks, and to assess the potential for aggregation of these '37Cs-exchanged materials to form "hot-spots'' in the tanks. This research, performed at Pacific Northwest Laboratory (PNL) for Westinghouse H a r d Company, stems from concerns regarding possible localized radiolytic heating within the tanks. After ferrocyanide was added to 18 high-level waste tanks in the 1950s, some of the ferrocyanide tanks received considerable quantities of saltcake waste that was rich in '37Cs. If radioactive cesium was exchanged and concentrated by the nickel ferrocyanide present in the tanks, the associated heating could cause tank temperatures to rise above the safety limits specified for the ferrocyanide-containing tanks, especially if the supernate in the tanks is pumped out and the waste becomes drier.For this study, two simulants, In-Farm-2 and U-Plant-2, were chosen to represent the waste generated by the cesium scavenging process. These simulants were formulated using protocols from the original cesium scavenging campaign. The effects from later additions of cesium-rich waste from various processes were also considered. The simulants were prepared and centrifuged to obtain a moist ferrocyanide sludge. This moist sludge was then used in three different sets of experiments: 1) batch equilibrium testing, 2) layering tests, and 3) intercalation of excess dissolved cesium into the settled sludge.The batch equilibrium testing was performed at room temperature to examine the effects of cesium and the cesium-to-nickel ferrocyanide ratio on the distribution coefficients 0. The maximum capacities of U-Plant-2 and In-Farm-2 simulants were also determined from these experiments. The maximum capacity of U-Plant-2 simulant was 0.50 mole of cesium per mole of nickel ferrocyanide and the maximum capacity of In-Farm-2 simulant was 0.80 mole of cesium per mole of nickel ferrocyanide. An evaluation of the effects of the sodium concentration and the sodium-to-cesium ratio indicated a slight but noticeable decrease in the distribution coefficients as the concentration of sodium was increased.Potential concentration mechanisms were also evaluated. A concentrated region of '"Cs nickel ferrocyanide could form in several ways, depending upon the settling and intercalation characteristics of the materials: 1) after exchange of cesium from solution, the cesium form of the nickel ferrocyanide could settle at a different rate than the sodium form of nickel ferrocyanide; 2) after exchange of cesium from solution, the cesium nickel ferrocyanide could settle at a different rate than the remaining solids present in the bulk of the waste (sodium salts). This concentration mechanism assumes a large portion of the nickel ferrocyanide exists as cesium nickel ferrocyanide. A concentr...

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“…Appropriately, the iron, cesium, and nickel concentrations in the NaOH solution were found to be lower than in the en/EDTA solution. As discussed in more detail below, aqueous NaOH does not dissolve "CS@iFe(CN)6" or other phases containing cesium (Bryan et al 1993;Lilga et al 1993), accounting for the different concentrations in the two media. The extent of dissolution (solubility) as a function of temperature was determined because aging experiments were conducted at elevated temperatures.…”

Section: Materials and Methodology For Hydrolysis Studiesmentioning

confidence: 99%

“…The lower rates and solubilities were more likely due to an accumulation of cesium at the particle surface, forming an insoluble phase. As cesium accumulation increases, the composition of this phase would tend to approach that of FECN-14, containing CGNiFe(CN),, which was found to be insoluble in up to 4 M NaOH (Bryan et al 1993;Lilga et al 1993). …”

Section: Dissolution (Total Dissolved Iron Concentration) As a Functimentioning

confidence: 99%

Ferrocyanide safety project ferrocyanide aging studies. Final report

Lilga¹,

Hallen²,

Alderson³

1996

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SummaryThis final report gives the results of the work conducted by Pacific Northwest National Laboratory (PNNL) from FY 1992 to FY 1996 on the Ferrocyanide Aging Studies, part of the Ferrocyanide Safety Project. The Ferrocyanide Safety Project was initiated as a result of concern raised about the safe storage of ferrocyanide waste intermixed with oxidants, such as nitrate and nitrite salts, in Hanford Site single-shell tanks (SSTs). In Numerous studies conducted by the Task Team defmed safety criteria and resulted in closure of the USQ in March 1994. The potential for ferrocyanide reactions in Hanford Site SSTs was evaluated, and the energy released during these reactions was quantified. Dynamic X-ray diffraction was also used to identify specific reactions and to quantify reaction rates. In addition, a number of experimental and theoretical studies were conducted in an effort to analyze the thermal characteristics of the tanks and to investigate the likelihood of "hot spots" forming as a result of radiolytic heating.Resolving the Ferrocyanide Safety Issue requires that tank contents meet the safety criteria and operations be conducted such that waste conditions fall within the criteria limits. Because the ferrocyanide sludge has been exposed for many years to other highly caustic wastes, as well as to elevated temperatures and both gamma and beta radiation, ferrocyanide decomposition has occurred in the tanks. As a result, the concentration of ferrocyanide is less than that predicted by tank inventory records. As such, C-Farm tanks have been re-categorized as safe, allowing resolution of the Ferrocyanide Safety Issue for these tanks. In the PNNL studies, ferrocyanide waste simulants were used instead of actual waste. The simulants used in these studies were primarily In-Farm simulants, prepared by WHC to mimic the waste generated when the In-Farm flowsheet was used to remove radiocesium from waste supernates in the SSTs. In the In-Farm flowsheet, nickel ion and ferrocyanide anion were added to waste supernate to precipitate sodium nickel ferrocyanide and co-precipitate radiocesium. Once the radiocesium was removed, supernates were pumped from the tanks and disposed to the ground via cribs. Later, new wastes from cladding removal processes and/or from evaporators were added.These new wastes were typically highly caustic, having hydroxide ion concentrations of over 1 M and as high as 4 M. The Aging Studies investigated possible reactions between this caustic waste and the precipitated ferrocyanide waste in a radiation field.Over a 5-year period, these studies demonstrated and characterized the aging of ferrocyanide waste simulants through dissolution and hydrolysis processes. The experiments show the ultimate products are ammonia (which is slowly radiolyzed), carbonate, and oxides or hydroxides of iron and nickel. Thus, most of the fuel value in the solid phase is consumed in the process. Any ferrocyanide tank waste that contacted highly caustic waste also would undergo similar aging processes. The rate of agi...

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Ferrocyanide safety program cyanide speciation studies FY 1993 annual report

Cited by 12 publications

References 0 publications

Ferrocyanide safety project ferrocyanide aging studies FY 1995 annual report

Ferrocyanide safety project ferrocyanide aging studies FY 1995 annual report

Ferrocyanide tank safety program: Cesium uptake capacity of simulated ferrocyanide tank waste. Final report

Ferrocyanide safety project ferrocyanide aging studies. Final report

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