EUROTRANS – DM1 ENEA Activities on EFIT Safety Analysis ENEA – FIS/NUC Bologna - Italy WP5.1 Progress Meeting Tractebel / Brussels, March 17, 2006 G. Bandini, P. Meloni, M. Polidori

OUTLINE Planned Activities on EFIT Safety Analysis Transient Analysis with RELAP5/PARCS Use of SIMMER-III in MEGAPIE Safety Study and DM4 - DEMETRA SGTR Analysis with SIMMER-III Preliminary SIMMER-III Results

ENEA Activities on EFIT Safety Analysis Analysis of DBC and DEC transients with RELAP5/ PARCS coupled code Analysis of the SGTR and water-lead interaction with SIMMER-III code

Transient Analysis with RELAP5/PARCS Planned Approach Capability to treat global system behavior coupled with dynamic core response in transient conditions Investigation of whole spectrum of accidental DBC scenarios and DEC conditions (no severe accidents) Main differences respect to PDS-XADS to address code upgrading and activity planning: Lead instead of LBE as coolant Large positive reactivity potentials without prompt Doppler Preliminary investigation of safety issues to support core design

Transient Analysis with RELAP5/PARCS Completed and in Progress Activity Inplementation of Lead thermodynamics and physics properties in the last RELAP version MOD3.3 (capable to be coupled with most recent PARCS versions) Modification of v2.4 PARCS version to treat external source (hexagonal geometry, multi-group energy description) First coupled calculations and modelling of EFIT core (preliminary design) in progress

Use of SIMMER-III in MEGAPIE Safety Study Calculations of LBE-Water Interaction Accident for MEGAPIE Comparison with FZK calculation with MATTINA code SIMMER-IIIMATTINA

Validation of SIMMER-III on JAERI Experiments LBE-Water Interaction Test SIMMER-III and Test result comparison (vapor volume)

Use of SIMMER-III in DM4-DEMETRA Lead-Water interaction experiments will be performed in the Facilities (LIFUS and/or CIRCE) of ENEA/Brasimone site SIMMER-III code will be used in pre- and post-test analysis of these experiments Qualification of SIMMER-III models in connection with these experiments is proposed by ENEA in close cooperation with the University of Pise Based on the results of this work and eventual code model limits some model development work could be envisaged and proposed ENEA asks for the agreement by the SIMMER-III development team (JNC, FZK and CEA) to perform this task in close cooperation with the University of Pise (under responsibility of ENEA)

Analysis SGTR Accident in EFIT Preliminary SIMMER-III Calculations Use of a simplified 2-D cylindrical geometry Boundary conditions according to EFIT ANSALDO design Stagnant lead inside the vessel Lead  liquid fuel, Water  coolant in SIMMER-III lead-water interaction simulation 1 to 5 steam generator tube rupture

EFIT Design SIMMER-III Modelling Simplified R-Z Geometry (29 x 41) R Z

SGTR Accident in EFIT Simplified Assumptions in SIMMER-III Calculations Reactor Vessel Lead mass = 1850 tons (LBE properties with T melting = 328 °C) Lead temperature = 400 °C Cover gas volume = 41 m 3 (T = 400 °C, P = 1 Bar) Steam Generator Tube inside diameter = 14.2 mm Liquid mass = 31.1 kg; steam mass = 25.3 kg Volume = 0.32 m 3 ; void fraction = 84.7% Pressure = 140 Bar; Temperature = 335 °C Tube Rupture (1 and 5 SG tubes) Downwards flow at the heat hexchanger bottom Mass flowrate (1 tube) = 1.2 – 1.6 kg/s (steam and liquid mixture)

SG Break Mass Flowrate

Material Fractions 1 Tube Rupture Time = 0 – 30 s 0.1 s 1 s 3 s10 s 30 s

Material Fractions 5 Tubes Rupture Time = 0 – 30 s 0.1 s 1 s 3 s10 s 30 s

System Pressure 1 Tube Rupture t = 30 s

System Pressure 5 Tubes Rupture t = 30 s

1 to 5 SG Tube Rupture Comparison s

Main Conclusions from SGTR Analysis More suitable geometry must be chosen to model the SGTR in EFIT reactor with the SIMMER code (2-D or 3-D ?) Boundary conditions are still uncertain Preliminary calculations show that steam explosion effects are not of concern in the SIMMER-III evaluation Fast vapour expansion outside the break causes a significant movement of lead mass that impacts onto the vessel upper structures An almost linear increase of the cover gas pressure is computed by SIMMER-III in the time frame of tens of seconds