B16726, Forwards Response to 970113 RAI Re Design of Millstone,Unit 3,station Blackout Sys.Response Supersedes Util . Commitments Made by Util,Encl

Forwards Response to 970113 RAI Re Design of Millstone,Unit 3,station Blackout Sys.Response Supersedes Util . Commitments Made by Util,Encl

ML20212D203
Person / Time
Site:	Millstone
Issue date:	10/23/1997
From:	Brothers M NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
B16726, TAC-M96054, NUDOCS 9710310038
Download: ML20212D203 (10)

Text

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'I1w %:theast Utihtice Systrin DCT 23 997 pocket No. 50-423 B16726 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Millstone Nuclear Power Station Unit No. 3 Revised Response to Request for Additional Information (TAC No. M96054) and Revised Commitment This letter provides Northeast Nuclear Energy Company's (NNECO's) response to the January 13,1997 NRC Staff request for additional information regarding the design of the Millstone Unit No. 3 Station Blackout (SBO) System. This letter supersedes NNECO's previous response on this subject dated February 28, 1997, B16181. The detailed response is provided in Attachment 1.

In addition, per this submittal NNECO is informing the Staff of the elimination of a previous Unit 3 commitment related to restoring the control room air conditioning within one hour after AAC power is available during an SBO. The details of this commitment change are provided in Attachment 2.

NNECO's commitments associated with this letter are provided in Attachment 3.

If you should have any quesilons regarding this submittal, please contact Mr. David Smith at (860) 437-5840. '

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Very truly yours. l 7

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NORTHEAST NUCLEAR ENERGY COMPANY m

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M. H. Brothers \

Vice President - Millstone Unit No. 3 Attachments 9710310038 og 971023 "

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U.S. Nuclear RD;;ulatory Commission B16726\Page 2 oc:

J. W. An:$erson, NRC Project Manager, Millstone Unit No. 3 A. C. Ceine, Senior Resident inspector, Millstone Unit No. 3 H. J. Miller, Region 1 Administrator W. D. Ttavers, Dr., Director, Special Projects I

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Docket No. 50423 B16726  ;

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Attachment 1 Millstone Nuclear Power Station, Unit No. 3 Revised Response to Request for Additional information Related to Alternate AC Power Source Requirements (TAC No, M96054)

October 1997 s,

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816726%ttachment 1Page 1 i l

Millstone Nuclear Power Station, Unit No. 3 Revised Response to Request for Adastional information i Related to Alternative AC Power Source Requirements ,

OACRoJd980M Question 1 i After a loss of offsite power (LOOP), how soon will the station blackout diesel generator (SBO-DG) auxiliaries be powered from the SBO-DG or another diesel generator? Also, which procedure will cover this requirement?

Reasonne ,

The SBO-DG auxiliaries will be powered from the SBO diesel generator within the first hour of a postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP, thereby ensuring availability of the SBO-DG at any time during the postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP. Emergency Operating Procedure (EOP) 35 ES-0.1, " Reactor Trip Response," will provide the '

procedural controls to power the SBO-DG auxiliaries. 7 Question 2 i if the SBO-DG is used to power the auxillaries:

i n._How long will the SBO-DG be running and at what load?

b. What are the consequences of running the SBO-DG at light load conditions?

l c. What is the impact on the SBO-DG fuel supply in view of the fact that the SBO-DG may be running for an additional 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />?  ;

Reasonam L a. Since the SBO-DG will be started within i hour of the LOOP event, and l remain running for the remainder of the postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP, the SBO-DG will t>s running for approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The SBO-DG will initially be loaded to less than the preferred minimum light load value specified by the SBO-DG engine iranufacturer. However,- EOP. 35ES-0.2 will provide' i requirements to increase the load to a value greater than the preferred i

minimum load value within 4'/ hours of starting the SBO-DG engine. This loading sequence follows requirements set forth by the SBO-DG engine manufacturer for light lood operation. ,

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. B16726%ttachment 1\Page 2

b. There are two consequences of running the SBO-DG at light loads; neither of which wdl present a problem. One consequence is that running the SBO-DG at light loads promotes ' souping.' Souping describes a condition of excessive oil escaping past the piston rings into the combustion chamber and ac4,umulating in the exhaust system and air box. Souping causes plugged turbine inlet screens, smoking exhaust, and potential manifold . fires.

However, the loading sequence described previously (see response to a of this question) avoids the potential problems from souping. 'he other consequence is increased wear on turbo charger drive gears, with n potential increase in the maintenance schedule to comply with the vendor l recommendations. However, it is unlikely that the changes to EOP 35 ES 0.1 L will result in a significant accumulation of light load operation hours and l therefore should not have an impact on the scheduled maintenance.

c. The SBO-DG fuel oil system is capable of providing fuel oil to the SBO-DG for the entire 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP. This 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP defines the duration of the design basis station blackout event. The design basis station blackout event ,

is the loss of offsite power concurrent with turbine trip sad unavailability of '

the emergency diesel generators. These events occur at time 0. It is assumed at the end of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, power is restored from either offsite or onsite sources.

The event where a postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP oreurs and one or both emergency diesel generators start, run and then fail sometime into the LOOP is beyond the design basis station blackout event. This scenario is bounded by the design basis case where the postulated 8' hour LOOP and the unavailability of the emergency diesel generators occur at time 0. The SBO-DG will have sufficient fuel oil to cope with the remainder of the postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP. Additionally, during the postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP, should the SBO-DG run for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> lightly loaded in accordance with engine manufacturer's requirements, and the emergency diesel generators become unavailable and the LOOP continues, there is sufficient fuel oil for the SBO-DG to run for approximately 6 additional hours at full load beyond design basis LOOP.

In conclusion, there is minimal impact on the SBO-DG fuel oil system if the SBO DG is run lightly loaded to ensure its availability during the postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP. The scenario where the postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP occurs and the emergency diesel generators become unavailable some tinw after the LOOP, is beyond the design basis of the station blackout event, however sufficient fuel oilis available.

u.s. Nuclear Regulatory Commission B16726%ttachment 1Page 3 5

Question 3 If another diesel generator is used to power the auxiliaries:

a. Provide details of this diesel generator (capacity, connectability, availability, reliability, etc.)?

b. Is this a new diesel generator?

c. . Provide details on how it will be interfaced with the existing switchgear and equipment.

L Resoonse

a. No, another diesel will not be used to power the auxiliaries. The_ SBO-DG will be used to power the SBO-DG auxiliaries.

b. The SBO-DG was installed in 1993 for compliance with 10CFR50.63, loss of all alternating current power.

c. The SBO-DG will power its auxiliaries during the postulated 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> LOOP in the same manner as during a Station Blackout event. The auxiliaries will become re-energized once the SBO-DG output breaker is closed. However,-

as a result of the procedure change to EOP 35 ESA1 a modification to the closing logic associated with the SBO-DG output breaker will be required.

' The modification will allow the SBO-DG output breakers to be closed while either EDG output breaker is closed.

Question 4 Provide details regarding the testing and operator training requirements resulting from this modification.

Response

Testing will be conducted to verify that the procedure changes to EOP 35 ES-0.1 will ensure power is provided to the SBO-DG auxillaries and that the SBO-DG auxiliaries can be powered within one hour of a LOOP. Additionally, the design and tests results will ensure the initial blackout test remains valid.

Classroom, simulator and/or in-plant training, regarding the procedure changes to EOP 35 ES-0.1, will be provided to Licensed and Non-Licensed Operators.

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i Docket No. 50423 B16726 i

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Attachment 2 Millstone Nuclear Power Station, Unit No. 3 Elimination of a Previous Commitment Related to SBO c October 1997 u--

i U.S. Nuclear Regulatory Commission 816726%ttachment 2Page 1 i-On August 1,1991 NNECO submitted a response to the Staff addressing the  :

j recommend 9tions contained in the safety evaluation repor1 (SER) for the station I i blackout rule, in our response we re evaluated the effects of loss of ventilation

, for the Unit '3 Control Room and committed to provide control room air i

conditioning after AAC power is available (within one hour) The control room .

heatup calculation indicates the temperature during an SBO, concurrent with

! loss of all air conditioning, will reach a maximum 98.1 degrees F after eight' ,

i hours. This temperature is considerably below the NUMARC 87-00 criteria of .

110 degrees F for control room habitability and the temperature necessary to i

ensure equipment operability. Therefore, we intend to eliminate this commitment j to provide control room air conditioning within one hour of an SBO.

l l Existing plant procedures provide directions on starting the control room air conditioning, based on existing generator loading, i

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Docket No 50-423 B167M l

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Attachment 3 Millstone Nuclear Power Station, Unit No. 3 NNECO's Commitments Associated With Revised Response for Additional Information. TAC No. M96054 i

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October 1997

U.S. Nuclear Regulatory Commission B16726%ttachment 3Page 1

, Attachment 3 List of Regulatory Commitments The fcilowing table identifies those actions committed to by NNECO in this submittal. Please notify the Manager Regulatory Compliance at the Millstone l Nuclear Power Station Unit No. 3 of any questions regarding this document or any i- associated regulatcry commitments.

Number Commitment Due

- B1672641 Procedure EOP 35 ES-0.1 will be revised to ensure SBO-DG availability during the postulated eight hour LOOP. EOP 354.2 will - Prior to be revised to increase the SBO-DG loading to Mode 4 a valua greater than the preferred minimum -

load value within 4'/ hours of starting the SBO-DG engine.

B16726-02 As a result of the procedure change to EOP 35 ES-0.1 a modification to the closing logic Prior to associated with the SBO-DG output breaker Mode 4 will be required.

B16726-03 Testing will verify that the logic modifications will allow the SBO-DG output breeker to close Prior to for the new event. Mode 4 B16726-04 Classroom, simulctor and/or in-plant training, regarding the procedure changes to EOP 35 Prior to ES 0.1, will be provided to Licensed and Non- Mode 4 Licensed Operators.

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