SUMMARYH-Area Operations is planning to process plutonium-contaminated (Pu-contaminated) uranium metal scrap in its efforts to de-inventory excess nuclear materials. The Actinide Technology Section of the Savannah River Technology Center (SRTC) performed flowsheet development to support the processing the scrap in H-Canyon using 2M nitric acid (HNO 3 ) / 0.025M potassium fluoride (KF) and 2 g/L boron. The scrap will be charged to the H-Canyon dissolver via a stainless steel charging bundle with a carbon steel bundle end cap that must dissolve.Experimental work was performed with a range of potential materials to be used to fabricate the bundle end cap to assess their dissolution characteristics in 2M HNO 3 / 0.025M KF and 2 g/L boron. The sample compositions were made of different, unknown types of carbon steel. Experiments also measured the amount of hydrogen gas generated during carbon steel dissolution.Several variables related to carbon steel dissolution have been evaluated using various materials that may be used in the fabrication of a dissolver bundle end cap for plutoniumcontaminated scrap processing. The variables evaluated include sample material, agitation, effect of a coating, and temperature.The dissolution rate data fall into three basic ranges: plate/bar, wire/rivet, and can material. The room-temperature, unstirred dissolution rates were: plate/bar, 0.7-1.7 mg/min-cm 2 ; wire/rivet, 2.1-3.2 mg/min-cm 2 ; uncoated can, 3.4-4.0 mg/min-cm 2 . The difference in rates shows the compositional differences between the samples. Sample hardness data show no correlation to the dissolution rates for the three categories. Calculated densities show that the can materials are clearly different than the plate/bar and wire/rivet materials. These dissolution rates increase by at least an order of magnitude at 100 o C.Stirring can provide a three-to four-fold increase in dissolution rate when compared to static conditions. As carbon steel dissolves, it forms an oxide that does not readily dissolve in the absence of stirring. The accumulation of iron oxide near the dissolution surface diminishes the overall dissolution rate.The effect of tin coatings on the food-pack cans is expected to be minimal. The data show that the coating reduces the initial dissolution rate by about one-third. However, because the coating is very thin, it is removed within a few seconds to a few minutes. Therefore, its effect on the overall dissolution rate of the can will be negligible.Gas generation rates for the dissolution of carbon steel in 2M HNO 3 /0.025M KF and 2 g/L boron reflected those observed for the dissolution of uranium metal. At room temperature, the amount of gas generated was not measurable due to solubility of the reaction products. At 95 o C, the measured gas generation was on the order of 250 mL per gram of carbon steel dissolved. At room temperature and 95 o C, the gases generated are predominantly a mixture of nitric oxide and nitrogen dioxide. Gas chromatography data WSRC-TR-2004-00035, Rev. 0Page 4 demonstrate that ...

SUMMARYH-Canyon has a "gap" in dissolver operations during the last three months of FY03 in which they can dissolve FBLine legacy residues. One group of material to be processed during the gap is pre-existing scrub alloy material received from the Rocky Flats Plant in the early 1980's. There are 14 cans of material containing approximately 3.8 kilograms of plutonium. Of the 14 cans, it was anticipated that four cans contain salts from the Molten Salt Extraction (MSE) process, two cans contain anode heel materials, and eight cans contain scrub alloy buttons.H-Canyon desires to process the materials using a flowsheet similar to the SS&C (sand, slag and crucible) dissolution flowsheet used in F-Canyon. The proposed flowsheet for this material will have a starting nitric acid (HNO 3 ) level of ~3M, an ending acid level of ~ 1.5M, 0.002M mercury, ~2 g/L boron, and 0.15M CaF 2 (calcium fluoride). The materials will be loaded into carbon steel cans and then placed into aluminum metal charging bundles.Samples of 13 items were sent to Savannah River Technology Center (SRTC) for characterization and flowsheet testing --four MSE salts, two anode heels, and seven scrub alloy buttons. SRTC dissolved and characterized each of the samples. Two of them, originally thought to be MSE salts, were found to be graphite mold materials and were unsuitable for processing in H-Canyon. Characterization studies confirmed that the identification of the remaining items as MSE salts, scrub alloy buttons, and anode heel materials was correct.The MSE salts and anode heels solids are comprised primarily of plutonium, potassium, sodium and chloride. The solids dissolve readily in 4M HNO 3 /0.3M HF (hydrofluoric acid) without any noticeable gas generation. Both the MSE salts and anode heels left behind small amounts of residual solids. The scrub alloy buttons are comprised primarily of plutonium and aluminum. The solids dissolve readily with light, effervescent gas generation at the material surface and only trace amounts of NOx generation. Of the seven button samples, four dissolved completely. Two button samples contained small amounts of tantalum that did not dissolve. The last of the seven scrub alloy samples left a trace amount of residual plutonium solids. It is anticipated that the presence of undissolved fissile material is a function of where the sample was located relative to the button surface.Process simulation experiments followed characterization studies. The baseline flowsheet (starting HNO 3 ~3.0M) was tested along with an increased-acid flowsheet (starting HNO 3 ~5.5M) at a 1:10,000 scale. Experiments show that both flowsheets are effective in dissolving the scrub alloy buttons, MSE salts, and anode heel samples. The vigor of the reaction of nitric acid with the items is characterized as a gentle "fizz" at the surface of the scrub alloy button samples with only trace amounts of NOx generation. As a result, the aggressiveness of overall process is determined by the dissolution of the steel cans and aluminum charge bundles. If a st...

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