ML20202F829
| ML20202F829 | |
| Person / Time | |
|---|---|
| Issue date: | 07/10/1986 |
| From: | Merschoff E, Naidu K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| Shared Package | |
| ML20202F811 | List: |
| References | |
| REF-QA-99900270 NUDOCS 8607150239 | |
| Download: ML20202F829 (7) | |
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ORMNIZATION: WESTINGHOUSE ELECTRIC CORPORATION BEAVER, PENNSYLVANIA REPORT INSPECTION INSPECTION N0.: 99900270/86-01 DATES: 5/12-13/86 ON-SITE HOURS: 11 CORRESPONDENCE ADDRESS: Westinghouse Electric Corporation Control Products Division ATTN: Mr. C. J. Kruzic, General Manager Components Division 1 Toscirawas Road Beaver, Pennsylvania 15009 ORGANIZATIONAL CONTACT: Mr. G. Dore, Product Manager TELEPHONE NUMBER:
215-775-2000 NUCLEAR INDUSTRY ACTIVITY: Manufactures commercial grade low voltage and me-dium voltage circuit breakers.
ASSIGNED INSPECTOR:
8-78a/fu h 7//M~
K. R. NaTdu, Reactid(e Inspection Section (RIS)
' Dhte OTHER INSPECTOR (S):
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APPROVED BY:
E. W. Merschoff, Chiief, RIS, Vendor Program Branch Date' INSPECTION BASES AND SCOPE:
A.
BASES: Appendix B to 10 CFR Part 50.
i B.
SCOPE: Obtain additional information on low voltage trolded case circuit breakers, type 22250 MW, which failed at the Peach Bottom Units 2 & 3 and Limerick nuclear power plants ar.d review the documentation supporting the Certificates of Conformance issued with the circuit breakers.
i PLANT SITE APPLICABILITY: Limerick Unit 1 (50-352); Peach Bottom Units 2 & 3 l
(50-277; 50-278).
f8607150239)B60714 PDR GA999 EMVWEST 99900270 PDR l
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ORGANIZATION: WESTINGHOUSE ELECTRIC CORPORATION BEAVER, PENNSYLVANIA INSPECTION REPORT RESULTS:
l PAGE 2 of 7 NO
- 44400270/86-01 A.
VIOLATION:
fone.
B.
NONCONFORMANCES:
None.
C.
UNRESOLVED ITEMS:
None.
D.
INSPECTION FINDINGS AND OTHER COMMENTS:
1.
Background Information:
On February 6,1986, a molded case circuit breaker (breaker), type LBB 22250MW, experienced a failure at the Peach Bottom Unit 2 nuclear power plant. Specifically, the shunt trip coil, which trips the breaker to interrupt abnormal power to the Reactor Protection System (RPS), overheatei and failed. On January 16 and E4, 1986, similar problems were ic 1tified in identical breakers at the Peach Bottom Unit 3 nuclear power plants and on November 9, 1984, similar problems were identified in identical breakers at the Limerick Unit I nuclear power plant.
These breakers were purchased by ASCO Electrical Products (AEP),
Parsipanny, New Jersey and assembled in a RPS power monitoring panel supplied to the Peach Bottom and Limerick nuclear power plants.
The NRC inspector reviewed the engineering specification for the RPS monitoring panels, the associated procurement documents and the quality-assurance docurents, including Certificates of Conformance for the failed breakers at AEP. The NRC inspector visited the Limerick and Peach Bottom nuclear power stations to obtain additional information on the failure mecha~nisms exhibited by the breakers.
Representatives of the licensee inforced the insoector that they l
I sent twc failed breakers to Westinghouse Beaver (WB) for analysis.
WB documented the results of their analysis on the failed breakers in a report. WB considers this report proprictary. The purpose of this inspection was to discuss the results of the tests perforced on the failed breakers and:
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' ORGANIZATION: WESTINGHOUSE ELECTRIC CORPORATION BEAVER, PENNSYLVANIA REPORT INSPECTION HL: 99900270/86-01 RESULTS:
PAGE 3 of 7 Evaluate whether similar failures could adversely affect the a.
safe operation of Limerick and Peach Bottom nuclear power
- plants, b.
Determire whether the failure mechanism is generic to all LBB 22250 type breakers.
c.
Determine whether Westinghouse manufactures other types of molded case breakers which are susceptible to this failure mode when coerated with a shunt trip coil.
d.
Determine whether tests could be performed on a breaker in the field to ascertain whether the breaker is susceptible to failure.
Verify whether the corrective action taken by Westinghouse to e.
preclude further failures is adequate.
2.
Review of the Results on Tests Performed on Failed Circuit Breakers:
The inspector discussed the normal operation of LBB 22250MW type circuit breakers, the failures experienced at the Peach Bottom and Limerick nuclear power plants, and the results of the tests per-formed on the two failed breakers which were sent to WB. Repre-sentatives of Philadelphia Electric Company (owner of Peach Bottom and Limerick); Westinghouse, Nuclear Services Integration Division (NSID) Monroeville; and WB Control Products Division, participated in the discussions.
a.
Normal Operation LBB 22250W type breakers equipped with a shunt trip coil (STC) interrupt the power to the Reactor Protection System (RPS) when an undervoltage, overvoltage or underfrequency (abnormal) condition is sensed. An abnormal condition closes a contact to energize a STC. The STC is internally connected to an auxiliary switch ("A" contact) installed in the breaker. The "A" contact opens when the breaker is open (0FF or deenergized) or tripped (subsequent to a trip) and closes when the breaker is closed (ON). The "A" contact is actuated by the movement of the breaker contact arms. When the breaker is closed (ON), the "A" contact closes and is ready to receive a signal to momentarily energize the STC. Any abnormal condition in the RPS power supply would energize the STC and trip the breaker. When the trip occurs, the operating handle will move to the trip position. When the l
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ORGANIZATION: WESTINGHOUSE ELECTRIC CORPORATION BEAVER, PENNSYLVANIA c
c REPORT INSPECTIOM NO.-
99900270/86-01 RESULTS:
PAGE 4 of 7 operating handle r.cVes into the trip position, the "A" contact should open and de-energize the STC.
If the "A" contact does not open, the STC wculd continue to be energized, overheat and fail. The STC is rated for momentary energization; not contin-uous energization. The failures at Peach Bottom and Limerick occurred when the "A" contact did not open and de-energize the STC. A breaker with a failed STC will not serve the intended safety-related functi'on.
.b.
Results of Tests on Failed Breakers A representative of WB stated that the test results indicated that there was problem with the operating handle post (OHP). A rivet connects the OHP to the breaker mechanism.
Excessive material was observed in the rivets of the failed breakers.
The excessive material impedes the breaker contact arms from being fully displaced to the open position when the OHP is physically restrained in the "0N" position subsequent to a trip.
In this mode, eventhough the breaker is tripped, the OHP can physically be made to remain in the ON position. When the OHP is in this position the "A" contact will not open be-cause it is actuated by the breaker's moving contact arm.
Furthermore, the CHP will not return to the " tripped" position, if the OHP is forcibly kept in the ON position after a trip occurs due to the excess material on the rivet. WB stated that LB 2M50, HLB 22250 and DA 22250 (rated for 240 volts) type brer.kers, when used with a STC, are susceptible to the same failure mode, c.
Tests to Detect A Defective Breaker WB stated that the following tests could be performed in the field to detect a defective breaker.
1)
Perfcrm a continuity check on the STC after each breaker operation.
2)
Ranua11y close the breaker and continue to hold the OHP in the ON position. Apply a source voltage suitable to the STC via the two leads exiting the breaker (which are wired to the terminal ' block) until the breaker trips or 1 second has elapsed. While continuing to hold the OHP in the ON position, perform a continuity check of the shunt trip circuit. Continuity indicates that the "A" contact did i
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ORGANIZATION: WESTINGHOUSE ELECTRIC CORPORATION BEAVER, PENNSYLVANIA REPORT INSPECTION NO.-
99900270/86-01 RESULTS:
PAGE 5 of 7 r.ot open and is defective. An open circuit indicates that the 'A' contact did perform its function and therefore is not defective.
d.
Corrective Action Taken to Preclude Recurrence WB stated that Assembly Drawing,1259 C58, for the circuit breaker mechanism assembly for LBB, LB, HLB, and DA type breaker was revised to require the rivet to be ground off and specifies a maximum height of 0.035" of pin rollover.
3.
Review of Quality Assurance Manual WB stated that the molded case circuits bresker: 3re manufactured at the Puerto Rico and Beaver facilities to Underwriter Laboratories (UL) specifications. UL inspectors periodically visit the Beaver facility. WB gave the NRC inspector a QA manual and stated that the manual is being revised. The following sections of this manual were reviewed:
a.
Incoming Material Control Samples of' incoming material are inspected to the pertinent specifications.
Each shipment is held in the receiving area until inspection is complete. A Material Rejection Notice is prepared to document adverse findings on rejected material.
A red tag is attached to the material. The purchasing depart-ment prepares a Qualified Suppliers List and maintains it by evaluating the data documented in Vendor Rating Reports.
b.
Process Controls The manufacturing process is controlled by physical, visual, and electrical tests and in-process inspection of assemblies, components, and material. The Quality Control department for-mulates the product quality plan including inspecticns, sam-pling plans, audits, and procedures to insure manufacturing product compliance to the designed quality criteria. Quality control instructions are given in the form of engineering drawings identified by breaker designated style numbers. When a particular style number breaker is assembled, the relevant drawing is made available at the work station. The drawing lists the components and provides detailed manufscturing in-formation including electrical tests, markings, special rout-ings, and packaging.
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ORGANIZATION: WESTINGHOUSE ELECTRIC CORPORATION BEAVER, PENNSYLVANIA REPORT INSPECTION NO.-
99900270/86-01 PESULTS:
PAGE 6 of 7 l
c.
Control of Nonconformina Material QC inspectors inspect material produced in-house and unaccep-table material is identified with a " Defect Apparatus" tag. QC inspectors perform receipt inspections on material received from vendors, document unacceptable findings on a Material Re-jection Notice, identify the material with a red tag, and se-gregate i t.
d.
Tests on Circuit Breakers Tests are performed on breakers to verify that trip mechanisms respond to published values of thermal and magnetic trip set-tings to satisfy the UL 489 requirements. All tr% units are individually tested and calibrated to verify that they meet the specified values. Additionally, followup tests are performed to meet UL requirements. Samples are pulled from breaker lots and are divided into three categories namely, x, y, z and are s.ubjected to the following tests:
1)
The breakers in lot x are subjected to 200% and 135% of the rated current to verify that the breakers trip within the specified time. An ov~erload test consisting of 50 interruptions at 600% of rated current is also conducted.
Temperature rise is measured at rated current' until the temperature stabilizes. The dielectric strength is veri-I fied by applying 2x rated voltage plus 1000 volts.
2)
The breakers in lot y are subjected to 200% of the rated current to verify that the breakers trip within the speci-fied time.
Repetitive switching operations are performed to determine the mechanical endurance of the operating re-chanism. A specified number of operations are performed at no load and rated load.
Following the above tests, the time to trip at 200% rated current and the dielectric strength are verified.
3)
The breakers in lot z are subjected to 200% of the rated current to verify that the breakers will trip within the specified time.
Interruptions at 1000 amperes at rated voltage are performed on individual poles in the following manner:
One open and one close-open test.
One three pole open test.
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ORGANIZATION: WESTINGHOUSE ELECTRIC CORPORATION BEAVER, PENNSYLVANIA REPORT INSPECTION NO.-
99900270/86-01 RESULTS:
PAGE 7 of 7 To ensure the proper functioning of the trip elements in the breakers following a short circuit, tests at rated voltage and current are repeated.
4.
Review of Certificates of Conformance Backup Data:
Three Certificates of Compliance were issued along with the LBB22250 MW type breakers supplied to Asco Electric Products, ?arsipanny, New Jersey stating that the breakers comply with Westinghouse-Quality Standards and that " Inspection and test reports, where contractually required, are on file and available for inspection." WB stated that the subject breakers were not individually tested and therefore no backup documentation exists. The tests referred to were UL type tests and tests performed to qualify the breakers to IEEE-323-1974 and IEEE-344-1975. The inspector determined that the codes were improperly used.
E.
PERSONS CONTACTED:
Westinghouse Electric Corporation Control Products Division Beaver, PA G. Dore, Product Manger J. Salvati, Engineering Section Manager R. Ringer, Quality Panager Westinghouse Electric Corporation Nuclear Services Integration Division Monroeville, PA J. Jelovich, Manager, Equipment Qualification (EQ)
Programs G. C. Steinel, Senior Engineer, EQ R. Barnet, Quality Engineer, NTSD.
Philadelphia Electric Ccmpany - Limerick Station C. Harmon, Quality-Assurance Engineer f
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