The components for the present aluminum clad, Al-Si bonded, internally and externally cooled (I & E), uranium fuel elements are composed of impact extruded cans and spire caps as shown in Figure 1. This type of component requires two impact extrusions; however, in December, 1957, J. E. Ruffin proposed another design of component in which there was only one impact extrusion. For this component, Figure 2, the spire was impact extruded as a part of the can.

The large scale application of Zircaloy-2 pressure tubes for structural use either in or out of reactor service, is without precedent. For more common materials, there normally are adequate data and long operating histories on which to base design and service limits. In the absence of such information for Zr-2, several investigative programs have been devised to provide much of the information from which design and service limits may be defined for Zr-2 pressure tubes. These investigations encompass in-and-out-of-reactor creep and stress-rupture testing, pre-and-post irradiation testing, and bust strength, as well as the effect of flaws or defects (from both fabrication and service origins) on burst strength and fracture characteristics. Already creep and stress rupture testing of unirradiated Zircaloy-2 is well advanced, and some experimental pre-irradiation burst testing has been carried out and will be extended rapidly as improved equipment becomes available. One irradiated KER tube sample has been burst tested and the requirement for post irradiation burst testing equipment have been defined.

Over the last decade, several computational methods have been developed and used to examine reactor flow transients caused by pump outage. The variations in system character which have been analyzed are sufficiently diverse that it appears worthwhile to compile them into a single report.