05000410/LER-2014-003, Regarding Uninterruptible Power Supply Failure and Subsequent Manual Scram
| ML14135A187 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 05/02/2014 |
| From: | John Stanley Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 14-003-00 | |
| Download: ML14135A187 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 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 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 4102014003R00 - NRC Website | |
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AOExe!on Generation.
Jim Stanley Plant Manager - Nine Mile Point P.O. Box 63 Lycoming, NY 13093 315 349 5205 Office www.exeloncorp.com James.stanley@exeloncorp.com May 2, 2014 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION: Document Control Desk
SUBJECT:
Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 Docket No. 50-410 Licensee Event Report 2014-003, Uninterruptible Power Supply Failure and Subsequent Manual Scram In accordance with 10 CFR 50.73(a)(2)(iv)(A), please find attached Licensee Event Report 2014-003, Uninterruptible Power Supply Failure and Subsequent Manual Scram.
There are no regulatory commitments in this submittal.
Should you have questions regarding the information in this submittal, please contact Everett (Chip) Perkins, Director Licensing, at (315) 349-5219.
Sincerely, JJS/KP
Attachment:
Licensee Event Report 2014-003, Uninterruptible Power Supply Failure and Subsequent Manual Scram cc:
NRC Project Manager NRC Resident Inspector NRC Regional Administrator
r ATTACHMENT LICENSEE EVENT REPORT 2014-003 UNINTERRUPTIBLE POWER SUPPLY FAILURE AND SUBSEQUENT MANUAL SCRAM Nine Mile Point Nuclear Station, LLC May 2, 2014
NRC-FbRM 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
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~Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by LICENSEE EVENT REPORT
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internet e-mail to lnfocollects.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 20503. If a means used to impose an information collection does not display a curreny valid OMB digits/characters for each block) control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Nine Mile Point Unit 2 05000410 1 OF 6
- 4. TITLE Uninterruptible Power Supply Failure and Subsequent Manual Scram
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV MONTH DAY YEAR NAM DOCKET NUMBER MON YEAR YEAR NUMBER NO.
NA NA FACILITY NAME DOCKET NUMBER 003 00 5
2 2014 NA NA
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
ED 20.2201(b)
El 20.2203(a)(3)(i)
ED 50.73(a)(2)(i)(C)
[] 50.73(a)(2)(vii)
D1 20.2201(d)
D 20.2203(a)(3)(ii)
[-I 50.73(a)(2)(ii)(A)
[]
50.73(a)(2)(viii)(A) 1 20.2203(a)(1)
L 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
[1 50.73(a)(2)(vifi)(B) 20.2203(a)(2)(i)
D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iii)
[1 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
[1 50.73(a)(2)(x)
LI 20.2203(a)(2)(iii)
[1 50.36(c)(2)
LI 50.73(a)(2)(v)(A)
[] 73.71(a)(4)
[]
20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[] 50.73(a)(2)(v)(B)
D 73.71(a)(5) 10 20.2203(a)(2)(v)
ED 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(C)
D OTHER 20.2203(a)(2)(vi)
[
50.73(a)(2)(i)(B)
E 50.73(a)(2)(v)(D)
Specify in Abstract below or in i
D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES
March 4 01:40 Entered N2-SOP-97 due to loss of 2VBB-UPS3B 01:41 Entered N2-SOP-29.1 due to loss of cooling to both RRPs 01:43 Exceeded N2-SOP-29.1 danger limit for RCS pump seal cavity temperatures (limit 200'F). RRP A No. 1 seal cavity temp 215'F. RRP B No. 1 seal cavity temp 21 1°F 01:43 Manually scrammed the reactor 05:08 Completed shutting down 2VBB-UPS3B and placed on maintenance bypass per N2-OP-71D
E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
No other systems or secondary functions were affected.
F. METHOD OF DISCOVERY
The event was recognized when operators entered N2-SOP-97 due to the loss of 2VBB-UPS3B.
G. MAJOR OPERATOR ACTION:
Operations personnel made entries into N2-SOP-97 due to the loss of the UPS. Personnel also entered N2-SOP-29.1 due to loss of cooling to the RRPs. The reactor was manually scrammed per N2-SOP-101C, Reactor Scram. Operations completed shutting down 2VBB-UPS3B and it was placed on maintenance bypass per N2-OP-7 1 D.
H. SAFETY SYSTEM RESPONSES:
Safety related equipment downstream of the non-safety related UPS functioned as designed on the loss of the AC power supply resulting in a manual scram without complications.
The 2VBB-UPS3B is designed to auto transfer from its normal AC and DC feeds to the maintenance AC supply in sufficient time to preclude loss of voltage to 2VBS*PNLB 100. The 2VBB-UPS3B did not transfer to the alternate maintenance supply as expected to prevent tripping of the EPA assemblies.
II. CAUSE OF EVENT
The cause of the event was the loss of the UPS which resulted in rising temperatures to the RRP seals and motors. The rise in temperature for these components resulted in a manual scram of the reactor.
The malfunction of the UPS was due to the degraded material condition of an associated subcomponent which prevented the 2VBB-UPS3B from performing its design function.
III. ANALYSIS OF THE EVENT
This event is reportable under the provisions of 10 CFR 50.72(b)(2)(iv)(B), and 10 CFR 50.73(a)(2)(iv)(A). The event caused a valid actuation of a safety system named in 10 CFR 50.73(a)(2)(iv)(B) and the actuation was not part of a preplanned sequence during testing or reactor operation. The loss of the reactor building vent gaseous effluent monitoring system is reportable under 10CFR50.72(b)(3)(xiii) as a condition that resulted in the loss of emergency response assessment capabilities. The UPS malfunction resulted from the degraded condition of a subcomponent. This degradation resulted in a failure of the Static Switch Sense Board (J4 card) to detect fault conditions on the UPS and provide control signals to the Static Switch Drive Logic Board (J5 card), resulting in either a slow or no transfer to the alternate maintenance supply.
Nine Mile Point Unit 2 is equipped with two 10-KVA UPSs (2VBB-UPS3A and 2VBB-UPS3B) that feed RPS logic trip channel loads and main steam line isolation valves (MSIV) control solenoids through their associated distribution panels 2VBS*PNLA100 and 2VBS*PNLB 100, and associated subpanels. These panel boards are fed from non-safety related power supplies because the control circuits supplied from these panel boards return to a fail-safe mode upon loss of electrical power. The RPS and the MSIV are fail-safe systems (de-energize to operate), i.e., failure of the power supply causes a reactor scram and isolation, therefore, the UPS's feeding these systems are classified as non-safety related.
The March 4, 2014 reactor manual scram is bounded by the Updated Safety Analysis Report (USAR) described transient assumed in Chapter 15.1. The reactor was scrammed and water level was maintained by the feedwater/condensate systems and pressure was controlled by electrohydraulic control (EHC). All control rods inserted on the reactor scram signal. The difference from a normal scram was that both reactor recirculation pumps were tripped immediately after the scram signal. The trip of both recirculation pumps is bounded by the transient described in USAR Chapter 15.3. The transient described in the USAR is terminated by the reactor pressure vessel level 8 (L8) trip and subsequent turbine trip resulting in a reactor scram. In the actual transient, operator action was taken prior to any adverse trends in reactor water level. The Mode Switch was placed in shutdown in accordance with N2-SOP-97. These actions are more conservative than those covered in either USAR Chapter 15 sections; therefore, this transient is fully bounded by the event analysis described in these sections.
The event described in this LER affects the NRC Regulatory Oversight Process (ROP) Index for unplanned scrams. Due to the March 4 scram, the unplanned scrams index value will be 1.67 compared to the Green-to-White threshold value of greater than 3.
Based on the above discussion, 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.
IV. CORRECTIVE ACTIONS
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:
For the degraded UPS, the following actions were taken:
Replaced the J4 circuit card Replaced the backplane Calibrated the UPS B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
- 1. For 2VBA*UPS2A/B and 2VBB-UPS3A/B, replace backplane, J4, J5, oscillator board (J3),
static switch drive, and other components as identified.
- 2.
Work with the vendor to identify a comprehensive list of single point of vulnerability (SPV) components that can prohibit the UPS from transferring to its alternate source when needed.
- 3. Revise preventative maintenance strategy to include replacement of all SPV components in 2VBA*UPS2A/B and 2VBB-UPS3A/B.
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
The failed subcomponent that resulted in the UPS not performing its function was the J4 card. The degraded condition of the J4 card was attributed to a failed capacitor.
B. PREVIOUS LERs ON SIMILAR EVENTS:
LER 2003-001 identified that on July 24, 2003, NMP2 experienced a power supply failure resulting in power and flow perturbations that lead to an automatic reactor scram. NMP2 was at approximately 100 percent power when the power supply failed, and was at approximately 45 percent power at the time of the scram. The cause of the power and flow perturbations was the failure of non-safety related power supply C33-K611 (Lambda Model LRS-54-24). The power supply failed because of the age related failure of internal components and no preventive maintenance activity to refurbish or replace the power supply.
LER 2013-004 identified that on December 2, 2013, NMP2 was lowering reactor power level to remove the main turbine from service to support maintenance. During the power reduction, the Low Frequency Motor Generators (LFMGs) did not start automatically. Attempts to manually start the recirculation system pumps in slow speed were unsuccessful and a manual reactor scram was inserted due to the sudden reduction in core flow. The root cause of this event is a failure to identify that the switches in the auto transfer circuits for the reactor recirculation pumps to shift from high speed to low speed are SPV components.
C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO IN THIS LER:
IEEE 803 FUNCTION IDENTIFIER IEEE 805 SYSTEM IDENTIFICATION COMPONENT Uninterruptible Power Supply Electric Reactor Recirculation Pumps D. SPECIAL COMMENTS:
None UJx P
EE AD