The alpha and beta emitter measurement system in INER

An alpha/beta emitter measurement system used to calibrate surface sources following the guidelines of ISO 8769 has been established in Institute of Nuclear Energy Research (INER) around the year 2000. This system consists of a windowless proportional counter with a uniformity of 0.28% when measuring the emission rate of a source on a centered area of 100 mm×150 mm, and a uniformity of 0.62% when the source area was 150 mm×200 mm. Four 100 mm×150 mm sources (90Sr+90Y, 36Cl, 14C and 241Am) had been measured by this system. The measurement results of the above four sources when compared with those of National Physical Laboratory, UK (NPL) showed difference between the two laboratories of <1%.