THE Jules Horowitz Reactor (JHR) [1] is the next Material Testing Reactor under construction in France. It will be a major research infrastructure in Europe to support existing power plant operation and lifetime extension, as well as future reactor developments. Its objectives are to participate to the demonstration of GEN-II vessel behavior for Pressurized Water Reactor lifetime extension, and to test the new structural material and fuel behavior under irradiation for the development of GEN-III and GEN-IV reactors. It also aims at producing a large part of the radioisotope European request.