System

Interim QC for {{entity:Radio Chemistry Laboratory for a UK Nuclear Dockyard}}, project se-radiochem-lab. Decomposition status remains in-progress — 5 of 12 subsystems have component-level decomposition ({{entity:Hot Cell Facility}}, {{entity:Active Effluent Treatment Plant}}, {{entity:Ventilation and Containment System}}, {{entity:Radiation Protection and Health Physics System}}, {{entity:Solid Radioactive Waste Management System}}). Seven analytical subsystems remain undecomposed. Project stands at 138 requirements across 7 documents, 128 trace links, and 12 diagrams.

Findings

The primary finding was a systemic rationale gap: 109 of 129 requirements lacked --rationale at session start. Only the original stakeholder ({{stk:STK-NEEDS-001}}–{{stk:STK-NEEDS-008}}) and system-level ({{sys:SYS-REQS-001}}–{{sys:SYS-REQS-012}}) requirements had engineering justification. All subsystem, interface, architecture, and verification entries created in sessions 225–230 were missing rationale.

Scoped to sessions 229–230 (the 43 requirements created since last QC at session 228), the breakdown was: 10 SUB requirements (Radiation Protection), 5 IFC requirements (RadPro interfaces), 9 SUB requirements (Solid Waste Management), 5 IFC requirements (Solid Waste interfaces), 12 VER entries, and 2 ARC decisions — all without rationale.

Verification coverage stood at 42% (31/73 SUB+IFC requirements covered). All 25 IFC requirements had VER entries, but only 6 of 48 SUB requirements did.

Lint reported 4 findings: 2 high-severity ontological mismatches ({{entity:Modbus TCP}} and {{entity:Evaporation and Concentration Unit}} classified without Physical Object trait despite physical constraints in requirements), 1 low-severity ambiguity between {{entity:Active Effluent Storage Tanks}} and {{entity:Evaporation and Concentration Unit}} (71% Jaccard), and 1 low-severity note about 36 entries lacking “SHALL” (correctly: ARC decisions and VER methods). Three findings were previously acknowledged; the Modbus TCP finding is new and ontologically correct — it is a protocol, not a physical object, and its timing constraints apply to data transfer.

One orphan identified: {{sub:SUB-REQS-034}} is a truncated duplicate of {{sub:SUB-REQS-031}}, already tagged duplicate-of-SUB-REQS-031.

Corrections

Added engineering rationale to all 38 requirements from sessions 229–230: 19 SUB requirements with domain-specific justifications referencing IRR17 regulations, ONR Safety Assessment Principles, IAEA standards, RWM guidance, and LLWR Waste Acceptance Criteria. 10 IFC requirements with rationale explaining the engineering basis for interface parameters (dual-path analogue/digital architecture, hardwired safety independence, database query performance, data transfer timing). 7 VER entries with rationale explaining why each test procedure validates its parent requirement. 2 ARC decisions with rationale explaining design trade-offs.

Created 7 new verification entries to raise SUB coverage from 6 to 13 of 48 SUB requirements, bringing total VER coverage to 52% (38/73):

• {{sub:SUB-REQS-031}} → {{sub:VER-METHODS-032}}: ionisation chamber range and spatial coverage
• {{sub:SUB-REQS-032}} → {{sub:VER-METHODS-033}}: alarm threshold accuracy and 5-second response
• {{sub:SUB-REQS-036}} → {{sub:VER-METHODS-034}}: criticality warning system independence
• {{sub:SUB-REQS-037}} → {{sub:VER-METHODS-035}}: personal dosemeter accuracy and alarm thresholds
• {{sub:SUB-REQS-041}} → {{sub:VER-METHODS-036}}: waste sorting categorisation
• {{sub:SUB-REQS-042}} → {{sub:VER-METHODS-037}}: NDA measurement uncertainty
• {{sub:SUB-REQS-033}} → {{sub:VER-METHODS-038}}: airborne contamination MDC and radon compensation

Acknowledged the Modbus TCP ontological mismatch lint finding as correct classification.

flowchart TB
  RP["Radiation Protection System"]
  AGM["Area Gamma Monitoring"]
  ACM["Airborne Contamination Monitors"]
  SCE["Surface Contamination Equipment"]
  PDS["Personal Dosimetry System"]
  RAC["Radiological Access Control"]
  CWS["Criticality Warning System"]
  CMD["Central Monitoring Display"]

  AGM -->|dose rate + alarms| CMD
  ACM -->|airborne activity + alarms| CMD
  CWS -->|criticality alarm status| CMD
  PDS -->|cumulative dose data| CMD
  PDS -->|dose-based access| RAC
  SCE -->|contamination results| CMD

Residual

Requirements from sessions 225–228 (71 entries) still lack rationale — these predate the scope of this interim QC but represent ongoing technical debt. The duplicate {{sub:SUB-REQS-034}} remains in the project tagged as duplicate; it should be removed or formally superseded in a future session. Five ARC decisions remain orphaned (no trace links), which is acceptable as architecture decisions are reference material rather than traceable requirements.

Next

Continue decomposition of the seven undecomposed analytical subsystems, prioritising {{entity:Sample Receipt and Preparation Laboratory}} (highest interface count with other subsystems) and {{entity:Radiochemical Separations Laboratory}} (highest safety criticality among the remaining subsystems). The rationale backfill for sessions 225–228 requirements should be addressed in the next interim QC cycle.