Verification of cosmic radiation dose rates at the summit of Mt.Fuji

From the 2007 fiscal year, the National Institute of Radiological Sciences (NIRS) has supported the assessment of cosmic radiation exposure of aircraft crew working for Japanese airline companies, according to the guideline settled on at April 2006 by the Radiation Council of the Japanese government. The radiation doses of crew are estimated using a recently developed program for calculation of aviation route doses JISCARD EX which has employed a PHITS-based analytical model PARMA. For reliable assessments, precision of calculated doses are desirably to be verified by measurements at high altitude..We thus measured cosmic radiation at the summit of Mt. Fuji (3,776m in altitude), the highest mountain in Japan, for comparison of dose rates with model calculations. Measurements during the summer from July to August were carried out repeatedly three times on 2007, 2008 and 2009 in a building of the Mt.Fuji weather station using selected radiation monitors such as several types of neutron monitor, phoswich scintillation detectors and an ionizing chamber coupled each with an exclusive data logger.As results, ambient dose equivalent rates measured for the solar minimum agreed well with model calculations. Possible systematic errors attributing to the uncertain spectra of high-energy cosmic-ray components are discussed according to separated signals of the scintillation detector.11th Neutron and Ion Dosimetry Symposium (NEUDOS-11