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Open radioactive sources/unsealed radioactive material


Depending on the area of use and the amount of radioactivity, the use of open radioactive sources may subject to authorisation according to section 5 of the Radiation Protection Regulations, as well as a possible obligation to notification under section 6.


Areas of use

The term “open radioactive sources” means radioactive material that is not sealed. The so-called sealed radioactive sources are the counterpart to this, whereby the radioactive material is encapsulated in order to prevent the diffusion of the radioactive material to the surroundings, often in form of a steel capsule around the radioactive material. The radioactive material in open sources typically appears in liquid or gas form, and in some cases, also as powder.

Open radioactive sources are used in a number of areas in industry, research, medical diagnostics and therapy, and so forth. A common use of open radioactive sources in industry and research is for the purpose of conducting so-called tracer studies, that is, the open radioactive sources are used to follow one or another physical, chemical or biological process. The radiation from radioactive material is usually relatively straightforward to measure, and even the presence of tiny amounts (trace amounts) of radioactive material can be detected. By marking different molecules with appropriate radioactive elements, these molecules can literally be tracked through different processes. For example, tritium-marked (H-3) water (HTO) can be used to follow ground water movements, and the marking of proteins can be used to follow the decomposition of nutrients in biological systems.

Tracer studies. Photo: NRPA.

The principle of use in medical diagnostics is generally the same as in general tracer studies, that is, to track the chemical and physiological processes in the patient by injecting different kinds of radioactive solutions into the body.

The radioactive source and radiation protection
There are a large number of radioactive nuclides that are actively used as open radioactive sources in several different areas of use, and factors such as chemical element, type of radiation (alpha, beta or gamma), half-life and so on, all play a role in the choice of source type. In order to follow relatively rapid processes with a time scale of hours and days, nuclides with short half-lives (hours and days) should be used from a radiation protection perspective.

Furthermore, because the source should not be encapsulated, the use of radioactive substances with low penetrating beta radiation such as for example H-3, is preferable. With respect to the use of sealed radioactive sources, there will always be a preponderance of short-lived isotopes and isotopes with low penetrating radiation among the open sources.

Radiation protection when using open sources is essentially the same as for sealed sources, but use of open sources carries the additional risk of spilling (contamination) and unintended intake of the radioactive substance through the mouth and nose. Certain uses of open radioactive sources also result in releases to the surrounding environment.

Requirement for authorisation and notification
Depending on the area of use and the amount of radioactivity, the use of open radioactive sources may subject to authorisation according to section 5 of the Radiation Protection Regulations, as well as a possible obligation to notification under section 6. Typical areas of use for open radioactive sources requiring authorisation are:
  • Section 5 d) radiation use for research purposes;
  • Section 5 e) administration of radioactive medicines or substances to persons in connection with medical diagnostics, treatment or research (nuclear medicine); 
  • Section 5 l) use of open radioactive sources for tracer studies outside the laboratory;
  • Section 5 n) use of open radioactive sources of activity levels requiring a type A isotope laboratory; 
  • Section 5 o) discharges of radioactive substances.

Other use of open radioactive sources requiring written notification to NRPA according to section 6 of the regulations, assuming that the amounts that are used exceed the exemption levels specified in the annex to the Radiation Protection Regulations.

Application for authorisation: