ML20088A554
| ML20088A554 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 04/05/1984 |
| From: | Fiedler P GENERAL PUBLIC UTILITIES CORP. |
| To: | Deyoung R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| References | |
| IEB-83-08, IEB-83-8, NUDOCS 8404120206 | |
| Download: ML20088A554 (6) | |
Text
_ _ - _ ______
GPU Nuclear Corporation
- Nuclear m'e=8r388 Forked River, New Jersey 08731-0388 609 971-4000 Writer's Direct Dial Number:
April 5, 1984 Mr. Richard DeYoung, Director Office of Inspection & Enforcement United States Nuclear Regulatory Comission Washington, DC 20555
Subject:
Oyster Creek N; clear Generating Station Docket No. 50-219 IE Bulletin No. 83-08
Dear Mr. DeYoung:
The purpose of this letter is to respond to the directives set forth in IE Bulletin No. 83-08 which is concerned with the proper operation of the circuit breakers with Undervoltage Trip Attachments (UVTA's) being used in safety related applications other than as Reactor Trip Breakers (RrB's). Our response to the specified action items in the subject bulletin are in an attachment to this letter.
If you have any questions, please call me or the Oyster Creek Licensing Manager at (609)971-4643.
Very truly yours, 2.
rd Vice President and Director Oyster Creek DBC:v1c/0501V Enclosure Sworn to anj Subscribed before me this g day of April 1984.
M\\@
OCR A Notary Public of New Jersey '
cc: Mr. J. Lombardo U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, MD 20014 NRC Resident Inspector l
Oyster Creek Nuclear Generating Station Forked River, NJ 08731 j
840412O206 040405 y
DR ADOCK 05000 6
GPU Nuclear Corporation is a subsidiary of the General Pubhc Utilities Corporation i
Attacnment Item No. 1 4
Identify applications of W type DB, W type DS, or GE type AK-2 circuit breakers with the UV trip feature as discussed in IEB 83-01 or 83-04 in safety related applications at your facility, other than as RTB's.
CP holders and licensees should also identify similar applications of other types of breakers by other manufacturers that use a W trip feature.
If ruch circuit breakers are used or planned for use, identify the system (s) involved.
Item No. 1 Response General Electric AK-2 circuit breakers with UV trip features used in safety related applications at Oyster Creek are listed below:
The circuit breaker trip function of items 13 througn 22 is considered important to safety for shedding of tne non-essential loads.
i Item Breaker No.
Bus Equipment Type 1
1A2 Containment Spray Pump No. 1-1 AK-2A-50 l
2 1A2 Containment Spray Pump No. 1-2 AK-2A-50 3
1A2 Core Spray Booster Pump NZO3A AK-2A-50 4
1A2 Core Spray Booster Pump NZO3D AK-2A-50 5
1A2 CRD Feed Pump NC08A AK-2A-50 6
182 Containment '.; pray Pump No. 1-3 AK-2A-50 7
1B2 Containment Spray Pump No. 1-4 AK-2A-50 8
1B2 CRD Eeed Wrp NC08B AK-2A-50 9
1B2 Core # ray Beaster Pump NZO3C AK-2A-50 10 182 Core Spray &;ister Pump NZO3B AK-2A-50 11 1A3 Service Water pump No. 1-1 AK-2A-25 12 183 Service Water dump No. 1-2 AK-2A-25 13 1A2 Shutdow:n Pump NUO2A AK-2A-50 14 1A2 Rx. Bld. Closed Cooling Water Pump 1-1 AK-2A-50 9
15 1A2 Building Exhaust Fan EF-1-5 AK-2A-50 16 182 Snutdown Pump NUO2B AK-2A-50 4
17 182 Shutdown Pump NUO2C AK-2A-50 18 182 Rx. Bldg. Closed Cooling Water Pump 1-2 AK-2A-50 19 182 Building Exhaust Fan EF-1-6 AK-2A-50 20 183 MCC 1832 AK-2A-25 21 1A1 Feeder to USS lAl AK-2A-75 22 1B1 Feeder to USS 1B1 AK-2A-75 -
Item No. 2a Review the design of tne UVTA and the connecting linkage. Using input from the breaker manufacturer, determine the design margin available to open the breaker. Evaluate whether or not this design margin is adequate in view of safety applications, considering possible problems of alignment, lubrication, adjustment of spring tension, etc., discussed in the " Description of Circumstances".
Item No. 2a Response
'Ibe GE type AK-2 Dreakers' WTA and associated linkage have been the subject of extensive reviews by utilities and tne manufacturer because of their reactor trip function on B&W PWR plants. It is acknowledged that the design margin for the WTA in performance of its circuit breaker trip function is small when considering the relatively slight trip torque available from the WTA trip spring possibly working against hardened trip shaft bearing luorication. At Oyster Creek, these creakers' trip function is considered safety related because they feed loads that are shed off busses picked up by the Emergency Diesel Generator during its loading sequence.
In reviewing the design of the breaker reset feature witn tne manufacturer, it appears that there is adequate design margin in the trip reset function for reliable breaker close operation when maintenance is performed following the manufacturer's recommendations.
Item No. 2b Describe the current breaker surveillance program, including details of test frequency, methodology, and response time measurement of WTA devices.
Item No. 2b Response Current surveillance on 12 of the 22 circuit breakers with a W trip feature is performed every refueling outage using surveillance procedure 636.2.001, " Diesel Generator Automatic Actuation Test".
The test positively demonstrates the capability of the circuit breakers to trip on loss of power and to sequentially reclose to prevent overloading the Emergency Diesel Generators.
The Site Preventive Maintenance Program has existed at the plant since 1977. The program is Dased on General Electric Instruction Manuals GEI-50299 (AK-2A-25) and GEK-7303 (AK-2A-50 & 75) recommendations. Those recommenda-tions from GE Service Advice 175 (CPPD) 9.3 that GE suggested as appropriate for Oyster Creek were included in the Program; specifically, Oyster Creek has been measuring the torque on the trip snafts and verifying the freedom of movement within the tripping and latching mechanisms of these breakers since 1982, while the checking of W function and timing devices (Dy removing the control power fuse) was added in 1983. PM for W function is performed, at the minimum, once every refueling outage cycle. The static time.
delay undervoltage tripping device used at Oyster Creek consists of an undervoltage device (including the UV coil, paddle and other attachments) mounted on the breaker, a static time delay box mounted separately from the
)
breaker and a control power transformer which is also mounted separately from the breaker. The UV coil circuit is continuously rated and will remain picked up as long as the voltage remains above the predetermined drop out voltage.
Plant procedure has established a required time delay of 2 to 6 seconds between loss of power to the UV control unit (tested by pulling the control power fuse) and breaker trip. Mechanical response time measurements, that is the time from UV coil dropout to tne time the breaker actually trips, have never been taken on these devices.
Iter. No. 2c Review operating experience with the circuit breakers in your plant identified in Item 1.
Provide a list of all malfunctions (both failure to trip and failure to close on demand) associated with tne UVTA, including the connecting linkages and latcning mechanisms. The list should include tne date of each malfunction, and the operating time prior to failure or date of installation, and the date(s) of major maintenance. In general, wnen tne circuit breaker UVTA is actuated on undervoltage and the breaker contacts do not open within the design time response, the NRC considers tne breaker to have failed.
Item No. 2c Response Based upon the review of available records dating back to 1972, a list of GE AK-2 circuit breakers with UVTA related failures was prepared below.
Please note that all of these breakers were installed prior to Decencer, 1969.
Maint. Date Failure Prior to Failure Item EXIuipment Date Failure Mode Apparent Cause 1.
MCC 1832 3/2/84 N/A To Trip Excessive friction on trip shaft resulting in high torque. RO # 84-002 being prepared.
2.
Serv. Water 9/16/83 3/7/82 To Trip Excessive friction on Pump 1-1 trip shaft due to a burr on the latch surface resulting in high torque RO #83-20 was issued.
3.
Serv. Water 11/30/83 10/5/78 To Trip Mechanical binding on the Pump 1-1 trip shaft. RO #78-31 was issued.
4.
Serv. W ter 11/30/78 N/A To Trip Mechanical binding on the a
Pump 1-2 trip shaft. RO #78-31 was issued.
1 Maint. Date Failure Prior to Failure Item E4uipment Date Failure Mode Apparent Cause 5.
RBOCW Pump 6/9/83 11/7/82 To Close Gag found tied around j
No. 1-1
& To armature coil. Static Trip time delay burned out.
RO #83-15 was issued.
6.
Core Spray 4/12/83 2/28/82 To Close Wrong UV coil was Booster Pump installed, static time NZO3A delay was burned. RO
- 83-08 was issued.
7.
Cont. Spray 11/26/78 6/10/77 To Close Excessive friction on Pump No. 1-3 bearings of trip bar. Ro (51C)
- 78-30 was issued.
8.
Cont. Spray 11/11/76 N/A To Close Excessive friction on Pump No. 1-4 bearings of trip bar, R0 (51D)
- 76-27 was issued.
9.
Cont. Spray 3/6/75 N/A To Close Excessive friction on Pump No. 1-1 bearings of trip bar. RO (51A)
- 75-5 was issued.
10.
CRD Feed Pump 3/31/83 2/23/80 N/A No UV test was performed.
NC08A Deviation was noticed during PM when trip shaft i
was found to be binding.
Breaker may have failed to trip. RO #83-04 was issued.
11.
Feeder to 8/18/83 N/A To Close Burned static time delay USS lAl unit, fuse & UV coil.
i 12.
Exhaust Fan 3/7/84 2/28/80 To Trip Circuit breaker failed to EF-1-6.
trip within time required in procedure. RO #84-002 being prepared.
13.
Shutdown Cooling 3/7/84 3/4/80 To Trip Circuit breaker failed to Pump #NUO2B trip within the time required in procedure.
RO #84-002 being prepared.-
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...s Item No. 2d Describe any preventive or corrective measures you have taken, or intend to take, based on the results of items 2a, 2D & 2c.
Include any revisions to the Surveillance Test Program and methodology. Specifically, address the inherent reliability of tne W trip feature in view of its apparent heavy dependence on intensive maintenance and surveillance, and whether a basic design change is warranted to correct the proolem, e.g., using a voltage sensitive relay to sense loss of voltage and energize the shunt trip coil from an independent DC source.
Item No. 2d Response Tne surveillance procedure used to perform tne Diesel Generator Automatic Actuation Test will be evaluated to determine if it snould be revised to add other breakers to the 12 of 22 circuit breakers now covered by this procedure to verify tripping. As discussed previously in item no. 2b, tnese 22 circuit breakers nave PM performed for W function, at the minimum, once eve y refueling outage cycle.
The PM procedure will be revised to incorporate tne remaining app 4icable recommendations listed in GE SA175 (CPPD) 9.3.
'mese items will be in addition to the items in the service advice tnat have already been included in the present PM procedure as discussed in item No. 2b of tnis response.
'It increase tripping reliaoility of the AK-2 circuit breakers, we are investigating tne feasibility of saodifying the control circuits for the twenty-two circuit breakers identified as performing a safety related function.
In addition, more frequent checks of the undervoltage trip mechanism will be made.