05000263/LER-2006-001, Unplanned LCO Due to Emergency Filter Flexible Connector Failure

Unplanned LCO Due to Emergency Filter Flexible Connector Failure

ML060940130
Person / Time
Site:	Monticello
Issue date:	03/31/2006
From:	Conway J Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-06-017 LER 06-001-00
Download: ML060940130 (4)

LER-2006-001, Unplanned LCO Due to Emergency Filter Flexible Connector Failure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(B)
2632006001R00 - NRC Website

text

i ts NMC Committed to Nudleer Exce Monticello Nuclear Generatinq Plant Operated by Nuclear Management Company, LLC March 31, 2006 L-MT-06-017 10 CFR Part 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Monticello Nuclear Generating Plant Docket No. 50-263 License No. DPR-22 LER 2006-001. "Unplanned LCO due to Emergency Filter Flexible Connector Failure" A Licensee Event Report for this occurrence is attached.

This letter makes no new commitments or changes any existing commitments.

oh T Cnway

(

Site Vice President, Monticello Nuclear Generating Plant Nuclear Management Company, LLC Enclosure cc:

Administrator, Region l1l, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC

-: J 3-e 01')- I
k 2807 West County Road 75

• Monticello, Minnesota 55362-9637 Telephone: 763-295-5151

• Fax: 763-295-1454

NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 EXPIRES 6-30-2007 (6-2004)

COMMISSION

, the NRC may not conduct or sponsor, and a digits/characters for each block) person is not required to respond to, the Infonmation collection.

FACILITY NAME (1)

DOCKET NUMBER (2)

PAGE (3)

Monticello Nuclear Generating Plant 05000263 1 of 3 TITLE (4) Unplanned LCO due to Emergency Filter Flexible Connector Failure EVENT DATE ()

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

MO DAY YEAR YEAR lSEQUENTIAL REV MO DAY YEAR FACIL NAME 05000 FACILITY NAME DOCKET NUMBER 02 01 2006 2006 001 00 04 03 2006 05000 OPERATING N

THIS REPORT IS SUBMITED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) (11)

MODE (9) 20.2201 (b) 20.2203(a)(3)(ii)

=

50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)

POWER 100 20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LEVEL (10) 20.2203(a)(1) 50.36(c)(1)(i)(A)

=

50.73(a)(2)(iv)(A)

=

73.71 (a)(4) 20.2203(a)(2)(i) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(5) 20.2203(a)(2)(ii) 50.36(c)(2) 50.73(a)(2)(v)(B)

OTHER

- Specify in Abstract b~elow or 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C)

In NRC Form 366A 20.2203(a)(2)(iv) 50.73(a)(2)(i)(A)

X 50.73(a)(2)(v)(D) 20.2203(a)(2)(v) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(C)

=

50.73(a)(2)(viii)(A) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B)

LICENSEE CONTACT FOR THISLER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Ron Baumer 763-295-1357 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE

SYSTEM COMPONENT MANU-REPORTABLE l l CAU SYSTEM COMPONEN lANU-REPORTAOLE FATUE TO EPIX I

EFACTURER TO EPIX X

BH FCON A220 Y

SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR SUBMISSION YES (if yes, complete EXPECTED SUBMISSION DATE).

IX NO I

DATE (15)

ABSTRACT On February 1, 2006 at 2300 with the unit operating at 100% power, the unit "A" train (V-ERF-1 1) of the Emergency Filtration (EFT) system tripped. Investigation found that the rubber boot between the filter unit and the suction of the fan had ripped resulting in a low flow condition through the filter. The low flow condition initiated an automatic trip of the operating unit. Due to the back leakage through the tear in the "A" filter boot and in order to perform an extent of condition review, the "B" train (V-ERF-1 2) of the EFT system was declared inoperable. The station entered a 24-hour LCO for both trains being inoperable at 2300. A manual damper was closed to isolate the potential in-leakage from the "A" train to the "B" train.

An extent of condition review of the HUB" unit boot was completed and the "B" EFT system was declared operable at 0302 on February 2, 2006. The 24-hour LCO was exited at 0302. An eight hour ENS notification was made to the NRC at 0351 on February 2, 2006 in accordance with 10 CFR 50.72(b) (3)

(v) (D). The replacement of the boots on EFT Train 'A" and UB" were completed on February 2, 2006.

The cause of the event was failure by the station to consider the effect of changing operating conditions on the Preventive Maintenance (PM) frequency for V-ERF-1 1 and -12. The station has replaced the rubber boots on both EFT trains and will revise the PM frequency for future replacements of the rubber boots.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)

LICENSEE EVENT REPORT (LER)

FACILITY NAME 1)

DOCKET (2)

LER NUMBER 6)

PAGE (3)

SEQUENTIAL REVISION Monticello Nuclear Generating Plant 05000263

- YEAR NUMBER NUMBER 2 of 3 2006.-

001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Description

On February 1, 2006 at 2300 with the unit operating at 100% power, the unit "A" train (V-ERF-1 1) of the Emergency Filtration (EFT) [BH] system tripped. Investigation found that the rubber boot [FCON]

between the filter unit and the suction of the fan had ripped resulting in a low flow condition through the filter. The low flow condition initiated an automatic trip of the operating unit. Due to the back leakage through the tear in the "A" filter boot and in order to perform an extent of condition review, the UBU train (V-ERF-12) of the EFT system was declared inoperable. The station entered a 24-hour LCO for both trains being inoperable at 2300. A manual damper was closed to isolate the potential in-leakage from the "A" train to the "B" train. An extent of condition review of the "B" unit boot was completed and the WB" EFT system was declared operable at 0302 on February 2, 2006. The 24-hour LCO was exited at 0302. An eight hour ENS notification was made to the NRC at 0351 on February 2, 2006 in accordance with 50.72(b)(3)(v)(D).The replacement of the boots on EFT Train WA-and 'B" were completed on February 2, 2006.

Investigation of the failed boot from Train "A" found cracks and tears due to aging and service related degradation. Inspection of the boot removed from Train "B" found similar cracking to a smaller extent, however no tears were found in the boot.

Event Analysis

In accordance with 10 CFR 50.72 (b)(3)(v)(D), "Event or Condition that could have Prevented Fulfillment of a Safety Function," an eight-hour event notification was made to the USNRC, due to the loss of the emergency filtration capability for accident mitigation. Per 10 CFR 50.73 (a)(2)(v)(D), a Licensee Event report is required for this event.

The event is classified as a safety system functional failure.

Safety Sianificance Following trip of V-ERF-1 1, both trains of EFT were declared inoperable. This was due to the tear on V-ERF-1 1 boot which prevented proper functioning of the unit, and potential backflow through the tear that could have prevented proper operation of V-ERF-1 2. This condition could have prevented the 'A" and "B" EFT/CRV system trains from performing the safety related functions. These functions include maintaining habitability during a toxic chemical release or in the event of high radiation detected in the outside air, and providing a controlled environment (humidity and temperature) for safety related equipment located in the Main Control Room and the EFT Building boundaries during post accident conditions. The "A" CRV was not capable of performing those functions until the boot was replaced.

Following isolation of V-ERF-1 1, an evaluation of the V-ERF-1 2 boot was performed and V-ERF-1 2 was declared operable. Subsequently, the boot on V-ERF-12 was replaced.

The Probabilistic Risk Assessment (PRA) group performed an evaluation for significance. The risk impact incurred by the failure of the rubber boot was of low significance. Scenarios that involve control room habitability-concluded that the risk of requiring control room ventilation to be isolated is negligible,U.S. NUCLEAR REGULATORY COMMISSION (1-2001)

LICENSEE EVENT REPORT (LER)

FACILITY NAME (1)

DOCKET (2)

LER NUMBER (6 PAGE (3)

I SEQUENTIAL REVISION Monticello Nuclear Generating Plant 05000263 YEAR

'NUMBER NUMBER 3 of 3 2006 001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) and degradation of EFT ventilation system reliability (loss of both trains, for example) poses a negligible risk impact.

Cause

The station changed the operating conditions of V-ERF-1 1 and V-ERF-1 2 in 1996 from a standby condition to continuous operation. The cause of this event was failure by the station to consider the effect of changing the operating conditions on the PM frequency on V-ERF-1 1 and V-ERF-12. This change increased the amount of time the rubber boots were under stress from temperature changes and operating stresses.

Corrective Action

The following corrective actions have been taken or will be tracked to completion in the station's corrective action program:

1. The rubber boot on V-ERF-1 1 was replaced.

2. The rubber boot on V-ERF-12 was replaced.

3. The station will revise the replacement frequency for the rubber boots.

Failed Component Identification Manufacturer: American Air Filter Connector, Flexible (9 inch diameter) - Catalog ID - VAGSGC

Previous Similar Events

No previous station events were found.