OECD Halden Reactor Project, Fuel and Material Behaviour Section: over 130 scientific, official and industrial organisations from 19 countries participate in the OECD’s Halden Reactor Project (HRP). The focus is on two areas: fuel and material behaviour, as well as Man-Technology Organisation (MTO). In the area of fuel and material behaviour, the current emphasis is on the high burn-up of fuels in light water reactors and the influence of radiation, water chemistry and mechanical and thermal stresses on material ageing in core internals. The MTO area is described in the section on “People, organisation and safety culture”.
In the year under report, twelve experimental nuclear fuel configurations were irradiated with low to high burn-up in order to simulate the thermohydraulic conditions in light water reactors. Key variables for the ceramic fuels, initially uranium oxides with various additives, were determined under operational and incident conditions. Comparative exposures were also used to examine the fuel rod cladding tubes in order to determine corrosion and deposits on the outside of the cladding tubes.
The experiments on high burn-up fuels from commercial reactors were continued under conditions such as those occurring in case of a coolant loss incident. Two tests were carried out in each case on fuels for pressurised and boiling water reactors (PWR and BWR, respectively). In particular, the two fuel samples from the Leibstadt nuclear power plant yielded interesting results regarding the release of gas from the fuel, and in respect of cladding tube elongation and fuel swelling.
An experiment was completed on the release of fission gas from uranium oxide fuels with additives at high linear rod power, and follow-up studies are in progress. A new experiment is being prepared on the release of fission gas with additive fuel. The inert matrix fuel experiment (for which the Paul Scherrer Institute (PSI) produced the fuel) was removed from the Halden reactor and the investigations in the hot cells were completed.
Experiments with reactor materials focus initially on radiation-induced stress corrosion cracking in normal and reducing water chemistry. Interesting results were obtained regarding radiation-induced changes to the properties of the stainless steels in reactor structures. Experimental proof was obtained of the favourable influence of reducing water chemistry on crack growth under the influence of irradiation.