System

STEP Fusion Power Plant {{entity:STEP Fusion Power Plant}} — second QC pass targeting the verification coverage gaps and trace-link deficiencies flagged in the previous decompose session. Entering this session: 207 requirements across 6 documents, 191 trace links, 3 orphan requirements ({{sub:ARC-SUB-009}}, {{sub:ARC-SUB-010}}, {{sub:ARC-SUB-011}}), and 28 SUB+IFC requirements without any VER link.

Findings

Verification coverage gap — 11 IFC requirements: {{ifc:IFC-REQ-010}} through {{ifc:IFC-REQ-020}} each had a corresponding VER entry ({{sub:VER-REQ-025}} through {{sub:VER-REQ-035}}) but lacked the verifies trace link. The VER text explicitly named each IFC source requirement, confirming genuine derivation. 11 IFC→VER links were missing.

Verification coverage gap — 17 SUB requirements: 17 of 47 subsystem requirements lacked VER trace links. For 11 of these ({{sub:SUB-REQ-003}}, {{sub:SUB-REQ-004}}, {{sub:SUB-REQ-006}}–{{sub:SUB-REQ-014}}), a VER entry existed but the link was absent. For 6 — {{sub:SUB-REQ-038}}, {{sub:SUB-REQ-039}}, {{sub:SUB-REQ-040}} (Remote Handling System radiation hardening, cask shielding, safe-state halt) and {{sub:SUB-REQ-043}}, {{sub:SUB-REQ-044}}, {{sub:SUB-REQ-045}} (Power Conversion System grid code, steam generator heat transfer, turbine runback) — no VER entry existed at all. Total: 28 SUB+IFC without verification, exceeding the 10% gate threshold.

Orphan ARC requirements: {{sub:ARC-SUB-009}}, {{sub:ARC-SUB-010}}, {{sub:ARC-SUB-011}} were architectural decomposition records for the Cryogenic Plant, Remote Handling System, and Power Conversion System respectively. All three lacked trace links to any SYS or SUB requirement, making them untraceable. The linkset architecture-decisions → system-requirements was available but unused.

Duplicate diagrams: Two pairs of duplicate diagrams detected — Remote Handling System Internal Components (diagram-1774370164603 and diagram-1774370168791) and Power Conversion System Internal Components (diagram-1774370165045 and diagram-1774370172127). Newer duplicates deleted, 10 diagrams retained.

Lint residual (49 findings, not addressed this session): High-severity findings include ontological mismatch — {{entity:fusion power plant}} classified without {{trait:Physical Object}} trait affecting {{sys:SYS-REQ-006}} and {{sys:SYS-REQ-007}}; {{entity:step fusion power plant}} flagged as {{trait:Biological/Biomimetic}} (likely false positive in the classifier — a tokamak is not biomimetic). The {{entity:isotope separation system}} flagged as {{trait:Functionally Autonomous}} without override constraints; this warrants a new SUB requirement in the next session. Coverage gap findings (findings 37–49) for STK concepts without SYS/SUB flow-down are genuine and deferred.

Corrections

11 IFC→VER trace links created: IFC-REQ-010 through IFC-REQ-020 linked to VER-REQ-025 through VER-REQ-035. Each link carries rationale explaining which measured parameter verifies the interface constraint.

11 SUB→VER trace links created: {{sub:SUB-REQ-003}}→VER-REQ-016 (PCS controller failover), {{sub:SUB-REQ-004}}→VER-REQ-015 (DAQ synchronous sampling), {{sub:SUB-REQ-006}}→VER-REQ-014 (disruption mitigation), {{sub:SUB-REQ-007}}→VER-REQ-017 (TCA heat flux), {{sub:SUB-REQ-008}}→VER-REQ-018 (SMS TF field), {{sub:SUB-REQ-009}}→VER-REQ-020 (Cryo 4.5K), {{sub:SUB-REQ-010}}→VER-REQ-019 (tritium accountability), {{sub:SUB-REQ-011}}→VER-REQ-021 (PCS 100MW export), {{sub:SUB-REQ-012}}→VER-REQ-022 (RHS 21-day campaign), {{sub:SUB-REQ-013}}→VER-REQ-023 (Vacuum pump-down), {{sub:SUB-REQ-014}}→VER-REQ-024 (RPS zoning).

6 new VER entries created: Test procedures written for RHS radiation hardening (Co-60 + neutron to 1×10^6 Gy, pass criterion ≤±1.1 mm positioning after irradiation), Transfer Cask biological shielding (ISO 2919 gamma survey at 0.1 m, pass ≤2 mSv/hr), RHS fault halt (hardware fault injection, pass ≤500 ms halt, 30-min load hold), PCS grid code compliance (400 kV/50 Hz/THD < 3%, National Grid ESO sign-off), steam generator heat transfer (enthalpy balance at Q≥5, pass ≥500 MWth, primary outlet ≤180°C), and turbine runback (disruption signal injection, pass 100%→20% load within 60 s, no trip).

3 ARC→SYS motivates links created: {{sub:ARC-SUB-009}} motivates {{sys:SYS-REQ-006}} (Cryo topology enables quench energy dump path); {{sub:ARC-SUB-010}} motivates {{sys:SYS-REQ-009}} (RHS decomposition basis for 21-day maintenance window); {{sub:ARC-SUB-011}} motivates {{sys:SYS-REQ-002}} (PCS separation of steam generators enables ≥25% efficiency).

Residual

Orphan count: 0/213. Verification coverage: 47/47 SUB requirements now have ≥1 VER link; 36/36 IFC requirements have ≥1 VER link. Duplicate diagrams: 0. Baseline QC-2026-03-24 tagged (213 requirements, 222 trace links).

Unresolved: 49 lint findings (9 high, 40 medium). Highest priority for next session: the {{entity:isotope separation system}} autonomy finding (needs a safety override SUB requirement); STK concept flow-down gaps for regulator compliance, remote handling capability, and net electrical power (findings 37–49 require 6–8 new SYS requirements). The Biological/Biomimetic false positive on the top-level system entity should be dismissed via entity reclassification.

Next

Verification coverage gate cleared. Project ready for validation pass. Recommend SE_VALIDATION session targeting: scenario walkthrough for disruption scenario (STK→SYS→SUB→VER chain for {{sys:SYS-REQ-004}}), tritium confinement chain ({{sys:SYS-REQ-005}}→{{sub:SUB-REQ-010}}→{{sub:vER-REQ-019}}), and the isotope separation system autonomy gap flagged by lint finding 9.

flowchart TB
  n0["Tokamak Core Assembly"]
  n1["Superconducting Magnet System"]
  n2["Cryogenic Plant"]
  n3["Tritium Plant"]
  n4["Power Conversion System"]
  n5["Plasma Control System"]
  n6["Remote Handling System"]
  n7["Vacuum System"]
  n8["Radiation Protection System"]
  n0 -->|Magnetic Field| n1
  n2 -->|4.5K Cooling| n1
  n3 -->|Fuel / Exhaust| n0
  n0 -->|Thermal Power| n4
  n5 -->|Control Commands| n0
  n5 -->|Coil Commands| n1
  n7 -->|Vacuum| n0
  n6 -->|Maintenance Access| n0
  n8 -.->|Shielding| n0