[en] In the event of a radiation emergency, it is necessary to assess intake and radiation dose for internally contaminated casualties. Bioassay methods consist of direct (in vivo) and indirect (in vitro) measurements. Direct (in vivo bioassay) methods commonly used to measure radioactive materials in the human body include whole-body counting and organ monitoring. Indirect measurements of radiation exposure (in vitro bioassay) involve measurements of excreta, such as urine, faeces, and/or blood. In this study, whole-body counting and biosample pretreatment and measurement were performed to assess the response to internal contamination under nuclear/radiological emergency conditions. First, the whole-body counting approach was validated for rapid and accurate internal contamination assessment in nuclear or radiological emergencies; validation requirements of whole-body counting were based on international standards. Our results indicated that the measurement system and procedures met international guidelines for sensitivity, accuracy, and measurement uncertainty for radionuclide detection in the human body. Second, Monte Carlo simulations were performed to improve the efficiency calibration of whole-body counter (WBC). Whole-body counting results are influenced by the subjects’ body shape, WBC detector type, and/or distribution of radionuclides in the human body. Our results indicated that the measurement geometry and material composition of BOttle Manikin ABsorber (BOMAB) phantoms well-represented the human body for stand-up-type WBC calibration purposes. For bed-scanning-type WBC, the measurement geometry and radioactive material distribution were dominant factors in calibration efficiency, thus requiring the appropriate anthropomorphic physical phantom for reliable calibration. Third, by using the whole-body counting system in the Korea Institute of Radiological Medical Sciences (KIRAMS), the potassium concentration in Korean subjects was measured to estimate the annual effective dose due to ⁴⁰K radiation. The results showed that potassium level in the body was not influenced by ethnicity or country (e.g., by variation in dietary habits), whereas sex, age, and body condition were important factors. Based on the ⁴⁰K measurement results, the annual effective dose estimates were 0.15 mSv for males and 0.13 mSv for females. Fourth, we established rapid and simple procedures for bioassay radioactivity measurements, including pretreatment of biosamples, measurement of samples, and evaluation of results. The established procedures can be applied for assessment of radionuclide intake and resulting radiation dose. Such capabilities should be made available for radiation emergency response preparedness. Based on our results, the procedures described herein will enable rapid, accurate measurement of radionuclide concentration in biosamples in the event of a radiation emergency. Lastly, we considered variability in the spot urine normalization method with respect to assessing the internal radiation dose of radiation workers who work with radiopharmaceutical products. The creatinine concentration method has commonly been used for normalization of spot urine under radiation emergency conditions. In this study, we measured and compared creatinine levels and ⁴⁰K activity. Our results showed that the ⁴⁰K activity concentration method is applicable as a complementary method for creatinine normalization in spot urine analysis in the event of nuclear or radiological emergencies. The procedures established in this study combine in vivo and in vitro bioassay assessments to accurately and rapidly assess radionuclide levels in the human body. Therefore, it is expected that the radiation dose assessment system of the KIRAMS could work effectively in mass casualty radiation emergency situations

[en] The radioactive waste oil from the nuclear industry is potentially hazardous due to the possible contamination of soils, waterways. Pollutants in waste oil are generally heavy and radioactive metals or metal oxides. These radioactive oils are highly viscous fluids that are similar to used motor oils. Several processes are developed for the regeneration of used motor oils, such as clay treatment, chemical addition, vacuum distillation and hydrofinishing. However these technologies are difficult to apply for separation of nuclides from radioactive waste oils. In recent years, a few laboratories tried to use membrane for the regeneration of used motor oils. But, the membrane filtration of viscous fluids demands high temperature to increase the permeate-flow rate. Generally, increasing the process temperature(up to 350 .deg. C), leads to decrease the fluid viscosity. Consequently, the membrane filtration of viscous fluids is difficult for commercial operation because of high energy consumption. Hence, a new method of separation of used oils which overcomes these disadvantages are urgently needed. Also we need environmentally-friendly and efficient processes for separation of used oils. This work have used supercritical CO₂ (scCO₂) as a viscosity-reducing agent at lower process temperature in order to improve the membrane permeability and thus the energy consumption in the process. scCO₂ is considered as an alternative process medium. Since, it is non-toxic, non-flammable, inexpensive and easy to handle. Additionally, the tunable properties of carbon dioxide through pressure and temperature control are versatile for use in extracting many organic materials. The membrane can be classified as microfiltration (MF: 0.01 ∼ 10 μm), ultrafiltration (UF: 1 nm ∼ 5 μm) and reverse osmosis (RO: ∼ 1nm). We have used the membrane of 0.1 μm and 7 μm pore size. Most of metals or metal ions have the size of ∼1 μm. Specially, ceramic membranes are favorable, because it can be reusable by various washing methods, such as back pressure washing. In this paper, we examine the filtering efficiency of ceramic membranes under scCO₂ and discuss about possible usages in the separation of used oils

[en] Current decontamination methods consist of many techniques such as surface decontamination, which separate contaminants from the subject surface, and melting decontamination that uses the difference of density of contaminants and that of subjects. However, most of decontamination methods produce lots of secondary wastes. We need more environmentally friendly processes for decontamination that results in the reduction of the amount of the secondary wastes. Carbon dioxide has been one of the alternative green solvents, because it is non-toxic, non-flammable, inexpensive and easy to handle. Additionally, the tunable property of carbon dioxide through pressure and temperature control is very useful for its diverse use in extracting many organic materials. However, carbon dioxide is non-polar solvent that cannot dissolve polar, ionic, or oxide contaminants. To resolve this limit of carbon dioxide solvent, we are developing CO₂. soluble chelate ligands that can extract metal ions into CO₂. TBP(tri-n-butylphosphate) is a well-known chelating ligand that can extract metallic ions such as uranium and plutonium from the nitric solution into organic solvent. TBP shows some weaknesses such as radiation instability under the strong gamma radiation and not-incinerable due to hazardous phosphate formation. We suggest another ligand, TBOD(N,N,N'N'-tetra-butyl-3-oxa-pentanediamide) for extraction of actinides and fission products. Compared to TBP, the diamide, TBOD has a high irradiation stability and a strong affinity to metallic ions, and it can be completely incinerated because TBOD consists of C, H, O and N elements only. In this paper, we examine the properties of TBOD under the supercritical CO₂ solvent conditions and discuss about possible usages in decontamination

[en] Whole-body counters are widely used to evaluate internal contamination of the internal presence of gamma-emitting radionuclides. In internal dosimetry, it is a basic requirement that quality control procedures be applied to verify the reliability of the measured results. The implementation of intercomparison programs plays an important role in quality control, and the accuracy of the calibration and the reliability of the results should be verified through intercomparison. In this study, we evaluated the reliability of 2 whole-body counting systems using 2 calibration methods. In this study, 2 whole-body counters were calibrated using a reference male bottle manikin absorption (BOMAB) phantom and a Radiation Management Corporation (RMC-II) phantom. The reliability of the whole-body counting systems was evaluated by performing an intercomparison with International Atomic Energy Agencyto assess counting efficiency according to the type of the phantom. In the analysis of counting efficiency using the BOMAB phantom, the performance criteria of the counters were satisfied. The relative bias of activity for all radionuclides was -0.16 to 0.01 in the Fastscan and -0.01 to 0.03 in the Accuscan. However, when counting efficiency was analyzed using the RMC-II phantom, the relative bias of 241Am activity was -0.49 in the Fastscan and 0.55 in the Accuscan, indicating that its performance criteria was not satisfactory. The intercomparison process demonstrated the reliability of whole-body counting systems calibrated with a BOMAB phantom. However, when the RMC-II phantom was used, the accuracy of measurements decreased for low-energy nuclides. Therefore, it appears that the RMC-II phantom should only be used for efficiency calibration for high-energy nuclides. Moreover, a novel phantom capable of matching the efficiency of the BOMAB phantom in low-energy nuclides should be developed

[en] Whole-body counters are widely used to assess internal contamination after a nuclear accident. However, it is difficult to determine radioiodine activity due to limitations in conventional calibration phantoms. Inhaled or ingested radioiodine is heterogeneously distributed in the human body, necessitating time-dependent biodistribution for the assessment of the internal contamination caused by the radioiodine intake. This study aims at calculating counting efficiencies considering the biodistribution of ¹³¹I in whole-body counting measurement. Monte Carlo simulations with computational human phantoms were performed to calculate the whole-body counting efficiency for a realistic radioiodine distribution after its intake. The biodistributions of ¹³¹I for different age groups were computed based on biokinetic models and applied to age- and gender-specific computational phantoms to estimate counting efficiency. After calculating the whole-body counting efficiencies, the efficiency correction factors were derived as the ratio of the counting efficiencies obtained by considering a heterogeneous biodistribution of ¹³¹I over time to those obtained using the BOMAB phantom assuming a homogeneous distribution.Based on the correction factors, the internal contamination caused by ¹³¹I can be assessed using wholebody counters. These correction factors can minimize the influence of the biodistribution of ¹³¹I in whole-body counting measurement and improve the accuracy of internal dose assessment

[en] As unclear industry grown, 432 of the nuclear power plants are operating and 52 of NPPs are under construction currently. Increasing use of radiation or radioisotopes in the field of industry, medical purpose and research such as non-destructive examination, computed tomography and x-ray, etc. constantly. With use of nuclear or radiation has incidence possibility for example the Fukushima NPP incident, the Goiania accident and the Chernobyl Nuclear accident. Also the risk of terror by radioactive material such as Radiological Dispersal Device(RDD) etc. In Korea, since the 'Law on protection of nuclear facilities and countermeasure for radioactive preparedness was enacted in 2003, the Korean institute of Radiological and Medical Sciences(KIRAMS) was established for the radiation emergency medical response in radiological disaster due to nuclear accident, radioactive terror and so on. Especially National Radiation Emergency Medical Center(NREMC) has the duty that is protect citizens from nuclear, radiological accidents or radiological terrors through the emergency medical preparedness. The NREMC was established by the 39-article law on physical protection of nuclear material and facilities and measures for radiological emergencies. Dose assessment or contamination survey should be performed which provide the radiological information for medical response. For this reason, the NREMC establish and re-organized dose assessment system based on the existing dose assessment system of the NREMC recently. The exposure dose could be measured by physical and biological method. With these two methods, we can have conservative dose assessment result. Therefore the NREMC established the exposure dose assessment laboratory which was re-organized laboratory space and introduced specialized equipment for dose assessment. This paper will report the establishment and operation of exposure dose assessment laboratory for radiological emergency response and discuss how to enhance international level of dose assessment system

[en] For the case of radiation emergency, it is required to assess internal contamination of the public, including children as well as adults. The objective of the present study was to assess counting efficiency of a whole body counter by human body size and standing position of the measurement person. In this study, the FASTSCAN whole body counter used at National Radiation Emergency Medical Center of Korean Institute of Radiological and Medical Science was simulated by a radiation transport computer code. The simulation results of the counting efficiencies agreed well with measurements within the 2% of discrepancy for 4-year child and 5% for adults. The standing positions of the people were adjusted by body size to find the consistent trend of the counting efficiencies by human body size. Body size scaling factors of the whole body counter were derived to consider human body size and improve the measurement accuracy. The counting efficiency assessment methodology in this study can be successively used to improve the measurement accuracy when using a whole body counter for the case of radiation emergency

[en] To extract uranium ions, we applied to N,N,N',N'-tetrabutyl-3-oxapentanediamide (TBOD) as a alternative ligand in supercritical CO₂. Generally, tributylphosphate (TBP) as an organophosphorous ligand was used to extract the uranium ions or oxides in supercritical CO₂. There are several problems such as secondary radioactive wastes and vulnerability to high radiation fields. Diamides can be completely incinerated, resulting in the advantages of no secondary wastes. Additionally, diamides have high irradiation stability and a strong affinity to metallic ions such actinides in acidic solutions. CO₂ is a good solvent for the minimization of the organic wastes because of its easy recycle. This study deals with the solubility of TBOD, TBOD-HNO₃ and TBOD-HNO₃- UO₂(VI) and the extraction of uranium ions using TBOD in supercritical CO₂

[en] It is necessary to analyze radioactivity of naturally occurring radioactive materials (NORM) in products to ensure radiological safety required by Natural Radiation Safety Management Act. The pretreatments for the existing analysis methods require high technology and time. Such destructive pretreatments including grinding and dissolution of samples make impossible to reuse products. We developed a rapid and simple procedure of radioactivity analysis for thorium series in the products containing NORM. The developed method requires non-destructive or minimized pretreatment. Radioactivity of the product without pretreatment is initially measured using gamma spectroscopy and then the measured radioactivity is adjusted by considering material composition, mass density, and geometrical shape of the product. The radioactivity adjustment can be made using scaling factors, which is derived by radiation transport Monte Carlo simulation. Necklace, bracelet, male health care product, and tile for health mat were selected as representative products for this study. The products are commonly used by the public and directly contacted with human body and thus resulting in high radiation exposure to the user. The scaling factors were derived using MCNPX code and the values ranged from 0.31 to 0.47. If radioactivity of the products is measured without pretreatment, the thorium series may be overestimated by up to 2.8 times. If scaling factors are applied, the difference in radioactivity estimates are reduced to 3-24%. The developed procedure in this study can be used for other products with various materials and shapes and thus ensuring radiological safety

[en] Operational nuclear facilities such as nuclear power plants and particle accelerators show various neutron spectra according to the type of facilities and specific position. Necessities of neutron dose management and neutron monitoring for radiation protection of radiation workers in such a kind of facilities have continuously increased in recent years. Bonner sphere spectrometers are widely used for measurement of neutron spectra. Data on response function of neutron detector, default neutron spectra and count rates of Bonner sphere spectrometer are required to obtain unfolded neutron spectra in specific workplaces. In this study, we carried out measurement of neutron spectra produced in MC50 cyclotron using Bonner sphere spectrometer with LiI scintillation detector. Additionally, we estimated quantitative data on neutron flux, mean neutron energy and ambient dose equivalent rate according to the incident proton energies and positions in MC50 cyclotron