ENS 46631

v t e ENS Event
15:34 Feb 20, 2011
Title	Reactor Protection System Actuation While Shutdown
Event Description	On Sunday, February 20, 2011, at 1034 EST with the reactor shutdown and all control rods fully inserted a valid Reactor Protection System (RPS) low reactor water initiation signal (+12 inch) was received. The RPS actuation signal resulted in reactor scram and actuation of the Primary Containment Isolation Systems for Group II - Primary Containment Isolation and Reactor Building Isolation System (RBIS), and Group VI - Reactor Water Cleanup System (RWCU). At the time of the event, a controlled reactor shutdown and cooldown was in progress. The Reactor Mode Selector Switch was in 'Startup' and a cooldown was being controlled using the Mechanical Hydraulic Control (MHC) System. Initial event review indicates that the turbine by-pass valve controlling the cooldown closed causing a 'shrink' on indicated reactor water level to briefly lower to +12 inches (lowest observed water level). Reactor water level was immediately restored, the isolations (Group II and VI) were reset, and the RPS signal was reset at 1135 EST. All systems operated as expected, in accordance with design. This event had no impact on the health and/or safety of the public. The US NRC Senior Resident Inspector was in the Main Control Room at the time of the event. The licensee will be notifying the State.

ENS 46631 +/-
Where
Pilgrim Massachusetts (NRC Region 1)
Reporting

10 CFR 50.72(b)(3)(iv)(A), System Actuation
Time - Person (Reporting Time:+2.22 h0.0925 days <br />0.0132 weeks <br />0.00304 months <br />)
Opened:	David Noyes 17:47 Feb 20, 2011
NRC Officer:	Dong Park
Last Updated:	Feb 20, 2011
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v • d • e

v t e Emergency Notification System
Pilgrim with 10 CFR 50.72(b)(3)(iv)(A), System Actuation
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