System

The {{entity:Fusion Reactor Control System}} ({{hex:51F77B19}}) QC review, session 421. Project se-fusion-reactor-control-system entered QC at 283 requirements across 6 documents with 10 block diagrams, status transitioning from validated to qc-reviewed. Previous session (420) completed SE_VALIDATION. This session focused on trace integrity and coverage gap closure.

Findings

Orphan VER requirements — 12 unlinked. VER-REQ-108 through VER-REQ-119 were created during validation but never received trace links back to the requirements they verify. Each text begins “Verify SUB-REQ-xxx” or “Verify SYS-REQ-xxx”, making the mapping unambiguous. Affected targets included {{sub:SUB-REQ-013}}, {{sub:SUB-REQ-014}}, {{sub:SUB-REQ-020}}, {{sub:SUB-REQ-042}}, {{sub:SUB-REQ-044}}, {{sub:SUB-REQ-045}}, {{sub:SUB-REQ-047}}, {{sub:SUB-REQ-052}}, {{sub:SUB-REQ-053}}, {{sys:SYS-REQ-001}}, {{sys:SYS-REQ-002}}, and SYS-REQ-015.

Spurious links on SYS-REQ-004. The SIL-3 SCRAM requirement ({{sys:SYS-REQ-004}}) carried 34 outbound trace links. Inspection found two anomalies: a duplicate derives link to {{sub:SUB-REQ-108}} (the safe state definition — linked once at session 386, again at session 421 with a near-identical rationale), and a backwards verifies link from {{sys:SYS-REQ-004}} pointing to VER-REQ-084 as the source rather than target. The remaining 32 links were all reviewed and found to be genuine — each carries a specific engineering rationale explaining why that subsystem or interface requirement exists because of the SCRAM function. For a SIL-3 safety requirement spanning eight subsystems this link count is defensible, not spray.

Coverage gaps — 3 SYS concepts without SUB-level requirements. Lint identified “qualified maintenance bus within 10 seconds” from {{sys:SYS-REQ-011}} and the IEC 61513/61511 compliance obligations from {{sys:SYS-REQ-014}} as lacking subsystem implementations. The {{entity:gas puffing valve controller}} ({{hex:55F57A18}}) was classified {{trait:System-Essential}} but had no redundancy or failover requirement, a gap inconsistent with the SIL-3 system context.

Lint also flagged “disruption prediction engine” ({{hex:51F57308}}) as carrying the {{trait:Biological/Biomimetic}} trait (bit 3). This trait is almost certainly a misclassification — the DPE is an LSTM-based signal processing engine with no biological characteristics. The trait is a UHT artefact from classifying “prediction engine” in isolation from the nuclear context. No requirements action is warranted; reclassification is the correct fix but deferred to a dedicated Substrate session.

Verification coverage: 0 orphan requirements after fixes (was 12/280). All 28 IFC requirements have VER traces. No requirements were missing --rationale or --verification.

flowchart TB
  n0["Fusion Reactor Control System"]
  n1["Plasma Control System"]
  n2["Disruption Prediction and Mitigation System"]
  n3["Heating and Current Drive Control"]
  n4["Magnet Safety and Protection System"]
  n5["Fuel Injection and Burn Control"]
  n6["Plasma Diagnostics Integration System"]
  n7["Plant Control and I&C System"]
  n8["Interlock and Emergency Shutdown System"]
  n0 --> n1
  n0 --> n2
  n0 --> n3
  n0 --> n4
  n0 --> n5
  n0 --> n6
  n0 --> n7
  n0 --> n8

Corrections

Deleted duplicate SYS-REQ-004 → SUB-REQ-108 link (ID link-1774091440979; older link preserved). Deleted backward SYS-REQ-004 verifies VER-REQ-084 link (ID link-1774089738221; correct link from VER-REQ-084 to SYS-REQ-004 already exists).

Added 12 verifies trace links from VER-REQ-108 through VER-REQ-119 to their respective target requirements. Each rationale explains what specific acceptance criterion the test procedure addresses.

Created three new SUB requirements: (1) REQ-131 — {{entity:Plant Control and I&C System}} qualified maintenance bus compliant with IEC 61784-3, 10-second fault reporting, derives from {{sys:SYS-REQ-011}}; (2) REQ-132 — {{entity:Interlock and Emergency Shutdown System}} IEC 61513 Category A and IEC 61511 SIL-3 compliance obligation, derives from {{sys:SYS-REQ-014}}; (3) REQ-133 — {{entity:Gas Puffing Valve Controller}} dual-channel solenoid drive with independent power supplies and 100 ms channel-loss recovery, derives from {{sys:SYS-REQ-004}}.

Residual

The Biological/Biomimetic misclassification on the {{entity:disruption prediction engine}} should be corrected via uht-substrate entities reclassify with a context string that anchors the entity to its nuclear I&C setting. Not a requirements defect.

ARC requirements (ARC-REQ-001 through ARC-REQ-009) have no VER entries — the verify matrix shows “(no activities)” for all architecture decisions. Architecture decisions are informational rather than testable; verification entries for them would be synthetic. Acceptable residual.

Baseline BL-SEFUSIONREACTORCONTROLSYSTEM-041 created at QC-2026-03-21.

Next

Status set to qc-reviewed. System is ready for SE_REVIEW to assess holistic coherence and proportionality before marking complete. The reclassification of disruption prediction engine should be bundled into that session or run as a standalone Substrate call.