Nuclear power plant commissioning experience

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<ul><li><p>ensti</p><p>Event</p><p>hereppe</p><p>evets.g oto</p><p>study (centralwer Phnicalct; in, manu</p><p>(Bruynooghe and Nol, 2010), (Martin Ramos et al., 2010).Interest in constructing new nuclear power plants is increasing</p><p>worldwide. Some countries are embarking in a nuclear program forthe rst time, others decided to re-start the construction of nuclearpower plants after a hiatus of decades. According to the PowerReactor Information System (PRIS) of the International Atomic</p><p>Nuclear Regulatory Commission (US NRC) report to the Congress,dated 1984 (United States Nuclear Regulatory Commission (US-NRC), 1984). More recently, the Nuclear Energy Agency (NEA) ofthe OECD created the Working Group on the Regulation of NewReactors (WGRNR) which examines the regulatory issues of siting,licensing and supervision of the new NPPs.</p><p>However, there is no recent comprehensive study publishedon lessons learned from events related to pre-operational phases.As a result, the Member States Safety Authorities participating to</p><p>* Corresponding author. Tel.: 31 224 56 51 88; fax: 31 224 56 56 37.</p><p>Contents lists availab</p><p>u</p><p>ls</p><p>Progress in Nuclear Energy 53 (2011) 668e672E-mail address: benoit.zerger@ec.europa.eu (B. Zerger).In the European Union, in order to support the Community activi-ties on evaluation of NPP operational events, a centralized regionalClearinghouse on NPP OEF was established in 2008 at the JointResearch Centre e Institute for Energy (JRC-IE), on request of NuclearSafety Authorities of several Member States, in order to improve thecommunication and information sharing on OEF, to promote regionalcollaborationonanalyses of operational experience anddisseminationof the lessons learned (Nol, 2010).Oneof the tasksperformedconsistsin performing in-depth analysis of event families (topical studies)</p><p>often based onwork done in similar ongoing or completed projects.Consequently, lessons learned from the past construction</p><p>periods or from the ongoing construction projects are veryimportant for the increased number of utilities and regulatorsinvolved in the construction of new NPPs in order to reduce theprobability that construction or commissioning problems whichalready occurred happen again.</p><p>Efforts to collect lessons learned form construction experiencehave already been done in the past, for example the United States1. Introduction</p><p>The results are extracted from a2010) which has been done by thepean Clearinghouse on Nuclear PoFeedback (OEF) in the frame of tectechnical report on preselected subjefrom events related to constructionsioning of Nuclear Power Plants.0149-1970/$ e see front matter 2011 Elsevier Ltd.doi:10.1016/j.pnucene.2011.04.010ration after commissioning tests and the management of the temporary devices. 2011 Elsevier Ltd. All rights reserved.</p><p>European Commission,ised ofce of the Euro-lant (NPP) Operationalwork e preparation ofthis case on experiencefacturing and commis-</p><p>Energy Agency (IAEA), 55 construction projects are currentlylaunched or under consideration worldwide.</p><p>Starting new build is very demanding since much of the earlierexperience and resources have progressively been lost from thenuclear industry. Circumstances are quite different from 1970swhen most of the currently operating plants were constructed.Vendors had large experienced organizations ready to go ahead,and had less need to rely on subcontractors. In addition, there wasno shortage of skilled manufacturing capacity, and designs wereTestConstructioncommissioning-related events. These recommendations concern mainly the time of the testing, thescope of the tests, the documentation of the tests, the test acceptance criteria, the systems recongu-Commissioning This paper summarizes the main lessons learned and the main recommendations concerning theNuclear power plant commissioning exp</p><p>Benot Zerger*, Marc NolEuropean Clearinghouse on Operational Experience Feedback for Nuclear Power Plants, IThe Netherlands</p><p>a r t i c l e i n f o</p><p>Article history:Received 21 December 2010Received in revised form21 December 2010Accepted 26 April 2011</p><p>Keywords:ExperienceFeedback</p><p>a b s t r a c t</p><p>In this paper, we present tnuclear power plants andare extracted from a studytional Feedback about theof new nuclear power planAfter the initial screenin</p><p>the lessons learned specicthe commissioning.</p><p>Progress in N</p><p>journal homepage: www.eAll rights reserved.rience</p><p>tute for Energy, Joint Research Centre, European Commission, P.O Box 2, 1755 ZG Petten,</p><p>results of the analysis of the events related to the commissioning of neworted to the IAEA International Reporting System database. These resultsrformed by the European Clearinghouse on Nuclear Power Plant Opera-nts related to the construction, the manufacturing and the commissioning</p><p>f the database, we have analysed in detail 34 events in order to highlightdifferent components and to raise the general recommendations related to</p><p>le at ScienceDirect</p><p>clear Energy</p><p>evier .com/locate/pnucene</p></li><li><p>distinguish the relevant events.</p><p>the start of operation, it was assumed that their occurrence wouldbe higher at the beginning of commercial operation.</p><p>The initial search with the combination of codes selected in thepreceding section, the text searches and the date searches yielded558 events (see Table 1 below).</p><p>After removing the overlaps, there are 409 events remaining forthe nal short list.</p><p>The rst step of the screening consists in selecting the relevantevents and in eliminating the others.</p><p>Events were rejected because they were related to plant modi-cations, because they are not relevant or because the IRS report is</p><p>Nuclear Energy 53 (2011) 668e672 669Additionally, a word or phrase can be searched in all or in part ofthe reports.</p><p>For this study, the IRS database was searched by codes, by textstring searches and by date.</p><p>A systematic list of codes can be found in Appendix C Dictionaryof Codes of the IRS Guidelines (IAEA, 2009). This list has beenreviewed in detail to select the combination of codes to retrieve theevents of interest. The selected code are indicated in the tablebelow.</p><p>Moreover the results of text string searches of the wordcommissioning in the elds title, abstract, root causes andlessons learned are added to the code-driven query.</p><p>Finally, the events whose date preceded the date of start ofoperation were selected, as well as the events that occurred duringthe year following the start of operation. Indeed, even thoughThe web-based IRS has an advanced search tool to query theevents database by setting a combination of criteria on the elds:</p><p>- Guidewords- Countries- Plant names- Reactor type- Reactor supplier- Plant capacity- Incident date- Report submission date- IRS number- Start of commercial operationthe European Clearinghouse on OEF agreed that it was necessary toperform an up-to-date analysis of both ancient and recentconstruction experience.</p><p>The study covers construction, commissioning andmanufacturing events, of which origin is prior to the start of thecommercial operation, in order to raise lessons learned andrecommendations for current and future construction programmes.</p><p>This paper focuses on the events related to the commissioningstage, which is dened by the IAEA glossary (IAEA, 2007) asfollows: the process by means of which systems and componentsof facilities and activities, having been constructed, are madeoperational and veried to be in accordance with the design and tohave met the required performance criteria. It gives complemen-tary results to the IAEA safety guide (IAEA, 2003).</p><p>2. Methodology</p><p>The Incident Reporting System (IRS) is an international systemjointly operated by the IAEA and the Nuclear Energy Agency of theOrganisation for Economic Cooperation and Development (OECD/NEA). It contains about 3600 event reports that provide detaileddescriptions and preliminary analyses of the events causes thatmay be relevant to other plants.</p><p>The IRS establishes a detailed framework inwhich the plant andthe characteristics of the incident can be classied according toa systematic set of codes which is later on very useful to retrieve theinformation.</p><p>2.1. Screening of the database</p><p>In the rst stage, the commissioning-related events among theevents reported to the IRS from the start-up of this system until 30November 2009 are identied. The list of events is screened to</p><p>B. Zerger, M. Nol / Progress inconstruction or commissioning events can be detected years afternot detailed or complete enough to be used for this report.After this step, there were 34 remaining relevant IRS reports.</p><p>2.2. Analysis of the selected events</p><p>In the second stage, the selected events are analyzed to identifyand group the lessons learned from the incidents in differentcategories. For each category, a brief description is given of thenature of the root and direct cause or both, the consequences andthe lessons learned.</p><p>Each of these categories is further classied according to thetype of concerned component: pipes, pumps, valves, electricalcomponents, Instrumentation &amp; Control, pumps, re protection,ventilation and emergency diesel generators.</p><p>This structure enables to raise recommendations applicable foreach type of components. Moreover, it enables to identify moregeneric recommendations than a classication in systems whichare dependant on the reactor design.</p><p>3. Discussion</p><p>Fig. 1 shows the distribution of the commissioning events pertype of component. Almost half of the events relate to I&amp;C de-ciencies, 24% are related to mechanical components (pipes, valves,pumps) and the remaining events are related to re protection,electrical components and emergency diesel generator.</p><p>3.1. Instrumentation and control</p><p>Fifteen IRS commissioning events related to I&amp;C deciencies.The following events should be noted:</p><p>- Three events describe deviations caused by commissioningactivities such as the disconnection of control room alarms toreduce the interference with normal activities, impropermodication of logic on containment hatch doors, or completeloss of the reactor protection system due to inadequate prep-aration of commissioning tests.</p><p>- Two events report undetected deviations during commis-sioning tests: a mistake in the I&amp;C of a radioactive release</p><p>Table 1Results of the IRS queries.</p><p>Query Number of registeredevents</p><p>2.4. Pre-operational 82.4.2 Commissioning 675.4.4. Equipment start-up 205.4.13. Commissioning</p><p>(of new equipment)12</p><p>Text searches 120Date searches 331</p><p>TOTAL 558</p></li><li><p>insufcient scope of commissioning, which left deciencies</p><p>Nuclsystemwhichwas not detected because the sump sensors werenot tested, and failure of a pressuriser safety relief valve to closebecause the control signal from the reserve control panel wasnot veried.</p><p>- During a load rejection test, a fast trend update program wasturned on to collect data, which caused an unexpectedbehaviour of the reactor. A fault had been detected in thissoftware at commissioning stage but had not been correctedbecause it had been analysed as without any consequences onother programmes.</p><p>- Discrepancies between vessel level swell sensors were due tosnubbers found in three of the sensing lines. The presence of</p><p>Fig. 1. Distribution of IRS commissioning events.B. Zerger, M. Nol / Progress in670these snubbers was not documented and it was assumed thatthey were installed during the commissioning period beforeinitial start-up for sensor testing purposes.</p><p>The main lessons learned are:</p><p>- The need for safety and impact analysis prior to commissioningactivities</p><p>- Software with known or suspected faults should not be used incontrol circuits as it may have an unexpected inuence onother programs.</p><p>3.2. Mechanical components</p><p>Two commissioning events related to pumps. The rst eventreports the failure of the three seals of a Reactor Coolant Systempump which could be explained by the pressure or temperaturetransients during the commissioning tests. The second eventreports insufcient performance of the containment spray pumpsdue to excessive pressure loss in the heat exchangers, whichremained undetected for a long time because the entire contain-ment spray system was never tested.</p><p>Thiseventemphasized theneed tocarryout complex testsof safetysystems in condition representative of full accident conguration toverify that they comply with their design characteristics (partial testsof the recirculation by-pass lines may not be enough).undetected:</p><p>- High voltage cables had not been adequately tested during thecommissioning stage. As a result, hidden defects in the insu-lation of the supply cables for the protection sensors in thesecond safety system train were not discovered in time.</p><p>- Ineffective verication of the backup batteries for re alarmcontrol panels due to insufcient functional checks duringcommissioning, maintenance and testing.</p><p>- Breaker logic was not fully tested because the breakers weremistakenly assumed to be the same as those installed andalready tested in another plant unit.</p><p>A fourth event related to the commissioning activities them-selves, when a grid disruption occurred during battery testing andled to a loss of power supply. Afterwards, the testing ranges for thebatteries were modied to ensure that they remained connected tothe electrical switchboards and consumers during unloading tests.</p><p>The lessons learned are:</p><p>- To dene a sufcient scope for commissioning activities.- To take into account the loss of external power during thetesting of batteries.</p><p>3.4. Fire protection</p><p>Four IRS events are relevant for this section:</p><p>- Fire detection did not actuate because too many detectors weretted in the same loop and because the commissioning testsdid not cover the situation where a lot of detectors are chal-lenged simultaneously.</p><p>- Undetected aws in functioning of dampers because the damperswere not tested as a whole, but each component was testedseparately (thermal actuation, electrical remote actuation)</p><p>- A CO2 re protection system was kept in manual mode toprevent its actuation on sensing welding fumes but wasnevertheless actuated by welding works because of a wiringerror dating from initial construction that had not beendetected during commissioning.</p><p>- A re protection valve remained partially open after commis-sioning tests</p><p>- A re propagated quickly during commissioning because theOne commissioning event was reported involving pipes:a temporary valve needed for commissioning was left on aninstrumentation pipe, which led to a high frequency vibration cycleand subsequently to the fatigue fracture of the pipe.</p><p>Two commissioning events related to valves. In one case,temporary bolts which clamped a valve for transportation andhydrotests purposeswere left after commissioningandblocked reliefvalves in the closed position, which led the licensee to improve themonitoring of these temporary bolts. In the other case, a feedwatercheck valve failed partially because the commissioning tests allowedthe feedwater system to be operated in violation of procedures.</p><p>These events show the needs to manage properly the temporarydevices and that the commissioning tests can also be a cause offailure and should...</p></li></ul>

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