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A fission gas release model

Abstract

The hypothesis contained in the model developed in this work are as follows. The UO{sub 2} is considered as a collection of spherical grains. Nuclear reactions produce fission gases, mainly Xe and Kr, within the grains. Due to the very low solubility of these gases in UO{sub 2}, intragranular bubbles are formed, of a few nanometers is size. The bubbles are assumed to be immobile and to act as traps which capture gas atoms. Free atoms diffuse towards the grain boundaries, where they give origin to intergranular, lenticular bubbles, of the order of microns. The gas atoms in bubbles, either inter or intragranular, can re-enter the matrix through the mechanism of resolution induced by fission fragment impact. The amount of gas stored in intergranular bubbles grows up to a saturation value. Once saturation is reached, intergranular bubbles inter-connect and the gas in excess is released through different channels to the external surface of the fuel. The resolution of intergranular bubbles particularly affects the region of the grain adjacent to the grain boundary. During grain growth, the grain boundary traps the gas atoms, either free or in intragranular bubbles, contained in the swept volume. The grain boundary is considered as a  More>>
Authors:
Denis, A; Piotrkowski, R [1] 
  1. Argentine Atomic Energy Commission, Buenos Aires (Argentina)
Publication Date:
Aug 01, 1997
Product Type:
Conference
Report Number:
IAEA-TECDOC-957; CONF-9409411-
Reference Number:
SCA: 210000; PA: AIX-28:068400; EDB-98:020615; SN: 97001863037
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; FISSION PRODUCT RELEASE; GASES; MATHEMATICAL MODELS; BUBBLES; COMPUTERIZED SIMULATION; FISSION PRODUCTS; GRAIN BOUNDARIES; GRAIN GROWTH; URANIUM DIOXIDE; WATER COOLED REACTORS
OSTI ID:
568483
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: XA9744818068400
Availability:
INIS; OSTI as DE98602336
Submitting Site:
INIS
Size:
pp. 455-465
Announcement Date:

Citation Formats

Denis, A, and Piotrkowski, R. A fission gas release model. IAEA: N. p., 1997. Web.
Denis, A, & Piotrkowski, R. A fission gas release model. IAEA.
Denis, A, and Piotrkowski, R. 1997. "A fission gas release model." IAEA.
@misc{etde_568483,
title = {A fission gas release model}
author = {Denis, A, and Piotrkowski, R}
abstractNote = {The hypothesis contained in the model developed in this work are as follows. The UO{sub 2} is considered as a collection of spherical grains. Nuclear reactions produce fission gases, mainly Xe and Kr, within the grains. Due to the very low solubility of these gases in UO{sub 2}, intragranular bubbles are formed, of a few nanometers is size. The bubbles are assumed to be immobile and to act as traps which capture gas atoms. Free atoms diffuse towards the grain boundaries, where they give origin to intergranular, lenticular bubbles, of the order of microns. The gas atoms in bubbles, either inter or intragranular, can re-enter the matrix through the mechanism of resolution induced by fission fragment impact. The amount of gas stored in intergranular bubbles grows up to a saturation value. Once saturation is reached, intergranular bubbles inter-connect and the gas in excess is released through different channels to the external surface of the fuel. The resolution of intergranular bubbles particularly affects the region of the grain adjacent to the grain boundary. During grain growth, the grain boundary traps the gas atoms, either free or in intragranular bubbles, contained in the swept volume. The grain boundary is considered as a perfect sink, i.e. the gas concentration is zero at that surface of the grain. Due to the spherical symmetry of the problem, the concentration gradient is null at the centre of the grain. The diffusion equation was solved using the implicit finite difference method. The initial solution was analytically obtained by the Laplace transform. The calculations were performed at different constant temperatures and were compared with experimental results. They show the asymptotic growth of the grain radius as a function of burnup, the gas distribution within the grain at every instant, the growth of the gas content at the grain boundary up to the saturation value and the fraction of gas released by the fuel element referred to the total gas generated, as a function of burnup. 8 refs, 4 figs, 1 tab.}
place = {IAEA}
year = {1997}
month = {Aug}
}