Revaporisation experiments on aged remnants of a severe nuclear accident using samples from the TMI-2 core.

In the frame of post-Fukushima research, TMI-2 corium samples stored in the ITU Hot Cells were retrieved and re-examined. One experiment consisted of a sequence of three revaporisation tests under different gas atmospheres (steam, hydrogen and air) up to 1000 °C to check their properties after long ageing periods. The samples used for the experiments originate from the TMI-2 core and consist of a fine powder of (U,Zr)O2 ceramic melt with U-rich and Zr-rich phases. Due to the age of the samples the remaining amount of Cs-137 and thus the activity is rather low. During the experiment the samples were heated by 2 K/min from 300 °C to 1000 °C and kept for 1 h at the maximum temperature. The experiments under air and steam did not allow unequivocal measurements of the volatile release due to the distributed nature of the remaining caesium release over the whole temperature range (300°C-1000°C). However, when testing the sample under hydrogen about ~50% of the remaining caesium revaporised about 15 minutes after reaching 1000 °C. In this case, the concentrated release allowed quantitative analysis. The samples will be examined further by Raman spectroscopy and the aerosols generated during the revaporisation will be analysed using TEM and EDX.

KNEBEL Kevin;  BOTTOMLEY Paul;  RONDINELLA Vincenzo;  AUVINEN Ari;  JOKINIEMI J.; 

2016-09-22

SARNET

JRC91834

http://www.sar-net.eu/sites/default/files/ERMSAR_2015/Papers/Source_Term_Issues/064_Knebel_final.pdf,    https://publications.jrc.ec.europa.eu/repository/handle/JRC91834,