Use of covariance matrices in criticality safety predictability studies

Journal Article · Mon Dec 01 04:00:00 EST 1997 · Transactions of the American Nuclear Society

OSTI ID:552493

Leal, L C; Derrien, H; Larson, N M ^[1]

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1. Oak Ridge National Lab., TN (United States)

In recent years important work has been performed in the analysis of neutron transmission and cross-section data for fissile nuclei in the resonance region by using the computer code SAMMY. SAMMY uses Bayes` method in a sequential analysis of several sets of experimental data aimed at obtaining the resonance parameters and their covariance. In this work, the Reich-Moore approximation of the R-matrix formalism is used to generate theoretical cross sections. In general, there are several thousand parameters, and the dimension of the covariance matrices is correspondingly large. These matrices are not reported in the current evaluated nuclear data files (ENDF, JEF, JENDL) because of their dimension and the inadequacy of the file formats. The aim of this work is to present a technique in which covariance data can be used in the generation of multi-group cross sections. This is illustrated by calculating {sup 235}U group-averaged cross sections from the covariance files generated by SAMMY since these can be more readily utilized in criticality predictability calculations. The calculations are performed in the energy range from thermal to 50 eV.

• OSTI ID: 552493
• Report Number(s): CONF-971125--
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 77; ISSN 0003-018X; ISSN TANSAO
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
66 PHYSICS
99 GENERAL AND MISCELLANEOUS
CRITICALITY
CROSS SECTIONS
MATRICES
NEUTRON TRANSPORT
NUMERICAL DATA
S CODES