An Investigation of the Concentration of Chemical Contaminants in a 4 2 MPa Once-Through Boiler Using a Full-Scale Part Model

A scanning gamma-ray detector located deposits of radio-labelled magnetite and sodium and bromine salt contaminants in water fed to an electrically heated serpentine tube replicating one of those in the boilers of Wylfa Nuclear Power Station. Magnetite deposited mainly in the economiser and evaporator initially near the entrance but later spreading further into the boiler. Soluble salts were found mostly in the dryout zone but also in the superheater and, under certain conditions, in parts of the evaporator. Sodium salts were carried through stoichiometrically, but with magnesium salts the anion was carried through in excess. Disodium phosphate added in suitable quantities was found to suppress internal corrosion.