IRR17 (28) - Sealed Sources & articles containing or embodying radioactive substances

Where a radioactive substance is used, it shall if possible be in the form of a sealed source (i.e. not dispersible). The design of any source must be so as to prevent leakage, and:

  • in the case of a sealed source, prevent leakage so far as is practicable; or
  • in the case of any unsealed source, prevent leakage so far as is reasonably practicable

Where it is appropriate, the employer must ensure that suitable tests are made at suitable intervals to detect any leakage. Typically, this test (‘leak test’) will be in the form of a ‘wipe’ made to the standard required by ISO 9978.

A record of these tests must be kept for 2 years after the source is disposed of, or until a further record is made of a subsequent test.

Where testing is appropriate under normal operating conditions the interval between tests should not be more than 2 years.

The Radiation Protection Adviser will normally be consulted by the RPS or employee to assist in determining what is ‘appropriate’. For example, it may be appropriate in certain circumstances to extend the testing interval of certain fixed gauges to meet plant maintenance schedules (which may have plant shut down every 3 years).

For older sealed sources outside their recommended working life, and normally at the request of the UK environmental regulators or on the advice of the RPA, the leak test frequency may be increased to perhaps once every 12 months. Unless otherwise known, the recommended working life of a sealed source should be assumed 5 years if no other information is provided. The integrity of the source should be assessed with a view to providing an extension to life (if justified) and what condition may be applied to such a source (i.e. examination, frequency of physical checks, leak test criteria and similar).

Note that sources outside their recommended working life will lose their special form status. This does not mean that the source is about to fail integrity, but it could have impact on:

  • The Radiation (Emergency Preparedness and Public Information) Regulations 2019 (REPPIR does not apply to special form sources. If special form status is lapsed the employer 'might' need to undertake an assessment to show that the sealed source is not dispersible under all identified hazard conditions so that the source remains outside of REPPIR requirements).
  • The transport of the source. For example, certain sources that can be carried in a Type A transport container may need to be carried in a Type B container if special form status has lapsed.

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