[en] Directly involved in the development of civil and military atomic programmes, the author, Denis Breton, relates the different steps of his nuclear career, from Zoe, the first French nuclear reactor with a null power to the birth of the french h bomb. (N.C.)

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[en] The displacement of a control plate leads to a corresponding variation in the multiplication factor. Measurements were done, by an oscillation method, on the anti-reactivity of a control plate in the pile Zoe as a function of its height. The plate was made to oscillate with small amplitude around a given position, and the value of the modulation of neutron density was measured. From this absolute values of the differential variation of reactivity for each mean oscillation position could be deduced directly from the kinetic equations. The curve of the differential effect as a function of the height, graphically integrated, gives the overall effect of anti-reactivity of the plate. The variation of this curve with the heavy water level is then studied. (authors)

[en] Among the possibilities for replacing snubbers in seismic design of pipes, installation of damping systems (viscous energy absorbers or other techno-logical systems, modelled as perfectly viscous in the present study) can be considered. A difficulty then arises in design process: Eigenmodes of the pipe are classically assumed to be ''uncoupled'' (classical damping); it is not longer true with located viscosities that create a non classical damping (coupled eigen-modes). This paper deals with the use of methods of classical damping in this situation of non classical damping

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[en] The temperatures needed to produce thermonuclear reactions are of the order of several million degrees Kelvin. Devising methods for measuring such temperatures has been the subject of research in many countries. In order to present the problem clearly and to demonstrate its importance, the author reviews the various conditions which must be fulfilled in order that reactions may be qualified as thermonuclear. The relationship between the temperature and the cross-section of the reactions is studied, and it is shown that the notion of temperature in the plasmas is complex, which leads to a consideration of the temperature of the ions and that of the electrons. None of the methods for the temperature measurements is completely satisfactory because of the hypotheses which must be made, and which are seldom fulfilled during high-intensity discharges in the plasmas. In practice it is necessary to use several methods simultaneously. (author)

[en] During the running of a reactor which uses water as a neutron moderator, a bluish light is seen to appear inside the liquid. A detailed study of this radiation, undertaken on the Fontenay-aux-Roses pile, has shown that the spectrum is identical with that which characterises the light produced by the Cerenkov effect. The light intensity as a function of the pile power grows exponentially as a function of time when the pile diverges, with a lifetime equal to that of the rise in power. An examination of the various particles present in the pile has led to the conclusion that only electrons with an energy greater than 260 keV con produce the Cerenkov light. The light source thus produced is about 2.10⁶ photons/cm² of water, when the pile power equals 1 watt. (author)

[en] Nuclear controls has for aim to determine the validity of materials intended to be used for the construction of the reactor core. The cross-section of capture of these materials has to be measured while comparing them either to a standard of the same material, either to an element of cross-section supposed known. We studied the disruption of the working of the reactor generated by the periodic introduction of a sample of the studied material. This method is based on the measure of the phase angle of the signal provided by the ionization chamber. This signal results from the composition of a local signal and an aggregate signal due to the effects of diffusion and capture. This method permits the comparison of the capture of 2 samples very dispersive and few capturing as the graphite, the beryllium, the beryllium oxide, with a good precision. It permits to determine the cross-section of capture of elements as magnesium or aluminum. (M.B.)

[en] A major objective of this study was to identify potential safety questions for laser controlled thermonuclear reactors. From the safety viewpoint, it does not appear that the actual laser controlled thermonuclear reactor conceptual designs present hazards very different than those of magnetically confined fusion reactors. Some aspects seem beneficial, such as small lithium inventories, and the absence of cryogenic devices, while other aspects are new, for example the explosion of pressure vessels and laser hazards themselves. Major aspects considered in this report include: (a) general safety considerations, (b) tritium inventories, (c) system behavior during loss of flow accidents, and (d) safety considerations of laser related penetrations