Q1. Graphite is used in nuclear reactors as a moderator to reduce the speed of fast neutrons and ensure a sustained nucl

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Q1 Graphite Is Used In Nuclear Reactors As A Moderator To Reduce The Speed Of Fast Neutrons And Ensure A Sustained Nucl 1 (221.42 KiB) Viewed 41 times

Q1. Graphite is used in nuclear reactors as a moderator to reduce the speed of fast neutrons and ensure a sustained nuclear chain reaction. It degrades over time and a good indicator of its condition is the linear thermal expansion coefficient, which is defined as the fractional change in length per degree of temperature change: 1 AL L, AT where Lo is the original length and AL is the change in length due to a change in temperature AT. Nuclear engineers require a non-contact way of measuring a inside the reactor and have asked you to develop a prototype system based on speckle interferometry. They provide you with graphite samples cut as a prism of dimensions 100 mm x 20 mm x 20 mm. The following components are available for you to assemble your setup: He-Ne laser (wavelength: 2=632.8nm); CCD camera with 1280 x 1280 square pixels with dimensions 6um x 6um with no dead areas between pixels; Imaging lens with magnification M=1/10; Various beam splitters, mirrors, collimating lenses and microscope objectives; a non-contact digital thermometer with an uncertainty of 0.1°C; a thermal chamber with temperature control; a phase shifting device (mirror on PZT transducer with controller). a) Decide on an appropriate interferometer that will allow you to determine a. Justify your decision. [5 marks] b) Make a detailed sketch of the setup indicating: Light source, illumination angle (of your choice), beam splitters, mirrors, sample and its orientation in the setup, coordinate axes, imaging lenses, cameras, etc. If you need to add extra components, justify your decision, and indicate any assumptions that you make. [5 marks] c) Based on your optical setup, write down an expression for the optical phase as a function of wavelength, displacement, and illumination angle, and calculate the illumination angle required to have a displacement per fringe ug = 1um. [5 marks] d) Describe the detailed step by step procedure that you would follow to determine the coefficient of thermal expansion as a function of temperature (including the necessary equations and results). Hint: how to set up the sample, temperature control, image acquisition, data processing, how to compute a from the fringe patterns, etc [6 marks) e) Is it necessary to identify the null fringe (N=0)? Justify your answer. [2 marks] f) Indicate potential sources of error and actions required to reduce them. [2 marks]