Regulatory Guide 1.108

Periodic Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants

ML12216A011
Person / Time
Issue date:	08/31/1977
From:	NRC/OSD, Office of Nuclear Regulatory Research
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References
RG-1.108, Rev.1
Download: ML12216A011 (4)

Revision I

U.S. NUCLEAR REGULATORY COMMISSION August 1977 REGULATORY GUIDE

OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 1.108 PERIODIC TESTING OF DIESEL GENERATOR UNITS

USED AS ONSITE ELECTRIC POWER SYSTEMS

AT NUCLEAR POWER PLANTS

A. INTRODUCTION

features if a loss of offsite power and an accident oc- cur during the same time period and (2) to provide Criterion XI, "Test Control," of Appendix B, power to equipment needed to maintain the plant in a

"Quality Assurance Criteria for Nuclear Power safe condition if an extended loss of offsite power oc- Plants and Fuel Reprocessing Plants," to 10 CFR curs. Diesel generator units are the most common Part 50, "Licensing of Production and Utilization source of onsite electric power.

Facilities," requires that a test program be es- tablished to ensure that systems and components per- High reliability must be designed into the diesel form satisfactorily and that the test program include generator units and maintained throughout their ser- operational tests during nuclear power plant opera- vice lifetime by appropriate testing, maintenance, and tion. operating programs. Branch Technical Position EICSB 2, "Diesel-Generator Reliability Qualifica- Criterion 17, "Electric Power Systems," of Appen- dix A, "General Design Criteria for Nuclear Power tion Testing," dated 11/24/75, of the Standard Plants," to 10 CFR Part 50 requires that onsite Review Plan (Appendix 7-A of NUREG-75/0871) es- electric power systems have sufficient independence, tablishes a reliability goal of 0.99 (at a nominal 50%

confidence level) and an acceptable qualification capacity, redundancy, and testability to perform their testing program for diesel generator units of a type or safety functions, assuming a single failure.

size not previously used as standby emergency power Criterion 18, "Inspection and Testing of Electric sources in nuclear power plants. The preoperational Power Systems," of Appendix A to 10 CFR Part 50 and periodic testing provisions set forth in this guide requires that electric power systems important to have been designed to provide a basis for taking those safety be designed to permit appropriate periodic in- corrective actions needed to maintain high inservice spection and testing to assess the continuity of the. reliability of installed diesel generator units. In addi- systems and the coindition. of their components. tion, the data developed will provide an ongoing demonstration of performance and reliability for all This regulatory guide describes a method accep- diesel generator, units after installation and in service.

table to the NRC staff for complying with the Com- Reliability objectives concerning the entire onsite mission's regulations with regard to periodic testing electric power system's probability of failure depend of diesel electric power units to ensure that the diesel on the interconnections among the system's compo- electric power systems will meet their availability re- nents and are not within the scope of this guide.

quirements. The Advisory Committee on Reactor "Failure" is taken here to mean the failure to start, accelerate, and assume the design-rated load within

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Safeguards has been consulted concerning this guide and has concurred in the regulatory position. and for the time prescribed during an emergency or a valid test.

B. DISCUSSION

I NUREG-75/087, "Standard Review Plan for the Review of The purposes of onsite electric power systems are Safety Analysis Reports for Nuclear Power Plants," U.S. Nuclear

(1) to provide power promptly to engineered safety Regulatory Commission. Copies may be purchased from the National Technical Information Service, Springfield, Virginia

• Lines indicate substantive changes from previous issue. 22161.

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The testing of the diesel generator unit should also be provided between diesel generator unit testing simulate, where practicable, the parameters of opera- locations and the main control room to ensure that tion (automatic start, load sequencing, load shed- the operators are cognizant of the status of the unit ding, operation time, etc.) and environments under test.

(temperature, humidity, etc.) that would be expected if actual demand were to be placed on the system. (5) The surveillance system should indicate which of the diesel generator protective trips is ac- This guide provides design and operational provi- tivated first in order to facilitate trouble diagnosis.

sions for the performance of periodic testing of diesel generator units used for onsite electric power for (6) All diesel generator protective trips should nuclear power plants. A "diesel generator unit" con- sists of the engine, generator, combustion air system, be in force during diesel generator unit testin

g. I

cooling water system up to the supply, fuel supply c. Detailed step-by-step procedures should be system, lubricating oil system, starting energy provided for each test under Regulatory Position C.2.

sources, autostart controls, manual controls, and The procedures should identify those special arrange- diesel generator breaker. ments or changes in normal system configuration that must be made to put the diesel generator unit un-

C. REGULATORY POSITION

der test. Jumpers and other nonstandard configura- tions or arrangements should not be used subsequent

1. General to initial equipment startup testing.

a. The design of a diesel generator unit should be d. Subsequent to any failure, the cause should be such that it can accommodate diesel generator testing determined and corrective action taken in a timely as defined in Regulatory Position C.2. manner, with emphasis on preventing reoccurrence of the failure.

b. Diesel generator units should be designed to be testable during operation of the nuclear power plant, 2. Testing as well as while the plant is shut down. The design should include provisions so that the testing of the a. Testing of diesel generator units during the units will simulate the parameters of operation plant preoperational test program and at least once (outlined in Regulatory Position C.2) that would be every 18 months should:

expected if actual demand were to be placed on the system. (1) Demonstrate proper startup operation by simulating loss of all a.c. voltage and demonstrate

(1) Capability should be provided to test each that the diesel generator unit can start automatically diesel generator unit independently of redundant un- and attain the required voltage and frequency within its. Test equipment should not cause a loss of in- acceptable limits and time.

dependence between redundant diesel generator units or between diesel generator load groups. (2) Demonstrate proper operation for design- accident-loading-sequence to design-load require-

(2) Testability should be considered in the selec- ments and verify that voltage and frequency are tion and location of instrumentation sensors and maintained within required limits.

critical components (e.g., governor, starting system components). Instrumentation sensors should be (3) Demonstrate full-load-carrying capability readily accessible and designed so that their inspec- 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 tion and calibration can be verified in place. hours should be at a load equivalent to the con- Testability should be considered in selecting critical tinuous 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 components, and the overall design should include load equivalent to the 2-hour rating of the diesel status indication and alarm features. generator. Verify that voltage and frequency require- ments are maintained. The test should also verify that

(3) Periodic testing of diesel generator units the cooling system functions within design limits.

should not impair the capability of the unit to supply emergency power within the required time. Where (4) Demonstrate proper operation during diesel necessary, diesel generator unit design should include generator load shedding, including a test of the loss an emergency override of the test mode to permit of the largest single load and of complete loss of load, response to bona fide signals. and verify that the voltage requirements are met and that the overspeed limits are not exceeded.

(4) A surveillance system should be provided (5) Demonstrate functional capability at full- with remote indication in the control room as to load temperature conditions by rerunning the test diesel generator unit status, i.e., under test, ready- phase outlined in Regulatory Positions C.2.a.(l) and standby, lockout. A means of communication should (2) above immediately following (3) above.

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(6) Demonstrate the ability to (a) synchronize C.2.a.(9), the interval for periodic testing under the diesel generator unit with offsite power while the Regulatory Position C.2.c (on a per diesel generator unit is connected to the emergency load, (b) transfer unit basis) should be no more than 31 days and this load to the offsite power, (c) isolate the diesel should depend on demonstrated performance. If generator unit, and (d) restore it to standby status. more than one failure has occurred in the last 100

tests (on a per nuclear unit basis), the test interval

(7) Demonstrate that the engine will perform should be shortened in accordance with the following properly if switching from one fuel oil supply system schedule.:

to another is a part of the normal operating procedure to satisfy the 7-day storage requirement. (I) If the number of failures in the last 100 valid tests is one or zero, the test interval should be not

(8) Demonstrate that the capability of the diesel generator unit to supply emergency power within the more than 31 day

s. I

required time is not impaired during periodic testing (2) If the number of failures in the last 100 valid under Regulatory Position C.2.c. tests is two, the test interval should be not more than

14 days.

Demonstrate the required reliability by

.(9)

means of any 69 consecutive valid tests2 (per plant) (3) If the number of failures in the last 100 valid with no failures, with a minimum of 23 or 69/n tests, tests is three, the test interval should be not more whichever is the larger, per diesel generator unit than 7 days.

(where n is equal to the number of diesel generator units of the same design and size). (4) If the number of failures in the last 100 valid tests is four or more, the test interval should be not b. Testing of redundant diesel generator units more than 3 days.

during normal plant operation should be performed independently (nonconcurrently) to minimize com- e. Valid tests and failures (under Regulatory mon failure modes resulting from undetected in- Positions C.2.a.(9) and C.2.d) should be based on the terdependences among diesel generator units. following criteria:

However, during reliability demonstration of diesel

(1) All start attempts (automatic, including generator units during plant preoperational testing those from bona tide signals, or manual) that result in and testing subsequent to any plant modification a failure to start, except as noted in (2) below, should where diesel generator unit interdependence may be considered valid tests and failures.

have been affected or every 10 years (during a plant shutdown), whichever is the shorter, a test should be (2) Unsuccessful start and load attempts that conducted in which redundant units are started can definitely be attributed to operating error, to simultaneously to help identify certain common spurious operation of a trip that is bypassed in the failure modes undetected in single diesel generator emergency operating mode, to malfunction of equip- unit tests. ment that is not operative in the emergency operating mode (e.g., synchronizing circuitry) or is not part of c. Periodic testing of diesel generator units during the defined diesel generator unit design should not be normal plant operation should: considered valid tests or failures.

(1) Demonstrate proper startup and verify that (3) Successful starts, including those initiated by the required voltage and frequency are automatically bona fide signals, followed by successful loading (se- attained within acceptable limits and time. This test quential or manual) to at least 50% of continuous should also verify that the components of the diesel rating and continued operation for at least one hour generator unit required for automatic startup are should be considered valid successful tests.

operable.

(4) Successful starts that are terminated inten-

(2) Demonstrate full-load-carrying capability tionally without loading, as defined in (3) above, (continuous rating) for an interval of not less than should not be considered valid tests or failures.

one hour. The test should also verify that the cooling system functions within design limits. This test could (5) Successful starts followed by an unsuccessful be accomplished by synchronizing the generator with loading attempt should be considered valid tests and the offsite power and assuming a load at the max- failures, except as noted in (2) above.

imum practical rate.

(6) Tests that are terminated intentionally d. After completion of the diesel generator unit before completion as defined in (3) above because of reliability demonstration under Regulatory Postition an alarmed abnormal condition that would ultimate- ly have resulted in diesel generator damage or failure

2 Valid test as defined in Regulatory Position C.2.e. should be considered valid tests and failures.

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(7) Tests performed in the process of generator units requires special evaluation, and the troubleshooting should not be considered valid tests. information provided on the report form should be Tests that are performed to verify correction of the supplemented, as needed, by additional narrative problem should be considered valid tests and succes- material that:

ses or failures, as appropriate.

(1) Identifies the reported failure as the 7th or

(8) Cranking and venting procedures that lead greater failure in the last 100 valid tests, to the discovery of conditions (e.g., excessive water or oil in a cylinder) that would have resulted in the (2) Describes corrective measures, taken or failure of the diesel generator unit during test or dur- planned, to increase the reliability of the generator ing response to a bona fide signal should be con- units, sidered a valid test and failure.

(3) Provides an assessment of the existing

3. Records and Reports reliability of electric power to engineered-safety- ieature equipment, a. All start attempts, including those from bona fide signals, should be logged. The log should (4) Provides the licensee's basis for continued describe each occurrence in sufficient detail to permit plant operation if that is planned, and independent determination of statistical validity in accordance with Regulatory Position C.2.e. (5) Provides a summary of all tests (valid and in- Maintenance, repair, and out-of-service-time valid) that occurred within the time period over histories, as well as cumulative maintenance and which the last 100 valid tests were performed, and operating data, should also be logged. Cumulative verifies that surveillance testing during this period statistical analyses of diesel generator unit test was in conformance with the schedule of Regulatory results, together with results of operation of the diesel Position C.2.d.

generator unit when required by actual demand, should be maintained. These analyses should include Invalid failures experienced during trouble- examination of the trend of critical failure shooting should be included in the report of the mechanisms, human errors, and common mode failure (valid or invalid) that made the troubleshooting necessary.

failures.

b. All diesel generator unit failures, valid or in- valid, should be reported3 consistent with the

D. IMPLEMENTATION

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licensee's reporting requirements. This report should The purpose of this section is to provide informa-

(1) identify the diesel generator unit involved, (2) tion to applicants regarding the NRC staffs plans for identify the failure as being the nth f'ailure in the last using this regulatory guide.

100 valid tests, (3) describe the cause of failure, (4)

describe the corrective measures taken, (5) indicate This guide reflects current NRC staff practice.

the length of time the diesel generator unit was un- Therefore, except in those cases in which the appli- available, (6) define the current surveillance test inter- cant proposes an acceptable alternative method for val, and (7) verify that the test interval is in confor- complying with the specified portions of the Commis- mance with the schedule of Regulatory Position sion's regulations, the method described herein is be- C.2.d. If the number of failures in the last 100 valid ing and will continue to be used in the evaluation of tests is seven or more, the reliability of the diesel submittals for construction permit applications until

' See Regulatory Guide 1.16, "Reporting of Operating Infor- this guide is revised as a result of suggestions from the mation." public or additional staff review.

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