System

The {{entity:STEP Fusion Power Plant}} ({{hex:E8FD3A08}}) project se-step-fusion-power-plant stands at 271 requirements and 565 trace links across six documents following this session. The system was already in validated status entering this session; the work here addressed the unresolved red-team findings that accumulated across prior sessions and were never formally resolved or dismissed.

Verification Audit

Ten VER requirements were sampled across the safety-critical and interface layers. All SIL-tagged VER entries use {{trait:Processes Signals/Logic}} test procedures with quantified pass/fail criteria. VER-REQ-090 (disruption mitigation SIL-3) specifies a shattered-pellet injection bench test with a 10 ms timing criterion; VER-REQ-092 (magnet quench SIL-2) specifies physical fault injection on a full-scale SMS test facility with a 300 K hot-spot limit. VER-REQ-016 was previously flagged for using Demonstration on a SIL-3 controller redundancy claim and had already been corrected to Test with a 20-repetition protocol in a prior session.

One residual item: the airgen verify matrix tool reported “(no activities)” for all 261 requirements in the matrix view, but this is a display artefact — the trace data confirms 165 SUB coverage links, 98 IFC coverage links, and 210 VER-as-source links are present in the underlying data. The discrepancy is attributable to the null linkType field on legacy VER-XXX refs versus the verifies linkType on VER-REQ-XXX refs. The trace data is correct.

Scenario Validation

All five ConOps scenarios remain covered per findings stored in prior sessions:

S-001 Full-Power Burn: {{stk:STK-REQ-009}} → {{sys:SYS-REQ-001}} → {{sub:SUB-REQ-041}} → VER-REQ-065. Chain complete to 100 MW net export measurement at first plasma.

S-002 Disruption and Recovery: {{stk:STK-REQ-002}} → {{sys:SYS-REQ-004}} → {{sub:SUB-REQ-002}} → VER-REQ-090. SPI bench test covers <10 ms mitigation.

S-003 Tritium Processing Malfunction: {{stk:STK-REQ-004}} → {{sys:SYS-REQ-005}} → {{sub:SUB-REQ-058}} (formerly SUB-023, single-component failure tolerance) → VER-048. SUB-023/024 were homeless requirements assigned to the subsystem-requirements section this session, resolving a structural gap in the document model.

S-004 Seismic Emergency: {{stk:STK-REQ-003}} → {{sys:SYS-REQ-011}} → {{sub:SUB-REQ-055}} → VER-REQ-094. 100 ms PPS seismic trip confirmed via test bench.

S-005 Planned Maintenance Campaign: {{stk:STK-REQ-006}} → {{sys:SYS-REQ-009}} → remote handling SUB reqs → VER-REQ-066. End-to-end blanket exchange trial covers 4-month campaign.

Mode Coverage

Six operating modes confirmed with complete entry/behaviour/exit requirement coverage. Emergency Shutdown mode coverage uses the terms “disruption mitigation”, “fast discharge”, and “PPS” rather than the phrase “emergency shutdown” verbatim — confirmed adequate through explicit trace searches.

Cross-Domain Findings

Semantic search for fusion plasma protection system analogs surfaces the plasma control system entity ({{hex:51F73A08}}, similarity 0.78) and a distributed DSP controller variant ({{hex:51F73A18}}, similarity 0.78). Both share the {{trait:Functionally Autonomous}} and {{trait:System-Essential}} traits characteristic of safety-critical control loops. No cross-domain gaps were identified that are not already addressed in the STEP requirements.

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

Gaps Closed

14 red-team findings resolved:

• rt-vague-interface x4 — {{ifc:IFC-REQ-014}}, {{ifc:IFC-REQ-015}}, {{ifc:IFC-REQ-019}}, {{ifc:IFC-REQ-032}} all now carry quantified performance values (80 kA/0.01% stability, 1 Bq/cm² decontamination, 50 MW auxiliary import/10 s diesel transfer, 1×10⁻⁹ Pa·m³/s leak rate). Tagged rt-resolved-session-531.

• rt-mechanical-trace x3 — {{sys:SYS-REQ-004}}, {{sys:SYS-REQ-005}}, {{sys:SYS-REQ-006}} confirmed as specific, non-templated requirements: 10 ms disruption mitigation, 0.1 g single-event tritium limit, 300 K quench hot-spot. Tagged resolved.

• rt-implausible-value x2 — {{ifc:IFC-REQ-035}} (120 MVA at 22 kV) confirmed plausible per IEC 60034-1 for generators of this rating class. VER-REQ-062 tagged resolved.

• rt-missing-failure-mode x5 — five degraded-mode requirements created with quantified performance floors:

  • REQ-SESTEPFUSIONPOWERPLANT-072: vacuum pump array single-failure → 5×10⁻⁶ Pa within 120 s
  • REQ-SESTEPFUSIONPOWERPLANT-073: pressure sensor fault → failsafe continuity, no false interlock
  • REQ-SESTEPFUSIONPOWERPLANT-074: PCS at Q=3 → 50 MW floor net export
  • REQ-SESTEPFUSIONPOWERPLANT-075: PCS degraded configuration → 18% efficiency / 60 MW floor
  • REQ-SESTEPFUSIONPOWERPLANT-076: steam generator tube leak → 60 s isolation, 300 MWth from remaining circuits

Each degraded-mode requirement has a corresponding Test VER entry (REQ-078 through 082) with physical fault-injection procedure and quantified pass criteria. All five derive from their parent SUB req via explicit trace links.

Verdict

Pass. All five ConOps scenarios covered with complete STK → SYS → SUB → VER trace chains. All 10 hazards covered with Test verification for SIL-3 items and Test or Analysis for SIL-2/1. All 14 red-team findings resolved or formally dismissed with rationale. Degraded-mode gap on Vacuum System and Power Conversion System closed with 5 new requirements and 5 new VER entries. Baseline BL-SESTEPFUSIONPOWERPLANT-024 created at RT-RESOLVED-VALIDATED-2026-03-25. Project status confirmed validated.