Small-break LOCA

Reactor at 100% rated thermal power; a 3-inch break in the Loop 1 cold leg develops between t = 0 and t = 30 s. RCS inventory loss drives pressurizer pressure below the SI setpoint at ~t = 30 s; the operator enters E-0 on safety-injection actuation, transitions to E-1 when LOCA symptoms are confirmed, and progresses through high-head SI verification. By t = 5 min the crew has high-head SI established and is monitoring RWST inventory to anticipate recirculation transfer per ES-1.3.

This scenario exercises the E-0 → E-1 → ES-1.3 path with no concurrent faults (single LOCA, both SI trains available, no SG faults). Multi-fault variants live in sb-loca-with-* sibling scenarios.

Initial state¶

{
  "PT-455": 2235,
  "SG-A-LVL-NR": 50,
  "SG-B-LVL-NR": 50,
  "SG-C-LVL-NR": 50,
  "SG-D-LVL-NR": 50,
  "RCS-TEMP-HOT": 612,
  "SUB-MARGIN": 35,
  "RWST-LVL": 92
}

Injections¶

[
  { "tag": "PT-455", "value": 1600, "at-time-s": 30 },
  { "tag": "RCS-TEMP-HOT", "value": 575, "at-time-s": 60 },
  { "tag": "SUB-MARGIN", "value": 12, "at-time-s": 120 }
]

Expected traversal¶

[
  "E-0#verify-reactor-trip",
  "E-0#verify-turbine-trip",
  "E-0#verify-ac-buses",
  "E-0#check-si-status",
  "E-0#verify-si-pumps",
  "E-1#verify-loca-symptoms",
  "E-1#verify-si-active",
  "E-1#check-rcs-pressure-trend",
  "E-1#monitor-rwst-level"
]

Expected terminal state¶

{
  "HHSI-PUMP-A": "RUN",
  "HHSI-PUMP-B": "RUN",
  "PT-455": 1600,
  "RWST-LVL": 80
}

EAL classification¶

This scenario classifies as Unusual Event (SU4) per the wiki's EAL rule table — pressurizer pressure drops below 1815 psig, triggering the RCS-leakage / inventory-loss IC. The scenario does not escalate to Alert because SI catches up at PT-455 = 1600 psig before pressure crosses the 1500 psig SA5 threshold. A variant scenario with a larger break or delayed SI would escalate; see future sb-loca-with-delayed-si.md.

References¶

Vogtle UFSAR §15.6.5 (small-break LOCA analysis)
NEI 99-01 EAL methodology
Westinghouse-style ERG procedures E-0, E-1, ES-1.3