ML15223A925
| ML15223A925 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/12/1983 |
| From: | Stolz J Office of Nuclear Reactor Regulation |
| To: | Tucker H DUKE POWER CO. |
| References | |
| GL-83-28, NUDOCS 8310040647 | |
| Download: ML15223A925 (16) | |
Text
DISTRIBUTION oc et F' RIngram NRC PTR JSuermann Dockets Nos. 50-269, 50-270 L PDR Gray File+4 and 50-287 ORB #4 Rdg 01 DEisenhut e
OELD CMiles LHarmon Mr. H. B. TuckerACS1 Vice President - Steam Production ACRS-1 2
TBarnhart-12 Duke Power Company Eordan P. 0. Box 33189 JTaylor 422 South Church Street WJones Charlotte, North.Carolina 28242 DBrinkman
Dear Mr. Tucker:
RDiggs By letter dated June 7, 1983, Arkansas Power and Light Company (AP&L) provided a description of proposed modifications of the reactor trip system to include automatic actuation of the shunt trip feature for the reactor trip breakers.
Earlier, by letter dated May 27, 1983, from Mr. E. G. Wallace, Chairman, B&W Owners Group Steering Committee to Mr. D. G. Eisenhut, the B&I Owners Group endorsed the AR&L shunt trip design approach for B&W facilities.
We have reviewed the AP&L design for Arkansas Nuclear One, Unit No. 1.
As a result of that review, we have prepared the enclosed Safety Evaluation Report (SER) which addresses the generic aspects of this design and sum marizes, in Enclosure 1, the information required to conclude the review of this matter on a plant specific basis.
When you do indeed endorse or submit the generic aspect of the AP&L design for application to your plant in response to Generic Letter 83-28 dated July 8, 1983, we request that you also provide the information identified in Enclosure 1 of the enclosed SER.
The reporting and/or recordkeeping requirements of this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.
Sincerely, Vli G MLAL SI G1RED BY JOHIN F. STOhZ B310040647 830912 PDR ADOCK 05000269 PDR DOCK0500269John F. Stolz, Chief
_P PDR Operating Reactors Branch #4 Division of Licensing
Enclosures:
As Stated cc w/enclosures-:
See next page OFFICE
- RB/4 L
- 4:.B..L............
suRNAME~ Surn; l
ing PKadambi SURN E0.. ur...n DATE
/1783 9
83 9/12-/83 NRC FORM 318(10/80 NRCM 0240 OFFICIAL RECORD COPY u.S. GPO 1983-400-241
Duke Power Company cc w/enclosure(s):
Mr. William L. Porter Duke Power Company P. 0. Box 33189 422 South Church Street Office of Intergovernmental Relations Charlotte, North Carolina 28242 116 West Jones Street Raleigh, North Carolina 27603 Honorable James M. Phinney County Supervisor of Oconee County Walhalla, South Carolina 29621 Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission, Region II 101 Marietta Street, 1W, Suite '2900 Atlanta, Georgia -30303 Heyward G. Shealy, Chief Bureau of Radiological Health South Carolina Department of Health and Environmental' Control 2600 Bull Street Reqional Radiation Representative Colubia, South Carolina 29201 EPA Region IV 345 Courtland Street, N.E.
Atlanta, Georgia 30308 Mr. J. C. Bryant Senior Resident Inspector U.S. Nuclear Regulatory Commission Route 2, Box 610 Seneca, South Carolina 29678 Mr. Robert B. Borsum Babcock & Wilcox Nuclear Power Generation Division Suite 220, 7910 Woodmont Avenue Bethesda, Maryland 20814 Manager, LIS NUS Corporation 2536 Countryside Boulevard Clearwater, Florida 33515 J. Michael McGarry, III, Esq.
DeBevoise & Liberman 1200 17th Street, N.W.
Washington, D. C. 20036
K S.
SAFETY EVALUATION REPORT GENERIC MODIFICATIONS OF REACTOR TRIP BREAKERS FOR B&W PLANTS TO PROVIDE AUTOMATIC ACTUATION OF SHUNT TRIP ATTACHMENTS INTRODUCTION AND
SUMMARY
By Letter dated May 27, 1983, from E. G. WaLLace, Chairman, B&W Owners Group Steering Committee to D. G. Eisenhut, Director of Licensing, NRR, it was indicated that the B&W Owners Group had conducted a review of the AP&L shunt trip design and has endorsed the proposed AP&L design as a generic approach for B&W facilities.
By Letter dated June 7, 1983, Arkansas Power and Light (AP&L) Company pro posed modifications of the reactor trip system for Arkansas NucLear One Unit 1 (ANO-1), to provide automatic actuation of the shunt trip attachments for the reactor trip breakers.
This modification was proposed as a backup to the existing undervoLtage (UV) trip capability to enhance the overaLL reLiabiLity of the reactor trip system on either an automatic or manuaLLy initiated trip command.
Subsequently on JuLy 8, 1983, NRC issued Generic Letter 83-28 identifying actions required by aLL reactor Licensees and appLicants based on generic impLications of the SaLem ATWS events.
Item 4.3 of the generic Letter estabLished the requirement that B&W plants be modified to provide reactor trip system actuation of the breaker shunt trip attachments.
This safety evalu ation report provides the staff's concLusions based on its review of the generic aspects of the AP&L design consistent with the pre-impLementation review of modifications as re quired by Generic Letter 83-28.
- 2 In summary, the staff finds the generic aspects of the AP&L design to provide an automatic shunt trip to be acceptable.
There are, however, a number of plant specific aspects associ ated with the design that were not addressed in the AP&L proposed modification and wiLl be subject to staff review on a plant.specific basis.
The information required to permit review and approval of the pLant specific aspects of this modification for aLL B&W plants incLuding ANO-1 are identified in EncLosure 1 to this evaLuation.
DISCUSSION:
The design of the B&W reactor trip systems is discussed in detaiL in Section 3.1.2.4 of NUREG-1000, VoLume 1, "Generic ImpLementation of ATWS Events at the SaLem NucLear Power PLant".
Figures 3.4 and 3.5 of NUREG-1000 are incLuded here in as Figures 1 and 2 respectiveLy to facilitate an understand ing of the shunt trip modifications as genericaLly appLicabLe to the two basic configurations of B&W reactor trip system designs.
The generic feature of the AP&L proposed modification to pro vide automatic actuation of the shunt trip attachments for the reactor trip breakers is the addition of a soLid state under voLtage sensing device to the reactor trip system circuits.
The undervoLtage sensor is wired to monitor the voLtage across
-3 the coiL of the undervoltage trip attachment and an output reLay contact of the undervoLtage sensor is used to energize the coil of the shunt trip attachment.
Thus when power is re moved from the breaker undervoLtage trip attachment on either a manual or automatic trip command, the shunt trip attachment wiLL be energized to provide an additionaL means to assure that the breaker is tripped.
Schematically, these modifications are shown on Figures 3 and 4. Figure 3 shows the trip circuit for the AC circuit breakers shown on Figures 1 and 2. Figure 4 shows the trip circuits for the DC circuit breakers shown on Figure 1.
Test switches are incLuded in the circuit modifications to permit independent testing of the shunt and undervoLtage trip attachments. -Indicating Lights are included to faciLitate testing and a relay is provided to aLarm a Loss of the dc power used to energize the shunt trip attachment.
EVALUATION The undervoltage sensor used in the ANO-1 proposed modification is a Brown Boveri Electric Inc. ModeL ITE-27H-211R high speed undervoLtage reLay.
This component has been environmentaLLy and seismically quaLified for its required service conditions in
accordance to IEEE Standards 323-1974 and 344-1971 respectively.
In addition the equipment was seismicalLy qualified in accord ance to IEEE Standard 501-1978 for a test response spectrum with a ZPA (zero period acceLeration) Level of 6 g's.
In addi tion each reLay is tested Line-to-Line and Line-to-ground be fore shipment to satisfy the dieLectric test requirements of IEEE Standard 313 and surge withstand capability requirements of IEEE 472.
As required by these standards the tests were performed at 1500 and 2500 volts respectiveLy with the reLay operating at normaL voltage and temperature. Therefore, based on the documentation of the qualifications of the undervoltage sensors incLuded in the AP&L proposaL, the staff finds that the qualification of this device is acceptable for this appli cation.
For plants other than AP&L, applicants and Licensees shouLd.confirm that the qualified service conditions enveLop the pLant specific conditions of service.
As noted in Figures 3 and 4 the undervoLtage sensors require a source of 125 Vdc power to operate the soLid state under voLtage sensing circuits and to maintain its output reLay in an energized state when the voltage appLied to the UV coil of the reactor trip breaker is at its nominal vaLue.
On sensing that voltage to the UV trip coil has been removed by either a manuaL or automatic reactor trip condition, the output reLay of the UV sensor is deenergized.
A normaLLy closed contact
(cLosed when the reLay is deenergized) is used to energize the shunt trip coil to trip the reactor trip breaker(s) and thereby remove power from the controL rods.
In the ANO-1 design the AC circuit breakers include a feature to actuate the shunt trip on sensing an under voLtage condi tion on the suppLy bus for the controL rod system.
The AP&L proposaL did not address the cLassification nor the separation of the wiring associated with these existing shunt trip cir cuits.
The Licensee wiLL be required to confirm that these circuits are cLassified and separated in accordance with the requirements of safety reLated circuits or that a qualified isoLation device wiLL be incorporated such that the circuit separation and cLassification is maintained to assure the re quired independence of these circuits.
Further, the AP&L pro posaL did not address the seismic cLassification of the shunt trip attachment and added trip circuit components other than the UV sensor.
As required by Generic Letter 83-28, the modifi cation is to be cLassified as safety reLated.
Therefore, Licensees and appLicants, including AP&L wiLL be required to confirm that the shunt trip attachment and the added trip cir cuit components are or wiLL be seismically quaLified.
Seismic qualification, if not performed, may be completed at a Later date and is not a prerequsite to implementation of this modifi cation.
GenericaLLy this wiLL apply to aLL B&W plants.
- -6 The ANO-1 shunt trip circuit design for the AC breakers as shown on Figure 3 incLudes a 30 amp fuse on both sides of the shunt trip coiL.
In that this fuse arrangement is not included in the proposed shunt trip circuit for the DC breakers shown on Figure 4, it is expected that this circuit protection is not required.
Since the faiLure of either 30.amp fuse would render the shunt trip inoperabLe and wouLd not be detected by the Loss of power alarm included in the proposed modification, the staff concLudes that these fuses do not enhance the reLiabiLity of the shunt trip function and therefore shouLd be removed.
Further, in that no other circuit protection was shown nor was the cLassification or separation of the dc circuits addressed in the proposed modification, this is an aspect of the design which the staff wiLL require aLL Licensees and applicants, incLuding AP&L to address on a pLant specific basis.
The DC breaker trip circuits shown on Figure 4 invoLve differ ent trains of Logic and power supplies for the UV and shunt trip circuits.
The UV trip circuit invoLves train "C " of the protection system while the shunt trip utilizes the train "A" DC power source.
This Leads to some difficuLty in maintaining adequate separation of the train "A" and train "C" wiring in the trip breaker cabinets and particularly at the UV sensor.
From the manufacturers Literature submitted with the AP&L pro posal, it is seen that the monitored voLtage input is on the
-7 same terminaL strip as output reLay contacts and the DC power supply.
The staff questions whether the physical separation of the different trains of wiring can be adequateLy maintained at the undervoLtage sensor.
Therefore, the staff wiLL require that Licensees and appLicants including AP&L address the cLassification and separation of the shunt and UV trip circuits and the measures taken to maintain adequate separation between different trains of the trip circuits.
With regard to the undervoLtage sensor, the staff wiLL require an analysis of potentiaL shorts between redundant train wiring or the instaL Lation of a quaLified isoLation device, such as a fused input one to one transformer, which would permit reasonable separa tion of wiring for different trains of the trip circuits.
For Davis Besse and B&W applicants, similar probLems may exist with regard to train "C" and "D" for the DC breaker trip circuits shown on Figure 3. These circuits are not applicabLe to the AP&L proposaL and the cLassification and separation of dc power sources to be used with trains "C" and "D" of the DC trip breaker circuits have not been defined.
The staff wiLL require that this matter be addressed on a pLant specific basis.
The staff concludes that the test features provided wiLL per mit independent testing of the operability of the shunt and UV trip features of the reactor trip breakers.
The B&W reactor trip system does not involve speciaL consideration with regard to manual trip testing that have been encountered in the review of other reactor vendor designs.
Therefore this has not been
an area of concern in this review.
However, with regard to testing, a procedure has not been proposed for the conduct of tests to demonstrate the operabiLity of the reactor trip breakers and the trip circuits.
The staff wiLL require aLL B&W plants to submit the test procedures for review.
Further as noted in Generic Letter 83-28, any needed technicaL specification change requests are to be submitted prior to de cLaring the system operable.
These aspects wiLL be reviewed on a plant specific basis.
The staff notes that the power faiLure alarm reLay incorpor ated in the shunt trip circuit of Figure 3 differs from that of Figure 4. In Figure 4 the power failure alarm relay wiLL be deenergized any time test switch #2 is operated, while in Figure 3 it onLy operates on removaL of power from the shunt trip circuit.
The AP&L proposaL did not address this differ ence nor is the basis for this difference cLear.
With regard to the alarm reLay, the staff notes that there may be some benefit to the design as shown on Figure 4 since test switch
- 2 provides a convenient means to verify the operability of the alarm circuit.
On the other hand some Licensees or applicants may concLude that this design may result in unnecessary aLarms during testing and may prefer to connect the power aLarm reLay as shown in Figure 3.
With regard to this matter the staff finds either method for connecting the power alarm reLay accept able.
However, if the configuration as shown in Figure 3 is
used, the operabiLity of the aLarm circuit shouLd be checked periodicaLLy on a refueLing outage interval.
ALL plants should address their intent to confirm the operability of this aLarm circuit.
The AP&L proposaL did not incLude marked up eLectrical sche matics of the proposed modifications but rather simpLified sketches typical of Figures 3 and 4 herein.
EarLier proposaLs of this modification were inadequate in that they did not show aLL components and circuit connections invoLved with these cir cuits.
On a plant specific basis, the staff wiLL require actuZ.L pLant eLectricaL schematics of the trip circuit modifications.
CONCLUSION Based on review of the AP&L proposaL to incorporate the auto matic shunt trip of the reactor trip breakers, the staff con cLudes that the generic aspects of this design are acceptable.
Those matters to be addressed on a plant specific basis to permit resolution of the aspects of the design which wiLL re quire further staff review are summarized in EncLosure 1 of this evaLuation.
These matters wiLL be addressed on a plant specific basis and an evaluation wiLL be issued by the staff for finaL design and implementation approval.
Dated: September 12, 1983.
The following NRC personnel have contributed to this Safety Evaluation:
T. Dunning
ALL POWER SOURCES FOR A PLANf PROCESS GIVEN ROD GROUP MUST BE INSTRUMENT CHANNELS INTERRUPTED IN ORDER FOR ISENSORS AND A
THE RODS IN THAT GROUP TRANSMITTERS.
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MANUAL TRIP -- ---------- -----
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0 CONTROL POWER A
SCR SECONDARY AC TRIP CONTROL POWER BREAKERS 8 HO DN HOLDING POWER TO REGULATING
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CROCS PLANT PROCESS (CONTROL ROD DRIVE CONTROL SYSTEMI INSTRUMENT CHANNELS ISENSORS AND A
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AC TRIP MANUAL TRIP 2---
HOLDING REAKERS POWER To ALL ROD
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6CR MAIN CONTROL POWER
&CA SECONDARY CONTROL POWER I
II I.
DC D
C DC DC D
C DC 0
ALL POWER SOURCES GIVEN ROD GROUP M INTERRUPTED IN ORDE THE MODS IN THAT OR t0 DROP INTO THE CON SILICON O R O U P 1 R O U P 2
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GU L A T IN G O D S R E L A Y S IUNDEtVOL1AGE TRIP ATTACHMENT Figures 2 Babcock it Wilcox Reactor Trip System (Davia-Besse
UV-.
PRIOOSED UVSESN.0 INA" ARIP PTRIP SNSING A
SWITCH EtTEST CKT 1
A B8 A
c 10 AMTEST SW 1 TRAI "A"
2V UV SENSO A C '
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C COIL B
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UV-TRIP CIRCUIT EXISTING PROPOSED AUTO SHUNT TRIP SHUNT TRIP
& TEST/ALARM CKT TEST SW #2 TRIP
--CONTACT v
I UV SENSOR I
L J
930 AMPL RL TRA 4"A" FUSE 125V DC POWER ALARM RELAY SHUNT RELAY TRIP IND COIL LIGHT #2 30 AMP FUSE SHUNT TRIP CIRCUIT
- "C" "D" TRANS USED ONLY ON DAVIS BESSIE AND B & W APPLICANT. ALL EARLIER PLANTS USE DC SKRS (SEE FIG 41 Figure 3 B&W AC Breaker Trip Circuits(Train "A" Shown, Typical for Train "B", "C", "D")
MAAL PROPOSED R
STRIP UVTI 2V SENSING A IN " C" SW B KRS 1 &2 U TEET NK A
F' D
10 10 TEST SW #1 AMP AMP TRAIN "C" 120V AC SENSOR BKRl BKR2 TRIP TRIP LIGHT #1 A
C COIL COIL B
D UV TRIP CIRCUIT PROPOSED AUTO SHUNT TRIP TEST/ALARM CKT U TEST SW #2 1
I I
I UV SENSOR I
Uv POWER I
I I SENSOR TRAIN A 125V DC POWER 72 72 ALARM a
a IND RELAY LIGHT #2 BKRI BKR2 SHUNT SHUNT TRIP TRIP COIL COIL SHUNT TRIP CIRCUIT
- NOT APPUCABLE ON DAVIS BESSIE AND B&W APPUCANTS Figure 4 BOW DC Breaker Trip Circuits* (Train "C" Shown, Typical for Train "D")
ENCLOSURE 1 INFORMATION REQUIRED ON A PLANT SPECIFIC BASIS FOR REVIEW AND STAFF APPROVAL OF MODIFICATIONS TO PROVIDE AUTOMATIC ACTUATION OF REACTOR TRIP BREAKER SHUNT TRIP ATTACHMENTS
- 1. A statement confirming that the UV sensor (high speed undervoLtage reLay)
ModeL ITE-27H-211R, is environment ally and seismically qualified for its service condi t ions.
- 2.
A statement confirming that aLL other additionaL com ponents invoLved in the shunt trip circuits are environ mentally and seismically qualified for their service conditions.
- 3.
A statement confirming that the shunt trip attachment is or wiLL be environmentaLLy and seismically quaLified for its service conditions.
- 4.
Identify the cLassification (safety reLated or not) and separation (train or channeL identification) for the re actor trip shunt and UV trip circuits, power suppLies, and any interface isoLation devices.
- 5.
If the wiring to the UV sensor invoLves different separ ation groups (train or channeL) identify the minimum separation (distance) between wiring of the different groups.
Provide an analysis of the consequences of short circuits between wiring in different separation groups to confirm that the consequences do not adversely impact redundant safety related systems.
- 6. Provide an outLine of the test procedures to independently verify the operability of the shunt and UV trip circuits and components.
Identify the sequence of actions to be performed.
Address your intent regarding periodic surveit Lance to confirm the operabiLity of the power faiLure alarms.
- 7.
Provide a draft of any proposed technicaL specification changes as a resuLt of this modification.
- 8.
Provide the eLectricaL schematics for the shunt and UV trip circuits.