Nuclear Engineering and Design 

Abstract: A simple procedure is proposed for calculating the number of atomic displacements produced in a damage cascade by a primary knock-on atom of known energy. The formulae have been chosen to give results in close accord with recent computer simulations of radiation damage phenomena. The proposed new standard is compared with other empirical formulae for estimating the number of atomic displacements in a cascade.

Abstract: The background of continuum damage mechanics is first presented in the framework of thermodynamics with some examples of constitutive equations for ductile damage, creep damage and fatigue damage. After the general scheme of structural calculations for macro-crack initiation, through non-coupled or coupled strain damage equations, some examples of “simple applications” are given: fracture limits of metal forming, surface initial damage in fatigue, creep fatigue interaction, and bifurcation of cracks.

Abstract: Boiling flow in a water-cooled reactor, an evaporator, or an electronic cooling system is susceptible to thermal-hydrodynamic instabilities, which may cause flow oscillations of constant amplitude or diverging amplitude. These oscillations could induce boiling crisis, disturb control systems, or cause mechanical damage. This paper identifies the causes and mechanisms of these instabilities. Based on their mechanisms, various types of instabilities are classified and tabulated. The parametric effects on flow instability, observed experimentally, are systematically presented. Various analytical techniques for predicting the instability threshold are reviewed in terms of their applicability and accuracy.

Abstract: Two-fluid formulation for two-phase flow analyses is presented. A fully three-dimensional model is obtained from the time averaging, whereas the one-dimensional model is developed from the area averaging. The constitutive equations for the interfacial terms are the weakest link in a two-fluid model because of considerable difficulties in terms of experimentation and modeling. However, these are of supreme importance in determining phase interactions. In view of this, the interfacial transfer terms have been studied in great detail both for the three- and one-dimensional models. New interfacial area, drag, virtual mass, droplet size and entrainment correlations are presented. In the one-dimensional model, a number of serious shortcomings of the conventional model have been pointed out and new formulations to eliminate them are presented. These shortcomings mainly arose due to the improper consideration of phase distributions in the transverse direction.

Abstract: Since the pioneering studies conducted by McClintock, Rice and Tracey on the growth of cavities, many studies have covered modelling of ductile fracture; a non-exhaustive list is given of these studies. In the local approach of fracture, the models are used at the tip of cracks, and in the present state, only relatively simple models can be used to solve fracture problems in a complete manner, from material characterization to the analysis of cracked structures. The paper presents two types of models based on a critical ratio of cavity growth or on continuum damage mechanics. In the framework of the local approach of fracture, their possibilities are presented with constant references to experimental validation studies. This allows conclusions to be drawn regarding the effectiveness of the methods proposed and their undeniable contribution to fracture mechanics.