ML19353A872
| ML19353A872 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/21/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19353A868 | List: |
| References | |
| NUDOCS 8912080023 | |
| Download: ML19353A872 (7) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION-
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WASHINGTON, D. C. 20b55
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED.T0 AMENDMENT N0. 80. TO FACILITY OPERATING LICENSE NO. NPF-10 AND AMENDMENT.NO. 68 - T0. FACILITY OPERATING LICENSE NO. NPF-15 SOUTHERN' CALIFORNIA EDISON COMPANY SAN DIEGO. GAS-AND ELECTRIC COMPANY THE CITY OF RIVERSIDE, CALIFORNIA THE CITY OF. ANAHEIM CALIFORNIA SAN ON0FRE NUCLEAR GENERATING STATION, UNITS 2 AND.3 DOCKET N05. 50-361 AND 50-362
1.0 INTRODUCTION
By letters dated April 26,1988(PCN-248), April 26,1988(PCN-251)and December 19,1988(PCN-282),SouthernCaliforniaEdisonCompany(SCE),et al., (the licensee) requested changes to the Technical. Specifications for -
Facility Operating Licenses No. NPF-10 and No. NPF-15 that authorize operation of San Onofre Nuclear Generating Station (SONGS), Units 2 and 3 in San Diego County, California. These requests proposed to extend the interval for certain of the required 18 month surveillance tests in order to~ support the nominal 24 month fuel cycle.
Both Units 2 and 3 are operating in their first such cycle and will be forced to shut down to perform the 18 month surveillance unless the required interval is extended.
SCE has submitted proposed changes to cover all the'18 month surveillance tests which cannot be performed during plant operation. Many of these requests would have changed the required interval from "at least once every 18 months" to "at least once per refueling interval." The Staff under-took its evaluation based on the understanding that the " refueling interval" was to be 24 months. Therefore, at the Staff's suggestion, by letter dated March 20, 1989, SCE amended these requests to define " refueling interval" ds 24 months.
This definition has been included in the Frequency Notation Table of the Technical Specifications (Table 1.2) by Amendments 73 and 61 to Licenses No. NPF-10 and No. NPF-15 respectively.
2.0 EVALUATION 2.1 PCN 248 By letter dated April 26, 1988, the licensee proposed a change that would revise Technical Specification (TS) 3/4.3.1, " Reactor Protective Instrumentation." TS 3/4.3.1 defines the number of channels of instrumentation required to be operable for each reactor trip functional unit, periodic surveillance tests to verify operability, and action to be taken if the minimum operability requirements are not met. TS 3/4.3.1 C912000023 891121 PDR ADOCK 05000361
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2 ensures that the various functional units of the reactor protective instrumentation will detect abnormal conditions and initiate a reactor trip to. mitigate the consequences of transients and accidents, consistent with the assumptions of the safety analyses.
Two of the functional units covered by TS 3/4.3.1 are the Core Protection Calculators (CPC) and the Control Element Assembly Calculators (CEAC).
Each of the four CPC channels monitor a number of process parameters and calculate departure from nucleate boiling ratio (DNBR) and local power density (LPD).
If any two CPC's detect the onset of a condition where
~i the specified acceptable fuel design limits for DNBR or LPD could be exceeded, a reactor trip will occur.
One of the parameters monitored by the CPC's and used in the calculation of DNBR and LPD is control element assembly (CEA) position. There are 91 CEA's each with two reed switch position transmitter (RSPT) stacks, each RSPT stack associated with one of four instrumentation channels. Thus, for a given CEA, position information can directly be provided to only the two CPC's in the same
. channels as the RSPT stacks if electrical separation between the four channels is to be maintained.
Electrical separation of the four instrumentation channels is important from a reliability standpoint and to minimize the potential for common mode failures of the reactor protection system.
Consequently, e6ch CPC channel directly receives position information for only 23 " target" CEA's from RSPT stacks in the same channel. Because of this:the CPC s cannot account for deviations in the position of CEA's located 'in symmetrical positions in the core. Such deviations are accounted for in the CPC calculations by penalty factors generated by the two CEAC'_s which each monitor the positions of all'91 CEA's.
The penalty factors calculated by the two CEAC's (CEAC #1 in channel "B" and CEAC #2 in channel "C") are transmitted by optically isolated data links to each of the four CPC's.
Each CEAC receives position information for. 68 CEA's directly from RSPT stacks in its channel. CEAC #1 receives position information for the remaining 23 CEA'
' rom channel "A" RSPT's through CEA position isolation. amplifiers. CE.c #2 receives position information for the remaining 23 CEA's from channel "D" RSPT's through CEA position isolation amplifiers.
The CEA position isolation amplifiers and optical isolators in the CEAC/CPC data transfer links provide the desired inter-channel electrical isolation.
One of the surveillance requirements, TS 4.3.1.4, requires that the isolation characteristics of each Control Element Assembly Position Isolation Amplifier (CEA PIA) Assembly and each optical isolator for CEAC to CPC data transfer be measured every 18 months. Specifically, the isolation amplifiers are checked by applying 120 volts AC across the output for 30 seconds and verifying that the input voltage does not exceed 0.015 volts DC and by applying 120 volts AC across the input for 1
30 seconds and verifying that the output voltage does not exceed 8 volts DC. By performing this check, the isolation amplifier is subjected to the maximum voltages that would be expected in the event of a worst-case fault on either the input or the output.
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.3-For the optical isolators, the input to output insulation resistance is verified to be greater than 10 megohms when tested using a megohmmeter on the 500 volt DC range. This assures that the optical isolator is effectively performing its isolation function.
SONGS 2 has recently entered its first nominal 24 month fuel cycle.
SONGS 3 will enter its first nominal 24 month cycle with cycle 4 startup in mid-1988. A plant shutdown is required to perform these surveillances. The current 18 month surveillance interval could L
necessitate a-plant shutdown solely for the purpose of performing 18 month surveillance requirements. To avoid the need for an otherwise unnecessary shutdown, the proposed change would increase the surveillance test interval from 18 months to "once-each refueling."
L The license. states that fulfillment of these surveillance requirements 1-requires that two reactor protection channels be out-of-service simultaneously. Although this could be accomplished during plant operation, the Plant Protection System trip logic would be in an undesirable one-out-of-two configuration, significantly increasing the risk of a spurious reactor trip ano engineered safety features actuation. This would be contrary to SCE's trip reduction program and TS 4.3.1.4 requires that these surveillance tests be performed during a plant shutdown.
Moreover, the licensee states that a review of the results of the required surveillance tests on the position amplifiers over the period
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from March.1982 through December 1987 has confirmed that the measured input and output values are well below the specified limits and that no adverse trend in the measured data exists. For the 18 month tests performed on the optical isolators to date, the measured resistance has l'
always exceeded 10 megohms. Since only pass / fail information is recorded for this test, it is not possible to trend quantitative results.
-However, no adverse trend in equipment performance has been noted. Most credible failures that could be experienced by the CEA PIAs and the CEAC/CPC data transfer optical isolators would be detected and flagged by either the CFC's or the CEAC's as sensor failures. The probability of an undetected on-line failure is considered to be very low.
The staff has evaluated the licensee's submittal. Since the isolation amplifiers and optical isolators are located in a controlled environment, the staff believes that they are not likely to change their isolation capability during the six months of extended surveillance interval (from l
18 months to 24 months).
In addition, Technical Specification 4.0.2 allows the current 18 month interval to be extended by 25%, to 22.5 months. For these reasons, and because the staff believes that the operating characteristics will not change significantly for an increase from the currently allowable 22.5 months to 24 months, a surveillance interval of 24 months for the channel calibration is ecceptable.
However, the 25% extension of the surveillance interval allowed under l
Technical Specification 4.0.2 will no longer be permitted, and the proposed Technical Specification,has been modified accordingly.
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.o Therefore, based upon the above information, the staff approves the amendments allowing the surveillance interval to be changed to once per i
refueling interval.
2.2 PCN-251 By letter dated April 26,1988,(TS)3/4.3.1,"ReactorProtectiveInstrument-the licensee proposed a change that woula revise Technical Specification ation," and. Technical Specification 3/4.3.2, " Engineered Safety Feature -
Actuation System Instrumentation." TS 3/4.3.1 requires operability of the reector protective instrumentation channels ana bypasses with specified response times. Similarly, TS 3/4.3.2 requires operability of the Engineered Safety Features Actuation System (ESFAS) instrumentation channels and bypasses with trip setpoints consistent with the values specified in the TS. The operability of the reactor protective and ESFAS instrumentation and bypasses ensure that: 1) the associated ESFAS action and/or reactor trip will be initiated when the parameter monitored by each channel or combination thereof reaches its setpoint; 2) the specified coincidence logic is maintained; 3) sufficient redundancy is maintained to permit a channel to be out of service for testing or maintenance; and
- 4) sufficient system functional capability is available from diverse l
parameters. The operability of these. systems is required to provide the overall reliability, redundancy ano diversity assumed evailable in the facility design for the protection and mitigation accident and transient conditions. The integrated operation of these systems is consistent with the assumptions used in the accident analyses. Specifically, the proposed change would revise Surveillance Requirements 4.3.1.3 and 4.3.2.3 of the above specifications, respectively. Technical Specifications 4.3.1.3 and 4.3.2.3 rec,uire that the response times of one of the four channels of instrumentation in the Reactor Protection System (RPS) and ESFAS, respectively, be measured every 18 months and that the results meet specified values. The proposed change would revise the interval for l
these particular surveillances from the current 18 months to an interval dt least once per refueling (nominally 24 months).
Response time testing is performed on approximately 280 sensors and associated electronic signal conditioning, logic, and actuation devices.
A' number of methods are utilized to perform the response time neasurements.
Response time testing requires that the safety-related component, or components, being tested, be renoved from service.
In some cases, access i
to the containment is required.
In order to optimize safe operation of the unit and to maintain personnel exposure as low as reasonably achiev-able, this testing is best performed with the unit in one of the shutdown modes. Several weeks in one of these modas would be required to complete this testing.
The change in RPS and ESFAS Instrument Response Times test frequency may result in a small reduction of confidence in the response time repeat-ability.
However, the licensee's record indicates that approximately 39
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4 5-individual test procedures completed on the sensors, electronics and actuation devices, resulted in only two instances where the procedure acceptance criteria were exceeded. Also, since the current TS schedule for channel check, monthly functional test and 18 month interval channel calibration for RPS and ESFAS functions are not changed, it is understood that any instrument setpoint drif t will be detected during the 18 month channel calibration test.
In addition Technical Specification 4.0.2 allows the current 18 month interval to be extended by 25%, to 22.5 months. For-these reasons, and because the staff believes-that operating characteristics will not change significantly for an increase from the currently allowable 22.5 months to 24 months, a surveillance interval of 24 months for the. channel calibration is acceptable. However, the 25%
extension of the surveillance interval allowed under Technical Specifi-cation 4.0.2 will no longer be permitted, and the proposed Technical Specification has been modified accordingly.
Therefore, based upon the above information, the staff approves the amend-ments allowing the surveillance interval to be changed to once per refueling interval.
2.3 PCN-282 By letter dated December 19, 1986, the licensee proposeo a change that would revise Technical Specification (TS) 3/4.1.3.3, " Position Indicator-l~
Channel-Shutdown" to increase the interval for surveillance tests, which L
.dre currently performed every 18 months, at each ref ueling in Modes 3, 4 or 5, to a " refueling interval," nominally 24 months. Technical Speci-fication:3/4.1.1.3requireseachoftheControlElementAssembly(CEA)
Reed Switch Position Transmitter (RSPT) inoicator channels be determined L
operable by performing a Channel Functional Test.
The RSPTs are used to detect'CEA positions and
.(CPCs) (25% for each CPC) provide input to both the Core Protection Calculators and CEACs. The overwhelming majority of plant operation is conducted in an all rods out configuration. 'This surveillance provides assurance that the CPC/CEACs actually respond to rod motion by testing the RSPTs response over the entire range of possible rod positions from full-in to full out.
If the unit were shutoown or tripped during the fuel cycle and the surveillance requirement had not been completed within the required time frame, this surveillance would have to be conducted prior to restart.
The licensee states that a review of the history of the required 18 month surveillance tests conducted from commercial operation to the present was performed and no adverse failure trends were observed.
In addition, the CPC/CEACs are self-checking digital computers which are subject to monthly surveillance tests and detailed channel checks on a shift basis. The extension of the refueling interval functional tests for the RSPTs has no impact on plant safety because these cetailed checks will ioentify any channel problem before it can impact the conservative operation of the CPC/CEAC.
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. SONGS Unit 2 and Unit 3 have both entered their first nominal 24 month fuel cycle. A plant shutdown is required to perform these surveillances.
The current 18 month surveillance interval could require aoditional outage time, in the event of a plant shutdown solely for the purpose of performing 18 month surveillance requirements. To avoid the need for an extension of an unplanned outage, the proposed change would increase the surveillance test interval from 18 months to "once per refueling interval."
The staff has evaluated the licensee's submittal. The RSPTs are used to detect CEA positions and provide input to both the CPCs and the CEACs.
Each of the 91 CEAs is monitored by two RSPTs and by the Plant Monitoring System through a diverse position monitoring system. Any~ change in the calibration of a single RSPT is easily detected by comparison of these-three. indications.
In addition, Technical Specification 4.0.2 allows the current 18 nonth interval to be extended by 25%, to 22.5 months. For these reasons, and because the staff believes that operating character-istics will not change significantly for an increase from the currently allowable 22.5 months to 24 months, a surveillance interval of 24 months for the channel calibration is acceptable. However, the 25% extension of the surveillance interval allowed under Technical Specification 4.0.2 will no longer be permitted, and the proposed Technical Specification has been modified accordingly.
Therefore, baseo upon the above inforr.iation, the staff approves the amend-
-ments allowing the surveillance interval to be changed to once per refueling interval.
3.0 CONTACT WITH STATE.0FFICIAL The NRC staff has advised the State Department of Health Services, State of California, of the proposed determination of no significant hazaros consideration.
No comments were received.
4.0 ENVIRONMENTAL CONSIDERATION
Pursuant to 10 CFR 51.21, 51.32, and 51.35, an environnental assessment L
and findin FR 47597) g of no significant impact have been prepared and published (54 in the Federal Registe_r on hovember 15, 1989 Accordingly, based upon the environmental assessment the Commission has determined that the issuance of this amendment will not have a significant effect en the quality of the human environnient.
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5.0 CONCLUSION
We have' 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 Connission's regulations and (3) the issuance of the amendments will not be inimical i
to the. common defense and security or to the health and safety of the public.
Principal Contributor:
- 1. Ahmed Lawrence E. Kokajko Dated: November 21, 1989
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