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Articles by M Janik
Total Records ( 6 ) for M Janik
  A Sorimachi , T Ishikawa , M Janik and S. Tokonami
 

The National Institute of Radiological Sciences (NIRS) has developed passive radon (222Rn)–thoron (220Rn) discriminative detectors for a large-scale survey and has established a thoron chamber to calibrate such detectors. In order to establish quality assurance and quality control for the 220Rn measurement at NIRS, intercomparison studies have been carried out. The intercomparisons using a scintillation cell method, which has been used as a standard for 220Rn measurement at NIRS, were conducted at New York University (NYU, USA) and Physikalisch-Technische Bundesanstalt (PTB, Germany). As a result, it was found that the result from the NIRS was in good agreement with that from the NYU. On the other hand, it was observed that the relative discrepancy between the 220Rn concentrations from the NIRS and PTB monitors was, on average, >50 %. Using the NIRS 220Rn chamber, the international intercomparison experiment for passive 220Rn detectors started in 2008.

  R. C Ramola , G Prasad , G. S Gusain , B. S Rautela , V. M Choubey , D. V Sagar , S Tokonami , A Sorimachi , S. K Sahoo , M Janik and T. Ishikawa
 

This paper presents the preliminary results of radon and thoron measurements in the houses of Chhatrapur area of southeastern coast of Orissa, India. This area is one of the high radiation background radiation areas in India, which consists of monazite sand as the source of thoron. Both active and passive methods were employed for the measurements. Radon and thoron concentrations were measured in the houses of Chhatrapur area using twin cup radon dosemeters, RAD7 and radon–thoron discriminative detector (Raduet). Thoron progeny concentration was also measured in the houses using deposition rate measurements. Radon and thoron concentrations in the houses of study area were found to vary from 8 to 47 Bq m–3 and the below detection level to 77 Bq m–3, respectively. While thoron progeny concentration in these houses ranges between 0.17 and 4.24 Bq m–3, preliminary investigation shows that the thoron concentration is higher than radon concentration in the houses of the study area. The thoron progeny concentration was found to be comparatively higher, which forms a base for further study in the area. The comparison between the results of various techniques is presented in this paper.

  V. W. Y Choi , C. K. M Ng , R. K. K Lam , M Janik , A Sorimachi , C Kranrod , D Nikezic , S Tokonami and K. N. Yu
 

The ‘proxy equilibrium factor’ (Fp) method has been developed for long-term determination of airborne radon progeny concentrations using LR 115 solid-state nuclear track detectors. In this paper, the effects of 220Rn on the Fp method have been studied. The correction to the track density was related to a parameter which was the ratio of the sum of activity concentrations of alpha-particle emitting radionuclides in the 220Rn decay chain to the activity concentration of 220Rn alone. Under commonly encountered circumstances, could not be smaller than 2. An attempt was made to verify this using the exposure chamber at the National Institute of Radiological Sciences (NIRS), Chiba, Japan. A most interesting observation of < 2 for very high 220Rn concentrations and very low equilibrium factors for 220Rn in the exposure chambers was made. A possible explanation was the substantial deposition of 216Po under the extreme conditions inside the exposure chambers.

  S. K Sahoo , T Ishikawa , S Tokonami , A Sorimachi , C Kranrod , M Janik , M Hosoda , N. M Hassan , S Chanyotha , V. K Parami , H Yonehara and R. C. Ramola
 

Several industrial processes are known to enrich naturally occurring radioactive materials (NORM). To assess such processes with respect to their radiological relevance, characteristic parameters describing this enrichment will lead to interesting information useful to UNSCEAR. In case of mineral treatment plants, the high temperatures used in smelting and refining processes lead to high concentrations of 238U and 232Th. Also due to thermal power combustion, concentration of U and Th in the fly ash increases manifold. NORM samples were collected from a Thailand mineral treatment plant and Philippine coal-fired thermal power plants for investigation. Some studies are initiated from a high background radiation area near Gopalpur of Orissa state in India. These NORM samples were analysed by gamma-ray spectrometry as well as inductively coupled plasma mass spectrometry. The radioactivity in case of Orissa soil samples is found to be mainly contributed from thorium. This study attempts to evaluate levels of thorium activity in NORM samples.

  M Hosoda , S Tokonami , A Sorimachi , T Ishikawa , S. K Sahoo , M Furukawa , Y Shiroma , Y Yasuoka , M Janik , N Kavasi , S Uchida and M. Shimo
 

Field measurements of thoron exhalation rates have been carried out using a ZnS(Ag) scintillation detector with an accumulation chamber. The influence of soil surface temperature and moisture saturation on the thoron exhalation rate was observed. When the variation of moisture saturation was small, the soil surface temperature appeared to induce a strong effect on the thoron exhalation rate. On the other hand, when the variation of moisture saturation was large, the influence of moisture saturation appeared to be larger than the soil surface temperature. The number of data ranged over 405, and the median was estimated to be 0.79 Bq m–2 s–1. Dependence of geology on the thoron exhalation rate from the soil surface was obviously found, and a nationwide distribution map of the thoron exhalation rate from the soil surface was drawn by using these data. It was generally high in the southwest region than in the northeast region.

  M Janik , S Tokonami , C Kranrod , A Sorimachi , T Ishikawa and N. M. Hassan
 

Intercomparisons of radon/thoron detectors play an important role not only for domestic radon/thoron survey but also for international or interregional discussion about radon/thoron mapping in dwellings as well as that in the soil. For these purposes, it is necessary to improve and standardise technical methods of measurement and to verify quality assurance by intercomparisons between laboratories. Therefore, the first thoron international intercomparison was provided at the NIRS (National Institute of Radiological Sciences, Japan) thoron chamber with a 150 dm3 inner volume. In addition, a second intercomparison of radon detectors was conducted at NIRS with a 24.4 m3 inner volume walk-in radon chamber. Only etched-track detectors were used during thoron intercomparison as well as three types for the radon intercomparison: etched-track, charcoal and electret. In general, 45 % results for thoron experiment do not differ more than 20 % from the reference value of thoron concentration and 69 % for radon.

 
 
 
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