what is nuclear radiation

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:

• electromagnetic radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ)
• particle radiation, such as alpha radiation (α), beta radiation (β), proton radiation and neutron radiation (particles of non-zero rest energy)
• acoustic radiation, such as ultrasound, sound, and seismic waves (dependent on a physical transmission medium)
• gravitational radiation, that takes the form of gravitational waves, or ripples in the curvature of spacetime

10 eV

Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms.

A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, and photons, respectively. Other sources include X-rays from medical radiography examinations and muons, mesons, positrons, neutrons and other particles that constitute the secondary cosmic rays that are produced after primary cosmic rays interact with Earth’s atmosphere.

ionize

Gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The word “ionize” refers to the breaking of one or more electrons away from an atom, an action that requires the relatively high energies that these electromagnetic waves supply.

Further down the spectrum, the non-ionizing lower energies of the lower ultraviolet spectrum cannot ionize atoms, but can disrupt the inter-atomic bonds which form molecules, thereby breaking down molecules rather than atoms; a good example of this is sunburn caused by long-wavelength solar ultraviolet.

The waves of longer wavelength than UV in visible light, infrared and microwave frequencies cannot break bonds but can cause vibrations in the bonds which are sensed as heat. Radio wavelengths and below generally are not regarded as harmful to biological systems. These are not sharp delineations of the energies; there is some overlap in the effects of specific frequencies.

radiation

The word “radiation” arises from the phenomenon of waves radiating (i.e., traveling outward in all directions) from a source. This aspect leads to a system of measurements and physical units that are applicable to all types of radiation.

Because such radiation expands as it passes through space, and as its energy is conserved (in vacuum), the intensity of all types of radiation from a point source follows an inverse-square law in relation to the distance from its source. Like any ideal law, the inverse-square law approximates a measured radiation intensity to the extent that the source approximates a geometric point.

Cosmic radiation

There are two sources of high energy particles entering the Earth’s atmosphere from outer space: the sun and deep space. The sun continuously emits particles, primarily free protons, in the solar wind, and occasionally augments the flow hugely with coronal mass ejections (CME).

The particles from deep space (inter- and extra-galactic) are much less frequent, but of much higher energies. These particles are also mostly protons, with much of the remainder consisting of helions (alpha particles).

GRB

A few completely ionized nuclei of heavier elements are present. The origin of these galactic cosmic rays is not yet well understood, but they seem to be remnants of supernovae and especially gamma-ray bursts (GRB), which feature magnetic fields capable of the huge accelerations measured from these particles.

They may also be generated by quasars, which are galaxy-wide jet phenomena similar to GRBs but known for their much larger size, and which seem to be a violent part of the universe’s early history.

Energy given off by matter in the form of tiny fast-moving particles (alpha particles, beta particles, and neutrons) or pulsating electromagnetic rays or waves (gamma rays) emitted from the nuclei of unstable radioactive atoms. All matter is composed of atoms, which are made up of various parts; the nucleus contains minute particles called protons and neutrons, and the atom’s outer shell contains other particles called electrons.

Radioactive nuclei

The nucleus carries a positive electrical charge, while the electrons carry a negative electrical charge. These forces work toward a strong, stable balance by getting rid of excess atomic energy (radioactivity). In that process, unstable radioactive nuclei may emit energy, and this spontaneous emission is called nuclear radiation.

All types of nuclear radiation are also ionizing radiation, but the reverse is not necessarily true; for example, x-rays are a type of ionizing radiation, but they are not nuclear radiation because they do not originate from atomic nuclei. In addition, some elements are naturally radioactive, as their nuclei emit nuclear radiation as a result of radioactive decay, but others are induced to become radioactive by being irradiated in a reactor. Naturally occurring nuclear radiation is indistinguishable from induced radiation.

Ionizing beams

Nuclear radiation refers to the particles and photons emitted during reactions that involve the nucleus of an atom. Nuclear radiation is also known as ionizing radiation or ionising radiation (depending on the country). The particles emitted by nuclear reactions are sufficiently energetic that they can remove electrons from atoms and molecules and ionize them.

Nuclear radiation includes gamma rays, x-rays, and the more energetic portion of the electromagnetic spectrum. Ionizing subatomic particles released by nuclear reactions include alpha particles, beta particles, neutrons, muons, mesons, positrons, and cosmic rays.

What does radiation from a nuclear disaster actually do to our bodies?

Atomic weapons and nuclear accidents like those at Chernobyl and Fukushima have made sure we all know that nuclear radiation can kill.

But how exactly does the radiation affect our bodies? And why does radiation sometimes cause cancer, and other times cure it?

Nuclear radiation is the energy given off by all radioactive elements when they break down into more stable atoms. And it is being produced in and around you right now.

Radioactive atoms in everything — from rocks to bananas and even our bodies — give off energy as they decay to more stable forms.

500 mSv

Our cells can easily clean up any damage done by this low-level background radiation — on average Australians are exposed to about 1.5 millisievert (mSv) of background radiation a year — but it is a different story if you are exposed to doses greater than about 500 mSv.

The combination of how much radiation you are exposed to, what type, and how often will determine the effect on your cells and tissues.

Low doses of nuclear radiation are more likely to change cells by modifying DNA, while high doses tend to kill cells.

Getting Cancer

So long-term exposure to low doses of radiation increase the odds of getting cancer, while a single high dose will quickly cause immediate damage to cells and tissues — a process used effectively to kill tumour cells in radiation therapy.

Very high doses like those experienced by workers at the site of nuclear accidents (several thousand times higher than the background radiation level) cause extensive damage, resulting in a range of symptoms known collectively as radiation sickness. Extremely high doses can kill in days or weeks.

What is nuclear radiation?

The high-energy radiation given off by radioactive decay can take the form of very high speed particles (electrons in the case of beta radiation; two protons and two neutrons in alpha radiation) or waves (gamma or X-rays).

Regardless of the form it takes, all nuclear radiation has enough energy to strip electrons off atoms and molecules that it interacts with, earning it the name ionising radiation.

It is this electron-stripping (ionising) property that does the damage to our cells and tissues.

DNA

As well as generating heat, the removal of electrons can break chemical bonds. When that happens in a molecule of DNA it can cause mutations, which can lead to cancer down the track. And ionising a protein can mess with its shape and function — not something you want in the molecules that coordinate most of the chemistry in our cells.

Those effects are compounded when water molecules (H₂O) in our bodies are ionised into the high energy free radicals OH^– and H⁺, which can go on to attack other nearby molecules and cells.

Our bodies are full of water, and almost all cells have DNA, but some cells and tissues are more susceptible to damage from nuclear radiation than others.

Types of radiation

Nuclear radiation arises from hundreds of different kinds of unstable atoms. The energy of each kind of radiation is measured in electron volts (eV). The principal kinds of ionizing radiation are:

Alpha particles

Alpha (α) particles consist of two protons and two neutrons, and are positively charged. They are often very energetic. But because of their large size they cannot travel very far before they lose this energy. They are stopped by a sheet of paper or skin. And are only a potential health concern if they are ingested or inhaled.

The alpha particles’ large size, relatively speaking, and high energy are key to understanding their health impacts. When inside the human body, alpha particles can cause damage to the cells. And to DNA as their size makes it more likely that it will interact with matter. If the dose is too high for repairs to be made satisfactorily. There is a potential increase in the risk of getting cancer later in life.

Other types of radiation

X-rays are also electromagnetic waves and ionizing, virtually identical to gamma rays, but not nuclear in origin. They are produced in a vacuum tube where an electron beam from a cathode is fired at target material comprising an anode. So are produced on demand rather than by inexorable physical processes. (However the effect of this radiation does not depend on its origin but on its energy. X-rays are produced with a wide range of energy levels depending on their application.)

Cosmic radiation consists of very energetic particles, mostly high-energy protons, which bombard the Earth from outer space. They comprise about one-tenth of natural background exposure at sea level, and more at high altitudes.

Destructive human tissue

Neutrons are uncharged particles mostly released by nuclear fission (the splitting of atoms in a nuclear reactor). And hence are seldom encountered outside the core of a nuclear reactor. Thus they are not normally a problem outside nuclear plants. Fast neutrons can be very destructive to human tissue. Neutrons are the only type of radiation which can make other, non-radioactive materials, become radioactive.

Thank you for staying with this post “what is nuclear radiation” until the end.