Concept of Operations (ConOps) — ISO/IEC/IEEE 15289 — Description | IEEE 29148 §6.1
Generated 2026-03-27 — UHT Journal / universalhex.org
Ensure continuous cooling of reactor fuel by providing standby electrical power during loss-of-offsite-power events at UK nuclear licensed sites
| Stakeholder | Relationship | Hex Code |
|---|---|---|
| Control Room Operator | Primary operational interface, monitors EDG status and initiates manual controls | — |
| Shift Supervisor | LCO and emergency decisions, authorises maintenance | — |
| Mechanical Technician | Engine maintenance and repair | — |
| I&C Technician | Control and protection system maintenance | — |
| ONR | Regulatory approval and safety case assessment | — |
| Licensee | Ultimate safety responsibility for the nuclear site | — |
| EDG OEM | Technical support, spare parts, overhaul services | — |
| Local Community | Expects accident prevention and environmental protection | — |
| Mode | Description |
|---|---|
| Standby Ready | Post-maintenance/test state, awaiting LOOP signal |
| Emergency Start | LOOP detected, engine cranking to rated V/Hz in 10 seconds |
| Running Loaded | Load sequencing complete, supplying emergency AC bus |
| Cooldown Shutdown | Offsite power restored, controlled engine cooldown |
| Surveillance Test | Scheduled monthly start test demonstrating readiness |
| Maintenance Out-of-Service | LOTO applied, planned maintenance or overhaul |
| Degraded Operation | Fault detected while running, reduced capability |
02:30 LOOP detected, both trains start, operator monitors from control room, load sequencing completes in 60 seconds
Stuck fuel solenoid prevents cranking, maintenance intervention required, alternate EDG takes load
Cooling fan belt failure causes high-temp trip, operator transfers to alternate EDG
Scheduled test demonstrating 9.8-second start-to-rated, load acceptance verified
Common-cause loss of both EDGs, mobile generator deployment, DC battery coping time critical
14-day outage during refuelling, LOTO applied, PMT required before return to service
| Category | Constraint |
|---|---|
| Seismic | Category I structure, 0.2g PGA design basis per EUR requirements |
| Environmental | -10C to +40C ambient, IP54 minimum, coastal atmosphere corrosion protection |
| EMC | IEC 61000-4 immunity, no spurious actuation from electromagnetic interference |
| Reliability | 0.975 start-on-demand probability, 0.999 24-hour mission reliability |
| Fuel | 7-day inventory at 100% load, EN 590 quality, diverse supply route |
| Timing | 10-second start-to-rated-voltage, 15-second full load acceptance |
| System | Interface | Hex Code |
|---|---|---|
| National Grid | LOOP detection signal, normal power source | — |
| Emergency AC Bus | 6.6kV AC power output to safety loads | — |
| Plant Protection System | Start/stop commands and status signals | — |
| Main Control Room | HMI data display and manual controls | — |
| Ultimate Heat Sink | Cooling water supply for engine and alternator | — |
| Fuel Supply | Diesel fuel from day tank and bulk storage | CE851018 |
| DC Battery System | 110V DC control power and engine starting | — |
flowchart TB n0["system<br>Emergency Diesel Generator for a UK Nuclear Licensed Site"] n1["actor<br>DC Battery System"] n2["actor<br>Emergency AC Bus"] n3["actor<br>Plant Protection System"] n4["actor<br>Main Control Room"] n5["actor<br>National Grid"] n6["actor<br>Ultimate Heat Sink"] n7["actor<br>Fuel Supply"] n3 -->|Start/stop command| n0 n1 -->|110V DC control power| n0 n0 -->|6.6kV Class 1E power| n2 n0 -->|Status and alarms| n4 n5 -->|LOOP detection signal| n0 n7 -->|Diesel fuel| n0 n6 -->|Cooling water| n0
Emergency Diesel Generator — System Context