The IAEA coordinated research programme concerning DHC cracks measurements on zircaloy sheaths

Full text: A mechanism of flaw extension called Delayed Hydride Cracking (DHC) has been implicated in the failure of zirconium based alloys, operating in the nuclear reactors as structural materials like Zr-2.5Nb in pressure tubes or zircaloy-2 and 4 used as fuel cladding. Both theoretical and experimental studies have been performed to investigate DHC phenomenon, to assess the structural integrity of these alloys, IAEA-Vienna being the co-ordinator of the Coordinated Research Program (CRP). Based on consistent and reproducible results obtained at the First CRP on CANDU and RMBK pressure tubes, IAEA initiated a new program in 2005, which will adopt the approach of technology transfer from the host laboratory, Studsvik AB, to the participating Institutes. The aim of this research is to develop a reproducible measurement procedure of Delayed Hydride Cracking Velocity (DHCV) in Zirconium alloy cladding tubes, using the Pin Loading Test (PLT) technique. This paper outlines the benefits for the participation of the Institute for Nuclear Research (INR) in the CRP. INR has developed a consistent and reliable testing method for DHC crack measurements on PWR zirconium alloy cladding and, as a CANDU reactor owner, has extended the testing procedure to PHWR materials. (authors)