ML20154M220
| ML20154M220 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/07/1986 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20154M219 | List: |
| References | |
| GL-83-28, NUDOCS 8603130383 | |
| Download: ML20154M220 (10) | |
Text
ENCLOSURE 3 SAFETY EVAI.UATION REPORT DOCKET NO. 50-498/499 SOUTP TEXA5 UNIT 5 I & 2 GENERIC LEIILR 83 28 ITEM 4.3 REACTOR TRIP BREAKER AUTOMATIC SPUNT TRIP INTRODUCTION AND
SUMMARY
Generic letter 83-28 was issued by NRC on July 8, 1983 indicating actions to be taken by applicants based on the generic implication 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 actuation of the shunt attachment on the reactor trip breakers.
By letter dated October 14, 1985, Houston 1.ighting and Power Company provided responses to the plant specific questions identified by the staff in its August 10, 1983, safety evaluation report of the generic Westinghouse design.
The staff has reviewed the applicant's proposed design for the automatic actuation of the reactor trip breaker shunt trip attachments and finds it acceptable.
The applicant has specified the implementation for these modifications to be completed prior to fuel load.
8603130393 860307 PDR ADOCM 05000498 A
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EVALUATION The followino required plant specific information items were identified based on the staff's review of the WOG prnposed caneric desian for this modificatica:
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Provide the electrical schematic / elementary diaarams for the reactor trio and bypass breakers showing the underynitage and shunt coil
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actuation circuits as well as the breaker control (e.a., closing) i circuits, and circuits providing breaker status information/ alarms to l
the control ronm.
i The applicant provided the electrical schamatic diagrams for the reactor trip and bypass breakers showing the underynitaae and the shunt trio circuits. The design of the electrical circuits have been reviewed and found to be consistent with the WOG generic proposed desian which was nreviousiv reviewed and approved J
by the staff. We find this is acceptable.
i 2.
Identify the power sources for the shunt trio coils. Verify that they are Class IE and that all enmonnents providino power to the shunt trip circuitry are Class IE and that any faults within nnn-class IE circuitry will not degrade the shunt trio function. Describe the annunciation /
indication provided in tha control room upon Inss of power to the shunt trip circuits. Also describe the overvoltaqe protection and/or alarms
3-provided to prevent or alert the operator (sl to an nyerynitaqa condition that could affect both the llV coil and the parallal shunt trio actuatinn relay.
Redundant Class IE power sourcas are used for the shunt trip actuation of the reactor trip breakers and for the shunt trip of the bvo6ss breakers. Class IE circuitry is separated from non-lE circuitrv. Therefore, credible faults within non-Class IE circuitry will not degrade the shunt trip function. This is in accordance with Regulatory Guide 1.75 and is, therefore, acceptable.
The breaker position status lights are used tn supervise the availability of power to the shunt trip circuits. The red light which is connectad in series with the shunt coil and the "a" auxiliary contact indicates that tha breaker is closed and also indicates that the onwar is available to the shunt trip device and, therefore provides detectability of power failure to the shunt trin coil.
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 (aporox.
50 ma) flows through the trip coil to monitor the circuit continuity which is not large enough to actuate the trip coil armature. Since the current through the shunt trip coils is interrupted when the breaker trips, eneraization of the shunt trio coil is only momentarv. The maximum available voltage occurs during a battery equalizino charge at a maximum voltaae of 115% of the nominal voltage. Due to the short duty cycle of the shunt trip cnil, it can operata at this overvoltaae condition without harmful effects.
The added shunt trip circuitry is powered from the reactor protection logic voltage supply (48 Vde).
Components in the added shunt trip circuitry have been selected based on their ability to perform their intended function up to 115% of nominal voltage.
The reactor protection logic voltage is provided with overvoltage protection set at 115% of nominal voltace.
Based on our review, we conclude that appropriate consideration has been given to the aspects of the design described above and the design is, therefore, acceptable.
3.
Verifv that the relays added for the autenatic shunt trip functinn ara within the capacity of their associated onwer sunplies and that the relay contacts are adequately sized to acenmolish the shunt trio function.
If the added relays are other than the Potter A Brunfield MDP series relays (P/N ?381A18 nr P/N 955655) recommandad by Westinahousa, provida a description of tha ralavs and their design specifications.
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I The added relays for the automatic trip function are Potter and Rrumfield MOD series relays P/N 955655. Westinahouse has verified that the relav contacts are adequately sized for the shunt trip function and are within the capacity l
of their associated power suoplies. We find this to be acceptable.
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4 State whether the test procedure / sequence used to independent 1v verify f
operability of the undervoltage and shunt trip devices in response to an automatic reactor trio signal is identical to the test procedure proposed i
by the Westinghouse Owners Group (WOG).
Identify any differences batween the WOG test procedure and the test procedure to be used and orovide the i
rationale /.iustification for these differences, j
The applicant states that the test orneadures used tn independentiv verifv f
operability of the UV and shunt trin d* vices will be written and in place prior to fuel load. The procedures submitted by the WOG will be referenced durinq l
the development of its procedures. No major deviations from the WOG prnreduras are anticipated. We find this commitment to be acceptable.
l 5.
Verify that the circuitry used to implement the automatic shunt trip function is Class 1E (safety related), and that the procuremant, in-sta11ation, operation, testino and maintenance of this circuitry will I
be in accordance with the quality assurance criteria set forth in l
Appendir B to 10 CFR Part 50.
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The applicant confirmed that the circuitry used tn implemant the automatic shunt trip function is Class IE (safety related1 and the procurement, installation, I
i operation, testina and maintenance of this circuitry will be in accordance with the Westinghouse and South Texas oro.iect quality assurance procedures wh'ch i
satisfy the quality assurance reauirements of Appendix 8 tn 10 CFR Part 50.
We find this to be acceptable.
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6.
Verify that the shunt trip attachments and associated circuitry are/will 1
i be seismically qualified (i.e., be demonstrated to be operable durino and I
after a seismic event) in accordance with the provisions of Requiatory l
Guide 1.100, Revision I which endorses IEEE Standard 344, and that all j
non-safety related circuitry / components in physical proximity to or i
i associated with the automatic shunt trip function will not dearade this l
function during or after a seismic event.
The applicant states that all components of the shunt trio and associatad cir-cuitry are incorporated within the reactor trip switchoaar cabinets and ara seismically qualified. We find this to be acceptable.
7.
Verify that the components used tn accomplish the automatic shunt trip function are desianed for the environmant where thav are locatad.
The applicant notes that the components used to acenmplish the automatic shun *.
trip function are designed for the environment where they are located. We find this to be acceptable.
8.
Describe the physical separation provided between the circuits used to manually initiate the shunt trip attachments of the redundant reactor trip breakers.
If physical separation is not maintained batween these circuits, demonstrate that faults within these circuits cannnt dearade both redundant trains.
The apo11 cant confirmed that physical separation is maintained between re-dundant trains in the main control board, reactor trio switchaear and reactor protection logic for the shunt trip circuitry. Dual section minual reactor trip switches, with metal barriers between redundant train decks, are provided on the main control board.
Shunt trip attachments interonsino relays and their associated terminal blocks are mounted in separate matal enclosures.
The reactor protection logic outouts for Preralzina the shunt trip interposino relays are housed in existing separate metal enclosures.
Physical separation for field cabling between the redundant trains is maintained. We find this meets the requirement of Reculatory Guide 1.75 and is, therafora, acceptable.
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9.
Verify that the operability of the control room manual reactor trip switch contacts and wirino will be adequately tested prior to startup after each refueling outaae. Verify that the test procedure used will not involve installina jumpers, liftina leads, or pullino fuses and identify any deviations from the WOG procedure. Permanentiv installed test connections (i.e., to allow connection of a voltmeter) are acceptable.
The applicant states that the test procedures will be written to verify the operability of control room manual reactor trip switch contacts and wirino prior to startup after each refueling outaae. The test procedures will not involve installina jumpers, lifting leads, or pulling fuses. We find this to be acceptable.
10 Verify that each bypass breaker will be tested to demonstrate its oper-ability prior to placino it into service for reactor trip breaker testino.
The applicant states that the Technical Specifications were revised to include testing of the bypass breaker prior to placino it into service for reactor trip breaker testing. We find this to be acceptable.
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- 11. Verify that the test procedure used to determine reactor trip breaker operability will also demonstrate proper operation of the associated control room indication / annunciation.
The applicant notes that the revised test procedures used to determina reactor trio breaker operability will demonstrate proper operat, inn of the associated control room indication /annunciatin.1 We find this to be acceptable.
- 12. Verify that the response time of the automatic shunt trip feature will he tested periodically and shown to be less than or eoual to that assumed in the FSAR analyses or that specified in the technical specificatinns.
The applicant state; that Westinghouse has prepared a report of the reactor trip breaker UVTA and STA life cycle test which concludes that periodic testino for STA can be limited to verifying that it can trip the breaker with 70 Vdc (mini-mum design voltagal. Tharefore, perindic testino of the automatic shunt trio feature response time is not required. We find this to be acceptable.
- 13. Propose technical specification chances to require perindic tastinq of tha undarvoltage and shunt trip functinns and tha manual reactor trip switch contacts and wirino.
The applicant has submitted the proposed Technical Specification chances to require periodic testing of the undarvoltaan and shunt trip functions and the
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manual reactor trio switch contacts and wirina. We find this to be in accord-l ance with G.L. 85-09 and is therefore, acceptable. However, the apolicant has added ACTION 11 to Table 3.3-1 but failed to reference it in item No.19.
Therefore, it is required that the apolicant add ACTION 11 to item No. 19 of l
Table 3.3-1.
1 CONCLUSION l
Based on the review of the licensee's response to the plant specific Questions identified in the staff's evaluation of the Owner's Group generic design modifications, we find that the modifications are acceptable.
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