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Regional Basic Professional Training Course in Korea

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1. Nuclear Reactor Pr<strong>in</strong>ciples<br />

❙ 7 ❙<br />

1. Nuclear Reactor Pr<strong>in</strong>ciples<br />

1.1. OVERVIEW OF NUCLEAR PHYSICS AND<br />

RADIOACTIVITY<br />

1.1.1. Radioactivity<br />

Matter is the name given to the materials of which the universe is composed. It exists <strong>in</strong><br />

four physical forms: solids, liquids, gasand plasma. All matter is found to consist <strong>in</strong> a<br />

number of simple substances called elements. Elements are substances, which cannot be<br />

broken down by ord<strong>in</strong>ary chemical means <strong>in</strong>to simpler, smaller substances. There are 90<br />

naturally occurr<strong>in</strong>g elements on earth, such as oxygen. In nature, elements are usually<br />

chemically l<strong>in</strong>ked to form compounds, which consist of two or more elements l<strong>in</strong>ked <strong>in</strong><br />

def<strong>in</strong>ite proportions, like water, H2O, which consists of two atoms of hydrogen and one<br />

atom of oxygen.<br />

Elements are made up of atoms. The atom is made up of neutrons and protons tightly

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