Grant: NSERC/NRCan/AECL Generation IV Energy Technologies Program

The long-term viability of the SCWR will be determined in part by the stability of the materials that will contact the coolant. Experience with existing reactors has shown that corrosion, fuel fouling and activity transport can be minimized if the chemistry of the coolant in the Heat Transport System (HTS) is controlled within optimal limits. Thus, to ensure the components achieve their design life, it is necessary to monitor and control the important chemical parameters, such as electrical conductivity, pH, oxidation-reduction potential (ORP), concentrations of dissolved ions and of redox species and particulate content. Many of the methods used to monitor these parameters for existing reactors are not appropriate for SCW applications, mainly because of the significant change in physical properties associated with the phase change. Existing methods are generally ex-situ. Small 'grab' samples are taken from the coolant and chemically analyzed 'off-line' at room temperature and atmospheric pressure. Unfortunately, the results of these analyses can vary with sampling location, and some properties, such as dissolved oxygen, cannot be reliably measured because of reactions with the sampling systems. These problems are expected to be worse for SCWR conditions. It is not obvious how knowledge of the chemistry of grab samples analyzed at room temperature and pressure can be usefully extrapolated to SCW conditions, where things like solubility, density, viscosity and dielectric constant can change by orders of magnitude. Thus, it is expected that key chemistry parameters for the SCWR will have to be monitored with in-situ on-line sensors. The proposed project would start with a review of chemistry sensors for existing and SCW reactor applications, and provide recommendations for future developments. This would be followed by further research into the most promising sensors, and would include designing, building and testing of new and improved models in the SCW loops at UBC, which will be modified to operate under proposed SCWR conditions. The proposed work will involve collaboration between UBC and AECL for a period of 3 years.