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Influence of coated particle structure in thermal neutron spectrum energy range

Abstract

The heterogenity due to lumping the fuel in coated particles affects the thermal neutron spectrum. A calculation model is discussed which, apart from some simplifying assumptions about the statistical distribution, allows a rigorous computation of effective cross sections for all nuclides of the heterogeneous medium. It is based on an exact computation of the neutron penetration probability through coating and kernel. The model is incorporated in a THERMOS-code providing a double heterogeneous cell calculation, which can be repeated automatically at different time steps in the depletion code system MAFIA-V.S.O.P.. A discussion of the effects of the coated particle structure is given by a comparison of calculations for heterogeneous and homogeneous fuel zones in pebble bed reactor elements. This is performed for enriched UO{sub 2} fuel and for a ThO{sub 2}-PuO{sub 2} mixture in the grains. Depending on the energy dependent total sigmas in the kernels the changes of the cross sections are ranging from 0.1% up to 45%. The influence on the spectrum averaged sigmas of the nuclides in the fresh UO{sub 2} fuel is lower than 1%. For the emerging {sup 240}Pu it increases up to 3.3% during irradiation. For the ThO{sub 2}-PuO{sub 2} fuel the averaged sigmas of  More>>
Publication Date:
Feb 15, 1971
Product Type:
Technical Report
Report Number:
DCPM-11/KFA-2
Resource Relation:
Conference: 11. Dragon Countries Physics Meeting, London (United Kingdom), 11-12 Feb 1971; Other Information: Portions of the full text have limited legibility; Running headline: Coated Particle Structure; Accepted for publication in Nucl. Sci. and Eng.
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; DRAGON REACTOR; HTGR TYPE REACTORS; EXPERIMENTAL REACTORS
Sponsoring Organizations:
OECD Dragon Project, Paris (France)
OSTI ID:
21146880
Research Organizations:
Kernforschungsanlage Juelich G.m.b.H. (KFA) (Germany). Inst. fuer Reaktorentwicklung
Country of Origin:
NEA
Language:
English
Other Identifying Numbers:
TRN: XN71OS022
Availability:
Commercial reproduction prohibited; OSTI as DE21146880
Submitting Site:
OSTI
Size:
19 pages
Announcement Date:
Mar 31, 2009

Citation Formats

Hansen, U, and Teuchert, E. Influence of coated particle structure in thermal neutron spectrum energy range. NEA: N. p., 1971. Web.
Hansen, U, & Teuchert, E. Influence of coated particle structure in thermal neutron spectrum energy range. NEA.
Hansen, U, and Teuchert, E. 1971. "Influence of coated particle structure in thermal neutron spectrum energy range." NEA.
@misc{etde_21146880,
title = {Influence of coated particle structure in thermal neutron spectrum energy range}
author = {Hansen, U, and Teuchert, E}
abstractNote = {The heterogenity due to lumping the fuel in coated particles affects the thermal neutron spectrum. A calculation model is discussed which, apart from some simplifying assumptions about the statistical distribution, allows a rigorous computation of effective cross sections for all nuclides of the heterogeneous medium. It is based on an exact computation of the neutron penetration probability through coating and kernel. The model is incorporated in a THERMOS-code providing a double heterogeneous cell calculation, which can be repeated automatically at different time steps in the depletion code system MAFIA-V.S.O.P.. A discussion of the effects of the coated particle structure is given by a comparison of calculations for heterogeneous and homogeneous fuel zones in pebble bed reactor elements. This is performed for enriched UO{sub 2} fuel and for a ThO{sub 2}-PuO{sub 2} mixture in the grains. Depending on the energy dependent total sigmas in the kernels the changes of the cross sections are ranging from 0.1% up to 45%. The influence on the spectrum averaged sigmas of the nuclides in the fresh UO{sub 2} fuel is lower than 1%. For the emerging {sup 240}Pu it increases up to 3.3% during irradiation. For the ThO{sub 2}-PuO{sub 2} fuel the averaged sigmas of the isotopes vary from 0.5% to 5.7% depending on the state of irradiation. Correspondingly there is an influence on the plutonium isotopic composition, on breeding ratios, and on the tilt of k{sub eff} during burnup which will be discussed in detail.}
place = {NEA}
year = {1971}
month = {Feb}
}