Achievable bum-up

TABLE 7.1. NUMBER OF IFR METALLIC FUEL ELEMENTS IRRADIATED AS A FUNCTION OF BURN-UP 

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

In Russia over the period 1960 - 1980 numerous investigations have been carried out at RLAR (Dimitrovgrad) and IPPE (Obninsk) concerning the physical and technological aspects of metallic fuel [7.14]. Unalloyed metallic fuel has been proposed, developed and investigated 

The investigations performed made it possible to recommend unalloyed metallic fuel to be used in absorbers and the hiel elements of radial blankets, and axial blankets (smeared density - 80%) and core fuel elements (smeared density - 70%) with gas bonded pins. As a certain protection against interaction between fiiel and cladding a special oxide film is recommended to be applied to the fuel column. For core U-Pu fuel pins an additional protective coating on the cladding is recommended. Metallic uranium alloyed with zirconium and niobium was irradiated in BN-350 and BOR-60 as fuel material for absorbers and axial blankets. At present one subassembly with U-Pu-10%Zr is under irradiation in BOR-60, and one subassembly with U-10%Zr has been discharged from BOR-60 core with a maximum bum-up of about 10%. 

In conclusion, all the irradiation results have demonstrated the reliable performance of metallic fuel and its potential to achieve high bum-up in prototypical elements. The key characteristics of behaviour have been shown clearly and no limitations to IFR applications have been identified. 

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