CANDU 600 Reactor Response to Localized Perturbations Such as Channel Fuelling

Abstract

The response of a CANDU-6 reactor core to the refuelling of FAF and FARE channels is described, based on data collected recently at Point Lepreau. A new data-logger system which can monitor - all SDS1 and SDS2 trip parameters, was used to supplement the traditional data-acquisition sources (reactor regulation data from DCCX). In addition some historical data collected by the site fuelling engineer, and meant to be used by Operators, is included, Of interest is both: (a) the response of key parameters such as coolant temperature and pressure; neutron flux at detectors; channel power and flow; global flux tilts; and (b) the response of reactivity control devices such as liquid zone controllers and flux-mapping. Four channels were monitored: K13, K17, P11, Q03. The responses were correlated to the actual position of the fuel string by stoppinq fuel string movement at specified points, long enough for data to be collected. Only Q03 was a flow-instrumented channel. This was also the FARE channel. Channel exit RTD response provides an indication of flow variation otherwise globally and in the subject channel, during the fuelling sequence. This paper begins a process of analyzing a number of long- standing operational concerns, listed in the paper. Some preliminary assessment of these questions are presented here - however, the objective is to provide a data-base to Analysts and designers, structured to help them understand these operational problems. The description of changes to ROPT parameters is meant to help the site Safety Analysis group address questions about ROP coverage during fuelling, and begin to define impairment levels for trip confidence.