DEVELOPMENT OF BETA-RAY SURVEY METER FOR MEASURING DIRECTLY ABSORBED DOSE-RATE

A new type β-ray survey meter was developed, which could be used for measuring the β-ray absorbed dose rate of the skin (epidermal thickness is 7 mg/cm2) and of fingers (40 mg/cm2) almost independently of β-ray maximum energy. The survey meter is also used for monitoring a surface contamination. The detector of the survey meter is a plastic scintillator (40 mm ø × 2 mmt, effective opening diameter for β-rays is 38 mm ø). In dose rate measurement, the dose sensitivity of the survey meter (counting rate per absorbed dose rate) was constant within ± 10% with maximum energy more than 0.4 MeV. The measurable ranges of the absorbed dose rate of the skin and of fingers were from 3.1 × 10-2 to 103 mrad/h and from 1.7 × 10-2 to 103 mrad/h, respectively. In surface contamination monitoring, the measurable range was from 1.9 × 10-1 to 1.7 × 103 β-particles/cm2-s (2π solid angle), assuming the uniform contamination with natural uranium covered with an aluminum filter (27 mg/cm2) for shielding low energy β-rays of 234Th and α-rays. © 1979, Atomic Energy Society of Japan. All rights reserved.