ML12334A480

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Official Exhibit - NYS000021-00-BD01 - Oecd, Nuclear Energy Agency, Operating Experience Report: Recent Failures of Large Oil-Filled Transformers, NEA/CNRA/R(2001)6 (Mar. 14, 2011) (Nea Report)
ML12334A480
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: ML12334A480 (26)
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Text

United States Nuclear Regulatory Commission Official Hearing Exhibit Entergy Nuclear Operations, Inc.

In the Matter of:

(Indian Point Nuclear Generating Units 2 and 3) NYS000021 c.\,..t.p.~ REGU~)o ASLBP #: 07-858-03-LR-BD01 Submitted: December 12, 2011

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Docket #: 05000247 l 05000286

~ 0 Exhibit #: NYS000021-00-BD01 Identified: 10/15/2012

~ ~

'" ~ Admitted: 10/15/2012 Withdrawn:

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'1"'/1-

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0' Rejected: Stricken:

      • .... Other:

F nc1assified NEA/Cl';'RAIR(2011)6 I- -,

OrgmllsatlO11 de C OOperflllOrl et de Developpement E.conomiqn.::s

((. Organisation for Economic Co-operation and Development 14-MHr-2011 Englisb text only

~TCLEAR ENERGY AGENCY COi'VIM1TTEE ON Nt':CLEARREGlTLATORY ACTTVITIES CanceL~ & replace~ tile same document of 11 ~.fal'~h 2011 Opel'atingExped"IH."" R('llOl't:

Recent F:dlul"es of Lltl'ge Oil-Filled T I"lmsforlllel'S Working Group on OperatiIlg Experience (\NGOE)

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'~ JT03298131 (t.

Do<um.nl camplet di,ponible .m' OLIS dans ron founa! d' origine

"~ Complet~ document "vailable on OLIS in its "dginal forma!

OAGI0001166_00001

1\i'EA!CNRA/R/(20 11)6 ORGA~lSATION FOR ECONOl\UC CO-OPERI\TION A..l"'\"D DEVELOP:\lENT TIle OECD is a lUlique forum where the govemments of34 democracies work together to address the economic. soci3l 3nd environmental challenges of globallsation. The OECD is aho at the forefront of efforts to IlnderstmICl Bnd to help governmenis re~pond to new developm;;:nts and conc,enn, such as cOlporak governance, the information economy and the chalknges of an ageing population. TIle Org,misation provides a "eHing where go,emmenh can compare policy experiences, seek lH1,WerS to common problem" identify good practice and work to co-ordinate domestic and international policies.

The OECD member countries are: Au.'itIalia" ft.usiria, Bdgillm. Canada, Chile, the Czech R;;:public, Denmark Estonia, Fini<lnd, France. Ot:l1nany, Greece, Hungary, Iceland. Ireland. Israel, Italy, Japan" Korea, Luxemhourg. Niexico. the

~etherbnds, New Zealand, Norway. PoiBnd, Portugal, the Slovak Republic. Slovenia. Spain, Sweden, Switzerland, Turkey.

the United Kingdom and the United State5.TIle EUl'Opean COlilllllssion takes part in the work of the OECD, OECD Publishing disselninates widely the results of the Organisation'5 5tatistics gathering and research on econollllc.

social and environmental ic;sues, a~ w.::li 3.0 the conventions, guidelines and standal"d~ agreed hy it, memhers.

This work is J7IIbiished on the ITsponsibilit;, of the Secmtary-General of the OECD, The opinions expressed and arguments I>fllployed herein do not necessarily re;f/ect the official views of [!"Ie Organismion or '<Itlll> govenmwnts c:f its member cOlin tries.

NUCLEAR ENERGY AGENCY The OECD Nudear Energy Agency (NEA) was e"tablislled on 1;:1 F;;:bmary 1958 tmder the name of the OEEC European Nudear Energy Agency It received iis prei>erlf designation on 2ot~ April 1972, when Japan became its first nOll-European nlll membero 'N'EA memlJep;hip today cOllsists of 29 OEeD member cOlUltrie,: Austl*alia. Austria. Belgium, CBnada, the Czech Republic, Denmark Finland. France, German}~ Greece, Hungal)'. lceiBnd, Ireland. ItBly, Japan. Ke<reae Lu."embomg. Mexico. the Netherlands, NorwaJ~ Poland, POltugal, the Slovak Repllblic, Spain, Sweden. Switzerland, TurkeJ~ the United Kingdom and the United States. The European Cmnnllssio!l aho takes part in the work of the Agency.

The nllssion of the NEA is:

  • to as,!st its member countries in maintaining and nll-ther developing, thmugh intel1mtional co-operation, the sciemiiic. technological and legal bases required for a safe. environment311y friendly and econmrucal me of nuclear energy tor IJe3ceful plUposes. as wen as
  • fo pmvide ,mihoritative as,;;:ssrnents and to forge cDnmIDnllnderstandings on key is,ues, as input to government decisio115 on nuclear energy policy and to broader DEeD policy analyses in an,a, S11Ch 3S energy and snst3llahle deYdopmem.

Specific areas of competence of the NEA include safety and regulation of mlclear 3ctivities, mdioactive waste management. radiological protection, nuclear science, ecmlOlllic and technical analyses of the nuclear filel cycle, nuclear law and liahility, and public intormatioll.

The NEA Data Bank provid;;:s nuclear data and cDmputer progralll <;elvice" tor participating coulltIies. In these and related tasks. the ~~A works in cime collahoration with th;;: Intemational Atomic Energy Agency in v'lenna, with which it has a Co-oper3tic<Il Agreement, as well as \'lith otller intematimilll orgBm,atioll'> in the mlclear fieldo Corrigenda to OEeD publications may be fcnmd online at: """<:oecdorgipublisil,,,W'conig<?nda, t:, OEeD 21111 You "all cupy, download {)f print GECD content fOf your "">> use, and y.,u can mdude excerpts from GECD J,'tIDlications, dalah"ses and multimedia product. in ymu' {)\~11 docwnent., pre""ntaliOll~o blocgs, wehsite, aud teaching maleriaB, p1m~iIed that ,,,itable acknowledgment of OEeD a~ smu'ce and C<Jfryl-iglrt o"'"Iler i. given, All ,-rque;.ts for public or C{)mmefcial u.e and =~latiOll fight~ ,hmild \x, submirte,,{ I.,

righ{s@=dorg. Reque;,ts fur pemris>;on to photoc<JPY p<.'ttions offllis Illil.le:t-inl f{)r public or commercial u,", ,hall be addressed ifu-ectly to the

.C:op)l~%ht C:lemoUliceCelIte1: (CC;C). at i'lf0(g:coPy"ght.cof" Oflhr C;""Ur ff""~ai~ d'exploitatl0n dUdr{)1tdr copte (C"C) COfJt"ci(ij;cjcopi<".oCOf".

OAGI0001166_00002

COM:\UTTEE ON l\'lTCLEAR REGVLATORY ACTIVITIES The Committee on Nuclesr Regulatory Activities (CN~A) shsll be responsible for the programme of the Agency conceming the regulation, licensing and inspection of nuclear installations with regard to safety. The Committee shall constitnte a tbnun for the eftective exchange of satety-relevant infbmmtion and experience smong regulatory orgmlisations. To the extent appropriate, the Committee shall revie\'l developments \vhich could aftect regulatory requirements with dIe objective of providing members with an understanding of the motivation for new regulatory requirements tmder consideration and an opportunity to ofter suggestions that might improve them and assist in tIle development of a common understandi.ng among member counnies. In p31ticular it shall review OUTent nmnagement strategies and safety management practices and operating experiences at nuclear facilities \'lith a ,*iew to disseminating lessons learnt.. In accontance with the l'Ii'EA Strategic Plan for 2011-2016 and the Joint CSNI/CNRA Strategic Plan and Ivlalldates for 2011-2016, the Committee shall promote co-operation among member countries to use the feedback it-om experience to develop measures to ensure high standards of safety, to fiuther enh31lCe efficiency and effectiveness in dIe regulatory process and to maintain adequate iniiastructure and competence in the nuclear safety field.

The COlmmttee shall promote transpm'ency of nuclem' safety work mId open public COllllll1mication. The Conllnittee shall maintain an oversight of all NEA work that may impinge on the development of effective and efficient regulation.

The Connruttee shall focus primarily on the regulatory aspects of existing power reactors, other nuclear installations and the constmction of ne,\' power reactors: it may also consider the regulatory implications of ne\;I,i designs of power reactors and other types of nuclear instsllatiOlls.

Fm1hennore it shall examine any other matters refelTed to it by the Steering Committee. The Conl1mttee shall collaborate with. and assist as appropriate, other international organisations for co-operation among regulatOl~<; and consideI~ 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 mechanisms with the Committee on the Safety of Nuc1eaT Installations in order to work \;l,iidl that Committee on matters of COIllmon interest. avoiding unnecessary duplications. The Committee shall also co-operate w*ith the COlll1mttee on Radiation Protection and Public Health and the Radioactive \Vaste Management Committee on matters ofcommon interest.

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1\i'EA!CNRA/R/(20 11)6 4

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The 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 industty's and regulatory body's etIbrts 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, \;vhich \vas later renamed the \Vorking Group on Operating Experience (WGOE). In 1978, tbe CSNI approved the establishment of a system to collect intemational operating experience data. The accident at TIuee I-,*1ile Island sbortly after added impetus to this and led to the stm1 of the 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 the member countries of both organisations. In 2006. the \VGOE was moved to be under the umbrella of the Connnittee on Nuclear Regulatory Activities (CN""RA) in NEA. In 2009. the scope of the Incident RepOlting System w'as expanded and re-named the International Reporting System for Operating Experience (although, the acronym remains the same).

The pllI})OSe of WGOE is to facilitate the excbSllge of infonnation, experience, SlId lessom leamt related to operating expelience betw'een member cmmtries. 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 gronps.

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1\i'EA!CNRA/R/(20 11)6 6

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TABLE OF CO~-rEj',TS Foreword ...................... ..... .......... ..... .......... ............ ............ ...... ................. ................. .......... 5

1. Background. . .. . .. ... . . .. .. .. ... . .. .... .. .. . .. ... .. . .. .. .... . ... . . .... . . .. . .. ... . . .. .. .. ... . .. .. . . ... .. .. ..... . ..... ............. 9
2. Failmes ofUJJge, Oil-Filled TransfOlmers and Risk Significance ..................... ................. ............... 11
3. Questiomlaire Issued to Member States ....... ............ ................. ............ . ............... ............... 13 3.1 Questions forthe Regulatory Body........... ..... ................ .................................................... 13 3.2 Questions for the Operating Organisation ....... .......... ....... .......... ............ ..... ...... ............... 13
4. Analysis and Conclusions .... ..... .. ...................................... .......... .......................... .......... 15 4.1 COlUltty Inputs .................. ...................... ................ .............. ........................ .......... 15 4.2 Recent Events ............................. ....... ....... ..... .......... ..... ..... ..... ............ ......... ........ 15 4.3 Summary of Countries' Responses ...... ............... ............... .............................................. 16 4.4 Commendable Practices .............................................................. ....................... ........ 17
5. Response of OECD-}':'EA Countries to Transformer Failure Questions ............................................. 19 5.1 Be1gillll1.. . .. . . . ... . . . ... . . . . . . . . .. . .. .... ..... .... ............................... ........... . ... .................... ........... 19 5.2 Canada ............... ..... ..... ... ......... ............ ..... .......... ... .. ..... ..... ......... ..... .... ................ 19 5.3 Czech Republic ............ .. ................ .......... ..... ....... .. .... ....... ... ........... ......... ................ 20 5.4 Filllallcl .... , ..... ,..... ~ .... ,..... ,..... ..... ,..... ".... .......... ... , ..,., .. ,..... ~ .... ,..... ,..... .,..... ...... "., ........... ".. .,..20 5.5 GelTIlany....... ..... ..... ..... .......... ................... .......... ..... ..... ..... ... ........................ ........ 21 5.6 Japan ....... .. .... ............... ......................... .......... ................................................ ........... 21 5.7 Netherlands ..... .................................................... .. ...................... ..... ............... ........... 22 5.8 Slovakia ................................. ..... ..... ............ ................. .......... ..... ....... .. ............... 22 5.9 Republic of Korea (SoutllIZorea) .............. ............................... .......................................... 22 5.10 Spain ............. ..... ..... ..... .......... ....... ....... ..... .......... ..... ..... ................. .............. ........ 23 5.11 S1;vitzerland ....... .. ............. ... ......... ..... ....... .. .... .. ..... .... ............... ......... . ..................... 23 5.12 United States .................................. .. ... .. ................................... .. ................ .... .......... 24 Appendix: Japanese Typical Recommended Transformer ~'ilaintenance Program ...... ................. ............... 25 OAGI0001166_00007

1\i'EA!CNRA/R/(20 11)6 8

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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 pertonned by WGOE recommendations are provided to the CNRA. on regulatory issues and the Committee on the Safety of Nuclear Installations (CSl';T) on tedmical 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 had identified that transfonner failures had an increasing trend.

Transformers are non-safety related equipment. As such . the maintemmce practices are generally outside of the regulatory purview. The US NRC developed a Sh011 questionnaire to discuss the regulatory treatment of transfOlmers and the operating experience in the member countries. At the conclusioll of the discussioll. tIle members decided that sufficient infonnation and interest was available to support a task on large oil-rllled transfonners.

In December 2009, the \VGOE was granted C"N""Rl\. approval for a task on transtonner failures.

The United States and Canada volunteered to SUpp01t the task. A more detailed questionnaire was developed for the member countJies to contribute their operating experience on transformer failures.

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1\i'EA!CNRA/R/(20 11)6 10 OAGI0001166_00010

2. FAILURES 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 behveen the nudear power plant and the electtic gIid. \\-'ith the main generator transfonner providing output to the gIid and lmit and station amdliary tmnsfbmlers providing offsite pow'er to the plant. Rated at tens or lumdreds of thousands of megavolt-ampere (1vfVA) these high energy systems are otten maintained by outside cOIlU'aC tors. and i.nvolve multiple suppotting components. induding cooling systems. surge atTestors, bushings/insulators, and control systems, all of which must be properly maintained in order to provide for the safe operation of the tramfonner.

2.2 Risk Significance

\Vith the exception of some atn;:iliary trallsfbrmers which fimction as part of the omite electrical distribution systems, large. oil-filled transformers are generally considered to be non-safety related equipment. Their primary illllction is continued power production. and they are not relied upon tor the safe shutdO\\'ll of tIle reactor. As such, failures of large transformers generally are not, in and of themselves. required to be repotted. 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 dIe reactor in a safe, shutdo""'!l condition.

2.3 Broader Implications for Safety-Related ;\lainteu3nce Programmes Indllsuy 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 countries dillt require plant maintenance progI'an11nes in general to meet acceptable standards. Successful maintellallCe progI1Ulunes 'will not only determine that testing results are within speciflcation, 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 breakdo\~lll of the oil caused by hot spots and faults in the u'ansfonner,can provide an indi.cation of the overall healdl of the u'ansformeI:

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3. QUESTIONNAIRE ISSI1ED TO MEl\ffiER STATES 3.1 Questions for the Regulatory Body
  • ATe there regulatOlY requirements for the maintenance of large transfOlmers? If so, what are they?
  • A..re tilere regulatory requirements for repOlting transformer failures? If so, \\'hat are they?
  • \'<llat parameters does your regulatory body monitor. trend. and analyse tor large transtonners to detect degraded conditions?

3.2 Questions for the Operating Organisation

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

- Are single-poim failure \'lllnembilities, potential sources of spurious transfOlmer hips that can cause an improper acmation of a single relay or component considered?

  • Does the operator have a predictive and preventive maintenance programme tor large tmnsfonners? Describe the tlmnework oftlle progmnune.

- Does it include . tnmsformer years of service, risk impOltance, duty cycle. transient cycles, and envlIOlUnental conditions?

- Does the operator have a contingency plall for transformer inspections if a signit1cant degraded condition exists?

- Does tIle operator conduct detailed maintenance rounds on major station transfonners and spaTe transt011l1ers? Do seasonal and opemting conditioIt'; affect the depth of the maintenance rounds?

  • Does the operator have suffkiently detailed operating and abnormal procedures related to tmnsfonner activities?
  • Does the operator have clear job responsibilities tor transformer operation. maintenance, and perfbmlance monitoring?
  • \VI1O verifies transfbnner maintenance activities by contractors or omite organisations?
  • Training and knowledge:

- Is appropliate training included with infi:equent transt011l1er activities?

- Are onsite personnel knowledgeable and proficient at maintaining dIe large transtonner?

- Does the operator provide trauling fbI' the station 11re hrigade. non-licensed operators. and the contn,l. room operators on transtbnner fire response? This training may consider dIe possible isolation ofthe lInit from the grid. as \;veil as isolation of the site it-om the grid, 13 OAGI0001166_00013

1\i'EA!CNRA/R/(20 11)6 14 OAGI0001166_00014

4. Ai'lALYSIS Al'I'D CONCLUSIONS 4.1 Country Inputs TItis report documents inputs received tl'om t\velve cOlll1tries regaJding maintenance and regulations associated with oil filled transfonners. These respoIl';es came from:
  • Belgium
  • Canada
  • Czech Republic
  • Finland
  • Gemlany
  • Japan
  • Netherlands
  • Slovakia
  • Republic of Korea (South Korea)
  • Spain
  • Switzerlalld
  • United States Though generally classitled as pO\ver generation systems rather th311 nuclear safety systems, transformer failures have the ability to affect safety related systems. as \;veil as to pose a hazard to site personnel. Ageing systems lllay be more sHsceptible to failure, making lessons leamt tl'om previolls event and best practices a valuable operating experience tool.

4.2 Recent Events The United States issued Infonnation Notice 2009-10 (IRS 8024) addressing concems about mallltenance issues tor main transfonners after observing a significant increase in the number of failures despite industry guidance providing recommendations. Genmmy posted IRS 8049 describing complications following a transtonner tIre that revealed weaknesses in the ventilation system design as smoke it-om the fire \;vas 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, and scattered debris after a high voltage bushing on the malll tramtonner exploded. Seismic effects tollO\ving an earthquake in Japan caused a fire due to grounds on one of the malll transformers as described in IR:S 7922. The event ,vas complicated as the \vater supply tor frretlghting etforts \Va5 also disabled by dIe earthquake.

IRS 8008 11-mn Russia on the other hand. describes an event w'here alarms received in the control room alerted operators to tile deteriorating condition of the transformer insulation . allowing them to trip the transfonners betore a catastrophic failme occulTed. IRS 8011 frollll\rgentina and IRS 7947 11'om Lithuania describe situations where inadequate maintenance procedures mId design features resulted in actuation oftramt011l1er trip features, requiring reactor scrams.

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1\i'EA!CNRA/R/(20 11)6 4.3 Summary of Couutries' Respouses Several general conclusions can be dravm fi'om the various responses received. Transtonners are not regarded as nuclear safety equipment i.n any cOlUltry, and as such no conntry dillt responded (with the exception of Republic of Korea. which includes tnmsfonners in its regulations for periodic inspection by regulatory body inspectors) lilld regulations specifically addressing transfonner maintenance. Likewise. no country had a specific reporting requirement regarding tran.sformer failures. Recognizing that tramfonner failures can lead to reactor trips, most cOllltries do have regulations addressing maintenance programmes in general, and inspections to verify dIe effectiveness of these maintenance programmes. ill addition. reporfability 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 temperature alld level. along with cHlTents, voltages and capacity factor are available in the conu'ol room, or at least will cause alalms in the control room in the event of an abnom1:'l1 condition. Visual inspections are generallycanied ant 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. "lvlany licensees have adopted continuous online gas analyzers to trend the gas content in the tratlstonner oil tltr indication of insulation or dielectric breakdown. 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 tramtltnners be retrofitted if there are indications of possible deterioration.

As tmnstltmlers 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 recolllmends analyzing areas susceptible to single point failure to detennine the risk to the u'ansformer and the feasibility of adding redundancy. Some operators have redlmdant main transfonner tlip relays to minimize sptllious uips, but in most counuies they have determined that the trip risk from other large transtltrmers is sufficiently low that redlmdmlt features are not necessary or cost-effective.

All licensees have detailed procedmes addressing the plant response to a reactor u'ip caused by a tl'ansfonner failure, and most plants have abnormal operating procedures addressing 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 tall 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 sufikient persOlmel onsite with the experience and training necessary to pelfonn maintenance on transformers, and so this maintenance is usually contracted out. Plant personnel maintain ovet~~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 somce of concem for transfonner maintenance, especially if the procedures, training, and acceptance standaJds are not sutlicient. Updated industry guidance suggests that the licensee be involved at evet*y stage of contracted maintenance (including from tlle time of Oliginal manufacture) w*ith testing mld inspections to ensure the required level of quality is maintained.

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

specifically for transtbnner fires. l'vfultiple counttiescited operating experience fi'om previom fires, in particular the transfonner fire at Krummel Nuclear Plant in 2007. as providing valuable lessons learnt for complications that can arise from this type of file.

4.4 Commendable Practices The primary concern for a plant operator upon loss of a main transfonner. once immediate actions to place the plant in a safe condition are complete, is the availability of a replacement. The long lead time necessary for the manufacture of a ne\;I,i main transformer means that if there is no functional spare traIl';t011l1er available, the plant \vill remain shnt down tor an extended peri0l.1 of time.

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

Aside trom the initiating event (loss of pmver, reactor scram etc .) \vhich is likely to result from the failure of a large u'ansfonner, nucleflJ regulators have seen other causes for concern from a spate of recent failures. Catastrophic failures of the main transformer challenge operators with distractioIl'; from tIre, affected equipment, and the coordination of emergency operations \vhile they place the pIm}t in a safe. slmtdmvn condition. Fires and explosions pose a hazard to personnel and equipment and contribute to the difticulty of restoring normal conditions.

Predictive and preventive maintenance is key to maintaining eqnipment, and to detecting any degrading conditions befbre dley pose problems ibr operation, All plants have maintenance procedures detailing work to be perfbrmed or parameters to be observed at regular intervals. A programme dlat takes into account dIe condition ofthe transfonner dmlng these mainterlance intervals in order to inform fl.Jture maintenance requirements can help to extend the operating life of the transfonner and aid in detection of impending problems in time to prevent a catastrophic failure.

Japan has developed a transformer life management evaluation programme 'which incorporates time-based management and condition-based management along with life cycle management assessments at nvelve and t\venty-ibur years. to detennine future transtonner maintenance alld replacement requirements (see appendix),

Poor oversight of contracted maintenance personnel and a lack of understanding by plant personnel of main transfoflllers have been highlighted by industry groups as a possible contributor to transtltnner tailures. ?\*lost nuclear plants do not retain the expertise onsite tor anything more than routine sampling and maintenance. Operators need to ensure dillt contractors, required for more extensive maintenmlCe and testing, understand the quality control and procedural practices required tor nuclear plant operations. Republic of Korea and the United States noted that licensees \vho mn multiple reactor sites may maintain a central group responsible fbI' transfblmer maintenance.

facilitating the silmlng of operating experience between multiple sites and helping to ensure an under~standing of plant practices. The Republic of Korea also reported a sn'ong degree of on-site stafr training and involvement in transformer maintenance, w'11ich appears to be a good practice in light of the noted indllstry guidance.

hldmtry operating experience has identitled continuous online gas analysis as the best method for identifying an impending failure of a large oil-flUed transfOlmer, Advantages of online analysis include measlirements of gas content in the oil that are less susceptible to sampling eLTOIS, mId which allO\v for timely recognition of deteriorating conditions. However it is recognized that the cost-benefit analysis of back-f1tting u'ansfonners already in place may not justifY the expense. Benefits may be gained frOlll identifying degrading trends in key parameters dlat lllay indicate degraded insulation conditions. This degrading trend could justify dle lllstaUation of continuous monitoring 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 dIe Peach Bottom plant in the U.S .. regular oil samples noted higher than normal gas levels. prompting the licensee to install an on-line gas analyzer.

17 OAGI0001166_00017

1\i'EA!CNRA/R/(20 11)6 "Vhen the on-line analyzer detected gas levels above a pre-set limit, the plant shut dovm and replaced the transfonner before it actually failed. In any case. any new large. oil-tIlled transfonners that are installed should be equipped \\'ith 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 respollSe 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 h'ansfonner tIres present additional hazards, some plants have institnted specific training for dealing 'with the challenges presented by a large transfonner fire, In Japan, lessons leamt trom a transfonner fire at Kashiwazaki-Karhva 3 resulting from the earthquake in 2007 (IRS 7922)

'were applied to fire response training programmes aroHnd the COHllttY. In Spain. the Garofia Nuclear Power Plant lllC0l1)orates specitle tmnsfbmler fhe scenarios lllto fn'e response training. Canada and the Netherlands used operating expelience fi"om the Kntennnel fire in 2007 (IRS 8049) to inform their response to trallSfonner fires . Republic of Korea ensmes regular panicipation of offsite fire stations in plant fire drills to enhance cOllll1mnication and cooperation.

18 OAGI0001166_00018

5. RESPONSE OF OECD-~"'EA COUNTRIES TO TRANSFORMER FAILURE QUESTIONS TIle following section provides the sununary response of each OECD-NEA COlll1try that replied to the questions posed by the U. S. "N"'RC about main tranSf011l1er failures.

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

Licensees have implemented preventative and predictive maintenance programmes based upon manufacturer maintenance guidelines. internal and extemal operating experience. Online monitoring of transfonner key fault gasses provides an early waming of fault conditions that could lead to transformer failure. Oil temperature and level are monitored by the licensee. Additionally, thenllOgraphy, dissolved gas analysis. air cooling system check~ and inspectiom for oil leaks are performed. ~'ilaintenance and testing frequency is influenced by the results of pfe'violLS testiug, as \vell as by environmental and operational consideratiOlls.

Transformer maintenmlCe is typically conducted by site maintenance personnel who have received appropliate training on trallSfOnllers. Onsite staff verify transformer maintenance pertltnned by contractors. An offsite maintenance competence center. \\'ith extensive training provided by the equipment manufacturer, is available to shaJe operating experience about the tnmsformer fleet.

Operators perform daily maintenance rounds and w'eekly inspections of critical parameters.

The spare transfonneL~ 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 the instmctions provided by the flre brigade oUker. Fire brigade officers have been trained on the electrical dangers on site.

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

Transfonners, there are regulations which apply to maintenance programmes in general. These require the licensee to consider vendor recolllmendations . industry codes and standards, design and operating conditions, operating experience, and aging mallagement requirements in their maintenance programmes. More generally, licensees are required to ensure that maintenance on equipment is perionned regularly. and to industry standards, Systems important to the nudeaJ power plant are required to function reliably. Though transfonners are not considered safety significant, aild 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 impact on the reactor raises the level of regulatory interest in LOF transformers.

despite their non-safety status.

19 OAGI0001166_00019

1\i'EA!CNRA/R/(20 11)6 As 'with ather nuclear and nan-nuclear plant parameter~. the f'tmction of the regulator and the inspection statT is not to monitor specitk indications or detect degraded conditions, but rather to verity that the licensee monitoring progrannne is sufficient. and that licensee response to abnormal indications is in accordance with designated procedures.

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

Monitoring frequencies are based on established industry recommendations, ranging from continnous monitoring of vital temperatures and pressures (and in some case continuaus gas analysis) to' infrared thennography checks, Doble testing. and complete overhauls every fe\¥ years. 11aintenance frequency is determined by a combination of industry guidance, risk impOltance, operating experience. duty cycles and environmental factors.

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

5.3 Czecb Republic As tmnsfonners are not classified as safety related equipment. they are not specifically covered by regulatOlY requirements, Likewise, reportability requirements do not address transformer failures, however the transients resulting 110m tJanstomler failures are covered by the stfmdard events repOlting scheme. Additionally, as the regulator receives alllicemee event repOlts, including reports oftransfomler failures, specific reportabiliry requirements regarding large transformer failures are not necess31y. Resident inspectors pertltnn an inspection sample of general transfonner parameters to verity that they m'e within specification. however the sample size is small, and monitoring of paJameters 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 dielecttic propelties. Equipment required for continuing operation. including pumps, fans, and dryers are also monitored. The preventive maintenance schedule accOlmts tltr the age of the components, risk importance, duty cycle, and environmental conditions. with augmented inspection requirements in the event of abnonnal results or trends.

Operatop; receive periodic training on actions to be taken in accordance with abnormal operating procedures in the event of a tramtltnner malfimction. Operators are trained to' recognize abnomlal indications, however actual maintenance of the transformers. both preventive and reactive, is perf011l1ed by outside contractors . Contractors are expected to ensure the qnality of tlleir own \vorlc, which is also overseen by station system engineers, Licensee quality assurance inspectors also review cantractar work on a sample basis to emure it meets station standards. Station peI~~onneL including the tire brigade. are trained to respond to tIres, and abn011l1al conditians resulting from a tramtltnner fire are covered in operating procedures, 5.4 Finland As large transformers are classified as non-nuclear. in the lowest safety class, there are no specific regulatory requirements regaJding transformer maintenance programmes, nor are there specific repOltability reqnirements for transfOlmer failures. The regulator oversees liCeI1See implementation of all maintenance progratilllles, induding those for large transformers, particularly 20 OAGI0001166_00020

during ammal maintenance outages. The licensee is responsible for regular monitoring oftransfltnner 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 transient or disturbance.

Operators are provided with control mom readouts of key transfonner parameters and results of online hydrogen gas-in-oil analysis. Thellllal and optical sensors alld oil level ala11115 are also provided. In an drOIt to eliminate single point of failure trips, redundmlt main transfonner protective relays are provided. The preventive maintenance programme schedules inspections, surveillallCes, and component replacements at intervals mi1ging from monthly to decennial based on operating experience, inspection results, and component conditions. The transfonner lifetime management programme accounts for years of service, risk imponance, duty cycles, and transients to provide feedback to the preventive maintenance programme fbr maintenance scheduling. In the event of a degraded condition, the maintenallCe and surveillance schedule is advanced to ensure timely assessment oftransfonner operability.

Operatop; are trained on procedures for monitOling and operating the plant in the event of an abnomlal condition with the transionner, including grid disturbances and tran.sformer flres. \\rhile onsite personnel are sufficiently knowledgeable to recognize abnonnal conditions and evaluate operability, maintenance is generally contracted to outside organisations. Contract lnaintenance is overseen by the plant electrical nlaintenance manager. and contracted maintenance procedures are expected to meet the basic expectations of licensee maintenance procedures. Licensed and non-licensed operators, as \;vell as the tlie brigade, receive training Oil transformer !lre response, induding the wide-ranging and potentially 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 trans tonner, which can be indicative of potential problems, but even \'lith continuOlL~ monitOling, tllis breakdow'll may not be discovered lmtil it is too late. *Utilities collect and amlyse samples regularly to detennine the condition of the oil, as well as its water and gas content. Protective relays \'lbich can sense step challges in pressure or temperature and trip the tt*ansfonner offline are used to protect equipment and personnel in the event that testing fails to detect a problem before a failure ocellIS.

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 on time-based maintenance every six years and fhll assessments every tw*elve years. At tvventy-tltHI years, a prediction of remaining life is made and the maintenance schedule adjusted accordingly. Implementation of condition based maintenance is based on regular monitoring and trending of imp0l1ant parameters, including gas conceutt*ation and temperatures. (See Appendix: Japanese Typical Recommended Transformer Maintenance Program)

Transfonner maintenance is canied ont by contractors, overseen by the utilities, bur is not included in regular or abnormal procedures.. Abnonml procedures contain response requirements for 21 OAGI0001166_00021

1\i'EA!CNRA/R/(20 11)6 tramients resulting from transformer incidents, bnt do not address transfonner maintenance, Training on intreqnent activities relating to tranSf011l1erS is not included 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 transt011l1er fires is emphasized in training progranlll1eS, UlC0l1)orating lessons-leamt follo\;ving an earlier transformer fire.

5.7 Netherlands

}.*1ain trallSfonners are not classified as nuclear safety equipment; therefore they are not covered by regulations and are not monitored by the regulatory body Though there are no repOlting requirements specifically addressing transformer failures, there ale requirements tor grid disturbances, reactor tramients, alld fire damage, any of which might result trom a transt011l1er failure.

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

Abnonnal operating procedures fOCllS on respome to reactor plant transients and grid disturbances that may affect (or be affected by) transformer anomalies. Specif1c training on response to tramfonner tIres has been implemented as a response to the Kmemmel transfonner fire in 2007.

5.8 Slonkia Regulatiom; do not specifically target the reportiug of transfblmer failures. However, failures that affect 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 rounds to verify the proper operation of transfonner functions and check that levels, temperatures, and voltage readings are witlun specified ranges. Twice a year, the operator pertonus an oil sample analysis 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 maintenance activities are pert011l1ed by amite personnel under agreements \vith the grid operator, but are verified by dIe plant operator as meeting the requirements of the nuclear regulator.

Abnonnal operating procedures describe operational linuts for the transfonners and con'ective actions to be taken in case of abnomlal indications, induding slufiing the plant to operate in island mode. This allow's plant systems to be fed from standby lines or EDGs. Training is provided to operators on the use of nonnal and abnormal operating procedures. and on a regular basis to all plant pet'SonneL including the fire bligade, for emergency preparedness and scenarios involving transfonner failures.

5.9 Republic of Korea (South Korea)

Oil filled traIl';tonl1ers are identified in regulations as equipment subject to petiodic inspection by regulatory inspectors. Inspectors cOllflnn insulation resistance checks and protective device tests, and examine the condition oftap changet'S along \\'ith the exterior of the transfonnet*. If abnormal degradation is identified during the inspection, recommendations or findings may be issued by the regulatory body. There ale no regulatory requirements directly related to repOlting of transthnner failures, However, if an event is caused as a result of transformer failure. the liCetlSee repOlts that event to the regulator.

22 OAGI0001166_00022

Botb predictive and preventative maintenance is petformed on large oil tilled tmnsfonners.

Preventative maintenance has induded replacement of all transfomlers more tl1llil 23 years old, and replacement of protective relays on a 5-year cycle . The moisnu'e levels and gas concentration in the insulating oil are analysed every t\VO homs to detect degraded conditions, Thennography and plli1ial discharge tests occm each spring, Operators monitor the temperanu'e of the tIansfOlmer during

'walkdowns 1-3 times a shift. A pcr10dic inspection is perfonned by maintenance personnel once a month and transfonner engineers \;valk down the equipment to detemnne system imegrity on a quarterly basis. Automatic respoIl<;es, emergency actions and conective measnres required due to tmnsfonner failure have been clearly descI1bed in system operating, alarm response, and abnonnal operating procedures.

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

Maintenance \vork conducted by contractors is pcrJomled according to approved procedures and is supervised by the site maintenance and engineeI1ng divisions. Site statf is knO\vledgeable and proficient at maintaining large tmnstolmers. Training is performed on llil llillual basis llild includes tbeory. maintenallCe and operating experience . Workshops are beld to highlight relevant events and share experience in the operation and maintenllilCe of these transfonners. Both the onsite fire brigade and the offsite fire station have been trained tor onsite fire accidents, including transfonner flres.

5.10 Spain Transformer maintenllilCe is not specifically mentioned in regulations. and events me not repOItable except as they result in reactor transients.. Licensees pelform regular monitoring of components imp0l1ant to normal transfOlmer operation. Some licensees have installed continnous gas analyzers to provide tinle1y notice of impending failure: other licensees perform in-depth physical and chenncal analysis of oil samples on a scrni-aIllnal 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 conditiom or transients, additional mainteIlance will be pertol111ed in response to observation of deteriorating tIends.

Basic maintenance is pcrionl1ed by licensee persOlllel. however most maintenance is pertonned by contractors under the supervision of licensee personnel. Procedures detail the appropriate responses for alamnng conditions and poteIltial transients. The fire bligade receives specific training regarding transformer t1res, while licensed alld non-liceIlsed operators receive training on general fire-fIghting scenarios. Wlnle not specifically tOcused on transformer thes, this training has included drills involving transfonner fires.

5.11 Switzerland RegulatOly requirements addressing quality assurance and maintenance progrmmnes are applicable to the associated programmes for large transt011l1ers. These regulations also require repOlting of any failures that lead to an unplanned power reduction or cause damage to safety-classif1ed components. Events caused by lightning strikes are also reponable to the regnlatOIY body.

In addition. monthly llild quarterly reports on maimenance and testing, including that perfonned on large transtonners, are required. as are safety assessments performed every ten years. which include an evaluation of the condition of equipment. Monit0I1ng of transtbnner parameters is the responsibility of the plant. though the etIectiveness of maintenllilCe fmd monitoring programmes is subject to inspection by the regulator.

23 OAGI0001166_00023

1\i'EA!CNRA/R/(20 11)6 Transtonner operating conditions and readings are monitored as part of routine shift rmUlds.

The short-tenn and long-telm maintenance schedules are int1uenced by any nonnal alanm; received, results of regl.llm* monitorin~ and any conditions noted during regular maintenance. AU main transfonners have been replaced since Oliginal installation as part of power upgrades that made more efficient nse of the heat available tl"om the reactor plant rather than because of degraded conditions noted on the trmlsformers themselves. Ivlaintenance is usually perfolmed either by plant pers0l11lel or by qualifIed employees of the parent c0l1)oration, with oversight ftom plant personnel.

5.12 United States Though there is no regulation specifically addressing main transformer~. there are regulations requiting the licensee to monitor the pertonnance and condition of equipment to emure it is capable of fulfilling its intended tllllctlons. Quality assurance requirements also may apply to valious aspects of transfonner maintenance. Tramfonl1er failures are not reportable in 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. MonitOling of transformer operation and pertormance is the responsibility of the licensee. The regulator evaluates the effectiveness of the licensee maintenance programme.

Licemees monitor itnp0l1ant parameters on a contitmoll5 basis. The latest industry recommendations include installation of continuous dissolved gas analyzers, however not all licensees have completed this upgrade. Preventive maintenance schedules use industry and vendor recommendations, operating experience. trend results, and component age to detennine inspection and maintenance fiequencies. Indication.s of degradation generally resliit in increased monitoring and evaluation. Industry guidallCe recommends abnonnal operating procedures addressing any alarming or abnomlal condition.

Licensees are expected to have the knowledge and experience available tor most TOutitle transformer nlaintenmlCe. Any work that is pertoImed by contractors or off-site organisations should be perfOlmed under the oversight of licensee personnel familiar with the equipment and the work to be pertomled. Contractors are expected to have procedures and qualitkations ",*hich meet the requirements of site procedures and qnalitkations. Industry guidance also recommencis that licensees velify contractor work at multiple stages of a project, itlCluding mHlmfactme, to ensme the quality of the work Training on transformer fires is expected to be provided to the tire brigade and to licensed and non-licensed operators. Fire fighting procedures should include consideration not just of the fire, but of potential hazards involved in a tramtonl1er fire, and of operations independent of the grid.

24 OAGI0001166_00024

APPENDIX: JAPANESE TYPICAL RECOMMENDED TRANSFORMER MAI~IENANCE PROGRAM

. Thermal Fal'tor (Normal, Excess load~ over l'urrent, etc.)

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

-Mechanical Factor (ExtcrJwl <lcddenhll over l'urrcnt~ etc.)

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

- Surge Current

- External Accident Current Lifetime iiiiiiiiiiM!!M>" .

~~~~a

~~~~~~~~~~~~~~~II~~~~~:*

.:.:"- .......~.......~.......~

TB?l.J: Time Based Maintenance

(' B:J\l: ('ondi hon Based l\Iaintenance Fig-l Japanese Typical Recommended Transformer Maintenance Program

Life Management Evaluation (1) <Referenced standard and

- Analysis results of dissolved g'as in oil g'uidw:1G(:>

- Degradation of the gasket *The ,J<'Ipan Eledrical

- COl~ro:;;ion of t.he tooier (Heat exchanger} l\lanufadurers'

  • Degradation of oil feed pump and fali bearings Association:
  • Performance ofth(: -insulation o-il

- Degradation of instrumentations "Proposed replacement time of oil c(xlled traustbrmer Life Management Evaluation (n) accessories

- Residual life evaluation of insulation papers (spare parts)"

- Purchasing of t.he spare part.:;; quitted t.o produce QENFl'nW7)

U:rC)

  • Compliance t.o t.he latest codes and st.andards *Electrical.Joint Research Report (Sea breeze, structmal integrity of the tanks) "Maint(mIH1C(; Management (If Oil cooled Transformer:;;"

In case of Service Life Extension:

Preparing .Life E*xiem;:ion Prognun e.g. to decrease oil temperature

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