Flexural Strength of Specimens Prepared from Several Uranium Dioxide Powders; Its Dependence on Porosity and Grain Size and the Influence of Additions of Titania

Abstract

Flexural strengths of specimens prepared from four uranium dioxide powders were determined at room temperature and at 1000°C. The relation of the strength ( S ) to porosity ( P ) and to grain size (G) could be represented by the expression S = kG-.e-hP, where k, a, and b are empirical constants which differed with test temperature but did not differ for the different urania powders used. Additions of titania were very effective in promoting sintering and additions of 0.50 or 0.75% by weight markedly increased the strength of the specimens.

Review and Statistical Analysis of the use of Ultrasonic Velocity for Estimating the Porosity Fraction in Polycrystalline Materials

“…As examples concerning key properties of technologically-important materials, porosity fraction has been shown to affect (1) the strength, toughness and modulus of structural and refractory materials such as Steel [1], Tungsten [2], SiC [3], Si3N4 [3], and A1203 [3], (2) the strength of nuclear fuel materials such as U02 [4][5], (3) the thermal shock behavior and strength of porcelain-based ceramics [6-7J, (4) the dielectric and elastic properties of piezoelectric materials such as PZT [8], and (5) the critical current density, diamagnetic response, and modulus of superconducting ceramics such as YBa2Cu307_x [9-11J. In such cases where physical properties are directly dependent on porosity fraction, the measurement of porOSity fraction becomes important in the quality assurance process for the material.…”

Modelling pellet-clad mechanical interaction during extended reduced power operation in bonded nuclear fuel

“…14a shows that very high tensile hoop stresses (424 MPa) were observed in the sliver as a result of thermal expansion during the initial rise to power. These could be sufficient to introduce the ladder cracks given a fuel fracture stress in the range of 50 -250 MPa, with a value of 125 MPa considered typical [58][59][60][61]. In addition, both modelling and experimental work has shown a greater concentration of cracks on the outer surface of the pellet compared to the inner surface in AGR fuel [62] and a number of radial cracks on the outer surface of PWR fuel [63].…”