Analysis of oscillations in the theta-weighted differencing scheme

Journal Article · Sat Dec 31 04:00:00 EST 1994 · Transactions of the American Nuclear Society

OSTI ID:89113

Petrovic, B G; Haghighat, A

The discrete ordinate (S{sub N}) method is widely used for solving the neutron transport equation. To enable numerical solution of discretized equations, it is necessary to postulate the flux shape within each phase-space cell, which leads to a corresponding differencing scheme. A choice of the differencing scheme may have significant impact on results. In recent studies of the reactor pressure vessel (PV) fluence calculations using the S{sub N} theory code DORT, nonphysical oscillations in the solution were observed and related to the DORT {theta}-weighted differencing scheme. An additional observed anomaly is that the solutions obtained using various differencing schemes do not necessarily converge to a unique solution when the spatial/angular mesh is refined. Similar findings have been previously reported; however, a complete explanation of this phenomenon is still needed. This paper reexamines the weighted differencing schemes available in the DORT code, and through a simple analytical benchmark problem, an attempt is made to understand the cause of the observed oscillations.

• OSTI ID: 89113
• Report Number(s): CONF-941102--
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 71; ISSN TANSAO; ISSN 0003-018X
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
66 PHYSICS
D CODES
DISCRETE ORDINATE METHOD
FINITE DIFFERENCE METHOD
NEUTRON TRANSPORT THEORY
OSCILLATIONS
REACTOR PHYSICS