System

{{entity:Nuclear Reactor Protection System}} {{hex:55B77859}}, session 203. Three remaining subsystems — {{entity:Class 1E Power Supply Subsystem}}, {{entity:Test and Surveillance Subsystem}}, and {{entity:Communication and Display Subsystem}} — decomposed and baselined. All 8 subsystems now have component decompositions with requirements, interfaces, and verification entries. Status advanced to first-pass-complete. The project stands at 152 requirements, 135 trace links, 40 components across 8 subsystems.

Decomposition

Class 1E Power Supply Subsystem {{hex:54D73858}} — 5 components reflecting the uninterruptible power path from energy storage through conversion to distribution. {{entity:Station Battery Bank}} {{hex:D6D51058}} provides 125VDC for 4-hour station blackout coping. {{entity:Vital Bus Inverter}} {{hex:D4E73018}} converts DC to regulated 120VAC. {{entity:Isolation Transfer Switch}} {{hex:D4B73058}} provides <4ms seamless changeover to the regulated transformer alternate source. {{entity:Battery Charger}} {{hex:D4F53018}} recharges from Class 1E 480V MCC. {{entity:Class 1E Distribution Panel}} {{hex:D6A51058}} provides individually protected branch circuits to protection loads. Each of 4 divisions has an independent, identical power supply chain with no cross-connections.

flowchart TB
  MCC(["Class 1E 480V MCC"])
  BC["Battery Charger"]
  BB["Station Battery Bank"]
  VBI["Vital Bus Inverter"]
  RT(["Regulated Transformer"])
  ITS["Isolation Transfer Switch"]
  DP["Class 1E Distribution Panel"]
  PL(["Protection System Loads"])
  MCC -->|480VAC| BC
  BC -->|140VDC float charge| BB
  BB -->|125VDC| VBI
  VBI -->|120VAC preferred| ITS
  RT -->|120VAC alternate| ITS
  ITS -->|120VAC vital bus| DP
  DP -->|Protected branch circuits| PL

Test and Surveillance Subsystem {{hex:51A53959}} — 4 components structured around the IEEE 338 overlap testing boundaries. {{entity:Analog Channel Test Module}} {{hex:D7E57018}} injects precision signals into instrument channels. {{entity:Logic Test Cabinet}} {{hex:D1E77018}} exercises all 2-out-of-4 voting combinations. {{entity:Response Time Test Equipment}} {{hex:54A53218}} measures end-to-end channel response using non-intrusive LCSR and noise analysis. {{entity:Trip Breaker Test Circuit}} {{hex:54A43818}} uses hardwired interlocks to prevent simultaneous testing of series breakers.

flowchart TB
  RTE["Response Time Test Equipment"]
  ACT["Analog Channel Test Module"]
  LTC["Logic Test Cabinet"]
  TBT["Trip Breaker Test Circuit"]
  BP(["Bistable/Logic Processors"])
  RTB(["Reactor Trip Breakers"])
  CD(["Comm and Display"])
  RTE -->|Timing reference| ACT
  ACT -->|Test signals| BP
  LTC -->|Logic test inputs| BP
  TBT -->|Shunt trip test| RTB
  ACT -->|Channel test results| CD
  LTC -->|Test results| CD

Communication and Display Subsystem {{hex:54ED7859}} — 4 components enforcing the safety/non-safety isolation boundary. {{entity:Intra-Division Communication Bus}} {{hex:40E57258}} provides deterministic TDM data exchange within each division at ≤10ms worst-case latency. {{entity:Safety Parameter Display System}} {{hex:54CD7858}} presents RG 1.97 Category 1 variables to operators. {{entity:Safety Data Gateway}} {{hex:50C57058}} uses hardware-enforced unidirectional fiber optic links — no receive photodiode on the safety side. {{entity:Alarm and Status Annunciator}} {{hex:D6ED7018}} provides hardwired relay-driven first-out indication independent of the digital platform.

flowchart TB
  PP(["Protection Processors"])
  IDCB["Intra-Division Comm Bus"]
  SPDS["Safety Parameter Display"]
  SDG["Safety Data Gateway"]
  ASA["Alarm and Status Annunciator"]
  OPS(["Control Room Operators"])
  PPC(["Plant Process Computer"])
  PP -->|Divisional data| IDCB
  PP -->|Hardwired status contacts| ASA
  IDCB -->|Safety parameters| SPDS
  IDCB -->|Status data| SDG
  SDG -->|One-way data| PPC
  SPDS -->|Display| OPS
  ASA -->|Alarms| OPS

Analysis

Lint returned 5 findings: 1 high ({{entity:Containment Environment Monitor}} {{hex:54A53058}} lacks Physical Object trait — acknowledged as ontologically correct for a monitoring function), 1 medium (abstract “year” metric in {{arc:ARC-DECISIONS-001}} — adequate in MTBF context), and 3 low (physical/abstract classification ambiguity for system-level entities, and architecture decisions and verification entries not using SHALL by convention). No medium/high severity issues requiring correction. 9 orphaned requirements are all architecture decisions, which by convention are unlinked rationale records.

Verification coverage stands at 38/85 SUB+IFC requirements (44%). The QC session must close the remaining gap to reach 50%+ coverage, particularly for the subsystems decomposed in sessions 199-202.

Requirements

This session created 18 subsystem requirements ({{sub:SUB-REQS-035}} through {{sub:SUB-REQS-052}}), 13 interface requirements ({{ifc:IFC-DEFS-022}} through {{ifc:IFC-DEFS-034}}), 16 verification entries ({{sub:VER-METHODS-023}} through {{sub:VER-METHODS-038}}), and 3 architecture decisions ({{arc:ARC-DECISIONS-007}} through {{arc:ARC-DECISIONS-009}}). All new requirements traced to parent system requirements and all new interface requirements have corresponding verification entries. Key requirements include the 4ms transfer switch changeover ({{sub:SUB-REQS-037}}), hardware-enforced gateway unidirectionality ({{sub:SUB-REQS-049}}), and the hardwired breaker test interlock ({{sub:SUB-REQS-045}}).

Next

System is first-pass-complete. Next session should execute Flow C (QC Review): review all 152 requirements for testability and ambiguity, close the verification coverage gap to ≥50%, check for missing cross-subsystem interfaces (particularly Class 1E Power Supply connections to every other subsystem), and validate that degraded-mode requirements have quantified performance floors.