Pellet fragmentation studies for the ITER disruption mitigation system

Abstract

The thermal and mechanical loads during disruptions are a major threat for large reactor-class tokamak devices. Therefore, shattered pellet injection (SPI) is selected as the baseline technology for the ITER Disruption Mitigation System (DMS). The aim of DMS Support Laboratory located at the HUN-REN Centre for Energy Research is to study the production, launch and shattering of cryogenic protium, deuterium, and neon pellets in the ITER geometry. This paper reports on the fragment analysis procedure and the first results of the fragment plume investigation performed with pellets made of the above materials and accelerated to a speed ranging between 70 and 500m/s. The experimental results show that the fragment plume consists of macroscopic and microscopic fragments. The shattering of about 500 m/s protium and deuterium pellets resulted in a most common fragment size of a few millimeters, while at lower velocities around 250m/s still the same few millimeters size fragments dominate but larger fragments have a higher proportion in the mass distribution. At low velocities (70 m/s) for neon pellets most of the pellet mass was converted into large fragments (from 10 to 20 mm ). The results are also compared with the Parks pellet fragmentation model.