Siwan Noh

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13.

Safety Classifications for the Fusion DEMO Plant of Korea

Regulatory requirements and industrial codes and standards (C&S) are to be compulsory top-tier prerequisites for the design and construction of the fusion DEMO plant of Korea (DEMO Plant) as it will have safety-related functions to mitigate radiation hazards to the environment. However, these prerequisites will be developed in parallel with the design and construction of DEMO Plant due to the first-of-a-kind nature of the DEMO Plant. To overcome this dilemma, a tentative set of general design criteria and classification criteria that are to be applicable for the design studies of DEMO Plant is proposed, making use of the commonalities between the DEMO Plant and existing nuclear power plants (NPPs). To determine the tentative set, the radiation release to the environment and consequences of the postulated events in the DEMO Plant are analyzed with rough approximation assuming the inherent safety of a fusion DEMO reactor. The classification criteria of the tentative set include safety class, IEEE electrical classes, quality groups, and seismic categories for the structures, systems, and components of the DEMO Plant. As it will take considerable time and substantial amounts of investment to develop the regulatory requirements and C&S, the use of ASME Section III for the design study of DEMO Plant is also proposed to make the best use of the commonalities between the DEMO Plant and existing NPPs.

Internal dosimetry for intake of 18FDG using spot urine sample

In nuclear medicine, workers handle unsealed radioactive materials. Among the materials, (18)FDG is the most widely used in PET/CT technique. Because of the short half-life of (18)F, it is very challenging to monitor internal exposure of nuclear medicine workers using in vitro bioassay. Thus, the authors developed the new in vitro bioassay methodology for short half-life nuclides. In the methodology, spot urine sample is directly used without normalisation to 1-d urine sample and the spot urinary excretion function was newly proposed. In order to estimate the intake and committed dose for workers dealing (18)FDG, biokinetic models for FDG was also developed. Using the new methodology and biokinetic model, the in vitro bioassay for workers dealing (18)FDG was successfully performed. The authors expect that this methodology will be very useful for internal monitoring of workers who deal short-lived radionuclides in the all field as well as the nuclear medicine field.

Safety classifications for the fusion DEMO plant of Korea

Regulatory requirements and industrial codes and standards are to be compulsory top-tier prerequisites for the design and construction of a power plant with nuclear technologies. As it will take considerable time and substantial amounts of investment to develop that for the fusion power plants, design studies on a fusion DEMO plant will be carried out in parallel with developing its regulatory requirements and codes and standards. To overcome this dilemma, a tentative set of general design criteria and classification criteria that are to be applicable for the design studies of the fusion DEMO plant of Korea (DEMO Plant) are proposed with the vacuum vessel pressure boundary that corresponds to the Reactor Coolant Pressure Boundary of the nuclear power plant. To determine the tentative set, the radiation release to the environment and consequences of the postulated events in DEMO Plant are analyzed with rough approximation assuming the inherent safety of a fusion DEMO reactor. The classification criteria of the tentative set include safety class, electrical class, quality group and seismic category for the components, structures and systems of DEMO Plant. Use of ASME Section III for the design study of DEMO Plant is also proposed to make the best use of the commonalities between DEMO Plant and existing nuclear power plant.