EFFECTIVE DOSE OF MINERS DUE TO NATURAL RADIOACTIVITY INA MANGANESE MINE IN HUNGARY N. Ka ´va ´si 1,2, *, T. Vigh 3 , A. Sorimachi 1 , T. Ishikawa 1 , S. Tokonami 1 and M. Hosoda 1 1 Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba-shi 263-8555, Japan 2 Social Organization for Radio Ecological Cleanliness, Egyetemu. 10, Veszpre ´m, Hungary 3 Manga ´n Ltd., 8409 U ´ rku ´ t, Hungary *Corresponding author: norbert@fml.nirs.go.jp In this study, short-term radon (RnDP) and thoron (TnDP) progeny measurements and dose estimation were carried out in winter and summer. Gamma-ray dose rate originating from external sources and 222 Rn and 226 Ra contents of spring-water from a mine were also measured. During working hours RnDP and TnDP concentration values changed between 12.1–175 and 0.14–0.42 Bq m 23 , respectively. The 222 Rn and 226 Ra concentration values in the karst spring-water were ∼6 Bq dm 23 and 16 mBq dm 23 , respectively. The radiation dose resulting from the consumption of karst spring-water was negligible. The doses from the inhalation of TnDP and external gamma radiation were of the same magnitude, ∼0.1 mSv y 21 , which was rather negligible related to the estimated radiation dose of 5 mSv y 21 from RnDP. INTRODUCTION The major part of the natural radiation dose in humans is received by inhaling radon ( 222 Rn) and its progenies, which originate from the decay chain of 238 U. In mines, besides other factors, attention should be paid to 222 Rn, as despite the low 226 Ra-content of the ore mined, such 222 Rn emanation and exhalation situations may occur together with low ventilation, which promote 222 Rn accumulate in the air of the mine galleries. This may even result in 222 Rn reaching such a significant level of concentration as the annual average that the increased health risk of those working underground must be taken into account (1) . In Hungary, Executive Regulation No. 16/2000 of the Ministry of Health came into effect on 1 January 2003, which identifies an annual average of 1000 Bq m –3 as the action level concerning the 222 Rn concentration of the air in workplaces (2) . In line with this, a survey of 222 Rn concentration using active and passive measuring instruments in the manganese mine in U ´ rku ´t was started in 2002 (3) . During the years since, thoron ( 220 Rn) measure- ments were also carried out, the results of which have proved the presence of 220 Rn within the range of 61–510 Bq m – 3(4) . As a consequence of these studies, the present work included the implemen- tation of short-term RnDP and TnDP concentration measurements during winter (January) and summer (August) periods, and the dose estimation of workers. Additionally, the gamma-ray dose rate originating from an external source was also measured, and after identifying the 222 Rn and 226 Ra contents of the spring-water in the mine, the dose originating from the consumption of the water was also estimated. EXPERIMENTAL METHODS 222 Rn and 226 Ra in water 222 Rn in spring-water and subterranean water was determined in situ using an RAD7 and its water measurement accessory, RAD-H 2 O. 226 Ra in water was measured using alpha-spectrometry. 226 Ra was deposited onto a polyamide disc coated with MnO 2 using 133 Ba (50 Bq) tracer. The concentration of 226 Ra was measured in a Canberra alpha-chamber with a Eurisys passivated integrated planar silicon detector. RnDP and TnDP in air RnDP and TnDP ( 218 Po, 214 Po, and 212 Bi, 212 Po) in air were identified using a Pylon WLx measuring unit in the 0.5 dm 3 min –1 flow rate mode for 60-min cycles. Gamma-ray dose rate The external gamma-ray dose rate (1 cm dose equiv- alent rate) was determined using an Aloka PDR– 101 pocket survey meter. The dose equivalent rate result was converted to the absorbed dose rate in air, using a calibration factor, and then the effective dose was calculated. Dose estimation Ingestion of 222 Rn and 226 Ra The effective dose from ingestion of 222 Rn and 226 Ra was calculated by the following equation: E ¼ DCF  I  C  t; ð1Þ # The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org Radiation Protection Dosimetry (2010), pp. 1–4 doi:10.1093/rpd/ncq253 Radiation Protection Dosimetry Advance Access published September 27, 2010 at National Institute of Radiological Science on September 27, 2010 rpd.oxfordjournals.org Downloaded from