Investigations concerning the safety of the assembly SNEAK 9B with consideration of assembly bowing

The reactivity feedback due to assembly bowing during an excursion has been estimated for the SNEAK-9B assembly. The maximum possible reactivity effect caused by complete closure of all gaps between assemblies amounts to +1.7 $. The total temperature coefficient at operational temperature is positive, so that any positive reactivity insertion without activation of a shutdown system would most probably lead to core temperatures of more than 800 deg C at which the integrity of the sodium platelets would no more be guaranteed. The positive bowing effect could be avoided by a fixation of the assembly tubes in core midplane