B15776, Forwards Response to RAI Re 24-month Fuel cycle-electrical Power Systems Surveillance Extensions
| ML20116B416 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/23/1996 |
| From: | Feigenbaum T NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES SERVICE CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| B15776, NUDOCS 9607300020 | |
| Download: ML20116B416 (17) | |
Text
. - . . .
"'N N:rtheast ' d*" 8'" 8"* C* 7
. ' Utilities System Nonhe..: uta.serwce come.oy P.O. Box 270
, fl.rtford, CT 06141-0270 -
(203) 665-5000 July 23,1996 l Docket No. 50-423 B15776 Re: 10CFR50.90 i . U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Millstone Nuclear Power Station, Unit No. 3 l Proposed Revision to Technical Specifications 24-Month Fuel Cycle - Electrical Power Systems Surveillance Extensions - Additional Information ;
L - .
i l
The purpose of this submittal is to provide additional information to support the request i made by Northeast Nuclear Energy Company (NNECO) on June 14,1995,W to amend -
Operating License NPF-49, by modifying the surveillance requirements for the e electrical power systems (Technical Specification 3/4.8.) .Specifically, the proposed changes to the Millstone Unit No. 3 Technical Specifications would increase the
, surveillance requirements for the electrical power systems (e.g., offsite' power and l_ onsite power supply) from at least once per 18 months to at least once each refueling l interval (i.e., nominal 24 months).
A conference call was held on May 22, 1996 between the NRC Staff and NNECO representatives to discuss and resolve the Staffs questions on NNECO's submittal i dated June 14,1995. Attachment 1 provides responses to the Staff's questions.
l
, it should be noted that the safety assessment, significant hazards consideration, and :
l environmental impact discussions, previously included 'in the June 14, 1995, !
amendment request, remain valid. l L
There are no commitments made within this letter.
W J. F. Opeka letter to the U.S. Nuclear Regulatory Commission, " Millstone j Nuclear Power Station, Unit No. 3, Proposed Revision to Technical
- Specifications,24-Month Fuel Cycle - Electrical Power Systems, Surveillance Extensions," dated June 14,1995.
~ ^
96073O00'20 960723' ' 1 PDR ADOCK 05000423 /@, I P PDR
, .. . -.. ~
A
U.S. Nucle:r R:gul: tory C mmission 815776\ Page 2 Should the NRC Staff require any additional information, please contact Mr. R. G. Joshi at (860) 440-2080.
Very truly yours NORTHEAST NUCLEAR ENERGY COMPANY FOR: T. C. Feigenbaum Executive Vice President and Chief Nuclear Officer BY: -
6d C
- 8. E. Scace Vice President - Nuclear cc: T. T. Martin, Regional i Administrator V. L. Rooney, NRC Project Manager, Millstone Unit No. 3 A. C. Cerne, Senior. Resident inspector, Millstone Un!t No. 3
< Docket No. 50-423 815776 l
l l
Attachment 1 l
Millstone Nuclear Power Station, Unit No. 3 24-Month Fuel Cycle - Electrical Power System Surveillance Extensions !
Responses to the NRC Staffs Questions i
i l
I I
I July 1996 f
e .,
U.S. Nucl=r R:guittory Commission B15776%ttachment 1\Page 1
, Millstone Nuclear Power Station, Unit No. 3 24-Month Fuel Cycle - Electrical Power System Surveillance Extensions Response to the NRC Staff's Questions Question 1:
Licensees are to confirm that the performance of surveillances at the bounding surveillance interval limit for the 24 month operating cycle would not invalidate any assumption in the plant licensing basis. Where do you address this in your submittal?
Answer.
Based on the technical evaluations and safety assessment performed for each of the Technical Specification surveillance extensions, NNECO has confirmed that the performance of surveillances at the bounding surveillance interval limit provided to accommodate a 24 month fuel cycle would not invalidate any assumption in the plant licensing basis.
Question 2:
Licensees should have a program to monitor calibration results and the effects of instrument drift that will accompany the increase in the calibration intervals.
Where do you address this in your submittal?
Answer:
The Millstone Unit No. 3 l&C Department maintains a Drift Monitoring Program for instrumentation as described in NNECO letter to the NRC, B15306, dated July 26,1995. In addition, relays are calibrated by the Millstone Unit No. 3 Generation Test Services organization and records of the "AS FOUND" and "AS LEFT" settings are maintained. These values are recorded on the surveillance sheets which allow the setpoint drift to be determined.
OFFSITE AC POWER Question 3a. SR 4.8.1.1.1.b What is the normal circuit and the alternate circuit?
Answer:
The normal circuit is the Normal Station Service Transformer (NSST). The alternate circuit is the Reserve Station Service Transformer (RSST).
4 .
U.S. Nuciszr Ragul: tory Commission B15776%ttachment 1 \Page 2 Question 3b. SR 4.8.1.1.1.b
] In what modes can the surveillance be safely done?
Answer:
l The manual transfer can be safely performed in all modes of plant operation.
j The automatic transfer requires a Loss-of-Power signal k. test, and is normally l performed in modes 5 or 6.
l l Question 3c. SR 4.8.1.1.1.b
! The 4160 volt switchgear is stated to be Class 1E with components of high reliability and a "long mean time" to failure. What is the mean time to failure and l on what data is this based?
e i
Answer: >
- The mean time to failure is expressed in Thousands of Calendar Hours as s
determined by the Nuclear Plant Reliability Data System (NPRDS). The average i time between failures for medium voltage switchgear (4kV-15kV) is approximately 269 thousand hours between 1986 and 1995. This has been increasing yearly and in 1994-1995 the average was 540 thousand hours with 90% Confidence Limits DIESEL GENERATOR Question 4a. SR 4.8.1.1.2.g in what modes can the surveillance be safely done?
Answer:
If the performance of a refueling interval surveillance during plant operation would adversely affect safety, then NNECO will postpone the surveillance until the plant is shut down or is in a condition or mode that is consistent with safe conduct of that surveillance.
Question 4bi. SR 4.8.1.1.2.g The past performance of the diesels is stated to have been satisfactory. What were the surveillance results that this is based on?
Answer:
Surveillance inspections are completed in accordance with the manufacturer's recommendations. The actual inspections include review of the following diesel generator equipment: air start system, camshafts, crankshaft, connecting rods, exhaust manifold, fuel oil injection system, cylinder liners, frame bolts, gear and
'U.S. Nuclur Rrgulitory Commission B15776\ Attachment 1 \Page 3
~
pinion, alternator, main bearings, rocker arms and pushrods, turbocharger, and the Woodward governor.
During a conference call on May 22,1996 between NNECO and NRC personnel, NNECO provided the detailed information regarding the past inspection results, including rationale for extending the surveillance intervals for individual tasks that are normally performed at an 18 month frequency. In addition, NNECO has contacted the appropriate vendors to get their recommendations conceming this extension. The information received from the vendors, suppods our conclusion that the surveillance requirement can be extended from an 18 month frequency to a 24 month frequency.
Question 4b2. SR 4.8.1.1.2.g The diesels are run at least 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> monthly for SR 4.8.1.1.2.a.5 (not affected by the proposed changes) and the extended surveillance interval will have them run at least an additional 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />, from 44 to 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br />, in the 30 month maximum -
limit before SR 4.8.1.1.2.g is performed. What were the results?
Answer:
Extending the diesel generator from 44 to 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br /> between surveillance inspections is based on achieving acceptable results after reviewing the manufacturer recommendations.
Question 4b3. SR 4.8.1.1.2.g it is stated that there are existing engine monitoring programs that are conducted in conjunction with SR 4.8.1.1.2.a.5 and provide indirect evidence of engine problems: start time trending, cylinder temperature trending, and monthly lube oil analysis. Are these programs required by the Technical Specifications (TSs)
(the TS section) and what are the results?
Answer:
Start times are a Technical Specification requirement. Start times are not required by Technical Specifications to be trended, however, they are trended monthly and used for an early detection of diesel engine problems, especially starting air. There have been no major problems to date.
Cylinder temperatures are not a Technical Specification requirement, however, cylinder temperatures during monthly engine runs are reviewed by the system engineer. Deviations from specified temperatures are evaluated and corrective actions are taken when necessary. There have been no major problems to date.
Monthly-lube oil analyses are a vendor recommendation, not a Technical Specification requirement, however, trending lube oil analyses provides early '
i U.S. Nucinr Rtgulatory Commission B15776%ttachment 1\Page 4 detection of deteriorating engine conditions. Samples are taken at two locations:
the rocker arm area and the engine sump. Lube oil is tested for an array of I properties, including water content, which indicate an internal engine leak.
There have been no major problems to date, with the exception of occasional small amounts of water found in the rocker arm lube oil. This is a generic problem with the Colt Pielstick engine. Typically, any water leaks from the injector cooling hoses are easily correctable.
Question 4c1. For items 2 and 3 What did the past preventative and corrective maintenance for the past four operating cycles indicate whereby you concluded that the proposed extension ;
should cause no deterioration in the system condition or performance? !
Answer.
The preventative maintenance requirements for emergency diesel generator i systems which were reviewed are as follows: review tube oil analysis, review Colt SILs and perform inspections, remove all crankcase inspection covers, check turbocharger dischargo to interior cooler flange bolts, clean and inspect crankcase oil separator; inspect flex neoprene pipe connections; verify all fuel injection pump hold down bolts are wrenched tight; remove water jacket and intercooler Hx covers, lube oil filters, lube oil strainers, fuel oil transfer system, fuel oil filter elements, combustion air filter, instrument air filter, moisture detector circulating pump; drain and clean rocker arm lube oil reservoir; change ;
rocker arm tube oil filters; test air storage tank relief valves; and inspect fresh )
water system. Based on the evaluations of the above preventative maintenance ;
tas,ks and corrective maintenance tasks performed for the past four operating !
cycles, it is concluded that the above preventative maintenance and corrective I maintenance tasks can be performed once per each refueling (i.e. nominal 24 months). The details of the evaluation were discussed with the NRC staff in the conference call of May 21, 1996. Preventative maintenance reviews are ;
described in 'd' below.
Question 4d1. Foritem 4 What specifically was meant when you stated a review of the corrective maintenance records showed that none of the large number of maintenance activities in the diesel generators indicated any deterioration in the engine's ability to perform its function?
Answer.
Corrective maintenance activities were reviewed for the following subsystems:
diesel fuel oil, diesel lube oil, starting air, jacket and intercooler water exhaust, and combustion air. These entries were reviewed for evidence of equipment with an unusually high number of corrective maintenance work orders. The
'U S Nucl:rr Rzgulttory Commission B15778\ Attachment 1 \Page 5
, review did not reveal any particular subsystem or piece of equipment with unusual patterno of repetitive failures, with the exception of the air start control valves. The majority of tasks noted during the review were minor corrective maintenance tasks such as leak corrections, gasket replacements, bolt tightening, instrument calibrations, relief valve set point corrections, filter and strainer element replacements, lube oil changes, and heat exchanger cleaning i due to mussel fouling. The starting air system has had unrelated problems i attributed to rust and moisture in the system. Additional maintenance has been i performed, such as chemically . cleaning the starting air system, and modifications, such as replacing tubing and upgrading the air dryers, and has .
corrected these problems. No major failures which could render the diesels !
inoperable were noted.
l Question 4e1. For item 5 1 It is stated that, based on a review of the surveillance tests in the past four operating cycles, it can be concluded that the overall performance of the diesel generators has been very good. What were the results that the conclusion was !
based on? 4 Answer:
This surveillance (Diesel Generator autostart on an ESF signal) has always been successful for the original plant startup and four refueling outages. The overall performance of the diesel generator is very good, based on the successful performance of this surveillance, which is the case at Millstone Unit No.3.
Question 4fi. For item 6, 7, 8, and 9 lt is stated that based on a review of the surveillance tests in the past four operating cycles, it can be concluded that the overall performance of the diesel generators had been very good. What is the basis for this statement?
Answer:
All surveillances have been completed successfully. Based on the evaluations of the preventative maintenance and corrective maintenance tasks performed for the past four operating cycles, it is concluded that all preventative maintenance and corrective maintenance tasks can be performed once per each refueling (i.e.
nominal 24 months). The details of the evaluation were discussed with the NRC staff in the conference call of May 21,1996. The diesel sequencer timers have not had any failures and hence, no corrective actions requirement.
w.- e v--- --
m v m ---.-, , -. -
U.S. Nucl::r Rsgulatory Commission B15776%ttachment 1 \Page 6 Question 4f2. For item 6, 7, 8, and 9 What do the corrective and preventative maintenance records show?
Answer:
The only preventive maintenance recorded is the replacement of the light bulbs in the Sequencer Isolators in 1993. For corrective maintenance records, see Table 1.
Question 4g1. For item 10 ,
it is stated that based on a review of the surveillance tests in the past four l operating cycles, it can be concluded that the overall performance of the diesel j generators has been very good. What is the basis ior this statement?
Answer:
All surveillance tests were successful over the last four operating cycles, which provides assurance that the controls portion of the d:esel generator performs satisfactorily. The overall performance of the diesel generator is very good, when the individual surveillances have been successful, which is the case at Millstone Unit No. 3.\
Question 4g2. For item 10 What is the "long" mean time to failure for the components used in the control l circuits and what is the data that this is based on?
Answer:
A typical control circuit relay (GE type HFA) has a mean time to failure of 2,580 thousand calendar hours based on NPRDS figures for the years 1986-1994.
Other components in control circuits are switches, terminal blocks, and wiring.
The relays are cited as the life limiting component, because the coils are always energized and subject to failure. The other components are passive and not subject to overheating and subsequent failure.
Question 493 For item 10 You stated that monthly testing of the diesel generators operates the same logic relays ar.d control circuit that switch the diesel generator to the standby mode.
Is this a rquirement in the TSs (TS section) and what are the results?
Answer:
Yes, the Technical Specifications require the diesel generators to be started at least once each 31 days (7 days if failures occur) as required by SR 4.8.1.1.2.a.
The reference to the monthly testing was to illustrate that the control circuits verified during the refueling surveillance are the same circuits used in the
U.S. Nuclier Regulatory Commission B15776%ttachment 1 \Pa0e 7 l
, routine diesel testing. Correct control logic functioning is confirmed every month and at refueling.
Question 4h1. For item 11 l Do the statements in the paragraphs on the review of corrective and l
~
preventative maintenance records, that they could be done at power, mean all the maintenance tasks for this item could be done at power, or just the specific maintenance discussed in the letter can be done at power?
l Answer:
There are two fuel oil transfer pumps for each diesel fuel oil storage tank. i Therefore, all preventative and corrective maintenance can be safely completed :
at power.
Question 4h2. For item 11 ,
is the calibration of the fuel oil strainer pressure differential alarm required in the l TSs (TS section)? l l
Answer No, the calibration of the fuel oil strainer pressure differential alarm is not required l in the Technical Specification. l Question 4i1.For item 12 It is stated in the letter that a review of the past survoillance tests indicate the timing intervals were consistent and within the minimum resolution of 0.1 second. What is meant by " indicate"? Are these "past surveillance tests" over the past four operating cycles?
Answer:
The timing intervals are all consistent and within 0.1 second, because the timers are electronic and repeatability is always achieved. The word " demonstrates" is more appropriate than " indicate," to describe what the surveillance data has documented over the past four refueling cycles.
Question 4i2.For item 12 You referred to maintenance history that has indicated that there is no indication the proposed extended interval could cause deterioration in the load sequencer condition or performance. Does this maintenance history cover the history of the corrective and preventative maintenance over the past four operating cycles?
What is the specific data from this maintenance history?
I
U.S. Nucl=r R gul: tory Commission !
B15776%ttachment 1 \Page 8 !
Answer: l The maintenance history covers four ooerating cycles, with no problems being '
recorded with the electronic timers.
Question 4ji.For item 13 Based or: a review of the surveillance tests in the past four operating cycles, you stated that it can be concluded that the overall performance of the diesel generators has been very good. What is the basis for this conclusion: what are the results of the surveillance tests?
l Answer:
The overall performance of the diesel generators has been very good, based on successful surveillance testing for the last four cycles.
Question 4j2.For item 13 You stated that since 1986 only one corrective maintenance action was performed while performing this surveillance. This involved fuses being blown in the control circuit during testing and the surveillance procedure was revised, to i have the fuses removed during testing, to prevent the overload that may cause l the fuses to blow. Explain removing the fuses during the surveillance. Also, if a surveillance procedure was revised, does this not mean the test involved a TS surveillance?
Answer:
During a surveillance test in 1992, fuses were blown because the sequence needed to perform the test was involved and the technicians stopped in the middle of a sequence to investigate the voltage readings observed. This delay was long enough to cause a temporary overload condition to melt the fuse links.
A change to the surveillance procedure was processed to remove the fuses for that portion of the test and restore the fuses in a later step. No other problems have occurred since that event in 1992. The complete description is provided in Plant information Request PIR No. 3-92-028.
BATTERIES and CHARGERS Question 4ki. SR 4.8.2.1.c, .d, .e, and .f You stated that there has been no surveillance performed to comply with SR 4.8.2.1.f, because the batteries were only placed in the degraded condition after thu fourth refueling outage. Explain why this is true?
Answer:
A battery capacity test (performance test) is required every 60 months, unless a battery is in a degraded condition. The first time a degraded battery condition
J
, U.S. Nucl:tr R gulat:ry Commission B15776%ttachment 1 \Page 9 was determined was during the fourth refueling outage. Therefore, a performance test (SR 4.8.2.1.f) for a battery that showed signs of degradation was performed during the fifth refueling outage. The condition requiring a performance discharge test every 18 months, while shut down, did not exist until a battery was determined to be degraded. Now, the battery is evaluated with a l service test and a performance discharge test to comply with SR 4.8.2.1.d and l SR 4.8.2.1.f at each refueling outage.
Question 4k2. SR 4.8.2.1.c, .d, .e, and .f You stated that the only preventative maintenance performed on an 18 month frequency is the application of an equalizing charge which may be performed on a quarterly basis if required by E.aother quarterly surveillance. Explain what other surveillance, by number, requires this equalizing charge and what are the results of the surveillances?
Answer:
An equalizing charge is conducted to restore the batteries to a fully charged condition after a service test or performance test. An equalizing charge is also performed when low specific gravity or individual cell voltage conditions exists (Technical Specification Section 4.8.2.1.a or b measurements). There are no surveillances that require an equalizing charge. The Station Batteries have never been declared inoperable by either the Category A or B requirements of Technical Specification 3/4.8.2.
Question 4k3. SR 4.8.2.1.c, .d, .e, and .f You stated that during the last four operating cycles, the corrective maintenance performed on the batteries has included installing bubblers, replacing intercell connectors, investigating alarms, and other minor actions. Also, the corrective maintenance on the battery chargers has included installing new control boards, replacing relays, investigating alarms, and other minor actions. What other corrective maintenance on the batteries and battery chargers has been done?
Answer:
Corrective maintenance actions were described, except for other minor actions such as cleaning the cell tops and intercell connectors. It is our maintenance practice to maintain " good battery cleanliness" to prevent the degradation mechanisms from impacting battery performance later in battery life.
The battery chargers had the high voltage setpoint and time delay reset to a value that was recommended by the charger manufacture, when new overvoltage circuit boards were installed. No other corrective actions were noted.
U.S. Nucimr Rigulitory Commission B15776%ttachment 1 \Page 10 Question 4k4. SR 4.8.2.1.c, .d, .e, and .f in what modes can SR 4.8.2.1.d,e and f be safely done?
1 Answer '
SR 4.8.2.1.d, e and f can be safely done in modes 5 and 6.
PENETRATION PROTECTION Question 41. SR 4.8.4.1.a Which Final Safety Analysis Report (FSAR) section is containment penetration conduction overcurrent protection devices described in the FSAR7 l Answer:
FSAR Section 8.3.1.1.4.2.m, Design Criteria Electrical System Protection, describes the Electrical Penetration Protection. The electrical penetrations themselves are described in FSAR section 8.3.1.1.4.4, on page 8.3-26.
Question 4m1. SR 4.8.4.1.a.1 (RCP Circuit Breakers)
You stated that the overcurrent relays in the circuit breakers are reliable and stable devices and orevious surveillance data for the "as-found" setpoints that were recorded were compared to the protection curve given in the specification to determine if the penetration was being protected. The previous surveillance data is over what period of time (operating cycles) and what were the results?
Answer:
The four operating cycles were evaluated for the data recorded and the results were acceptable. The RCP penetrations can withstand 3,660 amperes for 40 seconds and have a continuous rating of 563 amperes. The IAC overcurrent relays provide protection to avoid excessive current for a prolonged period, which could damage the feed through power penetration seals. The protection relay time verses current curve, given in the overcurrent relay specification, is lower than the electrical penetration thermal capability current (amperage),
which assures the penetration is not damaged.
Question 4m2. SR 4.8.4.1.a.1 (RCP Circuit Breakers)
A system functional test was also successfully conducted at each surveillance test. What was tested and what were the results? This test was conducted over how many operating cycles?
Answer:
Following the relay calibration tests, which has been conducted successfully for the past four operating cycles, a System Functional Test is performed to verify the relays actually trip the circuit breakers to remove the overload condition.
.___ _ - ._ _.- - _ . _ . _ - _ _ = _ - . - . - - - . -. _-
! i j . l U.S. Nucisar Rcgulatory Commission l l
B15776\ Attachment 1 \Page 11 i . l i
i l j Question 4m3. SR 4.8.4.1.a.1 (RCP Circuit Breakers) ;
j You stated that the "as-left" setpoints are within (+/-) 5% of the trip value which is i less than the acceptance criteria of being within (+/-) 10% of the trip value. This '
is important if the measured drift of the setpoints is sufficiently small. Discuss the drift in setpoints values and over what time period was it measured?
Answer: !
The protective relays operate within a 5% tolerance band and the acceptance ;
criteria is 10% on either side of the desired setpoint. The requirement to always l maintain the setting within the conservative band was implemented in 1991, i when the relay data sheets were revised. This method gives added assurance that the "as-found" setting will be within the acceptable limits for a 24-month fuel cycle. There have been no reported problems with the IAC relays since 1991.
Question 4m4. SR 4.8.4.1.a.1 (RCP Circuit Breakers)
Two corrective maintenance adjustments were made to the hot trip settings for the relays in 1992. What were they? Were these the only ones in the past four operating cycles?
Answer:
Two adjustments were made in 1992 for the hot settings. The two RCP relays that were calibrated by the test department in 1992 had to be recalibrated, when the hot setting switch was changed, because the time dial began to move and eventually tripped the circuit breaker. The minimum pickup value was set too close to the actual running current, because of an interpretation of the setting procedure by the technician. This was the only incident of this type during the ,
RCP relay surveillance in the past four refueling outages. i A follow-up training session was held to make the test technicians aware of the importance and sensitivity of setting minimum pickup values on the IAC relays.
Therefore, this experience is not expected to recur. l Question 4m5. _ SR 4.8.4.1.a.1 (RCP Circuit Breakers)
You stated that your review of the service records revealed no adverse conditions that would prevent the protective relays from operating as designed.
Is this conclusion for the extended 24 month surveillance interval?
Answer:
Yes, our review of service records revealed no adverse condition to preclude normal operation of protective relays for the 24 month surveillance interval.
U.S. Nuclar Regulatory Commission B15776%ttachment 1 \Page 12 Question 4n. SR 4.8.4.1.a.2 (Lower Voltage Circuit Breakers)
Why was there a different total number of breakers tested each refueling outage?
Answer: '
The Technical Specification requires at least 10% of each type breaker to be '
selected on a rotating basis. Millstone Maintenance typically tests about one half of all molded case circuit breakers at each refueling outage and this ;
accounts for the different numbers reported. This number far exceeds the Technical Specification requirements, but is required by the maintenance j procedures.
Question 4o1. SR 4.8.4.2.1 (MOV Thermal Overload Protection Bypassed) :
You stated that since the plant was originally started up, there have been 6 periods when the valves have been tested. You did not state whether the tests involved the thermal overload device. Did the three failures discussed involve i the thermal overload device? l l
Answer: '
This surveillance is for testing the bypass feature of thermal overload protection during accident conditions. The three reported failures were detected while conducting testing for this surveillance requirement. The failures involved external wiring of the bypass interlock and a ground on a limit switch, which caused a control power fuse to blow. The overload heaters were not at fault.
Their are 60 MOVs that have the thermal overload heaters bypassed. The surveillance verifies that the bypass occurs; however, the thermal overloads are ,
checked as part of the maintenance procedure which inspects and cleans the !
motor starters.
Question 4o2. SR 4.8.4.2.1 (MOV Thermal Overload Protection Bypassed)
You did not present any data on the preventative and corrective maintenance of these devices. ,
Answer:
There are no recorded failures of the bypass relays.
The Preventative and Corrective Maintenance records for thermal overloads that are bypassed for accident signals indicated a blown fuse, resulting from a short ,
on the close limit switch, and a valve operator which did not stroke due to an open external permissive interlock.
_ _ _ _ _ _ _ _ - _ _ _ _ _ - . .. , _ . . _ _ _ _ _ _ , __ _ ~_ .
U.S. Nucl:gr R gul: tory Commission B15776%ttachment 1 \Page 13 l
Question 403. SR 4.8.4.2.1 (MOV Thermal Overload Protection Bypassed)
What is the total number of these devices?
l l Answer:
(
i There are 60 thermal overloads protection bypassed.
j Question 4p. SR 4.8.4.2.2 (MOV Thermal Overload Protection Not Bypassed) l What is the total number of these devices, of which 170 were tested in four i operating cycles?
Answer:
j There are 82 MOVs included in the surveillance for MOVs not bypassed, of which 25% are required to be tested.
4 i
l l
l f
-- y o,-.._p.
~- - - ~ . - .. --- - - -.-- - - _ .- - - .- -.- - -_ . - . ~. - - - .. ~ -
t TABLE 1 -
Corrective Maintenance Records for Sequencer Cabinets ,
s l
i in response to question 4f2. SR 4.8.1.1.1.b, items 6,7,8, and 9. !
-t The following is a table of corrective maintenance work orders on the sequencer cabinets 3RPS*PNLESCA&B sorted into seven categories. Each entry lists the !
number of corrective maintenance work orders found under that category and a note reference. Notes are added to provide further insight into the actual work !
performed by the work orders.
opticalisolators trouble shooting powersupply design changes card / relay test actuations other replacement t
3RPS*PNLESCA 19 18 1 20 5 5 3 :
note 1 note 2 note 3 note 4 note 5 note 6 note 7
)
3RPS*PNLESCB 17 6 3 12 6 3 .2 note 1 note 2 note 3 note 4 note 5 note 6 note 7 :
Note 1: The " optical isolator" field contains work orders that replaced optical isolators and light bulbs. ;
Note 2: The " trouble shooting" field contains work orders that were used primarily for investigative purposes. A large portion of these were dedicated to the !
intermittent failure of autotest state F19. Troubleshooting performed during RF05 traced the problem back to the voltage level outputted by specific cards ;
being lower than the guaranteed pick up level. Since the replacement of these cards, autotest state 19 has not failed. ;
Note 3: The " power supply" field contains woit orders that replaced parts on any of the three power supplies per cabinet. These power supplies had become obsolete and were replaced by PDCR MPt93-091. There have been no corrective maintenance work orders written against the new power supplies. ;
i Note 4: The "<1esign change
- field contains the work orders that were used to implement E&DCRs and rework of PDCR implementations. The majority of these work orders deal with E&DCR implementation in the early years of operation. Work done under design changes today are worked under DC work orders. [
t Note 5: The " card / relay replacement
- field contains the work orders that changed out cards and relays in the panels. Many of these work orders replaced input relays that showed high contact resistance. These relays were changed out per PDCR MP3-93-068 to gold plated cor. tact relays. To date none of these i newly installed relays have had corrective maintenance work orders written against them. l
[
Note 6: The " test actuations' field contains work orders that investigated various devices for the testability / ability to actuate various plant equipment. 1 Note 7: The "other" field contains the work orders that did not fall into the other categones ;
4 i