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Journal Articles

Review of Fukushima Daiichi Nuclear Power Station debris endstate location in OECD/NEA preparatory study on analysis of fuel debris (PreADES) project

Nakayoshi, Akira; Rempe, J. L.*; Barrachin, M.*; Bottomley, D.; Jacquemain, D.*; Journeau, C.*; Krasnov, V.; Lind, T.*; Lee, R.*; Marksberry, D.*; et al.

Nuclear Engineering and Design, 369, p.110857_1 - 110857_15, 2020/12

 Times Cited Count:0 Percentile:0.33(Nuclear Science & Technology)

Much is still not known about the end-state of core materials in each of the units at Fukushima Daiichi Nuclear Power Station (Daiichi) that were operating on March 11, 2011. The Nuclear Energy Agency of the Organization for Economic Development has launched the Preparatory Study on Analysis of Fuel Debris (PreADES) project as a first step to reduce some of these uncertainties. As part of the PreADES Task 1, relevant information was reviewed to confirm the accuracy of graphical depictions of the debris endstates at the damaged Daiichi units, which provides a basis for suggesting future debris examinations. Two activities have been completed within the PreADES Task 1. First, relevant knowledge from severe accidents at the Three Mile Island Unit 2 and the Chernobyl Nuclear Power Plant Unit 4 was reviewed, along with results from prototypic tests and hot cell examinations, to glean insights that may inform future decommissioning activities at Daiichi. Second, the current debris endstate diagrams for the damaged reactors at Daiichi were reviewed to confirm that they incorporate relevant knowledge from plant observations and from severe accident code analyses of the BSAF (Benchmark Study of the Accident at Daiichi Nuclear Power Station) 1 and 2 projects. This paper highlights Task 1 insights, which have the potential to not only inform future Decontamination and Decommissioning activities at Daiichi, but also provide important perspectives for severe accident analyses and management, particularly regarding the long term management of a damaged nuclear site following a severe accident.

Journal Articles

Comprehensive analysis and evaluation of Fukushima Daiichi Nuclear Power Station Unit 2

Yamashita, Takuya; Sato, Ikken; Honda, Takeshi*; Nozaki, Kenichiro*; Suzuki, Hiroyuki*; Pellegrini, M.*; Sakai, Takeshi*; Mizokami, Shinya*

Nuclear Technology, 206(10), p.1517 - 1537, 2020/10

 Times Cited Count:5 Percentile:89.87(Nuclear Science & Technology)

Journal Articles

Main findings, remaining uncertainties and lessons learned from the OECD/NEA BSAF Project

Pellegrini, M.*; Herranz, L.*; Sonnenkalb, M.*; Lind, T.*; Maruyama, Yu; Gauntt, R.*; Bixler, N.*; Morreale, A.*; Dolganov, K.*; Sevon, T.*; et al.

Nuclear Technology, 206(9), p.1449 - 1463, 2020/09

 Times Cited Count:11 Percentile:98.02(Nuclear Science & Technology)

Journal Articles

Main findings, remaining uncertainties and lessons learned from the OECD/NEA BSAF Project

Pellegrini, M.*; Herranz, L.*; Sonnenkalb, M.*; Lind, T.*; Maruyama, Yu; Gauntt, R.*; Bixler, N.*; Morreale, A.*; Dolganov, K.*; Sevon, T.*; et al.

Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.1147 - 1162, 2019/08

Journal Articles

Development of the source term PIRT based on findings during Fukushima Daiichi NPPs accident

Suehiro, Shoichi*; Sugimoto, Jun*; Hidaka, Akihide; Okada, Hidetoshi*; Mizokami, Shinya*; Okamoto, Koji*

Nuclear Engineering and Design, 286, p.163 - 174, 2015/05

 Times Cited Count:12 Percentile:79.22(Nuclear Science & Technology)

The severe accident evaluation committee of AESJ (Atomic Energy Society of Japan) developed the thermal hydraulic PIRT (Phenomena Identification and Ranking Table) and the source term PIRT based on findings during the Fukushima Daiichi NPPs accident. These PIRTs aimed to explore the debris distribution and the current condition in the NPPs with high accuracy and to extract higher priority from the aspect of the sophistication of the analytical technology to predict the severe accident phenomena by the code. The ST PIRT was divided into 3 phases for the time domain and 9 categories for the spatial domain. The 68 phenomena were extracted and the importance from viewpoint of the source term was ranked through brainstorming and discussion. This paper described the developed ST PIRT list and summarized the high ranked phenomena in each phase.

Journal Articles

Study on gas-liquid two-phase flow distribution in a tight-lattice rod bundle

Onuki, Akira; Shibata, Mitsuhiko; Tamai, Hidesada; Akimoto, Hajime; Yamauchi, Toyoaki*; Mizokami, Shinya*

Nihon Konsoryu Gakkai Nenkai Koenkai 2003 Koen Rombunshu, p.35 - 36, 2003/07

Analytical evaluation of maximum critical power by so-called subchannnel code is indispensable for design of reduced moderation water reactor. In this study, two-phase flow distribution in a tight-lattice rod bundle is investigated using 19-rod bundle experimental rig and subchannnel analysis code NASCA. The flow distribution was measured under so-called churn flow regime and the predictive capability of NASCA was assessed. NASCA can predict the flow distribution qualitatively depending on local pressure drop. Quantitative prediction is also reasonable for liquid phase but the gas phase distribution was underestimated. Void-drift model has a dominant contribution and we should improve the model for the tight-lattice rod bundle.

Oral presentation

Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident, 1; Cesium chemistry team formation and research plan

Mizokami, Shinya; Osaka, Masahiko; Ito, Kenichi*; Karasawa, Hidetoshi*; Honda, Takeshi*

no journal, , 

Overview of the activity conducted in the project (Upgrading level of grasping state inside reactor) by cesium chemistry team will be introduced as a start point of the series presentation.

Oral presentation

Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident, 10; Phenomenological generation mechanisms of spherical cesium bearing particle

Ito, Kenichi*; Suzuki, Akihiro*; Oishi, Yuji*; Nakamori, Fumihiro*; Hikida, Shiro*; Nozaki, Kenichiro*; Honda, Takeshi*; Mizokami, Shinya

no journal, , 

The spherical cesium bearing particles (insoluble Cs particles), which were found in Fukushima and Tokyo area, are considered to be formed in RPV of Fukushima Daiichi NPS unit2 because of its composition and microstructural characteristic that needs quench from high temperature.

Oral presentation

Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident, 11; Analysis of samples from containment in Fukushima Daiichi NPS

Maeda, Koji; Mizokami, Masato*; Suzuki, Akihiro*; Ito, Kenichi*; Sato, Ikken; Mizokami, Shinya*

no journal, , 

Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident was performed. Especially, analysis of samples from containment in Fukushima Daiichi NPS was evaluated.

Oral presentation

Assessment of core status of TEPCO's Fukushima Daiichi Nuclear Power Plants, 115; Integrated evaluation of fuel debris remaining inside the RPV and the PCV; Unit2

Yamashita, Takuya; Honda, Takeshi*; Mizokami, Shinya*; Nozaki, Kenichiro*; Suzuki, Hiroyuki*; Pellegrini, M.*; Sakai, Takeshi*

no journal, , 

no abstracts in English

Oral presentation

Assessment of core status of TEPCO's Fukushima Daiichi Nuclear Power Plants, 113; Integrated evaluation of fuel debris remaining inside the RPV and the PCV; Unit3

Mizokami, Shinya*; Honda, Takeshi*; Nozaki, Kenichiro*; Sakai, Takeshi*; Yamashita, Takuya; Pellegrini, M.*; Suzuki, Hiroyuki*

no journal, , 

no abstracts in English

Oral presentation

Assessment of core status of TEPCO's Fukushima Daiichi Nuclear Power Plants, 114; Integrated evaluation of fuel debris remaining inside the RPV and the PCV; Unit1

Sakai, Takeshi*; Mizokami, Shinya*; Honda, Takeshi*; Nozaki, Kenichiro*; Yamashita, Takuya; Pellegrini, M.*; Suzuki, Hiroyuki*

no journal, , 

no abstracts in English

Oral presentation

Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident, 12; Analysis of nuclides in samples collected from primary containment vessel of Unit 1

Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*

no journal, , 

no abstracts in English

Oral presentation

Analysis of nuclides in deposition collected from primary containment vessel of Fukushima Daiichi unit 1

Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*

no journal, , 

no abstracts in English

Oral presentation

Analysis results on samples obtained inside PCV and relatively high dose materials in Fukushima Daiichi unit 1 to 3

Mizokami, Masato*; Suzuki, Akihiro*; Maeda, Koji; Ito, Kenichi*; Sato, Ikken; Mizokami, Shinya*

no journal, , 

Some radioactive material samples were taken inside the PCV of Fukushima Daiichi Units 1-3. TEPCO is working for sample collection, transport, and detailed examinations at hot cells using SEM, TEM and ICP-MS. Uranium-bearing micro-particles were analysed using SEM and Emit was confirmed that particles derived from fuel can be categorized into two groups. One is believed to have been separated from hot corium by hydrodynamic processes, while the other showed characteristics suggesting evaporation from hot corium and condensation afterward. The former particles might have compositional features common to the major part of fuel debris. Both groups possibly cause alpha contamination (actinide behavior) in the reactor building.

Oral presentation

Analysis of samples collected in PCV interior of Fukushima Daiichi NPP, 3; Nuclide analysis of samples collected in PCV interior

Sasaki, Shinji; Maeda, Koji; Morishita, Kazuki; Onishi, Takashi; Sato, Ikken; Mizokami, Masato*; Mizokami, Shinya*

no journal, , 

no abstracts in English

Oral presentation

Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident, 13; Chemical analysis of samples collected from the operating floor of the reactor building of Unit 2

Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*

no journal, , 

Samples, collected from the operating floor of the reactor building of Fukushima Daiichi Unit 2, were immersed in deionized water and nitric acid. Immersed solutions were analyzed by gamma-ray spectrometry and ICP-MS. Analyses suggest small amount of Fe, Mn and Cu derived from structural materials of nuclear reactor, and Te, Cs and U derived from spent fuels.

Oral presentation

Analysis of samples collected in PCV interior of Fukushima Daiichi NPP, 6; Use of analysis results of collected samples toward fuel debris retrieval

Kurata, Masaki; Madokoro, Hiroshi; Okumura, Keisuke; Sato, Ikken; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*

no journal, , 

Based on the analysis of the samples collected in the PCV interior of Fukushima Daiichi NPP, potential issues regarding the fuel debris retrieval are summarized. The analytical targets, analytical method and obtainable knowledge that are necessary to evaluate each issue are discussed. Valuable information can be obtained even from small samples to understand the current situation of the plant and the accident progression. Although the amount of collectable samples is limited, we considered how to evaluate the whole fuel debris and how to utilize the analytical results for recriticality, burnup and safety issues.

Oral presentation

Analysis results on samples obtained inside PCV in Fukushima Daiichi Nuclear Power Plant

Mizokami, Masato*; Ito, Kenichi*; Suzuki, Akihiro*; Sato, Ikken; Kurata, Masaki; Hirai, Mutsumi*; Mizokami, Shinya*

no journal, , 

no abstracts in English

Oral presentation

Whole core three-dimensional nuclide inventory calculation of the Fukushima Daiichi Nuclear Power Station, 1; Background and purpose

Okumura, Keisuke; Sakamoto, Masahiro; Tada, Kenichi; Nishihara, Kenji; Mizokami, Shinya*; Mizokami, Masato*; Miki, Yosuke*; Kaneko, Seiji*

no journal, , 

no abstracts in English

23 (Records 1-20 displayed on this page)