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1. This specific regulation sets the control and risk management strategies to ensure radiologically safe water for drinking. It gives the practical requirements to take appropriate action related to radioactivity in drinking-water that occurs during normal situations. These situations are where there could be consumption of drinking-water containing radionuclides over extended periods of time leading to prolonged radiation exposure of individuals. Exposure could continue for many years or even over a lifetime.
8. The individual dose criterion (IDC) shall be equal to 0.1 mSv y-1 for assessing public health risks from prolonged exposure to radionuclides in drinking-water.
9. The IDC of 0.1 mSv from one year’s consumption of drinking-water shall be used for all radionuclides, regardless of whether they are of natural or artificial origin. The exposure to radionuclides in drinking-water, particularly for natural occurring radionuclides is likely to occur over a prolonged period and possibly a lifetime. In order to keep the doses at a level where the risks from this exposure pathway are very low, maintaining the doses below the IDC shall be viewed as a long-term goal.
10. The screening levels are activity concentrations that can be used to demonstrate if the IDC may be exceeded. If either of the screening levels are exceeded, the activity concentrations of individual radionuclides should be determined and compared with the guidance levels (see Table 1 below).
11. The guidance levels of radionuclide concentration in drinking water shall be established as listed below in Table 1.
13. The process for applying the guidance levels shall be established as shown in Figure 1.
(a) The screening levels are the total radioactivity present in the form of alpha and beta radiation in drinking-water. They represent activity concentrations below which no further action is re-quired and are based on the IDC of 0.1 mSv per year.
(b) The gross alpha and gross beta screening methods rely on the detection of emitted alpha or beta particles during radioactive decay of the radionuclides. They are appropriate for most situations in which radionuclides in drinking-water are likely to be found, as they detect natu-rally occurring radionuclides.
(c) The guidance levels shall be used as a trigger for further investigation and not be interpreted as a limit indicating that the drinking-water is unsafe.
(d) The guidance levels shall not apply in emergency exposure situations.
14. A level of 300 Bq m-3 of radon in tap water shall be established as reference level.
15. Levels of radon in surface water or in water that has been stored are extremely low, and dissolved radon in water is readily degassed once it is released from the tap. If there is a groundwater supply close to and directly linked to the drinking-water supply, with little or no opportunity for agitation or storage before the domestic tap is opened, it could be relevant to take account of radon in drinking-water in dwellings with high radon concentrations in indoor air from the ground.
16. New water supplies shall be sampled and analyzed for radionuclides to determine their suitability for drinking-water before design and construction.
17. For a new drinking-water supply, measurements of radionuclides in the water shall be made at the source as part of characterizing the source and determining its suitability for drinking-water. The extent of treatment that will be carried out shall also be taken into account.
18. The frequency for measuring activity concentrations of radionuclides in drinking-water shall be developed considering the available resources, if there is a potential for there to be a public health risk from radionuclides in the drinking-water and other priorities for providing safe drinking-water.
19. If both the gross alpha and gross beta screening levels are not exceeded, the individual dose criterion (IDC) of 0.1 mSv in a year shall also not be exceeded, except under exceptional circum-stances (see below). Monitoring of drinking water shall continue at the locations and frequency that has been agreed with the water quality regulator for radiological parameters.
(a) If it is suspected that the water may contain a radionuclide that will not be detected by the screening methods. Table 2 provides information on the main radionuclides that will not be detected by the gross alpha and beta screening methods. Different sources of information may indicate that radionuclides in drinking-water could be present but would not be detected e.g. other environmental monitoring data in the area and the catchment that the water is drawn from, knowledge of sites that could have led to discharges of radionuclides to the catchment and local geology. In this case, radionuclide-specific measurements should be made and compared with the relevant guidance values.
(b) There are a few naturally occurring radionuclides (notably Ra-228 and Po-210) where the IDC of 0.1 mSv per year could be exceeded, even if the screening levels are not exceeded, in the exceptional situation where these radionuclides are the only significant contributors to the to-tal activity concentration.
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