Plutonium Oxide Powders

Pu02 powders readily exchange atmospheric moisture and carbon dioxide, particularly on their surface. With the precautions described below, the shipper s and the receiver s data were in 

These vessels can be small glass tubes, like the inserts of the BC4 and BC5 brass containers (O Fig. 63.12), whenever one can use a Type B package carrying several grams of plutonium to ship a load of samples. These containers were actually designed and qualified for use with the PAT2 container, which had received approval for the shipment of Type B quantities of Pu samples to or from the USA (Kuhn et al. 1982). Their compact size make them very attractive for shipments of gram size Pu samples in any Type B container. 

BC5 and BC4 brass vials with glass tube insert (IAEA 2004] 

In other cases, the subsamples are dissolved in nitric acid in the operators analytical laboratory. An aliquant of each subsample, carrying about 4 mg of plutonium, is taken into a 5 ml penicillin vial and dried carefully to form an adherent film of nitrate salt on the bottom of the vial. The two aliquants are intended for elemental assays. Another fraction of at least one subsample is usually prepared for isotopic analysis and dried as above. With current products issued from high burnup spent fuel, some 20 penicillin vials could be packed together into a single Type A container and flown to SAL. 

Uranium scrap materials in cans or hoppers are expected to be heterogeneous in element concentration and isotopic composition, and tend to change in composition upon exposure to atmosphere. As far as possible, the content of the container to be verified should be carefully mixed just before sampling. The item is weighed on a suitable scale immediately before duplicate samples of relatively large size are taken by collecting material firom various spots in the bulk of the material. 

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Emission spectrography is used to determine the content of impurities in samples of uranium and plutonium oxide powders and pellets. 

Milling. Both processes involve milling. The milling requirement of PUO2 particulates for the ceramic process is less than 20 pm, which is comparable to the 10 pm nominal requirement for the MOX fuel process. For plutonium oxide, particulate less than about 3 pm (corresponding to an aerodynamic equivalent diameter of 10 pm) are respirable. Thus under similar conditions, the potential inhalation dose associated with a spill accident of plutonium oxide powder for the ceramic process is no worse than that for the MOX fuel process. 

Spill of Pu oxide powder. Spills of plutonium oxide powder by human error or equipment failure are always a safety concern. Examples are dropping a container containing Pu oxide, or leaky seals in the Pu oxide process system. Adequate protection systems to protect against accidental spills or leakage are mandatory. 

The Coulter principle is also standard for dry toners [8,9] and an accepted method for aluminum oxide powder [10], chromatography media [11], polymeric powders [12], plutonium [13], filter evaluation [14], catalytic material [15] and comparing particle size distribution using alternative types of particle counters [16]. In ASTM method C-21 it states that the experience of several laboratories indicates that the method is capable of a repeatability of 1% and a reproducibility of 3% at the 95% confidence level. Operating procedures for this technique are also covered in BS3405 [17]. The method is also the subject of an international standard [18]. 

The conceivable option of using oxide powder (whether of uranium or plutonium) directly, with no postacquisition processing or fabrication, would seem to be the simplest and most rapid way to make a bomb. However, the amount of material required would be considerably greater than if metal were used. 

The plutonium canister assay system (PCAS) determines the content of plutonium in MOX and pure oxide powders in cans contained in a specific transport container (four cans per canister) (Menlove et al. 1986). The system can be integrated into an operator s material handling system and continuous measurement cycles are performed, which are evaluated at the end of a given collection period. Thereby, continuous verification of the flow of canisters can be performed without inspectorate intervention. For inventory verification, an inspector provides an electronic list of canisters to be verified and the operator transfers the selected... 

The contractual end product for uranium is the nitrate solution. If a utility wants to re-use it, it has to be converted to the hexavalent form or to the oxide form, which can be used in MOX fuels, but, in general, it is more attractive to use natural or depleted manium. The plutonium cannot be economically stored in the nitrate form because critical masses or concentrations in aqueous solutions can become very small. For this reason, the plutonium solution is converted to oxide powder by treating it with a hot oxalic acid, causing the plutonium to precipitate as Pu(lV) oxalate. When dried, it is calcined while modestly annealed, the product being Pu(lV) oxide (PUO2). This is weighed (with a typical uncertainty of 0.1%) and put in storage containers. 

Mhere materials are labelled with an asterisk, a large number of powders were successfully deposited using the suspension medium described. Mizuguchi et al included alumina barium, strontium and calcium carbonates magnesia, zinc oxide, titanium dioxide, silica, indium oxide, lanthanum boride, tungsten carbide, cadmium sulfide and several metals and phosphors. The list of materials described by Gutierrez et al included several metals carbides of molybdenum, zirconium, tungsten, thorium, uranium, neptunium and plutonium zirconium hydride, tantalum oxide and uranium dioxide. In addition, many metallic and oxide powder suspensions in alcohols, acetone and dinitromethane were studied by Brown and Salt ... 

The Oak Ridge technique employs Ti02 powder to adsorb Pu(V). This procedure has been used to characterize the oxidation state of plutonium in Pond 3513 as predominantly Pu(V). 

The very chemically reactive plutonium hydride is usually decomposed in a vacuum-tight furnace capable of attaining a temperature of 700°C. Plutonium hydride that is decomposed under vacuum at temperatures below 400°C forms a very fine (<20y) metallic powder above 500°C the powder begins to sinter into a porous frit which melts at 640°C to form a consolidated metal ingot. This metal typically contains significant oxide slag but is suitable for feed to either molten salt extraction or electrorefining. 

The skull metal and oxide are first completely burned to oxide by heating in air to 400-500°C. The plutonium metal spontaneously burns and is collected as a green Pu03 powder. This oxide is recycled back as feed for Direct Oxide Reduction. This process is normally 100% efficient with only a small plutonium residue showing up in items such as clean-up rags. 

Several incidents in which moisture has contributed to fires or explosions, in some of which water was definitely the sole oxidant, in zirconium, magnesium, uranium and thorium scraps or powders are retailed, largely sourced from an earlier paper. However, a plutonium fire was extinguished with water. 

The mixed oxide (U,Pu)02 can be prepared by adding ammonia to a mixed nitrate solution of plutonium(IV) nitrate and uranyl nitrate. The precipitate, which consists of Pu(OH)4 and (NH4)2U207, is converted to (U,Pu)02 by heating in hydrogen at 500-800°C. Typical conditions for the preparation of PUO2 and PUO2-UO2 powder are listed in Table 2. ... 

The extended radiation time for the domestic fuel increases the quantity of fission products and the higher actinides. Pure plutonium product poses nuclear weapons proliferation risk and is the primary reason reprocessing is not practiced in the United States. The modified PUREX process has been practiced on an industrial scale in Europe and supports the production of mixed uranium-plutonium fuel. Blended UO2 and PUO2 powder is compacted and sinter to form the mixed oxide (MOX) fuel pellets much like the enriched UO2 fuel. Natural and depleted uranium can be used to prepare MOX fuel and is the demonstrated option to recover fuel values from spent fuel. 

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