05000293/LER-2017-011

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LER-2017-001, Simultaneously Opened Reactor Building Airlock Doors Caused Loss of Secondary Containment
A Ler Number
Event date: 06-20-2017
Report date: 08-15-2017
2932017001R00 - NRC Website
LER 17-011-00 for Pilgrim Nuclear Power Station Regarding Simultaneously Opened Reactor Building Airlock Doors Caused Loss of Secondary Containment
ML17234A318
Person / Time
Site: A Ler Number, Pilgrim Entergy icon.png
Issue date: 08/15/2017
From: Perkins E P
Entergy Nuclear Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
2.17.057
Download: ML17234A318 (6)


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.

Pilgrim Nuclear Power Station 05000-293 2017 - 00

BACKGROUND

The secondary containment is designed to minimize any ground level release of radioactive materials that might result from a serious accident. The reactor building provides secondary containment during reactor operation, when the drywell is sealed and in service. Because the secondary containment is an integral part of the complete containment system, secondary containment is required at all times that primary containment is required as well as during movement of recently irradiated fuel and during operations with the potential to drain the reactor vessel.

EVENT DESCRIPTION

On June 20, 2017, at 1444 [EDT] plant personnel notified the Main Control Room that both doors in the secondary containment airlock at the 23 foot elevation on the East Side Reactor Building (RB) Entrance were opened simultaneously. They noted that when they exited through Door 58 that Door 85 opened momentarily and then closed within seconds but did not latch. The failure of this interlock caused a loss of secondary containment per Technical Specification (TS) 3.7.C.1. The doors were immediately reclosed, and the secondary containment boundary was reestablished. A repeat of the event, which was considered testing of the airlock, was performed a short time later to verify and confirm the condition. Although it was verified that both doors did open, Operators could not get the door to repeat the condition upon arrival.

CAUSE OF THE EVENT

The direct cause of the event was that the Door 85 latch did not engage to keep the door from opening when the other door in the airlock (Door 58) was opened. The closer magnets did engage for the interlock to show that the door was closed and allow entry through the opposite door.

CORRECTIVE ACTIONS

The Door 85 closer was adjusted to add additional tension to ensure it latched without manual action.

SAFETY CONSEQUENCES

The secondary containment performs no active function; however, its leak tightness is required to ensure that the release of radioactive materials from primary containment is restricted to those leakage paths and associated leakage rates assumed in the accident analysis and that fission products entrapped within the secondary containment structure will be treated by the Standby Gas Treatment System (SGTS) prior to discharge to the environment.

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.

Pilgrim Nuclear Power Station 05000-293 2017 - 00 Secondary containment remained available and functional during the event since the secondary containment interlock was immediately restored by closing the doors.

The engineering evaluation that was performed concluded that this event did not constitute a Safety System Functional Failure. (Reference NEI 99-02, Revision 7, Regulatory Assessment Performance Indicator Guideline, Section 2.2, Mitigating Systems Cornerstone, Safety System Functional Failures, Clarifying Notes, Engineering Analyses.) As such, this event will not be reported in the NRC Performance Indicator for Safety System Functional Failures since an engineering evaluation was performed which determined that the system was capable of performing its safety function during this event when both doors of the secondary containment interlock were momentarily opened simultaneously.

There are no consequences to the general safety of the public, nuclear safety, industrial safety or radiological safety from this event.

No actions to reduce the frequency or consequence are necessary.

REPORTABILITY

Given the impact on the secondary containment, this report is submitted in accordance with the requirements of 10 CFR 50.73 (a)(2)(v)(C), any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material.

PREVIOUS EVENTS

A review of LERs for the past five years did not identify any additional submittals of Secondary Containment being declared inoperable due to simultaneous opening of airlock doors.

REFERENCES

CR-PNP-2017-06380 - 011