Waste Technology Section
Source Recovery
What is a Sealed Source?
A sealed radioactive source is a small container of encapsulated radioactive material, which usually has the appearance of a small, harmless piece of metal. In more technical terms, it is radioactive material that is (a) permanently sealed in a capsule or (b) closely bonded and in a solid form. The capsule or material of a sealed source is strong enough to maintain leak tightness under the conditions of use for which the source was designed, and also under foreseeable mishaps. Such sources usually have high radioactivity concentrated in a small volume (high specific activity) . If lost, and not properly controlled the sources could fall into the wrong hands which could present a risk to public health and the environment, and possibly significant social and economic disruptions.
Why use a sealed source?
The first use of a sealed source dates back to 1901. Until the 1940s sources were made only using naturally occurring isotopes (radium and polonium). Today sealed sources are made of numerous radioisotopes. Such sources are used in various human activities (e.g. medicine, agriculture, industry, transportation, construction, geology, mining, research, etc.). In most of these areas the use of these sources either cannot be replaced by other methods or provides results that are unmatched by other methods.
IAEA Nuclear Security Series No. 5, "Identification of Radioactive Sources and Devices" 
(File=4.7 MB) provides several examples of different types of sources and devices.
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Source Uses in Process Industry - Level Measurement; - Measurement of Minimum and - Density measurement; - Process control (material
In normal and extreme process conditions, e.g.: - High pressure; - High temperatures; - Toxicity; - Abrasion; - Viscosity.
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Where and how many sealed sources exist?
Sealed sources are in use worldwide. It is estimated that several million individual sources exist in various countries. By far the largest numbers are located in the developed countries. Most sources are shipped to countries through direct sale, many however, have been provided by donations, international cooperation programmes and medical practitioners joint activities. International engineering firms have brought, in the course of their work, a considerable number of sealed sources to developing countries.