Annals of Nuclear Science and Engineering最新文献

This is a review on the effect of axial flow on cylindrical structures. It is shown that axial flow may cause fluidelastic instabilities at sufficiently high flow velocities. However, for the range of flow velocities and other parameters pertaining to most industrial systems, the effect of purely axial, uniform steady flow is to damp free motions. Nevertheless, departures from such ideal flow conditions induce small amplitude vibration, termed sub-critical vibration. The underlying mechanism of this vibration is examined and the various means available for predicting its amplitude are discussed. These latter are either empirical or analytical (generally semi-empirical); the analytical methods are further classified into three categories accordingly as they postulate the vibration to be forced, parametric or self-excited. The measure of success achieved in predicting sub-critical vibration amplitude is discussed, and possible reasons for its being generally poor. At present, the amplitude may be predicted typically to within one order of magnitude.

The meeting gave a good picture of the main problems being presently pursued in convective reactor heat transfer. Models for the prediction of the flow structures and temperature distributions in fuel subassemblies have made significant progress and are reaching a high level of sophistication. These models cover steady one-phase and two-phase flow as well as transient and accident conditions. Experiments on rod clusters investigating mixing in the cluster and the effect of spacers on it, as well as voidage and velocity distributions in subchannels are providing improved input data. Heat transfer on rough surfaces is still being studied, but no general reliable method for predicting the effect of such surfaces seems to be available yet. New data have been obtained on heat transfer in less common gases. Research on burnout seems to be concentrated mainly on transient situations. Increased activity is noticeable in the research of flow and heat transfer in typical heat exchangers of nuclear plant. In the field of reactor safety the main effort is concentrated on studies of the effect of blockages and accident conditions in fast reactor fuel assemblies and of blow-down and emergency flooding in water reactors. It is probably in this region that further experimentation is most urgently required. Some important problems not covered at the meeting have been pointed out on the previous pages.

A symposium on the Principles and Standards of Reactor Safety organised by the International Atomic Energy Agency (IAEA) was held at the Nuclear Research Centre, Julich, Federal Republic of Germany from 5th to 9th February, 1973.

The conference was attended by some 275 delegates from 32 countries; the majority coming from Belgium, France, Germany, Italy, Sweden, U.S.A. and the United Kingdom. The papers presented at the conference were divided into nine sessions under the following general headings.

• 1.

  (a) Philosophy of safety design.

• 2.

  (b) Quality assurance and reliability.

• 3.

  (c) Methods of safety evaluation for power reactors.

• 4.

  (d) Design for natural and man-made disasters.

• 5.

  (e) Siting considerations for power reactors.

• 6.

  (f) Standards and criteria for the design and construction of power reactors.

• 7.

  (g) Design safety features.

• 8.

  (h) Safety in high temperature gas cooled reactors.

• 9.

  (i) Safety in operation.

It is intended in this report to summarise the highlights of the symposium from a personal viewpoint.