ML17157A746
| ML17157A746 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 06/27/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17157A745 | List: |
| References | |
| NUDOCS 9107180041 | |
| Download: ML17157A746 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, O.C. 20556 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.112TO FACILITY OPERATING LICENSE NO. NPF-14 At'.EtIDMENT NO.
81 TO FACILITY OPERATING LICENSE NO. NPF-22 PENtISYLVANIA POWER 8
LIGHT COMPANY ALLEGHENY ELECTRIC COOPERATIVE, INC.
SUSQUEHANNA STEAM ELECTRIC STATIONUNITS 1 AND 2 DOCKET NOS.
50-387 AND 388 1.0 ItITRODUCTION By letter dated
.1uly 27, 1990, Pennsylvania Power and Light Company and Allegheny Electric Cooperative, Inc. (the licensees) submitted a request for changes to the Susquehanna Steam Electric Station, Units 1 and 2, Technical Specifications (TS}.
The requested changes would change the Technical Specifications by requiring that the LOCA/False LOCA interlocks be tested every 18 months and by incorporating language which allows the tests to be successfully completed by any series of sequential, overlapping or total channel steps such that the entire channel is tested.
2.
1.0 BACKGROUND
The licensee is proposing to increase the testing frequency of the LOCA/False LOCA interlocks between the Residual Heat Removal (RHR) and Core Spray (CS) pumps for Susquehanna Steam Electric Station, Units 1
and 2.
The existing Technical Specification requires testing of the RHR and CS pumps on the simultaneous shutdown of the units at an interval not less than five years.
The licensee has determined that the interlocks are an important feature of the Emergency Core Cooling System (ECCS) and should be tested more frequently than required by the existing specification.
Susquehanna is proposing to perform the surveillance every eighteen months using the existing surveillance procedures with some modifications.
The surveillance involves testing the pump interlocks that prevent the overloading of the 4Kv buses and the diesel generators.
The existing Surveillance Procedures would be modified to allow the interlocks to be tested by any series of sequential, overlapping or total channel steps such that the entire channel would be tested.
Under this testing proposal, a dual unit outage would not be required.
To support the proposed changes to the Technical Specifications the licensee submittal includes:
Description of Change, Hazard Evaluation, and the tiarked-up Technical Specification.
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1 2.2 DISCUSSION AND EVALUATION The staff has evaluated the Susquehanna Units 1 and 2 proposal in the following major areas:
Pump interlock Basis - The original technical basis of the interlocks must not change.
Shared Diesel Generator - Sufficient diesel capacity must exist to service accident conditions in both units.
LOCA/False LOCA Signal - The difference between a real LOCA condition and a false LOCA signal must be made.
Surveillance Procedures
- Changes to existing procedures must not be too extensive to alter procedures'bjectives.
The RHR System and the CS System are powered from 4Kv buses.
Power to the 4Kv buses comes from offsite sources or from onsite sources by the standby diesel generators.
Each unit has four RHR pumps, two of which are preferred pumps.
Each unit has four CS pumps, two of which are also preferred pumps.
The interlocks implemented by relays and relay contacts are provided between corresponding RHR and CS pumps in Susquehanna Unit 1 and Unit 2.
The interlocks prevent two corresponding RHR and CS pumps from operating at the same time.
Operating only one corresponding RHR and CS pump at a time protects against overloading the 4Kv buses and overloading the diesel generators
'in the event of a loss of offsite power (LOOP).
When a
LOCA occurs in one unit, with no other abnormal conditions in the non-LOCA unit, all eioht pumps are started.
When a
LOCA occurs in one unit and a LOCA/False LOCA occurs in the other unit, only the preferred pumps from each unit would be running.
Under this condition, the non-preferred pumps would be tripped.
To accomplish this the proper bus loading and shedding is preformed by the system logic.
Technical Specification 4.5.1.e requires that the RHR and CS pumps be tested during the first simultaneous shutdown (Units 1 and 2) of duration greater than 7 days occurring more than five years following the previous testing.
As written, testing may not occur at all in five years if there is not a dual unit outage of significant length.
In evaluating the need to test th'ese interlocks, Susquehanna examined twelve surveillance procedures for the RHR System, CS
'ystem, and the Diesel Generators and determined that with the exception of a few relays and contacts, the interlocks associated with the Technical Specification Surveillance 4.5.1.e were being tested periodically (18 months).
Subsequent to thi s evaluation, eight of the twelve survei llances were revised to include the additional relays and contacts.
This testing is accomplished by permitting the tests to be successfully completed by any series of sequential, overlapping or total channel steps such that the entire channel is tested.
The staff has concluded that with the modified changes, Technical Specification Surveillance 4.5.1.e is being met every 18 months.
4 ef The sharing of diesel generators is governed by 10 CFR 50, Appendix A, General Design Criterion 5.
GDC 5 requires that the design assume the event of an accident in one unit, and an orderly shutdown and cooldown of the other unit.
10 CFP. 50, Appendix A, General Design Criterion 1? requires an onsite electric power system and an offsite electr ic power system such that each electrical system provides sufficient capacity to accomplish the safety functions.
The Susquehanna submittals provide sufficient information to conclude that both GDC 5 and GDC 1? would still be met with the new testing frequency.
Three different indications can occur in a LOCA
- (1)
Low reactor water level, (2)
Low reactor
- pressure, and (3) High drywell pressure.
Any combination of two of these signals energizes relays in the Residual Heat Removal and Core Spray Systems.
To the plant initially, both signals are identical.
- However, a false LOCA signal is an injection of a LOCA signal into the non-accident unit ECCS logic when a
LOCA in reality does not exist.
Susouehanna system logic does not automatically identify a real LOCA from a false LOCA.
The Control Room operators manually validate or refute the LOCA signals by utilizing the three LOCA parameter indications.
Distinction between a real and false LOCA is necessary to optimize the handling of an accident.
The staff has reviewed the existing twelve surveillance procedures with the required markups.
The procedures are the 18 month surveillances performed on the RHR
- System, CS System, and the Diesel Generators.
In summary the procedures:
1.
Call for system and logic system functional checks of the RHR Divisions 1 and 2; 2.
Call for CS System logic functional check of Loops A & 8 and Divisions 1 and 2; and 3.
Call for checking the Diesel Generator automatic start and sequence logic for bus energizing
& load shedding.
The procedures denote where the changes are made to the text.
The changes to the existing procedures are minor and do incorporate the words to be able to test the interlocks every 18 months.
Each procedure checks only a piece of the loop which combined with the rest of the procedures tests the total system loop. It is preferred that testing of the entire loop be performed in one complete sequence.
However, testing by a series of sequential and overlapping steps is an acceptable method.
2.3 EVALUATION
SUMMARY
Susquehanna has proposed increasing the surveillance test frequency for the LOCA/False pump interlocks to once every eighteen months.
This proposal involves changing Technical Specification 4.5.1.e.
The RHR and CS pump interlocks prevent the overloading of the 4Kv buses and diesel generators in a LOOP.
The original interlock basis remains the same and is not impacted by the more frequent testing.
I
4 Our regulations at 10 CFR 50 require at that an onsite and an offsite electrical source be provided to service the safety system functions.
Susquehanna meets the regulations by providing adequate cooling capacity to both units simultaneously in normal and accident conditions.
The system logic is unable to distinguish between a true LOCA and a false LOCA.
This distinction is necessary to optimize handling of the accident conditions.
- however, the operator has the necessary indications to determine the true LOCA conditions.
The existing surveillance procedures are modified to enable testing the complete interlock channels every eighteen months.
Changes have been made to the
- RHR, CS, and diesel generators surveillance procedures to include the interlock relays and relay contacts to test in pieces the entire channel.
The functional testing of the interlocks by the series of sequential and over lapping steps is acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments.
The State official had no comments.
- 4. 0 ENVIRONMENTAL CONSIDERATION The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changed surveillance requirements.
The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a
proposed finding that the amendments involve no significant hazards consideration, and, there has been no public corn'ment on such finding.
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed
- above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed
- manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
J. Ibarra Date: gune 27, 1991
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