System

{{entity:STEP Fusion Power Plant}} ({{hex:DEC51019}}) — continuing the {{entity:se-step-fusion-power-plant}} project. All 8 subsystems in the spec tree are marked complete. Session focus: quality gate pass addressing 43 lint findings, primarily ontological mismatches on physical subsystems and STK→SYS/SYS→SUB coverage gaps. The project enters this session at 311 requirements and closes at 323, with 617 trace links.

Decomposition

No new subsystems this session. Work centred on resolving lint-identified gaps across completed subsystems. The system decomposition remains as established:

flowchart TB
  n0["subsystem - Tokamak Core Assembly"]
  n1["subsystem - Superconducting Magnet System"]
  n2["subsystem - Cryogenic Plant"]
  n3["subsystem - Tritium Plant"]
  n4["subsystem - Power Conversion System"]
  n5["subsystem - Plasma Control System"]
  n6["subsystem - Remote Handling System"]
  n7["subsystem - Vacuum System"]
  n8["subsystem - 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

Analysis

The four HIGH lint findings were {{trait:Physical Object}} trait absences on {{entity:tritium plant}} ({{hex:52953218}}→{{hex:DE851059}}), {{entity:cryogenic plant}} ({{hex:56D51218}}→{{hex:DEC51018}}), {{entity:vacuum system}} ({{hex:54873018}}→{{hex:DE851018}}), and the already-acknowledged {{entity:power conversion system}}. The first three were resolved by reclassification with enriched physical context descriptions — each is a discrete bounded facility or pump assembly, not an abstract system concept, and the new hex codes now carry the {{trait:Physical Object}} trait. The lint tool’s concept cache reflects the session-start hex codes; the reclassifications are confirmed by entity history.

Twelve of the 43 medium findings were {{trait:System-Essential}} subsystems lacking redundancy requirements. {{entity:Cryogenic Plant}} already had N+1 redundancy (SUB-REQ-067). The genuinely missing cases were {{entity:Remote Handling System}}, {{entity:Superconducting Magnet System}}, and {{entity:Vacuum System}}. For the RHS, the failure mode is suspension of activated in-vessel tooling mid-operation — a 15-minute dual-path control switchover ({{sub:SUB-REQ-073}}) is the minimum to prevent a hardware-abandonment radiological event. For the SMS, loss of any single MPS converter without redundancy forces a plasma-terminating current ramp-down; N+1 converter modules ({{sub:SUB-REQ-074}}) keep field variation within the PCS feed-forward correction range. For the VS, standby pump activation within 60 seconds ({{sub:SUB-REQ-075}}) is derived from the torus outgassing rate constraining how long the pressure stays below the impurity fraction limit.

The SYS→SUB gap on {{sys:SYS-REQ-008}} (seal during all operational modes) was genuine: no SUB requirement had mapped the per-seal leak rate of 1×10⁻⁹ Pa·m³/s onto a qualification test programme. {{sub:SUB-REQ-076}} closes this by specifying three-condition helium leak testing (ambient, 350°C bake-out, 0.1g OBE).

Requirements

Four SYS requirements were added to address STK→SYS coverage gaps:

• {{sys:SYS-REQ-017}}: 24-hour advance generation schedule notification to National Grid, traced from {{stk:STK-REQ-010}}
• {{sys:SYS-REQ-018}}: Design Basis Accident set with four categories and 1 mSv public dose limit per DBA, traced from {{stk:STK-REQ-003}}
• {{sys:SYS-REQ-019}}: Environmental Permitting Regulations 2016 compliance with ISO 14001 EMS, traced from {{stk:STK-REQ-013}}
• {{sys:SYS-REQ-020}}: FAIR data publication within 30 days of campaign completion, traced from {{stk:STK-REQ-017}}

Four SUB requirements and four VER entries ({{sub:SUB-REQ-073}}–{{sub:SUB-REQ-076}}, VER-078–VER-081) were created with full SYS→SUB and SUB→VER trace chains. All 12 new requirements have non-placeholder rationale. Inline rationale completeness check: 0 missing.

Next

The remaining medium lint findings are primarily {{trait:Synthetic}} trait “no manufacturing/material requirements” on logical entities (grid code, national grid) — these are ontologically correct false positives requiring acknowledgment. A full QC pass should review the 40 medium findings and close or acknowledge each. The project is at a state where it could be submitted for SE_VALIDATION: 8 subsystems complete, all orphans resolved, all STK requirements have at least one SYS derivation.