P22 Investigation of the activity release from HTR fuel element spheres during storage

For the disposal of spherical HTR fuel elements,

two approaches are envisaged:

- intermediate storage in steel barrels containing 1000 or 2000 spheres each (dry storage) and subsequent refabrication or

- storage of the integer fuel spheres contained in steel barrels in a salt deposit (possibly final storage).

For both possibilities predictions must be made about the long-time behaviour of the fuel elements under storage conditions, particularly about the release of activity.

1. The pebble-temperature in a dry storage will not exceed 140°C, even not in an accident, e.g. most of the fission products are not volatile and will not be released with the exception of the long lived gases Kr 85 and H 3. /1,2,3/