OECD CABRI Waterloop Project: experiments on the high burn-up behaviour of fuel rods in case of rapid reactivity incidents were carried out on the CABRI research reactor in Cadarache, France. These incidents occur when the reactor briefly becomes over-critical due to the rapid, uncontrolled movement of a control element or control rod.
The project is based on the Prometra test programme, which examines the mechanical behaviour of irradiated cladding tube specimens at the high elongation rates that are typical of RIAs (Reactivity Initiated Accidents). The main work in 2009 comprised:
- The conversion of the core structure (required for the changeover from sodium to water cooling) was completed, including the necessary tests. Advance calculations for several planned CABRI-RIA experiments were carried out.
- Several mechanical elongation tests on irradiated Zr-4 cladding tubes were carried out at various temperatures. Apart from the temperature, the deformation behaviour also depends on the thickness of the outer layer with deposited hydrides.
- At the PSI, measurements were taken regarding the distribution of hydride deposits in BWR Prometra specimens. For a cladding tube segment from the Leibstadt nuclear power plant, the measured values ranged from 4.7 % to 16.8 %.