Plutonium-containing fuel

The research programme of the European Institute for Transuranium Elements was, from its very beginning, devoted to both basic research on advanced plutonium containing fuel and to fundamental research on actinide elements. Non-fuel actinide research in Europe started more than 20 years ago with the reprocessing of irradiated actinide samples. Since the first isolation and purification of transplutonium elements, actinide research developed steadily in close contact and cooperation with specialised laboratories in Western Europe and in the United States. 

Interest in the so-called sol-gel process for the remote-controlled manufacture of plutonium-containing fuel rods is increasing due to its high safety. In this process a filter cake of freshly precipitated uranium(IV) oxide is converted ultrasonically into a U02-gel, which after drying is fired at 1150°C. The resulting microspheres, 40 to 60 t,m in diameter, are then poured into casing tubes using vibratory techniques. 

The geologic aspects of waste disposal (24—26), proceedings of an annual conference on high level waste management (27), and one from an annual conference on all types of radioactive waste (28) are available. An alternative to burial is to store the spent fuel against a long-term future energy demand. Uranium and plutonium contained in the fuel would be readily extracted as needed. 

Six plutonium containing particles stemming from soil (Marshall Island) were characterized by SIMS, SEM-EDX-WDX and sychrotron radiation by Jernstrom et al. AU the particles were identified as nuclear fuel fragments of exploded weapons components. Since they contained plutonium with a low °Pu/ Pu atomic ratio (less than 0.065), which corresponds to weapons grade plutonium or a detonation with low fission yield, the particles were identified as originating from the safety test and low yield tests conducted on Runit Island. ... 

Nuclear material that can be used for the manufacture of nuclear explosive components without transmutation or further enrichment, such as plutonium containing less than 80% plutonium-238, uranium enriched to 20% uranium-235 and uranium-233 or more any chemical compound or mixture of the foregoing. Plutonium, uranium-233 and uranium enriched to less than 20% uranium-235 contained in irradiated fuel do not fall into this category. 

The zinc distillation process consists of four basic operations to coprocess and recover uranium and plutonium containing fission products from spent FBR mixed-oxide fuels. These operations are ... 

The scraps which arise during the fabrication of plutonium-containing nuclear fuels are collected and stored for some time before they are processed to recover the plutonium. Due to the decay of Pu-241, considerable amounts of Am-241 may build up in the stored material. At the Alkem company, plutonium is recovered from the scrap by anion exchange the americium which is not sorbed on the resin is collected in the combined effluents from the loading and wash steps. The effluents are concentrated by evaporation besides americium, the concentrated effluents contain major amounts of uranium, plutonium, corrosion products, and residues from chemical reagents. A typical composition is given below ... 

Pu. The isotope Pu results from neutron capture in followed by two beta decays. It is the principal isotopic constituent of plutonium formed by the irradiation of low-enrichment uranium. It is the principal flssile corrstituent in plutonium fuel used in thermal and fast reactors. Pu alpha decays, with a half-life of 24,400 years, to form the U parent of the An+3 decay series discussed in Chap. 5. Relatively pure Pu can be made by the short-term low-exposure inadiation of natural uranium. Plutonium containing more than 99 percent Pu results from the irradiation of uranium at fuel exposures of less than 0.7 MWd/kg [K2]. Because of the hi ... 

Moxification of weapons-plutonium diminishes the amount of weapons-grade fissile materials available to potential diversion. A 30 % MOX-loaded reactor has a neutral plutonium output, i.e. plutonium consumption equals plutonium production in the reactor. The difference lies in the quality of the plutonium contained in the fuel after irradiation. 

The fuel elements were Pu-Al alloy rods of 5 w/o Pu content. These rods were 24 In. long and 0.506 in. in diameter. They were clad in 0. 030-in. Zircaloy-2 with 0.020 and 0.1254n. thick end-caps corresponding to a Zr/Pu atomic ratio of 31.92 and an Al/Pu atomic ratio of 168.20. Each r contained about 11 g of Pu. The plutonium contained 5 w/o -240. 

The basic ZPPR fuel consists of rectangular plates of metallic Pu-U-Mo alloy canned in stainless steel. The alloy contains 28.2 wt% Pu, 69.3 wt% depleted U, and 2.5 wt% Mo. The plutonium contains 11.5 at.% Approximately 3000 kg of plutonium are available in this form. This quantity is contained in 18 000 plates. 

Uncertainties in the value of or for in the epithermal energy range have indicated the need for Integral experiments to resolve some of the reported discrepancies/ The experiments. reported in this paper were designed to provide Integral data with clean, well-defined lattices of F -Al rods, 0.600-in. diam, clad in Zircaloy tubes, 0.668-in. o.d. X 0.612-in. l.d. / e plutonium contains 8.79 wt% °Pu. Subcritical lattices are composed of fuel rods in a hexagonal lattice, moderated hy DA and in tanks with radii either 13.0 or 14.8 in. 

At the presmt time no plans exist to modify the container. The container will continue to be used to ship high-enriched powders and plutonium powders if the ne arises. There are no plans to use the container for shipment of plutonium metal fuel plates. 

There are a number of situations where the existence of dilute plutonium with low H/Pu ratios might have to be considered to effectively control criticality. Among these are the dispersion of plutonium in soil, the accumulation of plutonium in fuel processing wastes, and the accumulation in filter materials. These systems may not only have finite critical masses at plutonium concentrations <7 g/liter, but may also contain added scatterers which can reduce the critical masses of the systems to several times less than those of pure plutonium-water systems. 

Verification of the calculations involving 15 wt% Pu and 30 wt% Pu was obtained by calculating keff for a critical array experimentally determined by Bieiman et al. The fuel pins in this experiment were composed of 19.84 wt% Pu in (U,Pu)02, with the plutonium containing 11.5 wt% Pu. The fuel materia) had a diameter of 4.94 mm, was clad in Type 316 stainless steel, and the rods were arranged in a 9.677-mm square lattice. The csdculated value of kerf was... 

The irradiated coated particle fuel discharged from the reactor is very resistant against heat and nitric acid. It is rather difficult to reprocess it. Special mechanical treatment is required and this technology is not widely available. Therefore, the reactor grade plutonium contained in spent FBNR MFEs is less accessible than plutonium from standard LWR spent fuel. 

The Zero-Energy Reactor, Dimple, which was used at Harwell until late 1960, has been extensively modified and rebuilt at Winfirth. Dimple can now be used to study the physics of reactor systems moderated by light or heavy water or by an organic moderator. Containment and monitoring equipment have been provided to permit the use of plutonium-bearing fuels. A wide variety of coarse structures can be built into Dimple ranging from large pressure tube systems to small close packed systems moderated with H2O or H2O/D2O mixtures, which are of interest in the field of marine propulsion. The reactor may be heated uniformly to about 90°C. 

Note The standard core has a veiy conservative design limit of less than 10 at% bum-up and does not contain plutonium bearing fuel. 

A typical 1000 MWe FBR might have a core loading of some 4 tonnes of Pu and 16 tonnes of uranium, with about 25 tonnes of uranium in the blanket. One of the advantages of the fast spectrum is that plutonium containing an appreciable proportion of the higher isotopes Pu " and Pu " is perfectly acceptable as fuel. Indeed, the conversion of to is a... 

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