Category:NRC Information Notice[Table view]The following query condition could not be considered due to this wiki's restrictions on query size or depth: <code> [[:Beaver Valley]] OR [[:Millstone]] OR [[:Hatch]] OR [[:Monticello]] OR [[:Calvert Cliffs]] OR [[:Dresden]] OR [[:Davis Besse]] OR [[:Peach Bottom]] OR [[:Browns Ferry]] OR [[:Salem]] OR [[:Oconee]] OR [[:Mcguire]] OR [[:Nine Mile Point]] OR [[:Palisades]] OR [[:Palo Verde]] OR [[:Perry]] OR [[:Indian Point]] OR [[:Fermi]] OR [[:Kewaunee]] OR [[:Catawba]] OR [[:Harris]] OR [[:Wolf Creek]] OR [[:Saint Lucie]] OR [[:Point Beach]] OR [[:Oyster Creek]] OR [[:Watts Bar]] OR [[:Hope Creek]] OR [[:Grand Gulf]] OR [[:Cooper]] OR [[:Sequoyah]] OR [[:Byron]] OR [[:Pilgrim]] OR [[:Arkansas Nuclear]] OR [[:Braidwood]] OR [[:Susquehanna]] OR [[:Summer]] OR [[:Prairie Island]] OR [[:Columbia]] OR [[:Seabrook]] OR [[:Brunswick]] OR [[:Surry]] OR [[:Limerick]] OR [[:North Anna]] OR [[:Turkey Point]] OR [[:River Bend]] OR [[:Vermont Yankee]] OR [[:Crystal River]] OR [[:Haddam Neck]] OR [[:Ginna]] OR [[:Diablo Canyon]] OR [[:Callaway]] OR [[:Vogtle]] OR [[:Waterford]] OR [[:Duane Arnold]] OR [[:Farley]] OR [[:Robinson]] OR [[:Clinton]] OR [[:South Texas]] OR [[:San Onofre]] OR [[:Cook]] OR [[:Comanche Peak]] OR [[:Yankee Rowe]] OR [[:Maine Yankee]] OR [[:Quad Cities]] OR [[:Humboldt Bay]] OR [[:La Crosse]] OR [[:Big Rock Point]] OR [[:Rancho Seco]] OR [[:Zion]] OR [[:Midland]] OR [[:Bellefonte]] OR [[:Fort Calhoun]] OR [[:FitzPatrick]] OR [[:McGuire]] OR [[:LaSalle]] OR [[:Fort Saint Vrain]] OR [[:Shoreham]] OR [[:Satsop]] OR [[:Trojan]] OR [[:Atlantic Nuclear Power Plant]] OR [[:Crane]] </code>.
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 accelerated aging and
failure of 120Y ac relays manufactured by the ITE/Gould Manufacturing Company
(currently Telemecanique).
The relay failures rendered portions of the associ- ated 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.
Description of Circumstances
On November 23, 1991, while performing an eighteen month engineered safety
features operability test, the licensee for the Millstone Nuclear Power
Station, Unit 3, noted that control power was interrupted to three safety- related motor operated valves (MOYs). The valves were located in the charging, component cooling water, and steam generator atmospheric dump systems.
The
licensee inspected the valves' control power circuitry and determined that
three normally energized auxiliary relays had failed.
These relays provided
control power alarms and thermal overload protection for the MOYs. The relay
The relays, which had been in service for about seven years, were class J10
relays with J20M magnet block assemblies and standard G1OJA126, 120V, 60 cycle
coil assemblies manufactured by the ITE/Gould Manufacturing Company.
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 coils. The licensee concluded that the
failures resulted from the thermal aging of the coil assemblies and plastic
parts near the coil assemblies.
9203270157 ;Z4-
IN 92-27 April 3, 1992 The failed relays were mounted shoulder to shoulder in a horizontal "ganged"
arrangement on a universal mounting strip supplied by the manufacturer. The
three relays that failed were each mounted in the middle of a ganged relay
cluster. The relays were originally qualified, individually, for the life of
the plant.
However, the qualification process did not account for the use of
the relays in the ganged arrangement. The licensee stated that the potential
heat induced degradation of "weak-link" materials such as the plastic armature
carrier was not considered in the qualification test report.
The licensee inspected relays in other safety and nonsafety systems and found
similar discoloration and embrittlement caused by overheating, but found no
additional failures. The Millstone licensee has replaced approximately 260
relays with identical components from spare motor control centers. Long term
corrective actions include periodic monitoring and replacement and/or physical
separation of ganged relays.
During the period April 1987 through August 1987, the licensee for the Seabrook
Generating Station experienced similar failures of ITE/Gould J-10 relays.
Following those failures, Telemecanique submitted a report to the NRC under
Title 10 of the Code of Federal Regulations (10 CFR), Part 21 (Part 21 report)
describing the Uailures at Seabrook. The report attributed the overheating
failures to the special low voltage coils in the J10 relays that were supplied
to the Seabrook Nuclear Station. Telemecanique stated that the relays supplied
to Seabrook were equipped with a non-standard magnet coil (identified as 816 with 50 ohms resistance) and, therefore, the failure mode would not be experi- enced at any other facility. The licensee for the Seabrook Station submitted a
Licensee Event Report (LER) to the NRC under 10 CFR Part 50.73 describing the
relay failures and their root cause analysis. The licensee stated in the LER
that, "...It was originally believed that excessive temperature resulted from
the close proximity of six normally energized relays...Subsequent investigation
led to the identification of relays not in close proximity with other energized
components that showed slight discoloration." However, the Seabrook licensee
accepted the Telemecanique Part 21 report conclusions that the failures were
due to the heat generated by the energized, non-standard coil.
The recent failures at Millstone suggest that the Seabrook licensee's original
conclusion may have been accurate. The gang mounting ("close proximity") of
these relays was likely a major contributor to the accelerated aging with
the condition being exacerbated by the additional heat generated by the contin- uously energized coil.
The J10 relay is one of a family of J-class relays currently manufactured by
Telemecanique as commercial grade items. Although the NRC staff is not aware
of the failure of any of the other J-class relays, these relays could be suscep- tible to similar heat induced degradation when gang mounted.
IN 92-27 April 3, 1992 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
