What is the difference between estimation and evaluation of TID?

The total indicative dose TID (mSv/y) is related with volume activities of radionuclides in water ci (Bq/L) by the equation:

where:

hi            dose conversion factor (µSv/Bq) for ingestion of radionuclides by adult members of the public (see Tab. I)

Di            indicative dose (mSv/y) from i-th radionuclide with volume activity 1 Bq/L (Di = 0.73 . hi)

Conservative estimate of TIDe can be evaluated from gross alpha activity cα and gross beta activity corrected for potassium-40 activity cβ according to the equation

where factor 0.17 corresponds to Di for 232Th and factor 0.50 corresponds to Di for 228Ra. Actual TID is always less than its estimate TIDe, because also other radionuclides are present with lower values of factor Di.

Why there are different LoD and UM for different samples in radiology?

The measurement of radiation has a statistic nature and Uncertainty of Measurement (UM) is evaluated for each measurement and as well as LoD. That is why the values of LOR and UM are only informative and actual values are reported. UM and LoD is influenced by the amount of sample, by the time of measurement, by the time of background measurement, by the value of background, by the detection efficiency etc. When I use in gamma-spectrometry detector with higher efficiency, the sample can be measured shorter time.

Has the sample salinity influence on the measurement of GAA and GBA?

Both methods are screening methods where the evaporated sample residue is measured. That is why the LoD’s for saline samples are higher because smaller volume of the sample can be analyzed. In the case of GAA there exists special method for saline and sea waters, based on the coprecipitation of radionuclides emitting alpha radiation with BaSO₄ and Fe(OH)₃.

Our company needs to determine ²¹⁴Pb and ²¹⁴Bi in water. Could you do that ?

At the first look, this requirement is strange and demands a short consultation with the client. To generalize, some requests involve the determination of short-term decay products of some radionuclides, which are in radioactive equilibrium with its parent radionuclide. In this particular case, ²¹⁴Pb and ²¹⁴Bi, daughter radionuclides of ²²²Rn .

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