A Nuclear Reactor Transient Methodology Based on Discrete Ordinates Method

Shun Zhang,Hui Yu,Bin Zhang,Penghe Zhang,Yixue Chen

doi:10.1155/2014/491048

Abstract

With the rapid development of nuclear power industry, simulating and analyzing the reactor transient are of great significance for the nuclear safety. The traditional diffusion theory is not suitable for small volume or strong absorption problem. In this paper, we have studied the application of discrete ordinates method in the numerical solution of space-time kinetics equation. The fully implicit time integration was applied and the precursor equations were solved by analytical method. In order to improve efficiency of the transport theory, we also adopted some advanced acceleration methods. Numerical results of the TWIGL benchmark problem presented demonstrate the accuracy and efficiency of this methodology.

Highlights

In reactor transient, neutron’s movement can be described by the time-dependent Boltzmann transport equation or the simplified diffusion equation in many cases
TWIGL problem is a 2D transient benchmark based on diffusion theory, which was originally put forward by Hageman and Yasinsky in 1969 [12]
We have done some research on the numerical methods for transient based on discrete ordinates method

Summary

Introduction

Neutron’s movement can be described by the time-dependent Boltzmann transport equation or the simplified diffusion equation in many cases. Diffusion theory is widely used in reactor transient analysis because it needs less computing resources. Transport theory has greater and greater potential in solving the space-time reactor kinetics equation. The quasistatic method or the improved quasistatic method decomposes neutron flux into amplitude function and shape function The latter two methods are more efficient because they introduce several approximations, which in turn make them not as precise as the direct numerical processing. By using various acceleration techniques, the calculation time of direct numerical processing is completely acceptable. This is the reason why we choose the fully implicit method on the basis of transport theory. The fully implicit method for time variable has not been widely applied in mature transport code. The influence of acceleration methods and important parameters was presented

Solution Method

Measures for Accuracy

Acceleration Technique

Results and Analysis

Conclusion and Outlook