Text

Supplement to Information Regarding License Amendment Request for Removal of Severe Line Outage Detection from the Offsite Power System
	ML16189A076
Person / Time
Site:	Millstone
Issue date:	06/29/2016
From:	Mark D. Sartain; Dominion Nuclear Connecticut
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	16-267
	Download: ML16189A076 (17)
	v • d • e

~

Dominion Nuclear Connecticut, Inc.

5000 Dominion Boulevard, Glen Allen, VA 23060 Web Address: www.dom.com June 29, 2016

'Dominion U.S. Nuclear Regulatory Commission Serial No 16-267 Attention: Document Control Desk NRA/WDC RO Washington, DC 20555 Docket Nos. 50-336/50-423 License Nos. DPR-65/NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNITS 2 AND 3 SUPPLEMENT TO INFORMATION REGARDING LICENSE AMENDMENT REQUEST FOR REMOVAL OF SEVERE LINE OUTAGE DETECTION FROM THE OFFSITE POWER SYSTEM In a letter dated June 30, 2015, Dominion Nuclear Connecticut, Inc. (DNC) requested amendments to Facility Operating License No. DPR-65 for Millstone Power Station Unit 2 (MPS2) and to Facility Operating License No. NPF-49 for Millstone Power Station Unit 3 (MPS3}. The proposed amendments would revise the MPS2 and MPS3 Final Safety Analysis Reports (FSARs) to: 1) delete the information pertaining to the severe line outage detection (SLOD) special protection system, 2) update the description of the tower structures associated with the four offsite transmission lines feeding Millstone Power Station (MPS), and 3) describe how the current offsite power source configuration and design satisfies the requirements of General Design Criteria (GDC)-17, "Electric Power Systems" and GDC-5, "Sharing of Structures, Systems, and Components." The amendments also request Nuclear Regulatory Commission (NRC) approval of a new Technical Requirements Manual (TRM) requirement, "Offsite Line Power Sources," for MPS2 and MPS3. This supplement proposes a revision to the TRM actions and the FSAR information for MPS2 and MPS3 as submitted in the June 30, 2015 license amendment request (LAR).

Attachments 1 and 2 to this letter provide DNC's proposed revisions to the TRM actions for MPS2 and MPS3, respectively. Since the proposed revisions are more limiting than those previously proposed in the June 30, 2015 LAR, the basis for the proposed revisions is still valid. Attachments 3 and 4 contain a replacement page for FSAR page 8.1-10 and 8.2-8, for MPS2 and MPS3, respectively, which add a description of the proposed new TRM actions.

This supplement does not require a revision to the conclusion of the significant hazards consideration provided in the June 30, 2015 LAR since the proposed changes are more limiting than previously proposed. The proposed amendment as supplemented does not involve a significant hazards consideration pursuant to the provisions of 10 CFR 50.92.

Serial No: 16-267 Docket Nos. 50-336/423 Page 2 of 3 Should you have any questions in regard to this submittal, please contact Wanda Craft at (804) 273-4687.

Sincerely,

.:...' -**- .!.._ _ ~ -

Mark D. Sartain Vice President - Nuclear Engineering COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mark D. Sartain, who is Vice President - Nuclear Engineering of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief. *

~ay of GVor. ,

~ .,;) Q!

Acknowledged before me this 2016.

My Commission E;xpires ff}/¥

((ki :J:l Notary Public Commitments made in this letter: None.

Attachments:

1. Revisions to Proposed New Technical Requirement for Offsite Line Power Sources, (For Information Only - MPS2)

2. Revisions to Proposed New Technical Requirement for Offsite Line Power Sources, (For Information Only- MPS3)

3. Replacement Page 8.1-10 MPS2 FSAR

4. Replacement Page 8.2-8 MPS3 FSAR

Serial No: 16-267 Docket Nos. 50-336/423 Page 3 of 3 cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman NRC Senior Project Manager U.S. Nuclear Regulatory Commission, Mail Stop 08 C2 One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station Director, Radiation Division ,

Department of Energy and Environmental Protection 79 Elm Street Hartford, CT 06106-5127

Serial No: 16-267 Docket No. 50-336 ATTACHMENT 1 REVISIONS TO PROPOSED NEW TECHNICAL REQUIREMENT FOR OFFSITE LINE POWER SOURCES (FOR INFORMATION ONLY)

DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

3/4.8 ELECTRICAL POWER SYSTEMS 3/4.8.1 A.C. SOURCES OFFSITE LINE POWER SOURCES TECHNICAL REQUIREMENT 3.8.1 .2 The offsite lines to the Millstone Switchyard: 310 , 348 , 371 (includes 364 line),

and 383, shall be FUNCTIONAL.

APPLICABILITY:

When Millstone Power Station (MPS) electrical output exceeds 1650 MWe net.

a. Wi one offsite line nonfunctional, perform the following or reduce total station output to ~EHf~EfflEl-YiaH:le-i:lSSreG~*l-WfffH:fle-..ffi!;s-.ef-<~~rEIQ+ffeffaHH~ffi-~3E*Ela1AE~Affi the Millstone raoility Out Guide stability operating limits within the next 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months s:

1. Restore FUNCTIONALITY of the affected offsite line within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , or

2. Establish the following ACTION requirements AND restore FUNCTIONALITY within 14 days. 7 days for Lines 310, 348, and 383, or within 14 days for Line 371/364

a. Once per shift, verify the remaining offsite lines to the MPS switchyard are FUNCTIONAL.

b. Perform an initial weather assessment for the scheduled line outage duration and then once per shift thereafter.

S 1650 MWe net

1. If t e assessment predicts adverse or inclement weather will exist while the off ite line is nonfunctional (i.e., out of service) , reduce total station output to * * *

aooordanoe with the Millstone r;aoility Out Guide stability operating limits, prior to arrival of the adverse or inclement weather.

c. Within one hour prior to or after entering this condition and at least once per 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months thereafter, verify that both the Millstone Unit 2 EDGs and the Millstone Unit 3 EDGs are OPERABLE and the Millstone Unit 3 SBO diesel generator is available. Restore any inoperable Millstone Unit 2 EOG or Millstone Unit 3 EOG to OPERABLE status and/or the Millstone Unit 3 SBO to available status within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months or reduce total station output to .H'M~FHH~

Millstone r;aoility Out Guide stability operating limits within the next 6

to S 1650 MWe net

b. With two offsite lines nonfunctional, reduce total station output IA assoFdaAse with the MillstoAe Facility Ollt Gllide stability opeFatiAg limits within the next 30 minutes.

TECHNICAL SURVEILLANCE REQUIREMENTS 4.8 .1.2 The four offsite lines to the Millstone Switchyard shall be determined to be FUNCTIONAL at least once per 7 days when station output exceeds 1650 MWe net.

BASES:

TR 3.8.1 .2 requires that all four offsite 345 kV transmission lines are FUNCTIONAL when MPS electrical output exceeds 1650 MWe net. TR 3.8.1 contains ACTIONS that must be performed when one offsite 345 kV transm ission line is nonfunctional.

TR 3.8.1 .2 provides flexibility to preclude plant downpowers due to planned and unplanned offsite transmission line outages. The TRM requirements provide this flexibility while also maintaining adequate defense-in-depth to ensure grid reliability and stability are preserved and the ability of the plants to respond to design basis accidents is not adversely affected .

With one offsite line nonfunctional , ACTION a.1 allows 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to restore FUNCTIONALITY. This 72-hour allowed outage time (AOT) is conservatively based on the loss of one offsite line being equal to the risk of losing one onsite connection to the offsite power system (i.e., TS 3.8.1.1 ). 1 days tor unes 310, 348, and 383, or 14 days tor une 3111364 and With one offsite line nonfunctio I, ACTION a.2 contains the provision to allow up to Gay& to restore FUNCTIONALIT if ACTIONS a.2 .a, a.2.b, and a.2.c are met. The 14 day AOT reduces the risk of a plant erturbation as a result of having to downpower the unit for short duration line outages-:- The 14 day AOT provides flexibility for conducting maintenance and improves operational safety margin by the following:

Minimizes the number of plant downpowers for short duration 345 kV transmission line outages.

Reduces the likelihood of a loss of offsite power event by establishing an AOT with additional defense-in-depth measures to minimize the potential for a double circuit failure scenario which can result in grid instability.

~

During the 14 day AOT, ACTION a.2.a ensures there are no known issues that could threaten the reliability of the remaining 345 kV transmission lines. Verifying the remaining 345 kV offsite transmission lines to the MPS switchyard are FUNCTIONAL, increases confidence that the remaining 345 kV lines will remain FUNCTIONAL during the planned outage of the affected 345 kV line.

~

During the 14 day AOT, the action to perform weather assessments as required by ACTION a.2.b ensures appropriate actions are taken to minimize the potential for adverse or inclement weather event to impact grid reliability with one line nonfunctional. If adverse

or inclement weather is predicted, the nonfunctional 345 FUNCTIONAL status or station output would be reduced to "fftEH+Fftff+R6t-Yi:fftf-e-i:tSSe61taM*I with the loss of one additional line in assordanse with the Millstone l=asility Out Guide stability operating limits rior to the arrival of the adverse or inclement weather.

applicable During the 14 day AOT, ACTION a.2.c (i.e ., both the Millstone Unit 2 and Millstone Unit 3 EDGs are operable and the Millstone Unit 3 SBO is available) provides assurance that AC power will be available to support required safety-related equipment in the unlikely event of a complete loss of offsite power during the time one of the 345 kV lines is nonfunctional.

This ACTION ensures that electrical power will be available in a timely manner to perform the required functions to maintain cooling to the reactor core in the unlikely event a loss of offsite power was to occur during th~ *11:;day AOT.

applicable '~

For the condition where the AOT is in use for one nonfunctional transmission line and one or more of the following components is out-of-service:

a Millstone Unit 2 EDG

a Millstone Unit 3 EDG

the Millstone Unit 3 SBO diesel generator 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months is allowed for restoration of the out-of-service component. If components is not restored within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , reduce total station output to *'ER<E!--ffffffHR43-YH*'te assosiated with the loss of one additional line in assordanoe with the Millstone r:aoility Out Guide stability ope rating limits within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months .

REFERENCE:

License Amendment The allowed outage times for Lines 310, 348, 371/364, and 383 are based on the configuration of the transmission lines at Hunts Brook Junction where Lines 383 and 310 cross over Line 371/364 and Line 348 runs to the west of the crossover. With Line 348, 310, or 383 nonfunctional, the possibility exists that either Line 383 or 310 could drop on Line 371/364 and result in three lines nonfunctional. Th is condition would impact grid stability and therefore, a 7-day AOT is allowed with the specified ACTION requirements in place. When Line 371/364 is nonfunctional, if either Line 310 or 383 drops, two transm ission lines remain FUNCTIONAL. Therefore, a 14-day AOT is allowed with the specified ACTION requ irements in place.

Serial No: 16-267 Docket No. 50-423 ATTACHMENT 2 REVISIONS TO PROPOSED NEW TECHNICAL REQUIREMENT FOR OFFSITE LINE POWER SOURCES (FOR INFORMATION ONLY)

DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3

3/4.8 ELECTRICAL POWER SYSTEMS 3/4.8.1 A.C. SOURCES OFFSITE LINE POWER SOURCES TECHNICAL REQUIREMENT 3.8.1 The offsite lines to the Millstone Switchyard: 310, 348 , 371 (includes 364 line),

and 383, shall be FUNCTIONAL.

APPLICABILITY:

When Millstone Power Station (MPS) electrical output exceeds 1650 MWe net.

ACTION:

S 1650 MWe net

a. With one ffsite line nonfunctional, perform the following or reduce total station output to the limiting val1:Je assosiated with the loss of one additional line in assordanse with the Millstone l=asility 01:Jt G1:Jide stability operating limits within the next 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months s:

1. Restore FUNCTIONALITY of the affected offsite line within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , or

2. Establish the following ACTION requirements AND restore FUNCTIONALITY within 14 days ~1 days tor unes 310, 348, and 383, or 14 days tor une 371/364 I

a. Once per shift, verify the remaining offsite lines to the MPS switchyard are FUNCTIONAL.

b. Perform an initial weather assessment for the scheduled line outage duration and then once per shift thereafter.

1. If the ass sment predicts adverse or inclement weather will exist while the offsi line is nonfunctional (i.e. , out of service), reduce total station output to *~:HtiFR+ttRe-YaHtM:~:;se~~t-Wtfft-if*HefS&-ereffie-aee-ttte-ffiff-HAe in assordanse with the Millstone l=asility 01:Jt Guide stability operating ffm+ts, prior to arrival of the adverse or inclement weather.

c. Within one hour prior to or after entering this condition and at least once per 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months thereafter, verify that both the Millstone Unit 2 EDGs and the Millstone Unit 3 EDGs are OPERABLE and the Millstone Unit 3 SBO diesel generator is available. Restore any inoperable Millstone Unit 2 EOG or Millstone Unit 3 EOG to OPERABLE status and/or the Millstone Unit 3 SBO

£s I t~

1650 MWe net to available status within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months or reduce total station output to limiting value assosiated with the loss of one additional line in assordanse with the Millstone Fasility Out Guide stability operating limits within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months .

to S 1650 MWe net

b. With two offsite lines nonfunctional, reduce total station output'1A--asS9li:ea~~R-EA the Millstone Fasility Out Guide stability operating limits within the next 30 minutes.

TECHNICAL SURVEILLANCE REQUIREMENTS 4.8.1 The four offsite lines to the Millstone Switchyard shall be determined to be FUNCTIONAL at least once per 7 days when station output exceeds 1650 MWenet.

BASES:

TR 3.8.1 requires that all four offsite 345 kV transmission lines are FUNCTIONAL when MPS electrical output exceeds 1650 MWe net. TR 3.8.1 contains ACTIONS that must be performed when one offsite 345 kV transmission line is nonfunctional.

TR 3.8.1 provides flexibility to preclude plant downpowers due to planned and unplanned offsite transmission line outages. The TRM requirements provide this flexibility while also maintaining adequate defense-in-depth to ensure grid reliability and stability are preserved and the ability of the plants to respond to design basis accidents is not adversely affected .

With one offsite line nonfunctional, ACTION a.1 allows 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to restore FUNCTIONALITY. This 72-hour allowed outage time (AOT) is conservatively based on the loss of one offsite line being equal to the risk of losing one onsite connection to the offsite power system (i.e., TS 3.8.1.1). 1 days tor Lines 310, 348, and 383, or 14 days for Line 371/364 and With one offsite line nonfunctional, ACTION a.2 contains the provision to allow up to

~ applicable 6ays to restore FUNCTIONALITY 1 ACTIONS a.2.a, a.2 .b, and a.2 .c are met. The 6ay AOT reduces the risk of a plant perturbation as a result of having to downpower the unit for short duration line outages.,. provides flexibility for conducting maintenance and improves operational safety margin by the following:

Minimizes the number of plant downpowers for short duration 345 kV transmission line outages.

Reduces the likelihood of a loss of offsite power event by establishing an AOT with additional defense-in-depth measures to minimize the potential for a double circuit failure scenario which can result in grid instability.

applicable During the AOT, ACTION a.2.a ensures there are no known issues that could threaten the reliability of the remaining 345 kV transmission lines. Verifying the remaining 345 kV offsite transmission lines to the MPS switchyard are FUNCTIONAL, increases confidence that the remaining 345 kV lines will remain FUNCTIONAL during the planned outage of the affected 345 kV line.

~

During the 14 day AOT, the action to perform weather assessments as required by ACTION a.2.b ensures appropriate actions are taken to minimize e potential for adverse or inclement weather event to impact grid reliability with one Ii e nonfunctional.

If adverse or inclement weather is predicted, the nonfunctional 345 V line would be restored to FUNCTIONAL status or station output would be reduced to ~~~tRe-¥affHS assosiated *.vith the loss of one additional line in assoFdanse with the Millstone F'asility Out Guide stability opeFating limits prior to the arrival of the adverse or inclement weather.

~

During the 14 aay AOT, ACTION a.2.c (i.e., both the Millstone Unit 2 and Millstone Unit 3 EDGs are operable and the Millstone Unit 3 SBO is available) provides assurance that AC power will be available to support required safety-related equipment in the unlikely event of a complete loss of offsite power during the time one of the 345 kV lines is nonfunctional. This ACTION ensures that electrical power will be available in a timely manner to perform the required functions to maintain cooling to the reactor core in the unlikely event a loss of offsite power was to occur during thf.s 14 day AOT.

~ ~

For the condition where the 14 day AOT is in use for one nonfunctional transmission line and one or more of the following components is out-of-service:

a Millstone Unit 2 EOG

a Millstone Unit 3 EOG

the Millstone Unit 3 SBO diesel generator 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months is allowed for restoration of the out-of-service component. If any o components is not restored within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , reduce total station output to * -~--R

'lalue assosiated with the loss of one additional line in assoFdanoe with the Millstone l=asility Out Guide stability opeFating limits within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months .

REFERENCE:

License Amendment The allowed outage times for Lines 310, 348, 3711364, and 383 are based on the configuration of the transmission lines at Hunts Brook Junction where Lines 383 and 310 cross over Line 371/364 and Line 348 runs to the west of the crossover. With Line 348, 310, or 383 nonfunctional, the possibility exists that either Line 383 or 310 could drop on Line 371/364 and result in three lines nonfunctional. This condition would impact grid stability and therefore, a 7-day AOT Is allowed with the specified ACTION requirements in place. When Line 371/364 is nonfunctional, if either Line 310 or 383 drops, two transmission lines remain FUNCTIONAL. Therefore, a 14-day AOT Is allowed with the specified ACTION requirements in place.

Serial No: 16-267 Docket No. 50-336 ATTACHMENT 3 REPLACEMENT PAGE 8.1-10 MPS2 FSAR DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

MPS-2FSAR tr. With any one of the four Millstone 345 kV transmission circuits out of service the plant remains stable for any three-phase fault normally cleared (four cycles) or any one-phase fault with the delayed clearing (eight cycles).

Ir. IA order to ffieet fhe lieeAsiAg reqttireffieAt that HO siHgle ffieehaAieal failttre, s1:1eh as a tower falliHg or a liAe drOf}f'iAg, is aBle to siffi1:1ltaHeo1:1sly affeet all eire1:1its iA stteh a *uay that off site f'OWer wo1:1 ld Be lost, siffi1:1ltaHeo1:1s 3 f"hase fa1:1lts htWe BeeA tested for eaeh ofthe two eire1:1its whieh are ffiOttHted tlf'OH eofftffioH towers .

With all liHes iH serviee fhe s~* steffi reffiaiAs staBle for this t'uo eire1:1it distttrBaHee.

It shottld Be reeogHil".ed that the fottr eirettits lea'¥'iHg the MillstoAe switehyard are f"Etired OH W.Co widely Sf'Eteed rows of dottBle eire1:1it str1:1et1:1res for oAly a short distaAee, aHd, heHee the eMf'OSttre to this dottBle eire1:1it 01:1tage is Sffiflll .

Witho1:1t MillstoAe UAit l oA liAe, the Aet MillstoAe otttf'ttt does Aot threateA systeffi staBility, eveA iA the e*veAt of this dottBle eire1:1it fatt lt. DottBle eire1:1it fatt lts oA the MillstoHe Beseek aHd MillstoAe MaHehester liAes do Aot reqttire geAeratioA rejeetioA iA order to ffifliAtaiA systeffi staBi lity.

~ The siffitt ltaAeotts loss of two MillstoAe eirettits OH eoffiffiOH strttet1:1res followiAg a f'reviotts (AoA siffitt ltaAeotts) 01:1tage of either of the other MillstoAe eirettits (or aAy other eritieal eleffieAt) ffittst Aot resttlt iA iAstaBility. All ofthe eritieal otttflges of this t)'f'e effeetively resttlt iA the loss of three of the fottr MillstoAe eirettits aAd leave the MillstoHe statioA weakly tied to the traAsffiissioA grid. Tu J"reveHt iAstaBilit)* for these eutreffiely severe (aAd highly iffiJ"FOBaBle) distttrBaHees, it is Aeeessary for the 8LOD 8P8 to Be iA serviee *uheH the loss of the tvto eirettits OA eoffiffiOA strttetttres takes f'laee .

The Millstone units are connected to the large interconnected transmission system in the eastern 15-15 half of the United States. The interconnected system frequency is maintained at 60 +/- 0.03 Hz in accordance with NPCC standards for the bulk power system. The system is designed and operated such that the loss of the largest single supply to the grid does not result in the complete loss of preferred power. The system design considers the loss, through a single event, of the largest capacity being supplied to the grid, removal of the largest load from the grid, or loss of the most critical transmission line. This could be the total output of a single Millstone reactor unit, the largest generating unit on the grid, or possibly multiple generators as a result of the loss of a

~ common transmission tower, transformer, or a breaker in a switchyard or substation.

IA order to eAsttre that the iAtereoAAeeted systeffi will reffifliA staBle followiAg eertaiA f'Osttt lated fattlts, flA 8P8, or geAeratioH rejeetioA seheffie, has BeeA iHstalled at the MillstoAe 8tatioA switehyard. The 8LOD, eoAtiAttottsly ffiOHitors the iAdi*tidttal state of fottr traAsffiissioH liAe eirettits terffiiHated at MillstoAe l 5G s*witehyard. togefher with the geHeratioA ott!f'ttt flt the MillstoAe eOffif'lex. The fottr liAe eirettits are:

MillstoAe MaHehester LiAe O'tttffiBer 31 O);

~ MillstoAe Beseek O'tttffieer 348);

8.1-10 Rev. 33

Serial No: 16-267 Docket No. 50-336 INSERT In order to ensure the interconnected system will remain stable and offsite power circuits meet GDC-17 requirements, the following technical requirement actions and generation output restrictions will be implemented when both Millstone Power Station Unit 2 and Unit 3 are at power:

With any of the 345 kV offsite transmission lines (310, 348 , 371 (includes 364 line) ,

and 383) out of service or nonfunctional, the nonfunctional transmission line shall be restored to functional status within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months or total station output shall be reduced to~ 1650 MWe net within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months ; or, alternatively, within 7 days for Lines 310, 348 , and 383 or 14 days for Line 371/364 with the following action requirements in place:

a. Once *per shift, verify the remaining lines are functional ,

b. Once per' shift, perform a weather assessment,

c. Once per 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , verify the EDGs are operable and the SBO diesel is available.

If any of the above actions cannot be met or if a weather assessment predicts adverse or inclement weather will exist while a transmission line is nonfunctional (i .e., out of service), total station output shall be reduced to :5 1650 MWe net within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months to ensure the stability and availability of the electrical grid is maintained .

With two 345 kV offsite transmission lines nonfunctional, total output shall be reduced to :5 1650 MWe net within the next 30 minutes.

The allowed outage times (AOT) for Lines 310, 348, 371/364 , and 383 are based on the configuration of the transmission lines at Hunts Brook Junction where Lines 383 and 310 cross over Line 371/364 and Line 348 runs to the west of the crossover. With Line 348, 310 , or 383 nonfunctional, the possibility exists that either Line 383 or 310 could drop on Line 371/364 and result in three lines nonfunctional. This condition would impact grid stability and therefore, a 7-day AOT is allowed with the specified action requirements in place. When Line 371/364 is nonfunctional, if either Line 310 or 383 drops, two transmission lines remain functional. Therefore, a 14-day AOT is allowed with the specified action requirements in place.

Serial No: 16-267 Docket No. 50-423 ATTACHMENT 4 REPLACEMENT PAGE 8.2-8 MPS3 FSAR DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3

MPS-3FSAR or the isolation of an area can cause a deficiency or surplus of generation respectively. Either case causes frequency dev iations. High frequency deviations causes generation to be tripped, and low frequency causes automatic load shedding. Either action applied appropriately helps the frequency to recover to 60 Hz within a few minutes.

The system is designed and operated such that the loss of the largest single supply to the grid does 15-16 not result in the complete loss of preferred power. The system design considers the loss, through a single event, of the largest capacity being supplied to the grid, removal of the largest load from the grid, or loss of the most critical transmission line. This could be the total output of a single Millstone reactor unit, the largest generating unit on the grid, or possibly multiple generators as a result of the loss of a common transmission tower, transformer, or a breaker in a switchyard or

~ubstation.

~ ~

IH order to eHsttre that the iHtereoHHeeted systeFH will reFHaiH stable followiHg eertaiH postttlated fattlts, Speeial ProteetioH S~*steFHS , Of geHeratioH rejeetioH seheFHes, ha*1e eeeH iHstalled at the MillstoHe StatioH switehyard. The se ..*ere LiHe Otttage Deteetor Of SLOD eoHtiHttOttsly FHOHitors the iHdh*idttal state of fottr traHsFHissioH liHe eirettits terFHiHated at MillstoHe l 5G switehyard together with the geHeratioH otttf'ttt at the MillstoHe eoFHpleJt. The fottr liHe eirettits are:

-h MillstoHe MaHehester Li He ~lttFHeer 31 O);

~ MillstoHe Beseek LiHe ~lttFHeer 348);

~ MillstoHe Card Street LiHe ~lttFHeer 383);

4-: MillstoHe MoHt>i*ilie Li He ~lttFHeer 3'.7 l)

Shottld the systeFH eoHditioH arise *where atty oHe ofthe fottr eritieal liHe eirettits is ttttavailaele, the getteratiott at Millstotte is above a predeterFHiHed MW level, aHd two speeifie trattsFHissioH eirettits are foreed ottt, thett geHeratioH will atttoFHatieally be ettftailed at MillstoHe. Stability stttdies iHdieate that dttriHg FHffi<iFHttfH Otttf'ttt eottditioHS (200 l MW), MillstoHe UH it 3 eaH ee stteeessfttlly tripped attd systeFH stability FHai-HtaiHed leaviHg MillstoHe UHit 2 iH syHehroHisFH with the trattsFHissioH HeP.vork. The triPJ'ittg of this ttHit resttlts iH a getteratioH redttetioH of ttf' to Elf'pro:ximately 1143 MW with 858 MW reFHaiHiHg syHehroHi'.Z':ed.

Stttdies ittdieate that a large loss of geHeratiott iH }Jew EHglaHd eottld lead to voltage f'FOeleFHs iH

}Jew Yi"lrk aHd PeHttsylvaHia, wheH heavy west to east power traHsfers are takiHg plaee OH their systeFHs. ISO }Jew EHglaHd FHOHitors the loadiHg OH the }Jew ¥erk aHd PeHttsylvaHia systems to deterFHiHe the FHaxiFHttm allowable amottHt of geHeratioH loss whieh the iHtereoHHeeted system e!lfl safely talerate. WheHever atty oHe of the fottr (4) eritieal liHe eireuits iHvolved iH the geHeratiott rejeetioH seheme is ottt of serviee, the outf"ttt ofMillstoHe 3 is redtteed to the maxiFHuFH allowable amouHt of geHeratioH loss.

The operatioH of the SLOD MillstoHe geHeratioH rejeetioH seheFHe is eased OH the otttage of eomeittatioHs of eertaiH trattsmissiott eireuit eleFHettts. This systeFH eotttiHttously moHitors the ittdividttal stattts of the fottr eritieal traHsFHissioH elemettts together with the getteratioH otttf"ut of 8.2-8 Rev. 28

Serial No: 16-267 Docket No. 50-423 INSERT In order to ensure the interconnected system will remain stable and offsite power circuits meet GDC-17 requirements, the following technical requirement actions and generation output restrictions will be implemented when both Millstone Power Station Unit 2 and Unit 3 are at power:

With any of the 345 kV offsite transmission lines (310, 348, 371 (includes 364 line),

and 383) out of service or nonfunctional, the nonfunctional transmission line shall be restored to functional status within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months or total station output shall be reduced to~ 1650 MWe net within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months ; or, alternatively, within 7 days for Lines 310, 348, and 383 or 14 days for Line 371/364 with the following action requirements in place:

a. Once per shift, verify the remaining lines are functional,

b. Once per shift, perform a weather assessment,

c. Once per 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , verify the EDGs are operable and the SBO diesel is available.

If any of the above actions cannot be met or if a weather assessment predicts adverse or inclement weather will exist while a transmission line is nonfunctional (i.e., out of service), total station output shall be reduced to::; 1650 MWe net within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months to ensure the stability and availability of the electrical grid is maintained.

With two 345 kV offsite transmission lines nonfunctional, total output shall be reduced to ::; 1650 MWe net within the next 30 minutes.

The allowed outage times (AOT) for Lines 310, 348, 371/364, and 383 are based on the configuration of the transmission lines at Hunts Brook Junction where Lines 383 and 310 cross over Line 371/364 and Line 348 runs to the west of the crossover. With Line 348, 310, or 383 nonfunctional, the possibility exists that either Line 383 or 310 could drop on Line 371/364 and result in three lines nonfunctional. This condition would impact grid stability and therefore, a 7-day AOT is allowed with the specifi~d -~ctiQll _e_ectµirements in place. When Line 371 /364 is nonfunctional, if either Line 310 or 383 drops, two transmission lines remain functional. Therefore, a 14-day AOT is allowed with the specified action requirements in place.

v t e Letter Sequence Supplement
CAC:MF6430, (Approved, Closed)
Initiation Acceptance... Supplement Administration Questions Answers 25 February 2016 Results Approval Other:
MONTHYEAR2016-06-29 [Table View]

ML16189A076

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