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감마선 분광법을 이용한 지하수 중의 <sup>226</sup>Ra 분석
서범경,이길용,윤윤열,이근우,Seo, Bum-Kyoung,Lee, Kil-Yong,Yoon, Yoon-Yeol,Lee, Kune-Woo 한국분석과학회 2003 분석과학 Vol.16 No.1
시료 전처리가 필요 없는 감마선 분광분석법을 이용하여 지하수 중의 라듐 ($^{226}Ra$) 분석을 위한 측정법을 확립하였다. 방사평형된 딸핵종을 이용한 라듐의 분석 시 가장 문제가 되는 대기 중 라돈 딸핵종에 의한 바탕계수는 측정함 내부로 질소가스를 흘려주므로써 해결하였고, 라듐과 그 딸핵종들 사이의 방사평형 과정에서 생성된 라돈가스의 용기 외부로의 누출은 밀폐된 알루미늄 용기를 사용함으로써 방지할 수 있었다. 또한 측정용기 내부의 공기층에 의한 방사능 변화정도를 조사하기 위하여 임의로 공기층을 만들어 측정한 결과, 물 속에 녹은 라돈의 공기층으로의 발산에 의한 방사능 변화정도는 통상적인 측정오차인 5% 범위 이내였다. 측정 시 검출기 주위로 질소가스를 흘려줌으로서 대기 중 라돈 딸핵종에 의한 간섭을 제거하였고, 검출하한값을 0.02 Bq/L로 낮출 수 있었다. 이는 최근 US Environmental Protection Agency (EPA)에 의하여 제안된 지하수 중의$^{226}Ra$ Maximum Contaminant Level (MCL)인 0.74 Bq/L보다 충분히 작은 값으로서 감마선 분광법을 이용하여 지하수 중의 라듐을 방사능 농도를 정확히 결정할 수 있다는 것을 확인하였다. The measurement of radium ($^{226}Ra$) in the groundwater was established using ${\gamma}$-ray spectroscopy without sample preparation. The background interference by air borne radon daughter nuclides was reduced by $N_2$ gas flow into the counting chamber. Leakage of radon gas produced in the radioactive equilibrium with radium and its daughter nuclides was prevented by use of the air-tighted aluminium container. We investigated the effect of air layer in the counting container. Radioactivity variation due to emanation of radon into the air layer was within the counting error range 5%. When the nitrogen gas was flowed around the detector, peak counts of ${\gamma}$-rays from the daughters of airborne radon was decreased and detection limit was decreased to 0.02 Bq/L. The detection limit of detector was lower than 0.74 Bq/L, the $^{226}Ra$ Maximum Contaminant Level (MCL) in the groundwater proposed by US Environmental Protection Agency (EPA). It was confirmed that $^{226}Ra$ radioactivity in the groundwater could be determined by the ${\gamma}$-ray spectroscopy.
김계홍,박찬희,이근우,정종헌,서범경,Kim, Gye-Hong,Park, Chan-Hee,Lee, Kune-Woo,Jung, Chong-Hun,Seo, Bum-Kyoung 한국방사성폐기물학회 2008 방사성폐기물학회지 Vol.6 No.2
The new type phoswich detector consisting of the ZnS(Ag) and plastic scintillator for alpha/beta-ray simultaneous counting was developed for monitoring radiological contamination inside pipes. The detection performance was estimated using the PSD (pulse shape discrimination) method as a function of distance between the scintillator and radioactive source. The attenuation of particles traveling through a thin film for preventing the detector from being contaminated was experimentally estimated. It is concluded from our investigation that the phoswich detector developed can provide a sufficient alpha/beta-ray discrimination. The application of a thin film for preventing the detector from being contaminated was proven to be feasible.
동전기 제염 토양 및 콘크리트 폐기물의 시멘트 고화 특성
구대서,성현희,홍상범,서범경,Koo, Daeseo,Sung, Hyun-Hee,Hong, Sang Bum,Seo, Bum Kyoung 한국방사성폐기물학회 2018 방사성폐기물학회지 Vol.16 No.1
While using an electrokinetic method to analyze the characteristics of cement solidification of radioactive wastes from decontaminated uranium soil and concrete, the compressive strength, pH, electrical conductivity, irradiation effects, and volume expansion were measured for the solidified cement specimens. The workability of cement solidified from radioactive waste was about 170-190%. After the solidified cement was irradiated, the compressive strength decreased by about 15%, but met the criteria ($34kgf{\cdot}cm^{-2}$) of KORAD (Korea Radioactive Waste Agent). According to the results of SEM-EDS for solidified cement, the aluminum phase was well combined with cement, while the calcium phase was separated from cement. The volume of solidified cement in radioactive wastes was dependent on the waste-to-cement ratio and the amount of water, and increased by about 30% under the conditions used in this study. Therefore, it was concluded that permanent disposal of electrokinetically decontaminated radioactive wastes is appropriate.
배관류 폐기물의 베타선 오염도 측정용 플라스틱 검출기 제작 및 특성평가
김계홍,오원진,이근우,서범경,Kim Gye-Hong,Oh Won-Zin,Lee Kune-Woo,Seo Bum-Kyoung 한국방사성폐기물학회 2005 방사성폐기물학회지 Vol.3 No.3
The characterization of radiological contamination inside pipes generated during the decommission of a nuclear facility is necessary before pipes can be recycled or disposed. But, existing direct measurements of radioactive contamination level using the survey-meter can not estimate the characteristic of contamination on a local area such as the pipe inside. Moreover, the measurement of surface contamination level using the indirect methods has many problems of an application because of the difficulty of collecting sample and contamination possibility of a worker when collecting sample. In this work, plastic scintillator was simulated by using Monte Carlo simulation method for detection of beta radiation emitted from internal surfaces of small diameter pipe. Simulation results predicted the optimum thickness and geometry of plastic scintillator at which energy absorption for beta radiation was maximized. In addition, the problem of scintillator processing and transferring the detector into the pipe inside was considered when fabricating the plastic detector on the basis of simulation results. The characteristic of detector fabricated was also estimated. As a result, it was confirmed that detector capability was suitable for the measurement of contamination level. Also, the development of a detector for estimating the radiological characteristic of contamination on a local area such as the pipe inside was proven to be feasible.
한명진,남석태,이근우,서범경,Han Myeong-Jin,Nam Suk-Tae,Lee Kune-Woo,Seo Bum-Kyoung The Membrane Society of Korea 2005 멤브레인 Vol.15 No.3
방사능 오염도 측정에 사용하기 위한 이중구조 고분자막이 폴리설폰과 세륨활성화된 이트륨실리케이트(CAYS)를 이용하여 제조되었다. 제조된 막은 순수 고밀도 고분자 지지층과 이에 제막된 고분자 용액의 상전환 공정에 의해 고형화된 CAYS 함침 활성층의 이중구조로 구성된다. 제막공정에서 대기방치 공정이 생략되었을 때 CAYS를 포함하는 활성층은 전형적인 비대칭 구조를 지니며, CAYS 입자들이 고분자 구조 사이에 박혀있는 형상을 지닌다. 제막공정에서 대기에 방치하는 시간이 증가할수록 막의 형상은 스폰지 구조를 띠며 CAYS는 고분자 구조로부터 분리되어 막 내부에 셀 같은 공간에 밀집되어 존재함을 보였다. 한편, 두 충 사의 계면형상은 고분자 고형화 과정에서의 상전환 속도와 밀접한 관련되었으며, 대기방치 시간의 증가에 따라 계면의 구분이 뚜렷하게 나타나지 않았다. 방사능 탐지 특성에서 스폰지 구조를 지니는 막의 고분자 구조는 방사성핵종이 통과할 수 없는 밀집된 형상을 지니면서 탐지효율의 감소를 초래하는 것으로 나타났다. Double-layered polymer films to assay the radioactive contamination were formulated using polysulfone (PSF) and cerium activated yttrium silicate (CAYS), consisting of a dense support layer and a CAYS-holding top layer prepared via the diffusion-induced phase inversion. As the vapor exposure process was omitted, the CAYS-holding layer showed a typical asymmetric structure, with CAYS being transfixed into the polymer network spread with large macropores. With the increase in vapor exposure time before immersion, morphology of the films transformed from asymmetric to sponge-like structures, with CAYS being localized in cellular structure. The border structure between the two layers reflects the phase inversion behavior of a cast solution during the coagulation. In the radioactive detection, the polymer phase in a film holding a sponge-like structure is so dense that the radionuclides, deposited on the film, could not filter through the phase, consequently resulting in the loss in the detection efficiency of the film.