9：00
10：30

鮱名 風太郎

風間 裕行

TRAN Tri Vien

Muhammad Fajar

The lifetime of B₄C pellets has been limited due to swelling effect and thermal stress leading to cracking and fragmentation of neutron-absorbers. High-performance B₄C pellets with excellent mechanical and thermal properties have been considerably required to extend their lifetime. Generally, the properties of ceramics depend on the crystal orientation. Therefore, it is expected that their properties can be enhanced by achieving highly crystal orientation. In this study, highly oriented B₄C ceramics with/without alumina (Al₂O₃) as a sintering additive were prepared under a rotating strong magnetic field followed by spark plasma sintering, and their mechanical and thermal properties were evaluated. In addition, the effect of crystal orientation on the properties of B₄C ceramics was discussed.

Wongsaroj
Wongsakorn

The Boiling Water Reactor (BWR) is a nuclear power plant having many operating units currently. The safety concept is the main issue for the reactor operation. The bubble and liquid phase's velocity distribution in the bubbly flow on sub-cooled boiling conditions is an essential parameter. It relates directly to heat transfer enhancement and downstream boiling distribution, which strongly affects the optimum design and safety margin. Therefore, the experimental investigation of this parameter is a necessity. Ultrasonic Velocity Profiler (UVP) has been developed for velocity distribution measurement on bubbly flow in air-water and the sub-cooled boiling condition. Firstly, the phase separation algorithm was developed. The velocity profile of the bubble and liquid in air-water bubbly flow was derived separately. The applicability and measurement accuracy was evaluated.  Secondly, the UVP with phase separation algorithm was modified by advanced signal processing to extends the velocity range due to the aliasing problem at beyond Nyquist velocity. The velocity range limit is increased to cover the actual value in the real reactor. The success rate of de-aliasing in both phase velocities was investigated. Thirdly, the developed UVP was conducted to obtain the bubbly flow velocity in the sub-cooled boiling condition. The classification of both phase's velocity in elevated temperature was analyzed. The velocity distribution measurement in sub-cooled boiling bubbly flow was test and examined experimentally. Furthermore, the UVP for the two-dimensional velocity measurement in the bubbly flow was developed. The multiple transducers are combined with the phase separation algorithm. The measurement ability was demonstrated and had a comparison with other techniques. These allow obtaining velocity data of experimental investigation for reactor design.

ASA Anie
Day De Castro

X-ray cross-complementing 4 (XRCC4) is one of the most essential proteins for DNA double-strand break (DSB) repair through non-homologous end joining (NHEJ) pathway. In NHEJ, XRCC4 is associated with and required for the function of DNA ligase IV, which joins two DNA ends. XRCC4 has additional roles coordinating DNA end processing prior to the ligation of DNA ends and also forming a filamentous structure with XRCC4-like factor (XLF) to bridge or align two DNA ends. Mutations in XRCC4 were identified in patients with developmental diseases, showing microcephaly and growth defects. There are also reports showing that a polymorphism in XRCC4, which changes its subcellular localization, is associated with increased cancer risk. This study aimed to explore the role in DNA repair function of XRCC4 and its association in disease development and protection against cancer. XRCC4 mutants mimicking these disease-associated mutants and cancer risk-associated variants were generated and expressed in murine and human osteosarcoma cell lines. Then, functional characteristics, i.e., protein expression, radiosensitivity and subcellular distribution were analyzed. Results showed that these disease-associated mutants showed varying degrees of dysfunction, depending upon the positions of its mutations, the length of deletions, or its proximity to significant positions associated to other NHEJ protein. Cancer risk-associated variant showed reduced DSB repair function. These results highlighted the significance of XRCC4 in the regulation of normal development and protection against cancer through DNA repair, and in maintaining genomic integrity and stability.

Zablackaite Giedre

The FPs transport from the bubbles to the water pool depends not only on the retention mechanisms inside the bubble, but also on the bubble hydrodynamics. Pool scrubbing codes, determining the efficiency of pool scrubbing effect, combine FPs aerosol transport models with bubble hydrodynamic models. In the codes, pool scrubbing efficiency is obtained from deposition velocities of several FPs aerosol retention mechanisms, such as inertial impaction, gravitational sedimentation, Brownian diffusion and steam condensation. The deposition velocities depend on bubble size and bubble rising velocity. All pool scrubbing codes adopted a single bubble model. However, the validity of the used single bubble diameters has not been verified. In this dissertation, the rising bubble hydrodynamic behaviour under the prototypical SA conditions of temperature, non-condensable gas content, submergence, downcomer diameter and pressure was investigated and suitable bubble diameter represented by Sauter Mean Diameter and corresponding bubble rising velocity was provided for single bubble model in pool scrubbing codes. The data base of SMD and bubble rising velocity corresponding to SMD was obtained and used for evaluation of the effects of varied parameters and investigate the importance of retention mechanisms. Proposed SMD was validated by using direct DF measurement data under a wide range of conditions presented in the reference. Moreover, experimental data was also collected under depressurization and used for evaluation of depressurization condition effect on bubble parameters and evaluation of pool scrubbing deterioration under depressurization condition. Based on the experimental results, recommendations were proposed for severe accident management concerning wetwell venting.

遺伝情報を司るDNAには、複製エラーなどの内因性、放射線や紫外線などの外因性ストレスによって、絶えずさまざまな損傷が生じている。細胞はそれらのDNA 損傷を迅速に認識・正確に修復することで、遺伝情報を維持し、ゲノムの安定性を保っている。一方、不正確あるいは不完全なDNA修復による突然変異の蓄積が遺伝病や発がん、がんの悪性化の原因となると考えられている。

2011年3月の東日本大震災における津波を契機に発生した福島第一原発事故では1, 2, 3号機が燃料溶融を伴うシビアアクシデントに至った。事故進展事象の解明および炉内における燃料溶融固化物の分布を推定する目的で実施された解析コードによる評価では，事故炉格納容器内部調査によって観察された原子炉圧力容器(RPV)破損状況の一部を説明することができず，事故後約10年が経過した現在においても炉心損傷からRPV破損に至る機構の全容解明には至っていない。本研究では福島第一原発事故の事故進展，沸騰水型軽水炉に特有な構造および燃料系金属融体の化学的特性に着目し，事故以前の知見とは異なる視点からRPV破損機構にいたる現象について熱力学計算および熱流動解析を用いて検証した。

Kim Min Seok

Determination of uranium in solid matrixes is one of the critical issues for the decommissioning of nuclear facilities. Since general analytical technologies of uranium have some disadvantages such as complex and time-consuming chemical operations and production of large amounts of secondary wastes, new rapid and simple and environmentally-friendly method should be required. In this study, I aimed to develop a novel separation and analysis system for uranyl ion (UO₂²⁺) included in solid matrix, utilized by fluorogenic chemosensor and supercritical carbon dioxide (ScCO₂) medium. As a UO₂²⁺ selective sensor material, this study employed novel PN-DCE bearing a diaza-18-crown-6 ether and two N-phenyl-1,8-naphthalimides. The synthesis of PN-DCE was performed by a series of solvent-free reaction and column-chromatography, and obtained PN-DCE was characterized by analytical methods such as ¹H-, ¹³C-NMR, elemental analysis. PN-DCE showed superior selectivity toward UO₂²⁺ among various alkali and alkaline earth metal ion species, in sensor property investigation. Also, its fine detection sensitivity was proven by Stern-Volmer analysis, supporting the suitability of PN-DCE on determination of clearance level UO₂²⁺ (1 Bq g^-1) in solid matrix. Moreover, direct extraction of UO₂²⁺ from solid waste matrixes was realized by using ScCO₂ medium and environmentally-friendly extractant, 2-pyrrolidone derivative. The extracted UO₂²⁺ could be successfully determined by fluorogenic analysis using PN-DCE. Therefore, this system can act as a promising analytical tool for uranium in solid waste.

福島第一原子力発電所の燃料デブリ取り出し作業を進めるにあたり、万一臨界事故が発生した場合の影響を予め評価しておくことは重要である。しかしながら、これまでの臨界事故解析の需要は溶液燃料体系や一般的な原子炉体系にあったため、燃料デブリを対象とした臨界事故時の影響評価に関する知見は少なく、明らかになっていない点が多い。本研究の目的は、燃料デブリによる臨界事故時の影響評価を行う上で重要な因子を明らかにすることである。燃料デブリの特徴を適切に取り入れることができる空間依存動特性解析を中心に種々の解析を組み合わせることで、燃料デブリによる臨界事故時の影響評価を行う上で重要な因子が明らかになった。

福島第一発電所廃止措置における燃料デブリ取り出し作業において、未臨界の担保は安全な作業に重要である。これまでの臨界評価手法は、燃料デブリの水中挙動を正確に考慮していないため評価精度に改善の余地がある。本研究の目的は、粒子法と中性子輸送モンテカルロ法の結合による燃料デブリ水中挙動を考慮した臨界計算手法の確立し本手法の有効性を明らかにすることである。本研究では粒子法シミュレーションの妥当性を実験と計算の比較によって評価した。また中性子輸送モンテカルロ法を組み合わせることで、水中挙動を考慮した臨界評価手法を確立し、さらに想定される取り出し作業条件下において本手法を適用することでその有効性を示した。