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5 DEFENSE WASTES
Pages 87-98

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From page 87...
... The 66-million-gallon total volume of waste in the Hanford tanks, and the debate over the appropriate treatment for its conversion to a suitable permanent waste form, make Hanford tank waste a primary focus of current DOE remediation efforts. A major concern about the Hanford tanks has been the possibility that chemical instability of the contents of some tanks could conceivably lead to uncontrolled chemical (not nuclear)
From page 88...
... The Hanford tank wastes pose a challenge for separations (and possible transmutation) , the study of which may supply useful information for the remediation of other defense sites and wastes.
From page 89...
... elements found in the tank wastes typically are precipitated under conditions such as those existing in the tanks, and some radionuclides may have been incorporated into the complex chemical structure of these mineral-like residues formed from nonradioactive elements. The amount of individual radioactive fission products present in the total contents of all the tanks and cribs can be estimated from historical operational power levels of the reactors and the decay-rate constants for each isotopic species.
From page 90...
... DEFENSE WASTES TABLE 5-1 Summary of the Chemical and Radiochemical Inventory of the Hanford Tanks Double-Shell Single-Shell Contaminated Material Type Tank Waste Tank Waste Soil Total Total Volume (m3) 7.8E+04 1.46E+05 1.6E+05 14 9E+05 Density (g/cc)
From page 91...
... DEFENSE WASTES TABLE 5-1 Continued Double-Shell Single-Shell Contaminated Material Type Tank Waste Tank Waste Soil Total NO2 5.0E+06 4.8E+06 5.7E+05 l.OE+07 NO3 1.4E+07 9.7E+07 7.9E+05 l.lE+06 PO4 2.2E+05 8.8E+06 7.0E+04 9.0E+06 SO4 3.8E+05 1.6E+06 2.0E+06 OH l.OE+07 5.3E+06 1.4E+05 1.6E+07 Total Organic Carbon 6. lE+05 2.0E+05 8.8E+04 9.0E+05 Cancrinite 2.7E+06 2.7E+06 Diatomaceous Earth 3.5E+05 3.5E+05 Portland Cement/Concrete 5.7E+04 3.9E+08 Soil 1.6E+08 1.6E+08 Water 6.6E+07 4.5E+07 2.
From page 92...
... Remediation Processing Considerations The complexity of remediating the Hanford tank wastes results not only from the variety of wastes generated by different processing techniques and reagents, but also from the thermal heat arising from fission-product decay energy. It would not be technically prudent to begin the processing needed to produce a suitable permanent waste form before the large majority of short-lived fission product isotopes had decayed to either stable end-products or long-lived isotopes that emit little decay heat per unit time.
From page 93...
... A logical next step toward remediation processing would therefore be to demonstrate pilot-scale sludge washing operations on feedstocks from several typical tanks. This would provide a sufficiently representative sample of sludge residue, which could be analyzed chemically to provide the information needed to evaluate additional chemical process options for separating the actinide fraction from the sludges.
From page 94...
... The diversity of feedstocks from the individual tanks would pose serious technical challenges for any type of vitrification plant, so blending of stocks would be essential. The cost of immobilizing and disposing of the high- and low-level waste fractions with this method (including construction of a vitrification plant, glass canister production over the plant's lifetime, and transportation and fees for geologic disposal)
From page 95...
... than would be possible if the untreated tank contents were vitrified directly. Estimates of the total costs, including sludge washing, LLW disposal, construction of a vitrification plant, glass canister production over the plant's lifetime, and geologic disposal (including transportation and fees)
From page 96...
... " case originally described by the Westinghouse Hanford Co., which includes separation of strontium and technetium (Johnson et al., 1993~. Total costs for that option, including tank processing, LLW disposal, construction of a vitrification plant, glass canister production over the plant's lifetime, and geological disposal (including transportation and fees)
From page 97...
... Both the IFR project scientists at Argonne and the ATW project scientists at Los Alamos agree that application of their transmutation systems to the Hanford tank TRUs may not be justifiable because the small quantity of actinide isotopes involved even in the relatively impure state that would be recovered from a PUREX-type separation could be disposed of through any of the glassingot options. Therefore, the Hanford TRUs- and by extension those from all defense waste sites-can be disposed of with little additional strain on the proposed national repository in vitrified form at considerably less cost than that of any of the proposed transmutation options.
From page 98...
... The primary goals of tank treatment are to mitigate safety concerns and to remove the ~37Cs and 90Sr, which He the major sources of radioactivity in the tanks, thus reducing the amount of HLW for disposal. Separations of the Hanford tank wastes would involve removal or destruction of sodium nitrate and sodium nitrite salts added during processing.


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