MEASUREMENT OF AMBIENT DOSE-EQUIVALENT USING A NAI(TL) SCINTILLATION DETECTOR

Ambient dose equivalent rates for terrestrial radiation fields were me asured by a 3 '' diam. x 3 '' NaI(TI) scintillation spectrometer. The factor for converting the measured pulse height spectrum of the NaI(Tl ) scintillation detector to ambient dose equivalent was calculated usi ng the response matrix of the detector. The relationship between air k erma rates and ambient dose equivalent rates for the measured terrestr ial radiation fields at different locations was found to be H(10)=1.2 1 K-a, + 1.26 where H(10) is ambient dose equivalent rate in nSv.h(-1 ) and K-a is air kerma rate in nGy.h(-1). This linear relationship com es mainly from the facts that the ratio H(10)/K-a for monoenergetic p hotons in the energy range from 300 keV to 3 MeV falls within 1.2 +/- 10% and the effective energy of the terrestrial fields is usually with in the above range. Ambient dose equivalent rate for the measured terr estrial field can be estimated using this formula within an error of /-7% from the measured air kerma rate in the range 80 similar to 280 n Gy.h(-1).