ML17347A205

SER Accepting Util 860612 & 0716 Emergency Diesel Generator Load Evaluation

ML17347A205
Person / Time
Site:	Turkey Point
Issue date:	12/15/1986
From:	NRC
To:
Shared Package
ML17347A204	List: ML17347A203 ML17347A205
References
TAC-61211, TAC-61212, NUDOCS 8612180404
Download: ML17347A205 (18)

Text

ENCLOSURE I SAFETY EVALUATION REPORT TURKEY POINT PLANT, UNITS 3 AND 4 DOCKET NOS.50-25O ANn 50-251 (TAC NOS.

61211 AND 61212)

BACKGROUND In December 1985, Florida Power and Light (FP8 L) informed the staff (LEP 85-04?)

that an emergency diesel generator (EDG) overload problem may exist during a

design basis event at the Turkey Point site.

The concern is that insufficient EDG capacity is available to accommodate the potential maximum EDG loading levels required for certain operational and/or accident conditions.

In letters dated

~brune 12 and July 16, 1986, FP8L provided to NRC an EDG load evaluation detailing the EDG loads, the EDG capabilities and ratinqs, and the effects and corrective actions to be taken during a loading sequence.

The proposed corrective actions consist of manually applyina nr removing plant system loads to accommodate the defined loading requirements within the EDG ratings.

These are listed as follows:

0 Secure a

RHR pump on the accident unit at 30 minutes.

Disable the auto-connect feature of the Instrument Air Compressors (IACs).

Disable the ability of the IACs to reload upon Safety Injection Signal (SIS) reset.

Provide EDG independent IACs.

(Equipment to support IAC operation will also be EDG independent.)

Disable the ability of turbine-related loads to reload upon SIS reset on both units.

4. Sbi>~~

'00 0>000gSO a>~

>OaCW Zog P

1

Initiate the Computer Room/Cable Spreading Room (CR/CSR) Air Conditioning (AC) function after one hour.

Provide Computer Room temperature indication in the Control Room.

Disable the auto-connect feature of the Normal Containment Coolers (NCCs) on the non-accident unit.

Upgrade, as required, NCCs and support equipment for operation at elevated temperature.

Secure a Containment Spray (CS) pump at 30 minutes and maintain two Emergency Containment Coolers (ECCs) running beyond 30 minutes.

Disable the auto-connect of boric acid-related loads (except heat tracing) when two EDGs start and operate.

The staff has reviewed the FP&L EDG load evaluation submittals for assessing the operational and accidents conditions at the two units, containment pressure and temperature conditions, diesel engine and diesel generator electrical capability and human factors considerations.

These assessments are based on the information provided in the licensee's submittals on EDG load evaluation and several telecon discussions with the licensee.

EVALUATION.AND ANALYSIS Diesel Generator Electrical Capability An emergency diesel generator (EDG> load evaluation conducted in December

1985, hy Florida Power and Light (FP&L) indicated that the EDG load capabilities were not at an acceptable level due to the identification of additional loads.

These loads could not be accommodated within the EDG loading limits without some corrective actions.

These corrective actions consisted of manually droppinq and/

or adding plant system loads in order to keep EDG(s> loading within defined limits.

The load limits established for the EDG(sl at Turkey Point are transient, short-term continuous and auto-connect.

During post-LOCA load management activities, loads must be added and/or dropped from the EDG(s).

This EDG load limit is set at 2950 KW and is referred to as the transient load limit.

The short-term continuous load limit is set at 2850 KW and refers to the 2000 MR rating.

The auto-connect load limit is set at 2750 KW and refers to the cold start loading of the EDG at the onset of LOCA with loss of off-site power.

The 2950/2850 KW load limit philosophy has been incorporated in the revised plant emergency procedures to alert the plant operators to avoid exceeding the 2950 KW EDG limit.

The load limits are well within the manufacturers recom-mended rating of the EDG(s).

The current Turkey Point Technical Specifications require periodic testing and surveillance to veriFy that the auto-connected loads to each diesel generator do not exceed 2750 KW.

The supplier of the Turkey Point EDG has tested the EDG engine at 2950 KW for about 30 minutes.

Additional testing of the same type EDG enqine has been performed at other installations at loads up to 3050 KW.

Based on the information provided by the licensee, it appears that the loads for various operating and accident conditions with the proposed manual corrective actions are within the 30 minute and continuous rating of the EDG.

This con-forms to the guidance of R.G.

1.9 Position P..

Diesel Enqine Capability The corrective actions addressed in the FP8L evaluation (Submittal of June V.,

1986) detailed the plant system loads that would be manually dropped and/or added during the first hour of an accident.

One of the proposed corrective actions is that the Computer Room/Cable Spreading Room Air Conditioning (AC} would not be initiated until one (1) hour into the accident.

Since certain safety related control systems are located in this area, the staff was concerned that the ambient room temperature would exceed the equipment design temperature prior to AC system initiation.

The 'licensee, in the luly 16, 1986 letter, provided the results of tests and analyses which showed that with an initial room temperature of 77'F and the outside ambient temperature at the design limit, the room temperature at the time of AC initiation would not exceed 90 F which is the design temperature limi-tation for the Safety Assessment System.

The failure modes and effects analysis provided with the EM Load Evaluation showed that for a failure to open of Motor Control Center (MCC) D, 3A, or 4A tie breaker, the auto-connected loads on the EOG would exceed the short-term continuous (2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />) rating of 2850 KW of the EDA for a short time (less than 30 minutes),

but would not exceed the Transient Rating of ?95O Kll.

The auto-connect loads for this event are well within the recommended manufacturer's load limitations for short duration loads (4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and 5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> load limitations).

Based on the manufacturer's recommendations and the results of tests on EGG's of the same model as Turkey Point at various overload conditions, the staff concludes that the short duration EDG over loading as a result of an MCC tie breaker <ailure is within the design capabilities of the diesel engine and will not result in an emergency diesel engine failure.

Loss of Coolant Accident (LOCA)

A postulated loss of coolant accident in one unit would produce the largest single unit power demand.

The staff does not postulate simultaneous accidents at both units.

Therefore, the largest non-accident demand at the other unit was evaluated.

This would occur if the non-accident unit were shutdown with the RHR system in operation to remove core decay heat.

The licensee has revised the plant emergency operating procedures to reduce the EDG power requirements.

Since the diesels are capable of operating with an overload for brief periods (30 minutes),

the revised procedures will allow for increased loading for the first 30 minutes and then allow for a reduction in the operating equipment after 30 minutes.

This would be accomplished in a manner that is consistent with the plant's safety analysis.

In'he event of a loss of coolant accident at one unit with the other unit

shutdown, and if offsite power were lost, the safeguards equipment at the accident unit would be loaded automatically on the emergency bus.

The decay heat removal equipment at the shutdown unit would be loaded manually.

The necessary equipment at the non-accident unit includes an intact Cooling Water

pump, a Component Cooling Mater pump and an RHR pump.

To minimize power demand on the emergency power bus in the event that only one emergency diesel were operating, restart of RHR at the non-accident unit will be delayed for as long as 30 minutes.

A 30 minute delay would be acceptable if the non-accident unit had been shutdown for as long as 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

At 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> after shutdown decay heat levels would be sufficiently low that RHR design limits would not be exceeded during a

30 minute interruption of decay heat removal.

If the reactor had been shutdown for less than 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />, the RHR might have to be loaded on the emergency power bus in less than 30 minutes.

Tn reduce the electrical

lnad, control room cooling will be reduced to the minimum level required to maintain environmental and habitability limits.

~

4

~ 4 At the unit with the loss of coolant accident the electric load would be greatest for the initial injection phase.

The injection phase would normally extend about 30 minutes for a large break LOCA; however, core reflooding would occur much earlier.

For small break LOCAs the injection phase would extend longer than 30 minutes.

Low pressure ECCS pumps are not required to mitigate

- small break LOCAs.

For either smaller or large break LOCAs the RHR pumps are not required to inject after an initial 30 minutes has passed since ample flow is provided by the high pressure injection pumps.

To ensure that an overload condition would not occur for a single operating emergency diesel for a period of longer than 30 minutes, at 30 minutes following a loss of coolant accident the emergency procedures will instruct the operator to secure the operating RHR pump.

The RHR pump at 30 minutes followinq a LOCA would be taking suction from the RWST.

Containment spray would also be secured afte~ 30 minutes.

Two high head Safety Injection pumps would be operated during the entire injection phase consistent with the safety analysis for small break LOCA.

For the large break LOCA, the core would be recovered by 30 minutes following the break and flow from the two high head pumps would be more than adequate to make up for core boil off.

Securing an RHR pump after 30 minutes into the iniection period not only reduces the emergency power requirement but permits a longer injection period.

The Turkey Point plants are equipped with reactor vessel water level indication equipment.

If inadequate core cooling were indicated, additional ECCS pumps could be reactivated.

At the end of the iniection period one RHR pump would be reactivated in the sump recirculation mode.

One of the two high head injection pumps would be deactivated and the other pump connected with its suction to the RHR pump discharge for continued small break LOCA protection during the recirculation periods.

These measures are consistent with the plant safety analysis for single ECCS train operation following a LOCA.

Revised Containment Pressure and Temperature For the scenario where one Emergency Diesel Generator (EDG) is operating during a

LOCA, the revised plant procedures will allow the operator to secure the operating containment spray pump thirty minutes after onset of the LOCA, and will instruct him to maintain two running Emergency Containment Coolers (ECCs) beyond thirty minutes.

The licensee has determined the effect this would have on the calculated containment temperature and pressure transients during the LOCA.

Stopping the containment spray will tend to increase containment temperature and pressure;

however, the ECCs operate more e<fectively at higher containment temperature, because the higher temperature difference between the atmosphere and the cooling coils increases the heat transfer rate of the ECCs.

Thus, the ECCs naturally tend to compensate for the loss of the containment spray.

To a lesser

degree, the same argument holds true for the passive heat sinks (e.g., walls, structures) inside containment.

The licensee's analytical approach uses a calculated parametric correction to the containment pressure curves found in FSAR Section 14.3.4 (i.e.,

Figure 14.3.4.-8).

For each interval addressed in the analysis, the heat capacity of the affected components is calculated based on the capacity used in the original FSAR analysis.

In addition, the impact on capacity due to higher containment temperature is also assessed using original capacity criteria.

These net changes, in BTU, are then converted to pressure gain (or loss) for the suhiect interval and the original curve corrected per this factor.

Each subsequent interval builds upon those preceding it to assess the total correction factor.

The analysis is based upon additional transferred or un-transferred heat load in the containment.

Temperature of the atmosphere is the saturation temperature at the partial pressure of steam in the atmosphere.

The results of the licensee's cal-culation are presented in Figure 3 of the licensee's submittal dated

>une l~,

1986, and Figure RAI-2 of the licensee's submittal dated July 16, 1986.

Containment design pressure and temperature are not exceeded hy the revised transients.

The calculated temperature and Dressure transients also remain, overall, within the environmental equipment qualification envelopes provided in the licensee's submittal cited above.

Additionally, containment pressure is reduced to less than one-half of the peak calculated pressure within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after onset of the LOCA, in accordance with the requirements of General Design Criterion 38.

Human Factors Analysis launder the severe stress conditions that would be present in an accident scenerio H

of a LOCA accompanied by a loss of off-site power, and with the licensee's acknow-ledged increase in control room temperature, the staff was concerned that the operators may not satisfactorily accomplish the actions required by the proposed changes in the Emergency Operating Procedures (EOPs).

The licensee's submittals on EOG load evaluation did not address the human factors analysis (man-machine interface evaluation) in sufficient detail to assure the staff that operators could perform the required actions successfully and that existing indicators and controls would be adequate.

Subsequent to the licensee's submittals on EDG load evaluation, the staff has reviewed the revised Turkey Point EOPs and discussed the human factor issues with the licensee.

Hased on these telecon discussions with the licensee and a review of their proposed changes to EOPs, the staff finds that the licensee has conducted a satisfactory human factors analysis for the proposed EAP changes necessitated by the EDG over load problem.

The staff concludes that the proposed operator actions are acceptable.

Conclusion The EOG load evaluation and associated corrective actions for plant loading provide sufficient EDG margins when compared to the FSAR (Tables 3

& 7)

EOG margins.

Implementation of the corrective actions as documented in the EOG load evaluation observes that the FSAR load evaluation remains bounding and that the EDGs meet all loading requi rements as stated in the Turkey Point Technical Specifications.

The staff review of the FP&L submittals of EDG load evaluation, from an electrical point of view, finds that the loads for various conditions are within the 30 minute and continuous rating of the diesel generators.

The corrective actions proposed by FP&L for the loading of EDGs, i.e., manually dropping and/or adding loads during the first hour of an accident have been evaluated by the staff from a system analysis aspect.

The staff analysis con-sidered a loss of coolant accident in one unit with the non-accident unit in the shutdown mode with RHR system in operation to remove core decay heat.

The staff concludes that the corrective actions proposed (Emergency power reduction provisions) by the licensee in his submittals on EOG load evaluation are acceptable, because they are consistent with the accident analyses and plant emergency procedures.

The proposed EDG load reductions during the first 30 minutes provide sufficient emergency power for adequate core cooling following an accident coupled with loss of offsite power, and maintain containment pressure and temperature within the FSAR design limits.

-IP-The licensee has revised the emergency operating prncedures to incorporate the corrective actions outlined in his submittals on EDG load evaluation.

The licensee has also conducted a satisfactory human factors analysis for the re.ised emergency operating procedures, i.e., the licensee has evaluated all control room and Emergency Operating Procedures changes in accordance wi>h their Human Factors Engineering Guidance Manual.

The staff therefore concludes that the proposed operator interfaces to carry out the corrective actions are acceptable.

It is also noted that there are five Black Start Diesels (non-safety grade diesels) installed at Turkey Point Site.

The power from these diesels is available in less than one hour post LOCA after decision is made to initiate this-AC source.

The Black Start Diesels are hard wired to provide backfeed capability to the safety buses.

The licensee has assured the staff that proper procedures are available to implement the backfeed feature.

The licensee has performed tests to demonstrate this capability.

The caoahility of backfeeding the safety buses from the Black Start Diesels adds to the AC power available safety margin for events involving loss of offsite power.

December 12, 1986 t

~-Uoctet Ft-le-w/o eocTZ PAD2 Rdg w/o encl.

D. t'iilier w/encl.

D. McDonald w/encl.

DOCKET NO(S).

50-250 and 50-251 Hr. C. 0. Ifoody, Group Vice President Nuclear Energy Department Florida Power and Light Company Post Office Box 14000 Juno Beach, Florida 33408

SUBJECT:

TURKEY POINT PLANT UNITS 3 AND 4 The following documents concerning our review of the subject facility are transmitted for your information.

D Notice of Receipt of Application, dated D Draft/Final Environmental Statment, dated O Notice of Availabilityof Draft/Final Environmental Statement, dated D Safety Evaluation Report, or Supplement No.

, dated O Notice of Hearing on Application for Construction Permit, dated D Notice of Consideration of Issuance of Facility Operating License, dated D Monthly Notice; Applications and Amendments to Operating Licenses Involving no Significant Hazards Considerations, dated D Application and Safety Analysis Report, Volume O Amendment No.

to Application/SAR dated D Construction Permit No. CPPR-

, Amendment No.

dated D Facility Operating License No.

, Amendment No.

D Order Extending Construction Completion Date, dated gP Other (Specify/

1986

, dated t

date

Enclosures:

As stated Division of PlfR Licensing-A Office of Nuclear Reactor Regulation cc:

See next page OVF(Ce~

SURNAMe~

DATe+

LA,: A NRC FORM 318 (1/84) NRCM 0240

C I4 II

~ l~

l

~

~