Annals of Nuclear Science and Engineering最新文献

At the Conference, held in London in March 1974, there were five plenary sessions devoted to past and current experience and to future plans for incorporating fast reactors into the electrical supply networks and there were six specialist sessions devoted to: steam generators; nuclear performance; core including fuel; control, dynamics and hydraulics; coolant management; and fuel handling and other mechanisms. The main points raised in the papers to the Conference are summarized and, in a final section, the writer makes his own assessment of the conclusions to be drawn from the information presented.

The fission cross-sections of U-235, U-238 and Pu-239 and the capture cross-section of U-238 have been evaluated in the energy range 100 eV to 20 MeV. Below 100 keV, the cross-sections have been considered independently but at energies above 100 keV, all the accepted data on the cross-sections and their ratios have been used simultaneously in a least squares fitting procedure, using weighting functions derived from assigned errors. The evaluated cross-sections and their associated uncertainties are given together with recommendations for further experimental measurements.

The paper describes the work carried out in the Mechanical Engineering Laboratory on the vibration of free-free beams under liquids of various densities.

A study of the formation of multiple vortex cells due to vibration has been made. It was found that the diameters of these cells are a function of vibration amplitudes.

A method of calculating the natural frequencies of a free-free beam under liquids of various densities is presented.

Planning of nuclear power programs is an intricate task of reactors designers, depending on power needs and materials availability. An example for a possible nuclear power program is outlined and its mesh with published power needs and materials availability is pointed out. Recommendations showed the importance of an early start on the power program if dependence on local resources is to be emphasized, and the most promising fuel cycle to be adopted.

An experimental study is described which could provide a method for the non-destructive assay of the fissile content in depleted fuel elements of power reactors.

The basis of the method is a comparison of pulsed prompt neutron responses of the unknown fuel element with responses of known standards.

The method has been tested on non-irradiated BR2 fuel elements simulating two types of examination:

• 1.

  (a) determination of the remaining ²³⁵U-content and of the associated boron content (residual burnable poison);

• 2.

  (b) classification of poisoned CERMET-elements with respect to increasing burn-up, without discrimination of uranium and poison effects.

An installation is described which should allow determination of burn-up values up to 50 per cent within reasonable measuring times and with acceptable accuracy.

The propagation of thermal neutron waves has been studied in four beryllium parallelepipeds. The transverse bucklings of these parallepipeds ranged from 0·0497 to 0·2572 cm⁻², values which are greater than the critical buckling (0·00116 cm⁻²). From the space-time profiles, the dispersion law for beryllium was deduced over the frequency range 0 < ω < 1000 Hz. For the larger systems good agreement was found with calculations based on thermalization theory at frequencies less than 600 Hz. The effect of continuum contamination was apparent in all the systems but in the larger blocks this contamination had about the same magnitude and attenuation as the discrete modes. For the smaller systems, the continuum contamination was associated with neutrons having energies below the Bragg cut-off and was manifested by oscillations in the complex inverse relaxation lengths at the higher frequencies.