[en] Industrial processes for uranium enrichment, economical context and market are briefly reviewed. Then physical principles of the two lasers processes: SILMO (molecular process) and SILVA (atomic process) are presented insisting on criteria for choosing lasers used in the SILVA process which will be developed in France

[en] Hemoglobin occupies an important role as oxygen carrier in the respiratory chain. The autoxydation of oxyhemoglobin (HbO₂) into methemoglobin (HbFesup(III)) could perturb this chain unless the system acts as a source of O₂^- which could facilitate oxydation processes. The reactivity of the HbO₂-HbFesup(III) system with short lived transients (O₂^-, CO₂^-) was studied in order to gain some insigh into this problem. The low reactivity of O₂^- with respect to both HbO₂ and HbFesup(III) shows that the autoxydation of HbO₂ in vivo could act as an O₂^- donor

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[en] The main products formed in the room temperature γ radiolysis of liquid isopropanol, and their respective yields, are: hydrogen 3.8, methane 1.6, acetone 3.4, acetaldehyde 1.1, and pinacol 0.3. These results give a material balance in good agreement with the formula of isopropanol and lead to a value for the yield of decomposition: 5, 3. The absence of butanediol 2.3 shows that the acetaldehyde cannot come from the dismutation of hydroxyethyl radicals. The variations of the hydrogen yield in the neutral medium with the concentration of added electron scavengers may be explained in terms of the model proposed by Freeman and FAYADH which supposes the existence of spurs. The yield of solvated electrons diffusing into the bulk of the solution and also the ratios of rate constants for the reactions of the scavengers with the electrons may likewise be obtained on the basis of this model. Certain effects not foreseen by this model may result from the capture of electrons solvated or not, whose mode of disappearance in pure alcohol remains unknown. One may distinguish a yield of excited molecules of at least 2, of which 80 per cent lead to the production of molecular hydrogen and 20 per cent to that of molecular methane, and an ionization yield of 2. 2. The discussion of the various mechanisms which may lead to the formation of the products indicates that these yields may be higher than the values quoted. (author)

[en] Dimethyl sulfoxide (DMSO) is known to solvate with difficulty anions including the electron and hence the addition of DMSO to a medium increases the anionic reaction rates. An attempt was made to study this effect in mixtures of H₂O--DMSO for specific reactions of the solvated electron using the pulse radiolysis technique. To begin with we chose different solutes among those known as good scavengers of electrons, neutral ones, N₂O, and positive and negative ionic ones (NO₃^- and H⁺). The experiments were carried out with a Febetron delivering 10-nsec pulses of 1.8-MeV electrons. The rate of disappearance of the solvated electron formed by the pulse was measured by direct observation of the decay absorption at 870 or 600 nm. The ultrapure products were used as supplied except for DMSO which was distilled before use

[en] The use of lasers by the electronuclear industry to enrich uranium is discussed, particularly economic aspects. The SILMO and SILVA processes (chosen by France for industrial development) are presented. Criteria which lead to the choice of lasers and to their set-up (architecture of the chain) are described. For electricity - consumption linked to the use of lasers of 40 kWh/STU, a laser uranium enrichment plant with 10 STU/yr capacity requires 50kW of light from copper vapor lasers, i.e., 500 units each having 100W capacity, compared with the 40W units currently marketed

[en] The first objective of research reactors is to produce calibrated beams of neutrons for experiments. However, this emission of neutrons, like the experiment that could bring about interactions with the reactor core, should function in total isolation. In order to avoid all risks of irradiation or contamination of personnel and the environment. These factors have important consequences that affect the design and operation of research reactors because of importance of the sensitivity of public opinion. Centre d'Etudes Nucleaire are often close to urban centres so as to maintain close contact with universities. The cases of CEN-Grenoble, with the reactor SILOE, and of CEN Saclay, with the reactors OSIRIS and ORPHEE, are good examples

[en] This study of the radiolysis of concentrated aqueous LiCl solutions enables the relative contributions of the direct and indirect effects to be evaluated as a function of Cl^- concentration and also permits an evaluation of the role of Cl^- in the early stages of water radiolysis. Radicalar and molecular yields G/sub Cl₂^-/, G/sub OH/, G//sub e//sub aq/^-/ + G/sub H/, G/sub H₂O₂/, and G/sub H₂/ are determined for all concentrations employed, and the material balance is verified. The main conclusions concerning the apparent inefficacy of the direct effect and the importance of OH scavenging in spurs are discussed