Electrochemical model of activity transport in pressurized water reactors

Activity transport in Pressurized Water Reactors (PWRs) is a major concern with respect to both safety and plant operation. The well-known cause of activity transport is the activation of isotopes found in the primary coolant as a result of corrosion of the construction materials. The precursors of the activated isotopes are those found in the alloys used to construct the plant, which once dissolved into the water are also known as Chalk River Unidentified Deposits (CRUD). The modeling of activity transport, in this work, is based on the movement of CRUD throughout the primary coolant loop. A model has been developed that calculates the activity levels at points around a typical PWR primary coolant loop. The solubilities of many CRUD species likely to be in the primary coolant of a PWR are calculated as a function of electrochemical properties. These solubilities are used to determine the rate of release of CRUD products into the coolant and to determine if dissolution or precipitation is occurring. Activation rates of the isotopes as they travel through the core are calculated. This model allows for the calculation of the number of activated isotopes deposited at a given loop position, thus giving the accumulated activity at that point. (authors)