Using dynamic frequencies for overcoming the stiffness of the neutronic space-time kinetic calculations

Conference · Fri Jan 01 04:00:00 EST 1993 · Transactions of the American Nuclear Society; (United States)

OSTI ID:6022971

Chao, Y A; Risher, D H ^[1]

---

1. Westinghouse Electric Corp., Pittsburgh, PA (United States)

One of the major computational difficulties in space-time kinetics is the [open quotes]stiffness[close quotes] of the kinetic equations, which is caused by the orders-of-magnitude difference between the prompt neutron and delayed neutron lifetimes. As a result, the time discretization step size in the numerical solution of the equations has to be very small to reflect the very fast response of the prompt neutrons. The idea of the [open quotes]stiffness confinement method[close quotes] was introduced and successfully demonstrated in Ref. I to alleviate the stiffness problem. The method uses a time-dependent [open quotes]dynamic frequency[close quotes] to replace the time-derivative term in the kinetic equations and calculates the dynamic frequencies iteratively in solving the equations. If the dynamic frequency for the prompt neutron is set to zero, the method reduces to the prompt jump approximation but also extends the validity of the prompt jump approximation into the prompt supercritical regime. Otherwise, if the dynamic frequency for the prompt neutron is retained, then no approximation is introduced, and the time discretization step size can be significantly enlarged.

• OSTI ID: 6022971
• Report Number(s): CONF-930601--
• Conference Information: Journal Name: Transactions of the American Nuclear Society; (United States) Journal Volume: 68
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220100* -- Nuclear Reactor Technology-- Theory & Calculation
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
CALCULATION METHODS
COMPUTERIZED SIMULATION
DIFFERENTIAL EQUATIONS
EQUATIONS
FINITE DIFFERENCE METHOD
ITERATIVE METHODS
NEUTRON DIFFUSION EQUATION
NUMERICAL SOLUTION
PHYSICS
REACTOR COMPONENTS
REACTOR CORES
REACTOR KINETICS EQUATIONS
REACTOR PHYSICS
REACTORS
SIMULATION
TIME DEPENDENCE
WATER COOLED REACTORS