IRR17 (20) - Monitoring of Designated Areas
Published: Sep 29, 2021
This regulation requires adequate routine monitoring of the levels of radiation and radioactive contamination, other than by the use of personal dosimeters (which is covered later), in order to determine the efficiency of the measures employed to control exposure.
Regardless of the type or extent of the monitoring required, an important part of the RPS role is to ensure such checks are carried out in an efficient and timely manner – and in accordance with local rules. This does not necessarily mean that the RPS should undertaken the monitoring.
What constitutes adequate monitoring depends on many factors including the nature and extent of the ionising radiations present, the process being undertaken and the output of a suitable and sufficient risk assessment. For example, surface contamination monitoring does not need to be undertaken in an area where only x-ray generators are used.
Furthermore, the detection of direct radiation leakage (not contamination) from such x-rays generators requires different techniques than those which might be employed to measure contamination (e.g. narrow beam vs. contamination spread, small point source detector vs. large area contamination monitor, x-rays vs. alpha particles).
Regardless of the nature of the ionising radiation source, the following needs to be considered:
- What kinds of measurements should be made (e.g. dose rate, air concentration, surface contamination)
- Where the measurements should be made
- How frequently, or on what occasions should they be made
- Method of measurement (type of instrument, sampling technique)
- Who should make the measurements (RPS, radiation users, Radiation Protection Adviser)
- What records should be kept and for how long
- Reference levels and the actions to be taken should they be exceeded (to be specified in local rules)
- When monitoring procedures should be reviewed
External radiation vs. Internal radiation hazards
For areas designated on the basis of external radiation, monitoring should include measurement of dose rates, averaged over a suitable period if necessary.
This is very important, for example, when deciding what exposure potential is derived from an x-ray security scanner. It may well be that the dose rate measured from the opening of such a device exceeds 7.5 micro Sv/h instantaneously at the moment of measurement, but when averaged over the minute may be equivalent to < 1 micro Sv/h.
For areas designated on the basis of internal radiation, monitoring should include, as appropriate, measurements of air concentration and surface contamination. In either case the monitoring regime should be adequate to indicate whether levels are satisfactory for the continuation of the work, and to detect the breakdown of control systems.
Sometimes monitoring is used to prove the negative rather than measure a positive dose rate above background. Therefore even where no controlled area exists (e.g. around the outside of a fully shielded x-ray cabinet), it might be appropriate to use a radiation monitor to demonstrate that the controlled area is still adequately shielded.
Monitoring equipment - suitability and selection
It is important that those carrying out the monitoring have a proper understanding of the capabilities and restrictions of the equipment they are using and know how to interpret the results. This is one particular area where there is a mandatory requirement for the employer working with ionising radiation to consult with the RPA. See IRR17 (14) Radiation Protection Adviser for advice on mandatory consultation of the RPA.
Particular issues to take into account include:
- The monitoring equipment must be suitable for the type, nature, intensity and energy of the radiation being monitored. Using the wrong type of monitor is akin to being blind or at the very least only seeing in black and white. You will not ‘see’ the whole picture, and in many cases, you will not see anything at all.
- Monitoring equipment used in any designated area (and this should be extended to whenever a source of ionising radiation needs to be quantified) must have been appropriately tested within the preceding 12 months. Furthermore, a new piece of equipment should be appropriately tested and calibrated by a suitably qualified person. Larger organisations are likely to have such a person internally, whereas for small users it’s often necessary to look for such services externally.
Records of monitoring should include the instrument used, date, time, location of monitoring, background measurement (if appropriate), the monitoring results and an indication if levels are being approached where remedial action will be necessary. Zero / background results should always be recorded.
An important objective of the monitoring process is to determine if the correct designation is being employed (e.g. Supervised or Controlled).
All monitoring records should be kept for at least 2 years. However, it is recommended that they are kept for as long as is reasonably practicable, and in any case not destroyed until consideration is given to duties under environmental legislation (as this applies to radioactive materials).
Interaction between IRR17 and environmental legislation
In considering the above matters it is important to note that there is significant overlapping between the IRR17 requirements, and those in the permits / registrations / authorisations issued under Environmental Permitting (England / Wales) Regulations 2018 / Environmental Authorisations (Scotland) Regulations 2018 / Radioactive Substances Act 1993 (Amendment) Regulations (Northern Ireland) 2011. Monitoring areas to determine contamination levels, clearance monitoring to allow free release of material to the environment (as non-radioactive), evaluation of ‘exempt’ or ‘out-of-scope’, and measurements to determine aqueous disposal activity down a sink are all examples of where monitoring will have both safety and environmental purpose.