[en] Electron microscopy has made extraordinary progress over the past 30 years and has become an indispensible tool for research in materials science. In this paper a review is given of some applications of microdiffraction and microanalysis in our current materials science research projects at the University of California, Berkeley. The topics discussed include: (1) The problem of solute atom partitioning in steels; this includes the difficulties of measuring carbon contents and methods of utilizing diffraction, lattice imaging, energy dispersive x-ray (EDXS) and electron energy loss (EELS) spectroscopies and atom probe analysis will be illustrated. (2) Utilization of CBED and EDXS techniques in zirconia ceramics research. (3) Applications of CBED to the study of γ-Fe₂O₃ particles used in magnetic recording systems. (4) Applications of CBED and EDXS to rare earth permanent magnets. (5) Channelling enhanced microanalysis. 50 refs., 21 figs

[en] India's long-term nuclear power aspirations are dependent upon fast breeder reactor technology due to the nature of the country's fuel resources. Thorium is plentiful and uranium scarce. These resources are assessed and the progress with fast breeder technology in India is reviewed. (U.K.)

[en] Two approaches for using UO₂-kernels in cladding tubes have been investigated, viz. the preparation of dense sphere-pacs and direct pelletizing (spherical). A theoretical study on the packing of spheres of different sizes showed that practical experiments were required. Model tests were, therefore, carried out, mostly with glass spheres. The most important results obtained are: A packing density of 80% can be exceeded if spheres of two sizes are used; quick and simple packing can be achieved with the mixing chute presented here; spheres pacs with a density of 90% for LWR cannot be prepared with kernels of practicable sizes; packing results can be translated to other tube diameters and to spheres and tubes made of other materials. The only suitable way to prepare dense pellets from kernels is pressing with a floating matrix at about 10 kbar, followed by removal under residual load. The kernels used should be produced without PVA and be reduced between 500⁰C and 800⁰C. Sintering is best accomplished in a limited oxidizing atmosphere at 1100⁰C with subsequent reduction. Stable pellets with up to 96% of their theoretical density could be produced this way. (orig.)

[en] The advantages of high resolution electron diffraction and imaging have been revealed in a wide variety of metallic systems, providing insight into the mechanisms of such phase transformations as ordering, spinodal decomposition, grain boundary precipitation, and the martensitic reaction. Structural discontinuities in interphase interfaces (atomic plane ledges) and grain boundaries (plane matching defects) have been identified with high precision, and compositional variations on an atomic scale have been detected, including solute segregation within approximately 10 A of a grain boundary. In the study of ceramics, primary effort has been directed toward the detection of thin intergranular films with notable success. Atomic dimension microledges have also been revealed in crystallization interfaces, polytype boundaries and transformation fronts, and compositional variations near grain boundaries have recently been recorded in lattice images of a Magnesium Sialon. It therefore appears that the technique holds equal promise for analysis of the fundamental mechanisms of crystallization, phase transformation, diffusion and solute segregation in ceramics as well as metallic alloy systems. The work presented here represents some of the potential of high resolution methods and is an initial step towards complete atomic characterization of materials. The most desirable progression of such research should lead to the attainment of structural images similar to those that are currently being used to explore the atomic arrangements in mineralogical specimens. This requires only a slight improvement in the contrast transfer characteristics of present day electron optics

[en] The problems that India has experienced with heavy water plants are described. The four plants under construction are at Baroda (67.2 t/y), Kota (100 t/y), Tuticorin (71.3 t/y) and Talcher (62.7 t/y). The plants employ different processes: Kota is based on a hydrogen sulphide water exchange process. Baroda and Tuticorin are based on the ammonia-hydrogen exchange process developed in France, and the Talcher plant is based on a West German process. Other problems such as disagreements with Canada, and high skin temperatures at the Baroda plant, are discussed. Three more heavy water plants have been proposed. (U.K.)

No abstract available

[en] The National Ignition Facility's (NIF) floor is damaged by transporter operations. Two basic operations, rotating the wheels in place and traversing the floor numerous times can cause failure in the grout layer. The floor is composed of top wear surface (Stonhard) and an osmotic grout layer on top of concrete, Fig. 1. An ultrasonic technique was implemented to assess the condition of the floor as part of a study to determine the damage mechanisms. The study considered damage scenarios and ways to avoid the damage. A possible solution is to install thin steel plates where the transporter traverses on the floor. These tests were conducted with a fully loaded transporter that applies up to 1300 psi loads to the floor. A contact ultrasonic technique evaluated the condition of the grout layer in NIF's floor. Figure 1 displays the configuration of the ultrasonic transducer on the floor. We inspected the floor after wheel rotation damage and after wheel traversal damage. Figure 2a and 2b are photographs of the portable ultrasonic system and data acquisition. We acquired ultrasonic signals in a known pristine area and a damaged area to calibrate the inspection. Figure 3 is a plot of the typical ultrasonic response from an undamaged area (black) overlapped with a signal (red) from a damaged area. The damage area data was acquired at a location next to a hole in the floor that was caused by the transporter. Five megahertz pulses are propagated from the transducer and through a Plexiglas buffer rod into the floor. The ultrasonic pulse reflects from each discontinuity in the floor. The ultrasonic signal reflects from the top surface, the Stonhard-to-grout interface, and the grout to concrete interface. We expect to see reflections from each of these interfaces in an undamaged floor. If the grout layer pulverizes then the high frequency signal cannot traverse the layer and the grout to concrete interface signal will decrease or vanish. The more damage to the grout the more the signal will be reduced. A secondary effect might show in the Stonhard-to-grout interface reflection. As the grout layer pulverizes the strength of the Stonhard-to-grout interface signal may increase because Stonhard-to-air is a stronger reflector that the Stonhard-to-grout. This waveform may also distort because of small particles of the grout adhering to the Stonhard surface. We have experienced both these effects

[en] Polarization of both electron and positron beams at a future linear collider (LC) allows for the measurement of transverse polarization asymmetries. These asymmetries have been shown to be particularly sensitive to graviton or other spin-2, s-channel exchanges in the process e⁺e^- → f(bar f) (F ≠ e) which allows for a doubling of the usual search reach. A question then arises as to whether other e⁺e^- processes also show comparable sensitivity. Here we extend our previous analysis to the set of final states e⁺e^-, W⁺W^-, 2γ and 2Z as well as to the Moeller scattering process e^-e^-. We demonstrate that these reactions yield transverse polarization asymmetries which are somewhat less sensitive to graviton exchange than are those obtained in our earlier analysis for e⁺e^- → f(bar f)

[en] With one extra dimension, current high precision electroweak data constrain the masses of the first Kaluza-Klein excitations of the Standard Model gauge fields to lie above ≅ 4 TeV. States with masses not much larger than this should be observable at the LHC. However, even for first excitation masses close to this lower bound, the second set of excitations will be too heavy to be produced thus eliminating the possibility of realizing the cleanest signature for KK scenarios. Previous studies of heavy $Z'$ and $W'$ production in this mass range at the LHC have demonstrated that very little information can be obtained about their couplings to the conventional fermions given the limited available statistics and imply that the LHC cannot distinguish an ordinary $Z'$ from the degenerate pair of the first KK excitations of the γ and Z. In this paper we discuss the capability of lepton colliders with center of mass energies significantly below the excitation mass to resolve this ambiguity. In addition, we examine how direct measurements obtained on and near the top of the first excitation peak at lepton colliders can confirm these results. For more than one extra dimension we demonstrate that it is likely that the first KK excitation is too massive to be produced at the LHC

[en] A brief overview of the signatures for several different models with extra dimensions at the stage II,√s = 175 - 200 TeV VLHC is presented. In all cases the search reaches for these models in the Drell-Yan channel are found to be in the range of 15-80 TeV