System

QC session on the {{entity:Emergency Diesel Generator for a UK Nuclear Licensed Site}} project (se-edg-uk-nuclear). Entry state: 116 requirements (4 homeless), 115 trace links, 11 diagrams. Exit state: 122 requirements, 119 trace links, 0 homeless. Baseline BL-SEEDGUKNUCLEAR-010 created.

Findings

Homeless requirements (4/116): REQ-SEEDGUKNUCLEAR-047 through 050 were verification procedures (GCB close-time acceptance test, GERP functional test, GERP trip circuit test, and I/O module isolation qualification) sitting outside any document. All four reassigned to verification-requirements; they now hold refs VER-REQ-028 through VER-REQ-031.

Spray pattern on {{sys:SYS-REQ-010}}: The engine protection trip circuit requirement carried 9 links to SUB and IFC requirements, all with null rationale. Analysis of each target revealed 2 spurious links: link-1774505309535 (to {{sub:SUB-REQ-013}}, Diesel Fuel Injection Class 1E power supply — related to the power architecture, not derived from the trip circuit requirement) and link-1774507199334 (to {{sub:SUB-REQ-018}}, Starting Air pressure inhibit — a distinct protection function, not a derivation of hardwired trip circuits). Both deleted. The remaining 7 links are genuine derivations — each implements one of the four named trip functions (overspeed, high coolant temperature, low oil pressure, overcurrent) or their relay architecture and physical interface. Rationale added to all seven.

Verification coverage gaps (4 SUB requirements unverified): {{sub:SUB-REQ-016}} (air receiver recharge capacity), {{sub:SUB-REQ-017}} (compressed air dewpoint), {{sub:SUB-REQ-018}} (pressure alarm and start inhibit), and {{sub:SUB-REQ-022}} (data diode unidirectionality) each lacked a VER entry. VER-REQ-032 through VER-REQ-035 created and linked. SUB VER coverage now 29/29.

EDG building coverage gap (lint finding 70): {{sys:SYS-REQ-011}} (fire detection and suppression, inter-train fire barriers) had no SUB decomposition. The “EDG Building and Support Systems” diagram existed but no requirements were assigned to it. {{sub:SUB-REQ-029}} created specifying gaseous total-flood suppression (HFC-227ea/CO2, 30-second extinguishment per BS EN 15004) and a two-hour fire-rated inter-train barrier per BS 476 Part 22, derived from hazard H-004 (SIL 2). Traced to SYS-REQ-011 and verified by VER-REQ-036.

Lint findings: 72 findings (3 high, 69 medium). The 3 high-severity findings are ontological mismatches where abstract concept names in lint-derived classifications lack the Physical Object trait; the underlying requirements are correctly specified and the mismatch is a lint artefact from how the semantic engine names concepts from requirement text (e.g., “emergency diesel generator design” is the concept extracted from ARC text, not a system entity). The 69 medium findings are primarily coverage-gap signals where lint concept names differ from the requirement text in lower-tier documents; the majority are false positives (e.g., “priority-based load sequencer” in SYS not in SUB — {{sub:SUB-REQ-010}} uses this exact phrase). Real gap addressed: building fire protection.

Ambiguous language: {{stk:STK-REQ-004}} uses “sufficient information” without enumerating the specific display parameters. Acceptable at stakeholder level; SYS and SUB requirements address the specific monitored values. No suppression needed.

Corrections

• Reassigned 4 homeless VER requirements to verification-requirements (VER-REQ-028 to VER-REQ-031)
• Deleted 2 spurious spray links on SYS-REQ-010; added substantive rationale to 7 genuine links
• Created VER-REQ-032 (SAS recharge test), VER-REQ-033 (dewpoint inspection), VER-REQ-034 (pressure alarm test), VER-REQ-035 (data diode test) — all with trace links to their parent SUB requirements
• Created SUB-REQ-029 (EDG building fire suppression and inter-train barrier), linked to SYS-REQ-011 and VER-REQ-036

Residual

The 3 high-severity ontological lint findings remain. They reflect the semantic classifier’s inability to match abstract concept phrases extracted from requirement text with the physical entities registered in the SE namespace. Reclassifying the entities would require the lint engine to re-extract concepts from the requirement text, and the conceptual names (“emergency diesel generator design”, “interface between the diesel engine assembly”) are not the same as the classified entity names in SE:edg-uk-nuclear. No requirements engineering action is needed.

STK-REQ-004 “sufficient information” is residual at acceptable risk — the downstream requirements are specific.

Next

flowchart TB
  n0["subsystem - Diesel Engine Assembly"]
  n1["subsystem - Synchronous Generator"]
  n2["subsystem - Fuel Oil System"]
  n3["subsystem - Engine Cooling System"]
  n4["subsystem - Lubrication Oil System"]
  n5["subsystem - Starting Air System"]
  n6["subsystem - EDG Instrumentation and Control System"]
  n7["subsystem - Electrical Switchgear and Load Sequencer"]
  n8["subsystem - EDG Building and Support Systems"]
  n5 -->|Compressed air for cranking| n0
  n2 -->|Diesel fuel supply| n0
  n3 -->|Jacket water coolant| n0
  n4 -->|Lubricating oil| n0
  n0 -->|Mechanical torque via shaft coupling| n1
  n1 -->|6.6kV 3-phase AC output| n7
  n0 -->|Speed, temp, pressure signals| n6
  n6 -->|Auto-start initiation| n5
  n6 -->|Governor control / trip| n0
  n6 -->|Breaker control commands| n7

Project is at 122 requirements (18 STK, 15 SYS, 29 SUB, 18 IFC, 6 ARC, 36 VER), 0 homeless, SUB coverage 100% verified. Ready for validation pass. The next session should run the full validation flow: scenario walkthrough against ConOps start-on-demand and LOOP scenarios, SIL chain check for H-004 (fire) and H-001 (failure to start), and verification adequacy sampling across the 36 VER requirements.