Modifications of the document Version Date Authors or paragraphs modified Description or comments 0 2015-07-01 All All Preliminary issued 1 2015-08-14 See QA page All WP 40 partners comments and contribution incorporated 2 2015-11-17 M. Kumar (LRC) All Comments and contribution received from JSI, CCA, GRS, EDF, INRNE, TUS, UJV, Tractebel, Iberdrola 3 2016-03-22 M. Kumar (LRC) All Comments and contributions received from GRS, LRC, Nubiki, CCA, JSI, INRNE, TUS, UJV, SSTC, IRSN, RATEN ICN, JANSI, ENEA. 4 2016-05-18 M. Kumar (LRC) Review comments Incorporation of review comments received from GRS, LRC, JSI, INRNE, Iberdrola and EDF. 5 2016-05-23 E. Raimond (IRSN) Review Approval review. Few editorial modifications and additions in the report. 6 2016-11-14 M. Kumar (LR) Review comments Incorporated End-User comments and ASAMPSA_E workshop recommendations. SARNET comments are also included. Contribution from GRS, SSTC, INRNE, LR. 7 2016-12-19 M. Kumar (LR) All technical editing, review comments received from GRS and JSI. 8 2017-01-16 H. Löffler (GRS) Mostly Section 4 Inclusion of IRSN updates 9 2017_01-23 E. Raimond (IRSN) Few Approval reading. List of diffusion European Commission (scientific officer) Name First name Organization Passalacqua Roberto EC ASAMPSA_E Project management group (PMG) Name name Organization Raimond Emmanuel IRSN Project coordinator Guigueno Yves IRSN WP10 coordinator
Decker Kurt Vienna University WP21 coordinator Klug Joakim LR WP22 coordinator until 2015-10-31 Kumar Manorma LR WP22 coordinator from 2015-11-01 Wielenberg Andreas GRS WP30 coordinator until 2016-03-31 Löffler Horst GRS WP40 coordinator WP30 coordinator from 2016-04-01 REPRESENTATIVES OF ASAMPSA_E PARTNERS Name First name Organization Grindon Liz AMEC NNC Mustoe Julian AMEC NNC Cordoliani Vincent AREVA Dirksen Gerben AREVA Godefroy Florian AREVA Kollasko Heiko AREVA Michaud Laurent Hasnaoui Chiheb AREXIS Hurel François AREXIS Schirrer Raphael AREXIS De Gelder Pieter Bel V Gryffroy Dries Bel V Jacques Véronique Bel V Van Rompuy Thibaut Bel V Cazzoli Errico CCA Vitázková Jirina CCA Passalacqua Roberto EC Banchieri Yvonnick EDF Benzoni Stéphane EDF Bernadara Pietro EDF Bonnevialle Anne-Marie EDF Brac Pascal EDF Coulon Vincent EDF Gallois Marie EDF Henssien Benjamin EDF Hibti Mohamed EDF Jan Philippe EDF Lopez Julien EDF Nonclercq Philippe EDF Panato Eddy EDF Parey Sylvie EDF Romanet François EDF Rychkov Valentin EDF Vasseur Dominique EDF Burgazzi Luciano ENEA Hultqvist Göran FKA Karlsson Anders FKA Ljungbjörk Julia FKA Pihl Joel FKA Loeffler Horst GRS Mildenberger Oliver GRS Sperbeck Silvio GRS Tuerschmann Michael GRS Wielenberg Andreas GRS Benitez Francisco Jose IEC Del Barrio Miguel A. IEC Serrano IEC Apostol Minodora RATEN ICN Farcasiu Mita RATEN ICN Nitoi Mirela ICN Groudev Pavlin INRNE Stefanova Antoaneta Andreeva Marina INRNE Petya Petrova INRNE Armingaud François IRSN Bardet Lise IRSN Baumont David IRSN Bonnet Jean-Michel IRSN Bonneville IRSN Clement Christophe IRSN Corenwinder François IRSN Denis Jean IRSN Duflot Nicolas IRSN
Duluc IRSN Dupuy Patricia IRSN Durin Thomas IRSN Georgescu Gabriel IRSN Guigueno Yves IRSN Guimier Laurent IRSN Lanore IRSN Laurent Bruno IRSN Pichereau Frederique IRSN Nadia IRSN Raimond Emmanuel IRSN Rebour Vincent IRSN Sotti Oona IRSN Volkanovski Andrija JSI Prošek Andrej JSI Alzbutas Robertas LEI Matuzas Vaidas LEI Rimkevicius Sigitas LEI Häggström Anna LR Klug Joakim LR Kumar Manorma LR Olsson Anders LR Borysiewicz Mieczyslaw NCBJ Kowal Karol NCBJ Potempski Slawomir NCBJ La Rovere Stephano NIER Vestrucci NIER Brinkman Hans NRG Kahia Sinda NRG Bareith Attila NUBIKI Lajtha Gabor NUBIKI Siklossy NUBIKI Morandi Sonia RSE Caracciolo Eduardo RSE Dybach Oleksiy SSTC Gorpinchenko Oleg SSTC Claus Etienne TRACTEBEL Dejardin Philippe TRACTEBEL Grondal Corentin TRACTEBEL Mitaille Stanislas TRACTEBEL Oury Laurence TRACTEBEL Zeynab Umidova TRACTEBEL Yu Shizhen TRACTEBEL Bogdanov Dimitar TUS Ivanov Ivan TUS Kaleychev TUS Holy Jaroslav UJV Hustak Stanislav UJV Jaros Milan UJV Kolar Ladislav UJV Kubicek Jan UJV Decker Kurt UNIVIE Halada VUJE Prochaska Jan VUJE Stojka Tibor VUJE REPRESENTATIVE OF ASSOCIATED PARTNERS (External Experts Advisory Board (EEAB)) Name First name Organization Hirata Kazuta JANSI Hashimoto Kazunori JANSI Inagaki Masakatsu JANSI Yamanana Yasunori TEPCO Coyne US-NRC González Michelle M. US-NRC
ASAMPSA_E Partners The following provides the list of the ASAMPSA_E partners involved in the development of this document. 1 Institute for Radiological Protection and Nuclear Safety IRSN France 2 Gesellschaft für Anlagen- und Reaktorsicherheit mbH GRS Germany 4 Ricerca sul Sistema Energetico RSE S.p.A. Italy 5 Lloyd’s Register Consulting LR Sweden 6 Nuclear Research Institute Rez pl UJV Czech Republic 8 Cazzoli Consulting CCA Switzerland 9 Italian National Agency for New Technologies, Energy and the Sustainable Economic Development ENEA Italy 11 IBERDROLA Ingeniería y Construcción S.A.U IEC 12 Electricité de France EDF France 14 NUBIKI NUBIKI Hungary 15 Forsmark kraftgrupp AB FKA Sweden 16 AREVA NP SAS France AREVA NP SAS France 17 National Centre for Nuclear NCBJ Poland
Research Institute 18 State Scientific and Technical Center for Nuclear and Radiation Safety SSTC Ukraine 22 TRACTEBEL ENGINEERING S.A. TRACTEBEL Belgium 24 Institut Jožef Stefan JSI Slovenia 25 Institute of nuclear research and nuclear energy – Bulgarian Academia of science Bulgaria 26 Autonoma Technologii pentru Energia Nucleara Institutul de Cercetari Nucleare RATEN INR Romania 27 Technical University of – Research and Development Sector TUS Bulgaria CONTENT
Type of initiating event Time when fuel damage occurs (related to the IE) Amount of water surrounding the fuel Status of the containment protection and mitigation systems Recovery of fuel cooling Amount of water in Refuelling Water Storage Tank (RWST) (PWR specific) Amount of water in the condensation pool (BWR specific) Primary system pressure boundary integrity, e.g. Primary system intact Primary system open but RPV head still mounted RPV head dismounted Primary system pressure Status of high pressure and low pressure safety injection system. The PDSs are grouped based on the POSs of the plant at power operation and during refuelling outage [47], e.g. Group 0 – Full power operation Group 1 – POSs similar to full power operation. Both the RCS and the containment are normally closed. Group 2 – POSs in which the RCS is closed but the containment is open. Group 3 – POSs in which both the RCS and containment are open. The fuel is located in the reactor vessel. Group 4 – POSs which is a special case because the fuel is relocated to the SFP. SHUTDOWN STATES L2 PSA This section on guidance for shutdown states is focusing on the RPV and the reactor core and complement to the existing ASAMPSA2 guidance [1] for L2 PSA. Obviously, the spent fuel pool is of interest in shutdown states, but the SFP is addressed separately in section 3 of this report below. In general, shutdown states are subdivided into two main groups based on the primary system integrity: states with closed RPV head and states with open RPV head. These states might also be subdivided in different subgroups, the number of which depends on reactor type and operational instructions. These sub-states are defined based on their impact on the core damage (L1 criteria) or fuel damage during shutdown and are associated to different plant configurations (barriers of retention and boundary conditions) and mitigation systems availability during the refuelling process. For L2 PSA, also the source term confinement into the containment should be taken into account and new sub-states need to be included when the containment at full power is modified into the plant configuration during the refuelling. If primary system integrity is given up for maintenance works before opening of RPV head, this period can be separated in a new sub-state or integrated into the states with open RPV head.
Both at-power and shutdown conditions should be addressed in the SFP PSA, however different operating modes for a SFP PSA may not be as relevant as for the reactor core. During shutdown conditions the plant configuration typically varies more and POSs that cover all these different configurations should be defined. The definition is made in the same way as for the reactor core shutdown PSA (for instance regarding system availabilities), but for the SFP PSA the following specific conditions also need to be taken into consideration: transfer canal (if applicable) between SFP and reactor building pool; opened, closed, amount of fuel offloaded to the SFP; complete core offload, partial core offload, reloading of new fuel; fuel movement complete; amount of cooling in the SFP. Note that this section covers issues that can be of interest for the SFP PSA for a plant to be commissioned or already in operation. In principle the types of accidents in SFP PSA can be divided into two categories: events/ sequences, loss of cooling events/ sequences (or non-draining IEs). Draining events may be caused by inappropriate operator action, seismic induced structural failures, heavy load drops, loss of coolant accidents (LOCAs), and reactor-related phenomena causing structural failure (e.g. steam explosion, hydrogen detonation). For non-draining events, the set of initiating events can be derived from an analysis of the situations leading to the temperature increase, i.e. to the loss of the cooling system, which may be due either to malfunctions in the cooling system itself or its support functions including electrical supply or the cooling chain. In L1 PSA, it is necessary to study each plant state (POS) because of the different configurations or characteristics of structural failures and support systems of electrical supply or cooling chain. Also, the timing of the release is very dependent on the sequence/ initiating event. This is also important for operator actions. However in L2 PSA it is almost irrelevant which particular combination of initiating event and failure has led to loss of cooling or draining and loss of coolant. The following spent fuel pool events leading to fuel damage should be taken into account: loss of cooling to the SFP (including failure of support systems and loss of coolant inventory loss from the SFP; heavy load drops, loss of coolant accidents (LOCAs), reactor-related phenomena causing structural failure, reactivity accidents;
Other fuel locations than SFP Depending on the plant design, apart from the SFP there may be other locations where fuel is present e.g. cleaning loops, fuel handling systems, dry storage, and transport casks. It is plant specific whether events in these locations can lead to fuel damage in the related system, or whether an event in these systems can trigger other failures and fuel damage in other locations, however this guidance is focused on fuel damage only in SFP. Shared SFPs Not each reactor is assigned to one dedicated SFP. For example, two reactors may a single pool. Also, a single reactor may store fuel in more than one pool, or two reactors at the same site may move fuel between both pools located in common or separated buildings that may or may not be connected. Thus, guidance is needed to address the differences and potential interactions between shared SFPs in an integrated way. Density of spent fuel racks Some pools contain high-density spent fuel racks which allow multiplying the number of stored assemblies. In such a case the consequences of fuel damage may propagate too much larger populations of fuel assemblies. These racks also have much higher overall decay heat and larger fission product inventory. Therefore, the density of the fuel racks should be considered. Spent fuel building ventilation The spent fuel building ventilation flow rate is important in determining the overall building energy balance. Airflow through the building is an important heat removal mechanism. On the other hand it also provides a source of oxygen for zirconium oxidation. Particular heat transfer mechanisms for fuel pools There are several heat transfer mechanisms that can influence the cooling of spent fuel during various postulated severe accident scenarios. These include: convective cooling to the surrounding steam cooling from surrounding steam generated by boiling coolant, conduction through the ends of the fuel rods, radiation cooling. The degree of success associated with different heat transfer mechanisms depends on the configuration of the SFP, rack/canister design (e.g., closed or open lattice), density of the fuel assemblies, arrangement of the hottest bundles within the SFP lattice and the SFP level. Structural integrity of fuel racks For recently discharged fuel or for severely restricted air flow (e.g. high density spent fuel racks) the exothermic oxidation reaction is predicted to be very vigorous and failure of both the fuel rods and the fuel racks is expected. The steel racks may not be able to maintain structural integrity because of the sustained
diameter is 240 mm. In all other cases operator actions are requires for actuation of LPIS. POS8 Below 70 Atm Open (vessel head off) open Reactor flange level Operation of one train of TQn2 /RHRS. Reactor is at cold shutdown before outage. All control rods are inside the core. Boron concentration is at 16g/kg.
Availability of new COP system. POS15 From below 70 to 160 Between 18 and 25 Closed Closed Full, N2 in pressurizer Or water-solid Nothing Reactor is at intermediate shutdown after outage. All control rods are inside the core. Boron concentration is at 16g/kg. Safety systems TQn2, TQn3, TQn4, TQn1 and DC are disconnected.
POS17 From 230 to 280 From 70 to 160 Closed Closed Full, steam in pressurizer. Secondary system (4 SGs are fed by 2 one auxiliary feed pumps and steam removed through BRU-K). Reactor is at hot shutdown after outage with availability of all safety systems and of their automatic protections. All control rods are inside the core. Boron concentration is at 16g/kg. Operation of one TK makeup pump. 4 MCPs in operation.