05000321/LER-2014-005, Regarding Degraded Diesel Room Fan Flow Switch and Incorrect Thermal Overload Setting Result in Condition Prohibited by Technical Specifications
| ML14241A399 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 08/29/2014 |
| From: | Vineyard D Southern Co, Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-14-1302 LER 14-005-00 | |
| Download: ML14241A399 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2) 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)(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)(1) 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3212014005R00 - NRC Website | |
text
David B. Vlzloyard Vice President
- Hatch August 29, 2014 Soalflem Nuclear Operadag CllfiiPIIIY, Inc.
Plant &Min I. Hatch 11028 Hatch Parltway North Baxley, Georgia 31513 Tal 912.537.5859 Fax 912.386 2077 Docket No.:
50-321 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Licensee Event Report1-2014-005-00 NL-14-1302 Degraded Diesel Room Fan Flow Switch and Incorrect Thermal Overload Setting Result in Condition Prohibited by Technical Specifications Ladles and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)0)(8) Southam Nuclear Operating Company hereby submits the enclosed Licensee Event Report This letter contains no NRC commitments. If you have any questions, please contact Greg Johnson at (912) 537-5874.
Respectfully submitted,
[)~!JOUr~
D. R. VIneyard J
Vice President - Hatch DRV/jcm
U. S. Nuclear Regulatory Commission NL-14-1302 Page2 Enclosures: LER 1*2014-005-00 cc:
Southern Nuclear Ooeratlng Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. Bost, Executive VIce President & Chief Nuclear Officer Mr. D. R. VIneyard, VIce President - Hatch Mr. B. L. lvey, VIce President-Regulatory Affairs Mr. T. E. Tynan, VIce President - Fleet Operations Mr. B. J. Adams, VIce President-Engineering Mr. G. L. Johnson, Regulatory Affairs Manager-Hatch RTVPE: CHA02.004 U. S. Nyclear Begulatol)' Commission Mr. V. M. McCree, Regional Administrator Mr. R. E. Martin, NRR Senior Project Manager-Hatch Mr. D. H. Hardage, Senior Resident Inspector-Hatch
X NRCFORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3160.0104 EXPIRES: 01/3112017 (02*2014) /"k........
Estimated burden per respcli1Se to comply ~
Utis mandalllry collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
\\.~) LICENSEE EVENT REPORT (LER)
Reporlad lessons learned are incorporated info the licensing process and fed back to industry.
Send comments regarding burden estimate ro the FOIA, Privacy and lnfOilllation Collections Branch (J.S F53), U.S. Nuclear R119Uiatory Comnission, Washington, DC 20555.0001, or by internet e-IIW to lnfoco!lects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regllarory Aftairs, NECJ8.10202, (3150-0104), Office ol Management and Budget, Washington, DC 20503. II a means used to impose an information cdlection does n<11 <isplay a cunen!ly valid OMS control romber, the NRC may not conduct or sponsor, and a person is not rllGlJired to respond to, the information collection.
- 3. PAGE Edwin I. Hatch Nuclear Plant Unit 1 05000 321 1 OF 4
- 4. TITLE Degraded Diesel Room Fan Flow Switch and Incorrect Thermal Overload Setting Result in Condition Prohibited by If echnical Specifications
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILmES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUI.UIER 07 03 2014 2014 - 005 -
00 8
29 2014
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.22o1cb>
D 20.2203(a)(3)(i)
D 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) 1 D 20.2201 Cd>
D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A)
D 20.2203<a><1 >
0 20.2203(a)(4)
D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(2)(i)
D 50.36(c)( 1 )(i)(A)
D 50.73(a)(2)(iii)
D 50. 73(a)(2)(ix)(A)
- 10. POWER LEVEL D 20.2203(a)(2)(ii)
D 50.36(c)( 1 )(ii)(A)
D 50.73(a)(2)(iv)(A)
D 50. 73(a)(2)(x)
D 20.2203(a)(2)(iii) 0 50.36(c)(2) 0 50.73(a)(2)(v)(A)
D 73.71(a)(4) 100 D 20.2203(a)(2)(1v) 0 50.46(a)(3)(ii)
D 50. 73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(v)
D 50. 73(a)(2)(i)(A) 0 50. 73(a)(2)(v)(C)
D OTHER D 20.2203(a)(2)(vi)
~ 50.73(a)(2)(1)(B) 0 50. 73(a)(2)(v)(D)
Specify in Abstract below or in
PLANT AND SYSTEM IDENTIFICATION
General Electric-Boiling Water Reactor Es~mated burden per response to comply 1\\'ith this mandatory collee~n 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 info the licensing process and led badt to industry.
Send comments regardng burden estimate to the FOIA, Priva:y and Information CoUec~
Branch (T-5 F53), U.S. Nuclear Regt4atory Commission, Washington, DC 20555.()()()1, CM" by internet e-mail to lnfocoDeeiS.R8SOUIC8@nrc.gov, and to the Desk Officer, Office oflnlonna~n and Regulatory Affairs, NE08-10202, (3150-0104), Olfica of M~nt and Budge~
Washington, DC 20503. If a means used to impose an inlonnalion coklion doas not display a Clllenlly vafid OMS control mmber, the NRC may not conduct or sponsor, and a person is not required to respond to, the information coUdon.
YEAR 2014
- 6. LER NUMBER I
SEQUENTIAL I NUMBER 005 REV NO.
00 2
- 3. PAGE OF 4
Energy Industry Identification System codes appear in the text as (EllS Code XX).
DESCRIPTION OF EVENT
On 07/03/2014 at 0856 EDT, with Unit 1 operating at approximately 100 percent rated thermal power, the 1A emergency diesel generator (EDG) (EllS Code DG) room exhaust fans (EllS Code FAN) were found inoperable while performing the 1A EDG monthly surveillance due to tripped thermal overload relays (EllS Code 94) in the motor control center (MCC) cubicles. The EDG room exhaust fans are two 100% capacity ventilators responsible for exhausting heat from the EDG room during EDG operation. The 'A' fan is the primary exhaust fan and the 'B' fan is the standby exhaust fan for the 1 A EDG room. The 1 A EDG was declared inoperable and the required actions were taken in accordance with the Technical Specifications. New thermal overload heaters were installed June 6, 2014 as part of a corrective action for incorrectly sized thermal overload heaters that were previously installed in April2014. These new thermal overload heaters were found to also be incorrectly sized, leading to thermal overloads with trip settings that were too close to the normal operating current for the fans. The incorrectly sized thermal overload heaters resulted in premature trips of the thermal overloads.
On 07/04/2014, Maintenance replaced the overload heaters in the 1A EDG ventilation fan pan assemblies and proper operation of each of the ventilation fans was then verified in accordance with Operations procedures.
On 07/07/2014, while analyzing data from the 'A' and 'B' exhaust fans, the primary exhaust fan differential pressure flow switch (EllS Code PDS) was found to be malfunctioning, leading to frequent cycling between the primary and alternate 1 A EDG room exhaust fans and increasing operating current. The fan control switches were aligned to make the 'B' fan the primary fan and the 'A' fan the standby fan to temporarily alleviate the problems encountered with the flow switch.
On 07/08/2014, Maintenance replaced and calibrated the 'A' differential pressure flow switch and returned the
'A' exhaust fan as the primary fan and the 'B' was aligned as the standby fan.
Additional safety-related and non-safety-related components whose thermal overloads were resized in early June 2014 as part of the same corrective action were walked down. The affected safety-related components were confirmed to be operating or in a standby configuration and their respective thermal overloads were not tripped. Some non-safety-related components whose respective thermal overloads had been resized were found in a tripped condition. Reasonable assurance was maintained that their support function did not adversely impact the operability of structures, systems, or components required by the Technical Specification in their "as found" condition. Several previously replaced overload elements were determined to still be incorrectly sized for these components, based on the added guidance to use actual measured motor currents.
Corrective actions were also taken to resize the affected components to increase their margin of operation and their reliability. (02*2014)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT {LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE OF YEAR I SEQUENTIAL I REV NUMBER NO.
Edwin I. Hatch Nuclear Plant Unit 1 05000 321 3
2014 005 00
CAUSE OF EVENT
The affected EDG room exhaust fans were found in a tripped condition due to the combination of incorrectly sized thermal overloads, increased demand on the motor due to the cycling of the 'A' flow switch, and operation of the motor with the running amps near their respective trip set points.
4 When the overload heaters were replaced in June 2014, the thermal overload heater size was based on the nameplate rating of the affected component. It was later learned that some motors were drawing current in excess of their nameplate rating. It is common for safety related fan motors to have a full load operating current value higher than their nameplate rating due to the motor housing being larger than normal. Using the nameplate amperage value instead of the full load operating current value led to the operation of the exhaust fans with running amps too close to their respective trip set points.
In conjunction with the undersized thermal overload heaters, the 'A' differential pressure flow switch for the primary 1 A EDG room exhaust fan was malfunctioning and causing the primary and standby 1 A EDG room exhaust fans to continuously cycle on and off. The abnormal cycling of the flow switch subjected the EDG room exhaust fans and its associated thermal overload heater to frequent in-rush currents. The frequent cycles prevented the overload heater from properly cooling, increasing its susceptibility to spurious trips. The failure of the flow switch is due to a lack of preventative maintenance on the component as the flow switch was no longer correctly calibrated. The malfunction of the 'A' flow switch did not impact the functionality of the 'A' exhaust fan once the correctly sized overload heater was installed. However, it did cause the standby 'B' exhaust fan to start due to a false low flow signal.
REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT The event is reportable per 10 CFR 50.73(a)(2)(i)(B) due to the 1A EDG room exhaust fans being in a tripped condition, resulting in the Limiting Condition for Operation (LCO) for the EDG existing for a time longer than permitted by Technical Specifications (TS). It was assessed that the fans had been in a tripped condition following the installation of incorrectly sized thermal overload heaters.
The event was discovered during routine surveillance testing of the 1 A EDG with its associated emergency bus being supplied power from off-site sources through the unit's auxiliary transformers. As a result this condition did not result in any plant transient or loss of safety function for the components served by this emergency bus.
The design of the plant's electrical power systems and compliance with the unit's Technical Specifications provide assurance of independent and redundant sources of power to support required safety systems during all anticipated operational occurrences and accident conditions. The needed electrical power to safely shut down the Unit 1 reactor, maintain it in a shutdown condition, and mitigate the consequences of a postulated accident remained operable since the 16 and 1C EDGs remained operable. Based on this information, this event had very low safety significance.
CORRECTIVE ACTIONS
The thermal overload heaters for the pan assemblies associated with the 1 A EDG ventilation fans were replaced and the fans were returned to service. The thermal overload sizing for a 3 pole block using 2 heaters to provide adequate thermal overload protection of Class 1 E systems was also verified for all components whose pan assembly was replaced in June 2014. A new pressure differential switch for the 'A' exhaust fan was also installed and calibrated.
The maintenance procedure used to provide instruction for sizing the thermal overload heaters was revised to require the use of the running amps for the affected load as input in determining the correct size thermal {02*2014}
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LEA NUMBER 3.PAGE 4
OF YEAR I SEQUENTIAL I REV NUMBER NO.
Edwin I. Hatch Nuclear Plant Unit 1 05000 321 4
2014 005 00 overload hater for that load. Surveillance procedures will also be revised such that, prior to a diesel generator test or run, a visual verification will be performed verifying each fan will run.
ADDITIONAL INFORMATION
Other Systems Affected: No systems other than those mentioned in this report were affected by this report.
Failed Components Information
Master Parts List Number: 1 R24S025 (1 X41-C002AIB)
Manufacturer: Cutler Hammer Model Number: AA23AB Type: Thermal Type A Overload Relay Master Parts List Number: 1 X41-N045A Manufacturer: Dwyer Instruments Model Number: 1637-25 Type: Differential Pressure Switch Manufacturer Code: C770 EllS System Code: ED Reportable to EPIX: Y Root Cause Code: 94 Manufacturer Code: 0282 EllS System Code: ED Reportable to EPIX: Y Root Cause Code: PDS Commitment Information: This report does not create any new licensing commitments.
Previous Similar Events
LEA 2-2014-001, identified incorrectly sized thermal overloads that led to a condition prohibited by Tech Specs. The 1A and the 2A EDG were inoperable for a period of time greater than the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> RAS due to the tripped condition of the 1 A and 2A EDG Room Exhaust Fans. The thermal overloads for the pan assemblies feeding the fans had tripped due to incorrectly sized thermal overload heaters. New thermal overloads had previously been installed in conjunction with a modification that installed new pan assemblies. The new thermal overload heaters were found to be incorrectly sized, leading to thermal overloads with trip settings close to the normal operating current of the fans. These overly conservative trip settings led to the premature tips of the thermal overloads. The trip of the 'A' and 'B' fans was not prevented by the previous corrective actions due to the fact that the cause determination and resulting corrective actions from that event had not had been identified and fully implemented.