ML20211C032

Proposed Tech Specs Extending Allowable Outage Time on Diesel Generator O from 7 to 21 Days

ML20211C032
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	02/10/1987
From:	COMMONWEALTH EDISON CO.
To:
Shared Package
ML20211C023	List: ML20211C018 ML20211C032
References
2704K, NUDOCS 8702190674
Download: ML20211C032 (13)

Text

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$$ For a 21 day period during the Unit 2 Spring 1987 refueling outage, O$ with Unit 2 in Mode 5 or 6, only two diesel generators (IA, IB) are ya required to satisfy the standby AC onsite power requirements for og Unit 1 as specified in Sections 3.15.1.B. 4.15.1.B.2, 3.15.2, and gg 4.15.2. The surveillance testing specified in 4.15.1.B.2 will be oro performed on diesel generators IA, IB, 2A, and 2B immediately prior g

~[p3 to removal of "0" diesel generator from service. During the 21 day 2b4 period, diesel generators IA, IB, 2A, and 2B will be verified (1) operable at least once per day. The surveillance frequency for diesel generators IA and IB will remain as specified in the Zion Confirmatory Order of February 29, 1980. In the event that diesel generator IA or IB becomes inoperable Unit 1 xill be brought to Mode

. 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 5 within the next 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

Should 2A and 2B diesel generators become inoperable during the 21 day outage on "0" diesel generator, the ACTION statements on the table on page 255b shall apply.

(1) The term verify as used in this context means to administrative 1y check by examining logs or other information to determine if certain components are out-of-service for maintenance or other reasons. It does not mean to perform the surveillance requirements needed to demonstrate the OPERABILITY of the components.

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1 Unit I l Unit 2 Diesel Generator O 1A IB O 2A 2B Bus 147 148 149 247 248 249 Service Water Pp 1A IB IC 2A 2B 2C Comp. Cool Pp OE OD OC --

OB OA ACTION O Diesel Gen. OOS Operable Operable OOS Operable Operable No LCO. No additional surveillance.

1A Diesel Gen. OOS Inop Operable OOS Operable Operable Unit 1 Mode 3 within 12 hrs. Mode 5 additional 30 hrs.

1B Diesel Gen. OOS Operable Inop OOS Operable Operable Unit 1 Mode 3 within 12 hrs.

Mode 5 additional 30 hrs 1A & IB Diesel Gen OOS Inop Inop OOS Operable Operable Immediate Shutdown 2A Diesel Gen. OOS Operable Operable OOS Inop Operable No LCO, No additional surveillance 2B Diesel Gen. OOS Operable Operable OOS Operable Inop No LCO, No additional surveillance 2A 3 2B Diesel Gen OOS Operable Operable OOS Inop Inop Unit 1 operation 7 days.

Test IB & IC SWPp's and OD & OC CC Pps daily.

ACTION STATEMENTS FOR 21 DAY PERIOD OF "O" D/G OUTAGE (SPRING 1987)

?S5b 11000/11010

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ATTACHMENT 2 Scheduled Testing / Modifications / Maintenance for "O" Diesel Generator During Unit 2 Spring 1987 Refueling Outage Estimated Description Manhours Commen,ts Work Requests Refueling Outage Maintenance 940 Misc. Commitments Torque 5 Valve Manifolds 16 10 CFR 21 commitment Miscellaneous Repair Work Requests 640 None Modifications D/G Instrument Upgrade 2 weeks Incresse D/G reliability D/G Turbo Lube Oil Filter Upgrade 1 week Increase D/G reliability and personnel safety D/G Bkr and Engine Isolation Switch 4 days Appendix R commitment 4KV ESS Bus Control Circuitry 1 week Increase D/G reliability Testing 5 days Total for all testing Modification Testing -

None Engine Overspeed Test - None D/G Maintenance Run - None 2704K

l ATTACHMENT 3 l

PCWER SUPPLIES TO BUS 147 O

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(1) Offsite power + Unit 1 system aux. Xfmr. --.pbus 142-.-> bus 147.

This is the normal configuration.

(2) Unit 1 generator-.> Unit 1 unit aux. Xfrmr.4 bus 142-.pbus 147.

This source is available with Unit 1 on line, and is lined up by manual switching from the main control board.

(3) Offsite power + Unit 2 system aux. Xfmr. 4 bus 147.

This source is lined up by manual switching from the main control board.

(4) Offsite power- ) Unit I unit Aux. Xfmr. (backfeed)+ bus 1429 bus 147.

This source is available with Unit 1 off-line, and is lined up by removing removable links in the Unit 1 generator output bus (manual operation, can be accomplished in less than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />).

(5) Diesel generator "O" 9 bus 147.

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. ATTACHMENT 4

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Excerpt from Zion,Probabilistic Safety Study, Vol.- 3 It is assume [in this study that all initiating events ultimately result in a trip of the main generator on the affected unit. Since each of the Zion units is rated at 1085 MW(e), the instantaneous loss of this input (

could have a significant effect upon the stability of the offsite power \

supply network due to reduced t,ransmission voltages, frequency fluctua-tions, or power flow imbalances as the grid recovers from the tran-sient. The Commonwealth Edison transmission network has been designed to provide a stable power supply grid under conditions of multiple, large generating unit and major transmission line outages. Utility interconnections to the north, west, south, and southeast provide ('

excellent geographical stability. Two of these tie lines (to the (

Wisconsin Electric Power Company) directly supply the Zion 345 kV switchyard, providing increased diversity in the power sources for this specific site. Detailed guidelines have been established for the entire Commonwealth Edison power supply network which define the basis for .i system operation under a wide variety of steady-state and transient conditions. A prime consideration in the establishment of these guide-lines is the requirement that no single loss of a generating unit or transmission facility should result in an unacceptable condition of degraded system operation. System operating contingencies are defined by these guidel.ines and specify the need to provide additional gener-ating capacity from Commonwealth Edison's own facilities or to provide -

power from network in.terties long before critical operating stability limits are approached. A detailed voltage reduction and selective-load shedding program is also specified in order to maintain grid stability with adequate margins under the most severe conditions. Detailed system stability studies have been performed to verify the efficacy of these operating guidelines under a wide range' of scenarios. The combined effects of these guidelines and the overall design stability of the

• Commonwealth Edison transmission network are demonstrated by the fact that there has never been a major grid failure or a local failure of the offsite power supply to Zion as a result of the loss.of a single gener-

, ating unit. (In fact, there has never been a loss of all offsite power

at Zion from any cause.)

The assignment o'f a distribution for the probability of losing all off-site power to the Zion switchyard as a result of the trip of one of the Zion units is an extremely difficult task. Factors affecting this condition are total system load, available spinning reserve capacity, l

the fraction of the load being supplied from the Zion units, the status of neighboring utilities' networks, scheduled and unscheduled outages of

. specific generating units and transmission lines, etc. The analysis of this problem presented in WASH-1400 applies a median value of 10-3 for the conditional loss of offsite power as a result of a unit trip.*

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• WASH-1400, Apendix II, page 34.

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Several factors limit the applicability of this value to the specific  !

problem faced in this study. The WASfi-1400 distribution was developed '

from a review of Federal Power Conunission studies of power supply net- .

works in a wide variety of locations east of the Rocky Mountains. While l it may be applicable to the composite site studied in WASH-1400, it is certainly not directly applicable to the Zion site. It must also be recognized that the reference study is now several years outdated and that significant advances in the design, operation and overall stability of virtually all transmission networks in the United States have been made during the intervening years.

Unfortunately, no specific studies have been conducted to address the precise problem posed at Zion. However, a review of the available Comonwealth Edison system design criteria and operating guidelines, several grid stabiity studies focusing specifically upon the Zion site, and conversations with Commonwealth Edison engineers have provided a significant amount of applicable information. As a result of these inputs, we have assigned the following distribution for the probability of losing offsite power to the Zion switchyard as a result of a trip of either of the Zion units:

Median: 2 x 10-5 failure / unit trip '

Sth Percentile: 4 x 10-7 failure / unit trip 95th Percentile: 1 x 10-3 failure / unit trip.

The mean and variance of this assumed lognormal distribution are Mean: 3.38 x 10-4 failure / unit trip Variance: 3.26 x 10-5, A few observations must be made in order to place this distribution in a proper perspective. It is our best estimate of a conservative distri ,

bution to be applied to this analysis only. Although it is broadly based upon the results of Comonwealth Edison grid stability studies developed for the Zion site, none of the studies reviewed was directly applicable to the problea at hand. Most of the studies address a condi-tion less severe than the total loss of offsite power, and those reports

' developed for the loss of power do not address it from the cause-effect relationship presented in this analysis. For these reasons, we feel that the median value of our distribution is a very conservative esti-i mate for the frequency of this' event. However, we also feel that the

! assigned broad distribution adequately accounts for our uncertaintly in l this value. The given distribution is thus considered to represent a

conservatively bounding estimate for the conditional failure of offsite power, which is as specialized to the Zion site as is possible with the j existing information base.

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1 Excerpt from " Response to the BNL Peer Review of the Zion Probabilictic Study," F. G. Lentine to H. R. Denton, dated 9/6/82:

A two-stage Bayesian update was pe'rformed using the data from Table 1.

As suggested by the BNL review coments, the Zion data was excluded from the plant population for the first step of the analysis. The plant population data was applied using the total number of offsite power -

failure events for each site and the total number of site years. listed 7 in Table 1 (i.e., not accounting for the effects of unit availability).

The generic data was updated using the Zion site. specific evidence of no failures in 9 site years. The resulting distribution provides the specialized calendar year frequency of loss of offsi.te power events at .i the Zion site, regardless of unit operating conditions. This distribu-tion was then multiplied by the average Zion unit availability (0.71) to obtain the frequency of losses of offsite power to a Zion unit during power operation.

are The parameters of this updated and scaled distribution 5th Percentile: 1.04 x 10-2 failure /unf t operating year-Median: .

3.63 x 10-2 failure / unit operating year -

95th Percentile: 1.27 x 10-1 failure / unit operating year Mean:

4.85 x 10-2 failure / unit operating year The mean frequency for the loss of offsite power at a generic plant site from the given population, excluding the Zion evidence, was determined to be 0.194 events per site calendar Lea *. The updated mean frequency for the loss of offsite power at the Zion site is 0.068 events per site calendar year. ,.

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i ATTACIDfENT 5 4KV Bus 147/247 148/248 149/249 Components Containment Spray Pumps A B C Safety Injection Pumps A B Centrifugal Charging Pumps B A Auxiliary Feedwater Pumps B C

Residual Heat Removal Pumps B A Component Cooling Pumps OE(147) OD(148) or OB(248) OC(149) or OA(249)

Service Water Pumps A B C Containment Fan Coolers C A, D B3 E W

O ATTACHMENT 6 Number Required Number Available Number Required With No Power Components in Licensing Bases in ZPSS to Buses 247/147 Containment Spray Pumps 1 (Iodine removal) 1 2 2 (Pressure suppression)

Safety Injection Pumps 1 Any 2 of 4 SI 1 Centrifugal Charging Pumps 1 1 Auxiliary.Feedwater Pumps 1 1 3 (including steam-driven)

Residual Heat Removal Pumps 1 1 2 Component Cooling Pumps 2 (total for both units) 1 (Loss power of offsite 4 2 (LOCA))

Service Water Pumps 2 (total for.both units) 3 4 Containment Fan Coolers 3 3 4 e

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REFERENCES FOR ATTACHMENT 6 Componenta Zion Tech. Spec. Bases Zion Prob. Safety Study Containment Spray Pumps p. 154 Vol. 3, p. 1 5-545 Safety Injection Pumps p. 193 Vol. 3, P. 1 5-361 Centrifugal Charging Pumps p. 193 Vol. 3, P. 1 5-361 Auxiliary Feedwater Pumps p. 162 Vol. 3, P. 1 5-68'3 ,

Residual Heat Removal Pumps p. 193- Vol. 3, p. 1 5-40'O Component Cooling Pumps p. 193 9/12/83 F. G. Lentine to H. R. Denton; Section 3,

p. I.2-I.5 Service Water Pumps pp. 193, 195 Ibid., p. I.6, I.7 Containment Fan Coolers p. 149 Vol. 3, p. 1 5-580 Additional references:

Amendment 68 to DPR-39 (9/25/81) and SER Amendment 72/66 to DPR-39 and DPR-48 (12/31/81) and SER ,

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ATTACHMENT 7 EVALUATION OF SIGNIFICANT HAZARDS CONSIDERATION PROPOSED CHANGES TO ZION TECHNICAL SPECIFICATION APPENDIX A - SECTIONS 3.15 AND 4.15 AUXILIARY ELECTRICAL POWER SYSTEM DESCRIPTION OF AMENDMENT REQUEST An amendment to the Zion Facility Operating License is proposed to allow a one-time 21 day outage for "O" diesel generator during the Unit 2 Spring 1987 refueling outage. ,

BACKGROUND 10 CFR 50.92 states that a proposed amendment will involve a no significant hazards consideration if the proposed amendment does not:

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety.

The discussion below addresses each of these three criteria and demonstrates that the proposed amendment involves a no significant hazards consideration.

BASIS FOR'NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION Does the proposed amendment (1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety?

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1 A DISCUSSION - ITgM 1 This. proposed amendment will result in the one-time 21 day outage period for "O" diesel generator during the Zion Unit 2 Spring 1987 refueling ,

outage. This change is being requested to allow the completion of required i Appendix R modifications and the performance of an extensive refueling outage maintenance program. Both of these activities will result in a diesel generator with increased reliability.

-The effects of an extended outage for "O" diesel generator with one reactor operating and the other reactor in cold shutdown has been evaluated by the NRC Staff. This evaluation was provided in Reference (d) in support of the NRC's previous approval of a forty-five day outage period for "O" diesel generator.

The conclusion of that evaluation is given on page 4 of the

. Attachment to the'SER.

By comparing these onsite AC power reliability estimates, which use consistent success criteria assumptions, the proposed configuration is seen to be as reliable, perhaps more so than the currently allowed configuration for the loss of offsite power sequences of concern. This is due primarily to the commitment not to perform maintenance on the other diesels while the' swing diesel is out of service. The non-seal LOCA loss.of offsite power sequences, are not affected by swing diesel considerations since the motor driven AFW pumps are powered of the A and i B diesel generators. Actually, AFW reliability is increased for the time the swing diesel is out-of-service since the A and B diesels must be operable during this period.

Based upon the above discussion the AC power reliability of Zion Station during this 21 day period is calculated to increase or remain stable.

Thus, this proposed amendment does not involve a significant increase in a probability or consequences of an accident previously evaluated.

t DISCUSSION - ITEN 2 l

I The flexibility to allow a one-time 21 day outage on "O" diesel generator has no effect on the reliability or integrity of any of Zion's

systems. As discussed above, the reliability of the AC power system is characterized to be "as reliable, perhaps more so than the currently allowed configurations for the loss of offsite power sequences of concern".

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' This 21 day one-time outage period will not have any effect on any of Zion's systems nor on the generation of any external event such as a turnado or flood. This new requirement will not create the possibility of any additional system malfunctions or externally generated events.

Therefore, this proposed amendment cannot create the possibility of a new or different kind of accident from any accident previously evaluated. ,

1 0 r DISCUSSION - ITEM 3 As discussed in Item 1 and in Reference (d), the onsite AC power reliability estimate will be as reliable or perhaps more so than the currently allowed configuration for the loss of offsite power sequences of concern. In addition, the maintenance and modifications performed on "O" diesel generator during this 21 day period will result in a diesel generator with increased reliability. These factors result in either an increased or constant margin of safety.

Thus, this change does not involve a reduction in the margin of safety.

Therefore, since the application for amendment satisfies the criteria specified in 10 CFR 50.92 and is similar to examples for which no significant hazards consideration exists, Commonwealth Edison Company has made a determination that the application involves no significant hazards consideration.

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