ML20206U799
| ML20206U799 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/30/1986 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | Knighton G Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML13305A889 | List: |
| References | |
| GL-84-15, TAC-54698, TAC-54699, TAC-61516, TAC-61517, NUDOCS 8610080380 | |
| Download: ML20206U799 (12) | |
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Southem Califomia Edison Company P. O. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 m,;" luEc[n N ewsmo September 30, 1986 mIE'EE.
Director, Office of Nuclear Reactor Regulation Attention: Mr. George W. Knighton, Director PWR Project Directorate No. 7 Division of PWR Licensing - B U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket Nos. 50-361 and 50-362 San Onofre Nuclear Generating Station Units 2 and 3 By letters dated March 17, 1986 and June 13, 1986, SCE transmitted proposed Technical Specification Change Numb _er NPF-10/15-192 (PCN 192) to the NRC. This proposed change provided SCE's response to reduce cold fast start tc: ting af the dicscl generators ccasisteal wili) iiRC Generic Letter 84-15.
Subsequently, the NRC provided SCE with a draft Staff evaluation of PCN-192 dated July 25, 1986 which indicated that, as submitted, PCN-192 required additional justification prior to NRC approval.
On August 14, 1986, SCE met with the NRC to discuss the PCN-192 Staff Evaluation and identify the additional justification required.
Possible j
modifications to PCN-192 were also discussed.
During this meeting, SCE committed to providing the NRC with the required additional justification and/or modifications to PCN-192.
Consistent with the agreements reached during this August 14, 1986 meeting, provided in Enclosure I is the NRC requested additional justification for PCN-192. Also provided in Enclosure I are revised attachments B and D which replace the corresponding attachments of PCN-192. These revised attachments B and D incorporate the modifications to the proposed change discussed during the August 14, 1986 meeting. The new attachments B and D also provide a new change to the Technical Specification 4.8.1.1.2.a.5 to make 8610030380 860930 0
DR ADOCK 05000361 jL i
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N-A Mr. G. W. Knighton the proposed change consistent with Generic Letter 84-15 and to clarify this Technical Specification requirement.
Provided as Enclosure II is a description of SCE's complete comprehensive diesel fuel oil testing program i
which ensures that non-safety related diesel fuel parameters are maintained within acceptable limits.
If you have any questions regarding the enclosed information, please call me.
Very truly yours, i
Enclosures cc: Harry Rood, i4RC Project Manager (To be opened by addressee only)
F. R. Huey, USNRC Senior Resident Inspector, Units 1, 2 and 3 i
4 b
W ENCLOSURE I i
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2 ADDITIONAL JUSTIFICATION FOR PCN-192 The proposed change revises Technical Specification 3/4.8.1.1 " Electrical Power Systems, AC Sources" to reduce the required number of fast cold start surveillance tests for diesel generators.
The proposed change also modifies 4
diesel fuel oil. testing requirements to more accurately determine the quality 1
of the diesel fuel oil.
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The purpose of Technical Specification 3/4.8.1.1 is to ensure that sufficient l
power will be available to supply the safety related equipment required for (1) the safe shutdown of.the facility and (2) the mitigation and control of i
accident conditions within the facility.
The proposed change to the Technical Specification consists of the following parts:
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(a) Technical Specification Limiting Condition for Operation 3.8.1.1.a currently requires two physically independent circuits between the offsite transmission network and the onsite Class lE distribution j
system. The proposed change would. require two physically l
independent c'rcuits between the offsite transmission network and i
each Class 1E 4kV bus. This change clarifies the Technical 4
Specifications regarding the requirement of General Design Criterion 17 to have two independent offsite circuits to each Class lE 4 kV Bus. This change would also require Action Statement "a" to be entered based on the inoperability of a single 4 kV. bus.
The proposed change would also modify Technical Specification 4.8.1.1.1 to be consistent with T.S. 3.8.1.1.a.
This would remove the existing requirement for cold fast start testing of a diesel l
generator on the unaffected bus when the affected bus lost its l
preferred or auxiliary offsite power source. The start testing of the remaining diesel generator would still be required if the other diesel generator is inoperable. These changes are consistent with General Design Criterion 17 and NRC Generic Letter 84-15.
1 (b) For Modes 1, 2, 3 and 4, existing Technical Specification 3.8.1.1 requires that if a diesel generator has become inoperable, it be A
restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the plant be brought
.i to cold shutdown within the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. 'However, the existing Technical Specifications do not provide any limit on the frequency, of entering this 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement. Thus, the total number 3
of days during which a diesel generator is inoperable over a given i
period of time is not limited by the current Technical Specifications.
Consistent with guidance provided in the example of an NRC acceptable Technical Specification provided as Appendix A to Generic'
]!
Letter 84-15, this proposed change provides a limit of 800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> on
-the combined out of service time for the two diesel generators-in one calendar year..The proposed ~ change requires that the NRC be i
notified at the 800 hour0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> point of the circumstances and the actions-taken to improve diesel generator performance. The 800 hour0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br />
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combined annual out-of-service time limit is based on the following calculation-Assuming a minimum reliability of 0.95 per diesel engine and 50-starts per year per engine, Maximum number of failures per year per engine =-0.05 x 50 = 2.5.
Using 3 days average repair time required per failure, Total unavailability per diesel per year due to failure 4
= 7.5 days i
With an average of 4 days out-of-service per quarter per diesel for preventive maintenance (PM).and/or contingencies, l
Out-of-service time per year per diesel due to PM and/or contingencies = 16 days Total out-of-service time per. year per diesel = 16 days + 7.5 24 days (approx.)
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I Total out-of-service time per year for 2 diesels = 48 days j
= 1152 hours0.0133 days <br />0.32 hours <br />0.0019 weeks <br />4.38336e-4 months <br /> l
Considering that the plant normally operates in Modes 1, 2, 3 and 4 for 70% of the time, total time lost per year in Modes 1, 2, 3 and 4 = 1152 x 0.70 - 800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> (approx.).
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l This proposed 800_ hour combined annual diesel generator out-of-service time limit would ensure a combined diesel generator availability of greater than 95%* and would be applicable.in Modes 1, 2, 3 and 4 only.
The average number of diesel generator starts with the plant in
-Modes 1 through 4 can be found from plant historical data as follows:
1 o Historical Scheduled f.j[3rts Per Diesel
- Starts Monthly Surveillance 12 Subgroup Relay Test
-2 Post Maintenance Testing:
l Quarterly and Annual PM Retest 5
Idle Run 1
Component Break-In 1
Governor Droop Adjustment 5
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-26 800 hrs / unit
_ 2 diesel aenerators = 4.6% unavailability i
8760 hrs / year unit per diesel per year
[95.4% availability per diesel per year]
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's e o Historical Starts / Start Attempts Due to Inoperability of the Redundant Diesel i
- Starts i
1985 4
1984 10 1983 3
17 Average starts per diesel per year:
i 17 starts, 5.7 starts. 5.7 starts /yr, 1.4 starts /yr 3 years yr 4 diesels diesel Starts of redundant diesel due to 3.8.1.1 Action Statements =
3 starts /yr diesel 0 Total average starts per year per diesel - 26 + 1 + 3 = 30 o Historical Preventive Maintenance Outage Time in Modes 1, 2, 3 and 4:
Clearance 8 Hours PM's 16 Oil Leak Repairs 12 Other Repairs 12 Restoration 8
Testing 4
60 Hours / Quarter x 4 Quarters / Year
= 240 Hours / Year
= 10 Days / Diesel o Historical Repair Time:
2 Days / Repair Performing the above cumulative diesel generator out-of-service time calculation usino plant historical data for plant operations in Modes 1, 2, 3 and 4 only, the following results are obtained:
With a minimum reliability of.95 per diesel and 30 starts per year per diesel Number of failures per year per diesel =.05 x 30 - 1.50 With 2 days average repair time (historical) required, total out-of-service time per diesel per year due to repair
= 1.50 x 2 - 3.0 days
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, Using a historical average of 10 days out-of-service time per year per diesel for preventive maintenance, Total out-of-service time per year per diesel
= 10 days + 3.0 days = 13.0 days Total out-of-service time per year for 2 diesels
= 13.0 days / diesel x 2 diesels x 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> / day = 624 hours0.00722 days <br />0.173 hours <br />0.00103 weeks <br />2.37432e-4 months <br /> From the above calculations, it can be seen that the proposed 800 hour0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> combined annual out-of-service time limit presents an acceptable margin to ensure that repairs and preventive maintenance can be performed each year and is consistent with respect to historical plant operations and NRC diesel generator acceptance criteria.
Having thus established an availability goal, this proposed change would increase the existing individual diesel generator out-of-service time limit from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> (3 days) to 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> (7 days).
This change will permit greater flexibility in handling diesel generator malfunctions and/or servicing needs without recourse to plant shutdown. This change from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days would more readily facilitate performance of detailed root-cause investigations of diesel generator failures which are difficult to perform within the current 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period. Additionally, based on the proposed new 800 hour0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> combined annual dicsc1 generator out-of-service time limit, the extension of the time one diesel generator can be inoperable from the current 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to the proposed 7 days will fall within a total annual diesel generator availability of at least 95%.
(c) Technical Specification 3.8.1.1 Action Statements (a) and (b) require the diesel generators to be demonstrated operable by fast cold start testing within one hour and once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter when either one offsite A.C. circuit and/or diesel generator is inoperable. This proposed change would reduce the number of diesel generator fast cold start tests by requiring only one test of the operable diesel generators within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when one diesel generator or one offsite AC circuit is inoperable. This change is consistent with NRC Generic Letter 84-15.
When the changes described in items (b) and (c) are considered together, it is possible that following a failure of one diesel generator the operability of the remaining diesel generator would be verified only once in 7 days prior to required plant shutdown.
There are two reasons for the acceptability of this proposed change.
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. - i (1)
Generic Letter 84-15 provided the acceptability of start testing the remaining diesel generator only once within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of a diesel generator failure without further testing for the remainder of the action statement period. This requirement eliminates the possibility of common mode failure following the failure of one diesel generator. When this test has been completed (the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> start test) the diesel generator should not be treated differently than it otherwise would under normal plant conditions for the remainder of the 7 day period. Thus, start testing of a diesel generator would be required only once during the 7 day period.
(2) Start testing of a diesel generator eliminates the possibility of common mode failure given one diesel generator failure.
Given that most diesel generator failures occur during starting conditions, increased start testing may actually reduce diesel generator reliability.
(The goal of Generic Letter 84-15 is reduced diesel generator start testing.) Therefore, additional start testing of a remaining diesel generator after the initial start test will not increase confidence in diesel generator availability nor improve overall diesel reliability.
It can be concluded that the possibility of start testing of a remaining diesel generator only once during 7 days with one failed diesel generator is acceptable because:
(1) One start test eliminates the probability of common mode failure. After the initial start test, the diesel generator 31 day surveillance would be in effect and demonstrates adequate reliability.
(2)
Increased start testing may decrease diesel generator reliability.
Therefore, the interaction of these two changes does not reduce-diesel generator reliability or availability and as the changes reduce unnecessary start testing of the diesel generators, they are consistent with Generic Letter 84-15.
(d) Technical Specification 3.8.1.1 Action Statement (d) requires that with two offsite AC sources inoperable, two diesel generators must be demonstrated operable by fast cold start testing within one hour and once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter. The proposed change would modify this action statement by requiring the two diesel generators to be verified operable by start testing within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> unless the diesels are already operating.
This reduces the number of fast cold start tests of the diesel generators consistent with NRC Generic Letter 84-15.
This change also corrects 0 typographical error in the Unit 2 Technical Specifications Action Statement "d".
The correction makes the Unit 2 Technical Specifications consistent with u
- 6 g
' the Unit 3 Technical Specifications and the Standard Technical Specifications regarding the time allowed to restore one offsite power source to operable status when two offsite sources are out-)f-service. The existing Unit 2 specification states 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> when 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is the correct number.
(e) Technical Specification 4.8.1.1.2.a.4 currently requires the diesel generators to be verified operable by fast cold start testing in i
accordance with the frequency specified in Table 4.8.1.
This
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testing requires the diesel generators to start from ambient I
condition and accelerate to 900 rpm in less than or equal to 10 seconds. Additionally, the generator voltage and frequency are required to be at 4,360 1 436 volts and 60 1 1.2 Hz within 10 seconds.
The proposed change requires a fast cold start from ambient conditions only once per 184 days.
For all other surveillance starts, the proposed change would allow the diesel generators to be started in accordance with the manufacturers z
recommendations regarding engine prelube and warmup procedures and allow the diesel generator to be gradually loaded. The proposed change would hiso specify that the diesel generators are to be started for the purpose of surveillance testing by the following f
signals only:
(1) manual, (2) simulated loss of offsite power by itself and (3) simulated loss of offsite power in conjunction with an ESF actuation test signal.
This change is consistent with NRC Generic letter 84-15.
(f) Technical Specification Table 4.8-1 prescribes the test frequency for diesel generators based cn the number of failures in the last 100 valid tests. The proposed change would revise the diesel generator test base from the last 100 valid demands to the last 20 valid demands. The proposed change would also delete the last two tiers of test frequency reducing the most frequent diesel generator testing from 3 days to 7 days. This change is consistent with NRC Generic Letter 84-15.
(g) Technical Specification 4.8.1.1.2.c requires that diesel fuel oil be tested for water and sediment content, viscosity, and insolubles once every 92 days and from new fuel prior to addition to the fuel storage tanks. The proposed change would upgrade the testing methods to be consistent with current industry practice and would replace the current test for insolubles with a more accurate and effective test. The bases for these changes are as follows:
(1) Fuels in storage should be tested periodically to detect degradation. Only those parameters that can change during storage need to be tested.
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.. (2)- Periodic testing for particulates formed in storage should identify the actual particulate contamination. The accelerated oxidation stability test (ASTM D2274-70) is currently required to be performed for new fuel and'every 92 days for stored fuel. This test provides a rough prediction of the tendency of the fuel to oxidize and form particulates during storage.
It does.not indicate actual particulate contamination.
In addition, ASTM 0975-81 states " Correlations (of Model 02274 results) with fuel suitability are tenuous." Finally, the ASTM D2274-70 test involves significant costs and a significant administrative burden.
In lieu of the accelerated oxidation stability test, a test for actual particulate contamination, ASTM D2276-83, is proposed.
This test would be performed every 92 days for fuel in storage. Since formation of particulates during storage at ambient temperatures (Note that San Onofre Units 2 and 3 storage tanks are underground) is a relatively slow process, the 92 day test will ensure early detection of particulates.
The proposed change from ASTM D2274-70 (potential insolubles) to ASTM D2276-83 (actual particulates) has been recognized as a substantial improvement in diesel fuel quality testing and represents the only substantive change in the proposed diesel fuel oil testing Technical Specifications.
Additionally, the proposed change would replace the fuel sampling standard, ASTM D270-1975, with ASTM 04057-81 and replace ASTM 0975-77 witii D975-81 as these standards are the current revisions of the standards in industry use.
Verification of diesel fuel oil quality is provided by SCE's complete comprehensive diesel fuel oil chemistry testing.
program (see Enclosure II). This comprehensive program is implemented by procedure and verifies 15 different fuel parameters to be within industry standards. Of these 15 parameters, only those important to the ability of the diesel fuel to start and power the diesel generators are included in the current and proposed Technical Specifications.
(h) This proposed change would modify the Technical Specification Bases to be consistent with the proposed configuration-of the diesel generator systems.
NRC Generic ' Letter 84-15 contains several recommendations' to improve and neintain the reliability of the emergency diesel generators, which, as noted in the' generic-letter, is one of the main factors affecting the risk from station blackout. One of the r.ecommendations is to reduce excessive testing which causes incremental wear and degradation of.the diesel engines. To accomplish this, 3eneric Letter 84-15 provides an example'of an NRC acceptable Technical Specification (TS).
Consistent with this. example TS, the changes t
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described in (a), (b), (c), (d), (e) and (f) above would eliminate all repetitive action statement and surveillance starts of the diesel generators except the initial start to verify the operability of the remaining diesel i
generator (s)..These proposed changes do not affect the surveillance requirements pertaining to the offsite circuits. The change described in (g) above provides for replacing a fuel oil test with a test that is more effective in detecting unsatisfactory fuel thus increasing the reliability of the diesel generators. The change described in (h) above provides for consistency between the proposed plant configuration and the bases.
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