ALMA MEMO #446

Levels of radiation exposure near AOS and OSF

Seiichi Sakamoto, Satoru Iguchi, Kiyoaki Wajima,
National Astronomical Observatory of Japan;
Hideki Koshiishi, Tateo Goka, Haruhisa Matsumoto,
National Space Development Agency of Japan;
Hisashi Kitamura,
National Institute of Radiological Sciences

2003/02/12

Levels of radiation exposure in Chilean altiplano primarily due to cosmic rays were measured with pocket gamma ray dosimeters and a handy neutron rem counter. Comparison data were also taken at Antofagasta, Santiago, Mitaka, and on board the aircrafts to/from the site. Significant enhancement of dose rates was found at the ALMA site: Measured gamma ray dose rate (including ~ 0.45 mSv yr⁻¹contribution of terrestrial gamma ray) was 3.14 mSv yr⁻¹at Pampa La Bola, and 1.70 mSv yr⁻¹atSan Pedro de Atacama, respectively, whereas it was 0.99 mSv yr⁻¹at Santiago. As for the neutron component, altitude dependence is severer: Measured neutron dose rates were 0.80 mSv yr⁻¹at Pampa La Bola, and 0.25 mSv yr−1 at San Pedro de Atacama, respectively, whereas it was 0.01 mSv yr⁻¹at Santiago. These values are even higher than world average dose rates at comparable altitudes, probably reflecting enhancement of incoming primary cosmic rays near the South Atlantic Anomaly. After correction for the effects of solar activity and indoor shielding, we estimate the occupational exposure of an 8–6 turno employee to be 2.0 mSv yr⁻¹, which exceeds that of a typical worker engaged in nuclear fuel cycle.

View a pdf version of ALMA Memo #446.