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MEASUREMENTS OF EFFECTIVE DOSES OF NATURAL BACKGROUND LEVEL OF NEUTRONS WITHETCHED-TRACK DETECTORS

Kumamoto, Yoshikazu; Noda, Yutaka

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Abstract— An etched-track method was applied for a measurement of the effective dose of natural background neutrons. Ten assemblies of polycarbonate film and 10 B were placed at the center of a rem-counter type moderator. The assemblies were put in an air-tight container in order to avoid a continuous contribution from radon. Electrochemical etching was adopted. The sensitivity of the detector was 0.21 ± 0.02 μSv pit −1 cm 2. After a period of storage of 4.3 y, the number of recorded artifact pits in the films corresponded to an effective dose rate of 0.8 ± 0.2 μSv y −1. The effective dose rate of natural background neutrons was 18.1 ± 3.6 μSv year −1 for the same period, with an artifact dose being subtracted. The total net number of etched-track pits of the present detector was 75 ± 15 when used for measuring an effective dose of natural background level neutrons for 1 mo, which gives enough counting statistics. The method can thus be applied for monitoring the effective dose of neutrons around nuclear sites and high-energy accelerator facilities.

*Division of Radiation Research, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba, 263-8555, Japan.

Manuscript received 20 July 2001;

revised manuscript received 28 February 2002, accepted 9 June 2002)

For correspondence or reprints contact: Y. Kumamoto at the above address, or email at yskumamoto@mug.biglobe.ne.jp.

© 2002 by the Health Physics Society