Morning Report for Macrh 14, 2000
Headquarters Daily Report
MARCH 14, 2000
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REPORT NEGATIVE NO INPUT
ATTACHED INPUT RECEIVED RECEIVED
HEADQUARTERS X
REGION I X
REGION II X
REGION III X
REGION IV X
PRIORITY ATTENTION REQUIRED MORNING REPORT - HEADQUARTERS MARCH 14, 2000
Licensee/Facility: Notification:
Part 21 Database MR Number: H-00-0015
Eaton Cutler-Hammer Date: 03/14/00
Subject: Part 21 - Potential misapplication of zinc chromate plating
to circuit breaker parts
Discussion:
VENDOR: Eaton Cutler-Hammer PT21 FILE NO: 99-50-0
DATE OF DOCUMENT: 11/12/99 ACCESSION NUMBER: ML993240465
SOURCE DOCUMENT: EN 36428 REVIEWER: REXB, D. Skeen
Eaton Cutler-Hammer (E-CH) reported a potential for malfunction of
Westinghouse Type DS and DSL Class 1E circuit breakers. During breaker
reconditioning activities on 13 breakers for South Texas Project, some of
which had been previously refurbished by Westinghouse in 1994, E-CH
personnel discovered two breakers with hardened metal parts that had been
plated with zinc chromate. Plating of metal parts is a common practice to
improve the appearance of some parts. However, the plating process can
allow hydrogen to be diffused into hardened parts which can cause the
parts to become embrittled and cause cracking and breaking, if a heat
treatment is not applied to desorb the hydrogen (see NRC Information
Notice 96-46, "Zinc Plating of Hardened Metal Parts and Removal of
Protective Coatings in Refurbished Circuit Breakers", Accession No.
9608090035).
E-CH is now the manufacturer of DS and DSL circuit breakers, since buying
the manufacturing facilities for the 600-V circuit breaker product line
from Westinghouse in 1994, and has recently begun performing
safety-related breaker refurbishments. During disassembly of one breaker,
E-CH was removing a Spirol pin (trade name for a rolled metal pin) that
secures the levering shaft to the interlock plate, when it broke. The pin
appeared to be a gold color, indicative of zinc chromate plating. During
disassembly of a second breaker, E-CH found a roller constraining link,
which is normally blue-black in color, that was also plated with zinc
chromate.
Westinghouse Repair and Replacement Services told the NRC that the pin in
question holds the levering shaft to the interlock plate and that the pin
is not removed when the assembly is plated. Westinghouse believes that
plating the pin does not present a safety hazard because they have
received no reports of this pin failing in service.
Licensees may wish to inspect the Spirol pin and the roller constraining
pin for signs of damage and whether these parts have been plated during
the next scheduled maintenance interval.
See Morning Report H-00-0016 for related information. The NRC will post
ensuing reports on this subject on its website at
http://www.nrc.gov/NRC/PUBLIC/PART21/2000.
Contacts: Dave Skeen, NRR Steve Alexander, NRR Kamal Naidu, NRR
HEADQUARTERS MORNING REPORT PAGE 2 MARCH 14, 2000
MR Number: H-00-0015 (cont.)
301-415-1174 301-415-2995 301-415-2980
dls@nrc.gov sda@nrc.gov krn@nrc.gov
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HEADQUARTERS MORNING REPORT PAGE 2 MARCH 14, 2000
Licensee/Facility: Notification:
Part 21 Database MR Number: H-00-0016
Eaton Cutler-Hammer Date: 03/14/00
Subject: Part 21 - Potential application of incorrect torque
specifications to circuit breaker arc chute mounting bolts
Discussion:
VENDOR: Eaton Cutler-Hammer PT21 FILE NO: 99-51-0
DATE OF DOCUMENT: 11/12/99 ACCESSION NUMBER: ML993210268
SOURCE DOCUMENT: EN 36429 REVIEWER: REXB, D. Skeen
Eaton Cutler-Hammer submitted a 10CFR Part 21 report concerning
discrepancies discovered during circuit breaker refurbishment activities
(EN #36429, 11/12/99).
The original Westinghouse maintenance program manual (MPM) for DS low
voltage metal enclosed switchgear, written in 1993, listed the arc chute
torque values for DS-206 and DSL-206 breakers as 40-45 inch-pounds, and
values for the DS-400, -500, and -600 series breakers as 65-70
inch-pounds. Westinghouse Repair and Replacement Services (RRS) personnel
told the NRC that prior to putting together the MPM in 1993, no torque
values were given for the arc chutes, but because of customer complaints
of cracked arc chutes, Westinghouse decided to list torque values for the
arc chutes in the MPM. The reason for the difference in values between
the 206 model and the other models is that the design of the arc chute
boss on the higher series model breakers is more substantial than the
design of the arc chute boss on the 206 model. The Westinghouse values
were based on experimental data, i.e. tightening the arc chutes until
they cracked and then backing down from that value to provide margin.
Westinghouse also stated that the breakers were satisfactorily tested
seismically in 1994, using the stated 1993 MPM values.
Eaton-Cutler Hammer (E-CH) told NRC that they developed torque values for
the DS and DSL breakers when they took over production in 1994. The arc
chute torque values listed on the design drawing in 1994 was 20-24
inch-pounds for all DS and DSL breakers. There was no differentiation
between the 206 model and higher model numbers. However, E-CH stated that
they subsequently discovered a small error in the design drawing value,
and the correct torque values are given on the manufacturing instructions
(MI) that are used on the factory floor to assemble the breakers. The MI
lists the torque value as 24 +/- 2 inch-pounds. E-CH recently revised the
design drawing to reflect the correct torque value in October 1999.
Westinghouse revised the MPM in March 1999 and the arc chute torque
values were lowered to match the design drawing values for the DS-206
breakers. The values for the higher series breakers were also lowered to
40 +/- 5 inch-pounds. Westinghouse stated that the higher series values
were lowered to provide additional margin to preclude cracking the arc
chutes.
In addition to the torque value discrepancies, E-CH also noted that the
HEADQUARTERS MORNING REPORT PAGE 3 MARCH 14, 2000
MR Number: H-00-0016 (cont.)
o-rings used to hold the arc chute mounting bolt in place when the arc
chute is not mounted on the breaker, were damaged on some of the breakers
being refurbished.
At this time the safety significance appears to be minimal. No failures
of circuit breakers in service have been reported because of pieces of
the arc chutes or o-rings becoming dislodged and falling into the
operating mechanism. Also, it is unclear when the arc chutes were
cracked, or what torque value was used on the bolts of the cracked arc
chutes. It is possible that using the values in the Westinghouse MPM
could lead to arc chute cracking, but it is also possible that plant
personnel could overtorque the bolts if care is not taken to ensure that
the bolts are not overtightened during maintenance activities.
Licensees may wish to consider checking the torque value on the arc chute
bolts, checking the arc chutes for cracks, and inspecting the o-rings for
damage during the next scheduled breaker maintenance interval.
See Morning Report H-00-0015 for related information. The NRC will post
ensuing reports on this subject on its website at
http://www.nrc.gov/NRC/PUBLIC/PART21/2000.
Contacts: Dave Skeen, NRR Steve Alexander, NRR Kamal Naidu, NRR
301-415-1174 301-415-2995 301-415-2980
dls@nrc.gov sda@nrc.gov krn@nrc.gov
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REGION II MORNING REPORT PAGE 3 MARCH 14, 2000
Licensee/Facility: Notification:
Tennessee Valley Authority MR Number: 2-00-0009
Sequoyah 1 Date: 03/14/00
Soddy-Daisy,Tennessee
Dockets: 50-327
PWR/W-4-LP
Subject: SEQUOYAH UNIT 1 UNEXPECTED OPERATION OF RESIDUAL HEAT REMOVAL
RELIEF VALVE
Reportable Event Number: 36792
Discussion:
On March 17, 2000, at 0017 Unit 1 was in Mode 5 (cold shutdown), with the
reactor coolant system (RCS) temperature at 156 degrees F and 330 psig.
Operators were conducting a venting procedure on the residual heat
removal (RHR) system to remove any gas voids from the injection path, in
preparation for entering Mode 4 (hot shutdown). During this evolution,
the licensee believes that the Train A RHR discharge relief valve
unexpectedly lifted and released RCS water to the pressurizer relief tank
(PRT). The relief valve reseated and RHR A train was isolated with the
transient lasting approximately 30 minutes. The PRT rupture disc was
breached and approximately 1500 gallons of water was released to the
containment. RCS temperature and pressure after the event were 156
degrees F and 145 psig. The RCS release was contained in lower
containment and there were no personnel contaminations. The licensee is
evaluating the cause of the event and is in the process of replacing the
PRT rupture disc and relief valve, and plans to lift-test the replaced
valve.
Regional Action:
The resident inspectors have been following the licensee's
troubleshooting activities and corrective actions.
Contact: P. E. FREDRICKSON (404)562-4530
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