Hanford and Savannah River

Salts of actinides are very common in waste streams. In particular, nitrates, chlorides, and sulfates are found in tank waste streams that were formed by neutralization of highly acidic solutions at several DOE sites, such as Hanford and Savannah River. The aqueous solubility of these salts is very high, and hence, it is a challenge to stabilize them. As we shall see in case studies, the CBPC matrix has good promise in handling these waste streams. 

Ceramicrete stabilization of Tc, partitioned from high-level tank wastes, was demonstrated by Singh et al. [11]. The waste stream was a product of a complexation-elution process that separates Tc from HLW, such as supernatant from salt waste tanks at Hanford and Savannah River. A typical waste solution generated during the complexation-elution process contains 1 M NaOH, 1 M ethylenediamine, and 0.005 M Sn +. 

Unlike Portland cement, the Ceramicrete slurry sets into a hard ceramic even in the presence of salts such as nitrates and chlorides hence, the Ceramicrete process has a great advantage over conventional cement technology with respect to the stabilization of some difficult waste streams, such as those from Hanford and Savannah River tanks. Wagh et al. demonstrated this advantage in several studies, wherein they produced monolithic Ceramicrete solids by using concentrated sodium nitrate and sodium chloride solutions in place of water to stabilize the waste streams. Details of some of these studies may be found in Ref. [21]. 

The studies on separation of water isotopomers (HTO, HDO, H2O) with membranes from poly[bis(phenoxy)phosphazene] and carboxylated derivatives were carried on in Pacific Northwest Laboratory [112,113]. Using these membranes tritiated water was extracted from fuel storing pool water of 3 pCi/L concentration of tritium, and from facilities under supervision of US DOE in Hanford and Savannah River. Separation with 10,800 pCi/L tritiated water obtained by membrane method was not higher than 33% (depletion in the permeate fraction). Water containing 3 pCi/L of HTO was depleted by 22% in a similar system [113]. 

Accurate properties prediction for radionuclides, including actinides and lanthanides, to understand their migration in the vadose zone (e.g., the Hanford site), and their chemical behavior in waste tanks (e.g., Hanford and Savannah River)—such chemical reactivity information is needed for detailed subsurface and groundwater reactive transport models. 

Reduction with ferrous ion was the reaction used in the first Purex flow sheets, at Hanford and Savannah River. The specific reductant used was ferrous sulfamate Fe(S03NHj)j, a compound selected because it stabilized ferrous ion against oxidation in a nitric acid-nitrous acid system. The process was satisfactory in all respects except its addition of extraneous, nonvolatile components to the wastes. 

The most important consideration in tank design is minimization of corrosion. Originally two storage philosophies were believed to be equally safe in this respect (1) neutralized waste in mild steel tanks and (2) acid waste in stainless steel tanks. Almost three decades of experience have proved that only the latter satisfies all safety requirements. No leakage from stainless steel tanks has become known, whereas 20 out of 183 mild steel tanks at the Hanford and Savannah River sites developed leaks [L2]. It is now generally accepted that a minimum conosion rate can be maintained with suitable types of stainless steel and nitric acid concentrations in the range of 2 to 4 Af. If the HNO3 concentration falls below 1 M stress corrosion due to chloride ions may be promoted. 

Soils may become contaminated from fallout associated with nuclear weapons tests, such as those conducted at the Trinity Site in southern New Mexico, the Pacific Proving Ground at the Enewetak Atoll, and the Nevada Test Site or with accidental, non-nuclear detonation of nuclear weapons, such as occurred at Palomares, Spain. Research facilities, such as the Los Alamos National Laboratory, Los Alamos, New Mexico, may release treated radioactive wastes under controlled conditions. Production facilities, such as the Hanford and Savannah River Plants and experimental reactor stations, for example, the Idaho National Engineering Laboratory, Idaho Falls, Idaho, also released treated plutonium-bearing radioactive wastes under controlled conditions to soils (Hanson 1975). 

An overview is given of plutonium process chemistry used at the U. S. Department of Energy Hanford, Los Alamos National Laboratory, Rocky Flats, and Savannah River sites, with particular emphasis on solution chemistry involved in recovery, purification, and waste treatment operations. By extrapolating from the present system of processes, this paper also attempts to chart the future direction of plutonium process development and operation. Areas where a better understanding of basic plutonium chemistry will contribute to development of improved processing are indicated. 

Large-scale plutonium recovery/processing facilities originated at Los Alamos and Hanford as part of the Manhattan Project in 1943. Hanford Operations separated plutonium from irradiated reactor fuel, whereas Los Alamos purified plutonium, as well as recovered the plutonium from scrap and residues. In the 1950 s, similar processing facilities were constructed at Rocky Flats and Savannah River. 

In the United States these sites are in Hanford, Washington, and Savannah River, Georgia. 

One of the primary waste disposal problems of the world is that of radioactive materials. At present, the U.S. nuclear wastes are stored in solution at Hanford, Washington, and Savannah River, Georgia. These wastes are divided into two types of materials. The high-level radioactive waste are absorbed into porous solids and transported to permanent depositories within mountains. 

Because of these accidents laboratory studies were made at Hanford [Wl] and Savannah River [Cll, N5] to determine the conditions under which nitric acid solutions possibly containing TBP could be safely evaporated. Wagner [Wl] reported that a red oil formed by extended refluxing of a concentrated aqueous solution of uranyl nitrate, nitric acid, and TBP decomposed autocatalytically when heated to 150°C. Nichols [N5] found that a mixture of... 

Special campaigns for recovering neptunium from Purex solutions have been run at Oak Ridge [F4], Hanford [D3], Savannah River [P7], Windscale [Nl], and Marcoule [C6]. None of these sought complete recovery. A brief description will be given of the first three. 

Nuclear weapons production and testing facilities (Hanford, WA, Savannah River, GA, Rocky Flats, CO, and The Nevada Test Site, in the United States, and Mayak in the former Soviet Union), also released small amounts. The releases occurred in accidents with nuclear weapons, the reentry of satellites that used Pu-238, and by the Chernobyl nuclear reactor accident. 

An improved solvent extraction process, PUREX, utilizes an organic mixture of tributyl phosphate solvent dissolved in a hydrocarbon diluent, typically dodecane. This was used at Savannah River, Georgia, ca 1955 and Hanford, Washington, ca 1956. Waste volumes were reduced by using recoverable nitric acid as the salting agent. A hybrid REDOX/PUREX process was developed in Idaho Falls, Idaho, ca 1956 to reprocess high bum-up, fuUy enriched (97% u) uranium fuel from naval reactors. Other separations processes have been developed. The desirable features are compared in Table 1. 

The Bush Administration (1989-1993) had a similar free marketplace philosophy as Reagan, hut faced the daunting task of having to start directing billions toward cleaning up after forty years of neglect at the contaminated weapons complex, particularly the federal facilities at Savannah River South Carolina, Hanford Washington, and Rocky Flats Colorado. The cleanup plan was fourfold characterize and prioritize all waste cleanups at departmental sites, con-... 

The advanced integrated solvent extraction and ion exchange systems are designed for the chemical pretreatment of waste retrieved from storage tanks at Department of Energy (DOE) sites (e.g., at INEL, Hanford, Savannah River). 

Over 5001 of HLW have been vitrified in France and Germany. In the USA, the HLW at the Nuclear Fuel Services plant in West Valley Plant, New York, have been vitrified (300 two-ton canisters) and vitrification is ongoing at the Defense Waste Processing Facility (DWPF) at Savannah River, South Carolina 1600 canisters by February 2004). A vitrification plant is under construction at Hanford, Washington. Vitrification of all of the HLW in the USA will generate approximately 20 000 canisters, which are destined for disposal at the geological repository at Yucca Mountain. 

Other multiphase ceramics. Numerous multiphase ceramic formulations for conditioning of various wastes have been designed (Harker 1988). These so-called tailored ceramics were developed for immobilization of complex defence wastes at the Savannah River Plant and Rockwell Hanford Operation (Harker 1988). Tailored ceramics include ACT and REE hosts (fluorite-structure solid solutions, zirconolite. 

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