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BS ISO 15646:2014 pdf free

BS ISO 15646:2014 pdf free.Re-sintering test for UO2, (U,Gd)02 and (U,Pu)O2 pellets
Following the density measurement, the pellets, after position identification to ensure traceability, are subjected to heat treatment in the furnace using the following parameters.
Heating rate: <15 °C/min (at higher rates the pellets could burst). A heating rate of 5 °C/min is recommended in order to be sure not to burst the pellets.
Heat treatment temperature: shall be specified jointly by the customer/fuel designer and the fuel vendor. As example, temperatures of the order of 1700 °C are generally applied.
Treatment time: shall be specified jointly by the customer/fuel designer and the fuel vendor. As example, residence time of the order of 24 h is generally applied.Suitable treatment atmosphere (see Examples 1 to 3).
EXAMPLE1 For UO2 pellets, pure hydrogen (5.1) or mixtures of noble gas with at least 3 % hydrogen (5.1) can be used.
EXAMPLE2 For (U, Gd)O2 and (U, Pu)O2 pellets, a shift in stoichiometry of pellets occurs during treatment when using dry hydrogen or dry hydrogen/noble gas mixtures. This can be avoided by using a gas atmosphere with a suitable oxygen partial pressure which keeps the stoichiometry constant during re-sintering. Adjusting the oxygen partial pressure can be done by admixing CO2 in appropriate proportions to the re-sinter atmosphere or by using wet hydrogen or wet hydrogen/noble gas mixtures.
EXAMPLE 3 A pure argon atmosphere can be used.
NOTE For (U, Gd)O2 pellets, if necessary, an adjustment of the initial oxygen/heavy metal (U+Gd) ratio can be performed by heat treatment of the pellets at 150。C in air during a holding time of 5 h. The heat-up rate shall be low enough to avoid cracking especially at high Gd contents. The annealing step ensures the adjustment of the equilibrium stoichiometry for (U,Gd)02 fuel pellets with a Gd content up to 10 % by mass.Cool down rate: <15 °C/min.
Records: For each re-sintering run, the temperature profile is recorded. If the temperature profile satisfies the heat treatment condition specified above, the results of the re-sintering test are accepted.BS ISO 15646 pdf download.

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