05000220/LER-2015-001

LER-2015-001, Secondary Containment Inoperable Due to Simultaneous Opening of Airlock Doors

Nine Mile Point Unit 1
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
2202015001R00 - NRC Website

Reported lessons learned are incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by Internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means 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.

A. PRE-EVENT PLANT CONDITIONS:

Prior to the event, Nine Mile Point Nuclear Station Unit 1 (NMP1) was operating at rated thermal power.

B. EVENT:

On Wednesday February 11th, 2015 at approximately 1935 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.362675e-4 months <br />, both Unit 1 Reactor Building Airlock Doors on the 340 foot elevation (Door-056 and Door-057) were opened simultaneously, resulting in a momentary loss of Secondary Containment Operability. Upon identification the doors were immediately closed and operability was restored. NMP1 was operating at rated thermal power. The incident occurred as personnel traversed through the airlock. From review of the Badge Access Transaction Report in addition to personnel statements from the prompt investigation, the following scenario had occurred resulting in the event:

At 1935 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.362675e-4 months <br />, a Member of the Security Organization (MSO) was exiting the Refuel Floor via D-057, while at the same time a Radiation Protection (RP) Technician was entering through D- 056. These actions resulted in the simultaneous opening of both secondary containment doors.

This concurrent opening of both airlock doors resulted in a breach of the secondary containment. One of the doors was immediately closed within 5 seconds re-establishing secondary containment integrity.

Operations review determined that the simultaneous opening of both secondary containment airlock doors constituted a momentary loss of secondary containment per Technical Specification 3.4.3 and NUREG 1022, Revision 3.

Review of the Reactor Building differential pressure as recorded by the plant process computer for the time period of the event indicated that the actual differential pressure remained negative and was unaffected by the brief simultaneous opening of the airlock doors.

This event has been documented in the plant's corrective action program as IR 2451218.

TO THE EVENT:

No other systems, structures, or components contributed to this event.

Nine Mile Point Unit 1 05000220

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

The dates, times and major occurrences for this event are as follows:

February 11, 2015 1935 Worker inside the airlock was exiting secondary containment through D-056 (outer door) Secondary containment was breached when D-057 (inner door) was opened simultaneously.

One of the doors was immediately closed Entered TS action statement 3.4.3, Condition C and exited.

E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

No other systems or secondary functions were affected beyond the systems discussed in Section I.B.

F. METHOD OF DISCOVERY:

This event was discovered by station personnel reporting the issue.

G. MAJOR OPERATOR ACTION:

NMP1 entered TS action statement 3.4.3, and exited it when the inner door was shut.

H. SAFETY SYSTEM RESPONSES:

The duration of this event was approximately 5 seconds. Review of the Reactor Building differential pressure as recorded by the plant process computer for the time period of the event indicated that the actual differential pressure remained negative and was unaffected by the brief simultaneous opening of the airlock doors. Operators entered the applicable TS action statement then exited it soon afterwards. The event concluded when one of the airlock doors was shut.

II. CAUSE OF EVENT:

The MSO involved failed to adhere to established site protocol and administrative requirements governing the use and operation of airlock doors. While attempting to exit the Refuel Floor the MSO approached the inside door (D-057) and validated that he had received a green indicating light. However, contrary to site expectations and administrative postings on the door, the MSO neglected to observe the cameras for inside and outside the airlock, listen for audible door alarms, and pause for an additional five seconds before proceeding. Had the MSO utilized the redundant barriers afforded him, in addition to human performance verification tools, he likely would have observed the RP Technician who had just entered the airlock and the event would not have occurred.

III. ANALYSIS OF THE EVENT:

Simultaneous opening of both reactor building airlock doors is reportable under 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.73(a)(2)(v)(C). It is defined under paragraph 10 CFR 50.73(a)(2)(v)(C) as 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. Secondary Containment differential pressure was unaffected by this event.

One of the accesses to the NMP1 Reactor Building refuel floor is through the airlock doors D-056 and D-057. In response to the event, the station entered the action statement for TS 3.4.3 then promptly exited it when the airlock doors were shut. Computer data identified that secondary containment differential pressure was unaffected by this event. Secondary containment structural integrity, the ability to automatically isolate the non-safety related Reactor Building ventilation system, and the Reactor Building Emergency Ventilation System availability were not impacted. It is concluded that the safety significance of this event is low and the event did not pose a threat to the health and safety of the public or plant personnel. This event does not affect the NRC Regulatory Oversight Process Indicators.

IV. CORRECTIVE ACTIONS:

A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL

STATUS:

The RB 340 foot elevation airlock doors were shut.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

Establish and implement a security training solution relating to secondary containment airlock doors. Training should target both current and perspective members of the security organization. Training should include significance of the doors as they relate to personnel safety, nuclear safety, and regulatory compliance along with site expectations for proper usage.

A. FAILED COMPONENTS:

There were no other failed components that contributed to this event.

B. PREVIOUS LERs ON SIMILAR EVENTS:

NMP1 LER 2014-004, August 13, 2014.

NMP1 LER 2014-005, October 16, 2014.

NMP1 LER 2014-006, October 20, 2014.

(NMP1) Reactor Building was breached when workers opened both inner (D053) and outer (D052) airlock doors simultaneously while passing through. The integrity of the airlock was re-established approximately 5 seconds when one of the doors was closed and latched. Secondary Containment differential pressure was unaffected by these events.

The three LERs in 2014 occurred at the main airlock into the RB 261 foot elevation. This is the first LER for simultaneous opening of the airlock doors on the RB 340 foot elevation.

C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION

COMPONENT

IEEE 803 FUNCTION IEEE 805 SYSTEM

IDENTIFIER IDENTIFICATION

Reactor Building (BWR) N/A NG Reactor Building Ventilation System PDIC VA Airlock Door DR NG

D. SPECIAL COMMENTS:

None