Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

The influence of axial-burnup distribution on Keff for casks with spent fuel

9/01/2015 2015 - #02 Fuel cycle and nuclear waste management

Vnukov V.S. Kulikov V.I. Chkuaseli L.I.

DOI: https://doi.org/10.26583/npe.2015.2.11

UDC: 611.036.546.3

This article presents axial burnup data and evaluates the effects of axial-burnup on Keff for american cask GBC-32 storage and transportation spent fuel PWR and russian cask TUK-6 spent fuel VVER-440. The concept of taking credit for the reduction in reactivity due to fuel burnup is commonly referred to as «burnup credit». The reduction in reactivity that occurs with fuel burnup is due to the change concentration of fissile nuclides and the production of actinide and fissile-product neutron absorbers. This reduction reactivity is dependent upon the axial and horizontal variation of burnup. The horizontal variation of burnup has been investigated elsewhere and shown to have a relatively minor in part on neutron multiplication in a typical burnup credit. In contrast, the axial burnup profile has a significant impact on reactivity and therefore is an impotent of a burnup credit safety analisis. Great number axial profiles different assemblies PWR and VVER-440 was performed to evaluate. The difference in the neutron multiplication factor (Keff) between a calculation of axial-burnup distribution and a calculation that assumes uniform axial-burnup has become known as end effect (ΔK).

Cask GBC-32 have neutron absorbers. Cask TUK-6 have not neutron absorbers. The end effect increases with burnup and becomes positive at burnup higher 20 GWd/MTU.

ΔK becomes negative for burnup from 10 to 40 GWd/MTU for cask TUK-6 in water density from 0.1 to 0.9 g/cm3. This conclusion is possible used in nuclear safety analysis TUK-6 in normal and accident situation.

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burnup nuclear safety spent fuel cask storage transportation axial-burnup distribution