# Rossi-alpha Benchmark Validation of a Static Alpha Eigenvalue Capability in OpenMC

Source: [Rossi-alpha Benchmark Validation of a Static Alpha Eigenvalue Capability in OpenMC](<https://www.sota2.com/research/paper/6a1e6392dbd7150506f85216>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2026-06-02T05:00:51.558Z

Authors: William Zywiec, Alessandro Ingegno, David Heinrichs, Benoit Forget

Published: 2026-05-30T22:06:01.000Z

## Abstract

A static alpha eigenvalue capability was implemented in a modified version of the open-source Monte Carlo radiation transport code OpenMC and validated against Rossi-alpha measurements from 21 delayed-critical benchmark experiments and 33 subcritical configurations spanning fast, intermediate, and thermal systems with U-233, HEU, IEU, LEU, and plutonium fuels. The effective delayed neutron fraction was calculated using the k-prompt method, and the prompt neutron lifetime was calculated using the iterated fission probability method, both evaluated within the standard k-eigenvalue power iteration. The delayed-critical alpha eigenvalue was calculated from these quantities using the point kinetics equation alpha\_dc = -beta\_eff / ell\_p. Agreement was generally within 10% for fast metal systems and within 5% for thermal solution systems. Subcritical extrapolation studies derived from the SHE-8 and STACY benchmark families show that alpha\_dc remains stable as the system is driven subcritical.

## Recorded benchmark results

A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage.

## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2606.00907>)

[PDF](<https://arxiv.org/pdf/2606.00907.pdf>)