ML19347B200
| ML19347B200 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 08/20/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17193A073 | List: |
| References | |
| TASK-08-02, TASK-8-2, TASK-RR NUDOCS 8010100142 | |
| Download: ML19347B200 (10) | |
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SEP TECHNICAL EVALUATION TOPIC VIII-2 ONSITE EMERGENCY POWER SYSTEMS - DIESEL GENERATOR DRESDEN 2 1.0 INIRODUCTION 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 General Design Criterion 17.
Criterion III, " Design Control," of Appendix B, " Quality Assurance Criteria 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 calculational methods, or by the performance of a suitable testing program.
Regulatory Guides, IEEE Standards, and Branch Technical Positions which provide a basis acceptable to the NRC staff for compliance with GDC17 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 111-1 and 111-12 will evaluate the diesel generator qualification.
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a 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 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 Bvg;ss of Protective Trips. Branch Technical Position (BTP)
ICSB 17, " Diesel-Generator Protective Trip Circuit Bypasses," speci fies that:
I (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 overspeed 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 that diesel-generator trip would require specific coincident logic.
2.3 Diesel Generator Testing. Regulatory Guide 1.108, " Periodic Tesing of Diesel Generator Unita Used as Onsite Electrical Power Systems at Nuclear Power Plants", states that:
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e (1) Testing of diesel-generator units, at least once every 18 months, should:
(a) Demonstrate proper startup operation by simulating loss of all ac voltage and demonstrate that the diesel generator unit can start automatically and attain the required voltage and frequency within acceptable limits and time.
(b) Demonstrate proper operation for design-accident-
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loading sequence to design-load requirements and verify that 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 cdhtinuous 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 racing of the diesel generator. Verify that voltage and frequency requirements are maintained. The test should also verify that the cooling system func-1 tions within design limits.
(d) Demonstrate proper operation during diesel-generator load shedding, including a test of the
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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 cerunning the test phase outlined in (a) and (b), immediately following (c), above.
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(f) Demonstrato th2 ability to synchronizs tha discal generator unit with offsite power while the unit is connected to the emergency load, transfer this load to the offsit: 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 satisfy the 7-day storage requirement.
(h) Demonstrate that the capability of the diesel-j generator unit to supply emergency power within the required time is not impaired during periodic
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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 plant modification where diesel-generator 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 1
required voltage and frequency are automatically 4
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o attained within acceptable limits and time. This test should also verify that the components of t.he 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), the 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 j
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 EVA2.UATION 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 D~scussion. On March 18, 1969, Ceco provided a list of loads automatically connected to the diesel generators in the event of a LOCA I
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.
The maximum step load change is 784 KW (28% of capacity), which occurs 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-gency load capability during each refueling outage. Maximum loading of the diesel generators occurs when there is a loss of offsite power with a LOCA. The total automatically connected load as shown on the licensee's 1
load tabulation is 1950 KW, calculated at 93% motor ef ficiency, or 2015 KW using 90% motor efficiency as required by Regulatory Guide 1.9.
The 2000-hour rating of the diesel generators is 2850 KW at 0.8 Power Fac-tor.
Therefore, the total automatically connected diesel generator loads (at 71% of generator capacity) are within the requirements of Regulatory Guide 1.9.
3.2 Bypass of Protective Trips Discussion. On May 27, 1977, CECO provided a list of protective trips which render the diesel generators incapable of responding to an automatic emergency start signal.
The protective trips which are not bypassed are generator high differential current, engine overspeed and 5
underfrequency.
The underfrequency trip has one frequency sensor.
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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 generator protective trip during accident conditions is not in agreement with current NRC staf f guidelines as listed in BTP ICSB 17.
3.3 Diesel Generator Testing Discussion. Dresden 2 Technical Specifications, paragraph 4.9.A, required diesel-generator testing as follows:
(1) Each diesel generator 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, ch'e 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.
1 (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 listed in paragraph 2.3 to the following extent:
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(1)
(c) Na linics cro sp;cificd for voltega, frequincy, cr
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time (b) No limits are specified for voltage or frequency (c) No limits are specified for voltage, frequency, or duration (d) Not addressed (e) Not addressed (f) Not addressed (g) Covered under monthly test (h) Not addressed (2) Not addressed (3)
(a) No limits specified for voltage, frequency, or time; automatic-start components are not addressed (4) Not addressed.
The Technical Specifications do not meet current licensing criteria for diesel-generator testing. Diesel-generator failure data will be extracted by NRC from Licensee Event Reports and will be considered in the final evaluation of testing adequacy.
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SUMMARY
Automatic diesel generator loading is in conpliance with current licensing criteria. The bypass of diesel generator protective trips is not in agreement with current NRC staff guidelines. Diesel-generator testing, as specified by plant Technical Specifications, does not meet current 8
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lic:nsing critsria. Th3 review of qualificatica of tha dissal gtnsrctors
>ill be completed with SEP Topics III-1, Seismic Qualification, and III-12, Environmental Qualification.
5.0 REFERENCES
1.
Safety Analysis Report, Amendment 10, dated March 18, 1969, Table 8.2.1.
2.
Safety Evaluation Report, dated October 17, 1969, page 21.
3.
Technical Specifications and Bases for Dreaden Nuclear Power Station Unit 2, June 7, 1978.
4.
Letter CECO (Turbak) to NRC (Davis) dated May 27, 1977, "Information Concerning Diesel Generators."
5.
Ceco Drawing 12E2346, " Standby Diesel Feed and Tie Breaker," Rev. K, dated July 14, 1976.
6.
General Design Criterion 17, " Electric Power System," of Appendix A,
" General Design Criteria of Nuclear Power Plants," to 10 CFR Part 50,
" Domestic Licensing of Production and Utilization Facilities."
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7.
General Design Criterion III, " Design Control," of Appendix B, " Qual-ity Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CRF Part 50, '* Domestic Licensing of Production and Utilization Facilities."
,8.
" Standard Criteria for Class IE Power Systems and Nuclear Power Gener-e 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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10.
"S91cetica of Diessi G:nsretor Sct Ccpreity for Stendby Powar 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 Reliability Qualification Testing," BTP ICSB2 (PSB).
13.
" Diesel-Generator Protective Trip Circuit Bypasses," BTP ICSB17 (PSB).
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