[en] The ISIS reactor, mock-up of the OSIRIS reactor at Saclay, is presented. After a brief description of the facility, emphasis is put on the use of the core as a neutron mock-up for studying reactor cores and dosimetry and as a neutron source for neutron-graphy. The validity of the results obtained and the difficulties lying in their interpretation are discussed

[en] The Saclay Nuclear Research Center is provided with an original gamma spectrometry facility located inside the pool of the Osiris reactor. It is intended for the gamma scanning of fuel elements irradiated in Osiris or elements of any other origin. The principal characteristics of this facility are given. Special emphasis is put on its

[en] A plate type nuclear fuel (Caramel fuel) has been developed in France in the framework of the various activities pursued in the design, fabrication and development of nuclear fuels by the CEA. This fuel can be adapted to various different categories of water cooled reactor (power reactors, marine propulsion reactors, urbain heating reactors, research reactors). The successful work conducted in this field led the realization of a complete core and reloads for the high performance research reactor, Osiris, at Saclay. The existing highly enriched U-Al alloy fuel was replaced by a non-proliferating low enrichment (7%) caramel fuel. This new core has been operating successfully since january 1980. A brief description of Caramel and its main advantages is given. The way in which it is fabricated is described together with the quality controls to which it is subjected. The qualification program and the main results deduced from it are also presented. The program used to monitor its in-pile behavior is described. The essential purpose of this program is to ensure the high performance of the fuel under irradiation. The successful operation of Osiris, which terminated 11 irradiation cycles on the 21st of April 1981 confirmed the correctness of the decisions made and the excellent performance that could be achieved with these fuel elements under the severe conditions encountered in a high performance research reactor

[en] Gamma scanning enable direct, rapid, non destructive experiment analysis about nuclear fuel. French experimental reactors are provided with gamma spectrometry facilities of which various designs are described. Evolution of a large number of fission products can be followed in space and over time, along the fuel life. So, an understanding in temperatures, changes in structure and behavior of the fuel and its cladding is obtained. Quantitative dosimetry allows to know operating power and burn-up. Such considerations prove well adapted to present requirements as concern reactor safety and fuel management and power reactors are being equipped with

[en] The French irradiation program for the steels of reactor vessels is outlined. A method of measurement of the damage fluence for this type of irradiations is exposed, from the preliminary dosimetry to the integrated counting involved in an experiment. The direct method using damage detectors is mentioned

[en] One of the various activities carried out in France concerned with the design, fabrication and development of nuclear fuels was the development by the CEA of a plate type fuel (Caramel fuel). A Caramel fuel element is in the form of a plate consisting of two tight covering zircaloy sheets in which the UO₂ platelets are confined themselves within the network of a zircaloy grid. The plane geometry provides an effective means of overcoming the drawback of poor uranium oxide conductivity, and makes it possible to combine high specific power with low fuel temperature. The chief advantages of this fuel are the following: it is a very low enriched fuel. It can be used in research reactors demanding high volumetric powers and neutron fluxes, with a required enrichment significantly lower than 20% ²³⁵U. The difference between the densities of UO₂ matrix and U-Al, 10.3 and 1.6 g/cm respectively, leads to a higher uranium charge, making it possible to reduce the enrichment to between 3 and 10%. Owing to fuel dispersion, any loss of tightness only puts a small amount of fissile material in contact with the coolant, thus limiting any contamination of the primary circuit. Another safety factor is the operating temperature, which is considerably lower than the temperature at which fission gases are liberated

[en] The fuel is composed of thin plates assembled parallel to each other to form bundles or assemblies. Each plate is composed of a pavement of uranium oxide pellets, insulated from each other by a zircaloy cladding. The ²³⁵U enrichment does not exceed 8%. The range of uses for this fuel extends from electric power generating reactors to irradiation reactors for research work. A parametric study in test loops has made it possible to determine the operating limits of this thick fuel, without bursting. The resulting diagram gives the permissible power densities, with and without cycling for specific burn-ups beyond 50,000 MWd/t. The thinnest plates were also irradiated in total in the form of advance assemblies irradiated in the core of the OSIRIS pile prior to its transformation. This transformation and the operation of this reactor with a core of 'Caramel' elements is the main trial experiment of this fuel