MONITORING PROGRAMME
7.1. Paragraph 3.96 of GSR Part 3 [9] states that: “Registrants and licensees…
shall establish, maintain and keep under review a programme for workplace monitoring under the supervision of a radiation protection officer or qualified expert.”
7.2. The programme for workplace monitoring should be designed to assess the adequacy of the arrangements in place for protection and safety for facilities and activities involving nuclear gauges. The programme should include measurements of dose rate at the following positions:
(a) Around storage facilities for gauges and sources, to ensure that an adequate level of shielding is provided;
(b) Around gauges during routine operations, to confirm that dose rates remain below any values specified in national regulations or guidance and by the operating organization;
(c) Around gauges during maintenance operations, to confirm that the gauge shutter is closed or that the radiation generator is switched off;
(d) At the operators’ positions during use of portable gauges, to confirm that radiation levels are acceptable;
(e) At the operators’ positions during source loading and unloading operations;
(f) At the entrance to a gauge enclosure, to confirm that the gauge shutter is closed or that the radiation generator has ceased to emit radiation;
(g) Around the transport package before transporting a portable gauge to and from the site, to confirm the presence of the source;
(h) Around vehicles transporting portable gauges before departure to and from the site.
7.3. Measurements of radioactive contamination should not normally be necessary; however, such measurements might be appropriate if there is reason to suspect that a sealed source encapsulation has been damaged or is leaking.
7.4. The workplace monitoring programme should describe the locations to be monitored, the frequency of monitoring and the records to be kept. This information should be included in the local rules and should also be described in the radiation protection programme. Dose rate investigation levels (see para. 4.29) for each measurement location should be prescribed, and the actions to be taken if these values are exceeded should be specified. Records of the workplace monitoring programme are required to be made available to appropriate persons, including workers and the regulatory body (see paras 2.45 and 3.98 of GSR Part 3 [9]).
SELECTION, MAINTENANCE AND CALIBRATION OF WORKPLACE MONITORING INSTRUMENTS
7.5. The operating organization should ensure that a sufficient number of suitable dose rate monitors are made available. While there are many types of monitor for measuring gamma radiation levels, some might not be suitable for accurately measuring low energy photons (e.g. from X ray gauges), which could result in a significant underestimation of the dose rate. Monitors should be calibrated in terms of the radiation fields likely to be encountered in the workplace. Specialized monitoring instruments are necessary for the measurement of beta radiation and for the measurement of neutron radiation. Information and guidance on the suitability
7.6. The operating organization should arrange for workplace monitoring instruments to be formally tested or calibrated at periodic intervals by a specialized testing laboratory. A number of operating characteristics of the workplace monitoring instrument should be assessed in these tests or calibrations. These operating characteristics include the response to known dose rates at specific energies, the linearity of the response, and the behaviour of the monitor at low dose rates and at very high dose rates. The frequency and the type of tests or calibration, together with the associated record keeping, should comply with regulatory requirements, or else they should be as recommended in appropriate international standards or guidelines. The recommendations of the manufacturer of the workplace monitoring instruments should also be taken into account.
7.7. The operating organization should prepare a procedure for undertaking routine operational checks of workplace monitoring instruments. These checks might include physical checks (i.e. of whether the instrument is damaged), battery checks and, if applicable, zeroing of the scale. The response of the monitor to radiation should be checked before use. This can be done, for example, by using a low activity test source of which the characteristics are well known, or by placing the monitor close to the surface of a nuclear gauge housing when the source is in its shielded position. The regulatory body may require that such checks be performed in accordance with formal procedures and that the results be recorded.
7.8. Account should also be taken of the environmental conditions in which workplace monitoring instruments are to be used. Some instruments are unsuitable for use in very humid or very hot locations, and some are not robust enough for use on industrial sites. On some sites, special types of workplace monitoring instrument might have to be used. For example, on some petrochemical sites, only monitoring instruments that are designed to minimize the likelihood of accidental ignition of flammable fumes or vapours (‘intrinsically safe monitoring instruments’) are allowed to be used.
7.9. Some workplace monitoring instruments are affected by radiofrequency transmissions. If radiation monitoring is to be conducted close to equipment that generates high levels of radiofrequency radiation, then the use of specially designed radiofrequency shielded instruments should be considered.
7.10. Account should also be taken of noise levels in the workplace. The audible signals from workplace monitoring instruments should be loud enough to be heard and they should be supplemented by vibration or visible signals, as appropriate.