• Restorative Dentistry and Endodontics
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• 제13권1호
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• pp.185-190
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• 1988

The study was designed to establish quantitative method for assessing the marginal leakage of dental restorations. 18 Class V cavities with $45^{\circ}$ bevel joint were prepared and replicas of these teeth were made with polyethylene wax. and classified with three groups. First group was filled with Scotch bond and silux. Second group was filled with glass ionomer cement:scotchbond/silux. Third group was filled with Dentin-Adhesit/Heliosit. After finishing, all specimens were subjected manually to 100 thermal cycles at $0^{\circ}C$ and $100^{\circ}C$ Samarium nitrate solution, irradiated with flux of $6{\times}12^{12}$ neutrons/$cm^2$/sec for 11 hours, woled for 200 hours, counted with the HpGe detector and the tracer uptake was determined by comparison with a standard of samarium ($10{\mu}g$). The following results were obtained. 1) The group filled with glass ionomer cement base showed least marginal leakage. 2) The group filled with Dentin-Adhesit/Heliosit showed less marginal leakage than the group filled with scotchbond/silux.

• Restorative Dentistry and Endodontics
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• 제13권1호
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• pp.69-78
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• 1988

The study was designed to establish a more nearly quantitative method for assessing the marginal leakage of dental restorations. 27 Class V cavities with $45^{\circ}$ bevel joint were prepared and classified into 2 groups. One group was filled with Scotchbond and silux. The other group was filled with glass ionomer cement, Scotchbond and silux. After finishing, all specimens were subjected manually to 100 thermal cycles at $0^{\circ}C$ and $100^{\circ}C$ water-bath. They were soaked in a samarium nitrate solution for 3 hours, irradiated with flux of $6{\times}10^{12}$ neutrons/$cm^2$/sec for 11 hours, cooled for 200 hours, counted with the HPGE detector and the tracer uptake was determined by comparison with a standard of samarium (10 ${\mu}g$). The following results were obtained. 1. Both of the two groups showed a considerable amounts of marginal leakage. 2. The group filled without glass ionomer cement base showed more marginal leakage than the group filled with glass ionomer cement base. 3. Neutron Activation Analysis produced a good quantitative method to measure the marginal leakage and samarium was appropriate to measure the marginal leakage of resin restorations using neutron activation analysis.

• Nuclear Engineering and Technology
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• 제22권1호
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• pp.58-65
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• 1990

열중성자로의 무작위 중성자 특성을 PC로써 측정하는 체계를 개발하고 이를 한국에너지연구소의 TRIGA Mark-II 원자로에 응용하였다. 그 결과 이 체계는 재래의 여러 방법에 비하여 많은 장점을 가지고 있음을 확인하였다. 아직은 한개의 계측기를 사용하였고, 즉발중성자만 고려한 시간 영역에 대하여 autocorrelation과 VTMR 두가지 방법으로 분석하였다. 두 방법의 결과는 서로 잘 일치하였으나 통계적인 신뢰도 면에서는 VTMR이 훨씬 나았고, 특히 임계 근처에서 이것이 두드러졌다. TRIGA Mark-II의 $\beta$/Λ 는 임계에서 -3＄까지는 약 125/초, -4＄이하에서는 약 150/초로 측정되었다.

• Journal of Radiation Protection and Research
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• 제41권4호
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• pp.328-332
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• 2016

Background: Boron Neutron Capture Therapy (BNCT) is a new radiation therapy. In BNCT, there exists some very critical problems that should be solved. One of the severest problems is that the treatment effect cannot be known during BNCT in real time. We are now developing a SPECT (single photon emission computed tomography) system (BNCT-SPECT), with a cadmium telluride (CdTe) semiconductor detector. BNCT-SPECT can obtain the BNCT treatment effect by measuring 478 keV gamma-rays emitted from the excited state of $^7Li$ nucleus created by $^{10}B(n,{\alpha})$ $^7Li$ reaction. In the previous studies, we investigated the feasibility of the BNCT-SPECT system. As a result, the S/N ratio did not meet the criterion of S/N > 1 because deterioration of the S/N ratio occurred caused by the influence of Compton scattering especially due to capture gamma-rays of hydrogen. Materials and Methods: We thus produced an arrayed detector with two CdTe crystals to test cross talk phenomenon and to examine an anti-coincidence detection possibility. For more precise analysis for the anti-coincidence detection, we designed and made a collimator having a similar performance to the real BNCT-SPECT. Results and Discussion: We carried out experiments with the collimator to examine the effect of cross talk of scattering gamma-rays between CdTe elements more practically. As a result of measurement the coincidence events were successfully extracted. Conclusion: We are now planning to carry out evaluation of coincidence rate from the measurement and comparison of it with the numerical calculations.

• Nuclear Engineering and Technology
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• 제36권6호
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• pp.528-539
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• 2004

It is essential in commercial reactors that the safety limits imposed on the fuel pellets and fuel clad barriers, such as the linear power density (LPD) and the departure from nucleate boiling ratio (DNBR), are not violated during reactor operations. In order to accurately monitor the safety limits of current reactor states, a detailed three-dimensional (3D) core power distribution should be estimated from the in-core detector signals. In this paper, we propose a calculation methodology for detailed 3D core power distribution, using in-core detector signals and core monitoring constants such as the 3D Coupling Coefficients (3DCC), node power fraction, and pin-to-node factors. Also, the calculation method for several core safety parameters is introduced. The core monitoring constants for the real core state are promptly provided by the core design code and on-line MASTER (Multi-purpose Analyzer for Static and Transient Effects of Reactors), coupled with the core monitoring program. through the plant computer, core state variables, which include reactor thermal power, control rod bank position, boron concentration, inlet moderator temperature, and flow rate, are supplied as input data for MASTER. MASTER performs the core calculation based on the neutron balance equation and generates several core monitoring constants corresponding to the real core state in addition to the expected core power distribution. The accuracy of the developed method is verified through a comparison with the current CECOR method. Because in all the verification calculation cases the proposed method shows a more conservative value than the best estimated value and a less conservative one than the current CECOR and COLSS methods, it is also confirmed that this method secures a greater operating margin through the simulation of the YGN-3 Cycle-1 core from the viewpoint of the power peaking factor for the LPD and the pseudo hot pin axial power distribution for the DNBR calculation.

• 대한화학회지
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• 제21권6호
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• pp.427-433
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• 1977

강물 시료속에 함유된 크롬, 철, 란탄, 스칸듐 및 아연의 함량을 방사화 분석법으로 동시정량하는 방법을 확립하였다. 10ml의 강물 시료를 사전 처리없이 석영관 속에 밀봉한 다음 열중성자속이 $1{\times}10^{13}n{\cdot}cm^{-2}{\cdot}sec^{-1}$인 곳에서 1주일간 조사하였다. 약 2일간 냉각시킨 후 시료 속에든 원소들을 0.1M 옥신의 클로로포름용액으로 여러 pH에서 연속적으로 추출하였다. 감마선 분광분석을 위하여 유기층을 800챈널 펄스높이 분석기에 연결된 $″3\;{\times}\;3″$ NaI (T1) 검출기로 계측하였다. 본분석법에 의하여 대부분의 강물 시료에 ppb 농도범위로 함유된 이들 원소들의 정량이 가능하였다. 추적자를 써서 이들 원소의 정량적 분리를 위한 연구를 수행하였다.

• Journal of Radiation Protection and Research
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• 제42권1호
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• pp.16-20
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• 2017

Background: The design of deuteron accelerator neutron source facilities requires reliable yield estimation of gamma-rays as well as neutrons from deuteron-induced reactions. We have so foar measured systematically double-differential thick target neutron yields (DDTTNYs) for carbon, aluminum, titanium, copper, niobium, and SUS304 targets. In the neutron data analysis, the events of gamma-rays taken simultaneously were treated as backgrounds. In the present work, we have re-analyzed the experimental data for a thick carbon target with particular attention to gamma-ray events. Materials and Methods: Double-differential thick target gamma-ray yields from carbon irradiated by 5 and 9 MeV deuterons were measured using an NE213 liquid organic scintillator at the Kyushu University Tandem accelerator Laboratory. The gamma-ray energy spectra were obtained by an unfolding method using FORIST code. The response functions of the NE213 detector were calculated by EGS5 incorporated in PHITS code. Results and Discussion: The measured gamma-ray spectra show some pronounced peaks corresponding to gamma-ray transitions between discrete levels in residual nuclei, and the measured angular distributions are almost isotropic for both the incident energies. Conclusion: PHITS calculations using INCL, GEM, and EBITEM models reproduce the spectral shapes and the angular distributions generally well, although they underestimate the absolute gamma-ray yields by about 20%.

• Nuclear Engineering and Technology
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• 제18권2호
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• pp.92-96
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• 1986

$^{93}Nb(n,n{\alpha})^{89m}Y$, $^{93}Nb(n,{\alpha})^{90m}Y$과 $^{93}Nb(n,2n)^{92m}Nb$의 14.6MeV 중성자 반응단면적을 $^{27}Al(n,p)^{27}Mg$과 $^{27}Al(n,{\alpha})^{24}Na$ 반응 단면적과 비교하여 측정하였다. $T(D,n)^4He$ 반응을 이용하는 소규모 가속기를 중성자 원으로 사용하였으며 시료에서의 중성자 에너지 퍼짐은 0.4MeV 정도였다. 생성된 방사능은 모두 같은 기하학적 조건에서 70cc HPGe 검출기로 측정하였다.

• Journal of Radiation Protection and Research
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• 제35권4호
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• pp.167-171
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• 2010

Fixed radiation portal monitors (RPMs) deployed at border, seaport, airport and key traffic checkpoints have played an important role in preventing the illicit trafficking and transport of nuclear and radioactive materials. However, the RPM is usually large and heavy and can't easily be moved to different locations. These reasons motivate us to develop a mobile radiation detection system. The objective of this paper is to report our experience on developing the mobile radiation detection system for search and detection of nuclear and radioactive materials during road transport. Field tests to characterize the developed detection system were performed at various speeds and distances between the radioactive isotope (RI) transporting car and the measurement car. Results of measurements and detection limits of our system are described in this paper. The mobile radiation detection system developed should contribute to defending public's health and safety and the environment against nuclear and radiological terrorism by detecting nuclear or radioactive material hidden illegally in a vehicle.

• Journal of Radiation Protection and Research
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• 제46권3호
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• pp.112-119
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• 2021

Background: This work aims to develop a new imaging system based on a pulse shape discrimination-capable Cs₂LiYCl₆:Ce (CLYC) scintillation detector combined with the rotational modulation collimator (RMC) technique for dual-particle imaging. Materials and Methods: In this study, a CLYC-based RMC system was designed based on Monte Carlo simulations, and a prototype was fabricated. Therein, a rotation control system was developed to rotate the RMC unit precisely, and a graphical user interface-based software was also developed to operate the data acquisition with RMC rotation. The RMC system was developed to allow combining various types of collimator masks and detectors interchangeably, making the imaging system more versatile for various applications and conditions. Results and Discussion: Operational performance of the fabricated system was studied by checking the accuracy and precision of the collimator rotation and obtaining modulation patterns from a gamma-ray source repeatedly. Conclusion: The prototype RMC system showed reliability in its mechanical properties and reproducibility in the acquisition of modulation patterns, and it will be further investigated for its dual-particle imaging capability with various complex radioactive source conditions.