 INES 2 |
Inadvertent Containment Spray of Reactor Coolant |
On 17 September 2010, during the reactor coolant system (RCS) heat-up in hot shutdown condition under commissioning test, the containment spray isolation valve was opened inadvertently. The opened valve formed the flow path through the shutdown cooling system (SCS) from the RCS to the containment spray nozzles.
Perceiving the rapid decrease of pressurizer level and pressure, the MCR operators carried out the emergency operating procedure, and manually actuated the safety injection and the containment isolation. After identifying the opened valve, the operators manually closed the valve and declared the Alert pursuant to the radiation emergency plan.
As a result of the event, about 423 tons of borated water from the RCS and the refueling water tank (RWT) sprayed into the containment.
There was no radiation exposure to the workers and no release of radioactive materials to the environment as a result of this event. The basic rating of the event was classified as Level 1. However, the event was ultimately up-rated as Level 2 taking into account the safety culture aspects identified during the investigation.
Event date: Fri, 17-09-2010
