Uranium-plutonium mixed oxides

A variant of the HWR is the Eugen reactor developed by Japan. This reactor is heavy water-moderated but lightwater-cooled. It is fueled by mixed uranium—plutonium oxides. 

Program direction will include the study of cross-cutting efforts in both countries dealing with reactor safety, safety issues involving transportation, plutonium vitrification, treatment options, and mixed uranium-plutonium oxide fuel fabrication. The program will also focus attention on safety in the storage, handling, treatment, and disposition of fissile weapons materials. 

MIXED URANIUM/PLUTONIUM Oxide lattice in water 1.0363 Nucl. Tech. 141-145... 

Testing of FAs with mixed uranium-plutonium oxide fuel and other types of nuclear fuel. 

A large size (600—1500 MWei) loop-type reactor with mixed uranium—plutonium oxide fuel and potentially minor actinides, supported by a fuel cycle based upon advanced aqueous processing at a central location serving a number of reactors ... 

The CEFR is a sodium cooled, bottom supported 65 MW(th) experimental fast reactor fuelled with mixed uranium-plutonium oxide (the first core, however, will be loaded with uranium oxide fuel). Fuel cladding and reactor block structural materials are made of Cr-Ni austenitic stainless steel. It is a pool type reactor with two main pumps, and two loops for the primary and secondary circuit, respectively. The water-steam tertiary circuit has also two loops, with the superheated steam collected into one pipe that is connected with the turbine. CEFR s has a natural circuit decay heat removal system. 

Uranium and mixed uranium—plutonium nitrides have a potential use as nuclear fuels for lead cooled fast reactors (136—139). Reactors of this type have been proposed for use ia deep-sea research vehicles (136). However, similar to the oxides, ia order for these materials to be useful as fuels, the nitrides must have an appropriate size and shape, ie, spheres. Microspheres of uranium nitrides have been fabricated by internal gelation and carbothermic reduction (140,141). Another use for uranium nitrides is as a catalyst for the cracking of NH at 550°C, which results ia high yields of H2 (142). 

Plutonium Dioxide in Molten Equimolar Sodium-Potassium Nitrate. The behavior of plutonium dioxide in molten alkali metal nitrates is an area of major concern. Claims that alkali metal plutonates are formed (1, 2, 3, 5, 6) are not substantiated by definitive analytical results. In some cases (5, 6), sodium peroxide was added as an oxidant to either an alkali metal nitrate melt (6) or to an alkali metal hydroxide melt (5). If the temperature is great enough, for example above 700°C, thermal decomposition of the nitrate melt produces peroxide species. Other studies (4, , 12, 17) do not claim formation of a plutonate species, but only state that an insoluble plutonium-containing compound exists. However, in all the references cited, the results were given for mixed uranium-plutonium dioxide definitive analytical results were not given. 

Mixed Uranium-Plutonium Dioxide in Equimolar Sodium-Potassium Nitrate. The behavior of two compositions of mixed uranium-plutonium dioxide has been investigated thus far at PNL. The first composition, designated material A, consists of 5.44% Pu02/94.56% UO2. The second composition, designated material B, consists of 27.56% Pu02/72.44% UO2. Both materials were acquired as pellets that had been sintered at 1700°C. The behavior of both mixed-oxide materials was studied under the same conditions used in the previous experiments. 

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. 

The capability of fissile self-sustainable regime (core breeding ratio 1) in a closed nuclear fuel cycle with mixed uranium-plutonium fuel (oxide or nitride) ... 

Stanley JA, Edison AF, Mewhinney JA. 1982. Distribution, retention and dosimetry of plutonium and americium in the rat, dog and monkey after inhalation of an industrial-mixed uranium and plutonium oxide aerosol. Health Phys 43(4) 521-530. 

MOX [Mixed OXides] A process for making mixed uranium and plutonium oxides for use as a nuclear fuel. Developed for the Thorp plant in Cumbria, UK. 

Tokai, K. Ooe, A. Manufacture of mixed oxide (MOX) pellets containg uranium oxide and plutonium oxide for fuel rods for power generation. JP 94-225519, Chem Abstr. 1996, 124, 272906. 

The projections are based on a recent forecast (Case B) by the Energy Research and Development Administration (ERDA) of nuclear power growth in the United States (2) and on fuel mass-flow data developed for light water reactors fueled with uranium (LWR-U) or mixed uranium and plutonium oxide (LWR-Pu), a high temperature gas-cooled reactor (HTGR), and two liquid-metal-cooled fast breeder reactors (LMFBRs). Nuclear characteristics of the fuels and wastes were calculated using the computer code ORIGEN (3). 

The most important fuel for currently operated nuclear power stations (mainly light-water reactors) is - U-enriched uranium(IV) oxide. Also of importance are metallic uranium for the Magnox reactors and a few research reactors and uranium-plutonium mixed oxides for light-water reactors. Fuel production comprises extraction and dressing of uranium ores to uranium concentrates, conversion into UF, the uranium compound used for enrichment of the BSy.jjjotope, enrichment of and production of fuel from enriched UF5 (reconversion). 

Uranium-plutonium mixed oxides Uranium-plutonium mixed oxides (MOX) are becoming increasingly important, since plutonium is produced during the reprocessing of spent fuel elements. In these mixed oxide fuel elements a mixture of uranium(IV) and plutonium(IV) oxides with a plutonium content of 3 to 4% is utilized instead of ca. 4% 235u-enriched uranium(IV) oxide. Such fuel elements have similar nuclear physical properties to the standard elements with and can therefore be used in their place. 

In their manufacture uranium(IV) oxide is mixed with the appropriate quantity of plutonium(IV) oxide, the mixture pressed into pellets and then sintered (termed coprocessing in the USA). Uranium(IV) oxide is produced by one of the above-described processes and plutonium(IV) oxide from the aqueous nitrate solution produced during reprocessing by precipitating it as plutonium oxalate and calcining the oxalate. 

The fuel is dissolved during reduction of the mixed oxides by calcium. This oxide reduction operation is done in the presence of a CaCl2-CaF2 salt and a Cu-Mg alloy. The FP-2 elements and the CaO reaction product are taken up by the salt and the reduced uranium, plutonium, FP-3, and FP-4 elements are taken up by the alloy. Uranium is present in excess of its solubility limit and precipitates as the UCu5 intermetallic compound. 

Other analytical problems to which the direct comparison method has been applied include the determination of mixed iron oxides in the oxide scale on steel [14.10], the beta phase in titanium alloys [14.11], and mixed uranium and plutonium carbides [14.12]. 

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