The total system design on Nuclear Plant ensures “Nuclear safety” with making practically achievable efforts to prevent and mitigate nuclear and radiological accidents. The performance based system design with “Defence in depth (D-I-D)” has been laid out as the key means in “preventing accidents”, “controlling escalation to serious consequences”, and “preventing harmful consequences to the public”. D-I-D is extended to the management of severe accidents, and is an approach intended to provide protection...
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Development of Resilience Evaluation Method for Nuclear Power Plant (Part4: Concept of System Safety on Operating Nuclear Power Plants)

In view of the severe consequences of TEPCO’s Fukushima Dai-ichi NPP accident, a new framework for the continuous enhancement of severe accident management (for beyond design basis accidents involving significant fuel damage) should be established for the operation of existing plants in Japan. Preparedness and response measures for addressing extreme natural disasters as large-scale earthquakes and tsunamis, and for other severe accident initiators should be formulated quickly, properly, and in good sequen...
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Nuclear Safety Assessment of Nuclear Operating Plants after Fukushima No.1 NPS Tsunami Accident

はじめに 2011 年 3 月 11 日に発生した東北地方太平洋沖地震は 日本周辺における観測史上最大の地震となり [1]、この 地震に伴い発生した津波が東京電力福島第一原子力発電 所(以下、1F)を襲った。1F は全交流電源喪失状態に陥り、 原子炉内部や核燃料プールへの注水を行えず、原子炉を 冷却できなくなったことで炉心溶融に陥り、最終的には 大気中、土壌、溜まり水、立坑、海水、および地下水へ の広範囲に渡る放射性物質の放出事故に至った。この事 故は国際原子力事象評価尺度 (INES: Internat......

１．はじめに本解説記事は、（独）原子力安全基盤機構から日本保全学会が委託された課題「保全方式の妥当性に関する調査・検討」を受けて発足した「原子力発電所の保全方式の妥当性に関する調査・検討委員会」において平成18年2月～5月の期間に開催した2回の委員会、4回のワーキンググループ、および7回の幹事会での調査・検討の成果としての報告書を元に、その内容を要約したものである。献身的にご貢献頂きました皆様には心よりの感謝を申し上げます。２．保全方式の種類　原子力発電所を含む大型プラントにおいて採用されている保全方式と......

Che draft guideline for managing the leakage from seal portions of equipment in nuclear power plant has be en eveloped by the special research committee of Japan society of maintenology (ISM). In this paper, the o utline f this guideline is shown and the technical backgrounds and key points including leak management pr ocess, leak ate measurement methods, leak rate prediction method, acceptance criteria, etc. are discussed....
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Development of a Guideline for managing Leakage from Seal Portions of Equipment in Nuclear Power Plants

Our portable X-band (9.3GHz) 950KeV linac has been successfully upgraded. The problems of RF power oscillation , beam current oscillation and reduction and finally lack of X-ray intensity were solved by replacing the axia l coupling cavities with the side-coupled ones. Designed X-ray dose rate of 0.05 Sv/min@lm is going to be achi eved. Length of the accelerating tube is reduced to less than 25 cm. X-ray source part with the local radiation shielding is connected by the flexible waveguide with the box of t...
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Study on Portable X-band 950keV linac X-ray Sourcefor On-site Nondestructive Inspection

After Fukushima accident in 2011, demand in a design and management to predict severe accidents like Fukushima accident have been realized. To realize them, we must clarify fracture event of reactor pressure v essels or containment vessels. However, the mechanism of failure of structure under severe condition like overpressure or hyperthermia is not clear completely. If we can to predict damage or failure causing se vere accidents in advance by some method, we can take some measures retaining soundness of ...
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Image analysis for the deformation of a specimen with tensile loading

Under the influence of the F1 accident, there is a growing threat to nuclear security. Among the nuclear security threat, current sensing technique is not effective to sabotage by an insider. In this research, for the purpose of detection of dangerous behavior, dealing with the time-series data. The analysis of the data using PCA(Principal Component Analysis) and SBM(Similarity Based Modeling), was determined for several types of motion....
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Development of malicious behavior detection method by using time-series data

Sabotage by malicious insider is one of significant and serious threats for nuclear security of nuclear power plants. It is difficult, however, to distinguish abnormal behaviors from normal works such as their daily maintenance activities. In this study, a technique was proposed to subdivide the abnormal behavior due to sabotage by image analysis and then to detect and identify the abnormal behavior in real time. ...
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Proposal of Insider Detection Method for Nuclear Security

Abstract After Fukushima accident, the threats of terrorism are increasing. However, countermeasures for insider terrorists are insufficient because the main target of Physical Protection System (PPS) is outsider. Thus development of automatic detection of insider terrorists is required. In this paper, focusing on the hand motion, final goal is image recognition by Convolutional Neural Network (CNN) and analysis of each finger’s position and angle and detection of signs of malicious behavior. And For ...
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Automatic Detection of Malicious Insider Behavior for Nuclear Security