A simplified few-group model for calculation of neutron flux spectra. [SIFAS Code]

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1980

OSTI ID:5337881

Sinclair, A N

A fast, efficient perturbation model is developed for generating few-group cross sections and flux spectrum and performing fuel depletion in a light water reactor unit cell configuration. In the thermal energy region, an approximate solution of the thermal neutron spectrum is determined based on the Wigner-Wilkins free-gas hydrogen scattering model. In the epithermal region, a combination of analytical and empirical techniques is used to determine resonance cross sections; group flux ratios and neutron leakage are determined by a three-group formulation of the B/sub 1/ equations. These models are combined in a perturbation scheme and incorporated as the SIFAS code. Unit cell depletion studies can be performed at a cost of less than 0.1 seconds per depletion step of The University of Michigan Amdahl 470V/7 computer, using a cross section library containing less than 500 words of information. Perturbations in lattice configuration, hydrogen/fuel atom ratio, and moderator temperature during fuel burnup can all be considered in the SIFAS code. Estimates of core reactivity obtained by the SIFAS code are generally within 0.2% of those determined by codes requiring large fine-group cross section libraries and computational time greater by at least an order of magnitude. Reaction rates of important nuclides in reactor cores can be estimated by the SIFAS code to better than 0.5% for fuel depletion studies for fuel burnup of up to 30,000 MWD/MTM.

• Research Organization: Michigan Univ., Ann Arbor (USA)
• OSTI ID: 5337881
• Country of Publication: United States
• Language: English

Related Subjects

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Light-Water Moderated
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BURNUP
COMPUTER CODES
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