C5G7-TD (Deterministic Time-Dependent Neutron Transport Benchmark without Spatial Homogenization)

Increasing efforts have been made to the development of codes for transient calculations of nuclear reactors in recent years. In order to ensure reliable modelling of neutron physics within a state-of-the-art transient code, the neutron kinetics part of such a code should be based on the full-scale calculation of the space-time neutron kinetics equations without use of the diffusion approximation and spatial homogenization. Such advanced approaches require the verification of neutron kinetics program modules through the cross-verification of codes, which are used to calculate thoroughly defined test cases, or the benchmarks.

However, existing benchmark problems are not able to satisfy the demand for verifying codes/methods for performing the homogenization-free time-dependent transport calculations. On one hand, some of them are simplified diffusion benchmarks, in which the computational domain is composed of several homogeneous regions. On the other hand, some of them have a broad range of sources of uncertainties involved in the calculation, such as the nuclear data, group cross section preparation procedure, and potentially other computational simplifications, making it difficult to reveal methodical errors of space-time neutron kinetics codes.

The current benchmark model is based on the well-studied steady-state C5G7 benchmark problems, which were developed to test the capabilities of radiation transport codes that do not utilize spatial homogenization above the fuel pin level. It is a miniature light water reactor (LWR) with sixteen fuel assemblies (mini-core): eight uranium oxide (UO2) assemblies and eight mixed oxide (MOX) assemblies, surrounded by a water reflector. It features a quarter-core radial symmetry in the 2-dimensional (2-D) configuration.

There are two sets of exercises considered in this problem. The first set, including three exercises, is focused on the 2-D configuration of the C5G7 core. The second set, including two exercises, is with regard to the 3-D C5G7 configuration.

The C5G7-TD benchmark is carried out in 3 phases as follows:
a) Phase I: Kinetics Phase – verification of methods/codes for
    heterogeneous time-dependent neutron transport calculations
    without feedback;
b) Phase II: Dynamics Phase – verification of methods/codes for
    heterogeneous time-dependent neutron transport calculations
    with feedback;
c) Phase III: High-fidelity Phase – uncertainty propagation in
    high-fidelity multi-physics calculations.

The benchmark team consists of KI, NCSU and GRS.

The workshop at ANS BEPU Conference will be the 3rd workshop of C5G7-TD.