• Nuclear Engineering and Technology
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• 제52권2호
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• pp.366-372
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• 2020

Using several accessible published data sets, we analyzed the temporal change of ¹³⁷Cs radioactivity (per unit mass of sample) in marine sediments and investigated the effect of the water content of sediment on the ¹³⁷Cs radioactivity, to understand the behavior of ¹³⁷Cs present in marine environments. The ¹³⁷Cs radioactivity in sediments decreased more slowly in the Baltic Sea (near the Chernobyl nuclear power plant) than in the ocean near the Fukushima Daiichi nuclear power plant (FDNPP). The ¹³⁷Cs radioactivity in the sediment near the FDNPP tended to increase as the water content increased, and the water content decreased at certain sampling sites near the FDNPP for several years. Additionally, the decrease in the water content contributed to 51.2% of the average ¹³⁷Cs radioactivity decrease rate for the same period. Thus, it may be necessary to monitor both the ¹³⁷Cs radioactivity and the water content for marine sediments to track the ¹³⁷Cs that was discharged from the sites of Chernobyl and Fukushima nuclear power plants where severe accidents occurred.

• 방사성폐기물학회지
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• 제19권3호
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• pp.367-386
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• 2021

The overestimation and underestimation of the radioactivity concentration of difficult-to-measure radionuclides can occur during the implementation of the scaling factor (SF) method because of the uncertainties associated with sampling, radiochemical analysis, and application of SFs. Strict regulations ensure that the SF method as an indirect method does not underestimate the radioactivity of nuclear wastes; however, there are no clear regulatory guidelines regarding the overestimation. This has been leading to the misuse of the SF methodology by stakeholders such as waste disposal licensees and regulatory bodies. Previous studies have reported instances of overestimation in statistical implementation of the SF methodology. The analysis of the two most popular linear models of the SF methodology showed that severe overestimation may occur and radioactivity concentration data must be dealt with care. Since one major source of overestimation is the use of minimum detectable activity (MDA) values as true activity values, a comparative study of instrumental techniques that could reduce the MDAs was also conducted. Thermal ionization mass spectrometry was recommended as a suitable candidate for the trace level analysis of long-lived beta-emitters such as iodine-129. Additionally, the current status of the United States and Korea was reviewed from the perspective of overestimation.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.770-780
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• 2022

In 1993 the University of Extremadura initiated the design, construction and management of the Radiological Alert Network of Extremadura (RAREx). The goal was to acquire reliable near-real-time information on the environmental radiological status in the surroundings of the Almaraz Nuclear Power Plant by measuring, mainly, the ambient dose equivalent. However, the phased development of this network has been carried out from two points of view. Firstly, there has been an increase in the number of stations comprising the network. Secondly, there has been an increase in the number of monitored parameters. As a consequence of the growth of RAREx network, large data volumes are daily generated. To face this big data paradigm, software applications have been developed and implemented in order to maintain the indispensable real-time and efficient performance of the alert network. In this paper, the description of the current status of RAREx network after 30 years of design and performance is showed. Also, the performance of the graphing software for daily assessment of the registered parameters and the automatic on real time warning notification system, which aid with the decision making process and analysis of values of possible radiological and non-radiological alterations, is briefly described in this paper.

• Environmental Analysis Health and Toxicology
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• 제1권1호
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• pp.81-86
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• 1986

$^{14}$ C로 표지된 $N^{G}$ -mono［$^{14}$ C-methyl］-L-arginine을 흰쥐에 경구투여 하여 7일동안에 66.3%의 방사능이 회수되었다. 회수된 총방사능의 86.2%는 처음 24시간내에 배설되었으며, 그 분포는 산성 물질, 염기성물질, 중성물질 및 회수된 $N^{G}$ -monomethyl-L-arginine에 서 각각 33.3%, 40.2%, 12.5% 및 0.3%이었다. 중성물질 방사능의 약 50%는 N-monomethylurea에 해당하며 이는 투여한 전체방사능의 6%이었다.

• 핵의학기술
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• 제16권2호
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• pp.99-105
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• 2012

Purpose : This study is designed to compare two parameters reflecting $^{18}F$-FDG uptake, SUV and radioactivity, for diagnosis of thyroid cancer in dual time $^{18}F$-FDG PET/CT imaging and to find which parameter is more useful to decide whether the tumor is malignant or not. Materials and Methods : We performed retrospective study for 40 patients. All patients are diagnosed as primary thyroid cancer and examined $^{18}F$-FDG PET/CT. First, we got the dispersion of scattering beam of neck and lung apex to set a background and compared each dispersion, mean value, standard deviation of maxSUV and radioactivity. Also, mean maxSUV, ${\Delta}maxSUV$, ${\Delta}maxBq$/ml(%) and radioactivity between groups according to lesion's size based on biopsy are compared with independent-sample t-test. Results : the values that were from maxSUV and radioactivity measurement technique were compensated and calculated to practical values for mean comparison and patients were divided to two groups based on tumor size, Group1 ($size{\leq}1$ cm, n=21), Group2 (size>1 cm, n=19) for accurate comparison. In Group1, maxSUV (semi-quantitative analysis) was increased from $5.64{\pm}5.85$ (1.89~17.84) at first image to $5.90{\pm}5.01$ (1.95~18.22) at second image and radioactivity (Bq/ml) (quantitative analysis) showed similar increase from $5.93{\pm}6.38$ (2.50~16.75) at first image to $6.01{\pm}5.25$ (2.66~16.58) at second image. In Group2, TFmaxSUV was $10.54{\pm}14.36$ (2.54~33.89) in true first image, TSmaxSUV was $9.85{\pm}12.88$ (2.62~26.20) in true second image separately. The maxSUV showed a significant difference in the mean comparison between the two groups (p=0.035) But, mean radioactivity (Bq/ml) was $5.93{\pm}6.38$ (4.81~40.99) in true first image, $6.01{\pm}5.25$ (4.51~36.93) in true second image and didn't show a significant difference statistically (p=0.126) Conclusion : In diagnosis of thyroid tumor, SUV and radioactivity depending on $^{18}F$-FDG uptake showed high similarity with coefficient of determination (R2=0.939) and malignant evaluation results using dual time also showed similar aspect. Radioactivity for evaluation of malignant tumor didn't show better specificity or sensitivity than maxSUV.

• Journal of Radiation Protection and Research
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• 제20권1호
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• pp.8-15
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• 1995

환경방사능 분석기술은 원자력시설의 가동중 정상 및 비정상 상태시 이상판단과 지역특성에 따른 주변환경 방사능의 특성 및 거동파악 등을 하는데 필요한 기술로 원전 가동전, 후 환경방사능량을 비교함으로서 방사능 오염 및 변화상황을 파악할 수 있다. 국내에는 현재 관련법에 따라 규제기관 및 관련기관에 의해 환경감시가 계속되어오고 있으나 분석기술에 대한 한국규격이 없으므로 분석절차가 서로 상이하고 분석결과의 상대오차율이 커서 환경방사선 감시결과에 대한 신뢰성이 떨어지고 있다. 따라서 토양시료에 대한 감마핵종 분석에 한정하여 기수행된 측정방법 및 결과 둥을 비교분석하므로서 원전주변 환경방사능 감시목적에 적합한 분석기술의 신뢰도 향상 및 상대오차율 최소화 방안을 도출하였다

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.562-571
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• 2003

발전용원자로에서 뱃치방식으로 환경으로 배출된 액체유출물 내에 함유된 방사능 평가 결과에 오차를 유발하는 시료채취, 제조, 방사능 계측, 유출물 배출체적 측정 등 다양한 인자를 분석하였다. 환경배출 방사능 평가에 포함된 많은 인자들은 단일 측정에 의해 얻어지고 환경배출 방사능의 참값을 알 수 없음에 따라, 평가결과의 오차를 예측하는 것은 원칙적으로 불가능하다. 이에 따라 1993년 ISO가 권고한 측정의 불확도 표현지침에 근거하여 액체폐기물 배출방사능에 대한 불확도 평가모델을 수립하고 가상적인 조건에 대한 액체유출물 환경배출 방사능 평가결과의 불확도를 평가하였다. 그 결과, 액체유출물을 통한 환경배출 방사능 평가결과에 불확도를 유발하는 인자의 상대적인 기여도는 배출폐액의 체적, 시료의 체적, 총방사능 계측값의 순서를 갖는 것으로 나타났다. 또한 개별 변수의 확률분포와 특성값을 토대로 몬테칼로 모사법을 적용하여 최종 환경배출 방사능 평가결과의 확률분포를 해석함으로써, 지금까지 단일 값을 평가 및 보고되었던 발전용 원자로의 액체상 방사성물질 환경배출량이 실제로는 일정한 확률분포를 갖고 있음을 확인하였다.

• 핵의학기술
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• 제14권1호
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• pp.111-114
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• 2010

양전자 방출 단층촬영은 세포의 생화학적 변화에 따른 방사성의약품의 집적 정도를 영상화함으로서 암을 조기에 진단할 수 있는 검사방법으로 알려져 있다. 이러한 집적 정도는 여러 가지 원인에 따라 발생될 수 있는 것으로 $^{18}F$-FDG 주사량, 종양의 크기, 혈중 포도당 농도 등이 있다. 본 연구에서는 집적방사능과 2D와 3D 영상 획득이 방사능 농도(kBq/mL)에 미치는 영향에 대하여 평가하고자 한다. GE Discovery STe 16 PET/CT에서 1994 NEMA PET phantom을 이용하였으며, 배후방사능과 열소의 방사능 농도비가 1:2, 1:4, 1:8, 1:10, 1:20, 1:30 표준이 되도록 하여 2D와 3D로 영상을 획득하였다. 재구성 방법으로 2D와 3D 모두에서 반복연산법으로 반복횟수 2회, 부분집합 20을 적용하였다. 그리고 CT 감쇠보정법과 획득 시간은 10분으로 설정하였다. 또한 영상분석은 열소의 중심과 배후방사능에 동일한 관심영역을 설정 한 후 각 부분의 방사능 농도를 측정하여 비교 분석하였다. 설정된 관심영역의 배후방사능과 열소의 방사능 농도 비는 2D에서 1:1.93, 1:3.86, 1:7.79, 1:8.04, 1:18.72, 1:26.90, 3D는 1:1.95, 1:3.71, 1:7.10, 1:7.49, 1:15.10, 1:23.24 값을 얻었다. 또한 표준 방사능 농도비를 기준으로 한 백분율 차이(% Difference)는 2D에서 3.50%, 3.47%, 8.12%, 8.02%, 10.58%, 11.06%로 최소 3.47%에서 최대 11.06% 차이가 있고 3D는 3.66%, 4.80%, 8.38%, 23.92%, 23.86%, 22.69%로 최소 3.66%에서 최대 23.92%까지의 차이를 나타냈다. 방사능 농도가 증가할수록 실제 집적된 방사능 농도의 차이가 커짐을 알 수 있으며, 2D가 3D보다 평균 약 10.6% 높게 집적되어 방사능 농도 변화에 영향을 적게 받는 것으로 나타났다. 따라서 임상환자의 추적 검사에서 영상 획득 방법을 변화할 시 정확한 정량 평가를 위해서 이점을 고려하여 적용하여야 한다.

• 방사선산업학회지
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• 제10권4호
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• pp.173-179
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• 2016

Coals and coal ashes, raw materials and by-products, in coal-fired power plants contain naturally occurring radioactive materials (NORM). They may give rise to internal exposure to workers due to inhalation of airborne particulates containing radioactive materials. It is necessary to characterize radioactivity concentrations of the materials for assessment of radiation dose to the workers. The objective of the present study was to analyze radioactivity concentrations of coals and by-products at four coal-fired plants in Korea. High purity germanium detector was employed for analysis of uranium series, thorium series, and potassium 40 in the materials. Radioactivity concentrations of $^{226}Ra$, $^{228}Ra$, and $^{40}K$ were $2{\sim}53Bq\;kg^{-1}$, $3{\sim}64Bq\;kg^{-1}$, and $14{\sim}431Bq\;kg^{-1}$ respectively in coal samples. For coal ashes, the radioactivity concentrations were $77{\sim}133Bq\;kg^{-1}$, $77{\sim}105Bq\;kg^{-1}$, and $252{\sim}372Bq\;kg^{-1}$ in fly ash samples and $54{\sim}91Bq\;kg^{-1}$, $46{\sim}83Bq\;kg^{-1}$, and $205{\sim}462Bq\;kg^{-1}$ in bottom ash samples. For flue gas desulfurization (FGD) gypsum, the radioactivity concentrations were $3{\sim}5Bq\;kg^{-1}$, $2{\sim}3Bq\;kg^{-1}$, and $22{\sim}47Bq\;kg^{-1}$. Radioactivity was enhanced in coal ash compared with coal due to combustion of organic matters in the coal. Radioactivity enhancement factors for $^{226}Ra$, $^{228}Ra$, and $^{40}K$ were 2.1~11.3, 2.0~13.1, and 1.4~7.4 for fly ash and 2.0~9.2, 2.0~10.0, 1.9~7.7 for bottom ash. The database established in this study can be used as basic data for internal dose assessment of workers at coal-fired power plants. In addition, the findings can be used as a basic data for development of safety standard and guide of Natural Radiation Safety Management Act.

• 지구물리
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• 제7권1호
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• pp.61-72
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• 2004

실시간으로 수집된 환경방사능 데이터 및 차량위치정보를 무선통신망을 통해 전송 받아 지도 상에 표출하고 핵종별 수집시간대별 분석 및 차량 위치별 수집데이터 분석 등의 통계분석기능과 결과물의 문서출력기능을 지원하고 다수의 감시차량 관제 및 관리가 가능한 서버 클라이언트 환경의 환경방사능 감시 차량관제 시스템을 개발하였다