ML20138J317
| ML20138J317 | |
| Person / Time | |
|---|---|
| Issue date: | 02/04/1997 |
| From: | Chaffee A NRC (Affiliation Not Assigned) |
| To: | Barbaglia R AFFILIATION NOT ASSIGNED |
| References | |
| IEIN-92-027, IEIN-92-27, NUDOCS 9702070005 | |
| Download: ML20138J317 (4) | |
Text
. - . - . . . ~ .. - . . _. . .
February 4,1997 Mr. Robert L. Barbaglia
, Senior Claims Management Specialist Square D Executive Offices Executive Plaza Palatine. Ill 60067-7399
SUBJECT:
REQUEST FOR A TECHNICAL REVIEW 0F A DRAFT INFORMATION NOTICE ON THE THERMALLY INDUCED ACCELERATED AGING AND FAILURE OF ITE/GOULD A.C.
RELAYS USED IN SAFETY-RELATED APPLICATIONS Mr. Barbaglia:
The U.S. Nuclear Regulatory Commission is planning to issue an information notice on thermally induced accelerated aging and failure of ITE/Gould A.C.
relays at the Beaver Valley Nuclear Plant. We ask that you review the i
attached draft of that information notice to ensure that the technical information is accurate. Your cooperation in this matter is appreciated.
Please return any comments you may have as soon as possible. A copy of this
! request and your response will be placed in tb9 Public Document Room for
- review by the public. Your response should be mailed to
- 1 i
U.S. Nuclear Regulatory Commission l Washington. DC 20555-0001 ATTN: Nick Fields, NRR/PECB ,
3 MAIL STOP: 011E4 '
Please address any questions you may have on this matter to Nick Fields of my staff. Mr. Fields may be reached by phone (301) 415-1173 or you may fax
! comments to (301) 415-2279. If no comments are received by close of business 4 February 12, 1997, we will assume the technical information in the notice is i correct.
I I
{0riginal signed by Robert L. Dennig) j for Alfred E. Chaffee, Chief Events Assessment and Generic Communications Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation
Enclosure:
Draft Information Notice DISTRIBUTION TMartin DRPM R/F AEChaffee PECB R/F NFields Central Files PDR [
OFFICE PECB:NRR SC/PECB:NRR C/PECP M 'g0 3 PECB NFields 4/f/f7 EGoodwin N M AChaff[eY DATE 2/04/97 2/04/97 2/Y/97 ('
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, p_ r oC 060089 9'0207o005 7 970204 PDR hk IC -27 l
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- l UNITED STATES
". NUCLEAR REGULATORY COMMISSION I h 0FFICE OF NUCLEAR REACTOR prGULATION pETf WASHINGTON. D.C. 205% '
February xx. 1997 NRC INFORMATION NOTICE 92-27. Supplement 1: THERMALLY INDUCED ACCELERATED AGING AND FAILURE OF ITE/GOULD A.C. RELAYS USED IN SAFETY-RELATED APPLICATIONS Addressees All holders of operating licenses or construction permits for nuclear power reactors.
Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to problems resulting from the thermally accelerated aging of relays manufactured by the ITE/Gould Manufacturing Company (currently Telemechanique). The accelerated aging could lead to relay coil failure potentially rendering portions of associated safety-related systems inoperable. It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate. to avoid similar problems. However suggestions contained in this information notice are not NRC requirements: therefore, no specific action or written response is required.
Backaround in Information Notice 92-27. " Thermally Induced Accelerated Aging and Failure of ITE/GOULD A.C. Relays Used in Safety-Related Applications". April 3. 1992.
the NRC staf f informed licensees of the failure of three safety-related relays at the Millstune Nuclear Power Station. Unit 3. The relays were installed in the control circuits of three safety-related motor-operated valves (MOVs).
These relays provided control power alarms and thermal overload protection for the MOVs.
The relays. which had been in cervice for about 7 years, were model J10 relays with J20M magnet block assemblies and standard G10JA126. 120V. 60 cycle coil assemblies manufactured by ITE/Gould. Inspection of the relays revealed that the movable plastic armature carrier. which surrounds the core and coil, and the retainer for the magnet yoke assembly were discolored, brittle, and severely cracked. Insulation degradation was severe. allowing electrical shorts to develop within the co11s. The licensee concluded that the failures resulted from the thermal aging of the coll assemblles and plastic parts near the coil assemblies. The failed relays were mounted shoulder-to-shoulder in a horizontal " ganged" arrarigement on a universal mounting strip supplied by the manufacturer. They were originally qualified, individually, for the life of the plant.
l DRAFf 1N 92-27. Su February xx.p 1 1997
, Page 2 of 3 Descriotion of Circumstances On October 11. 1996. Duquesne Light Company determined that J12 relays with J20M magnet block assemblies and standard G10JA116. 120V, 60 cycle coil assemblies manufactured by ITE/Gould and installed at Beaver Valley Unit 2 were susceptible to thermally induced premature aging. (Licensee Event Report No. 96-005-00, November 11. 1996. NRC Accession No. 9611210045). These relays provide alarms. " Bypass Inoperable Status Indication", and thermal overload protection for various MOVs fans, and pumps. Systems potentially affected included safety injection, component cooling, charging, instrument air, quench spray, recirculation spray, service water, and emergency diesel generators.
Four of the J12 relays failed during routine outage testing. In each case.
. the normally energized relays had been deenergized for several days during electrical bus maintenance. When the relays were reenergized, two contact pairs on the relays failed to pick up. This mode of failure would have prevented manual operation of the safety-related valve that the relay controlled, but did not affect the automatic engineered safety features (ESF) actuation function. The ESF portion of the circuit bypasses the failed thermal overload relay and contacts.
The relays had been installed for 9 years. Thermal aging had caused the magnetic yoke assembly retainer and the movable plastic armature carrier, which surrounds the core and coil, to become discolored deformed, brittle, and cracked. The deformation of the armature carrier was sufficient to interfere with free movement of the armature assembly and prevented pickup of the contacts. Following each of the four J12 relay failures at Beaver Valley.
the power supply circuit breaker was opened and reclosed. The relay contacts then made up as expected following this cycling of the power supply breaker.
The relay degradation may have remained unknown if the licensee had not investigated the anomaly further.
The licensee postulated that the failures of the contact pairs to pick up on the four J12 relays may be a precursor to coil failure and loss of control power similar to that reported in Information Notice 92-27. The licensee determined that the J20M armature assembly was also installed in J10. J11.
J13 and J14 class relays. The licensee stated that only the J10. J12. and J13 relays were normally energized and therefore, susceptible to thermally induced accelerated aging.
Approximately 223 J12 relays are installed at Beaver Valley Unit 2. None have been identified at Beaver Valley Unit 1. Before transitioning from mode 4 to mode 3 operation, the licensee replaced all J-class relays that were deemed susceptible to thermally induced accelerated aging.
Discussion The J12 relay is one of a family of J-class relays currently manufactured by Telemechanique as commercial-grade items. Although the NRC staff is aware of failures of J-class relays at other facilities, most of the failures occurred during surveillance testing and were attributed to " normal aging." The NRC staff is not aware of any analyses performed to determine the root cause for
DRAFT IN 92-27. Sup 1 February xx. 1997 '
. Page 3 of 3 the failures at these other facilities. In analyzing the failure mode of the relays at Beaver Valley. the licensee determined that if the relay remains energized. the contacts remain shat, the armature field remains steady. and. I therefore, there is no excessive current to cause insulation breakdown and '
circuit failure. However because the relay is continuously energized. the resultant high temperature causes the plastic carriage material to deform.
When the relay is deenergized. the spring-loaded armature assembly separates l the two magnet halves. This creates the armature gap. When the relay is reenergized, the deformed plastic carriage restricts motion of the armature assembly which. in turn, mairitains the large armature gap. With the large gap the circuit current is greater than normal. The higher current causes increased heat to be generated, eventually resulting in the breakdown of coil insulation and the development of a short circuit in the coil of the relay.
The short circuit could cause the fuse in the control power circuit for the component to open, rendering the component inoperable.
Information Notice 92-27 focused on the importance of the thermal effects resulting from ganged mounting of J10 relays. The information notice may not have adequately emphasized that the problem could exist with different mounting configurations and with other J-class relays.
This information notice requires no specific action or written response. If you have any questions about the information in this notice. please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
T. Martin. Directe '
Division of Reactor Program Management Office of Nuclear Reactor Regulation Technical contacts: D. Kern. Region 1 N. Fields. NRR (412) 643-2000 (301) 504-1173 Email - dmk@nrc. gov Email - enf@nrc. gov
Attachment:
List of Recently Issued NRC Information Notices 1