Abstract
Under certain conditions, boiling water reactors (BWRs) are susceptible to coupled neutronic/thermal-hydraulic instabilities. Such instabilities, which are characterized by periodic core power and hydraulic oscillations, can compromise established fuel safety limits. There are two types of reactivity instabilities have been observed in commercial BWRs: A. Core-wide reactivity instabilities; B. Out of phase instabilities. In both cases, the reactivity instability is caused by the density wave mechanism, which is reinforced by feedbacks from neutronic power and channel inlet flow.LAPUR is a computer code developed at Oak Ridge National Laboratory for the calculation of BWR core stability parameters. It uses a multinodal description of the neutron dynamics, together with a distributed parameter model of the core thermal hydrodynamics to produce a space-dependent representation of the dynamics of a BWR in the frequency domain for small perturbations around a steady state condition. The LAPUR program consists of two autonomous modules, LAPURX and LAPURW, which are linked by means of an intermediate storage routine. The first module, LAPURX, solves the governing equations for the coolant and the fuel steady state. Map of the core steady state are generated and stored in data files for subsequent utilization by LAPURW. The second module, LAPURW, solves the dynamic equations for the coolant, fuel, and neutron field in the frequency domain. A set of open-loop transfer functions are generated and the stability index (decay ratio), is estimated from the closed loop reactivity to power transfer function.Today, personal computers are cheaper and powerful. With its faster and faster computing ability, we can dispatch PC to calculate the routine work, like the repeating parameter testes. In this paper, we use programming skills and loop concepts on LAPUR DR calculation, in order to saving human power on parameter testing. We expect that this method can provide a simple way to those who concentrate on parametric studies, and get a large mount, more and more reliable data easily.