Radioactive decay - waves and particles Study Guide

When working with or near radioactive materials, it is crucial to understand the distinction between contamination and irradiation, as these terms describe different ways radioactive substances can interact with living organisms and the environment, leading to distinct hazards. Irradiation occurs when an object or person is exposed to radiation emitted from a radioactive source outside the body. The source itself does not touch the object, and after the source is removed, the object stops being irradiated. Think of it like being exposed to light from a lamp; the light hits you, but you don't become a lamp. The hazard from irradiation depends on the type of radiation (alpha, beta, gamma), its intensity, and the duration of exposure. Alpha radiation is easily stopped and is only dangerous if the source is very close; beta radiation travels further but can be stopped by thin metal; gamma radiation is highly penetrating and requires thick shielding. Contamination, on the other hand, occurs when an unwanted radioactive material is present on or within an object or person. This means radioactive atoms themselves are physically transferred to skin, clothing, or ingested/inhaled into the body. Once contaminated, the object or person becomes a radioactive source themselves, emitting radiation for as long as the radioactive material persists. This is generally more hazardous than irradiation from an external source because the radioactive material can be in direct contact with sensitive tissues, continuously irradiating them. For example, if radioactive dust is inhaled, it could be lodged in the lungs, constantly emitting radiation to the surrounding cells. Both contamination and irradiation can cause cell damage, mutations, and increase the risk of cancer, but the continuous internal exposure from contamination often poses a greater long-term risk due to the prolonged proximity of the radioactive source to tissues.

Nuclear fusion is a process where two light atomic nuclei combine to form a single, heavier nucleus. This process releases a tremendous amount of energy. It is the fundamental energy source of stars, including our Sun. For fusion to occur, the nuclei must be brought incredibly close together, overcoming the electrostatic repulsion between their positively charged protons. This requires extreme conditions: very high temperatures and pressures. At these high temperatures, atoms are stripped of their electrons, forming a plasma – an ionised gas. The energetic collisions within this plasma allow the positively charged nuclei to fuse. Examples of fusion reactions often involve isotopes of hydrogen, such as deuterium and tritium, combining to form helium and release a neutron and energy. While fusion offers the potential for a clean and virtually limitless energy source on Earth, sustaining the necessary extreme conditions for a controlled fusion reaction remains a significant scientific and engineering challenge. Current research aims to create fusion reactors that can produce more energy than they consume.