Monitoring of radioactivity in household water

There is no need to survey tritium under regular household water monitoring, as STUK monitors the activity concentrations of tritium through the national environmental radiation monitoring programme.

The quality requirement for radon concentration is 1,000 becquerels per litre (Bq/l). If it is exceeded, mitigating actions are necessary for radiation safety reasons and always without further assessment, regardless of how the water is used. The quality target for radon is 300 Bq/l. If the quality target is not met, the need for mitigating measures is considered on the basis of a risk assessment.

In water supply areas, radon concentrations need not be investigated if the water produced as household water derives solely from a body of surface water. Radon samples are taken from the water leaving the waterworks. Radon is usually examined under intermittent monitoring. Sampling may be reduced or the monitoring may be discontinued if the results of the radon concentration test meet the condition of item 5 of Appendix II to the Decree Relating to the Quality and Monitoring of Water Intended for Human Consumption.

Indicative dose refers to the accumulation of the effective radiation dose caused by household water from natural and artificial radioactive substances received during one year. However, tritium, potassium-40, radon and short-lived disintegration products of radon are not taken into account.
The quality requirement for the indicative dose is less than 0.10 millisieverts per year (mSv/year). The level of the indicative dose may be estimated from the total alpha activity of the sample or from the activity concentrations of individual radioactive substances (radionuclides).

If the total alpha activity is less than 0.1 Bq/l and the activity concentration of radon does not exceed the quality target of 300 Bq/l, it can be assumed that the indicative dose does not exceed the level of 0.10 mSv/year. In this case, it is not necessary to determine the activity concentrations of individual radioactive substances.

If the total alpha activity exceeds 0.1 Bq/l, the activity concentrations of the individual radioactive substances in the sample are determined to assess the indicative dose. The alpha-active substances determined from the water sample may include radium-226, uranium-234, uranium-238 and polonium-210 as well as the beta-active substances radium-228 and lead-210. In exceptional cases, it may be required that other radioactive substances are also measured in the sample.

In water supply areas, the indicative dose need not be surveyed if the water produced as household water derives solely from a body of surface water. The sample for the indicative dose is taken from the water leaving the waterworks. Sampling may be reduced or the monitoring may be discontinued if the results of the test meet the condition of item 5 of Appendix II to the Decree Relating to the Quality and Monitoring of Water Intended for Human Consumption.

The indicative dose is usually examined under intermittent monitoring. The indicative dose may be examined every five years if the indicative dose is less than 0.05 mSv/year and there is no apparent reason for the indicative dose to increase. Expert advice on estimating the indicative dose is provided by STUK ([email protected]).