Carbon Steel and Magnesium Oxide Dissolution for H-Canyon Process Applications

Abstract

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 ...

Nylon Dissolution in Nitric Acid Solutions

“…The experiments were designed based on a set of earlier experiments by Pierce 1 involving the dissolution of carbon steel and MgO. During the present work, twelve experiments were performed.…”

“…The Actinide Technology Section of Savannah River National Laboratory recently completed experiments in support of this activity. 1 During earlier work, a flowsheet was developed and the solubility of carbon steel and magnesium oxide (MgO) materials was investigated. Nylon bags will be used to contain materials being transferred to H-Canyon for dissolution.…”

Flowsheet Evaluation for the Processing of U-Mo Materials in H-Canyon

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