Fusion–fission hybrid — a source, a blanket, no chain
The coupling of a fusion neutron source to a subcritical fission blanket: source-to-blanket neutronics coupling declarations, blanket multiplication accounting with the effective multiplication strictly below unity as a declared boundary, energy-multiplication and fuel-conversion bookkeeping, and source-class declarations that reference the designated source device core without absorbing it. SCPN-FUSION-FISSION-HYBRID-CORE owns the device truth of the fusion_fission_hybrid configuration.
What the configuration is
A 14 MeV fusion neutron dropped into a blanket of uranium or thorium fissions and breeds far more energy and fuel than the fusion reaction that made it. A hybrid therefore needs a much less demanding fusion driver than a pure fusion plant — an engineering Q near one can suffice — at the price of being a fission machine with a fission machine's fuel cycle. The blanket stays subcritical: no chain reaction sustains itself. The hybrid core owns only the coupling and its bookkeeping; the source is whichever device core the configuration declares, and the four figures of merit it evaluates are exactly the ones the 1979 Oak Ridge assessment published.
What the core owns
- the device boundary: plant and experiment truth, lifecycle and configuration policy for the coupling of a fusion neutron source to a subcritical fission blanket;
- source-to-blanket neutronics coupling declarations, blanket multiplication accounting (effective multiplication strictly below unity as a declared boundary), energy-multiplication and fuel-conversion bookkeeping contracts, source-class declarations that reference the designated source core without absorbing it;
- the declared configuration: blanket \(k_{\mathrm{eff}}\) and fertile class; neutron source rate;
- diagnostic semantics for the coupled system (source-rate channels, blanket flux and multiplication monitors); the CONTROL adapter specification; the registry binding (version 1.0.0) and the domain manifest.
What it explicitly excludes
- Fusion source device physics: the designated source device core per configuration (tokamak, mirror, MIF or other family) — this core couples to a declared source and never owns its physics.
- Ordinary blanket and balance-of-plant utilities: out-of-scope plant engineering; only the coupling contracts live here.
- Solver mathematics and validation evidence: SCPN-Fusion-Core, until an exact surface passes the reactor family migration gate; no solver code exists in, or was copied into, the device core.
- Typed signal semantics and comparability: SCPN-Phase-Orchestrator (review-only output, never actuation). Control admission and action formation: SCPN-Control. Machine protection: independent systems retain the final veto. Portfolio presentation and gating: SCPN-Studio.
Level-0 physics and its anchor
The four published figures of merit of a hybrid — thermal power ratio (eq. 1), hybrid electrical efficiency (eq. 2), off-line and on-line capacity ratios (eqs. 6 and 7), the number of fission reactors supported (eq. 4) — and the agreement of eq. 7 with the form of eq. 5 over a sweep of driver and blanket values, asserted within a tolerance because 317 of 6372 parameter points disagree in the last places; every declared input refused outside its interval at the relation and at the declaration, a conversion ratio of one or more refused rather than reduced; the declared blanket energy multiplication and the neutron multiplication \(1/(1-k_{\mathrm{eff}})\) reported separately and derived from each other in neither direction. Anchored on Saltmarsh, Grimes & Santoro, ORNL/PPA-79/3 (1979), read off the rendered page because the scan's OCR mangles digits: the 1.33 of eq. 17 exactly; \(R_o = 68\) of eq. 19 (68.15) for the semicatalysed D–D driver with a molten-salt thorium blanket (\(E_{\mathrm{fus}}\) 12.45 MeV, \(f_n\) 0.66, \(F\) 0.7, \(M\) 1.5, \(\eta_H\) 0.35); \(Q' \approx 1.4\) for electrical self-sufficiency (1.396); thorium supporting 3–5× the uranium blankets of Table 1 (4.70 fresh, 4.03 exposed; uranium \(F\) 1.53/1.45, \(M\) 8.5/17.0 with plutonium reactors at \(C = 0.6\), \(\alpha = 0.3\); thorium \(F\) 0.62/0.52, \(M\) 2.13/4.59 with uranium-233 reactors at \(C = 0.85\), \(\alpha = 0.1\)); the ceiling identity \(Q'B/(1+Q'B)\); about 3 % fissile buildup roughly halving the reactor number (2.08 uranium, 2.42 thorium).
Load the ORNL blankets in the explorer →
Non-claims
- No parameter set describes any real machine, and nothing in the record is a criticality-safety, nuclear-safety, licensing, safeguards or proliferation-resistance statement.
- The energy multiplication of the figures of merit and the neutron multiplication of the blanket are different quantities; no filed source relates them, so nothing here does either.
- Source-class, blanket-concept and fuel-cycle choices are configuration facets, not separate claims; no capability has reached any state beyond
computational_prototype.
Capabilities and evidence
Evidence maturity computational_prototype, five implemented capabilities, each with its evidence record in VALIDATION.md: the device configuration model, the diagnostic and clock semantics model, level-0 device physics (the closed forms on this page), the device 3D model and the device CAD model. No parameter set or channel describes any real machine or diagnostic.