Add (n,n') inelastic isomeric activation to depletion chains - #123
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Add (n,n') inelastic isomeric activation to depletion chains#123jon-proximafusion wants to merge 1 commit into
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Registers (n,n') as a chain transmutation reaction (MT=4) with entries in REACTIONS, DADZ, REACTION_MT, and the C++ REACTION_TYPE_MAP so that existing depletion operators can tally it by name. Chain.from_endf emits (n,n') entries only when isomeric production data exists for the parent, always including the ground-state self-loop so the Bateman loss and gain terms stay exact; parents without data get no self-loop at all. Covers cases like Nb93(n,n')Nb93_m1 and In115(n,n')In115_m1 that are pure isomeric-state changes with no nuclide change. Tests cover the registry entries, atom conservation of self-loop matrices, and an integration test on the real ENDF/B-VIII.1 Nb93 evaluation. See #121.
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Second part of #121, building on #122. Adds
(n,n')(MT=4) as a depletion chain reaction so that inelastic scattering that only changes the isomeric state of the target is representable, e.g. Nb93(n,n')Nb93_m1, In115(n,n')In115_m1, Pb204(n,n')Pb204_m1, which the FNS decay-heat benchmarking showed to be significant activation pathways.Changes
REACTIONS["(n,n')"] = ReactionInfo({4}, ())inopenmc/deplete/chain.py,DADZentry (0, 0),REACTION_MT["(n,n')"] = 4, and the C++REACTION_TYPE_MAPalias so existing depletion operators can tally the reaction by name.Chain.from_endfemits(n,n')entries only when isomeric production data exists for the parent, and always includes the ground-state self-loop so the Bateman loss and gain terms stay exact (loss at the full MT=4 rate, gain ofrate * brper target). Parents without data get no self-loop at all, so chains built without isomeric branching are unchanged.Compatibility note
Chains containing
(n,n')require an OpenMC version with these map entries; older versions raiseKeyErrorwhen setting up depletion tallies. That is why the reaction is only emitted underisomeric_branching=Trueand why this is a separate PR.Verification
Unit tests cover the registry entries and atom conservation of self-loop matrices; an integration test on the real ENDF/B-VIII.1 Nb93 evaluation checks the emitted self-loop pair (ground 1.0, m1 0.0) and the verbatim 34-point MF=10 table, and that Am241 (no MT=4 isomeric data) gets no
(n,n')entries.