ML20214T308

Proposed Tech Spec Pages 5.6-1 & 5.6-2,changing Frequency of Standby Diesel Generator Surveillance.Safety Evaluation & Significant Hazards Consideration Encl

ML20214T308
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/24/1986
From:	PUBLIC SERVICE CO. OF COLORADO
To:
Shared Package
ML20214T282	List: ML20214T280 ML20214T300 ML20214T308
References
TAC-63029, NUDOCS 8609300257
Download: ML20214T308 (8)

Text

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• Fort St. Vrain #1 Technical Sp:cifications Amendment Page 5.6-1 5.6 EMERGENCY POWER SYSTEMS - SURVEILLANCE REQUIREMENTS A_pplicability Applies to the surveillance of the equipment supplying electrical power to the essential plant services.

Objective To establish the minimum frequency and type of surveillance for equipment supplying electric power to the olant auxiliaries to ensure that the motive power sources required to safely shut down the plant are available.

Specification SR 5.6.1 - Standby Diesel Generator Surveillance The surveillance of the standby diesel generators shall be as follows:

a) Each standby generator set will be started and loaded to at least 50". of rated full load capacity once per week.

The test shall continue for at least two hours to enable the engine (s) and the generator to Ettain their normal operating temperatures.

b) A loss of outside source of power and turbine trip shall be simulated to demonstrate that the standby generators and automatic cont: ol s are operable. This Surveillance Requirement shall be performed at least once per 6 months with a maximum allowable extension of 2 months per surveillance interval such that the maximum combined time interval for 3 consecutive surveillance intervals shall not exceed 20 months.

c) The diesel engine protection functions shall be calibrated annually.

, d) The diesel engine exhaust temperature " shutdown" and i

"declutch" shall be functionally tested monthly and calibrated annually.

8609300257 860924 PDR P ADOCK 05000267 pyg

Fort St. Vrain #1 Technical Sp;cifications Amendment Page 5.6-2 e) A loss of outside source of power and turbine trip shall be sinulated at least once per refueling cycle, not to exceed eighteen (18) months, to demonstrate that the stancby generators, automatic controls and load sequencers are operable. This surveillance may be performed in lieu of SR 5.6.1.b above.

Basis for Specification SR 5.6.1 The purpose of the weekly test of the standby diesel generator is to exercise the engine by operating at design temperature and to demonstrate operating capability. These tests will allow for '

detection of deterioration and failure of equipment.

The purpose of the loss of outside source of power and turbine trip test (SR 5.6.1.b), performed twice annually is to verify that the standby generator (s) are capable of starting automatically upon a simulated loss of outside power and turbine trip. SR 5.6.1.e, performed at refueling intervals, verifies the same features as SR 5.6.1.b but, additionally, verifies that the load sequencers automatically pick up required loads in the event of a loss of voltage on the 480V essential buses.

Specification SR 5.6.2 - Station Battery Surveillance The surveillance of the station and PPS batteries shall be as follows:

a) The specific gravity and voltage of the pilot cell and tamperature of adjacent cells and overall battery voltage shall be measured every week.

b) The specific gravity and voltage to the nearest 0.01

/ volt, temperature of every fif th cell and height of electrolyte shal! be measured every three months.

s c) The station and PPS batteries shall be load-tested to partial discharge once a year during plant shutdown.

Basis for Specification SR 5.6.2 The type of battery surveillance called for in this specification has been demonstrated through experience to provide a reliable indication of a battery cell initial breakdown well before it becomes unserviceable. Since batteries will deteriorate with time, these periodic tests will avoid precipitious failure.

The marufacturer's recommendation for equalizing charge is vital to maintenance of the ampere-hour capacity of the battery. As a check upon the effectiveness of this charge, each battery will be load tested to determine its ampere-hour capacity. In addition, its voltage shall be monitored as a function of time. If a cell has deteriorated or if a connection is locse, the voltage under load will drop excessively, indicating need for replacement er maintenance.

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Attachment 3 I f i

! SAFETY EVAL.UATION t

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Attachment 3 to P-86549 Safety Evaluation The surveillance requirements for the standby generators incorporate periodic testing and surveillance to verify the capability of the standby generators to perform as an emergency power source for essential loads. On a weekly test basis, the standby generators are started from ambient conditions and manually loaded to at least 50%

rated full load capacity for at least two hours. Diesel engine protective functions are calibrated annually. Diesel engine exhaust temperature " shutdown" and "declutch" functions are tested monthly and calibrated annually.

In addition to the above tests, the standby generators are tested twice annually with respect to their " system design function" as

. verification of the overall electrical system reliability for the Fort St. Vrain nuclear generating station.

That is, the standby generators function as an emergency source of electrical power to essential loads in the event of a loss of power to the essential buses.

Public Service Company of Colorado proposes to verify the operability of the standby generators while minimizing unnecessary surveillance shutdowns between refueling intervals.

Reliability of the electrical system and loads on the electrical system are enhanced by minimizing electrical system disturbances ac j maintaining steady state electrical system parameters. Additionally, minimizing reactor plant startups and shutdowns enhances overall plant reliability by maintaining steady state conditions and avoiding thermal cycling of the PCRV, piping and other high energy systems.

At present, a severe electrical disturbance to the electrical system is deliberately induced twice annually to verify that the standby generators will automatically start and pick up essential loads. The probability of electrical malfunctions and/or system upsets is increased due to loss of voltage and subsequent reenergization of dead buses. While it is desirable to veri fy that capability periodically, system upsets should be minimized. The standby generators can be verified as a reliable emergency power source with a high degree of confidence by observing that they start automatically upon a simulated loss of power to the buses at least once per 6 months as presently prescribed by the Technical Specifications with some allowance for operations scheduling.

Additionally, to provide that extra degree of confidence, the load sequencers would be verified operable at least once per refueling cycle when the plant is shutdown. The overall confidence in the emergency power source function of the standby generators is not- in question. The potential consequences of a severe power disruption are, however, minimized.

Verification that the standby generators respond automatically to a simulated loss of power signal using installed and normally operating circuits provides high confidence that the system will perform as designed. Thus, the twice annual performance of.the loss of outside source of power and turbine trip without stripping essential buses of their normal loads and sequencing on of essential loads maintains the desired high confidence level that the standby generators start in response to the low voltage condition.

However, the refueling cycle surveillance test will verify overall electrical system operability but with minimal impact to plant systems and components due to its less frequent system perturbation.

Overall system reliability is expected to be enhanced as potential failure mechanisms associated with power disruptions are reduced.

Consideration of the proposed changes to standby diesel surveillance involves evaluation of accidents or equipment functions previously 4

evaluated in the FSAR. As required by 10CFR50.59, the following questions are addressed:

1) Has the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety previously evaluated in the FSAR been increased?

As the direct result of reducing the frequency of load shedding and reenergizing essential loads with the standby.

generators, no abnormal modes of plant operation are required. Potential failure mechanisms associated with power disruption are- in fact, reduced. Thus, the probability of occurrence or consequences of an accident or

~ ' equipment malfunction previously evaluated in the FSAR has not been increased.

2) Has che possibility of an accident or malfunction of a different type than any evaluated previously in the FSAR been created?-

No. As discussed above, the surveillance test presently performed twice annually will be rescheduled to a refueling cycle interval. The standby generators will still be l started twice annually to verify automatic start capability i upon simulated loss of outside power and turbine trip. No j new tests or tests of a different type are proposed.

3) Has the margin of safety, as defined in the basis for any Technical Specification been reduced?

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No. The emergency power source system (standby generators

, and associated circuits) is not changed as a result of the i proposed Technical Specification change.

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Public Service Company of Colorado concludes that the operability of the standby generators is verified by the proposed surveillance j testing. The severe power disruption caused by stripping essential l buses of loads and reenergizing these loads with the standby l generators is reduced to one-half to one-third of the the previous license interval in these proposed Technical Specifications changes.  :

PSC considers these changes to be an improvement in overall plant l reliability as the result of minimizing electrical power disruptions j

.and plant startups and shutdowns. Thus, these proposed changes to  :

the Fort St. Vrain Technical Specifications do not result in an unreviewed safety question. l

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l Attachment 4

> l l SIGNIFICANT HAZARDS CONSIDERATION 1

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Attachment 4 to P-86549 SIGNIFICANT HAZARDS CONSIDERATION I. Evaluation Based upon the safety evaluation provided as Attachment 3 to this i

Technical Specification change, it is concluded that the change in frequency of testing the standby generators involving actual load I shedding and reenergizing loads taken together with the total

proposed surveillance testing verifies standby generator operability.

'It is further concluded that the proposed changes do not result in- ,

an unreviewed safety question.

1. Neither the probability nor consequences of accidents previously evaluated have been affected by this proposed Technical Specification change. The frequency of performing a surveillance presently required is reduced. from twice annually to once per refueling cycle. An emergency diesel generator surveillance verifying automatic start and run features but not requiring load shedding _and subsequent a

reenergization of loads is still proposed to be performed  ;

! twice annually. Thus, standby generator operability is

! affirmed semiannually.by proper operation of the loss of power sensing circuits and auto-start capabilities of the standby generators.

2. The possibility of a new or oifferent kind of accident from those previously evaluated has not been introduced. The

, proposed testing still verifies diesel generator operability using previously used and understood tests but reduces the frequency of power disruptions to essential loads.

3. No margins of safety have been reduced as a result of the proposed surveillance changes. The proposed changes in surveillance testing involve testing already performed with plant effects well understood.

II. Conclusion d

Based on the evaluation provided above, it is concluded that operation of Fort St. Vrain in accordance with the proposed changes

will not (1) involve a significant inci9ase in the probability or consequences of an accident previously eva'uated, (2) create the possibility of a new or different~ kind of actident from any accident previously evaluated, or (3) involve a significant reduction in any margin of safety._ Therefore this change will ne

ther create an undue risk to the health and safety of the public nor involve any significant hazards consideration.

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