NuDEX: A new nuclear γ-ray cascades generator

E Mendoza,A Algora,D Jordan,J.L Tain,D Cano-Ott,Z Ge,W Wang,Y Chen,H Zhang,N Shu

doi:10.1051/epjconf/202023917006

Abstract

Evaluated nuclear data libraries written in ENDF-6 format are used by Monte Carlo codes such as Geant4, MCNP6 or FLUKA for the transport of low energy neutrons (up to 20 MeV). The format in which the production of γ-rays after neutron induced reactions is provided do not allow, in general, to generate these γ-ray cascades in a correlated way. This prevents, among other things, energy conservation event by event, which is crucial in many applications. We have developed a code capable to generate correlated de-excitation γ-ray cascades using as much information as possible available in the RIPL-3 and ENSDF nuclear structure data libraries, among other useful information. The code follows the same philosophy of the DICEBOX or DEGEN codes. It generates the complete level scheme and branching ratios of the nucleus by using all the information experimentally known (known level scheme and known branching ratios) and completing the missing information with the most reliable statistical models. This code is able to generate automatically cascades for a large variety of nuclei (∼300) without requiring a specific input for each particular isotope. The code has been written in C++ language and can be integrated in the Geant4 simulation toolkit framework.

Highlights

The transport of low energy neutrons performed by Monte Carlo codes such as Geant4 [1], MCNP6 [2] or FLUKA [3] usually rely in the information available in evaluated nuclear data libraries, originally written in ENDF-6 format [4] (JEFF-3.3 [5], ENDF/BVIII.0 [6], JENDL-4.0 [7] ...)
The lack of correlations does not affect the accuracy of many Monte Carlo calculations, such as for example the spatial distribution of the energy released by neutron reactions inside a nuclear reactor, dose calculations, or the response of a γ-ray detector to neutron reactions produced far from the detec
There is the possibility of providing the level scheme and branching ratios in the ENDF-6 format, but in practice this only occurs in a few simple cases, such as in some (n,n’) or (n,p’) reactions, in which the residual nucleus is left in a well know and low energy excited state

Summary

Introduction

The transport of low energy neutrons (up to 20 MeV) performed by Monte Carlo codes such as Geant4 [1], MCNP6 [2] or FLUKA [3] usually rely in the information available in evaluated nuclear data libraries, originally written in ENDF-6 format [4] (JEFF-3.3 [5], ENDF/BVIII.0 [6], JENDL-4.0 [7] ...). The information present in these data libraries concerning the γ-ray emission after nuclear reactions is given in many cases in terms of a list of nk γ-ray yields yk(En), with k = 1, 2, ..., nk. Each of these yields represent the average number of γ-rays of the type k emitted after the corresponding reaction. The yields depend in general on the neutron energy En, and the γ-ray associated to each yk(En) can have either a fixed energy or an energy probability distribution From this information it is possible to deduce some quantities such as the total energy of the emitted γ-ray cascade, the average multiplicity, and the energy distribution of the emitted γ-rays. There is the possibility of providing the level scheme and branching ratios in the ENDF-6 format, but in practice this only occurs in a few simple cases, such as in some (n,n’) or (n,p’) reactions, in which the residual nucleus is left in a well know and low energy excited state

10-3 Total γ-ray energy

Description of the code

Validation and verification

Results

Conclusions