Slightly enriched uranium

The Hanford N Reactor. The Hanford N reactor was built in 1964 for purposes of plutonium production during the Cold War. It used graphite as moderator, pierced by over 1000 Zircaloy 2 tubes. These pressure tubes contained slightly enriched uranium fuel cooled by high temperature light water. The reactor also provided 800 MWe to the Washington PubHc Power Supply System. This reactor was shut down in 1992 because of age and concern for safety. The similarity to the Chemobyl-type reactors played a role in the decision. 

In the Purex process, plutonium and uranium are coextracted into an organic phase and partitioned by reducing plutonium(IV) to the aqueous-favoring plutonium(III). This has been achieved chemically by use of a suitable reductant such as ferrous sulfamate ( 1) or uranium(IV). (2, 3, 4, 5) The use of ferrous sulfamate results in accelerated corrosion of the stainless steel, due to the presence of ferric ions and sulfuric acid, and in an increase in the volume of wastes. The use of natural uranium(IV) can cause dilution of the 235U in slightly enriched uranium, thus lowering the value of the recovered uranium. 

In thermal-neutron reactors has an important advantage over or Pu in that the number of neutrons produced per thermal neutron absorbed, tj, is higher for than for the other fissile nuclides. Table 6.1 compares the 2200 m/s cross sections and neutron yields in fission of these three nuclides. Thorium has not heretofore been extensively used in nuclear reactors because of the ready avaUabihty of the U in natural or slightly enriched uranium. As natural uranium becomes scarcer and the conservation of neutrons and fissile material becomes more important, it is anticipated that production of U from thorium will become of greater significance. 

The Purex process has become the process quite generally used for reprocessing slightly enriched uranium fuel from power reactors. For this reason, it will be described in more detail in this chapter than other fuel separation processes. 

Plant data Slightly enriched uranium is to be reprocessed with a bumup of 30,000 MWd/MT uranium and a specific power of 30 MW/MT uranium. 

The number of structural materials available for use in reactor applications is limited. The most stringent requirement is a low thermal neutron capture cross section. Among common materials, only aluminum has a sufficiently low cross section to permit its extensive use in reactors using natural or slightly enriched uranium as fuel. The need for other materials, particularly for use at elevated temperatures, resulted in the development of reactor grade zirconium and zirconium alloys. 

The Eurochemic reprocessing plant, erected by a consortium of 13 European member states of the OECD/NEA, was in active operation between 1966 and 1974. During these campaigns, 181.5 tons of natural and slightly enriched uranium fuels and 30.6 tons of highly enriched aluminum alloy fuels from material testing reactors were reprocessed. 

Since 1995 a progressive loading with slightly enriched uranium (0.85% wt) began, so that at present the core contains not only natural uranium fuel elements but also slightly enriched ones. 

CANDU 3 uses the standard 37-element CANDU fuel bundle (Figure 5.8. IB). This fuel bundle is a very simple, easily-fabricated structure about 500-mm long and 100 mm in diameter. Current CANDU plants operate with natural uranium fuel (0.7% U235) they can, however, operate on a variety of other low fissile content fuels including slightly enriched uranium, and recovered uranium from PWR fuel reprocessing plants. 

The bucklings were calculated using pubUshed reflector savings values for slightly enriched uranium. 

Reactivity Measurements on ikiperturbed. Slightly Enriched Uranium Dioxide Lattices,, A.L. MacKinney R. M. Ball (B is fV. Uniform lattice critical experiments with... 

D. Kein, A. Z. Kranz, G. G. Smith, W.Baer, and J. De-Juren, Measurements of Thermal Utilization Resonance Escape Probability and Fast Effect in Water-Moeferated, Slightly Enriched Uranium and Uraniuni Oxide Lattice, J. Nuc, Sci, and Eng., 3 403. ... 

A. Z. kranz, Measurements of Thermal Utilization, Resonance Escape Probability, and Fast Fission Factor of Water Moderated Slightly Enriched Uranium Lattices, WAPD-134 (Sept. 1955). 

Either ratio, Ra or pa, can be related to the resonance escape probability or the conversion ratio. Microscopic (intracellular) flux distributions can be measured, and values of disadvantage factors and thermal utilisation can be obtained from them, b lattices of slightly enriched uranium rods in ordinary water it has also been possible to determine, indirectly, the migration area or age, and thus to obtain an experimental link between the macroscopic and microscopic properties of such lattices. 

Measurements of Reactor Parameters in Subcritical and Critical Assemblies-Lot-ticesof Slightly Enriched Uranium in Water,... 

The Determination of keofor Three Percent U-235 Enriched UO. and Slightly Enriched Uranium Metal from Monte Carlo Calculations, C. R, Richey (GE-HAPO. ... 

A Measurement the Post Oisodvonto e Foctor In.a LightrJyMer-Moderated, Slightly Enriched Uranium L ice, . Bliss,... 

Recent. Exponential and Critical-Approach Experiments. with Slightly Enriched Uranium Metal Tube s In Light Water / C. X. Sronn. R. C. Lloyd (BNW)... 

E]q>onential and critical-sq>proach experiments were performed on several slightly enriched uranium metal tubes md tube-in-tube combinations in light water. Exponential measurements were, performed on 1) 1.002 wt% U-235 ehriched uranium tubes 2) 1.002 wt% U-23S-enriched tubes containing an inner tube of 1.002 wt% U-235 3) 1.25 wt% U-235-enrlched tubes, and 4) 1.25 wt%U-235-enriched tubes containing an inner tube of 0.95 wt%U-235. Critical-m proach measurements were performed on 1.95 wt%enriched-uranium tubes. The dimensions of the tubes and the results of the ejqieriments are presented in Tables land n. 

Results of Exponential Measurements with Slightly Enriched Uranium Metal Tubes in Light Water... 

MALAVIYA, B. K., et al., Studies of Reactivity and Related. Parameters in Slightly Enriched Uranium, Heavy Water Lattices, MIT-2344-1 (May 25, 1964). 

Critical Experiments and Calculations in Some Very Under mode rated. Slightly Enriched, Uranium-Oxide/Woter Lottices/i4. R. 

HELLENS, R. L., and H. C. HONECK, A Summary and Preliminary Analysis of the BNL Slightly Enriched Uranium Water Moderator Lattice Measurements, Report of the Panel on Light Water Lattices Held in Vienna (1962), Technical Report Series No. 12, IAEA (1962). 

The critical parameters of slightly enriched uranium systenis are strongly dependent on both the enrichment and degree of moderation. Previous experiments performed in the Physical Constants Test Reactor (PCT of Battelle-Northwest have shown the minimum critical enrichment for homogeneous mixtures of UOs in water to be 1.034 0.010 wt%. Additional experiments with... 

R. L. HELLENS and G. A. PRICE, Reactor Physics Data for Water Moderated Lattices of Slightly Enriched Uranium, Reactor Technology, Selected Re-views-1964, iqp. 52S-609 (July 1964). 

Critical Masses for Slightly Enriched Uranium Rods in Uranyl Nitrate,i>. L. Dunaway (Natl Lead-OMo)... 

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