Simulation method for secondary hydriding breakage of zirconium alloy cladding

Abstract

BackgroundWhen the fuel zirconium cladding tube of pressurized water reactor (PWR) breaks, the water flowing into the cladding will flash into water vapor under the action of the pressure difference between the inner and outer surface. The inner surface of the tube is damaged due to a large amount of hydrogen absorption, which is known as secondary hydriding embrittlement.PurposeThis study aims to simulate the operating conditions of the first circuit of a PWR and the occurrence of secondary hydrogen embrittlement in zirconium clad tubes.MethodsThrough theoretical strength calculations and thermal engineering verification, a Zirconium alloy clad tube secondary hydrogen embrittlement experimental off-heap simulator was independently designed and implemented. Then the dual heat source simulation experiments ware conducted for ZIRLO alloy clad tube.ResultsUnit operation and experimental results show that unit achieves long-term stable operation at the one-loop condition level, and the inner and outer walls of ZIRLO alloy tubes oxidize and generate hydrides with increasing concentration along the axial direction from the bottom up.ConclusionsThe off-heap simulator device of study solves the impact of thermal delamination in narrow seam space, and can simulate the water loss in primary breach, cooling water flash and interstitial steam corrosion behavior in the secondary hydrogen embrittlement process of the pressurized water reactor cladding tube, which verifies the feasibility of the technical means of the device.

Keywords

• zirconium cladding
• second hydrogen embrittlement
• off-heap simulator
• oxidation
• hydride