{"paper":{"title":"PyNMC: An Open-Source Framework for Neutron Multiplicity Counting Simulation Coupling OpenMC, FREYA, and ALPHANSO","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"Open-source PyNMC framework simulates neutron multiplicity counting by coupling OpenMC, FREYA and ALPHANSO and matches ESARDA benchmark results.","cross_cats":["physics.comp-ph"],"primary_cat":"physics.ins-det","authors_text":"Christopher Fichtlscherer","submitted_at":"2026-05-17T13:25:32Z","abstract_excerpt":"Neutron multiplicity counting (NMC) underpins plutonium assay in nuclear safeguards, arms control, and disarmament verification, but existing simulation tools are essentially limited to MCNPX-PoliMi [1] (export-controlled, MCNP license required) and ONMS [2] (open-source but built on Geant4 with no scripting API); other codes (RMC, MCNP-PTA) are institute-internal. We present PyNMC, an open-source, Python-native NMC simulation framework that couples OpenMC for transport with FREYA for event-by-event correlated prompt-neutron emission and ALPHANSO for native ($\\alpha$, n)-source estimates, toge"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The framework is validated against the ESARDA Neutron Multiplicity Benchmark on bare 252Cf, low-multiplication Pu metal (M=1.12), and 10 g PuO2 with alpha-n source; simulated rates agree with point-model predictions and published ESARDA participant-code scatter.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The couplings between OpenMC transport, FREYA event-by-event emission, ALPHANSO alpha-n estimates, and the custom collision-level time-tagged recording plus Python shift-register post-processor introduce no significant artifacts or biases relative to the physics of real detectors.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"PyNMC delivers a Python-native open-source NMC simulation framework coupling OpenMC, FREYA, and ALPHANSO, validated on ESARDA benchmarks for Cf-252 and Pu samples with agreement to point models and participant codes.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Open-source PyNMC framework simulates neutron multiplicity counting by coupling OpenMC, FREYA and ALPHANSO and matches ESARDA benchmark results.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"e39a47c040e6543c8a03523efc6ebfac91d6fb831595d3da1e2a9017cadeae36"},"source":{"id":"2605.17440","kind":"arxiv","version":1},"verdict":{"id":"704658d9-07bf-4d32-a841-93f8cb7bf7cd","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-19T22:30:07.802785Z","strongest_claim":"The framework is validated against the ESARDA Neutron Multiplicity Benchmark on bare 252Cf, low-multiplication Pu metal (M=1.12), and 10 g PuO2 with alpha-n source; simulated rates agree with point-model predictions and published ESARDA participant-code scatter.","one_line_summary":"PyNMC delivers a Python-native open-source NMC simulation framework coupling OpenMC, FREYA, and ALPHANSO, validated on ESARDA benchmarks for Cf-252 and Pu samples with agreement to point models and participant codes.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The couplings between OpenMC transport, FREYA event-by-event emission, ALPHANSO alpha-n estimates, and the custom collision-level time-tagged recording plus Python shift-register post-processor introduce no significant artifacts or biases relative to the physics of real detectors.","pith_extraction_headline":"Open-source PyNMC framework simulates neutron multiplicity counting by coupling OpenMC, FREYA and ALPHANSO and matches ESARDA benchmark results."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2605.17440/integrity.json","findings":[],"available":true,"detectors_run":[{"name":"doi_title_agreement","ran_at":"2026-05-19T23:01:19.602387Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_compliance","ran_at":"2026-05-19T22:41:52.896418Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"claim_evidence","ran_at":"2026-05-19T21:41:57.723016Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"ai_meta_artifact","ran_at":"2026-05-19T21:33:23.672743Z","status":"skipped","version":"1.0.0","findings_count":0}],"snapshot_sha256":"2c149cfea0c50d5d9b4060dac4b79ab3decdc7bbc14c9d6f3595d7cbe2982f30"},"references":{"count":26,"sample":[{"doi":"","year":2003,"title":"MCNP-PoliMi: a Monte-Carlo Code for Correlation Measurements,","work_id":"9398b65d-ed8f-4898-a17e-20d224598dcb","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2016,"title":"Simulation of Neutron Multiplicity Measurements using Geant4 — Open Source Software for Nuclear Arms Control,","work_id":"b4c33859-4bf2-473f-bf7d-a37fcd8a41b7","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":1998,"title":"Application Guide to Neutron Multiplicity Counting,","work_id":"7f9abaa4-21d8-4434-bc1a-82ecfd8b5e03","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2015,"title":"Nuclear Warhead Verification: A Review of Attribute and Template Systems,","work_id":"d40e7f5c-dbb1-4622-b30c-29e633d08b1a","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2015,"title":"Reducing Neutron Multiplicity Counting Bias for Plutonium Warhead Authentica - tion,","work_id":"1b197015-900d-4d26-8e10-1fadc0fc04f9","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":26,"snapshot_sha256":"038a027fb314ccb200d6c92f427a39082d2befc8c59ecb470bd949376f5e5369","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}