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Shielded nuclear radiation containment chambers are commonly referred to as hot cells. The word "hot" refers to radioactivity. Hot cells are used in both the nuclear-energy and the nuclear-medicines industries. They are required to protect individuals from radioactive isotopes by providing a safe containment box in which they can control and manipulate the equipment required.
Hot cells are used to inspect spent nuclear fuel rods and to work with other items which are high-energy gamma ray emitters. For instance, the processing of medical isotopes, having been irradiated in a nuclear reactor or particle accelerator, would be carried out in a hot cell. Hot cells are of nuclear proliferation concern, as they can be used to carry out the chemical steps used to extract plutonium (whether weapons grade or not) from reactor fuel.[ citation needed ] The cutting of the used fuel, the dissolving of the fuel in hot nitric acid and the first extraction cycle of a nuclear reprocessing PUREX process (highly active cycle) would need to be done in a hot cell. The second cycle of the PUREX process (medium active cycle) can be done in gloveboxes.
Hot cells are commonly used in the nuclear medicines industry:
The user must never be subject to shine paths that are emitted from the radioactive isotopes and therefore there generally is heavy shielding around the containment boxes, which can be made out of 316 stainless steel or other materials such as PVC or Corian.[ citation needed ] This shielding can be ensured by the use of lead (common) or materials such as concrete (very large walls are therefore required) or even tungsten. The amount of radioactivity present in the hot cell, the energy of the gamma photons emitted by the radioisotopes, and the number of neutrons that are formed by the material will prescribe how thick the shielding must be. For instance a 1 kilocurie (37 TBq) source of cobalt-60 will require thicker shielding than a 1 kilocurie (37 TBq) source of iridium-192 to give the same dose rate at the outer surface of the hot cell. Also if some actinide materials such as californium or spent nuclear fuel are used within the hot cell then a layer of water or polyethylene may be needed to lower the neutron dose rate.
In order to view what is in the hot cell, cameras can be used (but these require replacing on a regular basis) or most commonly, lead glass is used. [1] There are several densities for lead glass, but the most common is 5.2 g/cm3. A rough calculation for lead equivalence would be to multiply the Pb thickness by 2.5 (e.g. 10 mm Pb would require a 25 mm thick lead glass window). Older hot cells used a ZnBr2 solution in a glass tank to shield against high-energy gamma rays. This shielded the radiation without darkening the glass (as happens to leaded glass with exposure). This solution also "self-repairs" any damage caused by radiation interaction, but leads to optical distortion due to the difference in optical indices of the solution and glass.
Telemanipulators or tongs are used for the remote handling of equipment inside hot cells, thereby avoiding heavy finger/hand doses.
Lead loaded gloves are often used in conjunction with tongs as they offer better dexterity and can be used in low radiation environments (such as hot cells used in hospital nuclear medicine labs). Some companies have developed tungsten loaded gloves which offer greater dexterity than lead loaded gloves, with better shielding than their counterparts. Gloves must be regularly replaced as the chemicals used for the cleaning/sterilisation process of the containments cause considerable wear and tear.
Hot cells can be placed in clean rooms with an air classification ranging from D to B (C is the most common).
These cells are often used to test new chemistry units or processes. They are generally fairly large as they require flexibility for the use of varying chemistry units which can greatly vary in size (e.g. synthera and tracerlab). Some cells require remote manipulation.
This type of hot cell is used purely for production of radiopharmaceuticals. A chemistry unit is placed in each cell, the production process is initiated (receiving the radioactive 18F from the cyclotron) and once finished, the cells are left closed for a minimum of 6 hours allowing the radiation to decrease to a safe level. No manipulation is necessary here.
Cells used to dispense products. For example, once Fludeoxyglucose (18F) (FDG) has been produced from 18
F mixing with glucose, a bulk vial is put into in a dispense cell and its contents carefully dispensed into a number of syringes or vials. Remote manipulation is crucial at this stage.
Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption. Different tracers are used for various imaging purposes, depending on the target process within the body.
Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, nuclear decommissioning, rare-earth mining, and nuclear weapons reprocessing. The storage and disposal of radioactive waste is regulated by government agencies in order to protect human health and the environment.
A beta particle, also called beta ray or beta radiation, is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β− decay and β+ decay, which produce electrons and positrons respectively.
A synthetic radioisotope is a radionuclide that is not found in nature: no natural process or mechanism exists which produces it, or it is so unstable that it decays away in a very short period of time. Examples include technetium-99 and promethium-146. Many of these are found in, and harvested from, spent nuclear fuel assemblies. Some must be manufactured in particle accelerators.
Ionizing radiation (US) (or ionising radiation [UK]), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel up to 99% of the speed of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.
A radioisotope thermoelectric generator, sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This type of generator has no moving parts and is ideal for deployment in remote and harsh environments for extended periods with no risk of parts wearing out or malfunctioning.
Nuclear chemistry is the sub-field of chemistry dealing with radioactivity, nuclear processes, and transformations in the nuclei of atoms, such as nuclear transmutation and nuclear properties.
Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is "radiology done inside out" because it records radiation emitted from within the body rather than radiation that is transmitted through the body from external sources like X-ray generators. In addition, nuclear medicine scans differ from radiology, as the emphasis is not on imaging anatomy, but on the function. For such reason, it is called a physiological imaging modality. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) scans are the two most common imaging modalities in nuclear medicine.
Radioactive contamination, also called radiological pollution, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases, where their presence is unintended or undesirable.
Radiopharmacology is radiochemistry applied to medicine and thus the pharmacology of radiopharmaceuticals. Radiopharmaceuticals are used in the field of nuclear medicine as radioactive tracers in medical imaging and in therapy for many diseases. Many radiopharmaceuticals use technetium-99m (Tc-99m) which has many useful properties as a gamma-emitting tracer nuclide. In the book Technetium a total of 31 different radiopharmaceuticals based on Tc-99m are listed for imaging and functional studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, skeleton, blood and tumors.
Phosphorus-32 (32P) is a radioactive isotope of phosphorus. The nucleus of phosphorus-32 contains 15 protons and 17 neutrons, one more neutron than the most common isotope of phosphorus, phosphorus-31. Phosphorus-32 only exists in small quantities on Earth as it has a short half-life of 14 days and so decays rapidly.
An atomic battery, nuclear battery, radioisotope battery or radioisotope generator is a device which uses energy from the decay of a radioactive isotope to generate electricity. Like nuclear reactors, they generate electricity from nuclear energy, but differ in that they do not use a chain reaction. Although commonly called batteries, they are technically not electrochemical and cannot be charged or recharged. They are very costly, but have an extremely long life and high energy density, and so they are typically used as power sources for equipment that must operate unattended for long periods of time, such as spacecraft, pacemakers, underwater systems and automated scientific stations in remote parts of the world.
Iodine-131 is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nuclear energy, medical diagnostic and treatment procedures, and natural gas production. It also plays a major role as a radioactive isotope present in nuclear fission products, and was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a large fraction of the contamination hazard in the first weeks in the Fukushima nuclear crisis. This is because 131I is a major fission product of uranium and plutonium, comprising nearly 3% of the total products of fission. See fission product yield for a comparison with other radioactive fission products. 131I is also a major fission product of uranium-233, produced from thorium.
There are 37 known isotopes of iodine (53I) from 108I to 144I; all undergo radioactive decay except 127I, which is stable. Iodine is thus a monoisotopic element.
Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2714 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisotopic and mononuclidic cobalt isotope 59
Co
. Measurable quantities are also produced as a by-product of typical nuclear power plant operation and may be detected externally when leaks occur. In the latter case the incidentally produced 60
Co
is largely the result of multiple stages of neutron activation of iron isotopes in the reactor's steel structures via the creation of its 59
Co
precursor. The simplest case of the latter would result from the activation of 58
Fe
. 60
Co
undergoes beta decay to the stable isotope nickel-60. The activated cobalt nucleus emits two gamma rays with energies of 1.17 and 1.33 MeV, hence the overall equation of the nuclear reaction is: 59
27Co
+ n → 60
27Co
→ 60
28Ni
+ e− + 2 γ
This page discusses each of the main elements in the mixture of fission products produced by nuclear fission of the common nuclear fuels uranium and plutonium. The isotopes are listed by element, in order by atomic number.
This article compares the radioactivity release and decay from the Chernobyl disaster with various other events which involved a release of uncontrolled radioactivity.
Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99, symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical radioisotope in the world.
A gamma ray, also known as gamma radiation (symbol
γ
), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays. With frequencies above 30 exahertz (3×1019 Hz) and wavelength less than 10 picometer (1×10−11 m) gamma ray photons have the highest photon energy of any form of electromagnetic radiation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their relatively strong penetration of matter; in 1900 he had already named two less penetrating types of decay radiation (discovered by Henri Becquerel) alpha rays and beta rays in ascending order of penetrating power.
Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which is different from contrast media which absorb or alter external electromagnetism or ultrasound. Radiopharmacology is the branch of pharmacology that specializes in these agents.
