The SI unit for radiation is the Bq (Becquerel) and equals the number of= atoms inside a source that decay per second. Often, source strength is giv= en in Bq per mass unit (Bq/kg). For natural radiation, other units like ppm= , % or even pCi/g are used. One should be careful translating from Bq/kg to= ppm's. Often people overlook whether the conversion was done assuming pure= radionuclides or oxides.
The following table lists the conversion between Bq/kg to ppms
Nuclide | To %/ppm | To %/ppm oxides |
40-K | 1 Bq/kg =3D 1/316% | 1 Bq/kg =3D 1/262% K2O |
238-U | 1 Bq/kg =3D 1/12.3 ppm | 1 Bq/kg =3D 1/10.4 ppm U3O8 |
232-Th | 1 Bq/kg =3D 1/4.1 ppm | 1 Bq/kg =3D 1/3.55 ppm ThO2 <= /td> |
For conversion between becquerel (Bq) and the (much older) curie (Ci) th= e following holds:
1 Bq =3D 27 pCi =3D 2.7 x 10^{-11} Ci
1 pCi =3D 0.037 Bq
Interestingly, the Bq has the same SI unit (s^{-1}) as the Hertz= (Hz). However, the difference being that 1 Hz describes a truly periodic p= henomenon whereas the Bq is purely stochastic.
There is a difference between radioactivity of a radioactive sourc= e and the radiation dose which may result from this source. The r= adiation dose depends on the following factors:
Converting becquerel (Bq) or becquerel per kilogram (Bq/kg) to gray (Gy)= or sievert (Sv) is therefore not straightforward and often not possible. B= ecquerel is a unit for radiation, while gray and sievert are both units for= absorbed radiation dose. The gray is a physical quantity, where 1 Gy = is the deposit of 1 joule of radiation energy in 1 kg of matter or tissue. = The sievert represents the equivalent biological effect of the deposit of 1= joule of radiation energy in 1 kilogram of human tissue.