Introduction to nuclear physics

Atom

Nuclear Physics deals with the interaction of mostly radioactive atoms, isotopes, and elements inside of a nuclear reactor and its corresponding nuclear components. The primary area of interest for Nuclear Engineering, is the atomic level behavior of particles inside of a nuclear reactor which lead to the production of energy via the fission process. For simplicity, we will begin our discussion of nuclear physics by considering a boiling water reactor and the fission process. A basic understanding of the fission process is therefore desireable and is the starting point for our discussion of Nuclear Physics.

## Neutron Physics

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Neutronic behavior inside of nuclear reactor is largely theoretical but there are some calculations to explain their behavior. Typically, a neutron source such as Beryillium is needed to start the chain reaction of the fission process inside of a nuclear reactor.

## Basic Neutron-Uranium Interaction

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Neutron

->U235 atom = more neutrons + Gamma energy + Alpha energy + fission "daughter" products

## Nuclear Physics - The Fission Process

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Uranium 235 (U235) is a naturally occuring isotope in nature with a yield of about .0711%. U235 is enriched to 1-3% to be used inside nuclear fuel bundles to fuel a typical boiling water reactor (BWR). U235 is usually combined with Gadolinia 157 inside of a typical fuel bundle in order to 'moderate" the fission process. This will be explained later. In the fission process, a slow thermal neutron bombardes a u235 atom which causes the atom to split and give off 'fission products'. These products are typically gamma rays, alpha rays, more neutrons, and two new 'split' atoms roughly half the atomic weight of U235. This split or fissioning of atoms causes incredible amounts of heat to be released into the reactor coolant water which heats the water to steam which is used to turn the turbine.