13343 research outputs found
Sort by
Basic Study on PWR Plant Behavior under the Condition of Severe Accident（1）
No full textIn this paper, we report on the results using the PWR plant simulator about the plant behavior under the condition of the severe accident that LOCA occurs but ECCS fails the water irrigation into the reactor core. As for the results about the relationship between the LOCA area and the time from LOCA occurs until fuel temperature rise start, the time became shorter as the area was the larger. But, in LOCA area of 1000cm2 or more large, the time was almost constant regardless of the area. For small LOCA of 25cm2 area, from the results of the comparative experiments for RCS natural circulation cooling effect in the case of SG open or not, in SG open condition compared with SG not open, the effect was observed more, but the reactor water level was greatly reduced and the time until the fuel temperature rise start was shortened, so the fuel temperature at the time of water irrigation into the reactor core has become higher. On the other hand, for the large LOCA of 1000cm2, the effect was not observed regardless of SG open or not. In addition, the reactor core damage was not spared in the irrigation into the reactor core after 30 minutes from LOCA, however, the hydrogen concentration in the containment building is less than the lower limit of hydrogen detonation, and also the pressure in the containment building is less than the designed value. That is, although suffered the core damage, the integrity of the containment building has been shown to be secured
Basic Study on BWR Plant Behavior under the Condition of Severe Accident（1）
No full textIn this paper, we report on the results using the BWR plant simulator about the plant behavior under the condition of the severe accident that LOCA occurs but ECCS fails the water irrigation into the reactor core. The simulation experiments were carried out for the cases that LOCA has occurred in the main steam piping or in the recirculation piping, respectively. As for the results about the relationship between the LOCA area and the time from LOCA occurs until the fuel temperature rise start, the effect that RCIC operated was extremely big for LOCA area of up to 100cm2 for both type LOCA. In the case of main steam system LOCA, the core water level suddenly decreased for large LOCA of 2000cm2 area, however, if the irrigation into the reactor core was carried out 30min after LOCA occurrence, the core had little damage. In addition, the H2 concentration in the containment vessel did not exceed both limits of H2 explosion nor detonation. The pressure of the containment vessel was around 3kg/cm2 of design value, so the soundness of the containment vessel was confirmed. On the other hand, for the recirculation system LOCA of 2000cm2 area, a drop of the core water level was extremely in comparison with main steam system LOCA, and the fuel assemblies were completely exposed during up to 30min. to the irrigation from approximately 100sec. after LOCA occurrence. Therefore, the fuel temperature during the irrigation had reached approximately 1900℃. Thus, the fuel cladding were damaged approximately less than 10%, and H2 concentration in the containment vessel was approximately 9% which did not exceed H2 detonation limit of 13% but exceeded H2 explosion limit of 4%. However, the containment vessel internal pressure was settled around design pressure value of containment vessel. As the results, some core damage could not be avoided, but soundness of the containment vessel, which should take the role of "confine", was found to be secured
Notes on the Specificity of the English Demonstrative that
No full textThe Present-day English demonstratives that and this derive from the Old English demonstratives se and þes respectively. In the history of the English language the Old English þes relatively simply developed into the Modern English this where as the Old English se extended its grammatical functions in the course of development. For example, se produced the definite article the and was diverted to a relative and a conjunction. These extended functions result from the definiteness and distant reference that the word involves
マイクロドーズマンモグラフィーへの移行により低減した被ばく線量と延長した乳房圧迫時間ー旧装置との比較によりー
No full text当院の乳房X線撮影装置は、国内導入3台目となるマイクロドーズマンモグラフィL130（MicroDose Mammography:MDM)である。従来のディジタルマンモグラフィ装置とは異なり、新技術フォトンカウンティングを採用している。ファントム及び臨床患者において被ばく線量を従来型旧装置と比較したところ、平均乳腺線量が1/2以下になり、被ばく線量低減を実現した。しかし、MDMはスキャニング方式によるXsenn 照射のため、受診者の苦痛因子である乳房圧迫時間の延長が懸念される。臨床患者において調べたところ、実際の圧迫時間は平均14秒であることがわかった。平均的な乳房厚とされる42㎜を超える乳房では、スキャン時間と乳房厚には有意な相関関係がみられ、乳房厚の増加がスキャン時間延長の要因になっていると考えられた。一方、乳腺密度で分類した患者群の平均スキャン時間はいずれも9秒前後と大きな差はみられず、乳腺密度が高くなるにつれて乳房厚が薄くなったためと考えられた
A Disaster Communication System using Ad-hoc Mesh Network
No full textIn this article, we propose a disaster communication system using ad-hoc network and mesh network.
In this system, we use the Etherphone which is new communication technology using only the
data link layer and the physical layer. The Etherphone network uses a broadcast for the transmission
of a message of data. We produced mobile communication terminal equipment by using Etherphone.
We built an alternative communication network at the time of disaster by constructing mobile ad-hoc
network which using wireless multi-hop communication. We demonstrated that the mobile communication
terminal equipment can take ad-hoc communication in alternative communication network
at the time of disaster