• Nuclear Engineering and Technology
• /
• 제48권2호
• /
• pp.330-338
• /
• 2016

The U-Zr or U-TRU-Zr cylindrical metallic fuel slug used in fast reactors is known to swell significantly and to grow during irradiation. In neutronics simulations of metallic-fueled fast reactors, it is assumed that the slug has swollen and contacted cladding, and the bonding sodium has been removed from the fuel region. In this research, a realistic burnup-dependent fuel-swelling simulation was performed using Monte Carlo code McCARD for a single-batch compact sodium-cooled breed-and-burn reactor by considering the fuel-swelling behavior reported from the irradiation test results in EBR-II. The impacts of the realistic burnup-dependent fuel swelling are identified in terms of the reactor neutronics performance, such as core lifetime, conversion ratio, axial power distribution, and local burnup distributions. It was found that axial fuel growth significantly deteriorated the neutron economy of a breed-and-burn reactor and consequently impaired its neutronics performance. The bonding sodium also impaired neutron economy, because it stayed longer in the blanket region until the fuel slug reached 2% burnup.

• Nuclear Engineering and Technology
• /
• 제53권11호
• /
• pp.3723-3740
• /
• 2021

The harsh conditions in the reactor affect the thermal and mechanical performance of the fuel plate heavily. Some in-pile behaviors, like fission-induced swelling, can cause a large deformation of fuel plate at very high burnup, which may even disturb the flow of coolant. In this research, the emphasis is put on the thermal expansion, fission-induced swelling, interaction layer (IL) growth, creep of the fuel meat, and plasticity of the cladding for the U₃Si₂/Al dispersion fuel plate. A detailed model of the fuel meat swelling is developed. Taking these in-pile behaviors into consideration, the three-dimensional large deformation incremental constitutive relations and stress update algorithms have been developed to study its thermal-mechanical performance under normal conditions using Abaqus. Results have shown that IL can effectively decrease the thermal conductivity of fuel meat. The high Mises stress region mainly locates at the interface between fuel meat and cladding, especially around the side edge of the interface. With irradiation time increasing, the stress in the fuel plate gets larger resulting from the growth of fuel meat swelling but then decreases under the effect of creep deformation. For the cladding, plasticity deformation does not occur within the irradiation time.

• Macromolecular Research
• /
• 제9권5호
• /
• pp.253-258
• /
• 2001

Crosslinked poly(ethylene glycol)s (PEGs) were prepared by ultraviolet irradiation of low molar mass, liquid PEGs in the presence of benzophenone (BP) as a photoinitiator. The networks obtained have been characterized by DSC, IR, and contact angle measurements, and their water absorption and equilibrium swelling have been examined. The percent of gel formed and degree of swelling of the networks in water were dependent on the amount of BP in the reaction mixture, irradiation time and molar mass of PEG. Gel fraction yield exceeded 84%, and equilibrium swelling in water varied from 49 to 244%.

• 대한의용생체공학회:의공학회지
• /
• 제39권4호
• /
• pp.161-167
• /
• 2018

Polyvinyl alcohol/sodium carboxymethyl cellulose (PVA/NaCMC) hydrogels were prepared by physical crosslinking (cyclic freezing/thawing) and gamma (${\gamma}$)-ray irradiation to evaluate the effect of NaCMC concentration (2~8 wt%) on the mechanical properties and the biocompatibility of the PVA/NaCMC hydrogels. The swelling rate of PVA/NaCMC hydrogels regardless of irradiation rose with increasing NaCMC content from 2 wt% to 8 wt%, while the gelation rate was the reverse. As the NaCMC content increased from 2 wt% to 6 wt%, the compressive strength of the hydrogels increased dramatically from $8.5{\pm}2.0kPa$ to $52.7{\pm}2.5kPa$ before irradiation and from $13.5{\pm}2.9kPa$ to $65.5{\pm}8.7kPa$ after irradiation. When 8 wt% NaCMC was added afterwards, the compressive strength decreased however. The irradiated PVA/NaCMC hydrogels containing 6 wt% NaCMC exhibited the tailored properties of the swelling rate of $118{\pm}3.7%$, the gelation rate of $71.4{\pm}1.3%$, the strength of $65.5{\pm}8.7kPa$, respectively, and no cytotoxicity was observed.

• Macromolecular Research
• /
• 제16권2호
• /
• pp.139-148
• /
• 2008

Biodegradable and elastic poly(L-lactide-co-$\varepsilon$-caprolactone) (PLCL) was electrospun to prepare nanofibers, and N-isopropylacrylamide (NIPAAm) was then grafted onto their surfaces under aqueous conditions using $^{60}Co-{\gamma}$ irradiation. The graft yield increased with increasing irradiation dose from 5 to 10 kGy and the nanofibers showed a greater graft yield compared with the firms. SEM confirmed that the PLCL nanofibers maintained an interconnected pore structure after grafting with NIPAAm. However, overdoses of irradiation led to the excessive formation of homopolymer gels on the surface of thc PLCL nanofibers. The equilibrium swelling and deswelling ratio of the PNIPAAm-g-PLCL nanofibers (prepared with 10 kGy) was the highest among the samples, which was consistent with the graft yield results. The phase-separation characteristics of PNIPAAm in aqueous conditions conferred a unique temperature-responsive swelling behavior of PNIPAAm-g-PLCL nanofibers, showing the ability to absorb a large amount of water at < $32^{\circ}C$, and abrupt collapse when the temperature was increased to $40^{\circ}C$. In accordance with the temperature-dependent changes in swelling behavior, the release rate of indomethacin and FITC-BSA loaded in PNIPAAm-g-PLCL nanofibers by a diffusion-mediated process was regulated by the change in temperature. Both model drugs demonstrated greater release rate at $40^{\circ}C$ relative to that at $25^{\circ}C$. This approach of the temperature-controlled release of drugs from PNIPAAm-g-PLCL nanofibers using gamma-ray irradiation may be used to design drugs and protein delivery carriers in various biomedical applications.

• Nuclear Engineering and Technology
• /
• 제41권2호
• /
• pp.155-162
• /
• 2009

Since the 90's, EDF and AREVA-NP have irradiated, up to very high burnups, lead assemblies housing $M5^{(R)}$ cladded fuels. Post-irradiation examination of high burnup $UO_2$ pellets show an increase in the fission-gas release rate, an increase in fuel swelling, and formation of fission-gas bubbles throughout the pellets. Xenon abundances were quantified, and phenomena leading to this bubble formation were identified. All examinations provided valuable data on the complex state of the fuel during irradiation. They show the good behavior of these fuels, exhibiting various microstructures at very high burnups, none of which is likely to lead to problems during irradiation.

• 방사선산업학회지
• /
• 제2권1호
• /
• pp.15-19
• /
• 2008

In order to develop a water-solubility and biocompatibility, chemically modified chitosan, N,O-carboxymethylchitosan (NOCC), was synthesized and the NOCC hydrogels were prepared by using ${\gamma}-ray$ irradiation instead of chemical reagents. The FT-IR spectroscopy, swelling behavior, gel content and mechanical property such as gel strength of the hydrogel were measured. When the NOCC solution concentration was 15 wt% and the dose of irradiation was less than 50 kGy, the NOCC hydrogels had an excellent hydrophilicity and exhibited a good swelling behavior and mechanical properties.

• 한국압력기기공학회 논문집
• /
• 제20권1호
• /
• pp.39-48
• /
• 2024

Research reactors are operated under ambient temperature and atmospheric pressure, which is much less severe conditions compared to those in typical nuclear power plants. Due to the high temperature, heat resistant materials such as austenite stainless steel should be used for the reactors in typical nuclear power plants. Whereas, as the effect of temperature is low for research reactors, materials with high resistance to neutron irradiation, such as zircaloy and beryllium, are used. Therefore, these conditions should be considered when performing integrity assessment for research reactors. In this study, a computational technique through finite element (FE) analysis was developed considering the operating conditions and materials of research reactor when conducting integrity assessment. Neutron irradiation analysis techniques using thermal expansion analysis were proposed to consider neutron irradiation growth and swelling in zirconium alloys and beryllium. A user subroutine program that can calculate the strain rate induced by neutron irradiation creep was developed for use in the commercial analysis program Abaqus. To validate the proposed technique and the user subroutine, FE analysis results were compared with hand-calculation results, and showed good agreement. Consequently, developed technique and user subroutine are suitable for evaluating structural integrity of research reactors.

• Nuclear Engineering and Technology
• /
• 제24권1호
• /
• pp.40-51
• /
• 1992

연구용 원자로의 분산형 핵연료에 대한 노내 조사 거동의 주요 특성중의 하나는 핵연료심 팽윤에 기인된 핵연료봉 직경 증가이다. 본 논문에서는 분산형 우라늄실리사이드 핵연료에 대한 노내 조사거 동과 실험 증거들을 분석함으로써 그 핵연료의 팽윤에 대한 물리적 해석 모형인, DFSWELL 전산 모형을 개발하였다. 문헌에 보고된 실험 증거들로부터 노내에서 U$_3$Si-Al 핵연료심의 부피변화는 온도와 핵분열율에 따라 크게 영향을 받는 것으로 나타났다. 분산형 우라늄 실리사이드 핵연료에 대한 정량적 팽윤량은 주어진 온도, 핵분열율, 핵분열고체생성물 측적 및 핵분열기체 기포거동을 고려함으로써 평가될 수 있다. 연구로의 분산형 우라늄실리사이드 핵연료의 팽윤 현상은 다음과 같은 세 가지 현상으로 귀결된다. i ) 핵분열기체생성물 기포 생성/축적에 치한 부피변화 ii ) 고체 핵분열생성물의 축적 및 상 변화에 의한 부피변화 iii ) 핵연료 입자와 기지 사이의 공유층에 대한 부피변화 상기 세 가지의 물리 적 현상을 고려하는 본 DFSWELL 전산 모형의 출력이력 조건에 따른 절대 예측치들은 실행 결과와 비교할 때 분산형 우라윰실리 사이드 핵연료의 조사추 팽윤 실측치와 잘 일치한다.

• Journal of Plant Biotechnology
• /
• 제41권1호
• /
• pp.44-49
• /
• 2014

In this study, we investigated the effects of sodium hypochlorite (NaOCl) and red or blue light-emitting diode (LED) light on embryo swelling and germination of Oreorchis patens (Lindl.) Lindl. A method for determining the swelling and protocorm formation in O. patens seeds through in vitro examination of immature seeds was established. NaOCl treatment of immature seeds was found to significantly enhance the extent of embryo swelling and protocorm formation in immature zygote embryos compared to those in the untreated controls. Additionally, the effects of white fluorescent light, and red and blue LED lights on embryo swelling and protocorm formation in in vitro cultured seeds were examined and compared to the conditions with or without NaOCl treatment. The most suitable light for embryo swelling and protocorm formation was the red LED light.