SARNET – Severe Accident Research Network University of Manchester School of Mechanical Engineering, G. Begg Building CFD Workshop on Test-Cases, Databases & BPG for nuclear power plants applications 16 th July 2008 M. Reeks 1 and T. Haste 2,1 1 University of Newcastle-upon-Tyne 2 PSI Villigen, Switzerland,

SARNET – CFD Workshop, University of Manchester, July OVERVIEW SARNET is a Network of Excellence in the Nuclear Fission area of the EU 6 th Framework Programme, with the general aim of integrating in a sustainable manner European research on severe accident phenomenology in light water reactors The network started in April 2004 and will finish in September 2008; a successor project is being negotiated for a further 4 years in the 7 th Framework programme After a brief summary of project organisation and aims, this presentation indicates how CFD methods are used in the project overall, with focus on the Source Term area, that studies the release and transport of radioactive fission products from the reactor core to the environment INTRODUCTION T Albiol et al. ‚ SARNET: Severe Accident Research Network of Excellence, ICONE15, Nagoya, Japan, April 2007

SARNET – CFD Workshop, University of Manchester, July Severe Accident Research NETwork of excellence Currently: – 18 European Countries and Canada – 51 organizations  19 Research organizations  10 Universities  11 Industry organizations  4 Electricity producers  7 Safety authorities and technical support organisations – More than 230 researchers – About 20 PhD students – 800 to 900 person-months per year – About 10M€ effort per year (1.6M€ funded by the EC per year)

SARNET – CFD Workshop, University of Manchester, July SARNET OBJECTIVES Resolution of still pending issues important for reactor safety Optimised use of available resources and competences on severe accidents throughout Europe Knowledge transfer for safety application Perpetuate the competence on severe accidents Encapsulation of the knowledge base on severe accidents through the lumped-parameter ASTEC code – this program calculates the progress of severe accidents in light water reactors from initiating event through to release of radioactive fission products to the environment – it enables the results of the scientific research to be used in reactor applications MAIN OBJECTIVES

SARNET – CFD Workshop, University of Manchester, July SARNET ACTIVITIES SARNET is organised into a number of work packages covering – integrating activities (such as research prioritisation, database management, ASTEC development) – jointly executed scientific research (focussed on corium, containment and source term matters), and – spreading of excellence (such as organisation of training courses and mobility of researchers) CFD is one of a number of analysis methods used in the jointly-executed scientific research (‘topical’) areas – used in all these areas, but mainly for containment and source term studies ORGANISATION

SARNET – CFD Workshop, University of Manchester, July WORK PACKAGES WP 17 : ET Education and Training WP 18 : BOOK Book on severe accident phenomenology WP 19 : MOB Mobility programme Spreading of excellence activities Integrating activitiesJointly executed research activities WP 1 : ACT Development of an Advanced Communication Tool WP 6 : IED Implementation of Experimental Database WP 7 : SARP Definition of Severe Accident Research Priorities WP 8 : IA Integration Assessment WP 2 : USTIA ASTEC Users Support and Training, Integration, and Adaptation WP 3 : PHYMA ASTEC PHYsical Model Assessment WP 4 : RAB ASTEC Reactor Application Benchmarking WP 14,15,16 : SOURCE TERM FP Release and Transport Aerosol Behaviour impact on Source Term Containment Chemistry impact on Source Term WP 20 : Management WP 12,13 : CONTAINMENT Hydrogen behaviour Fast Interaction in Containment WP 9,10,11 : CORIUM Early phase core degradation Late phase core degradation Ex-vessel corium recovery WP 5 : PSA2 Level 2 PSA methodology and advanced tools

SARNET – CFD Workshop, University of Manchester, July Integral numerical simulation of reactor accident with core melting (Severe Accidents) IRSN-GRS property : ~ 10 m-y/y in charge of software development and user support Has been distributed to 26 SARNET organizations SARNET scientists support for model improvement and physical assessment: ASTEC capitalizes, in terms of models, all the knowledge produced in the frame of the Network 40 trained users contribute to joint validation programme (mobilizes around 20 m-y/year) One major version delivered in July 2005 (V1.2) Size: ~ instructions Speed: ~ 3-10 hours to compute 24 h of transients ASTEC ASTEC integrates the technical knowledge in SARNET

SARNET – CFD Workshop, University of Manchester, July USE OF CFD METHODS IN SARNET CFD is used in a number of applications, such as – design of experiments – interpretation of experimental results – plant studies, e.g. to determine the parameter ranges for separate-effect tests – benchmarking system-level codes, in this case principally ASTEC – one also notes use in reactor applications outside SARNET to look at detailed aspects where lumped-parameter methods are not sufficient, e.g. where 3-D flows are important, CFD results can be used to guide the use of lumped parameter codes regarding noding, X-flow resistances, other tuneable parameters etc. Validation of CFD methods and development of best practice per se are not main aims within SARNET – the codes are applied rather than developed and validated, and the users are assumed to know how to use their codes effectively – note also the CFD activities within OECD/NEA/GAMA, with best practice guidelines, these are not within SARNET but many of the same organisations are involved USE OF CFD - GENERAL

SARNET – CFD Workshop, University of Manchester, July CONTAINMENT STUDIES Examples are: – Interpretation of results from the TOSQAN and MISTRA tests on influence of containment sprays on the atmosphere behaviour (depressurisation, gas mixing), comparison of LP and CFD methods, see also OECD International Standard Problem 47 report r pdf – Investigation of processes inside passive autocatalytic recombiners (PARs) using data from the REKO-3 facility, influence on the containment atmosphere and of steam condensation, hydrogen recombination, effects of steam and oxygen depletion – Investigation of hydrogen combustion using data from the ENACCEF facility, effect of concentration gradients on flame acceleration/deceleration USE OF CFD – CONTAINMENT STUDIES H Wilkening et al. ‚ European Research on Issues concerning Hydrogen Behaviour in Containment within the SARNET Network of Excellence, ICAPP’08, Anaheim, USA, June 2008

SARNET – CFD Workshop, University of Manchester, July USE OF CFD – CONTAINMENT STUDIES H Wilkening et al. ‚ op cit.

SARNET – CFD Workshop, University of Manchester, July SOURCE TERM STUDIES Examples are: – Reactor calculations in combination with other codes such as the LP programs ICARE/CATHARE and ASTEC to determine gas flows and compositions that may result from air ingress into the vessel following hot leg and lower head breach (EdF, IRSN), determining conditions for separate-effect tests on air oxidation of fuel and cladding – Design calculations for facilities investigating the dynamic chemical interactions of iodine- containing and ruthenium-containing species in the primary circuit under severe accident conditions (IRSN, VTT) – Interpretation of circuit chemistry aspects of the Phebus-FPT2 integral in-reactor experiment on core degradation, and fission product release and transport, and behaviour in-containment (IRSN) – Interpretation of an integral ThAI experiment (Becker Technologies) on iodine behaviour in-containment coupled with thermal hydraulic and aerosol aspects, in the frame of a SARNET benchmark led by GRS with contributions from GRS, IRSN and AECL – Investigation of results of the RECI experiments (IRSN) on the effects of PARs on airborne iodine in the containment (IRSN, Demokritos, et al.) USE OF CFD – SOURCE TERM STUDIES

SARNET – CFD Workshop, University of Manchester, July USE OF CFD – SOURCE TERM STUDIES A Auvinen et al. ‚ Progress on Ruthenium Release and Transport under Air Ingress Conditions, ERMSAR2007, FZ Karlsruhe, June 2007 SATURNE calculation of flows in the lower head and cavity under air ingress conditions (EdF)

SARNET – CFD Workshop, University of Manchester, July USE OF CFD – SOURCE TERM STUDIES Illustrations of the ThAI facility

SARNET – CFD Workshop, University of Manchester, July CONCLUDING REMARKS CFD methods have an important role within SARNET for support of experiments, in plant studies and for benchmarking more detailed models, for example in the major European severe accident analysis code ASTEC, that is a main product of the network The focus is on application rather than on development and validation The applications are mainly in the areas of containment studies, and in source term research It is expected that CFD methods will continue to be used in the follow- on SARNET2 project in the 7 th Framework programme, subject to the satisfactory outcome of negotiations with the EC that are currently in progress CONCLUSIONS The authors thank the European Commission for funding SARNET, in the 6 th Framework Programme area “Nuclear Fission: Safety of Existing Nuclear Installations”, under contract number FI6O-CT