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Title: A study of reactivity biases and their dependence on spatial discretization in depleted TRIGA fuel

Abstract

The impact of spatial discretization on reactivity biases in TRIGA fuel models was analyzed here. In particular, unit-cell analyses in 2-D and 3-D were performed using Serpent to understand how spatial discretization affects the accuracy with which the effects of material evolution and temperature feedback are resolved. For temperature-dependent cases, a simple, single-channel model was employed. Analysis of 2-D models showed that essentially no radial discretization resolution is needed to eliminate biases (i.e., to reduce biases to the level of stochastic uncertainties) due to material evolution but that more than eight, equal-area, radial regions are needed to resolve temperature-feedback effects. Analysis of 3-D models showed that at least seven, equal-volume, axial regions may be required to resolve material evolution with temperature feedback leading to insignificant additional bias. Because of memory constraints, a full-core model with radially- and axially-resolved fuel elements may be impractical, especially for production-level analyses. Consequently, an “effective Doppler temperature” was determined empirically as a function of the radially-averaged temperature and may be used for future, full-core analyses.

Authors:
 [1];  [1]
  1. Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical and Nuclear Engineering
Publication Date:
Research Org.:
Kansas State Univ., Manhattan, KS (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE); Nuclear Regulatory Commission (NRC) (United States)
OSTI Identifier:
1494564
Alternate Identifier(s):
OSTI ID: 1416029
Grant/Contract Number:  
NE0008408; NRC-HQ-60-15-G-0004
Resource Type:
Accepted Manuscript
Journal Name:
Annals of Nuclear Energy (Oxford)
Additional Journal Information:
Journal Name: Annals of Nuclear Energy (Oxford); Journal Volume: 108; Journal ID: ISSN 0306-4549
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; reactivity bias; TRIGA; fuel depletion; temperature feedback; effective temperature

Citation Formats

Cheng, Ye, and Roberts, Jeremy A. A study of reactivity biases and their dependence on spatial discretization in depleted TRIGA fuel. United States: N. p., 2017. Web. doi:10.1016/j.anucene.2017.04.030.
Cheng, Ye, & Roberts, Jeremy A. A study of reactivity biases and their dependence on spatial discretization in depleted TRIGA fuel. United States. doi:10.1016/j.anucene.2017.04.030.
Cheng, Ye, and Roberts, Jeremy A. Thu . "A study of reactivity biases and their dependence on spatial discretization in depleted TRIGA fuel". United States. doi:10.1016/j.anucene.2017.04.030. https://www.osti.gov/servlets/purl/1494564.
@article{osti_1494564,
title = {A study of reactivity biases and their dependence on spatial discretization in depleted TRIGA fuel},
author = {Cheng, Ye and Roberts, Jeremy A.},
abstractNote = {The impact of spatial discretization on reactivity biases in TRIGA fuel models was analyzed here. In particular, unit-cell analyses in 2-D and 3-D were performed using Serpent to understand how spatial discretization affects the accuracy with which the effects of material evolution and temperature feedback are resolved. For temperature-dependent cases, a simple, single-channel model was employed. Analysis of 2-D models showed that essentially no radial discretization resolution is needed to eliminate biases (i.e., to reduce biases to the level of stochastic uncertainties) due to material evolution but that more than eight, equal-area, radial regions are needed to resolve temperature-feedback effects. Analysis of 3-D models showed that at least seven, equal-volume, axial regions may be required to resolve material evolution with temperature feedback leading to insignificant additional bias. Because of memory constraints, a full-core model with radially- and axially-resolved fuel elements may be impractical, especially for production-level analyses. Consequently, an “effective Doppler temperature” was determined empirically as a function of the radially-averaged temperature and may be used for future, full-core analyses.},
doi = {10.1016/j.anucene.2017.04.030},
journal = {Annals of Nuclear Energy (Oxford)},
number = ,
volume = 108,
place = {United States},
year = {2017},
month = {5}
}

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Cited by: 1 work
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Figures / Tables:

Figure 1 Figure 1: 2-D Radial Discretization of 2, 4, 8, 16 equal-volume regions

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