Prompt neutron lifetime in a strongly heterogeneous lattice

Conference · Wed Jan 01 04:00:00 EST 1992 · Transactions of the American Nuclear Society; (United States)

OSTI ID:6983104

Trumble, E F; Baumann, N P; Graves, W E ^[1]

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1. Westinghouse Savannah River Co., Aiken, SC (United States)

The prompt neutron lifetime I[sub p] is an important input parameter in the solution of the point reactor kinetics equations. Over the years, several methods have been developed to calculate the prompt neutron lifetime, or approximations to it. Many of these approximations, such as the thermal inverse velocity method, rely on conventional widsom, which dictates that for thermal reactors, the prompt lifetime is dominated by thermal neutrons, and consequently, little error accures from the use of the thermal neutron lifetime as an approximation. This is not necessarily true in strongly heterogeneous lattices such as those used at the Savannah River Site (SRS). Explicit calculations of the prompt neutron lifetime have shown that calculation of the thermal neutron lifetime can result in the overprediction of the prompt lifetime by as much as 15% in a typical SRS lattice. Therefore, a new method for calculating the prompt neutron lifetime has been developed. The alpha search method (ASM) utilizes the results of an alpha (time eigenvalue) search performed by the GLASS lattice physics code to compute the full-spectrum lifetime. This method has been found not to succumb to the same overprediction as the methods using the thermal neutron lifetime. The inverse velocity method and the problems associated with its use in strongly heterogeneous lattices as well as the formation of the new ASM are presented. The eigenvalue method has been chosen as a further comparison method, and results of these three methods for several different media are shown and discussed.

• OSTI ID: 6983104
• Report Number(s): CONF-921102--
• Conference Information: Journal Name: Transactions of the American Nuclear Society; (United States) Journal Volume: 66
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220100* -- Nuclear Reactor Technology-- Theory & Calculation
BARYONS
CALCULATION METHODS
COMPUTER CODES
EIGENVALUES
ELEMENTARY PARTICLES
FERMIONS
FISSION NEUTRONS
G CODES
HADRONS
KINETICS
NEUTRON SPECTRA
NEUTRONS
NUCLEONS
PROMPT NEUTRONS
REACTOR KINETICS
REACTOR LATTICES
SPECTRA
THERMAL NEUTRONS