Improvement of Geant4 Neutron-HP package: from methodology to evaluated nuclear data library

TL;DR

This paper identifies limitations in Geant4's neutron-HP package for thermal neutrons, proposes modifications, and develops a nuclear processing tool to enhance compatibility with evaluated nuclear data libraries, improving simulation accuracy.

Contribution

The paper introduces specific modifications to Geant4's neutron-HP package and a new nuclear processing tool to support additional data libraries, advancing neutronics simulation capabilities.

Findings

Improved agreement with reference code Tripoli for thermal neutron interactions.

Enhanced compatibility of Geant4 with ENDF-BVIII.0 and JEFF-3.3 libraries.

Validated modifications and tools for future Geant4 releases.

Abstract

An accurate description of interactions between thermal neutrons (below 4 eV) and materials is key to simulate the transport of neutrons in a wide range of applications such as criticality-safety, reactor physics, compact accelerator-driven neutron sources, radiological shielding or nuclear instrumentation, just to name a few. While the Monte Carlo transport code Geant4 was initially developed to simulate particle physics experiments, %-with a large emphasis given on modeled cross-sections for all known particles at all conceivable energies-, its use has spread to neutronics applications, requiring evaluated cross-sections for neutrons and gammas between $0$ and $20$ MeV (the so-called neutron High Precision -HP- package), as well as a proper offline or on-the-flight treatment of these cross-sections. In this paper we will point out limitations affecting Geant4 (version 10.07.p01) thermal neutron treatment and associated nuclear data libraries, by using comparisons with the reference Monte Carlo neutron transport code \tripoli, version 11, and we will present the results of various modifications of the Geant4 neutron-HP package, required to overcome these limitations. Also, in order to broaden the support of nuclear data libraries compatible with Geant4, a nuclear processing tool has been developed and validated allowing the use of the code together with ENDF-BVIII.0 and JEFF-3.3 libraries for example. These changes should be taken into account in an upcoming Geant4 release.