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First steps towards modelling high burnup effect in UO{sub 2} fuel

Abstract

High burnup initiates a process that can lead to major microstructural changes near the edge of the fuel: formation of subgrains, the loss of matrix fission gas and an increase in porosity. A consequence of this, is a decrease of thermal conductivity near the edge of the fuel which may be major implications for the performance of LWR fuels at higher burnup. The mechanism for the changes in grain structure, the apparent depletion of Xe and increase in porosity is associated with the high fission density at the fuel periphery. This is in turn due to the preferential capture of epithermal neutrons in the resonances of {sup 238}U. The new model TUBRNP predicts the radial burnup profile as a function of time together with the radial profile of plutonium. The model has been validated with data from LWR UO{sub 2} fuels with enrichments in the range 2 to 8.25% and burnups between 21 to 75 Gwd/t. It has been reported that at high burnup EPMA measures a sharp decrease in the concentration of Xe near the fuel surface. This loss of Xe is interpreted as a signal that the gas has been swept out of the original grains into pores:  More>>
Authors:
O`Carroll, C; Lassmann, K; Laar, J Van De; Walker, C T [1] 
  1. CEC Joint Research Centre, Karlsruhe (Germany)
Publication Date:
Aug 01, 1997
Product Type:
Conference
Report Number:
IAEA-TECDOC-957; CONF-9409411-
Reference Number:
SCA: 210200; 210100; PA: AIX-28:068462; EDB-97:129968; SN: 97001863068
Resource Relation:
Conference: IAEA technical committee meeting on water reactor fuel element modelling at high burnup and its experimental support, Windermere (United Kingdom), 19-23 Sep 1994; Other Information: PBD: Aug 1997; Related Information: Is Part Of Water reactor fuel element modelling at high burnup and its experimental support. Proceedings of a technical committee meeting; PB: 559 p.
Subject:
21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS; BURNUP; SIMULATION; BWR TYPE REACTORS; NUCLEAR FUELS; POROSITY; PWR TYPE REACTORS; T CODES; THERMAL CONDUCTIVITY; URANIUM DIOXIDE; VARIATIONS; XENON
OSTI ID:
534358
Research Organizations:
International Atomic Energy Agency, Vienna (Austria)
Country of Origin:
IAEA
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 1011-4289; Other: ON: DE98602336; TRN: XA9744803068462
Availability:
INIS; OSTI as DE98602336
Submitting Site:
INIS
Size:
pp. 241-250
Announcement Date:
Oct 31, 1997

Citation Formats

O`Carroll, C, Lassmann, K, Laar, J Van De, and Walker, C T. First steps towards modelling high burnup effect in UO{sub 2} fuel. IAEA: N. p., 1997. Web.
O`Carroll, C, Lassmann, K, Laar, J Van De, & Walker, C T. First steps towards modelling high burnup effect in UO{sub 2} fuel. IAEA.
O`Carroll, C, Lassmann, K, Laar, J Van De, and Walker, C T. 1997. "First steps towards modelling high burnup effect in UO{sub 2} fuel." IAEA.
@misc{etde_534358,
title = {First steps towards modelling high burnup effect in UO{sub 2} fuel}
author = {O`Carroll, C, Lassmann, K, Laar, J Van De, and Walker, C T}
abstractNote = {High burnup initiates a process that can lead to major microstructural changes near the edge of the fuel: formation of subgrains, the loss of matrix fission gas and an increase in porosity. A consequence of this, is a decrease of thermal conductivity near the edge of the fuel which may be major implications for the performance of LWR fuels at higher burnup. The mechanism for the changes in grain structure, the apparent depletion of Xe and increase in porosity is associated with the high fission density at the fuel periphery. This is in turn due to the preferential capture of epithermal neutrons in the resonances of {sup 238}U. The new model TUBRNP predicts the radial burnup profile as a function of time together with the radial profile of plutonium. The model has been validated with data from LWR UO{sub 2} fuels with enrichments in the range 2 to 8.25% and burnups between 21 to 75 Gwd/t. It has been reported that at high burnup EPMA measures a sharp decrease in the concentration of Xe near the fuel surface. This loss of Xe is interpreted as a signal that the gas has been swept out of the original grains into pores: this ``missing`` Xe has been measured by XRF. It has been noted experimentally that the restructuring (Xe depletion and changes in grain structure) have an onset threshold local burnup in the region of 70 to 80 GWd/t: a specific value was taken for use in the model. For a given fuel TUBRNP predicts the local burnup profile, and the depth corresponding to the threshold value is taken to be the thickness of the Xe depleted region. The theoretical predictions have been compared with experimental data. The results are presented and should be seen as a first step in the development of a more detailed model of this phenomenon. (author). 22 refs, 9 figs, 2 tabs.}
place = {IAEA}
year = {1997}
month = {Aug}
}