• Journal of Nutrition and Health
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• 제31권2호
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• pp.213-219
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• 1998

This study was conducted to compare and evaluate the iodide specific ion electrode method (ISE) and neutron activation analysis method (NAA) for determining iodine in human milk and cow milk. The neutron irradiation and counting operations were carried out at the TRIGA Mark-III reactor facility of the Korea Atomic Energy Research Institute. The mean concentrations of iodine in human milk samples by the ISE and the NAA were 1450$\mu\textrm{g}$/L and 1350$\mu\textrm{g}$/L, respectively. The levels were not significantly different. In cow milk samples , the mean concentrations of iodine by the ISE and the NAA were 250$\mu\textrm{g}$.L and 200$\mu\textrm{g}$/L, respectively. here, the ISE reading was significantly higher than the NAA. reading. The correlations of the two methods were 0.92(p<0.001) for human milk samples and 0.65 for cow milk samples . The coefficient of variation was 8.3% in the ISE and 4.9% in the NAA. Therefore, the iodide specific ion electrode method is sample and fast method, but probably not in processed milk since free sulfhydryl groups in milk are also detected by the iodide electrode. However, these also indicate that the ISE method may be applicable to human milk and pasteurized milk if the conventional pasteurization time-temperature relationship of standards is not exceeded. On the other hand, the NAA method , which is independent of chemical forms and matrix, can be used for determining iodine in all kinds of milk and foods.

• 분석과학
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• 제6권5호
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• pp.501-508
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• 1993

$^{241}Am-Be$(${\alpha}$, n) 중성자 선원의 중성자/감마선(n/${\gamma}$) 복합 방사선장에서 $^6Li$(n, ${\alpha}$)T 핵반응을 이용하고 두 섬광체, BC 501($C_8H_{10}$)과 Cerium의 섬광 감쇠 시간차와 동일 섬광체 내에서의 n/${\gamma}$에 대한 서로 다른 섬광감쇠 시간차를 병용하여 PSD(Pulse Shape Disciminator) 및 CFD(Constant Fraction Discriminator) 방법으로 n와 ${\gamma}$성분을 분리 측정하였으며 $^6Li$ 속중성자 분광계의 figure of merit는 1.36으로 평가되었다.

• Nuclear Engineering and Technology
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• 제38권6호
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• pp.585-590
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• 2006

This paper describes the results of an irradiation test and the specifications of the pneumatic transfer system (PTS) in the NAA #3 irradiation hole at the HANARO research reactor, which was reinstalled after some modifications of the operation mode at the end of 2004. The outer and inner diameters of the PE transfer tube are 34.1 and 27.5 mm, respectively. PE rabbit was used for sample irradiation. The $N_2$ gas pressure of the PTS lines was adjusted to 0.75 bar. The average sending time to the reactor was $8.5{\pm}0.3$ s and the average receiving time back to the receiver was $3.2{\pm}0.2$ s. The internal and external temperature of the irradiation tube was measured in a range of 50 to $80^{\circ}C$ for a 40 s to 80 s irradiation time, respectively. The optimum irradiation time was estimated to be less than 80 s. The thermal, epithermal and fast neutron flux at 30 MW thermal power were $1.42{\pm}0.01{\times}10^{14},\;1.51{\pm}0.04{\times}10^{13}$ and $9.48{\pm}0.69{\times}10^{11} n{\cdot}cm^{-2}{\codt}s^{1-}$, respectively. The cadmium ratio was approximately 9.40. The data obtained will be applied to supplement user information and for reactor management.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.154-154
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• 2019

Characterization of reliable field-scale root-zone soil moisture (RZSM) variability contribute to effective hydro-meterological monitoring. Although a promising cosmic-ray neutron probe (CRNP) holds the pontential for field-scale RZSM measurement, it is often restricted at deeper depths due to the non-unique sensitivity of CRNP-measured fast neutron signal to other hydrogen pools. In this study, a merging framework relied on coupling cosmic-ray soil moisture with a representative additional RZSM, was introduced to scale shallower CRNP effective depth to represent root-zone layer. We tested our proposed framework over a densely vegetated region in South Korea covering a network of one CRNP and nine in-situ point measurements. In particular, cosmic-ray soil moisture and ancillary RZSM retrieved from the most time stable location were considered as input datasets; whereas the remaining point locations were used to generate a reference RZSM product. The errors between these two input datasets and the reference were forecasted by a linear autoregressive model. A linear combination of forecasts was then employed to compute a suitable weight for merging two input products from the predicted errors. The performance of merging framework was evaluated against reference RZSM in comparison to the two original products and a commonly used exponential filter technique. The results of this study showed that merging framework outperformed other products, demonstrating its robustness in improving field-scale RZSM. Moreover, a strong relationship between the quality of input data and the performance merging framework in light of CRNP effective depth variation has been also underlined via the merging framework.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2315-2324
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• 2023

Space nuclear reactors are becoming popular in deep space exploration owing to their advantages of high-power density and stability. Following the fourth-generation nuclear reactor technology, a conceptual design of the dual drum-controlled space molten salt reactor (D²-SMSR) is proposed. The reactor concept uses molten salt as fuel and heat pipes for cooling. A new reactivity control strategy that combines control drums and safety drums was adopted. Critical physical characteristics such as neutron energy spectrum, neutron flux distribution, power distribution and burnup depth were calculated. Flow and heat transfer characteristics such as natural convection, velocity and temperature distribution of the D²-SMSR under low gravity conditions were analyzed. The reactivity control effect of the dual-drums strategy was evaluated. Results showed that the D²-SMSR with a fast spectrum could operate for 10 years at the full power of 40 kWth. The D²-SMSR has a high heat transfer coefficient between molten salt and heat pipe, which means that the core has a good heat-exchange performance. The new reactivity control strategy can achieve shutdown with one safety drum or three control drums, ensuring high-security standards. The present study can provide a theoretical reference for the design of space nuclear reactors.

• Journal of Radiation Protection and Research
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• 제2권1호
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• pp.17-23
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• 1977

여러가지 핵분열중성자(核分裂中性子) 스펙트럼에 $^{32}S(n,\;p),\;^{27}Al(n,\;{\alpha})$ 및 $^{115}In(n\;n')$ 여기함수(勵起函數)를 증율(增率)시켜 평균핵반응단면적(平均核反應斷面積)을 전자계산기(電子計算機)로 계산(計算)하였다. 그 결과(結果) 발단(發端)에너지가 높을수록 중성자(中性子)스펙트럼 변화(變化)에 따라 평균(平均) 단면적(斷面積)은 민감(敏感)하게 변화(變化)한다는 것이 판명(判明)되었다. 발단(發端)에너지가 비교적(比較的) 낮은 인디움의 경우(境遇), 핵분열특성(核分裂特性)에 따라 그의 평균(平均) 단면적(斷面積)은 크게 변화(變化)되지 않았는데 중성자(中性子) 산란작용(散亂作用)에 의(依)한 영향(影響)이 배제(排除)될 수만 있다면 인디움은 핵임계사고시(核臨界事故時)에 방출(放出)되는 중성자(中性子)의 적산계(積算計)로서 효과적(效果的)으로 사용(使用)될 수 있을 것 같았다. 더욱이 중성자선량환산인자(中性子線量換算因子)가 핵분열(核分裂) 중성자(中性子)스펙트럼에 거의 무관(無關)하다는 사실(事實)은 인디움을 핵임계사고시(核臨界事故時)의 중성자선량적산계(中性子線量積算計)로 사용할 수 있음을 뒷받침하는 것 같았다.

• 비파괴검사학회지
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• 제20권3호
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• pp.183-190
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• 2000

본 연구에서는 고속 중성자가 조사된 원자로 용기 재료의 자기적 성질 변화를 $M{\ddot{o}}ssbauer$ 분광법을 이용하여 측정하였으며, X-선 회절실험을 이용하여 중성자 조사재료의 결정성 변화를 평가하였다. 시편은 크기가 $23mm{\times}18mm{\times}70{\mu}m$로 제작되었으며, 343K에서 $10^{12}n/cm^2{\sim}10^{18}n/cm^2$의 범위에서 중성자 조사를 하였다. X-선 회절실험 결과로부터, $10^{16}n/cm^2$의 중성자가 조사된 시료에서부터 결정성이 변화가 시작되고, $10^{17}n/cm^2$ 이상의 중성자가 조사된 시료에서 결정성이 심각하게 손상되는 것이 관찰되었다. 또한 $M{\ddot{o}}ssbauer$ 분광실험으로부터 중성자 조사량이 $10^{16}n/cm^2$ 이하인 시료에서는 자기적성질의 변화가 관찰되지 않았으나, $10^{17}n/cm^2$ 이상의 중성자가 조사된 시료에서 자기완화 현상이 일어나는 것이 관찰되었다. 따라서 두 실험 모두 비파괴적 실험방법에 따른 중성자 조사취화 평가로 활용이 가능한 것으로 평가되었다.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1213-1224
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• 2024

The liquid lead-bismuth cooled fast reactor has been in a single-phase, low-pressure, and high-temperature state for a long time during operation. Considering the requirement of calculation efficiency for long-term transient accident calculation, based on a homogeneous hydrodynamic model, one-dimensional heat conduction model, coolant flow and heat transfer model, neutron kinetics model, coolant and material properties model, this study used the fully implicit difference scheme algorithm of the convection-diffusion term to solve the basic conservation equation, to develop the transient analysis program NUSOL-LMR 2.0 for the lead-bismuth fast reactor system. The steady-state and typical design basis accidents (including reactivity introduction, loss of flow caused by main pump idling, excessive cooling, and plant power outage accidents) for the ABR have been analyzed. The results are compared with the international system analysis software ATHENA. The results indicate that the developed program can stably, accurately, and efficiently predict the transient accident response and safety characteristics of the lead-bismuth fast reactor system.

• 한국수의병리학회:학술대회논문집
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• 한국수의병리학회 2004년도 추계 학술대회 초록집
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• pp.16-16
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• 2004

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.15-15
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• 2011

As you know, boron compounds, borax ($Na_2B_4O_5(OH)_4{\cdot}8H_2O$) etc. were known thousands of years ago. As for natural boron, it has two naturally occurring and stable isotopes, boron 11 ($^{11}B$) and boron 10 ($^{10}B$). The neutron absorption $^{10}B$ is included about 19~20% with 80~81% $^{11}B$. Boron is similar to carbon in its capability to form stable covalently bonded molecular networks. The mass difference results in a wide range of ${\beta}$ values between the $^{11}B$ and $^{10}B$. The $^{10}B$ isotope, stable with 5 neutrons is excellent at capturing thermal neutrons. For example, it is possible to decrease a thermal neutron required for the nuclear reaction of uranium 235 ($^{235}U$). If $^{10}B$ absorbs a neutron ($^1n$), it will change to $^7Li+^1{\alpha}$ (${\alpha}$ ray, like $^4He$) with prompt ${\gamma}$ ray from $^{11}B$ $^{11}B$ (equation 1). $$^{10}B+^1n\;{\rightarrow}\;^{11}B\;{\rightarrow}\; prompt \;{\gamma}\;ray (478 keV), \;^7Li+4{\alpha}\;(4He)\;\;\;\;{\cdots}\; (1)$$ If about 1% boron is added to stainless steel, it is known that a neutron shielding effect will be 3 times the boron free steel. Enriched boron or $^{10}B$ is used in both radiation shielding and in boron neutron capture therapy. Then, $^{10}B$ is used for reactivity control and in emergency shutdown systems in nuclear reactors. Furthermore, boron carbide, $B_4C$, is used as the charge of a nuclear fission reaction control rod material and neutron cover material for nuclear reactors. The $B_4C$ powder of natural B composition is used as a charge of a control material of a boiling water reactor (BWR) which occupies commercial power reactors in nuclear power generation. The $B_4C$ sintered body which adjusted $^{10}B$ concentration is used as a charge of a control material of the fast breeder reactor (FBR) currently developed aiming at establishment of a nuclear fuel cycle. In this study for new boron compound, silicon boride ceramics for capturing thermal neutrons, preparation and characterization of both silicon tetraboride ($SiB_4$) and silicon hexaboride ($SiB_6$) and ceramics produced by sintering were investigated in order to determine the suitability of this material for nuclear power generation. The relative density increased with increasing sintering temperature. With a sintering temperature of 1,923 K, a sintered body having a relative density of more than 99% was obtained. The Vickers hardness increased with increasing sintering temperature. The best result was a Vickers hardness of 28 GPa for the $SiB_6$ sintered at 1,923K for 1 h. The high temperature Vickers hardness of the $SiB_6$ sintered body changed from 28 to 12 GPa in the temperature range of room temperature to 1,273 K. The thermal conductivity of the SiB6 sintered body changed from 9.1 to 2.4 W/mK in the range of room temperature to 1,273 K.