System

{{entity:Radiochemistry Laboratory for a UK Nuclear Dockyard v2}} — validation session against real-world engineering for a nuclear-licensed analytical facility. Project state at entry: 249 requirements, 177 trace links, 53 classified entities across 13 subsystems, 15 diagrams, QC-reviewed status. This session assessed whether the decomposition accurately represents a real facility and addressed gaps found.

Assessment

The decomposition is strong in its core analytical domain. The four measurement subsystems — {{entity:Gamma Spectrometry Suite}}, {{entity:Alpha Spectrometry Laboratory}}, {{entity:Liquid Scintillation Counter Array}}, and {{entity:ICP-MS Instrument}} — are decomposed with realistic component counts, quantified performance requirements traceable to IAEA International Target Values, and complete interface chains. The {{entity:Active Ventilation and Containment System}} has correct depression cascade values (15 Pa per zone boundary) and twin-bank HEPA filtration with appropriate DOP testing requirements. The {{entity:Safety Interlock and Trip System}} correctly implements 2oo3 voting for SIL 3 functions per {{sub:SUB-REQ-037}}.

However, four significant gaps were found that a real facility of this type would require:

1. No cybersecurity requirements. The LIMS stores safeguards-relevant nuclear material accountancy data and connects to analytical instruments across the facility. The BMS is a SCADA system bridging OT and IT domains. ONR CNS guidance and NIS Regulations 2018 mandate cybersecurity controls.

2. No decommissioning requirements. LC35 is a nuclear site licence condition requiring design-for-decommissioning from day one. Surface finishes, material selection, and operational contamination records are essential for a facility handling open sources.

3. No safety system proof testing intervals. The 2oo3 voting architecture achieves SIL 3 only when combined with proof testing at defined intervals. Cross-domain analysis of the {{entity:Nuclear Reactor Protection System}} (0.91 trait similarity to {{entity:Safety Interlock and Trip System}} at {{hex:50F77859}}) confirmed this as standard practice.

4. No common cause failure defences. IEC 61511 requires CCF defences proportional to SIL. The {{entity:Nuclear Reactor Protection System}} analog and {{entity:Emergency Shutdown System}} both require diverse sensing — identical redundant sensors can all fail simultaneously from chemical attack or EMI in a laboratory environment.

Gaps

Stakeholder level: Missing decommissioning (LC35) and information security (NISR 2003, Classification Policy Framework) stakeholders. Added {{stk:STK-REQ-006}} and {{stk:STK-REQ-007}}.

System level: Missing LIMS cybersecurity controls (RBAC, MFA, AES-256, network segmentation) and decommissioning records database. Added {{sys:SYS-REQ-011}} and {{sys:SYS-REQ-012}}.

Subsystem level: Missing proof test intervals for SIL 3 functions (3-month interval per IEC 61511) and diverse sensing requirement for CCF defence. Added {{sub:SUB-REQ-099}} and {{sub:SUB-REQ-100}}.

Interface level: Missing BMS-to-Safety System network boundary. Added {{ifc:IFC-REQ-055}} specifying a unidirectional data diode ({{hex:D4C55058}}) preventing BMS compromise from affecting safety system integrity.

Verification level: Added {{stk:VER-REQ-069}} (proof test procedure), {{stk:VER-REQ-070}} (CCF beta factor analysis), and {{stk:VER-REQ-071}} (LIMS penetration testing).

Additions

10 new requirements across all document types, 9 new trace links, 1 new classified entity. Project now: 259 requirements, 186 trace links, 54 entities.

flowchart TB
  n0["Criticality Warning System"]
  n1["Fire Detection and Suppression"]
  n2["Safety Interlock and Trip System"]
  n3["Emergency Comms and Alarm"]
  n4["Emergency Power System"]
  n5["Spill Containment and Decon"]
  DD["BMS-Safety Data Diode"]
  BMS["Building Management System"]
  n0 -->|criticality trip signal| n2
  n0 -->|criticality alarm| n3
  n1 -->|fire zone trip| n2
  n1 -->|fire alarm| n3
  n2 -->|trip status| n3
  n4 -->|UPS power| n0
  n4 -->|UPS power| n1
  n4 -->|UPS power| n2
  n4 -->|emergency power| n3
  n2 -->|status only| DD
  DD -->|read-only display| BMS

Verdict

Pass. The core engineering decomposition is sound and the analytical measurement chain is realistic and well-quantified. The gaps found were in cross-cutting concerns (cybersecurity, decommissioning, safety system through-life management) rather than in the domain-specific decomposition itself — consistent with a project that focused correctly on the analytical mission before addressing supporting disciplines. All critical gaps have been addressed with traced, verified requirements. Status set to validated. Ready for final holistic review (Flow E).

Next

Flow E (SE_REVIEW) should assess the complete 259-requirement set holistically: coherence between original and validation-added requirements, proportionality of the decomposition across subsystems, and whether any validation additions created trace chain inconsistencies. The 24 orphaned requirements (mostly ARC decisions and late-added QC requirements) should be reviewed for trace coverage. The LIMS cybersecurity additions should be cross-checked against the existing BMS network segmentation requirement {{sub:SUB-REQ-093}} for consistency.