Radioisotopes play a vital role in our world, they are mainly used in medicine, agriculture, industry and scientific research. An isotope is a variant of an element where differing numbers of neutrons exist in the nucleus of the atom where the atomic number stays the same. A radioisotope is a radioactive or unstable isotope of an element where the atom releases radiation in one or more of three different forms in an attempt to become stable (What are radioisotopes?, n.d.). These forms alpha (), beta () and gamma () radiation, all have different properties and are created in different ways when the nucleus of an atom tries to become stable.
Gamma : Technetium – 99m
9943Tcm 9943Tc +
Half Life = 6 hours
Technetium 99m is the most widely used radioisotope in medicine and accounts for 80% of nuclear procedures worldwide. Technetium 99m is predominantly used in bone and brain scans as well as finding cancers (Uses of Technetium-99m, n.d.). However, it is also used for imagery of the skeleton and heart mainly but also the brain, thyroid, lungs, liver, spleen, kidney, gall bladder, bone marrow, salivary and lacrimal glands and infection (Uses of Technetium-99m, n.d.). When being used for imagery, technetium 99m is injected into the body, as it travels around the body equipment outside the body is used to pick up the level gamma radiation and the data is then used to create an image. When detecting cancers in the body technetium 99m is attached to proteins which are able to bind with cancerous cells. After a few hours after injection of technetium 99m into the body, medical equipment is used to detect gamma rays being emitted and higher concentrations show where the cancer is (Uses of Technetium-99m, n.d.). Technetium 99m is also able to be attached to many other molecules all which travel to different parts of the body. This is extremely important as it means that all parts of the body can be seen and imaged to find problems etc (Properties of Technetium-99m, n.d.).
Technetium 99m has a half-life of 6 hours and it emits low energy gamma radiation (Properties of Technetium-99m, n.d.). This half-life is long enough for doctors to be able to detect the metabolic process, but still short enough not to cause harm to the body. The short half-life of technetium 99m also means that doctors can collect data quickly and efficiently. Gamma radiation is also the least ionising of all types of radiation which means it causes the least damage to tissue in the body. The low energy gamma radiation that technetium 99m emits is also important as it is less harmful when travelling through the patient’s body and causes less damage to tissues. Gamma rays are highly penetrative and can travel through the body with ease and can still be easily detected by gamma cameras outside the body. The short physical and biological half-life of technetium 99m also means that it is cleared from the body quickly after its medical application.
Technetium 99m is a fairly safe radioactive isotope to use and hand as it gives off low energy gamma emissions. When handling or using technetium 99m standard lab equipment of gloves, lab coats and safety glasses is used (Safety Precautions of Technetium-99m, n.d.). When using technetium 99m it is prohibited to eat, and drink and it should be kept in clearly labelled containers that the gamma rays cannot penetrate through. Due to technetium 99m emitting gamma radiation it needs to be kept in an enclosed lead container. It is also recommended to be stored at room temperature away from heat, sparks and flames. After use surfaces and safety equipment should be decontaminated to remove any potential radiation sources. It is also important to safely dispose of the radioactive substance so that radiation doesn’t build over the legal limit and effect the environment and an individual. All radioactive waste over 50MBq needs to be stored in lead containers and monitored until they reach acceptable levels (Safety Precautions of Technetium-99m, n.d.).
Technetium is one of two elements under uranium in the periodic table that do not exist naturally as they are so unstable, it is created through nuclear fission, the bombardment of an atom with neutrons in a nuclear reactor. Molybdenum 98 is bombarded with neutrons to create molybdenum 99 which has a half-life of 66 hours before it decays into technetium 99m. After technetium 99m’s 6 hour half-life it decays into technetium 99 and through beta it ends up as Ruthenium 99 (Production of Technetium-99m, n.d.). (See Figure 1 & 2)
Beta : Iodine-131
13153I 13154Xe + 0-1e +
Half Life = 8 days
Iodine 131 is a very dangerous radioisotope and is mainly used in medicine when dealing with the thyroid. The thyroid is one of the most important organs in the body as it deals with metabolism which is the process of converting food and oxygen into energy (Jardin, 2017). The thyroid can sometimes be overreactive or cancerous and so careful treatment is required. Iodine is extremely important in this situation as it the only element in the body that is absorbed by the thyroid meaning that iodine will always go to the thyroid and only the thyroid. Iodine 131 is taken by an individual through swallowing a capsule, the capsule then dissolves and the iodine 131 travels to the thyroid. In the case of thyroid cancer, after the cancer has been removed, doses of iodine 131 in pills are prescribed to absorb into the thyroid and destroy any remaining tissue. This procedure is done as a precaution in case parts of the thyroid cancer had broken off and moved to somewhere else in the body. The patient receiving this treatment must remain isolated for 3-5 days to prevent 2nd hand radiation. Once radiation levels fall to acceptable levels the patient is able to leave (Jardin, 2017).
Iodine 131 has a half-life of 8 days and highly radioactive meaning that small doses are often used in medicine (Iodide 131, n.d.). The half-life of iodine 131 is long enough for the iodine to be absorbed into the thyroid and have a good amount of time to use its beta emissions to destroy the thyroid and a cancer in it. Iodine 131 release beta emissions which is an electron that shoots out of each atom. These particles are not as penetrating as gamma but more penetrating than alpha, the particles are also more ionising than gamma but not as ionising as alpha. The means that when the iodine 131 is absorbed into the thyroid the beta emissions are radiated out and destroy the tissue around them. beta particles guarantee that only a small area of the body is affected as the particles cannot penetrate very far.
Iodide 131 is a very dangerous radioisotope and needs to be stored and handled with extreme care, it poses a large short-term risk with accidental release and waste disposal. When handling iodide 131 all skin should be covered, eyewear and gloves should also be worn. The protective clothing needs to be fairly thick to be able to block the beta particles. It is also important for handlers to not breath the radiation in so masks must be worn as well. It is important also to limit the time exposed to radiation and to decontaminate anything that may come into contact with the iodide (Radiation from Iodine, n.d.). When storing iodide 131 an enclosed aluminium box is sufficient to block the radiation however, the safest option is to use an enclosed lead box. Extreme care must especially be taken when disposing of the radioactive isotope and it must be kept in a proper storage container until levels of radiation reach an acceptable level. If iodide 131 escapes into the environment it must be monitored throughout the whole food chain to see how the radiation effects it.
Iodide 131 is made through neutron bombardment of uranium 235 in a nuclear reactor, it is a product of fission.
Alpha : Amerecium-241
24195Am 23793Np+ 42He
Half Life = 432 years
Americium 241 is a radioisotope used in smoke detectors, it decays by alpha emission and ionises with the air inside. This allows positively and negatively charged ions to flow between charged plates in the smoke detector (Americium in Smoke Detectors, n.d.). The smoke alarm is set off when smoke molecules interrupt this flow of ions. Americium emits only alpha particles which although they are the most ionising of all radiation they are the least penetrative and can’t even pass through a piece of paper. Due to this lack of penetration these alpha emitters are safe to have inside your house without threat to radiation, as long as the smoke alarm is untampered with and the ionising chamber doesn’t break. Even if this was to happen alpha particles cannot travel through skin and ionise after travelling through short amounts of air and only become a problem when inhaled, ingested or if they come into contact with a wound.
The half-life of americium is 432 years which is extremely useful in smoke detectors as the radioactive isotope will last for well long enough. However, if these radioisotopes find their way into the body it becomes extremely dangerous as there is a constant highly ionising radioisotope doing damage to cells. Too much exposure to radiation can lead to cancer and other health hazards.
When disposing of smoke alarms still containing americium 241 it is important to dispose of them properly through radioactive waste centres. By doing this it is protecting the environment and other people from possible exposure to extra radiation.
Smoke alarms are mostly safe to go near without any protection due to the fact that the radioisotope is enclosed, and the radiation cannot escape. However, if the ionising chamber is broken it is important to wear gloves, eyewear and a face mask as well as covering any breaks in the skin.