Title: Physical and Metallurgical Phenomena During Simulations of Plasma Disruption
Authors: SCHILLER PeterCAMBINI MarioBROSSA FrancescoRIGON Giordano
Citation: J. of Nuclear Materials vol. 155-157 p. 412-416
Publication Year: 1988
JRC N°: JRC5242
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC5242
Type: Contributions to Conferences
Abstract: IT IS EXPECTED THAT DURING PLASMA DISRUPTIONS THE FIRST WALL OF A TOKAMAK REACTOR WILL BE EXPOSED TO EXTREMELY HIGH HEAT FLUXES. BY CALCULATIONS, IT HAS BEEN SHOWN THAT SURFACE MELTING AND EVAPORATION WILL TAKE PLACE. SIMULA- TION EXPERIMENTS HAVE BEEN EXECUTED BY THE MEANS OF ELECTRON GUNS, AS THEY ARE USED IN WELDING EQUIPMENTS, IN ORDER TO VERIFY THE RESULTS OF THE CALCULATIONS AND IN ORDER TO STUDY THE OTHER PHYSICAL AND METALLURGICAL PHENOMENA LINKED TO THE DISRUPTION, WHICH MAY BE IMPORTANT FOR THE EVALUATION OF THE LIFETIME OF THE FIRST WALL. ANALYTICAL AND NUMERICAL SOLUTIONS HAVE BEEN DEVELOPED FOR CAL-CULATING MELT DEPTH AS A FUNCTION OF THE MATERIAL CHARACTERISTICS AND PLASMA DISRUPTION PARAMETERS, TAKING INTO ACCOUNT THE FORCED CONVECTION IN THE MELT ZONZONE. THE METALLOGRAPHIC ANALYSIS EXECUTED ON AUSTENITIC STAINLESS STEEL SPE- CIMENS SUBJECTED TO SIMULATED PLASMA DISRUPTIONS ALLOW TO PRESENT A COMPLETE PICTURE OF THE MOST IMPORTANT PHENOMENA. I) THE EXPERIMENTS SHOW THAT FOR THE CALCULATION OF MELT LAYER AND EVAPORATION IT IS NECESSARY TO TAKE CONSIDERABLE CONVECTION IN THE MELT LAYER INTO ACCOUNT. II) THE RAPID SOLIDIFICATION OF THE MELT LAYER LEADS TO A CHANGE IN THE CRYSTALLINE STRUCTURE AND TO THE FORMATION OF CRACKS. III) ALLOYING ELEMENTS WITH A HIGH VAPOUR PRESSURE EVAPORATE PREFE- RENTIALLY. IV) THE STRESSES GENERATED DURING COOLING INDUCE SOMETIMES PHASE CHANGES. V) DURING NEUTRON IRRADIATION HELIUM IS FORMED IN ALL FIRST WALL MATE-RIALS BY (ETA=ALPHA) PROCESSES. THIS HELIUM FORMS BUBBLES UNDER DISRUPTIONS. VI) THE FERROMAGNETISM FOUND IN DROPLETS AND STRUCTURAL MATERIAL OF THE LIMI- TER HAS BEEN CONFIRMED AND EXPLAINED IN LABORATORY TESTS. THE MAGNETISM WAS EXPLAINED BY MICROSEGREGATION AND THE FORMATION OF FERRITE DURING RAPID COOLING
JRC Institute:Joint Research Centre Historical Collection

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