Analysis and prevention of corrosion in To chopper systems

To neutron choppers at Oak Ridge National Laboratory's Spallation Neutron Source will stop prompt pulses of high-energy neutrons outside the target moderator. Choppers are cooled internally by recirculated distilled water maintained at 15 °C. Numerous metallic components are used to fabricate the choppers and cooling system; water contacts many of these components, establishing a corrosion cell. To chopper system corrosion products were investigated analytically. Results showed elevated concentrations of soluble and precipitated iron and copper in cooling water. A chemical-based corrosion strategy was implemented in a To chopper system during mechanical tests not involving system irradiation. Chemical analyses showed that a chemical corrosion inhibitor stopped system corrosion for 6 months after its introduction. Corrosion cessation was beneficial, as mechanical tests were performed without interruption from precipitate wear on mechanical parts, flowmeter blockage, or a decrease in heat transfer capabilities. Aqueous chemical changes occurring in the cooling system upon inhibitor addition are discussed.