[en] Channel H12/1 is one part of the channel unit of the High-Flux Reactor that has been affected by corrosion attack. It was disassembled after the appearance of a heavy water leak and examined in a hot cell. Results of the examination are presented

[en] The loss of seal of the H9 channel in vacuum, freeing the entire cross section of the front part, leads to a fast leak that progresses rapidly. The effect of depressurizing the reflector can leads to shutdown of the shutdown rod pumps. The source changer associated with the channel fills completely before the valve closes. All of the leak water remains contained within the source changer containment. After the valves open, cooling of the fuel element is handled by natural convection, requiring a reversal of the flow between the plates. This changeover, which takes place at a relatively low pressure level, could lead to local boiling in the fuel element. Consequently, irreversible transformations cannot be excluded as possibilities for the fuel element and even for the control rod. Subsequently, the can is refilled with heavy water with establishment of the usual pressure levels

[en] Channel failure is an incident that the reactor design takes into account and whose consequences have been studied and accepted during the safety analysis of the facilities. The study of the failure modes (Chapter 3) has shown that the embrittlement of the material due to neutron irradiation does not constitute a fact that could fundamentally change the probability of failure compared to a new reactor. The mechanical properties of the irradiated material in elastic regime are not below the values of the new material. In this respect, the second part of the AG3 NET - HFR test program, whose results are available, does not raise concerns, given the very high mechanical properties of the irradiated material. Consequently, no preventive provisions have to be made, since the irradiated material is compatible with its use as structural material for the channels. The study of the failure modes also demonstrated that mechanical blows applied to irradiated material could lead to destruction because of the reduced plastic deformability. However, this risk only arises when the reactor is shut down during maintenance operations that require access to equipment placed inside the channels

[en] Channel H13/1 is part of the channel unit of the High Flux Reactor characterized by average corrosion attack. Metallography reveal two types of corrosion: in-depth caving corrosion, and surface cracks

[en] The aim of this work is to show the temperature variation of the electrical resistivity, the thermal conductivity and the thermopower in the temperature range from 4.2 K to room temperature of the series (Gdsub(x)Ysub(1-x))Al₂ (0<=x<=1). Additional other physical properties such as magnetisation, suszeptibility and lattice constants are studied in the thesis. In the present work the determination of magnetic scattering processes to thermal conductivity and thermopower is based on a method which has been developed for the electrical resistivity. The idea of this method is to compare the transport properties of magnetic and nonmagnetic isostructurel compounds. For the system under investigation YAl₂ serves as the nonmagnetical isostructurel 'basis'. The subject which has been studied in detail is the influence of spin disorder scattering processes, existing in the paramagnetic temperature range. The temperature dependence of the spin disorder scattering contribution to the electrical resistivity rhosub(spd), the thermal conductivity lambdasub(spd) and the thermopower Ssub(spd) obtained from the experimental result are compared to the theoretical calculations. These calculations are based on the linearised Boltzmann equation which has been solved using the relaxation time approximation. Both the theory and experiment show that rhosub(spd) is temperature independent, whereas lambdasub(spd) and Ssub(spd) are linear in temperature. (Author)

No abstract available

[en] The loss of seal of a helium-filled channel opening the entire cross section of the front part leads to a fast leak. The channel fills to the upper generatrix of the leak orifice and part of the helium contained in the channel escapes into the circuit. The pressure drop in the reflector can lead to reactor and main pump shutdown. On the other hand, the Cooling Circuit Shutdown Bar circuit pumps remain in operation. This paper evaluates the consequences of an incident of this nature for the reactor and the surrounding experimental zones

[en] We have performed a many-body calculation of the longitudinal nuclear (e,e') reaction employing a Second RPA (SRPA) formalism which contains the Δ(1232). More explicitly, our scheme contains RPA correlations as well as Hartree-Fock and second order self-energies, where an accurate evaluation of exchange terms is achieved. Using this formalism we have evaluated the longitudinal response function for ⁴⁰Ca. We give final results at momentum transfers ranging from 300 up to 500 MeV/c, obtaining a good agreement with data

[en] The fission of highly eruiched uranium by thermal neutrons creates dozens of isotopic products. The Isotope and Nuclear Chemistry Group participates in programs that involve analysis of 'fiesh' fission products by beta counting following radiochemical separations. This is a laborious and time-consuming process that can take several days to generate results. Gamma spectroscopy can provide a more immediate path to isolopic activities, however short-lived, high-yield isotopes can swamp a gamma spectrum, making difficult the identification and quantification of isotopes on the wings and valley of the fission yield curve. The gamma spectrum of a sample of newly produced fission products is dominated by the many emissions of a very few high-yield isotopes. Specilkally, ¹³²Te (3.2 d), its daughter, ¹³²I(2 .28 h), ¹⁴⁰Ba (12.75 d), and its daughter ¹⁴⁰La (1.68 d) emit at least 18 gamma rays above 100 keV that are greater than 5% abundance. Additionally, the 1596 keV emission fiom I4'La imposes a Compton background that hinders the detection of isotopes that are neither subject to matrix dependent fractionation nor gaseous or volatile recursors. Some of these isotopes of interest are ¹¹¹Ag, ¹¹⁵Cd, and the rare earths, ¹⁵³Sm, ¹⁵⁴Eu, ¹⁵⁶Eu, and ¹⁶⁰Tb. C-INC has performed an HEU irradiation and also 'cold' carrier analyses by ICP-AES to determine methods for rapid and reliable separations that may be used to detect and quantify low-yield fission products by gamma spectroscopy. Results and progress will be presented.

[en] The GNEP program envisions continuing the use of light-water reactors (LWRs), with the addition of processing the discharged, or spent, LWR fuel to recover actinide and fission product elements, and then recycling the actinide elements in sodium-cooled fast reactors. Previous work has established the relationship between the processing efficiencies of spent LWR fuel, as represented by spent PWR fuel, and the potential increase in repository utilization for the resulting processing waste. The purpose of this current study is to determine a similar relationship for the waste from processing spent fast reactor fuel, and then to examine the wastes from the combination of LWRs and fast reactors as would be deployed with the GNEP approach