System

{{entity:Emergency Diesel Generator for a UK Nuclear Licensed Site}}, project se-edg-uk-nuclear. Interim QC pass scoped to changes since session 585, with particular attention to the {{entity:EDG Building and Support Systems}} requirements introduced in session 586. At session entry: 138 requirements, 128 trace links, 4 orphaned requirements. At close: 141 requirements, 137 trace links, 0 orphans, 12 baselines.

Findings

Orphaned requirements — 4/138 at session start. All four were introduced in session 586 for the building subsystem and lacked any trace linkage:

• {{sub:ARC-REQ-007}} — architectural decomposition record for the EDG building (Structure, HVAC, Flood/Drainage, Access Control sub-functions with SIL allocations). No informational tag; no parent SYS link.
• {{sub:SUB-REQ-034}} — Exhaust Silencer backpressure ≤50 mbar at turbocharger outlet. No SYS parent.
• {{sub:SUB-REQ-035}} — Drain and Spill Containment 110% of 4,000L day tank with MCR sump alarm. No SYS parent.
• {{sub:VER-REQ-041}} — Building integration test (HVAC auto-start, backpressure, sump alarm, fire damper). No verifies links.

Verification coverage gaps — 4 SUB requirements (031–033, 036) lacked VER entries. These were the building structural and ventilation requirements from session 586. Coverage was 53/57 (93%) — above the 10% gap gate — but below full closure.

Spray patterns — 2 flagged. {{sys:SYS-REQ-001}} (start within 10 seconds) had 5 child links; {{sys:SYS-REQ-010}} (engine protection trips) had 7 child links. Both are justified: SYS-REQ-010 decomposed into four independent hardwired protection functions (overspeed, coolant temp, oil pressure, overcurrent), each requiring a dedicated relay requirement. Not spurious.

Lint — 66 findings (4 high, 62 medium). The 4 high-severity items flagged ontological mismatch: “emergency diesel generator design” and “interface between the diesel engine assembly” lack the Physical Object trait. Both are correctly classified as abstract/functional concepts in context — the design document and logical interface are not physical assemblies — so no corrective requirements were created. The 62 medium findings are coverage gap alerts from concept text matching that have corresponding trace links already in place; they are false positives from the lint’s concept extraction.

All 138 requirements had rationale and verification set — no field-level gaps.

Corrections

Orphan resolution — 5 new trace links:

• {{sys:SYS-REQ-011}} → {{sub:ARC-REQ-007}} (derives): building decomposition decision derives from the fire/inter-train separation requirement. ARC-REQ-007 tagged informational.
• {{sys:SYS-REQ-005}} → {{sub:SUB-REQ-034}} (derives): exhaust backpressure limit protects sustained rated-load operation.
• {{sys:SYS-REQ-008}} → {{sub:SUB-REQ-035}} (derives): bund capacity design basis is the 4,000L day tank specified in SYS-REQ-008.
• {{sub:VER-REQ-041}} → {{sub:SUB-REQ-034}} (verifies): criterion (b) of the integration test.
• {{sub:VER-REQ-041}} → {{sub:SUB-REQ-035}} (verifies): criterion (c) of the integration test.
• {{sub:VER-REQ-041}} → {{sub:SUB-REQ-033}} (verifies): criterion (a) of the integration test.

New VER requirements — 3 created to close building VER gaps:

• VER-REQ-042 (Inspection): dimensional check of ≥600mm inter-train separation, per BS EN 61513, verifies {{sub:SUB-REQ-031}}.
• VER-REQ-043 (Test): calibrated anemometry at 100% rated load across 10/25/40°C ambient, verifies combustion air ≥0.55 kg/s ({{sub:SUB-REQ-032}}).
• VER-REQ-044 (Test): simulated structural breach signal to monitoring system, confirms EDG shutdown within 5 seconds and MCR alarm within 60 seconds, verifies {{sub:SUB-REQ-036}}.

Verification coverage after corrections: 57/57 (100%). All SUB and IFC requirements now have at least one VER entry.

Residual

Lint ontological mismatch findings (buildings, interfaces classified without Physical Object) remain open. These are classification artefacts, not requirement gaps; addressing them would require reclassifying abstract concepts as physical assemblies, which would misrepresent the engineering. Flagged as informational for next review.

Next

VER coverage is complete and orphans are resolved. Project is ready for validation pass (SE_VALIDATION). Focus for validation: confirm the seismic safety argument chain ({{sys:SYS-REQ-009}} → SUB-REQ-008, SUB-REQ-017, SUB-REQ-030, SUB-REQ-031, SUB-REQ-034, SUB-REQ-036), and verify that the LOOP signal initiation test chain (SYS-REQ-013 → SUB-REQ-019, VER-REQ-041) provides adequate surveillance test coverage per IEC 60780 (Nuclear power plants — Electrical equipment important to safety — Qualification).

flowchart TB
  n0["component - Ventilation and Combustion Air System"]
  n1["component - Exhaust Silencer and Discharge Stack"]
  n2["component - Fire Detection and Suppression System"]
  n3["component - Category 1 Building Structure"]
  n4["component - Drain and Spill Containment System"]
  n3 -->|air intake penetrations| n0
  n3 -->|exhaust penetration| n1
  n2 -->|fire/shutdown signal| n0
  n3 -->|floor drain collection| n4