Status of the MeLoDIE experiment, an advanced device for online biaxial study of the irradiation creep of LWR cladding

As a prototype of future instrumented material experiments in the Jules Horowitz Reactor (JHR), the MELODIE project was launched in 2009 by the CEA in collaboration with VTT. Being designed as a biaxial creep experiment with online capability, MELODIE is able to apply an online-controlled biaxial loading on a LWR clad sample up to 120 MPa and to perform an online measurement of its biaxial deformation. An important experimental challenge was to perform reliably accurate measurements under the high nuclear heat load of incore locations while keeping within their tight space. For that purpose, specific sensors were co-designed with and built by IFE Halden. MELODIE in-pile section is now manufactured and initial tests of the on-board instrumentation will be presented. The initial goal of an accuracy of 1 μm rms was recently achieved in the lab for the diameter gauge. Out-of-pile section includes a glovebox with a recirculating helium loop and a digitally-controlled pressurization system. This part is now close to be delivered and its specifications will be reviewed. Extensive pre-irradiation tests at room temperature and close to nominal temperature after final assembly of the complete setup are planned in the next months for final assessment of the design. Safety requirements for an in-core experiment involving NaK as the static coolant are very high. These requirements had also a strong impact on design and timeline of MELODIE. MELODIE project is now close to completion and irradiation in the OSIRIS reactor, in Saclay, should start by end of this year.