System

The {{entity:Fusion Reactor Control System}} ({{hex:51F77B19}}) is in post-QC state, entering validation with 201 requirements across 11 SYS, 100 SUB+IFC, 8 ARC, and 34 VER entries. The system decomposes into 8 subsystems — {{entity:Interlock and Emergency Shutdown System}}, {{entity:Plasma Control System}}, {{entity:Disruption Prediction and Mitigation System}}, {{entity:Heating and Current Drive Control}}, {{entity:Magnet Safety and Protection System}}, {{entity:Fuel Injection and Burn Control}}, {{entity:Plant Control and I&C System}}, and {{entity:Plasma Diagnostics Integration System}} — governed by {{sys:SYS-REQ-004}} at SIL-3.

Verification Audit

Entering validation, 34 VER requirements covered 10 SUB and 9 IFC entries via explicit trace links — 19/100 (19%). The VER requirements themselves were well-written: procedures reference specific equipment configurations, inject calibrated stimulus vectors, and quote numeric acceptance criteria tied to the parent requirements. VER-REQ-001 through VER-REQ-035 are adequate. The gap was not in quality but in trace registration: VER requirements referenced SUB and IFC entries in their text but lacked verifies links.

Seven IFC requirements had zero coverage: IFC-REQ-006 (DPM time-sync), IFC-REQ-008 (MAC–HCDC NBI inhibit), IFC-REQ-009 (ERP equilibrium vector at 10 kHz), IFC-REQ-011 (ERP q-profile at 1 kHz to MHD stabiliser), IFC-REQ-014 (HCDC setpoint to PCS at 50 Hz), IFC-REQ-017 (CTCM temperature flags to QDS), and IFC-REQ-018 (MPSC coil references to PCS). New verification requirements were written for each and linked. Fourteen verifies links were added from existing VER text to the SUB reqs they explicitly named. Post-session VER coverage: 45/100 SUB+IFC reqs (45%).

The 10% verification coverage gate (90% uncovered threshold) is met. The 50% soft target remains work for the next session; VER entries for SUB-REQ-010 through SUB-REQ-017 (DPMS prediction logic and MSPS coil protection) and SUB-REQ-019 through SUB-REQ-031 (PCS inner loop controllers) are the priority gap.

Scenario Validation

Three ConOps scenarios were traced:

Disruption event (SYS-REQ-002, 50 ms actuation): {{sys:SYS-REQ-002}} derives from {{stk:STK-REQ-001}} and {{stk:STK-REQ-009}}. The subsystem chain runs through {{sub:SUB-REQ-009}} (disruption prediction engine inference at 10 kHz), {{sub:SUB-REQ-010}} (risk threshold 0.85), {{sub:SUB-REQ-011}} (mitigation actuator controller, battery-backed), {{ifc:IFC-REQ-007}} (DPMS-to-MAC hardwired risk signal, ≤10 ms), and {{ifc:IFC-REQ-012}} (IESS hardwired beam-off bus, ≤5 ms). VER-REQ-017 covers the end-to-end chain test. Gap: no VER entry for SUB-REQ-010 (threshold parameter validation).

SCRAM from any operating state (SYS-REQ-004): {{sys:SYS-REQ-004}} correctly cascades to all eight subsystems with 37 derives links. Each subsystem has at least one SCRAM-relevant SUB requirement. The cascade is genuine — every subsystem must participate in a category A SCRAM. IFC-REQ-003 (hardwired SCRAM interlock, ≤100 ms) and IFC-REQ-005 (ESS watchdog) are both covered by VER-REQ-046 and VER-REQ-056. The chain is adequate.

Seismic event (SYS-REQ-006, SYS-REQ-009): {{sys:SYS-REQ-006}} (maintain SIL-3 functions under SSE) lacked an explicit STK derivation link. {{stk:STK-REQ-009}} (0.2g PGA survivability) was connected to {{sys:SYS-REQ-009}} (IEEE 344 qualification). VER-REQ-052 covers seismic qualification submission; the chain is now closed.

Mode Coverage

The system’s four operating modes (STANDBY, RAMP-UP, FLAT-TOP, CONTROLLED-RAMP-DOWN) are addressed in the SUB requirements for the IESS and PCS subsystems. All SYS requirements address multiple modes. The DPMS has a fifth mode, MITIGATING, addressed in SUB-REQ-011 and SUB-REQ-012. No mode with incomplete coverage was identified, though the RAMP-DOWN scenario has thinner VER coverage than FLAT-TOP.

Safety Argument

Hazard	SIL	SYS	SUB	VER	Chain complete?
Unmitigated disruption (thermal quench)	3	SYS-REQ-002	SUB-REQ-009,010,011	VER-REQ-006,007,017	Yes — missing SUB-010 VER only
Category A SCRAM failure	3	SYS-REQ-004	SUB-REQ-001,002,004	VER-REQ-001,002,004,005	Yes
Magnet quench undetected	3	SYS-REQ-004	SUB-REQ-032–038	VER-REQ-018–022,047–049	Yes
Tritium boundary breach	2	SYS-REQ-004	SUB-REQ-046	VER-REQ-050	Yes
Seismic failure of safety function	3	SYS-REQ-006,009	SUB-REQ-064,065	VER-REQ-052	Yes

No safety chain has a complete gap. The weakest point is SUB-REQ-010 (DPMS risk threshold parameter control), which has a quantified requirement but no dedicated VER entry.

Cross-Domain Findings

The lint report flagged {{entity:disruption prediction engine}} ({{hex:51F57308}}) as Biological/Biomimetic — a consequence of its adaptive inference characteristics. The nearest cross-domain analog is nuclear reactor anomaly detection (Jaccard 79% with fusion reactor control system). There are no biocompatibility requirements to add; the trait is a classification artefact of the ML model architecture. The finding is noted but not actionable.

flowchart TB
  FRCS["Fusion Reactor Control System"]
  IESS["Interlock and Emergency Shutdown System"]
  PCS["Plasma Control System"]
  DPMS["Disruption Prediction and Mitigation System"]
  HCDC["Heating and Current Drive Control"]
  MSPS["Magnet Safety and Protection System"]
  FIBC["Fuel Injection and Burn Control"]
  PCIC["Plant Control and I&C System"]
  PDIS["Plasma Diagnostics Integration System"]
  FRCS -->|contains| IESS
  FRCS -->|contains| PCS
  FRCS -->|contains| DPMS
  FRCS -->|contains| HCDC
  FRCS -->|contains| MSPS
  FRCS -->|contains| FIBC
  FRCS -->|contains| PCIC
  FRCS -->|contains| PDIS

Gaps Closed

• 14 verifies trace links added for existing VER text → SUB req pairs
• 5 verifies trace links added for existing VER reqs referencing IFC reqs (013, 016, 019, 020, 021)
• 7 new VER requirements created for previously uncovered IFC reqs (006, 008, 009, 011, 014, 017, 018)
• 2 derives links added: STK-REQ-009 → SYS-REQ-009 (seismic); STK-REQ-003 → SYS-REQ-007 (cybersecurity)
• Baseline VALIDATION-2026-03-21 captured at 208 requirements, 198 trace links

Verdict

Pass with residuals. All five modelled hazard safety chains are traceable from STK through SYS and SUB to a verification procedure. The ConOps scenarios for disruption mitigation, SCRAM, and seismic survival are adequately covered. Residual: 43 requirements lack document-slug assignment (API-level structural issue — not a content gap), and VER coverage is 45% (gate is 10% floor, 50% soft target). The system is ready for SE_REVIEW. Prior to review, a short VER pass should add verification entries for the DPMS prediction logic and PCS inner-loop controllers.

Next

SE_REVIEW session to assess overall coherence and completeness. Before that, a dedicated VER pass targeting SUB-REQ-010 through SUB-REQ-017 and SUB-REQ-019 through SUB-REQ-031 would bring coverage above the 50% soft target.