Some elements in nature are so highly charged that energized atoms with their central nucleus can expel radioactive rays and beams not only from local sources like a pieces of Uranium rock but they even come from space in the shape of X-rays in the form of cosmic rays as well as from infra-red, micro-waves, radio-waves, ultraviolet and visible light.
For this article, we will be concentrating on ionizing Alpha, Beta and Gamma radiation, each has different scientific qualities as well as varying penetration rates into other materials, there are different disintegration rates, these are dependent on the source of the radioactive decay.
Alpha – the name and act of the emission of an alpha particle (helium nuclei).
Beta – the name and act of the emission of electrons or positrons.
Gamma – the name and act of emission of energetic protons.
The radioactive sources go through periods of decay measured in “half-lives”, Plutonium
[Pu-239] has a half-life of 24,100 years (the time it takes to emit half of it initial energy), elements with short half-lives decay more quickly than those with longer half-lives, because of this they emit more energetic radioactivity – during this decay period, they go through a transmutation stage and can often change to other radioactive isotopes.
Radiation has found a lots of uses, it can be used in a controlled state within nuclear power stations when nuclides that are contained in enriched pellets are bombarded into each other within a reactor vessel, the energy and heat that is emitted by this process is used to heat up water, this then turns to steam that goes on to spin huge turbines creating electricity
Typical Alpha particles can be stopped by a piece of paper whilst Beta particles can be stopped with a plate of aluminium, Gamma radiation is damped and slowed down if it penetrates lead.
Radiation damages cells if in an uncontrolled amount due to exposure but it has found less damaging applications medicinally as a therapy for cancer treatment where forms of it are used to precisely target and kill cancerous cells as with a ‘Lazer knife’ radiotherapy treatment It is used in X-ray machines to map internal organs and to determine if bones are broken or damaged after an accident to decide upon the best form of further treatment.
A radiation source is also used within (Computerized Tomography) CT scanning machines that combine a series of X-rays taken from different angles around the body then combining them using computer processing power to map and create cross-sectional with dimensional images (slices) of the bones, blood vessels and soft tissues inside of your body, CT scans provide more detailed images than that of plain X-rays.
A Positron emission tomography (PET) scan is a test to see in real-time how your internal tissues and organs are functioning, it can be used to detect disease and healthy tissue by the ingestion of a fluid or injection of a ‘tracer’, the most common ‘tracer’ is fluorodeoxyglucose and is taken before the PET scan, sometimes due to the combination, this test is often called an FDG-PET scan.
There are different ways of measuring radiation and doses, invasive and non-invasive radiotherapy treatments have their risks but save lives and others shorten overall treatment as well as prolonged stays in hospitals lessening risks of dangerous cross-infections including Methicillin-resistant Staphylococcus aureus (MRSA).
The generally agreed safe dose of radiation per person per year is 1.0 millisieverts (mSV).
A single X-ray exposes the patient to about 0.1 mSV.
A mammogram exposes the patient to about 0.4 mSV.
A CT scan of the abdomen (belly) and pelvis exposes the patient to about 10 mSv.
A PET scan exposes the patient to about 25 mSv of radiation.
These figures may seem high to you but background radiation exposes us continually and we cannot ideally stop this, levels typically range from 1.5 – 3.5 mSv per year but can be more than 50 mSv*
*Background radiation comes from:
- Cosmic – radiation that reaches earth from space.
- Terrestrial – radiation that is emitted from rocks and soil.
- Internal – radiation from living things, plants and animals that absorb radiation passing these materials up the food chain.
There are other uses for radiation all around us every day, Americium-241 is used in smoke detectors, a containment chamber in one of these safety devices works by way of the Am-241 source being blocked due to smoke particles, the alarm will sound.
Iridium-192, Cobalt-60 or Cesium-137 are used in industrial radiography cameras to inspect hard to reach areas or systems where safety is paramount, like on points of welding in aircraft to make sure there are no defects.
Food irradiation is an approved way of killing bacteria and sterilizing foodstuffs, gamma rays from Cobolt-60 or Caesium-137 are routinely used to sterilize dental, household and medical supplies.
Gamma rays are used to scan shipping containers and lorries for illegal or dangerous goods protecting our nations.
X-rays are used in electron microscopes to view very small sources, this has a number of uses from microbiology to electronics and quality control, the primary electron beam or backscattered electrons hit a backplate that excites the source with sufficient energy to make up a picture on a screen for analysis.
There are many more uses for radiation in the medial, industrial commercial sectors but the most worrisome (now) is from Nuclear accidents, thermal runaway events, containment leaks or hydrogen explosions at facilities meant to make our lives easier and less dependant on fossil fuels including carbon, there have been more than 100 nuclear accidents from Tchernobyl in Ukraine to the Fukushima (ongoing fallout) accident in Japan caused by the Tsunami on March 26th 2011, serious accidents include those of the Costa Rica radiotherapy accident, The Kyshtym disaster the Windscale fire and others.
Thankfully now the risk of Thermonuclear exposure with nuclear bombs has lessened with the ending of the ‘Cold War’ (1947 – 1991), there was a time where the risk of attack was very real but this is over as relations between countries, particularly the USA and (former) USSR have improved.
Unfortunately, radioactive sources are still used on the battlefield today with the use of depleted uranium [Du-38], this has a lower radioactive content than fissile Uranium-235 and is used in A-10 “Warthog” Tankbusters ammunition as well as in AH-1 Cobra helicopter and Challenger tanks.
Depleted Uranium is used due to its very high density, it is 1.67 dense as lead and only slightly less dense than tungsten and gold – it is 84% as dense as osmium and iridium which are the densest materials known under standard (earth surface) pressures meaning projectiles with a DU core can penetrate ballistic materials effectively, DU is also used in tank and strategic placement armor.
In the theater of war, these projectiles are of course a risk but once the war has finished and if the DU shells are not responsibly and ethically cleaned up, the risk of exposure is still there. Cancers and cognitive defects are evident and ongoing with this material (and the targets) going on for generations.
Radiation helps civilizations and promotes science as well as the health of earths inhabitants, it can also be very damaging but as it is not only prevalent in nature as well as being used for human-made techniques, be it for industrial, science of war, we simply cannot get away from it.