05000263/LER-2010-003, Regarding Secondary Containment Briefly Degraded
| ML102780320 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 10/04/2010 |
| From: | O'Connor T Xcel Energy, Northern States Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-MT-10-064 LER 10-003-00 | |
| Download: ML102780320 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2632010003R00 - NRC Website | |
text
/e Xcel EnergyB October 4,201 0 Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 L-MT-10-064 10 CFR 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed License No. DPR-22 LER 201 0-003, "Secondan/ Containment Briefly Degraded" The Licensee Event Report (LER) for this occurrence is attached.
Summarv of Commitments new commitments and no revisions to existing commitments.
Site $&e President, Monticello Nuclear Generating Plant Northern States Power - Minnesota Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC
comments regard~ng burden est~mate to the Records Management Branch (T-6 E6), U S. Nuclear LICENSEE EVENT REPORT (LER)
Regulatory Commission, Washington, DC 20555-0001, or by internet e-mall to bjsl@nrc gov, and to the Desk Officer, Office of informat~on and Regulatory Affairs, NEOB-10202 (3150-0104), Office of Management and Budget, Washington, DC 20503 If a means used to impose informat~on collection does not display a currently val~d OMB control number, the NRC may not conduct or sponsor, and a On August 5, 2010, at approximately 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br />, with the plant operating in Mode 1 at 100%
power, DOOR-72 and DOOR-82 for airlock 41 3 (985 foot Pump Room) were inadvertently opened simultaneously, breaching the Secondary Containment (SCT) boundary. Personnel immediately identified the situation and closed both doors within about five seconds (estimated). Shift supervision was notified. With both doors open, the station's Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.3 (verify one Secondary Containment access door in each access opening is closed) was not met. TS Limiting Condition for Operation (LCO) 3.6.4.1 was declared not met and Action A, (Restore secondary containment to Operable status) entered. The doors were verified closed. With SCT restored, TS 3.6.4.1 was met at 1219. The cause of the event was the design of the interlock between the doors in the 985 foot Pump Room which allows simultaneous entry under specific timing conditions (i.e., the doors are opened at exactly the same time - otherwise, the interlock prevents one door from opening if the other is open) and for this occurrence the site failed to take adequate corrective actions for an earlier failure. Corrective actions taken: the doors were closed and administrative controls were placed on the 985 foot Pump Room doors and also the 985 foot Plenum Room doors (which have the same design interlock). NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
PAGE (3) 2of4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
Event Description
On August 5, 201 0, at approximately 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br />, with the plant operating in Mode 1 at 100%
power, DOOR-72 and DOOR-82 for airlock [AL] 41 3 (985 foot Pump Room) were inadvertently opened simultaneously, breaching the Secondary Containment (SCT) [VF] boundary.
Personnel immediately identified the situation and closed both doors [DR] within approximately five seconds (estimated). Shift supervision was notified. With both doors open, the station's Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.3 (verify one Secondary Containment access door in each access opening is closed) was not met. The TS Limiting Condition for Operation (LCO) 3.6.4.1 was declared not met and Action A, (Restore secondary containment to Operable status) entered. The doors were verified closed. With SCT restored, TS 3.6.4.1 was met at 1219.
This event was not the result of a cognitive error. The Fix-It-Now Mechanical team was performing work in the 985 foot Pump Room (outside Secondary Containment) to investigate P-32, Waste Collector Pump, suction pressure. The low dose waiting area is within Secondary Containment, so personnel exited the pump room during work breakststopping points. At 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br />, maintenance and radiation protection personnel attempted to enter the airlock simultaneously from the pump room and from within Secondary Containment. The doors were immediately (within approximately five seconds) closed and Operations shift supervision notified. Neither door has a window, so neither employee could see the other employee operating the opposite door. Both door electromagnets are normally de-energized on this airlock; and when a door opens, the opposite door electromagnet energizes to prevent the door from opening. When both doors opened simultaneously, each door moved away from the electromagnet before it could energize.
Event Analysis
The event is reportable to the NRC under 10 CFR 50.73(a)(2)(v)(C and D) - Event or Condition that could have Prevented Fulfillment of a Safety Function. The station reported the event to the NRC under 10 CFR 50.72 (b)(3)(v)(C and D) on August 5, 2010.
This event is considered a Safety System Functional Failure because for approximately five seconds the SCT TS LC0 was not met. However, evaluation has shown that the system could meet its design function to minimize a ground level release of radiation if there had been a release of activity within SCT.
A similar event on June 3, 2010, had inadequate interim corrective actions. The site has now implemented administrative controls to obtain permission from the Work Execution Center prior to entering the airlock doors that have this vulnerability.
FACILITY NAME (1)
Monticello Nuclear Generating Plant DOCKET (2) 05000263 LER NUMBER (6)
YEAR 2010 - 003 00 SEQUENTIAL NUMBER REVISION NUMBER (9-2007)
U.S. NUCLEAR REGULATORY COMMlSSlOh LICENSEE EVENT REPORT (LER)
I Safetv Sianificance There were no nuclear, radiological or industrial safety significant consequences related to this event.
PAGE (3) 3 o f 4 FAClLlN NAME (1)
Monticello Nuclear Generating Plant The Monticello risk assessment group reviewed the event for risk impact. Defeating the airlock feature for Secondary Containment has no direct or indirect impact on the frequency of core damage (CDF). No systems supporting critical safety functions, including support systems, are impacted due to the loss of secondary containment, and initiating event frequencies are not impacted. Large Early Release Frequency is not significantly impacted since CDF is not affected, and the duration of the secondary containment breach is very small.
Based on the above, the safety significance is minor. An engineering evaluation determined that SCT would be able to perform its safety function with these doors open.
TEXT (If more space is required, use additional copies of NRC Form 366A) (1 7)
The cause of the event was the design of the interlock between the doors in the 985 foot Pump Room allows simultaneous entry under specific timing conditions (i.e., the doors are opened at exactly the same time - otherwise, the interlock prevents one door from opening if the other is open). Additionally, the site did not take adequate interim corrective actions for the same event that occurred on June 3,2010.
DOCKET (2) 05000263 I Corrective Action The following actions were taken or are planned and will be tracked in the Monticello Corrective action program:
LER NUMBER (6)
The doors were closed (within approximately 5 seconds).
The station initiated administrative controls on all airlocks with the same design. Work Execution Center permission is required to open these airlock doors.
The station will evaluate other means of maintaining air lock integrity.
I Failed Component Identification REVISION NUMBER YEAR None 2010 - 003 -
00 SEQUENTIAL NUMBER (9-2007)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
FACILITY NAME (1)
DOCKET (2)
LER NUMBER (6)
PAGE (3)
SEQUENTIAL REVISION Monticello Nuclear Generating Plant 05000263 YEAR NUMBER NUMBER 4 o f 4 2010 - 003 -
00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
Previous Similar Events
On June 3, 2010, the same issue occurred (LER 2010-02).
In February 2007, the same issue occurred (no LER was submitted).
Actions to prevent recurrence were not taken following these events because the site assessed that the likelihood of occurrence was so low that corrective actions were not warranted.
IRC FORM 366A (9-2007)