Radiation

There are two opposing views on the effects of radiation. One view is based on a long held view of many substances normally considered toxic, that is, small doses are not harmful and in some cases are beneficial. Called Hormesis. This also applies to radioactive substances.

The other view is called the Linear No Threshold (LNT) model which assumes any radiation is dangerous.
Many are convinced that fear plays a factor and extreme attention to erring on the side of caution is an attitude that is preventing the growth of the nuclear energy industry.

Radiation is not a new phenomenon. It has been with us from the beginning of time. In fact the universe has become less radioactive over time. One reason that we can cope with radiation is that all creatures including humans evolved in a time when natural radiation was much higher than it is now.

Radiation comes from the largest atoms in the periodic table. They are less stable because of their size and show up towards the end of the periodic table.

Radioactive decay gives off either alpha or beta radiation. These particle emissions are the results of the change of the original atom to another element, either two atomic numbers smaller (alpha) or one higher (beta).

Alpha and Beta particles sometimes called rays are the activity that occurs naturally when a radioactive substance changes to another element which also confirms E= mc2.

Alpha Particles (Alpha Rays)-

Slow moving and short range emission of a few centimeters if in the air- The energy of alpha particles emitted varies, with higher energy alpha particles being emitted from larger nuclei, but most alpha particles have energies of between 3 and 7 MeV (mega-electron-volts), corresponding to extremely long to extremely short half-lives of alpha-emitting nuclides, respectively.
This energy is a substantial amount of energy for a single particle, but their high mass means alpha particles have a lower speed (with a typical kinetic energy of 5 MeV; the speed is 15,000 km/s, which is 5% of the speed of light) than any other common type of radiation (Beta particles – β, neutrons, etc.) Because of their charge and large mass, alpha particles are easily absorbed by materials, and they can travel only a few centimeters in air. They can be absorbed by tissue paper or the outer layers of human skin (about 40 micrometers, equivalent to a few cells deep).
Alphas are not, in general, dangerous to life unless the source is ingested or inhaled, in which case they become extremely dangerous.
Alpha emitters: radium, radon, uranium, thorium
Alpha radiation is the most destructive form of ionizing radiation. It is the most strongly ionizing, and with large enough doses can cause any or all of the symptoms of radiation poisoning. It is estimated that chromosome damage from alpha particles is anywhere from 10 to 1000 times greater than that caused by an equivalent amount of gamma or beta radiation, with the average being set at 20 times.

 

Transmutation of elements from one to another had been understood since 1901 as a result of natural radioactive decay, but when Rutherford projected alpha particles from alpha decay into air, he discovered this produced a new type of radiation which proved to be hydrogen nuclei (Rutherford named these protons). Further experimentation showed the protons to be coming from the nitrogen component of air, and the reaction was deduced to be a transmutation of nitrogen into oxygen in the reaction

14N + α → 17O + proton

Beta Particles (Beta Rays)-

Of the three common types of radiation given off by radioactive materials, alpha, beta and gamma, beta has the medium penetrating power and the medium ionising power. Can travel several feet in air. Although the beta particles given off by different radioactive materials vary in energy, most beta particles can be stopped by a few millimeters of aluminum. Being composed of charged particles, beta radiation is more strongly ionising than gamma radiation.
Beta emitters: strontium-90, carbon-14, tritium, and sulfur-35.

Example:
Cs-137 decays by beta radiation to become Ba-137M. The M means meta-stable which means that the nucleus has excess energy. This excess energy is dissipated by the release of a gamma ray almost immediately.

Gamma
Gamma radiation is electromagnetic, has no mass, and does not change the original atom to another element. Gamma radiation travels the farthest and is analogous to fluorescence; where excess energy is emitted in the form of a photon. Gamma rays are the smallest wavelength in the electro-magnetic spectrum. Gamma rays are also used to irradiate food which lills harmful bacteria. Gamma rays can be dangerous if the strength and length of exposure is high. Gamma ray photons are emitted from the nucleus and are a lot more energetic than fluoresced photons, which are emitted from the electron cloud.
Gamma emitters: iodine-131, cesium-137, cobalt-60, radium-226, and technetium-99m
Units

rems, sieverts, curies, bequerels, roentgen, rad, gray

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