An intercomparison done at NIRS, Japan on continuous monitors for measuring 220Rn concentration. (January 2016)

• Record Type: Journal Article
• Authors: Sorimachi, Atsuyuki; Janik, Miroslaw; Tokonami, Shinji; Ishikawa, Tetsuo
• Is Part Of: Applied radiation and isotopes. Volume 107(2016:Jan.)
• Page Start: 145
• Page End: 151
• Publication Date: 2016-01
• Subjects: Calibration factor -- Electrostatic collection -- NIRS -- Thoron; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2015.10.007
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: An intercomparison for continuous monitors that measure thoron ( 220 Rn) concentration was carried out using a 220 Rn chamber of National Institute of Radiological Sciences (NIRS), Japan; eleven 220 Rn monitors (four types) from nine laboratories were evaluated. The 220 Rn detection principle was the same for the eleven instruments and one reference instrument, which were commercially available silicon semiconductor detectors using an electrostatic collection method. The intercomparison results showed that there was a negative deviation of more than 30% in measured 220 Rn concentrations given by the laboratories relative to the reference values, which were obtained by making a decay-correction during the travel of 220 Rn through the sampling assembly (sample tube, filter and drying unit) and using a calibration factor. In order to elucidate the reason for this and then to investigate factors that affect the 220 Rn concentration measured with the monitors. As a result, it was necessary to make the decay-correction, in particular, when using a drying unit with a large inner volume and to use the calibration factor in order to better estimate the 220 Rn concentration. It was also found to be better to determine a calibration factor inherent to an individual monitor, because the calibration factor values ranged from 0.75 to 2.32, depending on the flow rate of the monitor pump (0.37–1.02 L min −1 ). It was concluded from this study that a periodical calibration of the monitor and a check of the monitor flow rate during measurements are necessary to maintain a consistent quality level of the 220 Rn measurement. Highlights: An intercomparison for continuous 220 Rn monitors was conducted at NIRS. A discrepancy in 220 Rn concentration between the laboratories and reference instruments. It was necessary to make the decay-correction and to use the calibration factor. We found to be better to determine a calibration factor inherent to an individual monitor. A periodical monitor calibration and a check of the monitor flow rate are necessary.