Radiation monitoring involves the measurement of radiation dose or radionuclide contamination for reasons related to the assessment or control of exposure to radiation or radioactive substances, and the interpretation of the results. [1]
Environmental monitoring is the measurement of external dose rates due to sources in the environment or of radionuclide concentrations in environmental media.
Source monitoring is a specific term used in ionising radiation monitoring, and according to the IAEA, is the measurement of activity in radioactive material being released to the environment or of external dose rates due to sources within a facility or activity.
In this context a source is anything that may cause radiation exposure — such as by emitting ionising radiation, or releasing radioactive substances. The phrase "standard source" is also used as a de facto term in the more specific context of being a calibration standard source in ionising radiation metrology.
The methodological and technical details of the design and operation of source and environmental radiation monitoring programmes and systems for different radionuclides, environmental media and types of facility are given in IAEA Safety Standards Series No. RS–G-1.8 [2] and in IAEA Safety Reports Series No. 64. [3]
Practical radiation measurement using calibrated radiation protection instruments is essential in evaluating the effectiveness of protection measures, and in assessing the radiation dose likely to be received by individuals. The measuring instruments for radiation protection are both "installed" (in a fixed position) and portable (hand-held or transportable).
Installed instruments are fixed in positions which are known to be important in assessing the general radiation hazard in an area. Examples are installed "area" radiation monitors, Gamma interlock monitors, personnel exit monitors, and airborne particulate monitors.
The area radiation monitor will measure the ambient radiation, usually X-ray, Gamma or neutrons; these are radiations which can have significant radiation levels over a range in excess of tens of metres from their source, and thereby cover a wide area.
Gamma radiation "interlock monitors" are used in applications to prevent inadvertent exposure of workers to an excess dose by preventing personnel access to an area when a high radiation level is present. These interlock the process access directly.
Airborne contamination monitors measure the concentration of radioactive particles in the ambient air to guard against radioactive particles being ingested, or deposited in the lungs of personnel. These instruments will normally give a local alarm, but are often connected to an integrated safety system so that areas of plant can be evacuated and personnel are prevented from entering an air of high airborne contamination.
"Personnel exit monitors" (PEM) are used to monitor workers who are exiting a "contamination controlled" or potentially contaminated area. These can be in the form of hand monitors, clothing frisk probes, or whole body monitors. These monitor the surface of the workers body and clothing to check if any radioactive contamination has been deposited. These generally measure alpha or beta or gamma, or combinations of these.
The UK National Physical Laboratory publishes a good practice guide through its Ionising Radiation Metrology Forum concerning the provision of such equipment and the methodology of calculating the alarm levels to be used. [4]
Portable instruments are hand-held or transportable. The hand-held instrument is generally used as a survey meter to check an object or person in detail, or assess an area where no installed instrumentation exists. They can also be used for personnel exit monitoring or personnel contamination checks in the field. These generally measure alpha, beta or gamma, or combinations of these.
Transportable instruments are generally instruments that would have been permanently installed, but are temporarily placed in an area to provide continuous monitoring where it is likely there will be a hazard. Such instruments are often installed on trolleys to allow easy deployment, and are associated with temporary operational situations.
In the United Kingdom the HSE has issued a user guidance note on selecting the correct radiation measurement instrument for the application concerned. [5] This covers all radiation instrument technologies, and is a useful comparative guide.
A number of commonly used detection instruments are listed below.
The links should be followed for a fuller description of each.
Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.
A Geiger counter is an electronic instrument used for detecting and measuring ionizing radiation. It is widely used in applications such as radiation dosimetry, radiological protection, experimental physics and the nuclear industry.
Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes. The amount and spread of fallout is a product of the size of the weapon and the altitude at which it is detonated. Fallout may get entrained with the products of a pyrocumulus cloud and fall as black rain. This radioactive dust, usually consisting of fission products mixed with bystanding atoms that are neutron-activated by exposure, is a form of radioactive contamination.
Ionizing radiation, 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.
Medical physics deals with the application of the concepts and methods of physics to the prevention, diagnosis and treatment of human diseases with a specific goal of improving human health and well-being. Since 2008, medical physics has been included as a health profession according to International Standard Classification of Occupation of the International Labour Organization.
A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses.
Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.
Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.
Health physics, also referred to as the science of radiation protection, is the profession devoted to protecting people and their environment from potential radiation hazards, while making it possible to enjoy the beneficial uses of radiation. Health physicists normally require a four-year bachelor’s degree and qualifying experience that demonstrates a professional knowledge of the theory and application of radiation protection principles and closely related sciences. Health physicists principally work at facilities where radionuclides or other sources of ionizing radiation are used or produced; these include research, industry, education, medical facilities, nuclear power, military, environmental protection, enforcement of government regulations, and decontamination and decommissioning—the combination of education and experience for health physicists depends on the specific field in which the health physicist is engaged.
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.
In radiation physics, kerma is an acronym for "kinetic energy released per unit mass", defined as the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation in a sample of matter, divided by the mass of the sample. It is defined by the quotient .
The measurement of ionizing radiation is sometimes expressed as being a rate of counts per unit time as registered by a radiation monitoring instrument, for which counts per minute (cpm) and counts per second (cps) are commonly used quantities.
The ionization chamber is the simplest type of gaseous ionisation detector, and is widely used for the detection and measurement of many types of ionizing radiation, including X-rays, gamma rays, alpha particles and beta particles. Conventionally, the term "ionization chamber" refers exclusively to those detectors which collect all the charges created by direct ionization within the gas through the application of an electric field. It uses the discrete charges created by each interaction between the incident radiation and the gas to produce an output in the form of a small direct current. This means individual ionising events cannot be measured, so the energy of different types of radiation cannot be differentiated, but it gives a very good measurement of overall ionising effect.
Gaseous ionization detectors are radiation detection instruments used in particle physics to detect the presence of ionizing particles, and in radiation protection applications to measure ionizing radiation.
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 nickel 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− +
In health physics, whole-body counting refers to the measurement of radioactivity within the human body. The technique is primarily applicable to radioactive material that emits gamma rays. Alpha particle decays can also be detected indirectly by their coincident gamma radiation. In certain circumstances, beta emitters can be measured, but with degraded sensitivity. The instrument used is normally referred to as a whole body counter.
Survey meters in radiation protection are hand-held ionising radiation measurement instruments used to check such as personnel, equipment and the environment for radioactive contamination and ambient radiation. The hand-held survey meter is probably the most familiar radiation measuring device owing to its wide and visible use.
Radioactive sources are used for logging formation parameters. Radioactive tracers, along with the other substances in hydraulic-fracturing fluid, are sometimes used to determine the injection profile and location of fractures created by hydraulic fracturing.
A radioactive source is a known quantity of a radionuclide which emits ionizing radiation, typically one or more of the radiation types gamma rays, alpha particles, beta particles, and neutron radiation.
The Philippine Nuclear Research Institute (PNRI) is a government agency under the Department of Science and Technology mandated to undertake research and development activities in the peaceful uses of nuclear energy, institute regulations on the said uses, and carry out the enforcement of said regulations to protect the health and safety of radiation workers and the general public.
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