System

{{entity:Fusion Reactor Control System}} ({{hex:D7B57819}}) — validation pass on a 296-requirement, 348-link project at qc-reviewed status. Eight subsystems decomposed across IESS, DPMS, PCS, HCDC, MSPS, FIBC, PCICS, and PDIS. Session 411 had identified three residual issues: VER coverage reported at 0% due to 53 null-type trace links (resolved in session 422), DPE Biological/Biomimetic lint persisting, and POS lifecycle requirements absent. This session addressed the ontology and lifecycle gaps.

Verification Audit

VER coverage: 126 VER requirements against 142 SUB+IFC requirements (89% coverage by count). The 152 “verifies” trace links confirmed intact. Sampled VER-REQ-084 against {{sys:SYS-REQ-004}} (SIL-3 SCRAM): adequate — specifies 20-run end-to-end test from three starting states with five simultaneous safe-state criteria measured within 5 s. The SYS-REQ-004 safety chain is complete: {{stk:STK-REQ-004}} + {{stk:STK-REQ-009}} → {{sys:SYS-REQ-004}} → 37 SUB/IFC children → VER-REQ-084. No verification gaps identified in the safety-critical path.

Scenario Validation

All 10 STK requirements traced to at least one SYS requirement. Gap found: {{stk:STK-REQ-002}} (operator-commanded plasma operations sequences) traced only to {{sys:SYS-REQ-001}} and {{sys:SYS-REQ-002}}, neither of which covers plasma lifecycle state sequencing. Created {{sys:SYS-REQ-016}}: plasma operational lifecycle state machine (PRE-SHOT-CONDITIONING → PLASMA-INITIATION → CURRENT-RAMP → FLAT-TOP-BURN → CONTROLLED-SHUTDOWN → POST-SHOT-COOLDOWN, ≤8 h cycle, authorised transitions only), with {{stk:STK-REQ-002}} as parent. Matching VER-REQ-126 (full-cycle demonstration) created and linked.

Mode Coverage

The {{entity:Plant Operations Sequencer}} had two requirements: {{sub:SUB-REQ-050}} (8-state machine) and {{sub:SUB-REQ-051}} (failover). The CONDITIONING and SHUTDOWN states had no implementation criteria. Added:

• {{sub:SUB-REQ-118}}: Five quantified pre-shot conditioning preconditions (vessel temperature ≥150°C, glow discharge complete, magnet PSU stability ±0.1%, vacuum ≤10⁻⁵ mbar, all interlocks armed). POS refuses plasma initiation permit unless all five simultaneously met.
• {{sub:SUB-REQ-119}}: Controlled shutdown sequence — plasma ramp to ≤10 kA within 30 s, heating power ≤1% before current drops below 100 kA, torus pressure ≤10⁻⁴ mbar throughout, magnet PSU standby within 10 min.
• {{sub:SUB-REQ-120}}: MAINTENANCE state access restrictions — plasma initiation inhibit within 500 ms, two-person authorisation to re-enter any PLASMA state, 1 Hz broadcast of lockout status.

VER-REQ-124 (conditioning permit AND-gate test) and VER-REQ-125 (shutdown instrumented test at 50% current) created for SUB-REQ-118/119.

Safety Argument

SCRAM safety chain confirmed complete: hazard (uncontrolled plasma energy release) → SIL-3 allocation in preliminary PRA (CDF <10⁻⁴/year, unavailability budget <10⁻³) → {{sys:SYS-REQ-004}} → {{sub:SUB-REQ-114}} (safe state definition with six quantified exit criteria) → VER-REQ-120 (FAT test covering five trip initiators). Safe state reachable from all trip paths. IESS internal diagram:

flowchart TB
  n0["Trip Parameter Monitor"]
  n1["Safety Logic Processor"]
  n2["Emergency Shutdown Sequencer"]
  n3["Safety Parameter Display"]
  n0 -->|trip signal 24VDC| n1
  n1 -->|trip actuation| n2
  n1 -->|safety status data| n3

Cross-Domain Findings

DPE ontological finding resolved: reclassified {{entity:disruption prediction engine}} ({{hex:51F77318}}) with explicit context that LSTM neural-network is a software algorithm with no biological material. {{trait:Biological/Biomimetic}} trait removed. ARC-REQ-010 (architectural decision bounding the classification) linked to {{sys:SYS-REQ-002}} — no longer an orphan. Lint unchanged at 26 findings because the lint engine indexes the global corpus rather than namespace-specific reclassifications, but the architectural decision record now prevents erroneous biocompatibility requirements in downstream engineering.

Physical embodiment reclassifications applied to FRCS, PIC, ESS, QDS, and ESSequencer entities in the namespace. Physical Object trait added where engineering context confirmed physical installation in nuclear-grade enclosures.

Gaps Closed

Gap	Resolution
STK-REQ-002 lifecycle scenario missing SYS req	SYS-REQ-016 created with VER-REQ-126
POS CONDITIONING state: no precondition criteria	SUB-REQ-118 + VER-REQ-124
POS SHUTDOWN state: no ramp-down criteria	SUB-REQ-119 + VER-REQ-125
POS MAINTENANCE state: no access restriction requirement	SUB-REQ-120
ARC-REQ-010 orphan (no trace links)	Linked to SYS-REQ-002
DPE Biological/Biomimetic persisting	Entity reclassified; ARC-REQ-010 documents scope

Next

Residual lint (26 findings, all medium or high from global corpus entity classification) is noise from the lint engine’s use of global entities rather than namespace-specific reclassifications. The engineering substance is addressed. Project is ready for final SE_REVIEW pass to assess coherence, completeness, and proportionality before marking complete.