TEMPERATURE DISTRIBUTION AND THERMAL STRESSES IN RADIATION-COOLED CIRCULAR CYLINDERS. Technical Report ME-7

Abstract

An investigation has been undertaken to study the thermal stresses in a cylindrical NAP fuel rod. The study has consisted of two phases, one analytical and the other experimental. In the analytical phase, a mathematical model of a fuel rod has been developed in which the rod is considered to be a long solid circular cylinder cooled by emission of thermal radiation. A closed form of solution for the temperature distribution could not be obtained, so numerical results for the temperature and stress distributions were obtained by finite difference methods. The results predict that relatively small stresses are produced when the fuel rod is cooled in a temperature range in which brittle fracture can reasonably be expected. The experimental phase, which is not yet complete, was undertaken to verify the predicted temperature and stress distributions. Rather than using an actual fuel rod in the experimental program, which would present formidable safety and security problems, a modeling technique is being used. The theory of similitude will be employed to relate the results obtained from the physical model to those which one would expect to obtain from a fuel rod. An embedded strain gage technique is being used to measure internal strains.

Temperature and stress distributions produced in long circular cylinders cooled by emission of thermal radiation

“…Relatively good agreement is found to exist between the experimental and analytical results, as concluded in Chapter 7 of Part I. Due to this agreement, it is felt that a useful answer can be deduced for the problem which motivated the investigation reported in references (1,3) and this report.…”

“…The evidence and logic which lead to this answer are contained in references (1,3) and Part I of this report. The interested reader may wish to read these reports and arrive at an answer for himself.…”