ML20045H402

LER 93-007-00:on 930611,plant Mgt Discovered Reduction in EDG Fuel Oil Storage Capacity Per SER & Fsar,Constituting Event Outside Design Basis of Plant.Caused by Inadequate Design Interface.Temporary Tanker utilized.W/930709 Ltr

ML20045H402
Person / Time
Site:	Millstone
Issue date:	07/09/1993
From:	Joseph V, Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-007-01, LER-93-7-1, MP-93-544, NUDOCS 9307200173
Download: ML20045H402 (5)

Text

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'NOI'TNEAST tmLITIES ma-=' o" San s~t B-"n connata l de*sfe$'nIfaSEa'eh se't!E "1e Ce pan P.O.BCX 270

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[80asItd$tfeEbIEb"oNoeny HARTFORD. CONNECTICUT 06141-0270 Northeast Nuclear Energy Company (203)665-5000 July 9, 1993 MP-93-544 Re: 10CFR50.73(a)(2)(ii)

U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Reference:

Facility Operating License No. NPF-49 Docket No. 50-423 Licensee Event Report 93-007-00 Gentlemen:

This letter forwards Licensee Event Report 93-007-00 required to be submitted within thirty (30) days pursuant to 10CFR50.73(a)(2)(ii).

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY eplm ' .

m Stephen Scace Vice President - Millstone Station SES/VJ:dir

Attachment:

LER 93-007-00 cc: T. T. Martin, Region 1 Administrator P. D. Swetland, Senior Resident inspector, Millstone Unit Nos.1, 2 and 3 V. L. Rooney, NRC Project Manager, Millstone Unit No. 3 f/f I

9307200173 930709 ,, 1 0

{DR ADOCK 05000423 PDR r' n

NRC Form 366 U S NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 46-89) E> PiRES 4;30/92

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• Estimated birden per response to comp!y with th s in'O' matron CoheCiton reouest 50 0 hrs F or ward Comments Fegardrng burden eshma's to the RDCordt

. LICENSEE EVENT REPORT (LER) and Reports vanagemem aranen ec30). u s Nucisar Repu!atory Commission Washington. DC 20555. and to the Fawwork Recuction Prorect (3160-0104 . Office of Management and Buaget. Wasn.ngton. DC 20603 FACIUTY NAME p; DOCKE T NUMBik (2) WE- r3' i Millstone Nuclear Power Station Unit 3 ol si ol of old 12 l3 1lOFl 0l 4 l llTLE 14)

Reducuon in Emergency Diesel Generator Fuel Oil Storage Capacity E VENT DATE (5) L E A NUM:3EA ,(; AEPORT DATE r71 OT HE R F A crL i? iE S INvCi vE D d B r VONTF DAV YEAR YEAR W .

MONTH DAY YEAq F ACIUTY NAME S of 5! ol ol ol l l l 0 6 1l1 9 3 9 l3 0l0l7 0l 0 0l7 0l9 9l 3 ol5lololol l l OPE RATING TH6 REPORT 15 DE!NG SUDM;TTED PURSJANT TO THE AEQUfREMENT S OF 10 CFR [- (Check one or more of the folloung)(11)

MODE (9) l 20 40210) 73 711bl 20 cm 50. 73 (a) (2) Ov) pOwEA 20 405(a)(1) oi 50. 36 ici n i 60 73(a)(2)(v) 73. 7 ) (c)

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60. 73 f a } l2) h 20 405(a) p liq N 50 73(ali2thi! SC 73:ali2)(vWitB) 214DSla * 'li s m SC.73(a)(2h *1 60 73lal(2)tml UCENSEE CON 7 ACT FOR THS LER P2r NAME TELEPHONE NUMBE A ARE A CODE Vere R. Joseph, Engneer. Ext. 4742 2l0l3 4l4l7l-llj7l9l1 COMDLETE ONE UNE FOR E ACH COMDONENT F AtLURE DESCRtBED !N TH3 REPOAT M31 CAU$E SfSTEC OOMDONENT Yh^ Ed .

cAUSE SYSTEM COMPONENT k pph l l 1 I I I I I II I I I I si l II I I I I I II I I I I SUPPLEMENT AL AEPORT EXPECTED M4i MONTH DAY YEAR SUBM'SSiON

] vi S ne yes, camp,ete EXPECTED SUBM:SSION DATE) DAM IW NO { ) }

ABSTR AcT tumrt to 1400 spaces L e . app ommatety Uteen singte-space typewntien imes) 06)

On June 11, 1993, at approximately 1044, in Mode 1 at 1009 power. plant management concluded that the reduction in available Emergency Diesel Generator (EDG) fuel oil supply below the capacity discussed in the Safety Esaluation Report and Final Safety Analysis Report constnuted an event outside the design basis of the pla nt. Storage tank capacity was reduced from a 3 1/2 day EDO run time, to slightly greater than 3 days. The two tank storage capacny to support 7 day operation of a single EDG was reduced to slightly greater than 6 days. The day tank storage capacit) was reduced from 1-1/2 hours to 3/4 of an hour. The reduced capacity resuhed from revised calculations arid were not the result of physical modifications.

The root cause of tlus esent is inadequate design interface.

No immediate correctne actions were required and the EDGs are considered operable.

A proposed License Amendment will be submitted by August 31, 1993. A temporary fuel oil tanker is being unhted to proside approximately 7,000 gallons of addnional fuel oil, pendmg isiue resoluuon.

By July 31, 1993 guidance to order fuel oil, and to initiate a load sheddmg evalua' ion, will be incorporated into the ernergency response proceduret A re-evaluation of the loss of coolant accident and loss of off-site power load sheddmg calculation will be performed by October 31, 1993, to demonstrate the ibility to extend EDG run times.

NRC f orm 36S 1649) i

NAC *orm RE A V$ nucle AR REGULATORY COMM'SSloN APPROVED oMB NO 3150-0104 16-80 EXP6RE S. 4 /30/92 Estimated buroen r;er response to comply with this mamn cee:mn rewest; s0 o nrs. rorware LICENSEE EVENT REPORT (LER) Co'" aments rega"dsnQ buroen estimala to the Records TEXT CONTINUATION and Reoorts Management Branch (p.4acn u s Nuc.eae Reguatory Commission. Washmotor: DC 20555. and to me Fape work Red;ntion Pro lect (3150-01D4). off,ce of Management and Budget. Washmgtort DC 20S33 F ACUTY NAUc (1) DocAET NUMBEP {2J LFR NUM9ep o PAGE (3 r Stu.rNnAL REVI!aON YEAR Ntam m ets Millstone Nuclear Power Stauon Unit 3 0l5lol0lol4l2l3 9l3 0l0l7 0l0 0l 2 OF 0l4 TEC M mye swe is rocwred use acat.caa; NRc Gorm a66A s} D7)

1. Descnmion of Esent On June 11. 1993. at approximateh 1044, at 2250 psia and 586 degrees Fahrenheit, with the plant in Mode 1 at 100G power, plant management concluded that the reduction in available Emergency Diesel Generator fEDG) fuel oil supply below the capacity dncussed in the Millstone Unit 3 Safety Evaluation Report (SER) and Final Safety Analysis Report (FSAR) constituted an event outside the design basis of the plant. An mimediate nonfication was performed to document this condition.

On May 8,1992, Northeast Utihues engineenng persornel initiated a formal Operabihty Determination /Reportabiht) Evaluanon (REF) to evaluate concerns with respect to the available fuel oil y u av for the EDGs. As part of a self- assessment in the form of an in-house electrical distribution functional mspecuon (EDSFI), fuel oil capacny inconsistencies had been .dentined dunng a review i uG loadmg calculations versus the EDG loadmg outlined m the FSAR. In support of the REF, a mulanon was performed to venfy the capacity of the EDG fuel oil storage and day tanks. The calculanon concluded that the storage tank and day tank capaciues used to suppon the EDG run times stated m the FSAR were not correct. The followmg contributions resulted either in a reduction in (usable) fuel oil storage capacity or increased the EDG fuel oil consumption:

The size of the post-accident elecincal loads were increased due to a revised calculation methodology and corrections in the calculation occurring subsequent to the origmal design calculation. ( Although no new electrical loads have been added, the increased EDG loading was shown to be within the 2,000 hour0 days <br />0 hours <br />0 weeks <br />0 months <br /> ratmg (i.e., 5335 kW) of the machine.)

Worst case mstrurnent errors, which had not been previously assumed were incorporated into the I

current calculauon.

The effect of vanauons in the fuel oil specific gravity (vice usm; an aserage value) on the tank level mdicator readings were considered.

Consideranons for vortex fonnation were included (this apphes to the EDG day tank only).

• Usable tank volumes were taken into considerauon.

Results of the reviews mdicate that the storage capacity, which ongmally allowed a 3-1/2 day run time per EDO, as stated m the FSAR and SER, now provide a calculated run ame of slightly greater than 3 days. The two tank storage capacity to support 7 day operauon of a smgle EDG was reduced to slightly greater than 6 days. The day tank storage capacity was reduced from 1-1/2 hours to 3/4 of an hour.

The REF was completed on January 29. It;93, with the conclusion that the reduction m fuel oil capacity was not a reportable occurrence and the EDGs , vere operable. The REF conclusion was based on a determinanon that the ongmal deugn considerauons, which were used to justify the fuel oil system, did I not change, and the margm of on-site capacity was not significantly reduced to the point where contingency teptemshment actions would be compromised.

I' On March 31,1993, Northeast Nuclear Energy Company (NNECO) had informed the NRC of its evaluation on the Millstone 3 EDG fuel oil storage systems. As part of the correspondence, NNECO submitted a 10CFR50.59 Safety Evaluation which concluded that the reduction in fuel oil capacity was I safe for conunued operation of the plant and did not adversel3 impact the margin of safety. This position was also discussed in a meeting with the Senior NRC Resident inspector on June 4,1993.

f Subsequently, in a June 7.1993 correspondence to NNECO, the NRC expressed that the reduction in fuel oil capacity consututed a change to the design basis of the plant, i

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m c Porm 356 A U S. NL'cLE AR PEGUL ATORY COMMSSION APPROVED OMBrJO 316C-0104 the9; ExPAES 4/30/Q2 Eshmated tween por response to compiy eth this "wam emm mst 60 na F omard LICENSEE EVENT REPORT (LER) COmmerits regaramg bJ'Oen ebbmate 10 Ih8 beCOrC5 TEXT CONTINUATION ane rats vanamet tvanen wsacn u s Nuvear Aeguietory commission. Wasmngton DC 20555. and to ine Papework ReducDon Pr ofect 131sD-0104 : O*f ee of Management and fssopet A ashrncton DC 20603 F ACUTY N AME l1; DOCKET NUMBER G) t FA NUWF A rE t PAGE Gi y[An, NWA WM mem um Mt!1 stone Nuclear Power Station Unit 3 o Sl ol ol ol4 l2 l3 9l3 0 l 0l 7 0l0 0l 3 OF 0l4 itn e m scace .s we1 me naamonai Nac eorrr. 3 sci s3 (in Followmg several discussions with NRC personnel includmp the Senior Resident inspector, and upon reconsideration of the interpretauon of repo~.ing gu dance, NNECO determmed the reduction m fuel oil margin was a reportable condnion on June 11,1993 No immedtate operator actions were required in response to this esent. In addnion, the licensee had prenously taken measures to temporarily merease the available fuel oil storage volume by uuhzmg a tanker with approximately 7,000 gallons of diesel fuel oil .

II. Ctme of Es ent The root cause of this event is madequate design mterface. The ongmal design calculanon indicated that each EDG fuel oil storage tank, when hlled, had a capacity to support approximately 3-1/2 days of contmuous operation. Howeser, gross tank storage capacity was used in the design calculation. The salue for tank storage capacny was not properly reconciled wnh usable tank volume and system operating condinons.

A contnbuting factor n some of the assumptions m use at the ume when the origmal calculation was performed, are not considered consersatne when revieued against current calculanon assumpoons (e.g.,

specific granty ranges, vortex formation and leve! mstrument maccuracies are incorporated into current calculanons).

The ieused assumpuons and current cakulation methodologies which have been incorporated into the EDG loading calculauons have resulted m an merease m the calculated loads and an increase in EDG loadmg (although no new loads were added). Changes in loading duranon also resulted m an merease in EDG fuel oil consumpoon.

Ill. Anaksn of Event This event is bemg reported pursuant to 10CFR50 73(a)(2)(ii), as an event or condition which resuhed in the nuclear pouer plant bemg in a condman that was outside the design basis of the plant. An immed: ate nonhcanon was performed pursuant to 10CFR50.72(b)(1)(ii).

The emergency AC power source consnts of two 4.16 kV, emergency diesel generators, each rated at 4,9f4 kW continuous output (and 5,335 kW for 2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />). The fuel oil system for each EDG consists of a storage tank sized to store approximately 35,000 gallons and a '50 gallon day tank. Two redundant transfer pumps are provided for each storage tank. One transfer pump per tank n prouded with an ahernate power supply from the opposne train emergency bus to allow the transfer of fuel to extend the fuel supph to one EDG.

The EDO fuel oil system design as described in the FSAR and SER, was for 3-1/2 days of contmuous operauon at rated load per diesel, bated on tank storage capacity. Exception was taken to the 7 day fuel 011 supply requirement for each diesel generator as outhned in ANSI N195: Arnerican National Standard Fuel Oil Sptems for Standb> Diesel-Generators. At the Ome of the hcensing process, the design of the fuel oil system was justihed and accepted by the NRC based on the following considerations:

Wniun 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of a loss of off-site power. (LOP) or an LOP coincident wnh a postulated accident, addaional fuel oil would be ordered, and fuel oil to extend EDG run times will be delisered to the site wnhm 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after notice, from geographically diserse off-site suppliers.

Historically. the grid supplymg the Milktone site has prosen to be rehable.

A reduction or sheddmg of loads could extend the operauon of each EDG beyond 3-1/2 days to a penod of approximately 5 to 6 days.

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• JRc Porm 3% A uS NUCLE AR REGULATO9Y COMM:SSION APPRON/ED Oh/8 NO 3150.0104 16-80L EXPAE S 4 /30/92 Estimatec traroen per response to compty wrth th's

• mat *' co"*ct* '* * *5t 60 0 " Fa*'d LICENSEE EVENT REPORT (LER) comments rega-oms"buroen estimate to the Recoros TEXT CONTINUATION se Renons Management er nen to-Saon u s. nuciear Regutatory Commissiort. Washington DO 20555. anc to tne Paperworm Recuct on Profect (3150-0104). Office of Management and Buopet Washmoton DC 20503 F AO!UTV NAME (1) DOC.KET N#M.ER (2i tJ A NU"9E 54 fe, PAGE (3)

YEAR N NUMBm MBR Millstone Nuclear Power Stauon Unn 3 0l Sl 0l 0l 0l4 2l3 9l3 0l 0l 7 0l0 0l 4 OF 0l4 T[XT (t' r%te space is reQuaet use &M icas: NRC Form 356A s) 117j Because the origmal design considerations used to jusufy the fuel oil system did not change, and the margin of on-sne capacity was not significantly reduced to the point where contingency replenishment acuans would be compromised. the REF had ongmally concluded that the plant was not outside tht design basis as stated m the SER and FSAR.

• Following reconsiderauon of the design basis requirements and reporting guidance. plant management concluded that the reducuan in fuel oil capaeny was a change to the onginal design basis of the plant.

An immediate noufication, was made to docurnent the revised conclusions.

This event resulted in no significant safety consequences and the EDGs remained operable.

IV Correcth e Acuon No immediate correcuve acuons were required m response to this event. A temporary fuel oil tanker has i been brought to the Millstone site to provide approximately 7,000 gallons of addinonal fuel oil capacity. I pendmg issue resoluuon. i l

A proposed License Amendment to address the reduction in usable fuel oil storage capacity will be I submnted by August 31, 1993. Upon approval of the proposed License Amendment, a revision to the Milistone Umt No. 3 FSAR is also planned.

Gwdance previously incorporated into the operaung procedures with respect to ordering EDO fuel oil '

within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of an LOP, or LOP comcident with a design basis esent, will be incorporated into the emergency response (SERO) procedures. In addinon, gtudance will be incorporated into the emergency response procedures which estabbshes a trigger to mitiate a load sheddmg evaluauon, if a determinanon is made that fuel oil cannot be delivered to the sue as required. Target compleuon date for incorporation of this guidance is July 31, 1993.

A re-evaluauon of the loss of coolant accident and LOP load sheddmg calculation will be performed by October 31, 1993, to demonstrate the ability to extend EDO run umes.

V. Addit!onal Information There hate been no similar LERs with the same root cause and underlymg concerns, j J. F. Opeka letter to US Nuclear Regulatory Commission, dated March 31, 1993, entitled " Millstone Nuclear Power Staten, Unn No. 3, Emergency Diesel Generator Fuel Oil Storage Capacity " provides a hmoncal perspective of the Millstone Unit No. 3 fuel oil storage capaen).

J. F. Opeka letter to US Nuclear Regulatory Commission, dated June 30, 1993, enutled " Millstone Nuclear Power Station, Unn No. 3, Emergency Diesel Generator Fuel Oil Storage Capacny," delineates the cornpensatory measures taken by NNECO pendmg review and approval of the proposed hcense amendment by the NRC staff.

Ells Codes Systems Components Diesel Fuel Oil System - DC Diesel Fuel Oil Storage Tank j and Diesel Fuel Oil Day Tank - TK '

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