• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1277-1283
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• 2024

This study presents a radiation-induced thermal conductivity degradation (TCD) model of zirconium as compared to the conventional UO2 TCD model. We derived the governing factors of the radiation-induced TCD model, such as maximum TCD value and temperature range of TCD. The maximum TCD value was derived by two methods, in which 1) experimental result of 32 % TCD was directly utilized as the maximum TCD value and 2) a theoretical approach based on dislocation was applied to derive the maximum TCD value. Further, the temperature range of TCD was determined to be 437-837 K by 1) experimental results of post-annealing of irradiation hardening as compared to 2) the rate theory and thermal equilibrium. Consequently, the radiation-induced TCD model of zirconium was derived to be $f_r=1-{\frac{0.32}{1+{\exp}\,\{(T-637)/45\}}}$. Because the thermal conductivity of zirconium is one of the factors determining the storage and transport system, this newly proposed model could improve the safety analysis of spent fuel storage systems.

• Macromolecular Research
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• 제11권3호
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• pp.146-151
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• 2003

The dependence of electrical conductivity on concentrations of diallyldimethylammonium chloride (DADMAC) monomer, linear poly(DADMAC) and their mixture monomer/poly(DADMAC) in dilute aqueous solution exhibits a linear relationship. It was possible to calculate conversion of DADMAC polymerization by measuring its electric conductivity. Although the electrical conductivity of the poly(DADMAC) solution decreased with increasing its molecular weight, in the process of UV or ionizing radiation polymerization the molecular weight of the polymers could be kept constant in the case of fixed temperature, UV-luminous intensity or dose rate. Based on the method mentioned above, the kinetics of UV induced polymerization of DADMAC in aqueous solution was studied; the overall activation energy of polymerization of DADMAC in the water phase was calculated to be 18.8 kJ mol$^{-1}$ . ${\gamma}$-Radiation-induced polymerization of DADMAC in aqueous solution as a function of absorbed dose was studied as well. The conversion of DADMAC increased quickly with dose before 30 kGy and then increased slowly. The experimental data of both UV- and ${\gamma}$-induced polymerization were verified to be reliable by inverted ultracentrifugation method.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.402-409
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• 2024

High energy neutron irradiations impact on structural and electrical properties of alumina are studied with particular emphasis on real time in-situ radiation induced conductivity measurement in low flux region. Polycrystalline Al₂O₃ samples are subjected to high energy neutrons produced from D-T neutron generator and Am-Be neutron source. 14 MeV neutrons from D-T generator are chosen to study the role of fast neutron irradiation in the structural modification of samples. Real time in-situ electrical measurement is performed to investigate the change in insulation resistance of Al₂O₃ due to radiation induced conductivity at low flux regime. During neutron irradiation, a significant transient decrease in insulation resistance is observed which recovers relative higher value just after neutron exposure is switched off. XRD results of 14 MeV neutron irradiated samples suggest annealing effect. Impact of relatively low energy neutrons on the structural properties is also studied using Am-Be neutrons. In this case, clustering is observed on the sample surface after prolonged neutron exposure. The structural characterizations of pristine and irradiated Al₂O₃ samples are performed using XRD, SEM, and EDX. The results from these characterizations are analysed and interpreted in the manuscript.

• Korean Membrane Journal
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• 제9권1호
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• pp.52-56
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• 2007

A proton exchange membrane was prepared by ${\gamma}-irradiation-induced$ grafting of styrene into poly(tetrafluoro-ethylene-co-perfluoropropyl vinyl ether) (PFA) and subsequent sulfonation reaction. The degree of grafting (DOG) increased with an increase in the absorbed dose. The prepared membranes showed high ion exchange capacity reaching 3.0 meq/g, which exceeded the performance of commercially available perfluorosulfonic acid membranes such as Nafion. The proton conductivity of PFA-g-PSSA membrane increased with the DOG and reached 0.17 S/cm for the highest sample at room temperature. The DMFC performance of the prepared membranes with 50% DOG was comparable to that of Nafion membrane.

• Carbon letters
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• 제16권1호
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• pp.41-44
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• 2015

We report the preparation of sulfonated reduced graphene oxide (SRGO) by the sulfonation of graphene oxide followed by radiation-induced chemical reduction. Graphene oxide prepared by the well-known modified Hummer's method was sulfonated with the aryl diazonium salt of sulfanilic acid. Sulfonated graphene oxide (SGO) dispersed in ethanol was subsequently reduced by ${\gamma}$-ray irradiation at various absorbed doses to produce SRGO. The results of optical, chemical, and thermal analyses revealed that SRGO was successfully prepared by ${\gamma}$-ray irradiation-induced chemical reduction of the SGO suspension. Moreover, the electrical conductivity of SRGO was increased up to 2.94 S/cm with an increase of the absorbed dose.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2359-2366
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• 2022

Selecting graphite grades with superior irradiation characteristics is important task for designers of graphite moderation reactors. To provide reference information and data for graphite selection, the effects of irradiation on three fine-grained, iso-molded nuclear grade graphites, ETU-10, IG-110, and NBG-25, were compared based on irradiation-induced changes in volume, thermal conductivity, dynamic Young's modulus, and coefficient of thermal expansion. Data employed in this study were obtained from reported irradiation test results in the high flux isotope reactor (HFIR)(ORNL) (ETU-10, IG-110) and high flux reactor (HFR)(NRL) (IG-110, NBG-25). Comparisons were made based on the irradiation dose and irradiation temperature. Overall, the three grades showed similar irradiation-induced property change behaviors, which followed the historic data. More or less grade-sensitive behaviors were observed for the changes in volume and thermal conductivity, and, in contrast, grade-insensitive behaviors were observed for dynamic Young's modulus and coefficient of thermal expansion changes. The ETU-10 of the smallest grain size appeared to show a relatively smaller VC to IG-110 and NBG-25. Drastic decrease in the difference in thermal conductivity was observed for ETU-10 and IG-110 after irradiation. The similar irradiation-induced properties changing behaviors observed in this study especially in the DYM and CTE may be attributed to the assumed similar microstructures that evolved from the similar size coke particles and the same forming method.

• 폴리머
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• 제34권2호
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• pp.126-132
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• 2010

메탄올 용매에서 고분자 촉진 단량체와 소디윰 스티렌 슐포네이트를 방사선 그래프트 방법으로 양이온 교환 PVdF 맴브레인을 제조하였다. 고분자 촉진 단량체로서 스티렌, 아크릴산, 비닐 피롤리돈을 사용하였다. 또한, 음이온 교환 PVdF 맴브레인도 방사선 그래프트 중합법에 의해 제조하였다. 양이온 및 음이온 교환 PVdF 맴브레인은 SEM, XPS 그리고 열분석기기를 통해 특성평가를 하였고 성공적으로 합성됨을 확인할 수 있었다. 그래프트 수율, 이온교환기의 양 및 침투율은 각각 30.0~32.3%, 2.81~3.01 mmol/g 그리고 66.6~147%로 평가되었으며, 20 $^{\circ}C$에서 이온 전도도를 측정한 결과 0.020~0.053 S/cm 이었다. 최종적으로, 제조된 양이온 및 음이온교환 PVdF 맴브레인은 전지격막으로서 충분히 사용될 수 있음을 확인할 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.130-133
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• 2006

In order to study the relationship between the discharge characteristics of an ac PDP and the surface conductivity of MgO thin film, the surface current across a ring shaped MgO film was measured by exposure to monochromatic vacuum ultraviolet from the synchrotron radiation source whose wavelength ranges from 60nm to 240nm $(5.5eV{\sim}25eV)$. The experimental results show that the surface current begins to increase rapidly at the photon energy of about 9 eV which might correspond to the valence band edge of MgO. The difference in the surface current level correlate well with the differences in the preparation method of MgO films and their respective discharge characteristics such as the firing, minimum sustain voltages, address voltage margin and address discharge delay time.

• 한국통신학회논문지
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• 제23권4호
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• pp.836-845
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• 1998

본 논문에서는 전류 라인 아래, 위에 놓은 유한 도전성 다층 영상 평면이 전자파 복사에 미치는 영향을 분석하였으며, 전류 라인과 영상 평면의 폭, 전류 라인과 평면의 거리 등의 함수로 영상 평면의 EMI 차폐성능을 계산하였다. 영상 평면에 유도된 전류분포는 모멘트 기법을 이용하여 전계 적분방정식을 풀어서 계산하였으며, 전류분포를 작은 매트릭스 크기로 효율적으로 구하기 위해 전류분포의 변화를 고려하여 적분구간을 분할하는 새로운 방법을 제안하고 그 결과를 다른 방법과 비교하였다.

• 한국의학물리학회지:의학물리
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• 제9권1호
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• pp.11-21
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• 1998

일렉트릿 (electret) 의 특성을 갖고 있는 Teflon-FEP 와 PET 필름의 유전체 양변에 크롬을 증착시켜 전극을 만들고 코발트-60 감마선을 찍어 이 두 유전체의 물리적 특성변화를 조사하였다. 선량률 25.0 cGy/min에서 방사선 조사하기 시작하여 2초이내에서 전류가 급격히 증가해 최대값에 이른후, 60초 이후에선 거의 안정값에 이르는 특성을 보였다. 방사선 조사동안 Teflon의 경우 유전 상수는 2.15에서 18.0으로, 전기전도도는 1$\times$$10^{-17}$ 에서 1.57$\times$$10^{-13}$ $\Omega$$^{-l}$ $cm^{-1}$ /으로 증가했고, PET는 유전상수는 3에서 18.3으로, 전기전도도는 $10^{-17}$ 에서 1.65$\times$$10^{-13}$ $\Omega$$^{-1}$$cm^{-1}$ /값으로 변하였다. 분당선량률을 변화시켰을때 (4.0 cGy/min, 8.5 cGy/min, 15.6 cGy/min, 19.3 cGy/min) 정상상태 방사선 유도전류(Ic), 유전율($\varepsilon$), 전기전도도 ($\sigma$) 가 선량률에 따라 증가함을 보였다. 정상상태방사선유도전류(Ic)값은 12시간내에선 1%내의 재현성을 보였고, 1주일간에선 3%내에서 일치하였다. 전하 및 전류값이 측정간격 (방사선 조사후 다음 조사때까지의 시간)에 의존성을 보였으며, 측정간격이 작을수록 초기측정값과 후측정값의 차가 크며, 최소 20분이상 간격을 둘 때 후측정값이 초기측정값과 같아졌다. 25.0 cGy/min. 선량률에서 유전체가 20분동안 전하를 유지하는 일펙트릿 성질을 갖고 있음을 보였다. 위 실험결과들은 2차전자에 의한 자유전자와 정공의 발생 및 이로 인한 내부편극과 전도도의 변화, 재결합등으로 인한 전자평형상태에 의한 것으로 볼 수 있다. 방사선조사직후 시료에 열을 가한 후 다시 조사하면 측정값이 상승하는 현상을 보였다. 이는 열을 가함으로 내부편극이 감소되었고 이로인해 다음 방사선 조사시 전하운반자(charge carriers)의 숫자를 높이는데 기여했음을 알 수 있다. 인가전압 및 흡수선량에 따른 선형성 및 재현성과 다른 전리함에 비해 적은 부피로 큰 전하량을 측정하는 것은 미세전류검출기로서의 사용가능성과 검출기의 부피를 크게 줄일수 있는 가능성을 보여준다.