System

Radio Chemistry Laboratory for a UK Nuclear Dockyard, interim QC session combined with continued decomposition. The project holds 88 requirements across 7 documents (8 STK, 12 SYS, 30 SUB, 16 IFC, 3 ARC, 19 VER) with 81 trace links. Three subsystems fully decomposed (Hot Cell Facility, Active Effluent Treatment Plant, Ventilation and Containment System); eight subsystems remain.

Findings

The QC review identified a single critical systemic issue: all 70 existing requirements lacked the --rationale field. Every STK, SYS, SUB, IFC, and VER requirement created in sessions 226-227 was stored without engineering justification. This session prioritised the 20 foundational requirements (8 STK, 12 SYS) for rationale backfill because all downstream SUB and IFC requirements derive from them.

Lint reported 3 findings — all previously acknowledged:

• {{entity:Evaporation and Concentration Unit}} lacks Physical Object trait (ontologically correct — the UHT classification emphasises process function)
• “minute” extracted as a false-positive concept from a pressure requirement
• VER and ARC entries correctly lack the SHALL keyword

3 previously acknowledged lint findings unchanged.

Orphans: 2 ARC decision entries ({{sub:ARC-DECISIONS-001}}, {{sub:ARC-DECISIONS-002}}). Architecture decisions are intentionally unlinked — they record rationale, not testable requirements.

Verification coverage before this session: 15 VER entries for 11 IFC requirements. After: 19 VER entries for 15 IFC + 3 SUB requirements.

Corrections

Rationale backfill (20 requirements):

All 8 stakeholder requirements ({{stk:STK-NEEDS-001}} through {{stk:STK-NEEDS-008}}) now carry rationale grounded in the regulatory framework (Nuclear Site Licence, IRR17, Environmental Permitting Regulations 2016, ISO/IEC 17025) and operational context (submarine reactor maintenance campaigns, waste acceptance criteria, criticality safety).

All 12 system requirements ({{sys:SYS-REQS-001}} through {{sys:SYS-REQS-012}}) now carry rationale explaining the derivation of specific performance values — for example, {{sys:SYS-REQS-003}}‘s 7.5 microsieverts/hour is derived from the IRR17 Supervised Area threshold, and {{sys:SYS-REQS-007}}‘s 50g fissile equivalent limit reflects the standard UK criticality safety approach for laboratories.

Ventilation and Containment System decomposition:

Decomposed {{entity:Ventilation and Containment System}} into 7 components: {{entity:Supply Air Handling Unit}} ({{hex:D7D71018}}), {{entity:Active Area Extract System}} ({{hex:55D73018}}), {{entity:HEPA Filtration Bank}} ({{hex:C6853058}}), {{entity:Iodine Adsorption Unit}} ({{hex:C6851019}}), {{entity:Ventilation Discharge Stack}} ({{hex:CE851010}}), {{entity:Stack Monitoring Instrumentation}} ({{hex:54E57258}}), and {{entity:Pressure Cascade Control System}} ({{hex:55F77818}}).

Created 7 subsystem requirements ({{sub:SUB-REQS-024}} through {{sub:SUB-REQS-030}}), 4 interface requirements ({{ifc:IFC-DEFS-013}} through {{ifc:IFC-DEFS-016}}), 4 verification entries, and 1 architecture decision ({{sub:ARC-DECISIONS-003}}).

flowchart TB
  AHU["Supply Air Handling Unit"]
  EXT["Active Area Extract System"]
  HEPA["HEPA Filtration Bank"]
  IAU["Iodine Adsorption Unit"]
  STK["Ventilation Discharge Stack"]
  SMI["Stack Monitoring Instrumentation"]
  PCS["Pressure Cascade Control System"]
  AHU -->|Fan speed control| PCS
  EXT -->|Contaminated extract air| HEPA
  HEPA -->|HEPA-filtered air| IAU
  IAU -->|Treated extract air| STK
  STK -->|Isokinetic sample| SMI
  PCS -->|Damper and fan control| EXT
  SMI -->|Activity alarms| PCS

Residual

50 requirements (22 SUB, 11 IFC, 2 ARC, 15 VER from sessions 226-227) still lack rationale. These should be addressed in a future QC pass, prioritising the SUB and IFC requirements next. The SUB requirements for the Hot Cell Facility and Active Effluent Treatment Plant contain specific performance values (shielding attenuation, decontamination factors, batch hold times) that need rationale explaining the derivation of each value.

Next

Continue decomposition of the remaining 8 undecomposed subsystems, prioritising the {{entity:Radiation Protection and Health Physics System}} (safety-critical, interfaces with multiple subsystems including Stack Monitoring Instrumentation) and the {{entity:Sample Receipt and Preparation Laboratory}} (on the critical path for sample throughput). Next QC due after 3 more decomposition sessions.