ML20129K390
| ML20129K390 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/18/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20129K389 | List: |
| References | |
| NUDOCS 9611220188 | |
| Download: ML20129K390 (4) | |
Text
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UNITED STATES l
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,g NUCLEAR REGULATORY COMMISSION
'f WASHINGTON, D.C. 20066-4001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION j
RELATED TO AMENDMENT NO.133TO FACILITY GPERATING LICENSE NO. NPF-10 i
l AND AMENDMENT NO.122 TO FACILITY OPERATING LICENSE NO. NPF-15 i-
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SOUTHERN CALIFORNIA EDISON COMPANY j
SAN DIEGO GAS AND ELECTRIC COMPANY l
THE CITY OF RIVERSIDE. CALIFORNIA j
i THE CITY OF ANAHEIM. CALIFORNIA i
j SAN ONOFRE NUCLEAR GENERATING STATION. UNITS 2 AND 3 DOCKET NOS. 50-361 AND 50-362 i-
1.0 INTRODUCTION
By application dated July 17, 1995, Southern California Edison Company (SCE or the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License Nos. NPF-10 and NPF-15) for San Onofre Nuclear Generating Station, Unit Nos. 2 and 3.
The proposed changes would revise the frequency of surveillance requirements for certain plant protective system instrumentation ccntained in Technical Specifications (TS) 3.3.1, " Reactor Protective System (RPS) Instrumentation - Operating," TS 3.3.2, " Reactor Protective System (RPS) Instrumentation - Shutdown," TS 3.3.3, " Control Element Assembly Calculators (CEACs)," TS 3.3.4, " Reactor Protective System (RPS) Logic and Trip Initiation," TS 3.3.5, " Engineered Safety Features Actuation System (ESFAS) Instrumentation," and TS 3.3.6, " Engineered Safety Features Actuation System (ESFAS) Logic and Manual Trip."
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2.0 BACKGROUND
The present surveillance requirements (SRs) in the above listed TS sections require, in part, that certain plant protective system (PPS) instrumentation, which includes the reactor protection system (RPS) and engineered safety feature actuation system (ESFAS) instrumentation, be demonstrated OPERABLE by the performance of a CHANNEL FUNCTIONAL TEST (CFT) at least once in 92 days.
I This licensee proposes to revise the PPS 92-day surveillance test interval to 30 days on a STAGGERED TEST BASIS (60 days on a STAGGERED TEST BASIS for the two channels of CEACs), and where staggered testing is not applicable, extends the CFTs from 92-day sequential to 120-day sequential. The new test interval will result in each PPS channel being tested at 120-day intervals.
In addition, the channel calibration interval for nuclear instrumentation (NI) and several other minor instrumentation system will be extended.
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j I The proposed TS amendment for the change in PPS functional testing interval is based on the reliability analysis presented in. topical report CEN-327-A, 4
"RPS/ESFAS Extended Test Interval Evaluation," and Supplement I to CEN-327-A prepared by Combustion Engineering for the Combustion Engineering Owners Group l
(CE0G).' This' report was previously approved by the staff by letter dated November 6,1989, for quarterly test intervals and is presently being used by the San Onofre licensee to justify extending the test intervals to 120 days.
Probabilistic risk analysis techniques were used to demonstrate that the l
proposed surveillance interval extensions had a negligible impact on plant risk when compared with current technical specification requirements. The documentation submitted by the licensee verifies that the same methodology and fault tree analysis of topical report CEN-327-A was used in analyzing the present request to extend the PPS surveillance test interval to 120 days. The licensee also conducted a plant specific nuclear instrumentation system j
unavailability study to support extension of the channel calibration interval for the NI, including the linear subchannel gains settings, which were not included in CEN-327-A.
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The analysis presented in topical report CEN-327-A estimated a slight increase in RPS unavailability as a result of extending the functional test interval l
from monthly to quarterly. The analysis also estimated a reduction in scram
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and core melt frequency based on the expected reduction in test-induced j
transients / scrams. The staff's safety evaluation (SE) for CEN-327-A found, j
therefore, that the overall impact of reduced RPS testing intervals on safety 1
is negligible. The results of the analysis regarding reduced ESFAS testing on core melt frequency was found to be similar to the reduced testing of RPS j
instruments.
Topical report CEN-327-A does not address the effect of drift in eithe the instrument strings or sensors. These effects are specific to each ir.vidual i
plant and as a result, the staff required licensees to review plant tsecific drift data (as found, as left) for each instrument channel involve <
The i
staff's SE for CEN-327-A required the licensee to confirm that the. rift i
occurring over the proposed surveillance interval will not cause tha setpoint to exceed the allowable value for that channel as calculated by the licensee setpoint methodology.
3.0 EVALUATION Topical report CEN-327-A explicitly addressed the proposed 120-day CFT extensions for all the RPS instrumentation listed in TS Table 3.3.1-1, the ESFAS instrumentation listed in TS Table 3.3.5-1, the four RPS logarithmic power channels required by TS 3.3.2 to be operable during plant shutdown, and the control element assembly calculators governed by TS 3.3.3.
Specifically, the CFTs are proposed to be changed to a 30-day frequency on a STAGGERED TEST BASIS fnr SR 3.3.1.7, SR 3.3.2.2, and SR 3.3.5.2, and changed to a 60-day frequency on a STAGGERED TEST BASIS for SR 3.3.3.3.
This will result in each channel being tested at a 120-day interval. Also, the CFT frequency for the RPS and ESFAS logic channels will be changed from 92 days to 120 days sequential (SR 3.3.4.2 and SR 3.3.6.1, respectively).
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In addition, the CFTs for certain instrument bypass logic checks will be f
extended by this TS amendment proposal. SR 3.3.1.12, SR 3.3.2.3 and SR i
3.3.5.6, (this is SR 3.3.5.7 in the amended TS) which applies to certain RPS and all ESFAS instrumentation, currently requires that the bypass logic be i
demonstrated operable prior to each reactor startup unless performed during the preceeding 92 days. The licensee proposes to revise this interval to 120 i
-days proceeding each reactor startup. SR 3.3.5.3, which currently requires i
the CFT frequency for each ESFAS bypass function to be further checked at 92-day intervals, will be changed to a 120-day interval.
i The staff confirmed that the licensee evaluation for the proposed CFT extension was derived from the RPS and ESFAS fault tree models developed for and presented in Topical Report CEN-327-A, including Supplement 1.
The staff's SE dated November 6,1989 approving CEN-327-A found the overall impact of reduced PPS functional testing intervals on safety to be negligible.
i Moreover, the licensee performed a specific evaluation for the San Onofre Units 2 and 3 instrumentation to support the proposed 120-day CFT interval i
extension. Therefore, the staff finds acceptable the frequency extensions j
proposed for the above listed SRs.
i The calibration interval for the power range neutron flux channels (SR 3.3.1.8) and the verification of the linear power subchannel gains of the excore detectors (SR 3.3.1.6) will also be revised from 92-day to 120-day sequential. The licensee conducted a plant specific nuclear instrumentation system unavailability study to support extension of the channel calibration interval for the NI including the linear subchannel gain settings, since this issue was not included in CEN-327-A. The study determined that because of the high reliability of the NI, the surveillance intervals for the nuclear instrumentation linear power subchannel gain amplifiers and associated nuclear instrumentation can be extended to a 120-day sequential interval with no increase in system unavailability. The staff agrees that the proposed increase in calibration interval will not increase system unavailability, and finds the 120-day calibration interval to be acceptable.
As noted in Section 2.0 of this SE, the effects of drift are plant specific and are to be included with each individual plant analysis, as stated in the staff's November 6, 1989, SE on CEN-327-A.
Licensees requesting the CFT interval extension should confirm that they have reviewed drift information, including as-found and as-left values for each instrument channel involved.
The review should determine that the drift occurring in that channel will remain bounded by the licensee's setpoint methodology for the extended surveillance interval. Additionally, licensees should maintain on site records of the setpoint calculations and associated data to support planned future staff audits. The San Onofre licensee has provided information on the plant specific drift analysis methodology and the results were demonstrated to be bounded by the current setpoint calculations. The staff concludes, therefore, that the conditions stated in the November 6, 1989 staff SE for CEN-327-A have been met by the licensee, and that the current setpoint calculations are acceptable.
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. )i The calibration of transmitters and signal processing equipment continues to be conducted at each refueling interval and is not affected by the proposed increase in the functional test surveillance interval. Also, the margin or i
error allowances related to the channel calibration interval of 24 months will i
remain unchanged.
Therefore, this amendment request does not compromise the bases for the 24-month calibration interval as stated in San Onofre license Amendment Nos. 88 and 78.
1 Although not included in the staff's review of the proposed changes to the TS,
.the licensee has also revised the Bases of the TS to reflect the new surveillance intervals.
4.0 STATE CONSULTATION
l In accordance with the Commission's regulations, the California State official was notified of the proposed issuance of the amendments. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
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The amendment.s change surveillance requirements. The NRC staff has determined i
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, ed 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 comment on such finding (60 FR l
45185). Accordingly, the amendments meet the eligibility criteria for 1
categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR i
51.22(b) no environmental impact statement or environmental assessment need be i
prepared in connection with the issuance of the amendments.
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6.0 CONCLUSION
I The Commission has concluded, based on the considerations discussed above, i
that (1) there is reasonable assurance that the health and safety of the i
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:
M. C. Gareri, HICB Date:
November 18, 1996
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