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Articles by C Kranrod
Total Records ( 4 ) for C Kranrod
  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.

  C Kranrod , T Ishikawa , S Tokonami , A Sorimachi , S Chanyotha and N. Chankow
 

There is a well-known discrepancy between dosimetrically derived dose conversion factor (DCF) and epidemiologically derived DCF for radon. As the latter DCFs, International Commission on Radiological Protection (ICRP) recommends a value of ~6.4 nSv (Bq h m–3)–1 and 7.9 nSv (Bq h m–3)–1 for radon decay products (RnDP) in dwellings and workplaces, respectively. On the other hand, the dosimetric calculations based on the ICRP-66 respiratory tract model derived a DCF of 13 nSv (Bq h m–3)–1 and 17 nSv (Bq h m–3)–1 for RnDP in dwellings and workplaces, respectively, and 83 nSv (Bq h m–3)–1 for thoron decay products (TnDP) in dwellings. In addition, the DCFs derived from both approaches and UNSCEAR were applied to comparative dosimetry for two thoron-enhanced areas (cave dwellings in China and dwellings at a spa town in Japan), where the equilibrium equivalent concentration of radon and equilibrium equivalent concentration of thoron have been measured. In the case of the spa town dwellings, the dose from TnDP was larger than the dose from RnDP.

  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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