[en] The IFA-533.2 experiment represents the first in-reactor test of pre-irradiated fuel rods with fuel thermocouples. It has been irradiated in the HBWR since March 1992. The rig contains BWR-type fuel rods, pre-irradiated in IFA-409 to an average burnup of about 44 MWd/kgUO₂, and then re-instrumented with fresh fuel thermocouples. This report presents an evaluation of the results in steady-state and transient operation to a burn-up of 70 MWd/kgUO₂. The data can be interpreted in terms of fuel conductivity degradation, gap conductance, and fission gas release. The results from the steady-state fuel temperature studies are summarized as follows: 1. For burnups from 43 to 50 MWd/kgUO₂, the temperatures at constant power showed an increasing trend. This is interpreted as fission gas release into the still open gap as the dominant factor. 2. For burnups > 50 MWd/kgUO₂, the isopower temperatures remained essentially constant, indicating that the effects of conductivity degradation, gap closure and continued fission gas release appear to balance each other. The transient temperature behaviour was investigated by measuring fuel centre temperature changes following reactor scrams. The trend in fuel rod dynamic response showed a continuous increase in the time constant until a burnup of 63 MWd/kgUO₂, and thereafter a slight decrease. (author)