ML061780639

Ltr, Tornado and High Energy Line Break Mitigation Strategies

ML061780639
Person / Time
Site:	Oconee
Issue date:	07/12/2006
From:	Chris Miller Plant Licensing Branch III-2
To:	Hamilton B H Duke Power Co
Olshan L N, NRR/DORL, 415-1419
References
TAC MC4608, TAC MC4609, TAC MC4610
Download: ML061780639 (5)

Text

July 12, 2006 Mr. Bruce H. Hamilton Vice Presi dent, Oc onee S ite Duke Power Company LL C 7800 Rocheste r Highway Seneca, SC 29672 SUB JEC T: OCONEE NUCL EAR S TATION, U NITS 1, 2, AN D 3 (OC ONEE 1/2/3) -TORNADO AND HIGH-ENERGY LINE BREAK MITIG ATION STRATEG IES (TAC NOS. MC 4608, MC4 609, AND M C4610)Dear Mr. H amilton: We have completed our rev iew of y our letters date d April 12 , 2006, and A pril 28, 20 06, regarding the propos ed Oconee 1/2/3 mitigation strategie s for tornado and high-energy li ne break (HELB), respec tively. We are encour aged by the apparent progr ess you have made in your plan s towards d evelopi ng these mitigation strategies, wh ich wi ll result in formulating a n ew lice nsing b asis. In ord er to e nsure that y our pl ans ar e full y und erstoo d, we wou ld li ke to schedule a meeting to discuss some key issues related to the proposals that you have made in the referenced lett ers. The issues of part icular interest for this m eeting are described in Enclo sure 1. It is our unde rstanding that y ou wil l be submitti ng license a mendment requests (LAR s) for the tornado-mitigation strategy in Octo ber 2006 and for the HELB-miti gation strategies i n March 2007 for Unit 1, June 2007 for Un it 2, and Se ptember 2007 for Uni t 3. Follo wing the meeti ng on key issues, w e anticipate that you w ill prov ide additi onal docketed i nformation regarding y our plans to add ress th e miti gation strate gies. Enclosure 2 to this letter contains a l ist of the items tha t I recommend yo u address w hen preparing the LARs for the mitigation strateg ies. It is important that these LARs be sufficiently complete to ena ble the Nuc lear Regulatory Commission (N RC) staff to perform the techni cal revi ew th at wi ll be condu cted p rior to the LA Rs bei ng acce pted for further NRC re view. Should y ou have a ny questions regarding this l etter, please c ontact me at (301) 415-1453. Sincere ly,/RA/Christopher M iller, Dep uty Directo r Divisi on of Operating Reac tor Licensin g Office of Nuclear Reacto r Regulation Docket Nos. 50-2 69, 50-270, 50-2 87

Enclosures:

1. Key Iss ues Related to Proposed Tornado and HE LB Miti gation Strategies

2. Issues That Sh ould Be A ddressed in the License Amendment Requests cc w/encl s: See nex t page July 12, 2006 Mr. Bruce H. Hamilton Vice Presi dent, Oc onee S ite Duke Power Company LL C 7800 Rocheste r Highway Seneca, SC 29672 SUB JEC T: OCONEE NUCL EAR S TATION, U NITS 1, 2, AN D 3 (OC ONEE 1/2/3) -TORNADO AND HIGH-ENERGY LINE BREAK MITIG ATION STRATEG IES (TAC NOS. MC 4608, MC4 609, AND M C4610)Dear Mr. H amilton: We have completed our rev iew of y our letters date d April 12 , 2006, and A pril 28, 20 06, regarding the propos ed Oconee 1/2/3 mitigation strategie s for tornado and high-energy li ne break (HELB), respec tively. We are encour aged by the apparent progr ess you have made in your plan s towards d evelopi ng these mitigation strategies, wh ich wi ll result in formulating a n ew lice nsing b asis. In ord er to e nsure that y our pl ans ar e full y und erstoo d, we wou ld li ke to schedule a meeting to discuss some key issues related to the proposals that you have made in the referenced lett ers. The issues of part icular interest for this m eeting are described in Enclo sure 1. It is our unde rstanding that y ou wil l be submitti ng license a mendment requests (LAR s) for the tornado-mitigation strategy in Octo ber 2006 and for the HELB-miti gation strategies i n March 2007 for Unit 1, June 2007 for Un it 2, and Se ptember 2007 for Uni t 3. Follo wing the meeti ng on key issues, w e anticipate that you w ill prov ide additi onal docketed i nformation regarding y our plans to add ress th e miti gation strate gies. Enclosure 2 to this letter contains a l ist of the items tha t I recommend yo u address w hen preparing the LARs for the mitigation strateg ies. It is important that these LARs be sufficiently complete to ena ble the Nuc lear Regulatory Commission (N RC) staff to perform the techni cal revi ew th at wi ll be condu cted p rior to the LA Rs bei ng acce pted for further NRC re view. Should y ou have a ny questions regarding this l etter, please c ontact me at (301) 415-1453. Sincere ly,/RA/Christopher M iller, Dep uty Directo r Divisi on of Operating Reac tor Licensin g Office of Nuclear Reacto r Regulation Docket Nos. 50-2 69, 50-270, 50-2 87

Enclosures:

1. Key Iss ues Related to Proposed Tornado and HE LB Miti gation Strategies

2. Issues That Sh ould Be A ddressed in the License Amendment Requests cc w/encl s: See nex t page Distr ibut ion: PU BL IC R ids N rrP M LO lsh an (H ar d C op y)RidsNrrDorl Dpr LP L2-1 r/f R ids N rrM O'Br ien (H ar d C op y)Ri dsOg cRp RidsNrrDorl Lpl2-1(EMarin os)RidsAcrsAcnwMail Center RidsRgn2Mail Center(MErnstes)RidsNrrDeD(MMayfi eld)RidsNrrDss(TMarti n)RidsRgnII (JShea)Accession Number: ML061780639 NRR-106 OFFI CE LPL2-1/PM LPL2-1/L A RG N-II DS S/D DE/D LPL2-1/BC NAME LOlshan MO'Bri en JShea T M ar tin M M ayf ield EMarinos DATE 7/10/2006 7/7/2006 7/7/2006 7/10/2006 7/11/2006 7/12/2006 OFFICIA L RECORD COPY , page 2 KEY IS SUES RELATE D TO TORN ADO AN D HIGH-ENER GY LINE BREA K MITI GATION STRATEGIES The following issues were generated base d on the Nuclear Regulatory Commission (NRC) staff's review of the tornado an d high-energy l ine break (HEL B) mitigation stra tegy submitted b y Duke Po wer C ompany LLC o n Apri l 12, 2006, and Ap ril 2 8, 200 6, resp ectiv ely. To faci litat e review , the issues have been annotated w ith [T] for torn ado an d/or [H] for HEL B applicab ility.1.Use of TOR MIS[T] The April 1 2, 2006, letter states that the TORM IS computer code will be used to evaluate the probability of damage f rom tornado-g enerated missiles for cer tain structures, systems, and components (SSCs). Add ress the issue s discussed in the NRC staff's October 26 , 1983, TORMIS Safety Eval uation for those S SCs for whi ch TORMIS is us ed. All S SCs that are re lied upon for tornado mitigatio n (includi ng Keowee, a tmospheric dump v alves (AD Vs), etc.) and are not adequately protected (irrespective of fu nction) must be collectively assessed. Physical separation of SSCs is not considere d a viab le option for evaluatin g the effects of tornados.

2.Cold S hutd own[T/H] Discuss ho w cold shutdown w ill be a chieved, includin g: a.) a defined ti me for achievi ng cold shutdow n (e.g., 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />); b.)

recognition of the strategy/systems to be used (e.g., res idual heat r emova l (RH R), lo w-pre ssure s ervi ce wa ter, hi gh-pres sure injection (HPI), pressur izer heaters, ADVs, instrument s, etc.; c.) identif ication of specific vuln erabi liti es tha t need to be addres sed, e quipmen t to be staged (e.g., ca ble, e tc.); and, d.) a human fact ors assessment of effort/repair that is consistent with the NRC revi ew st andard s/guida nce. 3.Technical Sp ecifications

[T/H] To ensure lic ensing-basis c larity an d component ope rability , Technical Speci ficatio ns (TSs) need to pro perly addre ss the tornad o/HEL B miti gation syste ms (e.g., prot ected service water/HPI, standby shutdown facility, etc.) in a manner that is consistent w ith the Stand ard TS requirements th at have be en establis hed for the functions that are being performed by these syste ms. For exampl e, the minimum require d miss ion ti me shou ld be 7 day s and the Co mpleti on Time s shou ld be limi ted to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in most cases.

4.Reactor Cool ant System Le tdown Li ne[T/H] The reactor cool ant system le tdown li ne exits containment and enters the eas t penetration roo m, where it presents an HE LB concern an d could po ssibly be damaged by to rnado-generat ed mis sile s, resu lting in a s ignific ant lo ss-of-co olant accid ent. Discuss how this vul nerability will be addressed , includi ng the possibi lity of mov ing the flow-l imiti ng orifi ce in side contai nment. Enclosure 1, page 2 5.Applicati on of Generic Lette r 87-11[H] The April 28, 2006, letter discusses k ey concepts and assumptions for HELB.Regarding break and crack postulation addressed un der the fifth concept/as sumption, discu ss if al l of Gen eric L etter 8 7-11, "Relax ation of Arbi trary Interme diate Pipe Ruptu re Requirements," w ill be a pplied, or the specific ex ceptions that are planned to be requested.

6.Protection of El ectrical Pen etrations[H] Aff ordi ng pr otec tion to onl y thos e elec tric al pen etr atio ns ne eded for saf e shu tdown (as indicated in the April 28, 2006, letter, Mitigation Function 4) may not be all that is needed, assumi ng that water a nd foreign material gets in all non-sealed enclosures from water spray or steam. If the encl osures are to b e replaced o r modified, the ne w or modified enclo sures should be qualified by test, ex perience, or a nalysis in accordanc e with the requirements of Title 1 0 of the Code of Fede ral Regula tions (10 CFR), Part 50, Section 50.49

. , page 1 ISSUES THAT SHOULD BE ADDRESSED IN THE LICENSE AMENDMENT REQUESTS The comments below were generate d based on the NRC staff's rev iew of the to rnado and hi gh-energy line break (HELB) miti gation strategy su bmitted by D uke Power C ompany LLC on April 12, 2 006, and Apri l 28, 2006, respectivel

y. To facili tate review , the comments hav e been annotated w ith [T] for torn ado an d/or [H] for HEL B applicab ility.1.[T/H] Analyse s, codes, and/or models bein g utilize d that need to be integrated i nto the quality ass urance manual

/commitments should be addressed in the app licable license amendme nt reque sts (LA Rs). 2.[T/H] The LARs should discuss any scenarios where the reactor coolant system (RCS)does not stay sub-cooled with a p ressurizer s team bubble.

3.[T/H] Communication s for assuring that the necessary action times a re not excee ded for establishi ng secondary heat removal and reactor co olant pump (RC P) seal in jection should be discussed.

4.[T] Discussio n is neede d to justify the conclusion that equipment i n the east pen etration rooms is largely protected by adjacent st ructures (i.e., low probability of missile damage). 5.[T/H] Additiona l expla nation shoul d be provi ded regarding the p rotected swi tchgear (PSG), such as h ow the al ternate underground cable/suppl y to the PS G is routed (directly from Keowee or from CT-4), and if there are any tornado or HELB vulnerabi lities to the power supplied to or from the PSG othe r than Keow ee (i.e., outsi de connections in and out of its protected bu ilding, inte ractions w ith the sw itch yard, tu rbine building i nterfaces, etc.). Descri be how th e alternate po wer suppl y from the PSG to the standby shutdown facility (SSF) will be protected from a torn ado and from where it will be controlled. Describe to what extent it will be credited as part of the tornado or HELB-mitigation strategie s, and how this capabi lity w ill be a ssured, or if it i s considered to be defen se-in-depth on ly.6.[T/H] Considerati on should be given to alternativ es to routing the new protecte d serice water (PSW) pipe through the penetration ro oms (for example, b elow grade may be an optio n.) 7.[T/H] Any depen dencies rel ated to the prote cted servic e water sy stem and high-pressure injecti on (HPI) pumps s hould be d escribed (e.g., coo ling, lubric ation) and justified as app ropriate.8.[T] The analy sis of the control battery room e xternal w all shoul d be discus sed for those cases whe re tornado-relate d modifications will not be performed.

9.[T/H] Prov ide th e basi s for PS W/HPI and SS F ini tiati on time s and confirma tion t hat a human factors assessmen t has been co mpleted that i s consistent w ith the Nucl ear Regulatory C ommission (NR C) review standards and guidance to v alidate op erator actions and times. Enclosure 2, page 2 10.[T] The most limiti ng tornado-related main steam li ne ruptures and their impact to the overall tornado mitigatio n strategy shoul d be describ ed, includi ng any pla nt modifications d eemed necessary to preclude adverse effects.

11.[T/H] The borated w ater storage tank (BWST) critical lev el and the basis for this l evel should be discussed (e.g., co ol down , RCS leakage, R CP seal l eakage, high point vent loss, etc.). Al so, how forei gn material (e.g., ins ulation v ia missil e impact, etc..) w ill be kept from entering the BWST above the c ritical prote cted area shou ld be dis cussed.12.[T/H] Sinc e the r eactor head and/or high-p oint v ents w ill be use d for RC S inv entory control, descri be how u sing these v ents wil l affect containment p ressure and di scuss the environmenta l effects on the SSF makeup pump.

13.[T/H] Instrument f ailures (e.g., press urizer level, etc.) and how they will be discerned in support of main co ntrol room and/o r SSF control should be discussed.

14.[T/H] The means for assuri ng a sufficient wa ter supply for the SSF make-up pu mps and spent fuel pool s should be described.

Also descri be how c riticality concerns asso ciated with the spent fuel pool will be addressed

.15.[T/H] Discuss the RCP seal model that w ill be u sed, includ ing the condi tions and limit ation s of the appli cable topic al rep ort as it rel ates to the Oco nee 1/2/3 tornado/HELB-mi tigation strategies.

16.[H] The Ap ril 2 8, 200 6, let ter di scusse s key c oncep ts and assump tions for HEL B. Under the first co ncept/assumption, structures, systems, and components (SSCs)necessary to reach safe shutdo wn (SSD) will be protected from the p ossible di rect effects of a given HELB event. In that regard, additi onal discu ssions shoul d be provi ded to e xp la in if: a.Protection from possi ble HELB effects on SSCs nece ssary to reac h SSD als o incl udes s upport ing equi pment a nd the automa tic feed wate r isol ation syste m, and b.SSCs satisfy environmenta l qualificatio n requirements Also, discu ss the break loc ations and e ffects/strategies that were used in di scerning required SSC H ELB-related p rotection.

17.[H] Und er th e thi rd co ncep t/as sump tion , it was ind ica ted t hat j et ge omet ry fr om br eaks and cracks wi ll be bas ed on NURE G/CR-2913, "Two Phase Jet Loa ds," pending approval from the NRC. In tha t regard: a.Since NUREG/CR-2913 applies to breaks, justification fo r applying this NUREG to cracks should be provid ed b.The ass essmen t shou ld be site-speci fic (i.e., the i ndica ted 10-pipe diame ters may not prov ide a large e nough zone o f influence for potenti ally affected S SCs) Enclosure 2, page 3 18.[H] Under the fourth c oncept/assumption , no breaks or crac ks will be postulated on systems that op erate at high-ene rgy conditio ns less than 1 percent of the total plant operating time or less than 2 percent of the total system operati ng time. Additi onal explanati on is need ed in the foll owing areas

a.How sy stem percentages are justified/confirmed b.How far back the associated o perating histori es are assesse d and if this is a periodic as sessment c.Subjec t pipi ng shou ld be anal yze d in a ccorda nce w ith th e Upda ted Fi nal S afety Analysi s Report in order to preclu de break and crac k postulation b ased on limited sy stem operation p ercentages d.Aside from the in dicated emergency feedwater (EFW) and low-pressure injecti on systems, any others for whi ch break and crac k postulation i s being precl uded based on l imited sys tem-operation perc entages should be identified 19.[H] The April 2 8, 2006, letter discusses miti gation functions for HE LB. Regarding structure failures addressed und er Mitigati on Function 1: a.The LAR shoul d list pi pe inspecti ons being performed (i n lieu of i mplementing modifications for struc tural components) and provi de the reason that modifications w ere considere d not feasible

.b.GOTHIC Code 4.0, which is to be utilized in calculating pressurization eff ects in the au xil iary buil ding, s hould be be nch-mar ked and captu red in the qua lity assurance program c.Describe the worst-case break for pressure in the east penet ration room and if the block w alls fail b efore the blow out panels.

If they do fail before the blow out panels, explain why this is acceptable 20.[H] Under M itigation Fun ction 2, it i s indicated that no sy stems and compone nts located in the turbi ne buildi ng (TB) will be credited for initial H ELB-event mi tigation or for reaching SSD, except for tho se systems and components necess ary to protect the main steam (MS) pre ssure boundary. Those systems and components necessary to protect the M S pres sure b ounda ry w ill be pro tected from the effects of a give n HEL B eve nt, includin g, jet impingement, env ironmental effects, spray , and flooding.

In that regard:

a.Discuss if emergenc y feedwater (EFW) and/or main feedwater (M FW) will be credi ted for r ecov ery b.Describe w hat wil l cool HP I and PSW, and address the function of the atmospheric dump valves in supporti ng PSW operation Enclosure 2, page 4 c.Describe the worst-case effect of an M S line bre ak in the TB and the strategy for mitigat ion. (Inclu de pos sibl e effects on SS F-cont rolle d compo nents with associ ated c ables in th e TB.)21.[H] Regarding Mitigation Function 3, discuss how long the main cont rol room will remain habitable and how long its equipme nt will remain functiona l should control room venti latio n be l ost foll owi ng an H ELB e vent.

Oconee Nucle ar Station, Un its 1, 2, and 3 cc: Ms. Lisa F. Vaughn Duke Power Company LL C 526 South Ch urch Street P. O. Box 10 06 Mail C ode EC07H Charlotte, North Carolina 28201-1006 Mana ger, LIS NUS Corporati on 2650 McC ormick Dr., 3rd Flo or Clearwate r, FL 34619-1 035 Senior Resi dent Inspector U.S. Nuclear Regulatory C ommission 7812B Roche ster Highway Seneca, SC 29672 Mr. Henry Porter, Directo r Divisi on of Radioacti ve Waste Management Bureau of Land a nd Waste Management Dept. of Health and Env. C ontrol 2600 B ull S t.Columbia, S C 29201-170 8 Mr. Mi chael A. Sc hoppman Framatome ANP 1911 N orth Ft. My er Dr.Suite 705 Rosslyn, VA 22209 Mr. B. G. Dav enport Regulatory C ompliance M anager Oconee Nucl ear Si te Duke Energy Co rporation ON03RC 7800 Rocheste r Highway Seneca, SC 29672 Ms. Karen E. Long Assistant Attorn ey General NC Department o f Justice P.O. Box 629 Raleigh, NC 27602 Mr. R. L. Gil l, Jr.Mana ger - Nu clear Regul atory Issue s and Indust ry Affai rs Duke Power Company LL C 526 S. Churc h St.Mail S top EC05P Charlotte, NC 28202 Divisi on of Radiati on Protection NC Dept of Environment, Health, & Natura l Resources 3825 B arrett D r.Raleigh, NC 27609-7721 Mr. P eter R. Harde n, IV VP-Customer Rel ations and S ales Westinghouse Electric Compan y 6000 Fairv iew Roa d 12th Floor Charlotte, NC 28210 Mr. Henry Barron Group Vice Pre sident, Nucl ear Generation and Chi ef Nuclear Officer P.O. Box 100 6-EC07H Charlotte, NC 28201-1006 Mr. Charle s Brinkman Director, Washington Operations Westinghouse Electric Compan y 12300 Twin brook Parkway, Suite 330 Rockville , MD 20 852