ML17193B287

Forwards Revised Evaluation of SEP Topic VIII-2 Re Diesel Generators.Evaluation Will Be Basic Input to Integrated Safety Assessment for Facility

ML17193B287
Person / Time
Site:	Dresden
Issue date:	03/31/1981
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Abel J COMMONWEALTH EDISON CO.
References
TASK-08-02, TASK-8-2, TASK-RR LSO5-81-03-078, LSO5-81-3-78, NUDOCS 8104080305
Download: ML17193B287 (14)

Text

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March 31, 1981 Docket No. 50-237 LSOS-81-03-078 Mr. J. S. Abel

• Director of Nuclear Lfcens1ng Commonwealth Edison Company Post Office Box 767 Chicago, 11 Hnois 60690

SUBJECT:

.SEP TOPIC VIII-2, DIESEL GENERATORS (DRESDEN UNIT 2)

Enclosed is a revfsed copy of our evaluation of Systematic Evaluation Program (SEP} Topic VIII-2. This report has been revised to reflect th~c:gmments on matters'of fact contained in your letter of February 4, 1981 *

• Your comments on diesel generator testing will be considered by the staff

• during our new generic program for the enhancement of diesel generator reliability-that is being pursued by the Power Systems Branch. Because of this new g(!neric activ-1-ty, ___ dfesel generator testing is no longer a considera-tion in the SEP.

This evaluation w111 be a basic input to the *integrated safety assessment*

for your fac111ty unless you identify changes needed to reflect the as-bu11t conditions at your facility. This topic assessment may be revised in the future if your facility design 1s changed or ff NRC criteria relating to thi_s topic are modif1~d before the 1nte9rated assessment 1s completed.

Sincerely, Dennis M. Crutchfield, Chief

- -- - -operatin~f Reactors-srancfl No:- s- -----*-.- -*- --

Df vf sion of Licensing

Enclosure:

As stated*.

cc w/enclosure:

See next p~ge *.

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OFFICIAL RECOR-0 COPY

~uSGPO: 1980-329-824

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e UNITED STATES e.

NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Docket No. 50-237

. LSOS-81-03-078 Mr. J. S. Abe 1 Director of Nuclear Licensing Corimonwealth Edison Company Post Office Box 767 Chicago, Illinois 60690

Dear Mr. Abel:

March 31, 1981

SUBJECT:

SEP TOPIC VIII-2, DIESEL GENERATORS (DRESDEN UNIT 2)

Enclosed is a revised copy of our evaluation of Systematic Evaluation Program (SEP) Topic VIII-2. This report has been revised to reflect the comments on mattersof fact contained in your letter of February 4, 1981.

Your corrunents on diesel generator testing will be considered.by the staff.

• .during our new generic program for the enhancem.ent of diesel generator rel i abi 1 ity that is being pursued by the Power Sys terns Branch.

Because of this new generic activity, diesel generator testing is no longer a considera-tion in the SEP.

This evaluation will be a basic input to the integrated safety assessment

. for your facility unless you identify changes needed to reflect the as-built conditions at your faci 1 i ty. This topic assessment may be revised in. the

.future if your facility design is changed or if NRC criteria relating *to this topic are modified before the integrated assessment is completed.

Enclosure:

As stated cc w/enclosure:

See.next page Sincerely, Lt#~ /.. UL:/,/

Dennis M. Crutch~~

• Operating Reactors Branch No. 5 Division of Licensing

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SEP TECHNICAL EVALUATION TOPIC VIII-2 DIESEL GENERATORS FINAL DRAFT DRESDEN 2 Docket No. 50-237 March 1981 F~ G. Farmer 0035J 3-2-81

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CONTENTS INTRODUCTION CRITERIA

• 2.1 2.2 2.3 Diesel Generator Loading Bypass of Protective Trips Diesel Generator Testing DISCUSSION AND EVALUATION 3.1 3.2 3.3 Diesel Generator Loading Bypass of Protective Trips Diesel Generator Testing

SUMMARY

REFERENCES 1

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SEP TECHNICAL EVALUATION TOPIC VIII-2 DIESEL GENERATORS J,

DRESDEN 2 f-j..

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1.0 INTRODUCTION

The objective of the review is to determine if the onsite AC generator for the Dresden 2 Nuclear Station has sufficient capacity and capability to supply the required automatic safety loads during anticipated occurrences and/or in the event of postulated accidents after loss of offsite power; The requirement that the onsite electric power supplies have capacity and capability to complete the required safety functions is contained in Generai Design Criterion 17.

Criterion III, "Design Control," of Appendix B, "Quality Assurance Criteri~ for Nuclear Power Plant and Fuel Reprocessing Plant," to

.* *10 CFR Part 50 'includes a requirement* that measures be provided for veri-fying or checking the adequacy of design by design reviews, by the use of*

alternate or simplified calculationa1 methods, or by the performance of ~

. suitable testing program.

Regulatory Guides, IEEE Standards, and Branch Technical Positions which provide a basis acceptable to the NRC staff for.compliance with GDCl-7

• and Criterion III include:

Regulatory Guide 1.9, "Selection of Diesel Generator Set _:Capacity for Standby Power Supplies;" Regulatory Guide 1.108,

--"Periodic Testing of Diesel Generators, Used as Onsite Power Systems at Nuclear Power Plants"; IEEE Standard 387-1977, "Criteria for

• Diesel-Generator Units Applied. as Standby Power Supplies for Nuclear Power Stations;" BTP ICSB2, Diesel-Generator Reliability Qualification Testing";

and BTP ICSB17, "Diesel Generator Protective Trip Circuit Bypasses."

Specifically, this review evaluates the loading of the diesel-generator, bypasses of protective trips during accident conditions and periodic testing.

The SEP reviews for Topics III-1 and III-12 will evaluate the diesel-generator qualification.

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2.0 - CRITERIA 2.1 Diesel Generator Loading.

Regulatory Guide 1.9, "Selection of Diesel-Generator Set Capacity for Standby Power Supplies;" provides the basis acceptable to the NRC staff for loading diesel-generator units.

The following criterion is used in this report to determine compliance with 1

current licensing requirements:

(1)

The automatically-connected loads on each diesel-generator unit should not exceed the 2000-hour rating.

(Loads must be conservatively estimated utilizing the nameplate ratings of motors and transformers with motor efficiencies of 90% or less.

When available, actual measured loads can be used.)

2.2 Bypass of Protective Trips.

Branch Technical Position (BTP)

ICSB 17, "Diesel-Generator Protective Trip Circuit Bypasses," specifies that:

(1)

The design of standby diesel generator systems should retain only the engine overspeed and the generator differential trips and bypass all other trips under an accident condition (2) If other trips, in addition to the engine over;speed and generator differential, are retained for accident con-ditions, an acceptable design should provide two or more independent measurements of each of these trip parameters.

Trip logic should be such th~t diesel-generator trip would require specific coincident logic.

2.3 Diesel Generator Testing.

Regulatory Guide 1.108, "Periodic Tesing Of Diesel Generator Units Used as Onsite Electrical Power Syste!J!s at Nuclear Power Plants", states that:

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e (1)

Testing of diesel-generator units, at least once every 18 months, should:

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(a)

Demonstrate proper startup operation by simulating loss of ;all ac voltage and demonstrate that the diesel gen~r'ator unit can start automatically and attain the required voltage and frequency within acceptable limits and time.

(b)

Demonstr1te proper operation for design-accident-

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loadin{ se_quence to design-load requirements and verify tha1t voltage and frequency are maintained within required limits.

(c)

Demonstrate full-load-carrying capability for an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, of which 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> should be at a load equivalent to the continuous rating of the diesel generator and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> at a load equivalent to the 2-hour rating of the diesel generator.

Verify that voltage and frequency requirements are maintained.

The test should also verify that the cooling system func-tions within desi.gn limits.

(d)

Demonstrate proper operation during diesel-generator load shedding, including a test of the loss of the largest single load and of complete loss of load, and verify that the voltage require-ments are met and that the overspeed, limits are not exceeded.

(e)

Demonstrate functional capability at full-load temperature conditions by rerunning the test phase outlined in (a) and (b), immediately following (c), above.

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(f)

Demonstrate the ability to synchronize the diesel generator unit with offsite power while the unit is connected to the emergency load, transfer this load to the offsite power, isolate the diesel-generator unit, and restore it to standby.status.

(g)

Demonstrate that the engine will perform properly if switching from one fuel-oil supply system to another is a part of the normal operating proced-ure to s~tisfy the 7-day storage requirement.-.

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(h)

Demonstra~e that the capability of the diesel-generator unit to supply emergency power within the required time is not impaired during periodic testing under (3), below.

(2)

Testing of redundant diesel-generator units during normal plant operation should be performed indepen-dently (nonconcurrently) to minimize common failure modes resulting from undetected interdependences among diesel-generator units.

However, during reliability demonstration of diesel-generator units during plant preoperational testing and testing subsequent to any

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plant modification where diesel-gen_erator unit inter-dependence may have been affected or every 10 years (during a plant shutdown), whichever is the shorter, a test should be conducted in which redundant units are started simultaneously to help identify certain common failure modes undetected in single diesel-generator unit tests.

(3)

Periodic testing of diesel...:generator units during nor-mal plant operation should:

(a)

Demonstrate proper startup and verify that the required voltage and frequency are automatically 4

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attained within acceptable limits and time.

This test should also verify that the components of the diesel-generator unit required for automatic startup are operable.

(b)

Demonstrate full-load-carrying capability (contin-uous rating) for an interval of not less than one hour.

The test should also verify that the cooling system functions within design limits.

This test could be accomplished by synchronizing the generator with the offsite power and assuming a load at the maximum practical rate.

(4)

The interval for periodic testing under (3), above (on a per diesel-generator unit basis) should be no more than 31 days and should depend on demonstrated perfor-mance.

If more than one failure has occurred in the last 100 tests (on a per nuclear unit basis), th~ test interval should be shortened in accordance with the following schedule:

(a)

If the number of failures in the last 100 valid tests is one or zero, the test interval should be not more than 31 days.

(b)

If the number of failures in the last 100 valid tests is two, the test interval should be not more, than 14 days.

(c)

If the number of failures in the last 100 valid tests is three, the test interval should be not more than 7 days.

(d)

If the number of failures in the last 100 valid tests is four or more, the test interval should be not more than 3 days.

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• • 3.0 DISCUSSION AND EVALUATION.

Since diesel generator loads, protective trips, and trip bypasses are.

identical for both generators, a review on one serves as a review on both.

3.1 Diesel Generator Loading Discussion.

On March 18, 1969, CECo provided i list of loads.

automatically connected to the diesel generators in the event of a LOCA 1

concurrent with a loss of offsite power

• The Safety Evaluation Report which accompanied the Provisional Operating License states that the onsite 2

power systems are acceptable (28% of capacity), which occurs The maximum step load change is 784 KW when the generators are initially loaded.

Evaluation.

Dresden 2 Technical Specifications, para-graph 4.9.A.4, requires verification, by test, of diesel generator emer-3 gency load capability during each refueling outage

• Maximum loading of the diesel generators occurs when there is a loss of off site power with a LOCA.

The total automatically connected load as shown on the licensee's load tabulation is 1950 KW, calculated at 93% motor efficiency1, or 2015 KW using 90% motor efficiency as required by Regulatory Guide 1.9.

The 2000-hour rating of the diesel generators is 2860 KW at 0.8 Power Fac-tor.

Therefore, the total automatically connected diesel generator loads (at 70% of generator capacity) are within the requirements of Regulatory Guide i. 9.

3.2 Bypass of Protective Trips Discussion.

On May 27, 1977, CECo provid.ed a list of protective trips which render the diesel generators incapable of responding to an autdmatic emergency start signal4 The protective trips which are not bypassed are generator high d_ifferential current' engine overs peed and 5

underfrequency The underfrequency trip has one frequency sensor.

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i I Evaluation.

The diesel generator underfreqency protective trip is neither bypassed during accident conditions nor provided with multiple parameter sensors and coincident logic.

Therefore, the use of this diesel I

generator protective trip during accident conditions is not in agreement with current NRC staff guidelines as listed in BTP ICSB 17.

3.3 Diesel Generator Testing Discussion.

Dresden 2 Technical Specifications, paragraph 4.9.A, required diesel-generator t~sting as follows:

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(1)

Each diesel generat@r shall be manually started and loaded once each month to demonstrate operational readiness.

The test shall continue until both the diesel engine and the generator are at equilibrium conditions of temperature while full load output is maintained.

(2)

During the monthly generator test, the diesel starting air compressor shall be checked for operation and its ability to recharge air recievers.

(3)

During the monthly generator test, the diesel fuel oil transfer pumps shall be operated.

(4)

During each refueling outage, the conditions under which the diesel generator is required will start and accept the emergency load.

If this specification has been complied with for the shared diesel generator (2/3 diesel) for Dresden Unit 3, it shall not be required for Dresden Unit 2.

Evaluation.

Diesel-generator testing defined in the plant Tech-nical Specifications address the criteria list:d in paragraph 2.3 to the following extent:

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No limits are specified for voltage, frequency,*or time*

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No limits ~re specified for voltage or frequency (c)

No limits\\ar*e specified for voltage, frequency, or duration (d)

Not addyes.';,,d (c)

Not addres:;*~J

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Not addressed (g)

Covered unJ~r-monthly test (h)

Not *address:::J (2)

Not addressed (3)

(a)

No limits specified for voltage, frequency, or time; autom.1tic-start components are.not addressed (4)

Not addressed.

The. Technical Specifications do not meet current licensing criteria for diesel-generator testing.

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SUMMARY

Automatic diesel generator loading is in compliance with current licensing criteria.

The bypass of diesel generator protective trips is not in agreement with current NRC staff guidelines.

Diesel-g~nerator testing,

. as specified by plant Technical Specifications; does not meet current 8

licensing.criteria.

The review of qualification of the diesel ~enerators will be completed with SEP Topics III-1, Seismic Qualification, :rnJ IIl-12, Environmental Qualification.

5.0 REFERENCES

1.

Safe.!=_y ___ ~l2_;2__!_ysis Repor~-'.:\\me.1dment 10, dated March 18, 196':1, Table 8.2.l.

3.

Tech~ic~~ecificati.ons and Bases for Dresden Nuclear Power Station Unit 2, June 7, 1973.

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Letter CECo (Turbak).to NEC (Davis) dated May 27, 1977, "Information Cone ern i ng Die se 1 G*.::,1.~ r a i:o rs*."

5.

CECo Drawing 12E234(l, "Standby Diesel Feed and Tie Breaker," Rev. K, dated July 14, 1976.

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General Dc::;ign Crit*~ri.on 17, "Electric Power System," of Appendix A, "General Design Crit.::r.i.n *:if Nuclear Power Pl:ints," to 10 CFR Part 50, "Domestic Licensing.Jf Production an<l Utilization Facilities."

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General Design Criterion III, "Design Control," of Appendix B, "Qual-ity Assuranc(~ Critcr tf; f.Jr Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CRF P.:irt SO, "Domestic Licensing of Production and Utilizat i.on Faciliri ::;. "

8.

"Standard Criteria f*-*r Clas:3 IE Power Systems and Nuclear Power Gener-ating Stations", IEEE Std. 308, 1974, paragraph 5.2.4.

9.

"Criteria for Diesel-Generator Units Applied as Standby Power Supplies for Nuclear Power Stations," IEEE Std. 387, 1977.

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"Selection of Diesel Ge,1erator Set Capacity for Standby Power. Sup~

plies", Regulatory.Guide 1.9.

11.

"Periodic Testing of Diesel' Generators Used as Onsite Power Systems at Nuclear Plants," Regulatory Guide 1.108.

12.

"Diesel-Generator Reli.aiJility Qualification Testing," BTP ICSl32 (PSB).

13.

"Diesel-Generator Protective Trip Circuit Bypasses," BTP ICSB17 (PSB).

14.

CECo letter (Janacek) to NRC (Crutchfield), dated February ~' 1981.

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