Showing papers by "Jitendra Kumar published in 1969"

The Electron Microscopic Observation of Mechanical Twins in Gadolinium

Abstract: Mechanical twinning in gadolinium has been observed using an electron microscope. The analysis of electron diffraction patterns revealed that the twinning elements are K1 = K2 = (1012) and η1 = η2 = [1011]. The possible mechanism of genesis for these twins are investigated. It is found that the twins are nucleated due to thermal stresses set up in the films as a result of electron irradiation. There is no evidence for the pole dislocation mechanism to be operative in the present case, instead, the observations suggest that the twin formation is in accordance with the Bell-Cahn mechanism. Mit dem Elektronenmikroskop wurde in Gadolinium mechanische Zwillingsbildung beobachtet. Die Analyse von Elektronenbeugungsbildern zeigt, das die Zwillingselemente K1 = K2 = (1012) und η1 = η2 = [1011] sind. Der mogliche Mechanismus der Erzeugung dieser Zwillinge wird untersucht. Es wird gefunden, das diese Zwillingbildung durch Keime erfolgt, die durch thermische Spannungen im Ergebnis einer Elektronenbestrahlung gebildet werden. Es existiert kein Hinweis fur einen Polversetzungsmechanismus fur den vorliegenden Fall, stattdessen weisen die Beobachtungen darauf hin, das sich die Zwillingsbildung in Ubereinstimmung mit dem Bell-Cahn-Mechanismus befindet.

Eddy Current Testing of Zirconium Wires

Abstract: FUEL bundles for Rajasthan Atomic Power Reactor, as per the design, consist of a cluster of 19 elements held together by zircaloy end plates and spaced by wire helices on the six elements of the inner ring and alte-rnate elements of the outer ring. Each element is a zircaloy-2 tube 495 min long,1524 mm in diameter and of 0.4 nom wall thickness containing the nuclear fuel in the form of sintered uranium dioxide pellets and sealed at both ends. In order to provide the required spacing between the elements, zircaloy wire of 1.25 mm dia. is spot-welded around the elements in the helix form. The wire helices serve to separate the elements to maintain the dimensions of the coolant sub-channels between them and to increase the mixing of coolant between inner and outer sub-channels. Zircaloy wire of 1.63 mm dia. is spot-welded on the outer elements so as to provide bearing surfaces for the bundle when it moves through the fuel channels in the coolant assemblies.