Reactivity Coefficients In A Thorium Oxide Fuelled, Heavy Water Moderated And Cooled Reactor (Part A); Validity of Bragg Stopping Cross-Section Additivity Rule For SiC (Part B)

Abstract

<p> Part A Abstract </p> <p> Temperature coefficients of reactivity for an 37-element reference design of a thorium oxide fuelled, heavy water moderated and cooled reactor, are calculated. The physical processes which determine magnitude and sign of the coefficients are identified and discussed. Results are given for fresh fuel containing equilibrium concentrations of the fission product Xe-135 and with boron control in the moderator. Results are. also -given for fresh fuel with the equilibrium concentration of Xe-135 but without boron contorl for fuel with an exposue of 1.513 n/k barn and for fuel with an exposure of 3.13 n/k barn; each containing appropriate concentrations of 50 separate nuclides and one-pseudo fission product. The fuel temperature coefficient of reactivity is negative for all the cases studied, while the coolant temperature coefficient of reactivity is positive for all the cases studied. The void effect is an increase in reactivity for all cases studied. </p> ////////////////////// <p> Part B Abstract </p> <p> This work has been done with the purpose of studying the validity of Bragg Kleeman rule which states that for combinations of elements, the atomic stopping cross-sections are additive. The validity of Bragg Kleeman rule for low energy He ions has not been conclusively tested for solids. In this work, the comparison with the experimental stopping power of SiC with the additive stopping powers of Si and C has been made experimentally. </p> <p> A thick target technique in the experimental evaluation of the stopping powers is used. This method has some simplicity over the thin target techniques. </p> <p> A calibration of the McMaster University Van-de Graff accelerator was done. Experiments were conducted later using the calibration curves produced. </p> <p> The report contains a brief account on different sources of errors due to the Van-de-Graff accelerator calibration and due to stopping power experiments. </p>