Radioactivity Analysis

Radiation sources, using radioactive materials or radiation generators, are used worldwide for a wide variety of purposes including industry, medicine, research and education. They are also used for various military purposes. Many are sealed sources, where the radioactive material is tightly contained or bound within a suitable capsule or enclosure. The risks posed by these sources and materials vary greatly depending on factors such as the radionuclide, its physical and chemical form and activity. Unless breached or leaked, sealed sources pose a risk only from external radiation exposure. However, breached or leaked sealed sources, as well as unsealed radioactive material, can lead to environmental contamination and the ingestion of radioactive material into the human body.

The risks associated with the use of radioactive materials should be limited and protected by the application of appropriate radiation safety standards. Recognizing the need for a stepwise approach to regulatory control of radiation sources, the “Action plan on the safety of radiation sources and the safety of radioactive materials” published by the International Atomic Energy Agency called for the development of a categorization.

The purpose of the resulting categorization system is to provide a simple and logical system for ranking radioactive sources according to their potential to harm human health and for classifying the applications in which these sources are used into separate categories.

The purpose of categorizing radioactive sources is to provide an internationally harmonized basis for risk-informed decision-making. It is envisaged that the categorization system will be used as an input to many activities related to the safety and security of radioactive sources, including:

• Development or improvement of international safety standards
• Developing or improving national regulatory infrastructures to meet a country's conditions
• Optimizing decisions about regulatory priorities within resource constraints
• Optimizing security measures for radioactive sources, including potential misuse
• Emergency planning and response
• Developing national strategies to improve control over radioactive sources.

Radioactive sources are used in a wide variety of applications, including industry, medicine, agriculture, research and education, and are also used in military and defense applications. Within these diverse applications, there is a range of radionuclides, forms and amounts of radioactive material that must be considered in the categorization system. High-activity sources, if not managed safely or securely, can cause serious deterministic effects on individuals within a short period of time, whereas low-activity sources are unlikely to cause such effects. The categorization system therefore provides a relative ranking and grouping of sources and applications on which decisions can be based.

In general terms, the categorization system is important for decisions, both in a retrospective sense to ensure that existing resources are brought under control or kept under control, and in a prospective sense to ensure that future resources are properly organized.

Since the discovery of radioactivity, various techniques have been developed:

• Neutron activation analysis
• Isotope dilution analysis
• Radiometric titration
• Radiochromatography
• Radioimmunoassay

Among these, the neutron activation analysis technique is the most common. This technique is based on the measurement of radiation emitted by the decay of radioactive nuclei formed by neutron irradiation of the material. The most suitable neutron source for such an application is usually a research reactor. Samples that can be analyzed with this method are from many different fields such as medicine, nutrition, biology, chemistry, forensics, environment and mining.

Neutron activation analysis can be performed in a number of ways. This depends on the element to be measured and the corresponding radiation levels, as well as the nature and extent of interference from other elements present in the sample. Most of the methods used are non-destructive, based on the detection of gamma radiation emitted by the irradiated material after or during irradiation.

Neutron activation analysis is a highly sensitive technique used to determine the presence and amounts of major, minor, and trace elements in a sample of material. This technique differs from other methods in that, unlike mass spectrometry or chromatographic methods, it relies on the nucleus of the atom and ignores the chemical formulation. This technique requires a neutron source, gamma-ray detectors, and a thorough understanding of how elements respond to neutron bombardment.

A few areas where radioactivity analysis is commonly used include:

• This method is primarily preferred in research and development studies. Approximately 65 elements can be determined at levels from one part per million to one part per trillion or lower. If the matrix to be analyzed does not become very radioactive when activated by neutrons or if unwanted radioactivity decreases rapidly, trace element groups can often be measured simultaneously.
• In forensic analysis, this method has significant experience in the forensic analysis of evidence materials. Examples of this type include bullet fragments, gunpowder residues, plastic, hair and nails, and geological materials. Comparing materials in a non-destructive manner is one of the main advantages of this technique for forensic medicine.
• High purity silica, silicon, aluminum, other materials and compounds that do not form long-lived radionuclides, cellulose air filters, and materials such as graphite are excellent matrices for high-sensitivity neutron activation analysis. Such materials can be irradiated for hours to determine many elements at subppb levels. Silicon wafers and silicon dioxide used in fiber optics are among the samples analyzed.
• In the field of radiochemical separations, extremely low amounts of some elements (e.g. iridium) can be measured using microwave digestion facilities and simple chemical separation techniques.
• In the neutron activation analysis laboratory, barium, bromine, europium, antimony, terbium and uranium elements as well as cerium, cobalt, chromium, cesium, iron, lanthanum, sodium, rubidium, scandium and thorium elements can be determined with high sensitivity in soil, sediment, rock, metal and mineral samples.
• The source of radioactivity always poses serious risks to the environment, soil, air, water and agricultural products. While the elements required for nutrition are taken from the soil, radioactive substances are also mixed with plants and therefore the food chain. Knowing the content of natural radioactive substances in foods is necessary to estimate the amount of radiation to which people are exposed as a result of consuming the food.
• Radioactivity analyses are commonly performed in solid foods, such as cereals, vegetables, dairy products and various consumer goods, and in liquid foods, such as drinking water, milk and liquid sauces.
• In environmental analyses, radioactivity analyses are always performed on air and similar gas samples or salt water, fresh water and similar liquid samples, as well as soil, sediment, sand, fauna, flora, ash and similar solid samples.
• Likewise, these analyses are needed for medical waste, industrial waste, paper, plastic and all polymer types that arise after the process.

Neutron activation analysis method is widely used in environmental control and monitoring, analysis of environmental samples, chemistry and materials science, archaeology, medicine, biology, food analysis, forensic science, history, anthropology, geology and geochemistry, industry, reference materials and quality control analysis and many other fields.

Briefly, radioactivity analysis is based on the principle of counting the characteristic gamma rays emitted by radioactive isotopes obtained by irradiating the nuclei of stable atoms in the sample with neutrons using high-resolution detectors. The analysis of the gamma spectra obtained with the counted gamma rays is performed as a result of the analysis of the elements in the sample. It is an analysis method that allows the determination of many elements (30-40 elements) at the same time under ppm. The uncertainty in element determination is at the level of 0,01 percent under suitable conditions.

Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also radioactivity analysis services.