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Publicatie Laka-bibliotheek:
Safety consequences of the release of radiation induced stored energy (1994)

Auteur	ECN, Prij
Datum	augustus 1994
Classificatie	6.01.5.51/40 (AFVAL - OPSLAG OP LAND (oa ZOUT/KLEI))
Voorkant

Safety consequences of the release of radiation induced stored energy

ABSTRACT

Due to the disposal of high level waste (HLW) in a salt formation gamma energy will
be deposited in the rock salt. Most of this energy will be converted into heat, whilst
a small part will create defects in the salt crystals. It has been shown that energy is
stored in the damaged crystals. Due to uncertainties in the models and differences
inthe disposal concepts the estimated values for the stored energy range from 10 to
1000 J/g in the most heavily damaged crystals close to the waste containers. The
amount of radiation damage decays exponentially with increasing distance from
the containers and at distances larger than 0.2 m the stored energy can be neglected.
Given the uncertainties in the model predictions and in the possible release
mechanism this report concludes that at this moment an instantaneous release of
stored energy cannot be excluded completely. Therefore the thermo-mechanical
consequences of a postulated instanteous release of an extremely high amount of
radiation induced stored penergy have been estimated. These estimations are based
on the quasi-static solutions for line and point sources. To account for the dynamic
effects and the occurrence of fractures an amplification factor has been derived
from mining experience with explosives. A validation of this amplification factor
has been given using post experimental observations of two nuclear explosions in
a salt formation. For some typical disposal concepts in rock salt the extent of the
fractured zone has been estimated. It appeared that the radial extent of the fractured
zone is limited to 5 m. Given the much larger distance between the individual
boreholes and the distance between the boreholes and the boundary of the salt
formation (more than 100 m), it is concluded that the probability of a release of
radiation induced stored energy creating a pathway for the nuclides from the
containers to the groundwater, is extremely low. The radiological consequences
of a groundwater intrusion scenario induced by this very unprobable pathway are
bounded by the 'standard' groundwater intrusion-extrusion scenario used in the
performance assessment (smaller than 10-8 Sv/a).

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