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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

IMPACT OF NUCLEAR MATERIAL DISSOLUTION ON VESSEL CORROSION

Different nuclear materials require different processing conditions. In order to maximize the dissolver vessel lifetime, corrosion testing was conducted for a range of chemistries and temperature used in fuel dissolution. Compositional ranges of elements regularly in the dissolver were evaluated for corrosion of 304L, the material of construction. Corrosion rates of AISI Type 304 stainless steel coupons, both welded and non-welded coupons, were calculated from measured weight losses and post-test concentrations of soluble Fe, Cr and Ni.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Controlled in-situ dissolution of an alkali metal

A method for the controllable dissolution of one or more alkali metals from a vessel containing a one or more alkali metals and/or one or more partially passivated alkali metals. The vessel preferably comprising a sodium, NaK or other alkali metal-cooled nuclear reactor that has been used. The alkali metal, preferably sodium, potassium or a combination thereof, in the vessel is exposed to a treatment liquid, preferably an acidic liquid, more preferably citric acid. Preferably, the treatment liquid is maintained in continuous motion relative to any surface of unreacted alkali metal with which the treatment liquid is in contact. The treatment liquid is preferably pumped into the vessel containing the one or more alkali metals and the resulting fluid is extracted and optionally further processed. Preferably, the resulting off-gases are processed by an off-gas treatment system and the resulting liquids are processed by a liquid disposal system. In one preferred embodiment, an inert gas is pumped into the vessel along with the treatment liquid.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Safe Dissolution of High Flux Isotope Reactor Cores

The H-Canyon facility at the Savannah River Site is the U.S.A.’s only remaining full- scale chemical separations plant. H-Canyon maintains the capacity to safely and efficiently disposition a large inventory of excess nuclear material from across the Department of Energy (DOE) complex and used nuclear fuel from foreign and domestic research reactors. One such fuel that H-Canyon may dissolve is cores from the High Flux Isotope Reactor (HFIR). By employing realistic analysis, the need for administrative controls was eliminated. A new criticality modeling approach has eliminated the need for administrative controls for HFIR dissolution operations in H-Canyon. The primary upsets of concern are an over-mass event and an overconcentration event. Several initiating events were considered for each type of upset. Over-concentration events were deemed to be not credible by taking credit for the chemistry of acid consumption, i.e. there are not enough moles of acid to dissolve enough moles of uranium in order to reach a critical configuration. Over-mass events were deemed to be not credible by taking credit for the annular design of the fuel elements. By using realistic analysis, both types of upsets have been shown to be subcritical, and therefore administrative controls are not needed to prevent an inadvertent criticality. In this paper, the new methodology for performing criticality analyses for dissolving HFIR fuel elements will be presented, and the elimination of administrative controls will be discussed.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

System and process for dissolution of solids

A system and process are disclosed for dissolution of solids and "difficult-to-dissolve" solids. A solid sample may be ablated in an ablation device to generate nanoscale particles. Nanoparticles may then swept into a coupled plasma device operating at atmospheric pressure where the solid nanoparticles are atomized. The plasma exhaust may be delivered directly into an aqueous fluid to form a solution containing the atomized and dissolved solids. The composition of the resulting solution reflects the composition of the original solid sample.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Dissolution and separation of rare earth metals

A chemical dissolution method is provided for use in recycling rare earth metal-containing material such as permanent magnet material including end-of-life magnet shapes, magnet scrap and Terfenol-D alloy material by mixing the rare earth metal-containing material and an aqueous solution of a copper (II) salt to dissolve the material in the solution. The dissolved rare earth metal is then precipitated from the aqueous solution as a rare earth metal compound, such as a rare earth metal oxalate, sulfate or phosphate from which rare earth metal oxide can be obtained.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Dissolution of Mechanically Mixed UO2-PuO2 and Insoluble Residue Characteristics

During the reprocessing operations of mixed oxide fuel the dissolution step plays a very important role in the attainment of an acceptable plutonium recovery yield. The importance of this step on the overall fuel cycle was recognized by many authors but was especially treated in depth by Lerch [1] and Nicholson [2].

De Regge, P.↗
DOE OSTI2018

Evaluation of the Effects of Microbes on Autunite Dissolution and the Spectral Induced Polarization Response in Hanford Vadose Zone Sediment - 18440

As a result of the U.S. nuclear weapons program during the second World War and throughout the Cold War, there now exists a significant amount of uranium contamination at the U.S. Department of Energy Hanford site located in Washington State. Much of this contamination is in the form of mobile uranyl carbonates species within the vadose zone, which at Hanford varies up to 100 m thick in the Central Plateau. In-situ immobilization of mobile uranium via injections of a soluble sodium tripolyphosphate amendment may prove effective in the formation of low-solubility uranyl phosphate solid phases, autunite. However, the injected polyphosphate undergoes hydrolysis in aqueous solutions to form orthophosphate, which serves as a readily available nutrient for the various microorganisms in the sediment. Sediment-filled column experiments conducted under saturated oxygen restricted conditions using a geophysical technique known as spectral induced polarization (SIP) have shown the impact of microbes on the dissolution of synthetic autunite. Two sets of experiments were conducted using test columns. Each experiment had a pair of columns inoculated with microbes (with a glucose solution acting as a nutrient source) which were monitored using SIP in conjunction with regular sampling of pore-water. Columns were built with two silver/silver chloride (Ag/AgCl) coiled current electrodes at either end and four Ag potential electrodes along the side, which allowed the measurement of three distinct points along the length of the column. SIP measures phase which is the time delay between an injected current and measured voltage, in this case measured in radians. Three sampling ports were added to correspond with the geophysical measurements. Pore-water samples taken over the course of the experiment were analyzed for dissolved elements including uranium, iron, phosphorous, calcium, and magnesium. SIP results were plotted over time in order to determine correlations between changes in electrical phase and changes in pore-water chemistry. It was determined that changes in the phase and bulk resistivity detected with SIP corresponded to changes in the pore-water chemistry due to the growth of microbes. The first experiment ran for five months and had measurements done once a week, the second only ran one month but had measurements taken five times a week in order to understand initial changes in column chemistry in greater detail. SIP may be an effective way to remotely track changes indicative of bacterial activities on the surrounding environment. This method has the potential for field application at a larger scale for the purpose of tracking microbe growth in response to tripolyphosphate amendment. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Fluid Flow, Dissolution, and Mixing Phenomena in Argon-Stirred Steel Ladles

In the current study, the multiphase fluid flow in argon-stirred steel ladles is simulated using an Eulerian–Lagrangian two-phase approach. The momentum source and the turbulent kinetic energy source due to the motion of the bubble are considered for the liquid phase. Argon bubbles are treated as discrete phase particles, and the interfacial forces between the bubbles and the liquid phase; the dependence of the gas density and the bubble diameter on the temperature and the static pressure; and the bubble size distribution are considered. When the fluid flow reaches the quasi-steady state, the ferroalloy melting and mixing phenomena is also modeled. The melting time and the trajectory length of each ferroalloy particle are recorded using a user-defined function (UDF). Local mixing time is predicted in the entire computational domain by checking the mixing criteria in every cell. The effects of gas flow rate, porous plug location, and separation angle of two porous plugs on the fluid flow and the mixing phenomena are investigated. The results show that the flow intensity increases, and the mixing time decreases with the increasing gas flow rate. The optimal porous plug’s radial position with one porous plug is 0.50R for its best mixing condition. When two porous plugs are adopted, the separation angle of 90 deg is recommended to improve the flow field and mixing phenomena.

42 ENGINEERING↗
DOE OSTI2018

Impact of initial CA dissolution on the hydration mechanism of CAC

Usually, for basic investigations on the hydration behaviour of CA (monocalcium aluminate, CaAl{sub 2}O{sub 4}) preferably pure samples without the presence of other hydraulic phases are used. In the presented study we apply an alternative approach investigating mixes that contain tiny to low amounts of CA (0.5–20 wt%) besides CA{sub 2} (CaAl{sub 4}O{sub 7}) or C{sub 6}AF{sub 2} (Ca{sub 6}Al{sub 2}Fe{sub 4}O{sub 15}). The hydration of the mixes is investigated by isothermal heat flow calorimetry, in-situ XRD and pore solution analysis at 23 °C. A modified thermodynamic database enables the calculation of saturation indices for relevant hydrate phases in the investigated systems. CA similarly influences the hydration of both CA{sub 2} and C{sub 6}AF{sub 2} although the exact impact strongly depends on the initial CA/water ratio in the mixes. Up to a certain amount CA is completely consumed during the first minutes after mixing. Beyond this amount the presence of undissolved CA causes an induction period and retards the hydration of CA{sub 2} or C{sub 6}AF{sub 2}.

36 MATERIALS SCIENCE↗