Where and when is measuring necessary?
The meter used in radiation measurement has to be suitable for measuring the type of radiation in question. It has to be ensured as well that the measurement result is sufficiently reliable for the purpose.
Radiation measurement is necessary in many different places and for a variety of reasons. Meters are made subject to different requirements in different situations as regards accuracy as well as other matters. These requirements can be found in Guide ST 1.9. It must always be ensured, however, that the meter used is suitable for measuring the type of radiation in question and that the measurement result is sufficiently reliable for the purpose.
Monitoring of working conditions
Radiation measurements are an essential part of the monitoring of working conditions. The measurement results must be recorded and they must be available for the assessment of the safety of the working conditions and employee doses. Based on the measurements carried out for the purpose of monitoring working conditions, it can be ascertained that employees have been classified to the correct radiation work category.
The monitoring of working conditions includes the necessary dose rate measurements as well as surface and air contamination measurements. The monitoring of working conditions and individual monitoring are described in more detail in Guide ST 7.1.
Individual monitoring of employees in use of radiation and nuclear energy
The amount of radiation exposure of persons working with radiation sources must always be evaluated in advance and, if necessary, measured during work. Individual monitoring, or the determination of an employee’s dose with a personal dose measurement, must be organized for all category A workers, at least. Often it is appropriate to organize it for those in category B as well.
Individual monitoring measurements must be performed by an approved dosimetric service and their results are recorded in the dose register.
Exposure in various industries and different duties varies greatly. Employees can also influence the degree of their own exposure with their own working practices and by using the necessary protective equipment carefully.
Radon at workplaces
Sometimes the radon gas in the air causes radiation exposure to employees to such an extent that it becomes necessary to assess the amount of the exposure and, in some cases, to determine it for each employee.
Radon measurements must be performed using a measurement method or device that has been approved by the Radiation and Nuclear Safety Authority. The execution, timing and other considerations regarding radon measurements are described in more detail under the Practices Causing Exposure to Natural Radiation section on STUK’s website.
Aviation operations
Cosmic radiation causes exposure to aviation employees. It is difficult to measure this exposure accurately but several calculation programmes that are based on mathematical models have been developed to estimate it. Using these, it is possible to determine the radiation exposure of each employee with sufficient accuracy.
The date, departure and arrival fields as well as the profile of the flight are entered into the calculation programmes. Based on this information, the calculation programme takes into consideration all factors relevant to the dose, such as the flying altitude, latitude and longitude as well as the variations in solar activity.
Patient doses and quality assurance in health care
It must be possible to determine the radiation exposure suffered by a patient due to X-ray examination, if necessary. In order to determine the radiation exposure, it must be possible to ascertain the examination procedures (such as the radiation quality used, imaging distance) afterwards. On the other hand, in many cases a dose reading indicating the radiation exposure that can be utilized in determining the radiation exposure suffered by a patient is available in modern equipment. In such cases, it is important that the accuracy of the dose display is ensured at an adequate level during the technical quality assurance of the equipment. Further information about measuring the dose-area product (DAP) and methods for calibrating DAP meters at their locations of use have been presented in the guide, published by STUK, “Annoksen ja pinta-alan tulon mittaaminen. DAP-mittarin kalibrointi röntgensäteilykeilassa” (Measurement of dose-area product. DAP meter calibration in X-ray radiation beam).
Environmental radiation measurements
STUK monitors radiation in the environment in a number of ways, for example with an automatic measuring network as well as by measuring radioactivity in foodstuffs and natural products. The objective is to be constantly aware of the radiation to which the people and the environment in Finland are exposed. Results of radiation monitoring are published on STUK’s website.