Measurement and preliminary analysis on transient cladding deformation during reactivity initiated accident conditions

The transient cladding deformation measurement tests have been performed under reactivity initiated accident (RIA) conditions in the Nuclear Safety Research Reactor (NSRR). A single PWR type fuel rod which was instrumented with strain gage was contained within a capsule filled with water at ambient temperature and atmospheric pressure, and heated up by pulsing operation of the NSRR simulating an RIA. Transient diametral deformation of the cladding tube due to Pellet-Cladding Mechanical Interaction (PCMI) was successfully measured using strain gage. It was revealed through the experiments that strain gage designed for the use in steel could be applied for the measurement of transient PCMI behavior of zircaloy cladding tube if appropriate correction on temperature compensation of the strain gage was made. Data obtained by the strain gage are quite valuable for the verification of the fuel rod deformation model in the fuel behavior analysis code. Preliminary analysis showed that pellet deformation model of GAPCON-THERMAL-1 code gave good prediction on the fuel rod deformation under an RIA transient. (author)