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--- orb:geiger [2016/08/06 21:43]
jeroen [Sievert Approximation]
+++ orb:geiger [2016/10/26 22:53]
jeroen
@@ Line 1: / Line 1: @@
-<note important>This page is still in progress!</note>
 ====== Geiger Counter ======
 ==== Sievert Approximation ====
-The installed Geiger counter measures only activity (counts per minute (CPM) convertible to Becquerel). As the energy of the individual impacts is not measured by the device, the dose cannot be measured. Therefore, we use an approximation to convert from counts per minute to mSv/a in order to obtain an approximate value.
+The installed Geiger counter measures only activity (counts per minute (CPM) convertible to Becquerel). As the energy of the individual impacts is not measured by the device, the dose cannot be measured; nor can the health effect be measured. As the conversion from CPM to Sv depends both on the type of radiation (which in turn depends on the type of nucleotide from which it is emitted) and the type of exposure (such as exposure through the skin or exposure through inhalation), it is impossible to calculate the health effect from the activity as the composition of the air and soil in the area of operation would have to be known a priori.
-The most critical approximation concerns the nature of the radiation. This is related to the source of the isotope. For our approximation, we choose the Cs-137 isotope. For this isotope, there are 6.5E-14 mSv/h per Bq/m3 (//Facilia AB, Rodolfo Avila, July 2006//[[http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/37/101/37101600.pdf]]).
+The value which we present for the dose is therefore to be viewed as a rough approximation. We base our conversion factor on activity measurements we obtained in Switzerland with our device and dosage values provided on a daily basis by the Swiss Government for the region on the following website: [[https://www.naz.ch/de/aktuell/tagesmittelwerte.shtml]].
-We also know that the are 0.0167 Bq per CPM and that there are 8765.76 hours in a year. The volume of our Geiger counter is 0.00002325.
-We can therefore calculate the following relation between CPM and mSv/a:
+With this method, we calculate a conversion factor of 22.4 CPM per mSv/a. On the day of our measurements, we measured an average of 22.4 CPM and the value given for Pully, the closest measurement station, was 114 nSv/hr.
-mSv/a/CPM = 6.5E-14*8765.76/0.00002325/60=4.08E-4
+We expect that this conversion factor will not be drastically different in most settings. However, as very different conversion factors can occur in certain situations, we cannot exclude that our values for doses do not correspond to the actual values.