Structure of Helium Loaded Stainless Steel after Short Heat Pulses

IN PRESENT DAYS TOKAMAKS PLASMA DISRUPTIONS OCCUR FREQUENTLY. THE NEXT GENERATION MACHINES WILL, THEREFORE, HAVE TO BE DESIGNED TO SURVIVE A CONSIDERABLE NUMBER OF DISRUPTIONS DURING THEIR LIFETIME /1/. SINCE THE DAMAGE TO THE FIRST WALL DUE TO DISRUPTIONS IS EXPECTED TO INCREASE WITH THE SIZE OF THE MACHINES, THESE PHENOMENA ARE OF MAJOR CONCERN FOR THE CONSTRUCTION OF THE INTOR/NET TYPE. DURING PLASMA DISRUPTIONS LARGE AMOUNTS OF ENERGY (1-20 MJ M-2) ARE DUMPED IN SHORT TIMES (1-20 MS) TO PARTS OF THE FIRST WALL. AS A CONSEQUENCE, THE SURFACE TEMPERATURE OF THE WALL MAY REACH VALUES IN THE RANGE OF 1500-3000 DEGREES C. IN THE CASE OF METALLIC FIRST WALLS, SURFACE MELTING AND EVAPORATION MAY DAMAGE THE STRUCTURE. DUE TO THE INTERACTION OF THE HIGH ENERGY NEUTRONS WHICH ARE GENERATED IN THE BURNING PLASMA WITH THE ATOMS OF THE WALL MATERIAL, SUBSTANTIAL AMOUNTS OF HELIUM WILL BE GENERATED BY (N,ALPHA) REACTIONS. THIS HELIUM WILL BE RANDOMLY DISTRIBUTED IN THE WALL MATERIAL AND WILL BECOME MOBILE ONLY AT HIGH TEMPERATURE. IN THIS PAPER SOME RESULTS WILL BE REPORTED ON THE BEHAVIOUR OF THE HELIUM CONTAINED IN STEEL IN THE CASE OF DISRUPTIONS.

SCHILLER Peter;  CAMBINI Mario;  BROSSA Francesco; 

1995-03-15

JRC4755