05000263/LER-2017-001

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LER-2017-001, Reactor Scram and Group II Isolation Due to 11 Reactor Feed Pump (RFP) Removal from Service with 12 RFP Isolated
Monticello Nuclear Generating Plant
Event date: 04-15-2017
Report date: 06-13-2017
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(B), System Actuation

10 CFR 50.73(a)(2)(iv)(A), System Actuation
2632017001R00 - NRC Website
LER 17-001-00 for Monticello Regarding Reactor Scram and Group II Isolation Due to 11 Reactor Feed Pump (RFP) Removal from Service with 12 RFP Isolated
ML17164A171
Person / Time
Site: Monticello Xcel Energy icon.png
Issue date: 06/13/2017
From: Gardner P A
Northern States Power Company, Minnesota, Xcel Energy
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-17-049
Download: ML17164A171 (4)


comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Monticello Nuclear Generating Plant 05000-263

EVENT DESCRIPTION

On April 10, 2017, at approximately

1140 hours
0.0132 days
0.317 hours
0.00188 weeks
4.3377e-4 months

, prior to the 2017 Refueling Outage (RFO), the 12 Reactor Feedwater Pump (RFP) [EIIS: P] was removed from service and isolated for maintenance. On April 15, 2017, at

0142 hours
0.00164 days
0.0394 hours
2.347884e-4 weeks
5.4031e-5 months

, a manual reactor scram was inserted to shutdown the plant for the 2017 RFO. On April 15, 2017 at

0436 hours
0.00505 days
0.121 hours
7.208995e-4 weeks
1.65898e-4 months

, with the unit in Mode 3, the 11 RFP in the Feedwater System [SJ] was removed from service in accordance with plant shutdown procedures and the 11 RFP discharge valve (FW-68-1) [ISV] was closed. With the 11 RFP discharge valve closed and the 12 RFP previously isolated, there was no make-up flow path lined-up for the Condensate pumps to supply water to the reactor vessel [RPV]. Reactor water level lowered, and at approximately

0441 hours
0.0051 days
0.123 hours
7.291667e-4 weeks
1.678005e-4 months

, resulted in a valid Reactor Protection System (RPS) [JD] actuation (scram) signal and a valid Primary Containment Group II Isolation [JM] signal when level decreased below +9 inches as indicated on the Safeguards level instrumentation. The 11 RFP discharge valve was reopened to reestablish a flowpath from the Condensate pumps restoring reactor water level. The RPS and Group II isolation logic was reset at 0452 and

0500 hours
0.00579 days
0.139 hours
8.267196e-4 weeks
1.9025e-4 months

, respectively, as stated in the station log. An eight hour event notification was made pursuant to 10 CFR 50.72(b)(3)(iv)(A). All systems functioned as required.

EVENT ANALYSIS

This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A), “Any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph 10 CFR 50.73(a)(2)(iv)(B).” Specifically, the RPS and the Primary Containment Isolation System (PCIS) actuations. This event is not classified as a safety system functional failure.

CAUSE

Two apparent causes were identified:

1. Operators failed to identify and address the unusual Condensate and Feedwater System configuration prior to execution of the 11 RFP shutdown.

2. The guidance for shutdown of the RFP in the Condensate and Reactor Feedwater System operation procedure did not take into account the state of the other train when shutting down a RFP.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Monticello Nuclear Generating Plant 05000-263

SAFETY SIGNIFICANCE

The safety objective of both the RPS and PCIS are to provide timely protection at the onset of conditions that could challenge the integrity of the fuel barrier and nuclear system process barriers. The RPS prevents the release of radioactive material from the fuel and nuclear system process barriers by terminating excessive temperature and pressure increases through the initiation of an automatic plant shutdown. The reactor was subcritical with all rods inserted at the time of the actuation. PCIS prevents release of radioactive materials by isolating the reactor vessel and closing containment where required. The RPS, PCIS, and plant safety systems functioned as designed and fuel and nuclear system process barriers remained intact.

Consequently, this event did not have an adverse impact on the health and safety of the public.

CORRECTIVE ACTIONS

The immediate corrective actions were:

1. An Operations Memo was issued to reinforce operator fundamentals and performance expectations, and Operations management personnel were assigned to monitor the Control Room during major plant maneuvers throughout the remainder of the outage.

The long-term corrective actions are:

1. Revise the plant startup and shutdown procedures to ensure abnormal equipment lineups are addressed such that unexpected procedural interactions are avoided.

2. Revise the Condensate and Reactor Feedwater System operation procedure to maintain a flow path when the opposite train Reactor Feed Pump is isolated.

PREVIOUS SIMILAR EVENTS

There were no previous similar licensee event reports in the past three years.

ADDITIONAL INFORMATION

The Institute of Electrical and Electronics Engineer codes for equipment are denoted by [XX].