System

{{entity:Fusion Reactor Control System}} [{{hex:51F77B19}}], session 395. The two remaining undecomposed subsystems — {{entity:Plant Control and I&C System}} [{{hex:50B53218}}] and {{entity:Plasma Diagnostics Integration System}} [{{hex:54E77308}}] — were decomposed this session. HCDC PART_OF facts, which were classified in session 391 but never linked, were also repaired. All eight top-level subsystems now have full component decomposition with 43 PART_OF facts across the SE:fusion-reactor-control-system namespace.

Decomposition

Plant Control and I&C System decomposes into five components reflecting a clear performance-tier separation: {{entity:Plant Operations Sequencer}} [{{hex:51B57A18}}] runs the reactor operating-state lifecycle in 1oo2 hot-standby; {{entity:Operator Console System}} [{{hex:54EC7B18}}] provides SCADA displays and alarm management; {{entity:Machine Timing and Synchronisation System}} [{{hex:51F77A18}}] distributes GPS-disciplined shot timing over fibre to all subsystems; {{entity:Plant I&C Network Infrastructure}} [{{hex:40857018}}] enforces three physically separated network zones; and {{entity:Plant Data Historian}} [{{hex:50841308}}] ingests 50 MB/s and retains pulse data for 25 years.

Plasma Diagnostics Integration System decomposes into {{entity:Magnetic Diagnostics Array}} [{{hex:54C57200}}], {{entity:Real-Time Diagnostic Signal Conditioner}} [{{hex:D4F55208}}], {{entity:Thomson Scattering and Interferometry System}} [{{hex:54C43210}}], {{entity:Disruption Precursor Sensor Suite}} [{{hex:54E55208}}], and {{entity:Diagnostic Data Multiplexer}} [{{hex:40F57308}}]. The Disruption Precursor Sensor Suite is separated from the Magnetic Array because they serve different consumers with different latency and bandwidth requirements: the Array feeds equilibrium reconstruction at 100 kHz; the Suite feeds the DPMS Disruption Precursor Monitor at 10 kHz with disruption-optimised processing.

flowchart TB
  n0["Fusion Reactor Control System"]
  n1["Plasma Control System"]
  n2["Disruption Prediction and Mitigation System"]
  n3["Heating and Current Drive Control"]
  n4["Magnet Safety and Protection System"]
  n5["Fuel Injection and Burn Control"]
  n6["Plasma Diagnostics Integration System"]
  n7["Plant Control and I&C System"]
  n8["Interlock and Emergency Shutdown System"]
  n0 -->|contains| n1
  n0 -->|contains| n2
  n0 -->|contains| n3
  n0 -->|contains| n4
  n0 -->|contains| n5
  n0 -->|contains| n6
  n0 -->|contains| n7
  n0 -->|contains| n8

Analysis

Lint identified 8 high-severity ontological mismatches. Three were addressed with real requirements; three were acknowledged as classification artefacts.

The most consequential findings were for the three {{trait:Functionally Autonomous}} components — {{entity:Disruption Precursor Monitor}}, {{entity:Equilibrium Reconstruction Processor}}, and {{entity:Disruption Prediction Engine}} — none of which had watchdog or override requirements. For safety-critical systems this is a genuine gap: an autonomous ML component (Disruption Prediction Engine) making actuation decisions toward the IESS without a watchdog or inhibit constraint violates the spirit of IEC 61508 functional safety for autonomous actuators. Three new requirements ({{sub:SUB-REQ-058}}, {{sub:SUB-REQ-059}}, {{sub:SUB-REQ-060}}) specify fail-safe watchdog behaviour for each.

The {{trait:Biological/Biomimetic}} classification of {{entity:Disruption Prediction Engine}} [{{hex:71F77308}}] is a known artefact from its ML pattern-recognition architecture; no biocompatibility requirements apply.

The {{entity:Machine Timing and Synchronisation System}} [{{hex:51F77A18}}] is distinct from all prior components in this decomposition by being classified with {{trait:System-integrated}} traits strongly aligned to infrastructure services rather than control functions — closer in trait profile to the {{entity:PCS Real-Time Data Bus}} [{{hex:40A57200}}] than to any controller.

Requirements

22 requirements created this session (SUB-REQ-050–060, IFC-REQ-023–028, VER-REQ-029–034, ARC-REQ-008–009). Key requirements:

• {{sub:SUB-REQ-050}}: Plant Operations Sequencer broadcasts machine state variable at 10 Hz to all subsystems in 8 defined states.
• {{sub:SUB-REQ-051}}: Sequencer failover to standby within 500 ms on heartbeat loss — derived from 1-second quench growth time ceiling.
• {{sub:SUB-REQ-052}}: MTSS delivers shot timing with ≤1 µs absolute accuracy and ≤5 µs inter-subsystem jitter. Derives from {{sys:SYS-REQ-001}}.
• {{sub:SUB-REQ-055}}: Real-Time Diagnostic Signal Conditioner delivers at ≤100 µs — the signal-conditioning allocation within the 1 ms plasma control loop.
• {{ifc:IFC-REQ-024}}: MTSS timing over fibre-optic only — mandated for EMI immunity against 50 kA magnet transients.
• {{ifc:IFC-REQ-028}}: DPSS to Disruption Precursor Monitor within 500 µs — derived as sensor delivery allocation from {{sys:SYS-REQ-002}}‘s 50 ms disruption budget.
• {{sub:SUB-REQ-058}}–{{sub:SUB-REQ-060}}: Watchdog and override constraints for three functionally autonomous components, addressing the lint high-severity findings directly.

Trace links close the derivation chain: SYS-REQ-001 → SUB-REQ-055/056, SYS-REQ-002 → IFC-REQ-028/SUB-REQ-057, SYS-REQ-005 → SUB-REQ-053/IFC-REQ-025.

Next

Project now has 141 requirements across all eight subsystems with 118 trace links. Verification coverage should be audited — several subsystem requirements added in earlier sessions have no VER entries. The project is approaching QC threshold; the next session should review for orphaned requirements, missing rationale on prior-session requirements, and completeness of the trace chain before a QC pass.