CONFLUX: A standardized framework to calculate reactor antineutrino flux

Nuclear fission reactors are abundant sources of antineutrinos for neutrino physics experiments. The flux and spectrum of antineutrinos emitted by a reactor can indicate its activity and composition, suggesting potential applications of neutrino measurements beyond fundamental scientific studies that may be valuable to society. The utility of reactor antineutrinos for applications and fundamental science is dependent on the availability of precise predictions of these emissions. For example, in the last decade, disagreements between reactor antineutrino measurements and models have inspired revision of reactor antineutrino calculations and standard nuclear databases as well as searches for new fundamental particles not predicted by the Standard Model of particle physics. Past predictions and descriptions of the methods used to generate them are documented to varying degrees in the literature, with different modeling teams incorporating a range of methods, input data, and assumptions. The resulting difficulty in accessing or reproducing past models and reconciling results from differing approaches complicates the future study and application of reactor antineutrinos. The CONFLUX (Calculation Of Neutrino FLUX) software framework is a neutrino prediction tool built with the goal of simplifying, standardizing, and democratizing the process of reactor antineutrino flux calculations. CONFLUX includes three primary methods for calculating the antineutrino emissions of nuclear reactors or individual beta decays that incorporate common nuclear data and beta decay theory. The software is prepackaged with the current nuclear databases, including ENDF.B/VIII, JEFF-3.3, and ENSDF, and it includes the capability to predict time-dependent reactor emissions, adjust nuclear database or beta decay inputs/assumptions, and propagate related sources of uncertainty. This paper describes the CONFLUX software structure, details the methods used for flux and spectrum calculations, and provides examples of potential use cases.

Program summary

Program Title: CONFLUX

CPC Library link to program files: https://doi.org/10.17632/hvkr4bff8v.1

Developer's repository link: https://github.com/CNFLUX/conflux

Licensing provisions: MIT

Programming language: Python, C++

Nature of problem: The reactor antineutrino flux were calculated with various nuclear theories of beta-decay and different nuclear databases. The prediction of neutrino produced from nuclear reactors was hard to repeat, or used for in reactor-specific models. Calculations of the covariance among fission products and beta decay branches need more standard approaches.

Solution method: We implement the CONFLUX software framework to standardize and simplify the calculation of reactor neutrino flux by modularize the nuclear databases, neutrino modeling methods, and the nuclear theories of beta-decay. So that the modeling of neutrinos from nuclear reactors can be done with minimum requirement of nuclear database, or the programming knowledge. The modules in the CONFLUX calculation are designed as customizeable and replaceable for updated and more accurate databases or beta-decay models.