Evaluation of the effect of ion exchange resin on feeder integrity

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Point Lepreau Nuclear Generating Station (PLNGS) has installed an online hydrogen effusion monitor (HEPro from CNER at UNB) on an outlet feeder to monitor the hydrogen permeation rate and hence the rate of feeder thinning. Initial results have shown that the general corrosion rate of the higher chromium feeders installed during the refurbishment outage is significantly lower than the previously installed low chromium pipes. Monitoring the rate of hydrogen effusion has shown that the probe is sensitive to chemistry changes in the primary heat transport system (e.g. the introduction of low concentrations of dissolved oxygen during fueling). One of these recent observations was a significant increase (more than double) in the hydrogen effusion rate following the installation of a fresh, lithiated IX resin bed in the PHT purification circuit. The observation suggests that the feeder thinning rate changed significantly due to this chemistry change. The elevated corrosion rate (still much lower than pre-refurbishment) persisted for a month, until a planned outage and resumed at the higher rate following plant restart but has since been decreasing. Preliminary calculations suggest that the fresh ion exchange resin is removing iron from solution at a fast enough rate to significantly influence the degree of under-saturation at the core outlet and hence change the flow accelerated corrosion rate. The objective of this project is to evaluate the influence of current ion exchange resin practices on feeder integrity and to determine if the resin mixtures in use can be optimized to lower the amount of iron being removed from solution while meeting activity transport requirements. The scope includes a full analysis of the PLNGS HEPro data (2006 - present) to evaluate the link between ion exchange resin practices and FAC rates. A secondary aspect of this work will further evaluate the absorption characteristics of ion exchange resins for iron species and for film forming amines that may be used as additives to the station's secondary system.