The INTER-RAMP programme of work was designed to meet the following main objectives:
- To establish the failure-safe operating limits of 20 standard-type, unpressurized BWR fuel rods on overpower ramping at the burn-up levels of 10 and 20 MWd/kgU. The over-power ramping was to be performed at a fast ramp rate of about 4 kW/m/min with the preceding base irradiation performed with an idealised patterned cyclic variation in power levels designed to represent realistic variations in operating boiling water power reactors.
- To study the influence of three main design parameters on fuel rod performance under power ramping, i.e. clad heat treatment (recrystallised anneal "RX", vs cold work plus stress relief anneal "SR"), pellet/clad diametral gap size, and fuel density.
- To study the failure mechanism and associated phenomena.
- To furnish data suitable for fuel modelling work.
In order to meet these objectives, much effort was expended to record the individual fuel rod power history in great detail and also to determine the fuel rod changes, based on a preirradiation characterisation on a pellet by pellet basis, nondestructive examinations at stages throughout the irradiation history and selective detailed destructive examination of all rods following power ramping.