ML11346A510

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State of New York (NYS) Pre-Filed Evidentiary Hearing Exhibit NYS000021, OECD, Nuclear Energy Agency, Operating Experience Report: Recent Failures of Large Oil-Filled Transformers, NEA/CNRA/R(2001)6 (Mar. 14, 2011) (NEA Report)
ML11346A510
Person / Time
Site: Indian Point  Entergy icon.png
Issue date: 03/14/2011
From:
Govt of France, Nuclear Energy Agency
To:
Atomic Safety and Licensing Board Panel
SECY RAS
References
RAS 21523, 50-247-LR, 50-286-LR, ASLBP 07-858-03-LR-BD01 NEA/CNRA/R(2011)6
Download: ML11346A510 (26)
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Q'I Unclassified Organisation de Cooperation ef de Developp,:ment Ecc>nomiquo:s Organisation for Economic Co-operation and Development

~TCLE...\\R ENERGY AGENCY COi'VIM1TTEE ON Nt':CLEAR REGULATORY ACTTVlTIES CanceL~ & replace~ tile ~ame document of 11 :\\.fal'~h 2011 OpE'l'ating Expel'i(,IH"(' R(,POl't:

Rec(>nt F:dlures of Lltl'ge Oil-Fm",d TnnsforIllf'l's Working Group on OperatiIlg Exp(>rienc(' (\\YGOE)

JT03298131 Doeum.,,' camp!et di,ponible <D!' OLIS dans ron format d' origine Complet~ document available on OLIS in its <>1'iginal format NEA/Cl';'RAIR(20 11)6 14-Mllr-2011 Englisb text only OAGI0001166_00001 NYS000021 Submitted: December 12, 2011

1'.:'EAiCNRA/R/(20 11)6 ORGA~lSATION FOR ECONOl\\UC CO-OPERI\\TION A..l",,"D DEv"ELOP:\\lENT TIle OECD is a lUlique forum where the govemments of34 democracies work together to address the economic. *,.oci3l 3nd environmental challenges of globllllsati0l1, The OECD is aho at the forefront of efforts to understand 3nd to help governmenis re~pDnd fJ:, ne\\v development~ and conc,enl'>, such as cOlporate governance, the infommlion economy and the chal1engeb of an ageing population. TIle Otgani~ation provides a i>clting where go,emmenh can compare policy e.xperiences, seek an<;\\vers to common problems, id.:11tify good practice and work to co-ordinate domeMic a11d international policies.

The OEeD member countries are: AustIalia" ft.usiria, Bdghml. Canada, Chile, the Czech Republic, Denmark Estonia, Finl,md, France, 0e11l1ally; Greece, Hung<lry, Iceland. Ireland, Israel, Italy, Japan, Korea, Luxemhourg. Mexico, the Netherlllnds, New Zealand, Norway. Po13nd, Portugal, the Slovak Republic. Slovenia. Spain, Sweden, Switzerland, Turkey.

rhe United Kingdollland the United Stales. TIle Em'opean Cmmllission takes part inlhe work of the OECD, OECD Publishing disseunnates widely the results of the Organisation's st<llistics gathering and research on economic.

social and environmental i%ue~, a~ w0:113,<; the conventions, guidelines and standal"d~ agreed hy it, memhers.

This work is Jmblished on the responsibility" of the SecITtary-General of the OEeD, The opinions expressed and arguments e;lIIployed herein do not necessmiiy t"f';f/ea the ~lficial views of dw Organismion or qlthe govenmwnts c:f its member cOlllltries.

NlJCLEAR ENERGY AGENCY The OECD Nudear Energy Agency (NEA) wa~ e"tablished on 1;:1 Febmary 1958 tmder the name of the OEEC European Nudear Energy Agency It re<ceived iis prei><!rlf designation on 2ot~ April 1972, when Japan became it~ first n011-European fun member, 'N'EA membership today c011~i~ts of 29 OEeD member cOlUltrie,: Austl*alia. Austria. Belgium, C3nada, the Czech Republic, Dell11k1rk Fi1lland. France, Gennan}~ Greece, Hungal)', lce13nd, Ireland. It3ly, Japan. Kc<reae Lu."embomg, Mexico. the Netherlands, Norway; Poland, POltllgal, Ihe Slo\\'ak Repllblic, Spain, Sweden. Sv,itzelbnd, Turkey; rhe Uniled Kingdom and the Unired Stares. The Em'opean Cmillllls,ion also takes part in the work of the Agency.

The ml&sion of rhe NEA is:

to as,;ist its member countries in maintaining and fill'ther developing, thlUugh i1ltemational oo-operatimL the

&Ciellliiic. technological ll1ld legal hases required for a sak e1lvironment3Hy friendly ll1ld econmrucal me of nuclear energy tor pe3ceful pmposes. llS well as fo provide mlihoritative assessments and to forge <:DllmIDn understandings on key is,ue~, as input to government decisi0115 on nuclear energy policy and to broader OEeD policy analy,es in al'ea, &11Ch 3S energy and. sust3mahle deYdopmem.

Specific at'eas of competence of rhe NEA include safery and reglilation of mlclear 3ctivities, mdioactive waste management. radiologic1l1 protection, nuclellr,cience, ecmlOnnc and technical anlllyses of the nuclear filel cycle, nuclear law and liahility, and public information.

The NEA Data Bank provides nudear data and cDmputer progralll service" for participating countIies. In these and related tasks. the ~~A \\vorks in elme collahoration with the Intemational Atonllc Energy Agency in '-lenna, with which it hlls a Co-oper3timl Agt'eement, as well as \\'lith otller intematimilll org3ni,atiollS in the mldear field.

Corrigenda to OEeD public"tic",,, may be fGUtld online at: """,,oecdorg/pubiisilW'e<mig<?ndt:i,

'1;:. OEeD 21111 You C1lll copy. download {)f print GECD content fi.)f your own use. and yvu can mdude "X<:eIl'ts from GEeD :pubhc;rtions, datah"ses alld multimedia product, in,?"'>U- {)\\~11 docwnent" p1,,"'"tatiOll~., blogs, website, and !ce3chillg material<, p1m~iIed that,,,itable adcnowledgment of OEeD a~ smn-c" ;md C<Jfryl-ight o"'"Iler i, gi"ffi, All req"";"ts for public or c{)mm<'n:ia1 u,,, 01"0. =~latiOll right~,hmlld \\x, submirte,f Iv righf!i@oecda"!J_ R""jl=ts fur pennis>;on to :photoC<JPY P'-',-tlons ofillis ""'l",-inl f{)r public or commercial u;e,hall be addressed dil:ectly to the

. (:op':l~~ht C:lem*unceCente1: <<('c;c). at i'lfo({!:coPY,7ght.<: af}) ofllie C;""rre ff""~ai~ d'explO1tat1oll dudr{)1tde copie <<('1'C) conr"ci(ij;rjcopit""Caf}).

OAGI0001166_00002

1'.:'EA/Cl';"'RAtRi{ 2011)6 COM:\\UTTEE ON l\\'[TCLEAR REGVLATORY ACTIVITIES The Committee on Nudesr Regulatory Activities (CN~A) shs11 be responsible for the programme of the Agency conceming the regulation, licensing and inspection of lluclear illstallations with regard to safety. The Committee sllall constitnte a tbnull for the eftective exchange of satety-relevant infbmmtion and experience among regulatory orgmlisations. To the extent appropriate, the Committee shall review developments \\vhich could aftect regulatory requirements with flle objective of providing members with an understanding of the motivation for new regulatory requirements under consideration snd an opportunity to ofter suggestions that might improve them and assist in tIle developmellt of a COlIllnOll understanding among member counoles. In pmticular it shaH review OUTent nmnagement strategies and safety management practices and operating expeliences at nudear facilities with a "iew to disseminating lessons leamt. In accordance with the I>.i'EA Strategic Plan for 2011-2016 and the Joint CSNIiCNRA Strategic Plan and I-,*1andates for 2011-2016, the Committee shall promote co-operation aIllong member countries to use the feedback iiom experience to develop measures to ensure higll standard.s of safety. to ftuther enhallCe efficiency alld effectiveness in the regulatory process and to maintain adequate iniiastmcture and competence in the nudear safety field.

The COlmmttee shs11 promote transpm'ency of nuclem' safety work mId open public communication. The Committee shall maintain an oversight of all NEA work that may impinge on the developmellt of effective and efficient regulatioll.

Tile Committee shall focus primarily on the regulatory aspects of existillg power reactors, other nuclear installations snd the constmction of new power reactors: it may also consider the regulatory implications of ne\\;I,i designs of power reactors and other types of nuclear installatiOlls.

Fm1hennore it shaH examine any other matters refelTed to it by the Steering Committee. The Comlmttee shall collaborate with. and assist as appropriate, other international organisations for co-operation among regula top; and cOllsideI~ upon request issues raised by these organisations. The Committee shall organise its ovm activities. It may sponsor specialist meetings alld working groups to further its objectives.

In implementing its programme the Committee shall establish co-operative mechmlisms with the Committee on the Safety of Nuc1eaT Installations in order to work \\;l,iifll that Committee on matters of COIllmon interest. avoiding ullnecessary duplications. The COlIlluittee shaH also co-operate w*ith the COllllmttee on Rsdiation Protection and Public Health and the Radioactive \\Vaste Management Committee on matters of COlIllnOll interest.

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1'.:'EA/Cl';"'RAtRi{ 2011)6 Tile NEA Committee on Nuclear RegulatOIY Activities (CNRA) believes that sharing operating experience from the national operating experience feedback programmes are a major element in the industry's and regulatory body's et1brts to ensme the continued safe operation of nuclear facilities. Considering the importance of these issues, the Committee on the Safety ofNudear Installations (CSNI) established a working group, PWG #1 (Principle \\Vorking Group Number 1) to assess operating experience in the late 1970's, \\;vhkh \\vas later renamed the \\Vorking Group on Operating Experience (WGOE). In 1978, the CSNI approved the establishment of a system to collect intemational operating experience datiL The accident at TIuee I-,*1ile Island shortly after added impetus to this and led to the st31t of tile Incident RepOlting System (IRS).

In 1983, the IRS database \\;vas moved to the Intemational Agency for Atomic Energy (IAEA) to be operated as a joint database by L<\\'EA and NEA for the benetIt of all of tile member countries of both organisations. In 2006. the \\VGOE was moved to be under the umbrella of the Connnittee on Nudear Regulatory Activities (CN""R.A.) in NEA. In 2009. the scope of tile Incident RepOlting System w'as expanded and re-named the International Reporting System for Operating Experience (although, the acronym remains the smne).

The pUI})Qse of WGOE is to facilitate the excbSllge of infonnation, experience, SlId lessom leamt related to operatillg expelience bet\\veen member cotmtries. TIle working group continues its mission to identify trending and issues that should be adch'essed in specialty areas of C"N""RA and CSNI

'working groups.

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1'.:'EA/Cl';"'RAtRi{ 2011)6 TABLE OF CO~lE~lS Foreword.............................................................................................................................. 5

1.

Background............................................................................................................. 9

2.

Failmes ofLaJge, Oil-Filled TransfOlmers and Risk Signific.ance..................................................... 11

3.

Questiolllaire Issued to Member States............................................................................... 13 3.1 Questions for the Regulatory Body............................................................................... 13 3.2 Questions for the Operating Organisation........................................................................ 13

4.

Analysis and Conc1usiollS............................................................................................ 15 4.1 COlUltty Inputs...................................................................................................... 15 4.2 Recent Events...................................................................................................... 15 4.3 Summary of Countries' Respollses................................................................................ 16 4.4 Commendable Practices............................................................................................. 17

5.

Response of OECD-1'.:'EA Countries to Transformer Failure Questions............................................. 19 5.1 Belgium.................................................................................................................. 19 5.2 Canads................................................................................................................. 19 5.3 Czech Repuhlic........................................................................................................ 20 5.4 Fll11allcl.,..,.......... ~.............. "......... ".... ".........,..,.,........ ~..............,......... ".,..........,.. ",.20 5.5 GelTIlany............................................................................................................... 21 5.6 Japan................................................................................................................... 21 5.7 Netllerlands............................................................................................................ 22 5.8 Slovakia............................................................................................................... 22 5.9 Republic of Korea (SOUdl Korea).................................................................................. 22 5.10 Spain.................................................................................................................... 23 5.11 S1;vitzerland............................................................................................................. 23 5.12 United States........................................................................................................... 24 Appendix: Japanese Typical Recommended Transformer ~'ilaintellance Prognull...................................... 25 OAGI0001166_00007

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1'.:'EA/Cl';"'RAtRi{ 2011)6 L BACKGROUND A main activity of the WGOE is to review events and trends from operating experience that have safety issues \\;'lith generic impOltance and need to be addressed from a regulatory viewpoint.

From this activity perfonued by WGOE recommendations are provided to the CNRA. on regulatory issues and the Committee on the Safety of Nuclear Installations (CSl'<T) on technical and scientific issues.

At the I-,.1ay 2009 meeting of the WooE, tranSf0l111er failures were discussed as an issue of generic impOItance. The US "N""RC llad identified that transfonner failures had all increasing trend.

Transformers are non-safety related equipment. As such.. the maintemmce practices are generally outside of the regulatory purview. The lJS NRC developed a short questionnaire to discuss tlle regulatory treatment of transfonners and the operating experience in the member countries. At tlle conclusion of the discussion. tIle members decided that sufficient info11nation and interest was available to support a task on large oil-fllled transfonners.

In December 2009. the \\VGOE was granted CNRA approval for a task on transfonuer failures.

The United Srates and Callada vohmteered to suppmt the task. A more detailed questionnaire was develoPed for the member countJies to contribute their operating experience on transformer fsilures.

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2.

FAILITRES OF LARGE, OIL-FILLED TRANSFOR\\JERS Al'£) RISK SIGj'\\IFICAl'i'CE 2.1 Large Oil-Filled Transformers Large oil-filled transfomlers provide the primary connections benveen the nudear power plant and the e1ecttic gIid. \\\\-'ith the main generator transfonner providing output to the gIid and lmit and station amdliary tJans!omlers providing offsite pow'er to the plant. Rated at tens or lumdreds of thousands of megavolt-ampere (l'vfVA) these high energy systems are otten maintained by outside COIlU'actors. and i.nvolve multiple suppotting components. including cooling systems. surge atTestors, bushingslinsulators, and control systems, all of which must be properly maintained in order to provide for tile safe operation of the tramfonner.

2.2 Risk Significance

\\Vith the exception of some muiiliary tram!ormers which tlmction as part of the onsite electrical distribution systems, large. oil-filled transformers are generally considered to be non-safety related equipment. Their primary ilmction is continued power production. and they are not relied upon tbr the safe shutdown of tIle reactor. As such. tailures of large transformers generally are not, in and of themselves, required to be repOlted. nor are they covered by specific regulatory requirements.

Though they are not considered nuclear safety equipment, dle failure of a large transfonner at power usually results in a reactor trip. The complications associated with a transformer failure, induding fire, electrical distribution dismption. emergency declarations, mld hazards to personnel, create distractions for operators and call complicate efforts to maintain dle reactor in a safe, shutdovm condition.

2.3 Broadt'I" Implications for Safety-Rdated :\\laintenanct' Programmes Indusuy operating experience identifIed a COlEtant trend in transfonner failures over a ten year period despite a conceIted effort to identify and correct the leading causes of the failures. While some failures can be traced to weaknesses in the manufacturing process or desigIl vulnerabilities in essential support systems, the root cause for lllany failures are 'wealmesses in the maintenance and monitoring programmes.

To the extent that transfOlmers aTe covered by nuclear safety regulations at all.. it is through regulations in some countri.es dmt require plant maintenance progI'anllnes in general to meet acceptable standards. Successful maintenance progI"llilllneS 'will not only determine tbat testing results are within speci!1cation, but will trend results to note if there is a deteriorating condition, or if there bas been a step change that could indicate imminent failure.

Analysis of dIe transfonner oil, palticularly analysis of the gas content.. which increases due to breakdovin of the oil caused by hot spots and faults in the transformer, can provide an indication of the overall healdl of the u'ansformeI:

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3. QUESTIONNAIRE ISSl'ED TO MEl\\ffiER STATES 3.1 Questions for the Regulatory Body A.re there regulatOlY requirements for the maintenance of large transfonners? If so, what are they?

A.Ie tilere regulatory requirements for repOlting transformer failures? If so, *what are they?

",<11at parameters does your regulatory body monitor. trend. and anslyse tor large trans tanners to detect degraded conditions?

3.2 Questions for the Operating Organisation

\\'<l18t parameters do operators monitor. trend, and analyse tor large transtormers to detect degraded conditions?

Are single-poim failure \\'ulnerabilities, potelltial sources of spurious transfonner hips that can cause an improper acmation of a single relsy or component considered?

Does the operator have a predictive and preventive maintenance programme tor large transfonners? Describe the tlmnework oftlle progranune.

Does it include. tmllSfonner years of service, risk impOltance, duty cycle. tmnsient cycles, and environmental conditions?

Does the operator have a contingency phm for transformer inspections if a sigllitkallt degraded condition exists?

Does tIle operator conduct detsiled maintenance rounds on major station trans fanners and spaJe transtOl1l1ers?

Do seasonal and operating conditiom; affect the depth of tlle maintenance rounds?

Does the operator have suffkiently detailed operating and abnormal procedures related to transfonner activities?

Does tlle operator have clear job responsibilities tor trausfonner operation. maintenance, and perfbmlance monitoring?

\\VI1O verifies transfbnner maintenance activities by contractors or omite organisations?

Training and knowledge:

Is appropliate training illduded with inu:eqnent transt0l1l1er activities?

Are onsite personnel kllowledgeable and proficient at maintaining dIe large transtonner?

Does the operator provide training fbI' the station !lre brigade. non-licensed operators. and the contn.,1 room operators Oll transfonner fire response? Tllis training may consider dIe possible isolation oftile lInit from the grid. as \\¥ell as isolation of the site fiom the grid, 13 OAGI0001166_00013

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4. Ai'l"ALYSIS Al\\'D CONCLUSIONS 4.1 Country Inputs TItis report documents inputs received 11'0m t\\velve cOlll1tries regaJding maintenance and regulations associated with oil filled transfonners. These respom;es came from:

Belgium Canada Czech Republic Finland Gemlany Japan Netherlands Slovakia Republic of Korea (South Korea)

Spain Switzerhmd United States Though generally classitied as power generation systems rather thal1 nuclear safety systems, transformer failures have the ability to affect safety related systems. as \\¥eU as to pose a hazard to site personnel. Ageing systems lllay be more sHsceptible to failure, making lessons kaillt 11'om previous event and best practices a valuable operating experience tool.

4.2 Recent Events The United States issued Infonnation Notice 2009-10 (IRS 8024) sdclressing conce11lS about mallltellance issues 101' msill transfonners after observing a significallt illcrease in the number of 1ailures despite industry guidance providing recommendations. Genmmy posted IRS 8049 describing complications following a transfonner tIre that revealed weaknesses in the ventilation system design as smoke iiom the fire \\¥as ch'awn into the main control room. IRS 7928 from the United Kingdom desclibes an event w'hich challenged operators with a reactor trip, fire, snd scattered debris after a high voltage bushing on the main tran<;tonner exploded. Seisullc e1Iects following an earthquake in Japan caused a fire due to grounds all one of the main transformers as described in IR:S 7922. The event,vas complicated as the water supply tor frretighting etlons was also disabled by dIe earthquake.

IRS 8008 1t-om Russia on the other hand. describes an event w'here alarms received in the control room alerted operators to tIle deteriorating condition of the tmnsfonner insulation. allowing them to trip the transfonners be10re a catastrophic failme occulTed. IRS 8011 from l\\rgentiua and IRS 7947 1t-om Lithuania describe situations where inadequate maintenance procedures mId design features resulted in actuation oftrall<;t0l1l1er trip features, requiring reactor scrams, 15 OAGI0001166_00015

1'.:'EAiCNRA/R/(20 11)6 4.3 Summary of Couutries' Respouses Several general conclusions can be dravm from the various responses received. Transtonllers are not regarded as nuclear safety equipment in any CotUltry, and as such no country t1mt responded (with the exception of Republic of Korea. which includes tnmsfonners in its regulations for peliodic inspection by regulatory body inspectors) had regulations specifically addressing transfonner maintenance.

Likewise. no country had a specific reporting requirement regarding tran.sformer failures.

Recognizing that tramtonller failures can lead to reactor trips, most cOlllltries do have regulations addressing maintenance programmes in general, and inspections to verify the effectiveness of these maintenance programmes.

In addition. reportability requirements addressing tile consequences of most u'ansformer failmes (reactor trip, extensive fire), effectively capture the vast maj ority of the catastrophic failmes.

Licensee maintenance and monitoring programmes are generally stmctured around available industry recommendations and operating experience.

Key operating parameters induding oil temperatme alld leveL along with cHlTents, voltages and capacity factor are available in the conu'ol room, or at least will cause ala1ms in the control room in the event of an abnol1l1:'l1 condition. Visual inspections are generally canied out on a shiftly or daily basis. and preventive maintenance is scheduled regulally~ usually 'with major overhauls and assessments made every several years to verify that no signit1cant degradation has occUlTed. I'vlany licensees hsve adopted continuous online gas analyzers to trend the gas content in the tratlst0l111er oil tl.lr indication of insulation or dielectric breakdowll. Those that do not have the online analyzers installed perform oil analysis at least annually. The industry recommendation is that new main transfonners have online gas analyzers included. and that operating tramtl.lnners be retrofttted if there are indicatiom of possible deterioration.

As tJanstomlers are not considered nuclear safety equipment. many of them do not have redundancies built in and are thus vulnerable to single point failmes. IndustlY guidance recommends analyzing areas snsceptible to single point failure to detennine the risk to tile u'ansformer and the feasibility of adding redundancy. Some operators have redlmdam main transfonner nip relays to minimize spUlious uips, but inmost counuies they have determined that the trip risk from other large transtormers is sufficiently low that redlll1dmlt features are not necessary or cost-effective.

All licensees have detailed procedmes addressing the plant response to a reactor u'ip caused by a tmnsfonner failure, and most plants have abnormal operating procedures adckessing other concerns that may arise as a result of the failure.

l'vfany plants have follO\\ved industry recommendatiOlls to develop procedures to address paJameters that fall outside tile normal range, or which indicate a deteriorating trend.

These procedures may require increased monitoring and maintenance, or set limits for taking additional actions, including taking the transformer offline to avoid a catastrophic failure.

Nuclear plants in most countries do not maintain sufi1cient personnel onsite with the experience and training necessmy to pelfonn maintenmlCe 011 traIlSformers, and so this maintenance is usually contracted out.

Plant persomlel maintain over~ight of contractor activities, and require adequate knowledge of the system to ensure that work is pertomled to site standards and meets regulatory requirements. Industry operating experience has highlighted the use of outside contractors as a possible source of concem for transfonner maintenance. especially if the procedures, training, and acceptance standards are not sutlicient Updated industry guidance suggests that the licenSee be involved at every stage of contracted maintenance (including from dIe time of Oliginalmanufactnre) w*ith testing mld inspections to ensure the required level of quality is msintained.

Another common theme among all of the responses was in the area of tire fighting. Though in many countries training for licensed and non-licensed operators "vas for a general approach to fires and their potential effects on the plallt. licensees in all coullllies pro\\'ided the fire bligade with training 16 OAGI0001166_00016

1'.:'EA/Cl';"'RAtRi{ 2011)6 specifically for transfonner fires. l'vfultiple countties cited operating experience fi'om previom fires, in particular the transfonner fire at Krummel Nuclear Plant in 2007, as providing valuable lessons learnt for complicstions that cml arise from this type of t1re.

4.4 Commendable Practices Tbe primary concern for a plmlt operator upon loss of a main tnmsfonner. once immediate actions to place tbe plant in a safe condition are complete, is the availability of a replacement. The long lead time necessary for the manutacture of a ne\\;I,i main transformer means that if there is no functional spare tram;tOl1l1er available, the plant \\,",ill remain shut down tor an extended periOl.i of time.

As this is not a nuclear regulatOlY concern. indllsuy groups have generally taken the lead in addressing transformer failures. preventive measures to be taken. and recommendations tor millimizing t11e potential for catastrophic failure.

Aside trom the initiating event (loss of pmver, reactor scram etc.) \\,",hic11 is likely to result from the failure of s large transformer, nucleill' regulators have seen other causes for concern from a spate of recent failures.

Catastrophic failures of the main transformer challenge operators with distractiom; from tIre, affected equipment, and the coordination of emergency operations \\vhile they place the plmlt in a safe. shutdmvn condition. Fires and explosions pose a hazard to personnel and equipment and contribute to the difticulty ofrestorillg normal conditiolls.

Predictive and preventive maintenance is key to maintaining eqnipment, and to detecting any degrading conditiolls before dley pose problems for operation.

All plants have maintellance procedures detailing work to be performed or parameters to be observed at regular intervals. A programme dIat takes into account dIe cOlldition ofthe transfonner dmlng these mailltenance illtervals in order to inform future maintenance requirements can help to extend the opemting life of the transfonner and aid in detection of impending problems in time to prevent a catastrophic failure.

Japall has developed a trausformer life management evaluatioll programme 'which incorporates time-based mmmgement snd condition-based management slong with life cycle management sssessments at twelve and t\\venty-tour years, to detenuine future transfonner mailltellllilCe alld replacement requirements (see appendix).

Poor oversight of contracted maintenance personnel mId a lack of understanding by plant personnel of main transfoflllers have been highlighted by industry groups ss a possible contributor to trmEt"i../nner tailures. ?\\*lost lluclear plants do not retaill the expertise ollsite for allY thing more than routine sampling and maintenance. Operators need to ensure dIat contractors, required tor more extensive maintenmlCe and testing, understand the qusHty control and procedural practices required for nuclear plallt operatiolls. Republic of Korea and the United States noted that licensees \\v110 mn multiple reactor sites may maintain a central group responsible for transfOlmer maintenance.

facilitating the shming of operating experience betweell multiple sites mId helping to ensure an undel~standing of plant practices. The Republic of Korea also reported a strong degree of oll-site staff training and involvement in transformer maintenance, w'hich appears to be a good practice in light of the noted indllstry gnidmlCe.

Indmtry operating experience bas identified cOlltinuous online gas analysis as the best method for identifying all impending failme of a large oil-flUed transfonner. Advantages of online analysis include measmements of gss content in the oil that are less susceptible to sampling elTOrs, mId which allO\\'l for timely recognition of deteIiorating conditions. However it is recognized that the cost-benefit analysis of back-f1tting u'snsfonners already in plsce may not justifY the expense. Benefits may be gailled frOlll identifying degradillg trends in key parameters dIat lllay indicate degraded insulation conditions. This degrading trelld could justify dIe lllstaUation of contilluous mOllitoring equipment in order to identify w'hen the transtonner should be taken out of service for repair or replacement before a catastrophic failme occurs. At the Peach Bottom plant in the U.S.. regular oil smnples noted higher than normal gas levels. prompting the licensee to instsll an on-line gas analyzer.

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\\vllen the on-line analyzer detected gas levels above a pre-set limit, the plant shut dO'Y<1l and replaced the tnmsfonner before it actually failed. In any case. any new large. oil-tilled transfonners that are installed should be equipped \\\\,1th continuous gas analysis capability.

Although all nuclear plants have staff trained in tire response identified on every shift, most plants do not maintain dedicated frre11ghting staff capable of combating a large fire.

1,1ost fire respome crews consist of licensee personnel \\'/110 have received training on basic fireiighting techniques. Procedural response tbr large fires usually involves coordination with otIsite firet1ghting organisations. As trausfol1ner tIres present additional hazards, some plants have instituted specific training for dealing 'with the challenges presented by a large transfonner fire, In Japan, lessolls leamt trom a transfonner fire at Kashiwazaki-Kariwa 3 resulting from the earthquake ill 2007 (IRS 7922)

'were applied to fire respollse tmilling programmes aroulld the COUllttY. In Spain. the Garolla Nuclear Power Plant ulCol1)Orates specitle tJanstbmler fhe scenarios UltO fu'e response traming. Canada and the Netherlallds used operatillg expelience fi"om the Kmemmel fire in 2007 (IRS 8049) to inform their response to tramfonner fires. Republic of Korea ensmes regular panicipation of offsite fire stations in plant fire drills to enhance communication and cooperation.

18 OAGI0001166_00018

1'.:'EA/Cl';"'RAtRi{ 2011)6

5. RESPONSE OF OECD-~"'EA COUNTRIES TO TRANSFOR\\IER FAILURE QUESTIONS TIle following section provides the summary response of each OECD-NEA COlll1try that replied to the questions posed by the U. S. NRC about main tranSfOl1l1er failures.

5.1 Belgium TIlere are no regulatory requirements which govern the maintenance of trrulsfonners and no repm1ing requirements that apply directly to tnmsfonuer failure. The regulator does not monitor any parameters to detect degraded conditions in transfonners. This is the responsibility of the licensee.

Licensees have implemented preventstive snd predictive maintenance progrmnmes based upon manufacturer msintenmlCe guidelines. internal and extemal opemting experience. Online monitoring of transfonner key fault gasses provides an early waming of fault conditions that could lead to transformer fsilure.

Oil temperature mId level are monitored by the licensee.

Additionally, thenllOgraphy, dissolved gas analysis. air cooling system chech and inspectiollS for oil leaks are performed. ~'ilaintenance and testing frequency is influenced by the results of previous testing, as \\vell as by enviromnental and operational consideratiOlIs.

TrmLsformer maintenmlCe is typically conducted by site maintenance personnel who have received appropliate training on trallSfOnllers. Onsite staff verify transformer maintenance pertt/nned by contractors.

An offsite maintenance competence center. \\\\'ith extensive training provided by the equipment manufacturer, is available to shsJe operating experience about the tmnsfonner fleet.

Operators perf0l1ll daily maintenance rounds and \\veekly inspections of critical parmneters.

The spare transfonner~ have their O\\",n maintenance rounds. Adequate procedures are in place if an abnonnal condition is detected.

In the event of fire, dIe control room operators \\",ill follow tlle instmciions provided by the flIe hrigade oUker. Fire brigade officers have been tmined on the electrical dangers on site.

5.2 Canada Though there are no regulatOly requil'ements specifically governing Large Oil-Filled (LOF)

Transfonners, tllere are regulations which apply to maintenance programmes in general. These require the licensee to consider vendor recommendations. industry codes and standards, design and operating conditions, operating experience, and aging mallagement requirements in tlleir maintenance programmes. More genemlly, licensees are required to ensure that maintenance on equipment is pedonned regularly. and to industry standards, Systems important to the nudem power plsnt are required to function reliably. Though transfonners are not considered safety significant, alld so in and of itself a failure is not repOItable to the regulator. their faihrre is usually accompanied by a nuclear plant transient. which is reportable.

This potential for impsct on the reactor raises the level of regulatory interest in LOF transformers.

despite tlleir non-safety statns.

19 OAGI0001166_00019

1'.:'EAiCNRA/R/(20 11)6 As 'with other nuclear and non-nuclear plant parameter~. the function of the regulator and tile inspection stat1' is not to monitor specitk indications or detect degraded conditions, but rather to verity that the licensee monitoring programme is sufficient. and that licensee response to abnormal indications is in accordance with designated procedures.

Licensee maintemlllce and monitoring programmes track oil properties. particularly gas concentrations in the oil indicative of insulation breakdovm and 31'Cing events. as well as oil and w'inding temperatures, oil level, pump pressure, insulation deterioration, mId possible leaks.

Mouitoring frequencies are based on establislled industry recommendations, ranging from continnous monitoring of vital temperatures and pressures (and in some case continuous gas analysis) to infrared thennography checks, Doble testing. and complete overhauls every fe\\¥ years.

1iaintenance frequency is determined by a combination of industry guidance, risk impOltance, operating experience. duty cycles and environmental factors.

In general, pl31lt persOlUlel are sufficiently familiar witll transformer operation to recognize abnormal circumstances. but maintenance is performed by contractors under oversight of specified licensee engineers. Training is provided to operators to diagnose abnonnal conditions and take appropriate actions to stabilize tIle plant if necesssry Specific training for combating transformer fires is provided to the tire bligade, wllile control room operator~ and non-licensed operatOl~~ receive general training for plant tIres and fn'e safe shutdown procedures.

5.3 Czecb Republic As tmnsfollners are not classified as safety related equipment. tlley are not specifically covered by regulatOlY requirements-Likewise, reportability requirements do not address transformer failures, however the tmnsients resulting 110m tJanst011l1er fsilures are covered by the stmldard events repmting scheme. Additionally, as the regulator receives alllice!l<;ee event repOlts, including reports oftransfo11l1er failures, specific rep011abiliry requirements regarding large transformer failures are not necess31y. Resident inspectors pertl..lnn an inspection sample of general transfonner parameters to verity that they moe within spedficstion. however the smnp1e size is sUlsll, and monitoring of parameters is primarily the responsibility of the licensee.

Licensees monitOling consists of continuous gas in oil analysis to keep track of the status of the insulation and dielechic propelties. Equipment required for continuing operation. including pumps, fans, and dryers are also monitored. The preventive maintenance schedule accounts tl..lr the age of tile components, risk importance, duty cycle, and environmental conditions. with augmented inspection requirements in the event of abnonual results or trends.

Opemtop; receive periodic training on actions to be taken in accordance with abnormal operating procedures in the event of a tramtl..lnner malfunction. Operators 31-e trained to recognize abnol1llal indications, however actual maintenance of the transformers. both preventive and reactive, is pertol1l1ed by outside contractors. Contractors are expected to ensure tile qnality of dleir own \\vorlc, which is also overseen by station system engineers. Licensee quality assurance inspectors also review contractor work on a sample basis to emnre it meets station standards. Station per~onneL including the tire brigade. are trained to respond to tIres, and abnOl1l1al conditions resulting from a tramtl..lnner fire are covered in operating procedures.

5.4 Finland As large transtonners sre classified as non-nuclear. in the lowest safety class, there are no specific regulatory requirements regarding transfonner maintenance programmes, nor are there specific repOltability reqnirements for transfonner failmes. The l-egnlator oversees licell';ee implementation of all nlliintenance pro gralmnes, induding those for large transfonners, particularly 20 OAGI0001166_00020

1'.:'EA/Cl';"'RAtRi{ 2011)6 during annual maintenance outages. The licensee is respomible for regular monitoring oftranst"i../nner parameters and conditions, and the regulator perfonns a regular assessment of the licensee programmes. RepOlts including transfbnner failures are made to the regulator in the event that the failure results in a plant transiellt or disturbance.

Operators are provided with control mom readouts of key transfonner parameters and results of online hydrogen gas-in-oil analysis.

Thellnal alld optical seusors alld oil level alann<; al'e also provided. In an dfOIt to eliminate single point of failure trips, redundmlt main transfonner protective relays are provided. The preventive maintenance programme schedules inspections, surveillallCes, and compollent replacemellts at intervals rallging from mOllthly to decennial based Oll operating experience, inspection results, and component conditions. The transfonner lifetime management programme accounts for years of service, risk imponance, duty cycles, alld transients to provide feedback to the preventive maintenance programme fbr maintenance scheduling. In the event of a degraded condition, the maintenallCe and surveillallce schedule is advanced to ensure timely assessment oftransfonner operability.

Operatop; al'e trained Oll procedures for mOllitOling and operating the plant in the event of an abnomlal condition with the transfonner, including grid disturbances and tran.sformer flres. Vv'hile onsite persollnel are suftkielltly knowledgeable to recognize abnonual conditions and evaluate operability, maintenance is generally contracted to outside orgallisations. Contract luaintellance is overseen by the plant electrical nlaintenance manager. and contracted maintenance procedures are expected to meet the basic expectations of licellsee maintenallce procedures. Licensed and non-licensed operators, as \\;vell as the tlre brigade, receive training 011 transformer !lre response, induding the wide-ranging and potelltially unpredictable plant responses that could result.

5.5 Germany Transfonner events are not reportable unless they affect the emergency pm,ver disttibution system or other safety related systems.

Online gas monitoring is lIsed to detect the breakdown of oil used to cool the transformer, which can be indicative of potential problems, but even \\'/ith continnom mOllitOling, tllis breakdovm may not be discovered lmtil it is too late. Utilities collect and amlyse samples regularly to detenmne the conditioll of the oil, as well as its water and gas content. Protective relays \\'/hich can sense step challges in pressure or temperature and trip tlle tt*allsfonner omine are used to protect equipment and personnel in the event that testing fails to detect a problem before s failure OCCllIS, 5.6 Japan Transfonners are not nuclear safety equipment, and so are not covered by regulations, The regulator does not monitor any transfonner parameters, and failures are not reportable except as they may be incidentally related to a reactor trip.

Licensees act upon a life management programme based Oll time-based maintetlallCe every six years and fhll assessments every tw*elve years. At t"venty-tbur years, a prediction of remaining life is made and the maintenance schedule adjusted accordingly. Implementation of condition based maintenance is based on regular mOllitoring and tretlding of imp0l1ant parameters, inc1udillg gas conceutt*stion and temperatures. (See Appendix: Japanese Typical Recommended Transformer Maintenance Program)

Transfonner maintenance is cfluied out by contractors, overseen by tlle utilities, bnt is not included in regular or abnormal procedures. Abnonml procedures contain response requirements for 21 OAGI0001166_00021

1'.:'EAiCNRA/R/(20 11)6 transients resulting from trausformer incidellts, but do not address transfonner maintenallce, Training on intrequellt activities relatillg to tranSfOl1l1erS is llot illduded in the regular training cycle, hmvever operators and contract employees are considered to be sufficiently expelienced to handle situations as they arise, Fire fighting response to transtOl1l1er fires is emphasized in trainillg progranlllles, lllC0l1)orating lessons-leamt follo\\;ving an earlier transfmmer fire.

5.7 Netherlands

}.*1ain tmllSformers are not classified as nuclear safety equipment; therefore they are not covered by regulations and are llot monitored by the regulatory body Though there are no repOlting requirements specifically addressing transformer failures, there ale requirements tbr grid disturbances, reactor transients, alld fire damage, any of which might result trom a transtOl1l1er failure.

Licensee maintenance programmes involve annual oil sampling. analysis, and trending. testing of protective relays, and regular inspection and replacement of importallt compollents. Maintenance is generally performed by contractors, however plant personnel receive specific training on transfonner operation snd maultenance to ensure proper supelvision of contracted activities.

Abllonnal operating procedures fOCllS on response to reactor plant transients and grid disturballces that may affect (or be afiected by) transformer anomalies.

Specit1c rrauung on response to transtonner tIres has been implemented as a response to the Kmemmel tmnsfonner fire u12007.

Regulatiom; do not specifically target the reportillg of transfbnner fsilures. However, failures that aiIect systems covered by the regulations 'Nould be reported. Transformer maintenance is covered by regulations 11l1der requirements for basic maintenance and operations for specified items.

Twice a shift operators petform roullds to verify the proper operation of trallsfol1ner functions and check that levels, temperatures, and voltage readings are witillil specified ranges. Twice a year, the operator pertOl11lS an oil sample allalysis to check color. gas and water content. and dIe extent of oil degradation. A full preventive maintenance workup is performed during each planned outage, or about evety two years" These maultenallce activities are peliol111ed by amite personnel under agreements \\vitll the grid operator. bnt are verified by dIe plallt operator as meeting the requirements of the llliclear regulator.

Abnonnal operating procedures describe operational linuts tor the transfonners and con-ective actions to be taken in case of abnomlal indications, indudulg shifting the plant to operate in island mode. This a11o\\\\'s plant systems to be fed from standby lilles or EDGs. Training is provided to operators on the use of nonnal and abnormal operating procedures. and on s regulsr basis to all plsnt persollneL including the fire bligade, for emergellcy preparedness and scenarios involving transfonner failures.

5.9 Republic of Korea (South Korea)

Oil filled trallst0l111erS are identified in regulations as equipment subject to petiodic inspection by regulatory inspectors. Inspectors conflnu ulsulation resistsllce checks snd protective device tests. and exanune the condition oftap changet'S along \\\\'ith the exterior of the transfonnet*. If abnormal degradation is idelltified durUlg the illspectioll, recommendations or findings may be issued by the regulatory body. There Sle no regulatory requirements directly related to repolting of tramt\\..lnner failures" However, if all event is caused as a result of transformer failure. the liCetlSee repOlts that event to the regulator.

22 OAGI0001166_00022

1'.:'EA/Cl';"'RAtRi{ 2011)6 Both predictive alld preventative maintenance is petformed Oll large oil tilled tmnsfol1ners.

Preventative maintenance has induded replacement of all transfomlers more tIlllil 23 years old, and replacement of protective relays on a 5-year cycle. The moistme levels and gas concentration in the insulating oil are analysed every t\\VO hours to detect degraded conditions. Thennography and plli1ial discharge tests OC('11f each spring. Operators monitor the temperanu'e of the tIansfOlmer during

'walkdowns 1-3 times a shift. A pcr10dic inspection is perfol1ned by mailltenance persollnel once a month and transfonner engineers \\;valk down the equipment to detel111ine system imegrity on a quarterly basis. Automatic respoIl<;es, emergency actions llild conective measnres required due to tmnsfonner failure have been cleady desCI1bed in system operating, alarm response, and abnonual operating procedures.

Detailed inspections of the inside of the transformer are periodically perfolmed by vendors.

Maintenance work conducted by contractors is perfomled according to approved procedures and is supervised by the site maintenance and engineeJ.1ng divisions. Site statf is knowledgeable and proficient at maintaining large tnmstolmers. Trainulg is performed on llil llilllUal basis and includes theory. maintenallCe and operating experience. Workshops are held to highlight relevant evellts and share experience in the operation and nmintenllilCe of these transfonners. Both the onsite fire brigade and the offsite fire stationllave beell trained t\\..lr onsite fire accidents, including transfonner flres.

5.10 Spain Transfolmer nmintenllilCe is not specitkaUy mentioned in regulations. and events me not repOItable except as they result ill reactor transiellts. Licensees petform regular monitoring of components important to normal tTansfolmer operation. Some licensees have installed continllous gas analyzers to provide timely notice of impending failure: other licensees perform in-depth physical and chemical analysis of oil samples Oll a scrui-allllUal basis. The preventive maintenance schedule \\vas established based on industry and vendor guidelines. and though the basic maintenance schedule is not adjusted based on duty cycle. envirornnental cOllditiom or transients, additional mainte1lance will be pertbl111ed in response to observation of deteriorating tIends.

Basic maintenance is pcrionned by licensee personnel. however most maintenance is pertbnned by contTadors under the supervision of licensee personnel.

Procedures detail the appropriate responses for alanning conditions and potcruial trallsients. The fire bligade receives specific trainillg regarding transformer tlres, while licensed alld non-lice1lsed operators receive training on general fire-tlghting scenarios. While not specifically tOcused on transformer thes, this training has included drills involving transfonner fires.

5.11 Switzerland RegulatOly requirements addressing quality assurance and maintelmnce programmes are applicable to the associated programmes for large transtOl1l1ers. These regulations also require rep0l1ing of any failures that lead to an unplanned power reduction or cause damage to safety-dassitled components. Events caused by lightning strikes are also reponable to the regulatOIY body.

In addition. monthly llild quarterly reports on maimenance and testing, including that perfonned 011 large transtbnners, are required. as are safety assessments performed every ten years. which include an evaluation of the condition of equipment.

Monit0I1ng of transfonuer parameters is the responsibility of the plant. though the etfectiveness of nmintenllilCe fmd monitoring programmes is subject to illspectioll by the regulator.

23 OAGI0001166_00023

1'.:'EAiCNRA/R/(20 11)6 Tramfonner operating conditions and readings are monitored as part of routine shift rmUlds.

The short-tenn and 101lg-tenn maintenance schedules are int1uenced by allY nonnal alanm; received, results of regl.llm* monitorin~ and any conditions noted during regular maintenance. All main transfonners have been replaced since Oliginal installation as P31t of power upgrades tlIat made more efficient use of the heat available tl"om the reactor plant rather than because of degraded conditions noted on the trmlsformers themselves. I-,*1aintenance is usually per!olmed either by plant pers0l11lel or by quslitied employees of the psrem c0l1)oration, with oversight from plsnt personnel.

5.12 United States Though there is no regulation specifically addressing main transformer~. there are regulations requiring the licensee to mOllitor the perfonnance and condition of equipment to emure it is capable of fulfilling its intended tllllctlons. Quality assurance requirements also may apply to valious aspects of transfollner maintenance. Tmmfonner failures are not reportable ill and of themselves, hmvever any transtonner event that results in a reactor trip or a fire requiting an emergency declaration is required to be reported. l'vfonitOllng of tnmsformer operation and performance is the responsibility of the licensee. The regulator evaluates tlIe effectiveness of the licensee maintewmce programme.

Licemees monitor impOltant psrameters on a contllmOlls basis. The latest illdustry recommendations include installation of contiImous dissolved gas analyzers, however not all licensees have completed this upgrade. Preventive maintenance schedules use industry and vendor recommendations, operating experiellce. trend results, and component age to detennine inspection and maintenance fiequencies. Indication.s of degradation generally result in increased monitoring and evaluation. Industry guidsllCe recommends abnonual operating procedures addressing any slanning or abnomlal condition.

Licensees are expected to have the knowledge and experience avsilable for most TOutllle transformer lllaintenmlCe, Any work that is performed by contraciors or off-site organisations should be perfonned under the oversight of licensee personllel fsmiliar with the equipment and the work to be per!omled, Contractors are expected to have procedures and qualitkations w'hich meet the requirements of site procedures and qualitkatiOlK Industry guidance also recommencls that licensees velify cOlltractor work at multiple stages of a project, lllCluding mmmfactme, to ellsme the qus1ity of the work Trainillg on transformer fires is expected to be provided to the tire brigade and to licensed and non-licensed operators. Fire fighting procedmes should include consideration not just of the fire, but of potential hazards involved in a trsllSfonner fire, and of operatiollS independent of the grid.

24 OAGI0001166_00024

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(J1 APPENDIX: JAPANESE TYPICAL RECOMMENDED TRANSFORMER MAI~IENANCE PROGRAM t*j

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l\\lAINBOOV Ci}tl/lnsulatlon paper Ci:wEl. Insulation on Internal structure lank Agingfactllrs

- Thermal F::I{'tor (Normal, Excess load~ over l'urrcnt, etc.)

- Electrical Factor (Surge yoltage. Alternate Over Volhlge.etc.)

-Mechanical Factor (Extcnull <lcddenhll ovcr l'urrcnt~ etc.)

- Environmental Factor (Rain, Thunder, sunshine,corrosive gas~ etc.)

Life Mm"'f;<ment

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"~12yUrs ;,.

LIfe Manat;e",,,,,,t A&s....."ent (II }

"'~',il4l"'"""""

Lifetime

- Surge Current External Accident Current

.* ~. :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::?j nnnjjn!!!m;i~". :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::,

TBl\\J: Time Based Maintenance C B:l\\,.1: Condi bon Based l\\laintenance Fig-l Japanese Typical Recommended Transformer Maintenance Program Tm.i

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(Every6yUr$ )

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Life Management Evaluation (1)

- Analysis results of clissolved g'us in oil

- Degradation of the gasket

- COl~rosion of t.he eooier (Heat exchanger)

  • Degradation of oil feed pump and fali bearings
  • Performance ofth(; in~mlation oil

- Degradation of instrumentations Life Management Evaluation (n)

- Residual hfe evaluation of in suiation papers

- Purchasing of t.he spare part.s quitted t.o produce U;J'C)

  • Compliance to the latest codes and standards (Sea breeze, structmal integrity of the tanks)

In case of Service Life Extension:

Preparing.Life E,:\\J*ension Progmm e.g. to decrease oil temperahrre

<Referenced standard and g'uid;;Il:1C:(;>

  • The,Japan Eledrical l\\lan ufact.urers' Association:

"Proposed replacement time of oil c(xlled traustbrmer accessories (spare parts)"

(;J EIVFrnW7)

  • Electrical.Joint Resem:ch Report "Maint(;ru:tnc(; l'vfanagement of Oil cooled Transfonners" z

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