05000461/LER-2014-001, Regarding Premature Failure of Air Supply Solenoid Results in Isolation of Fuel Building Ventilation System and Loss of Secondary Containment Differential Pressure
| ML14091A242 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 03/20/2014 |
| From: | Taber B Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| U-604163 LER 14-001-00 | |
| Download: ML14091A242 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4612014001R00 - NRC Website | |
text
Exelon Generation.
Clinton Power Station 8401 Power Road Clinton, IL 61727 U-604163 10 CFR 50.73 March 20, 2014 SRRS 5A.108 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461
Subject:
Licensee Event Report 2014-001-00 Enclosed is Licensee Event Report (LER) No. 2014-001-00: Premature Failure Of Air Supply Solenoid Results In Isolation Of Fuel Building Ventilation System And Loss Of Secondary Containment Differential Pressure. This report is being submitted in accordance with the requirements of 10 CFR 50.73.
There are no regulatory commitments contained in this report.
Should you have any questions concerning this report, please contact Mr. Jeffrey E. Cunningham, Acting Regulatory Assurance Manager, at (217)-937-3160.
Respectfully, B. Keith Taber Site Vice President Clinton Power Station RSF/blf
Enclosure:
Licensee Event Report 2014-001-00 cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Clinton Power Station Office of Nuclear Facility Safety - IEMA Division of Nuclear Safety
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (02-2014)
Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
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 LICENSEE EVENT REPOR (LER) internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number of Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC for each block) 20503. If a means used to impose an information collection does not display a currently valid OMB digits/characters control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Clinton Power Station, Unit 1 05000461 1 OF 4
- 4. TITLE Premature Failure Of Air Supply Solenoid Results In Isolation Of Fuel Building Ventilation System And Loss Of Secondary Containment Differential Pressure
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SFACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR NUMBER NO.
05000 FACILITY NAME DOCKET NUMBER 01 22 2014 2014 -
001 00 03 20 2014 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
L 20.2201(b)
L 20.2203(a)(3)(i) 50.73(a)(2)(i)(C)
L 50.73(a)(2)(vii)
[
20.2201(d)
[
20.2203(a)(3)(ii)
L 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
L 20.2203(a)(1)
L 20.2203(a)(4)
L 50.73(a)(2)(ii)(B)
E 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i)
[I 50.36(c)(1)(i)(A)
[1 50.73(a)(2)(iii)
Fl 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL
[
20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
[D 50.73(a)(2)(x)
L 20.2203(a)(2)(iii)
[I 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4) 09 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
E 50.73(a)(2)(v)(B)
E] 73.71 (a)(5) 097 L
20.2203(a)(2)(v)
E 50.73(a)(2)(i)(A)
[
50.73(a)(2)(v)(C)
E OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
[] 50.73(a)(2)(v)(D)
Specify in Abstract below or in
PLANT AND SYSTEM IDENTIFICATION
General Electric -- Boiling Water Reactor, 3473 Megawatts Thermal Rated Core Power Energy Industry Identification System (EIIS) codes are identified in text as [XX].
EVENT IDENTIFICATION Premature Failure Of Air Supply Solenoid Results In Isola tion Of Fuel Building Ventilation System And Loss Of Secondary Containment Differential Pressure
A. Plant Operating Conditions Before the Event
Unit: 1 Event Date: 1/22/14 Event Time: 19:56 CST Mode: 1 Mode Name: Power Operation Reactor Power: 97 percent
B. DESCRIPTION OF EVENT
On 1/22/14, the plant was in Mode 1 at 97 percent reactor power and operators in the Main Control Room (MCR) were in the process of placing Train B of the Main Control Room Ventilation (VC) system (VII into service. At 1956 hours0.0226 days <br />0.543 hours <br />0.00323 weeks <br />7.44258e-4 months <br />, while starting the VC system Train B supply fan [FAN] OVC03CB, operators received unexpected alarms [ALM] for trouble in the Fuel Building Ventilation (VF) system [VG] and high Fuel Building differential pressure (d/p).
Operators discovered the causes of the alarms were the trip of the in-service VF system supply fan 1 VF03CA and the Fuel Building [ND] and Secondary Containment differential pressures no longer being maintained negative, as required. Fuel Building d/p was plus 0.5 inches water column (inWC) and Secondary Containment d/p had risen to 0.0 inWC. Secondary Containment d/p is required to be less than or equal to a minus 0.25 inWC in accordance with Technical Specification Surveillance Requirement 3.6.4.1.1.
In response to the loss of secondary containment d/p, operators entered Emergency Operating Procedure (EOP) - 8, Secondary Containment Control. After several seconds the VF system exhaust fan (1 VF04CA) tripped and VF system exhaust fan 1 VF04CB automatically started and ran for several seconds before also tripping. Operators declared Secondary Containment inoperable due to secondary containment differential pressure being greater than minus 0.25 inWC, and entered Technical Specification (TS) 3.6.4.1, Action A.1 that requires secondary containment to be restored to an operable status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
At 1958 hours0.0227 days <br />0.544 hours <br />0.00324 weeks <br />7.45019e-4 months <br />, operators in the MCR noticed VF system inboard exhaust isolation damper [DMP] 1VF07Y change position from intermediate to open. Based on a review of computer point information, operators determined that at about 1956 hours0.0226 days <br />0.543 hours <br />0.00323 weeks <br />7.44258e-4 months <br /> isolation damper 1 VF07Y had travelled to the closed position. With the isolation damper closed (no flow path) the VF supply fan tripped as designed on either low flow or high Fuel Building d/p (greater than 0.0 inWC). The VF system exhaust fan is also designed to trip on low flow.
Therefore, the fan trips and subsequent loss of Secondary Containment negative d/p were expected system responses when the VF system inboard exhaust isolation damper 1VF07Y closed.
At 2003 hours0.0232 days <br />0.556 hours <br />0.00331 weeks <br />7.621415e-4 months <br /> Fuel Building ventilation was restored, the inboard exhaust isolation damper was re-opened, the VF system was restarted, and Secondary Containment d/p was restored to normal. With the Fuel Building d/p and Secondary Containment d/p restored to normal values, operators exited the TS required action. At 2013 hours0.0233 days <br />0.559 hours <br />0.00333 weeks <br />7.659465e-4 months <br />, operators exited EOP-8.
Troubleshooting of this event identified that VF system inboard exhaust isolation damper 1VF07Y unexpectedly closed at almost exactly the same time as the start of VC system Train B supply fan OVC03CB. Circuit analysis
identified that the power source for VF system damper 1 VF07Y also provides power to the VC system supply air B zone isolation dampers and return air B dampers. This review confirmed that the VF system inboard exhaust isolation damper 1VF07Y closed during the cycling of the VC dampers during the start of the VC system B train. The trouble shooting team concluded that during the VC Train B startup, the air supply solenoid [SOL] on the VF system inboard exhaust isolation damper 1 VF07Y responded to a minor perturbation of the supply voltage or a surge of current on the bus by repositioning (dropping out) because the solenoid was weak or degraded, resulting in isolation of the VF system inboard exhaust isolation damper. The VF system inboard exhaust isolation damper failed closed, thus fulfilling its safety function.
This event is reportable under the provisions of 10 CFR 50.73(a)(2)(v)(C) as an event that could have prevented fulfillment of the Secondary Containment safety function needed to control the release of radioactive material. Event Notification 49758 was made to the NRC on 01/22/2014 at 2236 hours0.0259 days <br />0.621 hours <br />0.0037 weeks <br />8.50798e-4 months <br /> Central Standard Time.
This event was entered into the Clinton Power Station corrective action program under Issue Report 1611216.
C. CAUSE OF EVENT
The apparent cause of this event is the VF system inboard exhaust isolation damper 1 VF07Y air supply solenoid was prematurely degraded and caused the damper to isolate the VF system flow-path during the VC Train B startup, resulting in a VF system trip. This solenoid is currently replaced on an 8-year Preventive Maintenance frequency and was most recently replaced on 11/25/13. The cause of the premature failure of the solenoid is being evaluated by an independent laboratory.
D. SAFETY CONSEQUENCES
This event had no actual consequences. Operators entered EOP-8 for Secondary Containment d/p greater than minus 0.25 inWC and entered TS 3.6.4.1, Action A.1 to restore secondary containment to an operable status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Secondary Containment d/p was greater than minus 0.25 inWC for about 7 minutes. The VF system is the non-safety ventilation system which is normally in service to maintain secondary containment d/p, The Standby Gas Treatment system (VG) [BH] is the safety-related system which is credited to perform this function in an accident condition. The VG system was fully operable at the time of the event and capable of performing the required safety function. The VG system was subsequently placed in service and demonstrated the ability to perform the safety function. Therefore, the ability of the Station to maintain secondary containment in an accident scenario was never jeopardized or challenged by the VF system exhaust isolation damper repositioning. An Engineering evaluation has concluded that the safety function of the VF system exhaust isolation damper is to close during the accident condition to ensure the Secondary Containment safety function can be met. Since the VF system exhaust isolation damper failed closed during this event, the damper safety function was met, and therefore this event is not being counted as a Safety System Functional Failure for the NRC performance indicator.
E.
CORRECTIVE ACTIONS
The prematurely degraded solenoid has been replaced.
F.
PREVIOUS OCCURRENCES
A review for previous occurrences did not identify a similar event at Clinton Power Station. The station reviewed Licensee Event Report 1987-009 that reported a manual actuation of the VG system that occurred due to a trip of the VF system exhaust fan resulting in Secondary Containment d/p greater than minus 0.25 inWC. The cause of the event was a random failure of the solenoid valve on the VF system supply outboard
isolation damper. Engineering concluded that the solenoid valve failure mechanism described in LER 1987-009 was different from the event described in this report (LER 2014-001).
G. COMPONENT FAILURE DATA
Component Description: Solenoid Valve; Type: 3 way; Size 3/8 inch; Material: Brass; Orfice: 9/32 inch Manufacturer: ASCO-Automatic Switch Co Model: NP8321A6E