Measurement methods and delivery times
The delivery times indicated for all measurement methods are indicative and not binding on STUK. The delivery time of the results depends on the number and urgency of STUK's regulatory supervision tasks at the time.
Since the service measurements are carried out alongside STUK's normal supervision measurements, STUK cannot guarantee that the results of the service measurement will be delivered to the customer within the indicative delivery time.
| Method of measurement | Delivery time of the result a,b |
|---|---|
| Gamma spectrometry | approx. 1 − 2 months |
| Tritium | approx. 1 month |
| Strontium | approx. 2 − 3 months |
| Uranium | approx. 1 month |
| Polonium-210 | approx. 2 months |
| Total alpha and total beta activity | approx. 1 month |
| ICP-MS | approx. 1 month |
a) Delivery time estimated from the time the sample arrives at STUK.
b) You may request an urgent delivery for the measurement result, in which case the price is 1.5 times the normal price (urgent deliveries are subject to the availability of STUK's resources and the method chosen). For urgent deliveries, pleaser contact STUK in advance so that we can inform you of whether an urgent measurement is possible.
Methods of measurement
The radioactive substances whose concentration can be determined with a gamma spectrometer are potassium-40, cobalt-60, caesium-134, caesium-137, lead-210, radium-226, uranium-235 and uranium-238.
This method of measurement does not have strict requirements for the sample. However, when the concentration needs to be determined accurately, the sample will be measured in sample containers with a capacity of 35, 110 or approx. 500 ml. The sample must also be homogeneous. Most samples are pre-treated to meet these requirements. Pre-treatment methods include drying, grinding, incineration, compression and evaporation. If the initial sample quantity is very small (such as less than 10 grams), the accuracy of the result may be poor. The sample is measured for a period of time ranging from a few hours to 24 hours.
The method usually detects concentrations exceeding 1 becquerel per kilogram (Bq/kg) or 1 becquerel per litre (Bq/l). However, it is also possible to detect concentrations below 0.1 Bq/kg by pre-treating the sample more intensively or extending the measurement time. The result reports the radioactive substance detected, its concentration in the sample and the uncertainty of the results. The result can also state the limit of quantification for the desired substances if they were not detected in the measurement.
Tritium concentration in water is measured from a distilled sample of water by liquid scintillation counting. The limit of quantification is 1–3 becquerels per litre (Bq/l), depending on the measurement time. When sampling secretions, the sample is taken directly to measurement without distillation and the limit of quantification is approximately 6–8 becquerels per litre (Bq/l).
Determining radioactive strontium in an environmental or food sample requires not only pre-treatment but also a lengthy chemical separation before the beta activity of strontium can be measured. In addition, the analysis includes a waiting period of more than two weeks. The limit of quantification varies between 0.02 and 0.1 becquerels per litre (Bq/l) or becquerels per kilogram (Bq/kg) depending on the measurement time and the sample volume.
Radiochemical uranium and polonium analyses can performed on environmental or food samples. The sample must always be brought to a soluble form. The limit of quantification varies between 0.01 becquerels per litre (Bq/l) or becquerels per kilogram (Bq/kg) depending on the measurement time and the sample volume.
The determination of total alpha activity determines all alpha-active radioactive substances in a sample. The total alpha measurement does not indicate the activity concentrations of individual radioactive substances, only the total activity concentration of alpha emitters. For example, the total alpha activity of a drinking water sample consists of alpha emitters in the sample, such as uranium, radium and polonium. Correspondingly, the total beta activity consists of all the radioactive substances emitting beta radiation in the sample.
ICP-MS is a multi-element technique that allows the simultaneous measurement of samples with high and low concentrations, independently of the element. Due to the high measurement sensitivity, extremely low concentrations of elements can be determined from the sample accurately and repeatably.
The samples are analysed in a liquid form. Solid samples are pre-treated by wet digestion to covert them into a solution prior to analysis.
STUK offers FINAS-accredited uranium and thorium concentration analyses from several liquid and solid sample matrices.