The Studsvik Demo-Ramp-II Project was an internationally sponsored research project designed to investigate the pellet/clad interaction phenomenon during short time power transients. The project included eight fuel rod segments of standard boiling water reactor design, which were operated to burnups ranging from 25 to 29 MWd/kg uranium in a power reactor. The rods were subsequently subjected to power ramp or transient tests in the Studsvik R2 reactor. The failure threshold (where cladding failure and fission product release occur after a sufficient time) was determined from two ramp tests to be ∼40 kW/m for the present rods. The six remaining rods were then subjected to short power transients to heat generation rates up to 48 kW/m. No cladding failures were detected after the transients, by activity release or examination by means of neutron radiography. The unexpected result was, however, that a large number of nonpenetrating (incipient) cladding cracks were formed very rapidly, within a minute. The crack depths, measured by scanning electron microscopy, ranged from 10 to 50% of the cladding wall thickness.