ML16341C154
| ML16341C154 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/16/1984 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML16340E357 | List: |
| References | |
| GL-83-28, NUDOCS 8406040130 | |
| Download: ML16341C154 (20) | |
Text
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DIABLO CANYON UNITS 1
8 2
DOCK ET NO. 50-275 AND 323 SAFETY EVALUATION GENERIC LETTER 83-28 ITEN 4 3
REACTOR TRIP BREAKER AUTOMATIC SHUNT TRIP 1
0 INTRODUCTION AND SUNNARY Generi c Letter 83-28 was issued by the NRC on July 8~
1983 indi-cating actions to be taken by Licensees based on the generi c im-plication of the Salem ATWS events.
Item 4.3 of the generic Letter requires that modifications be made to improve the reliability of the reactor trip system by implementation of an automatic actua" tion of the shunt attachmen't on the reactor trip breaker s.
The staff identified in its August 3~
1983~ safety evaluation report
-of the generic Westinghouse design-certain plant specif ic requests for information.
By Letter d'at ed December 20~
1983~ Pacifi c Gas and ELectric Company (PGSE) provided responses to the plant spe-cific questions.
The staff has reviewed the Licensee's proposed design for the automatic actuation of the reactor trip breaker shunt trip attachments and finds it acceptable.
The staff evaLua" tion is presented below.
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2.0 EVALUATION In response to the staff requests for plant specific information regarding the Westinghouse Owners Group (WOG) proposed generic de-sign of the modification of the reactor trip breaker automatic shunt trip the Licensee provided the information as described be" Low.
The staff requests and its evaluation of the information are presented below.
2.1 Provide the eLectricaL schematic/eLementary diagrams for
'he reactor trip and bypass breakers showing the under-voltage and shunt coiL actuation circuits as weLL as the breaker contro L (e.g.~
c Losing) circuits~
and. circuits providing breaker status information/alarms to the con-t ro L room.
The Licensee provided-the eLectricgL schematic diagrams for the reactor trip and bypass breakers showing the under voltage and the shunt trip circuits.
The des'ign of the eLectrical circuits have been reviewed and found to be consistent with the WOG generi c pro-posed design which was'previously reviewed and approved by the staff.
We find this is acceptable.
2.2 Identify the power sources for the shunt trip coils.
Verify that they are CLass 1E and that aLL components providing power to thy shunt trip circuitry are Class 1E and that any faults within non-class 1E circuitry wiLL not degrade the shunt t rip function.
Describe the annunciation/indi-cation provi ded in the controL room upon Loss of power to the shunt trip circuits.
ALso describe the overvoltage protection and/or aLarms provided to prevent or alert the operator(s) to an overvoltage condition that could affect both the UV coiL and the paraLLeL shunt trip actuation reLay.
Redundant Class 1E power sources are used for the shunt trip actu" at ion of the reactor trip breakers and for the shunt trip of the bypass breakers.
The additionaL shunt trip circuitry is powered f rom the reactor protection system regulated supply (48 Vdc).
CLass 1E circuitry is separated from non"1E circuitry.
Therefore~
a fault within non"C Lass 1E circuitry wiLL not degrade the shunt r
trip function.
This is in accordance with Regulatory Guide 1.75 and is ther efore acceptable.
The breaker position status Lights are used to supervise the avai Labi Lity of power to the shunt trip circuits.
The red Light..
which is connected in series with the shunt coil and the "a" aux-i liary contact indi cates that the break~
is closed and aLso indi-
~ cates that the power is available.to the shunt trip device and~
therefore provides detectabiLity of power f ai Lure to the shunt trip coiL.
A red indicating Light (non-CLass 1E) failure wiLL not im-pact the shunt trip'oil function. If the breaker is closed the green Light is off and the red Light is on.
If the red Light goes out with the green Light remaining off~ either a power Loss to the shunt trip coi L or a burned out bulb would be indicated.
Normally c Losed auxi Liary, swi tch contact of each breaker provides annuncia-tion when the breaker trips.
ALso~ normaLLy open auxiliary switch contact of each breaker provides breaker status information to the pLant computer.
Normally the shunt trip coils in the reactor trip breakers are in de-energized condition.
When the trip breakers are closed~
the red Lamp current (approximately 50 ma) flows through the trip coiL to monitor the circuit continuity which is not Large enough to actuate the trip coi L armature.
Since the current through the shunt trip coi Ls is interrupted when the breaker trips energiza-tion of the shunt trip coil is only momentary.
The maximum avaiL-able voltage occurs during a battery'qualizing charge at a maxi-mum vo Ltage of 115K of the nominaL voLtage.
Due to the short duty cycle of the shunt trip coi L~ it can operate at this overvoLtage condition without harmfuL effects.
The added shunt trip circuitry is powered from the reactor protec"
~ t ion Logic voLtage suppLy (48 Vdc7.
Components in the added shunt trip circuitry have been selected based on their abi Lity to perform
~I their intended function up to 115K of nominaL voltage.
The reactor protection Logic voltage is regulated with overvoltage protection set at 115K of nominaL voLtage.
Based on our review of the information provided by the Licensee,.
we conclude that appropriate consideration has been given to the as-pects of the design described above and the design is~ therefore~
a cceptable.
2.3 Verify that the relays added for the automatic shunt trip function are within the capacity of their=- associated power supplies and that the relay contacts are adequately sized to accomplish the shunt trip function.
If the added re Lays are other than the Potter 5 Brumfield MDR series relays (P/N 2383A38 or P/N 955655) recommended by Westinghouse~
provide a descript ion of the relays and their design speci-fications.
The added relays specified by Westinghouse for the automati c shunt t rip function are the Potter and Brumfield MDR series reLays (P/N 2383A38 for 125 Vdc or P/N 955655 for 48 Vdc).
The Licensee ordered MDR 5134 reLays directly from Potter"Brumfield which are the same as Westinghouse P/N 955655.
West inghouse has verified that the re Lay contacts are adequately sized for the shunt trip function and are within the capacity of their associated power supplies.
We find this. is accept~ Le.
2.4 State whether the test procedure/sequence used to indepen-dentLy verify operabiLity of the undervoltage and shunt trip devices in response to an automatic reactor trip signaL is identical to the test procedure proposed by the Westinghouse Owners Group (WOG).
Identify any differences between the WOG test procedure and the test procedure to be used and provide the rationale/justification for these di ffer ences.
The Licensee plans to implement
~ a test procedure that is function-aLLy simiLar to the WOG proposed procedure.
The staff wiLL re-I quire that the test procedure be provided for staff review when it is availabLe.
However~ this matter need not delay implementation of the proposed modification and is subject to subsequent staff review.
2.5 Verify that the circuitry used to impLement the automatic shunt trip function is C lass 1E (saf ety related)
~
and that the procurement~
instaLLation~ operation~ testing and main-tenance of this circuitry "wi LL be in accordance with the quality assurance criteria set forth in Appendix B to 10 C FR Pa rt 50.
The Licensee confirmed that the circuitry used to impLement the automatic shunt trip function is C Lass 1E (safety re Lated) and the procurement~
instaLLation~ operation~ testing and maintenance of this circuitry wi Ll be in accor dance with the quality assurance criteria set forth in Appendix B to 10 CFR Part 50.
We find this i s accep tab Le.
26 Verify that the shunt trip at'tachments and associated circuitry are/yiLL be seismicaLly qualified (i.e.~
be demonstrated to be operable during and aft'er a seismi c event) in accazdaace with t5e provisions of Regulatory Guide 1.100~
Revision 1
whi+h endorses IEEE Standard 344~
and that a LL non-safety.
related circuitry/components in physicaL proximity to or associated with the automatic shunt trip function wi LL nat degrade this function during or after a seismic event.
The Licensee notes that WOG is performing seismi c qualification tests to demonstrate operabi Lity of the shunt tr ip in accordance with the provisions of ReguLatory Guide 1.100 Revision 1 which en" dorses IEEE Standard 384.
These tests wi Ll be performed on a
generi c system
'and w i LL encompass the Diablo Canyon f eatures.
We f ind this commitment to be acceptable.
2.7 Verify that the components used to accompLish the automatic shunt trip function are designed for the environment where they a re Located.
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The Licensee notes that the components used to accomplish the automatic shunt trip function are designed for the environment where they are Located.
We find this is acceptable.
2.8 Describe the physicaL separation provided between the cir-cuits used to manuaLly initiate the shunt trip attachments of the redundant reactor trip breakers.
Xf physical separa-tion is not maintained between, these circuits~ demonstrate that faults within these circuits cannot degrade both redundant t rains.
The Licensee confirmed that physicaL separation is maintained between redundant trains in the main controL board~ reactor trip switchgear and reactor protection logic for the shunt trip cir-cuitry.
The reactor trip switches on the main controL board have barriers to separate redundant train switch contact decks.
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trip attachments interposing rela~
and their associated terminaL blocks are mounted in separate metal enclosures.
The reactor
~I protection Logic outputs for energizing the shunt trip interposing relays are housed in existing separate metal enclosures.
Physi caL t
separation for field cabling between the redundant trains is main-tained.
We find this meets the requirement of Regulatory Guide 1.75 and i s~ therefore~
a cceptab'Le.
2.9 Verify that'he operability of the reactor trip switch contacts and wi tested prior to sta rtup after each Veri fy that the test procedure used insta L Ling jumpers~
Lifting Leads~
identify any deviations from the WO Ly insta L Led test conne cti ons (i.e.
of a voltmeter) are acceptable.
controL room manuaL ring wiLL be adequately ref ueL ing outage.
wi Ll not involve or pulLing fuses and 6 procedure.
Permanent-to aLLow connection
The Licensee provided a
copy of the test procedure used to veri fy the operabi Lity of the manuaL trip function.
The procedures in-c Lude the use of jumpers to defeat the action of the undervoltage trip attachment to independently verify the operability of the shunt trip attachment.
The continuity of the manuaL reactor trip circuits could be verified by voltage measurements at the terminaL blocks for the reactor trip breakers.
Since this testing could be performed in a manner which would no't require the use of jumpers~
we find that the existing pr'ocedure is unacceptabLe.
The staff requires that the procedure be modified such that the use of jump" ers wiLL not be required to permit verification of the manuaL trip circuits.
The revised procedure should be submitted for staff review.
2.10 Verify that each bypass br eaker wilL be tested to demon-strate its operability'rint to placing it into service for reactor t rip breaker testing.
The Licensee has described the procedure for testing the trip breakers in the FSAR The bypass breaker is closed and tripped to verify its operation.
After its operabiLity is verified it can be reclosed~
and the reactor trip breakers of the same train can be tested.
This is a cceptab Le.
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1 2.11 Verify that the test procedure used to determine reactor trip breaker operabi Lit'y wi L L aLso demonstrate proper operation of the associated controL room indication/
annunciation.
The Licensee notes that the existing test procedures used to de-termine reactor trip breaker operability also demonstrates proper operation of the associated controL room indication/annunciation.-
The red Light indicates that the breaker is cLosed and the green Light indicates that the breaker is open.
We find this is ac-e eptab Le.
2.12 Verify that the response time of the automatic shunt trip feature wiLL be tested periodicaLLy and shown to be Less than or equa'L to that assumed in the FSAR analyses or that specified in We techni ca L specif icat'ions.
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The Licensee has not committed to perf orm the periodi c time re-sponse testing of the automatic shunt trip feature at this time
~I but wiLL re evaluate foLLowing Life cycLe testing under a
WOG pro-gram.
The staff wi LL review this matter following completion of Life. cyc Le testing program.
2.13 Propose technicaL specification changes to require periodic testing of the under voLtage and shunt trip functions and the manuaL reactor trip switch contacts and wiring.
The Li censee notes that a technicaL specification change request wi LL be submitted incorporating the required testing of the reactor trip function.
We find this commitment to be acceptabLe.
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3.0 CONCLUSION
Based on the review of the licensee's response to the plant spe-cific information requests identified in the staff's evaluation of the Owner's Group generic design modifications~
we find the modifi-cations acceptabLe with the foLLowing conditions:
a)
Submission of test procedure used to independently verify operabiLity of the undervoltage and shunt trip device as identified in item 2.4 ~
b)
Confirmation of the seismic qualifi cations of shunt trip attachments and associated circuitry as identified in item 2.6.
c)
Submission of revised test procedure for manua L reactor trip testing as identified in item 2.9.
d)
- e)
Submission c lus i on on Submission to require trip funct and associ of-resuLts of Life cycle test program and con" the need for tests as defined in item 2.12
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of the proposed technicaL specification changes periodic 'test'ing of the undervoLtage and shunt ions~ the manuaL reactor trip switch contacts ated wiring as deFined in item 2.13.
The Licensee shaLL provide'~ prior to exceeding 5 percent of rated power~
a schedule for responding to items a through d.
Finally~
the staff concLudes that the proposed modif ications shaLL be im-pLemented and proposed technicaL specifications (item e above) shaLL be provided for each unit prior to exceeding the 5 percent power Level.
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