He and fission product release from irradiated nuclear fuels: MERARG 2 capabilities

In order to increase fuel rod performance, the basic mechanisms that promote gas (i.e. He, H2, N2, Kr and Xe) release from irradiated nuclear fuel must be studied. The CEA fuel study department at Cadarache decided to improve its experimental facility devoted to fuel behaviour under thermal transient by modifying the existing annealing device, called MERARG (a French acronym for 'Means of Study by Annealing and Analysis of Gaseous Releases'), to extend the studies of fission gases to He. As a result, a micro-gas chromatograph (μ-GC) has been integrated into the MERARG 2 facility. The device can analyse gas concentrations from a few ppm (1.5, 0.9, 3, 2.6 and 5.3 ppm respectively for He, H2, N2, Kr and Xe) up to several thousands of ppm in under two minutes. Regarding the quality of the measurements (limits of detection, fidelity and linearity), the μ-GC is very well adapted to measure the absolute level and the time dependence of all gases released from the fuel during a representative thermal transient. (authors)