Control Rod Drop Accident Safety System Event at Monticello

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Power Reactor Event Number: 47479
Facility: MONTICELLO
Region: 3 State: MN
Unit: [1] [ ] [ ]
RX Type: [1] GE-3
NRC Notified By: KIRK DUEA
HQ OPS Officer: HOWIE CROUCH
Notification Date: 11/28/2011
Notification Time: 01:04 [ET]
Event Date: 11/27/2011
Event Time: 16:57 [CST]
Last Update Date: 11/28/2011
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(v)(D) – ACCIDENT MITIGATION
Person (Organization):
JULIO LARA (R3DO)
Unit SCRAM Code RX CRIT Initial PWR Initial RX Mode Current PWR Current RX Mode
1 N N 0 Startup 0 Startup

Event Text

ROD WORTH MINIMIZER CONTROL SWITCH FOUND OUT OF REQUIRED POSITION

“After transitioning to Mode 2 from Mode 4, while performing the Rod Worth Minimizer (RWM) operability test, it was discovered that the RWM control switch was in the BYPASS position. The RWM enforces predetermined control rod withdrawal and insertion sequences. Complying with these predetermined sequences ensures a Control Rod Drop Accident does not exceed analytical limits. With the control switch in the BYPASS position, the RWM was inoperable and would not have enforced the predetermined control rod withdrawal sequence. The RWM control switch was restored to the OPERATE position and the RWM was verified to be operable.

“This issue is being reported under 50.72(b)(3)(v)(D) as an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of the RWM, which is a system needed to mitigate the consequences of the Control Rod Drop Accident.”

The licensee will be notifying the NRC Resident Inspector.

The Monticello Nuclear Generating Plant is a nuclear power plant located in Monticello, Minnesota, along the Mississippi River. The site, which began operating in 1971, has a single nuclear reactor(boiling water reactor) of the General Electric BWR-3 design generating 613 megawatts, but studies are ongoing to uprate it to 700 MWe.

Currently the plant is both owned and operated by Xcel Energy

Source: NRC Event Notifications

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