Lessons Learned from the Fire Test of Westinghouse’s New Type AF Package, the Traveller: (Nothing like the Real Thing)

Satisfying the thermal test requirements is a significant part of licensing a Type AF package. Regulations allow the thermal test requirements to be satisfied by several means including thermal analysis, thermal test inside a furnace, pool fire test, test using a scale model of the package, test using a segment or portion of a package, or test using a full-scale package. It was decided that a pool fire test using a full-scale package was the only way to adequately test the many features of the Traveller. Items crucial to criticality safety are more subject to damage during the thermal test. The Traveller design includes a substantial amount of neutron moderating material built into the packaging. This is so that criticality safety would not be dependent on moderation by HAC immersion. A full-scale fire test proved to be the only method to verify that the moderator survives. The Traveller also features a unique impact limiter system inside the packaging that is designed to lessen the impact of the contents in an end drop. It was determined that the full-scale fire test would be the only way to verify that the limiters would not ignite and burn inside the package. Actual pool fire temperatures are more severe than the 800ºC minimum required in the regulations. Also it is impossible to model distortions and stresses caused by an actual fire, and these have a significant impact on any thermal analysis. This paper describes the many exploratory and scoping tests that preceded the final fire tes t. The lessons learned, though perhaps not new to those regularly employed in the fire testing profession, proved to be valuable to the licensee in completing the Traveller design.