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Research paper on nuclear fission reactor moderators

Project by Polygence alum Arif

Research paper on nuclear fission reactor moderators

Project's result

Research Paper

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The goal of this study is to find the best and most feasible compound(s) to use in a nuclear reactor as a moderator in order to achieve a chain reaction with maximum efficiency. To obtain a chain reaction with the most energy output per volume material used, neutrons need to be able to collide with radioactive material in a manner that will maximize the probability of fission. For this to happen, the cross section for fission must be exceptionally large. This is attainable by slowing down the speed of neutrons by use of a moderator. A number of criteria must be met for a moderator to be considered the most feasible. For one, it must be able to quickly thermalize neutrons from the MeV range down to a few eV. In this paper, we will define thermalization as reducing a neutron’s energy from 2 MeV to 0.025 eV [3]. Second, it mustn’t have a high affinity for absorbing neutrons. And lastly, it must be cheap and abundant. If these criteria are met, we have found a good moderator. Various studies have been conducted in this field, and the results vary depending on the type of reactor at the center of the experiments. For fast reactors, the most common coolant used at is Helium(g) (4He) due to its low density. As a result, only a few collisions between high-energy neutrons and moderator occur, which leads to the sustained high-energy level of the neutrons, which is favorable for the compound nucleus formation process. In thermal reactors, the common consensus is that light water, heavy water, and graphite are best at slowing down high-energy neutrons to room temperature in the least number of collisions. Water and graphite are further aided by their relatively high density and favorable collision kinematics. This study will primarily explore to substances: Zirconium Hydride and Yttrium Hydride, and their abilities to act as moderators for slow water reactors. 1



Polygence mentor

MSE Master of Science in Engineering


Physics, Engineering


Physics, Robotics, Nuclear Physics Fission/Fusion Energy, Clean Energy, Environmental Science, Nuclear Security, Global Security Questions in Artificial Intelligence/Policy, Nuclear Weapons, Fintech / Finance





Centennial High School

Graduation Year


About my mentor

“My mentor guided me in the research process perfectly. She taught me to look in all the right places.”