No abstract available

[en] The phenomena of carburization in the cladding of absorbing elements in fast breeder reactors was studied by the techniques of X-ray microanalysis and micro-hardness. A comparison of the results obtained for different types of pins showed that the intensity and depth of the carburization were closely dependent on the amount of free carbon present in the boron carbide. An assessment was made of the effects of the stresses produced within the cladding. Mechanical properties were in general little affected; however, in the case of the most severely carburized pin a distinct loss of ductility was observed

[en] Gas release is studied in three sodium-joint carbide pins irradiated in the reactor Osiris at a nominal linear power of 900 W/cm to burn-ups ranging from 4 to 13%. The overall activity, stable gases and radioactive gases are measured. It is found that most of the gas is released in busts, that the release of stable gases speeds up sharply after an incubation time, that the initial bursts are very large and that for each mode of release observed and for each class of nuclide the radioactive gases follow a law R/B=A/lambda.n. An attempt is made to interpret the results in terms of either the formation of gas bubbles in the sodium joint, the existence of a large bubble above the fissile column or the simultaneous release of a large number of smaller bubbles

[en] The carburization of fast reactor cladding material may affect its mechanical properties and give rise to severe embrittlement. Carbon profiles were determined by EMPA in various irradiated carburized clads. All clads were in 316 type steels. An effective diffusion coefficient (Dsub(eff)) has been calculated for each profile. The set of Dsub(eff)) is shown in an Arrhenius Diagram. The experimental dispersion on Dsub(eff)) calculated values is due to the non-applicability of the model to a few profiles. The analysis is then made on the remaining Dsub(eff)). These values constitue a good coherent set of points. A comparison is then drawn between this set of points and: - true diffusion coefficient of carbon in the gamma phase, - effective diffusion coefficients of carbon derived from out-of-pile simulation experiments. Activation energy of Dsub(eff) coefficient (in pile and out-of-pile) is small compared too the activation of carbon diffusion in austenite. Dsub(eff) values are quite insensitive to surface concentration in the range 0,9 - 4%. Diffusion time is shown to have a great influence on Dsub(eff): Dsub(eff) decreases as time increases. A Dsub(eff) value for simple evaluations of carburization intensity in irradiated 316 steels is recommended

[en] A doubling time less than or equal to 15 years is possible with the carbide type fuel element in numerous technological configurations. From these results the two references were selected which seemed best suited to French circumstances. In both cases the most critical manufacturing parameter is smear density which must be kept to the highest possible value; swelling and mechanical interaction studies must therefore proceed with this objective in mind. On the other hand, one must not forget that the results obtained in the (most likely optimistic) hypotheses of a 1 year out-of-pile time may need to be questioned in the case of longer out-of-pile times. Nevertheless, at the present moment, the problem of out-of-pile time is not solved for oxide type fuel elements any more than for carbide type elements. Therefore, arbitrary values for this parameter must be chosen for computations. It is important to note that carbide type fuel elements always compare favourably with oxide type fuel elements when out-of-pile times are approximately the same for both fuels. 11 figures

[en] Cladding carburization of fuel elements irradiated in fast reactors, led to the development of a measurement method for the evaluation of carbon concentration with the use of a shielded electron microprobe CAMECA MS 46. In this paper an account is given of: the specimen preparation, the specific conditions of microprobe analysis; choice of standard specimen, localization of measurement, electronic discrimination, background evaluation; the comparison of different carbon distributions obtained in the case of steels irradiated in various conditions; and a quite simple model of unidirectional diffusion. (author)

[en] A new control system for the Safety Linear Accelerator is now being designed. The computer control architecture is based on 3 dedicated VME crates with MC68000 micro-processors: one crate with a disk-based operating system will run the high level application programs and the data base management facilities, another one will manage the man-machine communications and the third one will interface the system to the linac equipments. Communications between the VME microcomputers will be done through 16 bit parallel links. The software is modular and organized in specific layers, the data base is fully distributed. About 90% of the code is written in Fortran

[en] France has a long history of R and D, construction and operation of fast neutron reactors. However, with the shutdown of Superphenix reactor more than 10 years ago and of Phenix in 2009, we are now entering a phase where we must convince that fast neutrons reactors are part of the energy solution for the future, and that they can meet Generation IV requirements. To that purpose, French R and D on fast reactors has been organized for the last 4 years around two systems: sodium cooled fast reactor SFR, as the reference option, and gas cooled fast reactor GFR as long term option. This paper concentrates on SFR R and D and prototype. Along with the R and D, plans for the prototype ASTRID (as for Advanced Sodium Technological Reactor for Industrial Demonstration) have been prepared. As an industrial prototype, it is foreseen to be put into operation around 2020. End of 2009, in a broader investment plan for the future, ASTRID was identified as one of the priorities to receive governmental funding. The ASTRID prototype (as for Advanced Sodium Technological Reactor for Industrial Demonstration) is seen as an industrial prototype prior to the first-of-a-kind, meaning that extrapolability of the technical options and of the safety demonstration is of outmost importance. The reactor will also provide some irradiation capabilities especially in order to validate the expected properties for the new fuel (big pin and ODS clad) and the ability to burn minor actinides up to an industrial scale. The ASTRID program defined by CEA also includes the facility to manufacture the fuel for the reactor, of limited capacity from 5-10 tons heavy metal per year. The refurbishment of existing testing facilities and the construction of new tools is part of the program as well. ASTRID shall be coupled to the grid with an electrical power of about 600 MW. It shall integrate operational feedback of past and current reactors. It is seen as a full Generation IV prototype reactor. Its safety level shall be at least as good as current 3. generation reactors, with strong improvements on core and sodium-related issues. After a learning period, the reactor shall have a high load factor (e.g. 70 to 80%). The reactor shall provide capability for demonstration of transmutation of minor actinides, at larger scale than previously done in Phenix. And of course, the investment costs of the prototype shall be kept to the lowest possible, with technical options compatible with later deployment on a commercial facility. The schedule associated to the ASTRID prototype is very ambitious and will be adapted in the course of the project, following R and D results and political decisions. End of 2009, in a broader investment plan for the future, ASTRID was identified as one of the priorities to receive governmental funding. Although collaborations and partnerships are sought, most of the financing for the design studies is secured (650 M of Euros). (O.M.)

[en] In this article are distinguished different kinds of nuclear fuels for fast reactors: mixed oxides fuels which the plutonium rate between 35 and 45%, the mixed nitrides fuels where the plutonium percentage is between 15 to 85%, fuels without uranium allowing to burn the maximum of plutonium and the targets devoted to the americium transmutation. (N.C.)

[en] France has a long history of R and D, construction and operation of fast neutron reactors. However, with the shutdown of Superphenix reactor more than 10 years ago and of Phenix in 2009, we are now entering a phase where we must convince that fast neutrons reactors are part of the energy solution for the future, and that they can meet Generation IV requirements. To that purpose, French R and D on fast reactors has been organized for the last 4 years around two systems: sodium cooled fast reactor SFR, as the reference option, and gas cooled fast reactor GFR as long term option. This paper concentrates on SFR R and D and prototype