A limiting condition for operation is a technical specification setting the minimum equipment capability or plant condition required to stay in a given operating mode, such as two operable trains of a safety system. When an LCO is not met, the plant enters its action statement, which sets a completion time to restore the equipment, often 72 hours for one inoperable train, or else forces a power reduction or shutdown. Operators track every open LCO on a status board.
Diesel B is inoperable, we're in a 72 hour LCO, so the clock started at 0215.
Entering an LCO is not a violation; failing to complete the required action within its completion time is.
Also heard as
- limiting condition for operation
Related terms
Single failure criterion
The design rule that a safety system must still do its job despite any one component failing.
Redundancy
Providing more components or trains than needed, so a safety function survives if one fails.
Safety culture
The shared attitudes and behaviours in an organisation that give nuclear safety overriding priority.
Shutdown margin
How far subcritical a reactor would be with all rods inserted except the single most valuable one stuck out.