05000361/LER-2002-001, Aging Phenomenon Affects Certain Potter and Brumfield Relays
| ML020330048 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/29/2002 |
| From: | Krieger R Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 02-001-00 | |
| Download: ML020330048 (8) | |
| 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 |
| 3612002001R00 - NRC Website | |
text
SOUTHERN CALIFORNIA EDISON An EDISON INTERNATIONW1L Company R. W. Krieger Vice President Nuclear Generation January 29, 2002 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555-0001
Subject:
Docket Nos. 50-361 and 50-362 Voluntary Report Licensee Event Report No. 2002-001 San Onofre Nuclear Generating Station, Units 2 and 3 Gentlemen:
This submittal provides a voluntary Licensee Event Report (LER) describing an aging phenomenon that affects certain Potter and Brumfield relays. SCE discovered this phenomenon while investigating a Potter and Brumfield relay that failed during its normal six month surveillance testing. This event did not meet the reporting criteria provided in 10CFR50.72, 50.73 or 10CFR21. Nevertheless, SCE considered that this information could assist other licensees that use similar relays and is providing this voluntary report.
Any actions listed are intended to ensure continued compliance with existing commitments as discussed in applicable licensing documents; this LER contains no new commitments. If you require any additional information, please so advise.
Sincerely, LER No. 2002-001 cc:
E. W. Merschoff, Regional Administrator, NRC Region IV C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 & 3 P. 0. Box 128 San Clemente. CA 92674-0128 949-368-6255 Fax 949-368-6183 1/1) ,7
''X
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES MM-YYYY (M M-YYYY)
, the NRC may not conduct or sponsor, and
- person is not requiedt rspn tthe information collection.
FACILITY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
San Onofre Nuclear Generation Station (SONGS) Unit 2 05000-361 1 of 7 TITLE (4)
Aging Phenomenon Affects Certain Potter and Brumfield Relays EVENiT DATI (5)
LEsR NUMBER (6)
MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR FACILITY NAME DOCKET NUMBER I
NUMBER NUMBER SONGS Unit 3 05000-362
=_
FACILITY NAME DOCKET NUMBER 09 11 2001]
2002 001 00 01 29 2002 OPERATING T1 HIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) (11)
MODE (9)
[
l 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii)
POWER LEVEL [ 100 1 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A)
(10)
[l__ J 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)0l)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71 (a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71 (a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
X OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Voluntary LICENSEE CONTACT FOR THIS LER (12) l NAME TELEPHONE NUMBER (Include Area Code) l R. W. Krieger, Vice President, Nuclear Operations 1949-368 255 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
CAUSE
SYSTEM COMPONENT MANUFACTURER REPORTABLE TO
CAUSE
SYSTEM COMPONENT MANUFACTURER 1 REPORTABLE I
BA RLY P297 l
Y l
l llll SUPPLEMENTAL REPORT EXPECTED (14)
]
EXPECTED MONTH lD l
YEAR YES l X I NO SUBMISSION l
l IfST esRcor
(
lte EXPEcTEDsUBMISSIoNDATEy
.ing DATEo(15) l____e-adt w itte lines ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)
On 9/11101, while performing a subgroup relay test on Emergency Feedwater Actuation Signal (EFAS) 1 Train B, Steam Generator (SG) E-089 Auxiliary Feedwater (AFV)
Isolation Valve 2HV4715 failed to close. AFW pump 2P140 started and AFW control valve 2HV4706 to SG E-089 closed as expected.
2HV4715 did not close as expected and was verified locally to be open. Plant operators manually closed 2HV4715 from the control room. Upon investigation, SCE discovered that the P&B relay (2L035K402) used for 2HV4715 had failed.
SCE determined the return springs of 2L035K402 would not fully rotate the relay shaft to its zero-degrees stop position when de-energized. A self-lubricating nylon hub in deck 1 of the form "Y" contacts (i.e., closest to the relay coils and the heat they generate) had deteriorated such that reinforcing glass fibers in the nylon were creating an abrasive interface.
SCE replaced the relay and returned the EFAS train to operable status within the time allowed by the Tech Specs. SCE also determined that there is no need to utilize the form "Y", high current contacts.
A proactive approach will be implemented to replace the P&B MDR-7032 relays with P&B MDR-7033 or P&B MDR-7034 relays, which do not contain form "Y" contact blocks.
Because the failed relay is not in the EFAS or MSIS actuation logic for 2HV4715, there was no safety significance to this event.U.S. NUCLEAR REGULATORY COMMISSION (MM-YYYY)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACLFTY N
IE(1)
DOCKET (2 LER NUMBER 6 PAGE (3a YEAR SEQUENTIAL REVISION San Onofre Nuclear Generating Station (SONGS) Unit 2 05000-361 NUMBER NUMBER_
2of7 2002
- - 001-00 Plant:
San Onofre Nuclear Generating Station, Units 2 and 3 Event Date:
September 11, 2001 Discovery Date:
January 11, 2002 Unit 2 Unit 3 Reactor Vendor Combustion Engineering Combustion Engineering Mode 1 - power operation 1 - power operation Power (percent)*
98.5 100
- on 9/111/2001
Background:
At San Onofre Nuclear Generating Station (SONGS) Units 2 and 3, the Engineered Safety Features Actuation System (ESFAS) use Potter and Brumfield (P&B) series 7032 Motor Driven Relays (MDR) to actuate Engineered Safety Features equipment. The ESFAS subgroup relays are the last relays in the control circuit before the ESF actuated equipment. As required by Technical Specification 3.3.6.,
"Engineered Safety Features Actuation System (ESFAS) Logic and Manual Actuation," Southern California Edison (SCE) surveils these relays once every six months.
Series 7032 relays are non-latching MDR relays (Figure 1). These relays have two positions: "energized" and "de-energized."
When energized, two coils, connected in series and located inside the relay, rotate the relay rotor shaft and operate the relay contacts by a shaft extension. When de-energized, the rotor shaft is returned to its normal position by two connected springs (Figure 2). Relay shaft rotation is limited to a 30-degree arc by the stator faces and a stop ring. At SONGS, the Series 7032 relays are normally energized so that only spring force is used to rotate the relay on a loss of power.
The Series 7032 relays have three decks of main form "Y" contacts (high current applications) and three decks of four (4) auxiliary form "C" contacts (low current applications) mounted in isolated rings.
Units 2 and 3 each have 20 Series 7032 relays (total of 40) installed as follows:
- 1. 10 are spare relays and not currently being utilized
- 2. 18 form Y contacts are not being used
- 3. 12 form Y contacts are being used Description of the Event:
On September 11, 2001, while performing a subgroup relay test on Emergency Feedwater Actuation Signal (EFAS) 1 Train B, Steam Generator (SG) E-089 Auxiliary Feedwater (AFW) (BA} Isolation Valve 2HV4715 {FCV} failed to close. AFW pump 2P140 started and AFW control valve 2HV4706 to SG E-089 closed as expected. 2HV4715 did not close as expected and was verified locally to be open.
Plant operators manually closed 2HV4715 from the control room. Upon investigation, SCE discovered that the P&B relay (2L035K402) {RLY} used for 2HV4715 had failed. The relay was replaced and the EFAS train returned to operable status within the time allowed by Tech Spec 3.7.5, "Auxiliary Feedwater (AFW) System."U.S. NUCLEAR REGULATORY COMMISSION (MM-YYYY)
LICENSEE EVENT REPORT (LER)_l TEXT CONTINUATION FACILTY NA(1
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EAR SEQUENTIAL REVISION San Onofre Nuclear Generating Station (SONGS) Unit 2 05000-361 i
NUMBER NUMBER 3of7
_?2002 1-001 -
I 00 I
On September 14, 2001, SCE determined the shaft of relay 2L035K402 would not fully counter-rotate to its zero-degrees stop position when de-energized. SCE continued to perform a detailed cause evaluation, which included the use of a Scanning Electron Microscope to examine various components within the relay. During this time, SCE had ongoing discussions with P&B. During November 2001, SCE met with P&B at their facility in Greensboro, North Carolina and analyzed a second sample of the same type and vintage relay. In November 2001, SCE conducted additional laboratory analyses to quantify the degradation of the relay components. P&B confirmed that the springs were within their design specifications on December 28, 2001 and were not a factor in the relay failure. On January 11, 2002 (discovery date), SCE completed the cause evaluation, concluding that the self-lubricating nylon hub in deck 1 of the form "Y" contacts (i.e., closest to the relay coils and the heat they generate) had deteriorated such that reinforcing glass fibers in the nylon were creating an abrasive interface. The increased friction prevented the shaft from rotating to its zero position (Figure 2). Consequently, relay 2L035K402 failed to close contacts 4L-4M, which prevented 2HV4715 from closing.
Cause of the Event
The primary factor, which increased the frictional force (drag) associated with the main form "Y" contact blocks, was the slow, age-related degradation of the movable nylon hub (Figure 3). Scratching on the
'Y' contacts was a secondary factor that increased friction. This cumulative friction eventually overcame the spring return force and prevented the relay from fully counter-rotating to its fail safe "zero degree stop" position.
The 40 relays at SONGS (30 installed and 10 spare) were manufactured from 1989 through 1990 time frame and as such are subject to the same degradation mechanism.
Corrective Actions
SCE has determined that there is no need to utilize the form 'Y", high current contacts at SONGS Units 2 and 3. As such, a proactive approach will be implemented to replace all the SONGS P&B MDR-7032 relays with P&B MDR-7033 or P&B MDR-7034 relays, which do not contain form 'Y" contact blocks.
SCE also examined a spare P&B MDR-7032 relay that had been subject to the same conditions (age, number of cycles and normally energized). This spare relay also showed signs of this age related degradation, but its contacts operated correctly.
The testing of 30 installed (i.e., non-spare) MDR-7032 relays are being staggered each month so that at least three relays are tested each month. Thirteen of these relays have already been tested following the initial relay test failure and there have been no additional failures.
The performance of these relays will be trended during the performance of the subgroup relay testing until the new MDR relay is installed.
Safety Significance
Valve 2HV4715 is located on AFW pump P-141 discharge piping to steam generator (SG) E-089. This valve is closed during plant operation (Mode 1) and fails as-is upon loss of power. Upon an EFAS actuation, the valve opens and closes to provide automatic SG level control. It is also the AFW isolation valve for SG E-089.U.S. NUCLEAR REGULATORY COMMISSION (MM-YYYY)
LICENSEE EVENT REPORT (LER)
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REVISION San Onofre Nuclear Generating Station (SONGS) Unit 2 05000361 2
NUMBER NUMBER 4of 7 There are two actuation signals for this valve generated by the ESFAS: (1) an EFAS, and (2) a Main Steam Isolation Signal (MSIS). These signals come from relays located in the ESFAS auxiliary relay cabinets. The EFAS initiates a signal for the valve to open to supply AFW to the SG for plant cool down in the event of a postulated Chapter 15 accident. MSIS initiates a close signal to isolate SG E-089.
ESFAS actuates separate relays for these actions.
The failed relay is not in the EFAS or MSIS actuation logic for 2HV4715. The P&B relay which opens 2HV4715 on EFAS (2L035K724) and the relay which close 2HV4715 on MSIS (2L035K723) did not experience the failure found in relay 2L035K402. Therefore, 2HV4715 would have been capable of closing on an MSIS. The failure of relay 2L035K402 to close valve 2HV4715 would only prevent the automatic control of SG E-089 water level, but would not (and did not) prevent control room operators from manually operating this valve. The close signal on the failed relay secures excess AFW flow by shutting valve 2HV4715 when the SG water level returns to above the low level setpoint and is not in the actuation logic for MSIS.
Although the EFAS 1 Train B was not able to automatically close 2HV4715 to secure excess AFW flow, it did not impact the ability of plant operators from detecting increasing water level in the SG E-089 and manually closing 2HV4715. Therefore, neither the health nor the safety of plant personnel or the public was affected by this condition.
Additional Information
On May 5, 1999, SCE reported a defect found in a different type of P&B relays resulting from insufficiently welded contact pads. This condition does not involve the same underlying concern or reason as this event. Therefore, the corrective actions taken would not have prevented this condition.U.S. NUCLEAR REGULATORY COMMISSION (MM-YYYY)
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Figure 1 II
- Potter and Brumfield Series 7032 Motor Driven Relay Form "C" Contacts:
(3 separate decks)
Form "Y" Contacts:
(3 separate decks)
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REVISION San Onofre Nuclear Generating Station (SONGS) Unit 2 l05000361 NUMBER l
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