• 한국해양환경ㆍ에너지학회지
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• 제12권3호
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• pp.133-142
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• 2009

2009년으로 예정된 산샤댐 완공 후 인근해역에 대한 장강 유출수의 영향을 예측하기 위해 라듐 동위원소의 방사능비($^{228}Ra/^{226}Ra$)와 염분을 이용하여 북부 동중국해의 표층수를 쿠로시오수(Kuroshio Water; KW), 동중국해수(East China Sea Water; ECSW), 장강수(Changjiang Water; CW)등 세가지 단성분 수괴로 나누고, 세 단성분 사이의 혼합비를 추정하였다. 2005년 11월에 동중국해 북부해역의 32개 정점(조사선 '탐구3호'), 2006년 7월에 20개 정점(조사선 '해양 2000호'), 2006년 8월에 17개 정점(조사선 '이어도호')에서 표층해수의 시료 각 300 L씩을 망간섬유에 통과시켜 라듐을 농축하였고, $Ba(Ra)SO_4$형태로 공침된 라듐 동위원소를 감마선 분광분석법으로 측정하였다. 라듐 동위원소 방사능비와 염분을 이용하여 추정된 세 단성분의 혼합비는 풍수기에 장강수가 약 1-23%, 쿠로시오수가 0-30 %, 동중국해수는 58-100% 사이에 분포하였다. 여름철 인공위성 이미지에서 장강수 플룸이 동쪽으로 향하는 것이 관찰되듯, 이 연구에서도 장강수 혼합비가 동쪽으로 갈수록 감소하는 것이 관찰되는데 이는 이 지역에 여름에 우세한 남동계절풍에 의한 표층수의 엑크만 수송 때문이라고 생각된다. 갈수기에는 연구해역의 표층수에 장강수가 거의 포함되지 않는 것으로 나타났다. 장강수의 혼합비가 증가할수록 용존 무기질소의 농도가 증가하는 경향을 보였다. 이는 용존 무기질소의 주 공급원이 장강수임을 의미하며, 혼합곡선이 제거의 형태를 보이는 것은 장강수가 인근 해수와 혼합시에 식물플랑크톤의 섭취 같은 생물작용에 의하여 질산염이 소모되는 것으로 설명할 수 있다.

• 지질공학
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• 제26권1호
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• pp.71-78
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• 2016

이 연구는 국내 지질별 지하수내 자연방사성물질의 산출특성을 평가하기 위해 지질을 5개로 분류한 후 공간적 농도 분포, 일원분산분석 그리고 상관관계 분석을 실시하였다. 지하수중 라돈 농도는 최소 0.4 pCi/L에서 64,688 pCi/L까지 매우 넒은 범위를 나타냈다. 각 자연방사성물질의 표준편차값이 평균값보다 상회하는 것은 일부 고농도 지하수가 포함되어 있어 산술평균에 큰 영향을 주는 것으로 사료된다. 히스토그램을 통해 라돈은 전체 자료 중 53.5%가 미환경청(USEPA)의 대체최고허용농도가 초과하였고 우라늄은 30 μg/L 이상이 11.9%, 전알파는 15 pCi/L 이상이 3.5% 그리고 라듐 5 pCi/L 이상인 4개(4.5%)가 미환경청의 대체최고허용농도를 초과한 것으로 나타났다. 자연방사성물질간에 상관분석 결과 매우 낮은 결정계수가 나타나 서로 상관성이 없는 것으로 분석되었다. 결론적으로 여러 가지 변수 인해 모암인 우라늄 농도에 따른 라돈, 전알파, 라듐간의 농도는 큰 연관성이 없었다. 그러나 라돈과 우라늄은 화산암(화강암) 지역, 변성암지역 순으로 고농도를 보였고 퇴적암에선 가장 낮은 농도를 분석되었다. 또한 다른 자연방사성물질에 비해 라돈은 지질에 따라 상대적으로 크게 영향을 받는 것으로 나타났다.

• 한국산업보건학회지
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• 제27권1호
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• pp.38-45
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• 2017

Objectives: Radon may be second only to smoking as a cause of lung cancer. Radon is a colorless, tasteless radioactive gas that is formed via the radioactive decay of radium. Therefore, radon levels can build up based on the amount of radium contained in construction materials such as phospho-gypsum board or when ventilation rates are low. This study provides our findings from evaluation of radon gas at facilities and offices in an industrial complex. Methods: We evaluated the office rooms and processes of 12 manufacturing factories from May 14, 2014 to September 23, 2014. Short-term data were measured by using real-time monitoring detectors(Model 1030, Sun Nuclear Co., USA) indoors in the office buildings. The radon measurements were recorded at 30-minute intervals over approximately 48 hours. The limit of detection of this instrument is $3.7Bq/m^3$. Also, long-term data were measured by using ${\alpha}-track$ radon detectors(${\alpha}-track$, Rn-tech Co., Korea) in the office and factory buildings. Our detectors were exposed for over 90 days, resulting in a minimum detectable concentration of $7.4Bq/m^3$. Detectors were placed 150-220 cm above the floor. Results: Radon concentrations averaged $20.6{\pm}17.0Bq/m^3$($3.7-115.8Bq/m^3$) in the overall area. The monthly mean concentration of radon by building materials were in the order of gypsum>concrete>cement. Radon concentrations were measured using ${\alpha}-track$ in parallel with direct-reading radon detectors and the two metric methods for radon monitoring were compared. A t-test for the two sampling methods showed that there is no difference between the average radon concentrations(p<0.05). Most of the office buildings did not have central air-conditioning, but several rooms had window- or ceiling-mounted units. Employees could also open windows. The first, second and third floors were used mainly for office work. Conclusions: Radon levels measured during this assessment in the office rooms of buildings and processes in factories were well below the ICRP reference level of $1,000Bq/m^3$ for workplaces and also below the lower USEPA residential guideline of $148Bq/m^3$. The range of indoor annual effective dose due to radon exposure for workers working in the office and factory buildings was 0.01 to 1.45 mSv/yr. Construction materials such as phospho-gypsum board, concrete and cement were the main emission sources for workers' exposure.

• Fisheries and Aquatic Sciences
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• 제3권2호
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• pp.143-150
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• 2000

Assuming that summer surface waters in the South Sea (northern East China Sea) are formed mostly by a mixing of three source water (Changjiang Discharge Water; Kuroshio Water and Yellow Sea Surface Water) we apply optimum multiparameter (OMP) analysis to calculate the mixing ratio of each source water to a given surface water. Since OMP requires more parameters than the number of water types (three in this study), we utilize two radium isotopes of dissolved $^{226}Ra\;and\;^{228}Ra$ along with temperature and salinity. Parameter values of each source water are deduced from in situ and historical data. Results with three source of waters on the surface waters are quite promising with less than $1\%$ of unanswered portions. Results not only reproduce the measured temperature and salinity faithfully but also discern the water masses of similar T and S according to their source water mixing. Extending OMP analysis to a whole water column obviously requires more parameters because more source waters are involved in the water mass formation. Original OMP routine utilized dissolved oxygen and nutrients. However, they seem to be perturbed too much by biological activities in the case of shallow waters. We discussed the use of other potential parameters. Also the benefit of parameter substitution is briefly introduced for the future OMP application on shallow waters.

• 대한방사선치료학회지
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• 제6권1호
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• pp.56-60
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• 1994

In the past, brachytherapy was carried out mostly with radium or radon sources. Currently. use of artificially produced radionuclially produced radionuclides such as $^{137}Cs,\;^{192}Ir,\;^{198}Au,\;and\;^{125}I$ is rapidly increasing. Although electrons are often used as an alternative to interstitial implants, brachytherapy continues to remain an important mode of therapy, either alone or combined with external beam. The National Council on Radiation Protection and Measurements(NCRP) recommends that the strength of any ${\gamma}$ emitter should be specified directly in terms of exposure rate in air at a specified distance such as 1m. The air kerma strength is defined as the product of air kerma rate in 'free space' and the square of the disrance of the calibration point from the source center along the perpendicular bisector, i. e., $S_k=K_L{\times}L^2$. Where $S_K$ is the the air kerma strength and K is the air kerma rate at a specified distance L. (usually 1m). Recommended units for all kerma strength are ${\mu}Gym^{2}h^{-1}$.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.881-885
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• 2017

This work presents a new technique for discriminating between alpha particles of different energy levels. In a first study, two groups of alpha particles emitted from radium-226 and americium-241 sources were successfully separated using a CR-39 microfilm of appropriate thickness. This thickness was adjusted by chemical etching before and after irradiation so that lower-energy particles were stopped within the detector, while higher-energy particles were revealed on the back side of the detector. The number of tracks on the front side of the microfilm represented all alpha particles incident on that side from the two sources. However, the number of tracks on the back side of the microfilm represented only the long-range alpha particles of higher energy that arrived at that side. Therefore, by subtracting the number of tracks on the back side from the number of tracks on the front side, one could easily determine the number of tracks for the short-range alpha particles of lower energy that remained embedded in the microfilm. Discrimination of the two energy levels is thus achieved in a simple, fast, and reliable process.

• 한국의학물리학회지:의학물리
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• 제32권2호
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• pp.25-39
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• 2021

Brachytherapy, along with external beam radiation therapy (EBRT), is an essential and effective radiation treatment process. In brachytherapy, in contrast to EBRT, the radiation source is radioisotopes. Because these isotopes can be positioned inside or near the tumor, it is possible to protect other organs around the tumor while delivering an extremely high-dose of treatment to the tumor. Brachytherapy has a long history of more than 100 years. In the early 1900s, the radioisotopes used for brachytherapy were only radium or radon isotopes extracted from nature. Over time, however, various radioisotopes have been artificially produced. As radioisotopes have high radioactivity and miniature size, the application of brachytherapy has expanded to high-dose-rate brachytherapy. Recently, advanced treatment techniques used in EBRT, such as image guidance and intensity modulation techniques, have been applied to brachytherapy. Three-dimensional images, such as ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography are used for accurate delineation of treatment targets and normal organs. Intensity-modulated brachytherapy is anticipated to be performed in the near future, and it is anticipated that the treatment outcomes of applicable cancers will be greatly improved by this treatment's excellent dose delivery characteristics.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1757-1762
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• 2023

Radiological hazards from external exposure of naturally occurring radioactive materials (NORM) scales residues, generated during the extraction process of oil and gas production in southern Algeria, are evaluated. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were measured using high-purity gamma-ray spectrometry (GeHP). Mean activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K, found in scale samples are 4082 ± 41, 1060 ± 38 and 568 ± 36 Bq kg^-1, respectively. Radiological hazard parameters, such as radium equivalent (Ra_eq), external and internal hazard indices (H_ex, H_in), and gamma index (I_γ) are also evaluated. All hazard parameter values were greater than the permissible and recommended limits and the average annual effective dose value exceeded the dose constraint (0.3 mSv y^-1). However, for occasionally exposed workers, the dose rate of 0.65 ± 0.02 mSv y^-1 is lower than recommended limit of 1 mSv y^-1 for public.

• Nuclear Engineering and Technology
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• 제56권9호
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• pp.3898-3903
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• 2024

There is a lack of available data on the radioactivity levels of these materials, despite the potential risks they may pose to patients, dental technicians, and dentists. A total of forty samples were collected from different dental markets in Egypt. Using an NaI(Tl) detector, the gamma-ray spectrometer measured the activity levels of uranium-238, radium-226, thorium-232, and potassium-40. The findings revealed that the mean concentration of ²³⁸U (below the minimum detectable activity, MDA), ²²⁶Ra (135 ± 5 and 132 ± 5 Bq/kg), ²³²Th (187 ± 4 and 243 ± 8 Bq/kg), and ⁴⁰K (1560 ± 52 and 2501 ± 89 Bq/kg) in feldspar and zirconia (ZrO₂) dental ceramic samples, respectively, were all within the limits established by the International Organization for Standardization (ISO) and the European Commission (EC). The use of feldspar and zirconia dental ceramics to restore all teeth would result in an estimated maximum beta dose of 1.5 mGy/year to the oral tissue. The results suggest that there is no cause for concern regarding any additional beta dose to the oral cavity from the use of feldspar and zirconia dental ceramics.

• 한국방사선학회논문지
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• 제7권1호
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• pp.31-36
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• 2013

우라늄($^{238}U$)의 붕괴과정에서 생성되는 방사성기체인 라돈($^{222}Rn$)은 발생원 중 토양에서 85 % 이상으로 토양의 공극률이 클수록 토양 밖으로 방출할 수 있는 가능성이 많은 동위원소이다. 라돈으로부터 인체를 보호하기 위해서 적절한 대책을 세우는데 무엇보다도 정확한 측정기술의 개발이 선행되어야 한다. 이에 본 연구는 고순도게르마늄(HPGe) 검출기를 이용한 감마선 분광분석법으로 라돈을 측정할 경우에는 불안정한 자연방사능의 백그라운드 문제를 줄일 수 있고, 라듐과 라돈의 딸 핵종들을 방사평형에 이르게 한 후 라돈 농도를 측정하였으며, 토양시료에서의 감마선 방출핵종 및 에너지 스펙트럼을 분석하였다.