Radiation Sources Safety

A radiation source must provide the highest possible integrity for its contents, together with the minimum attenuation of the emitted radiation by the encapsulation materials. Safety, however, must always be the prime consideration.

The International Organization for Standardization have issued standard (ISO 2919:1999), which establishes a sealed radioactive source classification system based on test performance. This standard also specifies production tests, markings, and gives an example of a test report. Similar standards are ANSI/HPS N43.6-1997 published in the United States.

These standards, to quote from ISO2919, "…provides a set of tests by which the manufacturer of sealed radioactive sources can evaluate the safety of those products in use, and by which the user of such radioactive sources can select types which are suitable for the required application, especially where the release of radioactive material with consequent exposure to ionizing radiation is concerned."

The suitability and safety of a source will depend on the intended application and the environment of use of which there will be a wide range. It is the customer's responsibility to ensure the source and its specification is suitable and safe for his particular application and environment of use. This applies to standard products or custom made designs.

The information given here is intended as guidance. It is recommended that the standards be consulted for detailed definitive information.

• Temperature Test - 20 min at -40°C up to 800°C (for 1 hour) and thermal stock to 20°C

• External Pressure Test - from 25kPa absolute raise to 170MPa absolute

• Impact Test - The source, positioned on a steel anvil, is struck by a steel hammer of the required weight; the hammer has a flat striking surface, 25mm diameter, with the edges rounded.

• Vibration Test - 25 to 80Hz at 1.5mm amplitude peak to peak and 80 to 2000Hz at 196 m/s² 20 gn (repeat 3 times for 30 min each)

• Puncture Test - The source, positioned on a hardened steel anvil, is struck by a hardened pin, 6mm long, 3mm diameter, with hemispherical end, fixed to a hammer of the required weight.

Each test can be applied in several degrees of severity, which is expressed as a five digit code representing the class numbers which describe the performance for each of the tests. The digits are preceded by the letter C or E indication respectively, whether the activity of the source is greater or less than the prescribed amount.

The limits depend on the toxicity etc of the active components. Test compliance is determined by the ability of the sealed radiation source to maintain its leak tightness. Leakage tests are defined in ISO 9978.

IAEA Special Form

Sealed sources which have passed the performance tests described in the regulations for the Safe Transport of Radioactive Material, 1996 Edition (Revised), International Atomic Energy Agency (IAEA), No. TS-R-1 (ST-1, Revised) may be approved as Special Form Material by a National Competent Authority.

Designation as Special Form allows an increase in the activity limits for shipment as a Type A package.