Parametric experiments on the radiolysis of water: Application to the R62 package for the transport of failed PWR fuel assemblies

If failed irradiated fuel assemblies are to be examined rapidly, they must be transported under water. The decay power of the fuel causes radiolysis of the water through the action of the beta and gamma radiation emitted: hence, H2 and H2O2 are formed and molecular hydrogen is released, with the risk of over-pressure and formation of an explosive mixture. The authors performed experiments on water radiolysis, simulating the effects of handling and transport of the package, by circulating water in the Radiolysis loop of the Siloe reactor at the Grenoble Nuclear Studies Centre. The results of these experiments show how the nature of the gas cover affects the formation and release of the hydrogen produced in radiolysis and indicate, in the case of failed fuel, a substantial effect from the dissemination of fission products in the water. In order to test the R62 transport castle designed by the Robatel Company on behalf of Electricite de France, a full-scale water radiolysis test was performed. This experiment, carried out at the Chinon B power plant, has made it possible to characterize the package in relation to hydrogen formation. (author)