Results from the 1st - 5th interim inspections of coupons and fuel rods from the PWR corrosion and hydriding test IFA-638

In-pile corrosion and hydriding of both conventional and new Zr-based PWR cladding materials are being studied at increased burn-up levels (> 50 MWd/kg U) in IFA-638. The test materials comprise 51 coupons and 12 fuelled cladding segments, of which 6 were in an as-received condition and 6 were pre-irradiated in Swedish power plants and re-fuelled with fresh UO2 pellets. The cladding materials, supplied by ENUSA, Framatome ANP, Kurchatov Institute, MHI and Westinghouse Atom AB, include different types of Zry-4, Zry-2, ZIRLO, Alloy A, E635, E110, M4, M5 and MDA. PWR thermal-hydraulic and water chemistry conditions ( ∼158 bar, ∼310 C, ∼3 ppm lithium, ∼1000 ppm boron, and 2-4 ppm H2) are being simulated by means of an external loop system. Booster fuel rods surrounding the test section create an increased fast flux level. Irradiation of IFA-638 started in July 1998 and five interim inspections, comprising oxide thickness measurements and weighing, have been carried out to date. This report presents the results of the fifth inspection, which was performed after a total of 1001 full power days of irradiation, at an assembly burn-up of 38.3 MWd/kg UO2. Weight gains of the coupons were in the range 70 to 210 mg/dm2. Oxide thicknesses on the pre-irradiated and fresh fuelled claddings were 34 - 77 μm and 15 - 28 μm respectively. (Author)