Rossi-alpha Benchmark Validation of a Static Alpha Eigenvalue Capability in OpenMC
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| Main Authors: | , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866916070809403392 |
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| author | Zywiec, William Ingegno, Alessandro Heinrichs, David Forget, Benoit |
| author_facet | Zywiec, William Ingegno, Alessandro Heinrichs, David Forget, Benoit |
| contents | 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2606_00907 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Rossi-alpha Benchmark Validation of a Static Alpha Eigenvalue Capability in OpenMC Zywiec, William Ingegno, Alessandro Heinrichs, David Forget, Benoit Computational Physics Nuclear Experiment Applied Physics Atomic Physics 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. |
| title | Rossi-alpha Benchmark Validation of a Static Alpha Eigenvalue Capability in OpenMC |
| topic | Computational Physics Nuclear Experiment Applied Physics Atomic Physics |
| url | https://arxiv.org/abs/2606.00907 |