Safety insights from forensics evaluations at Daiichi

Rempe, Joy L.; Corradini, Michael L.; Farmer, M. T.; Gabor, J.; Gauntt, Randall O.; Hara, Takaya; Luangdilok, W.; Lutz, Robert J.; Luxat, David; Mizokami, Shinya; Plys, M.G.; Robb, Kevin; Tateiwa, K.; Yamanaka, Yasunori

doi:10.1016/j.nme.2016.08.010

Cited by 12 publications

(10 citation statements)

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“…During FY2019, the US expert panel reviewed Attachment [3][4][5][6][7][8][9] of Reference [53], which documents TEPCO Holdings analyses to estimate 1F3 RPV water levels at the time of core damage and core melt. U.S. experts in plant operations find the TEPCO Holdings approach similar to that used for 1F2 in Attachment [2][3][4][5][6][7][8][9][10][11][12][13][14] of Reference [53], and results are similar to those described in Section 7.2.4.2.…”

Section: Resultsmentioning

confidence: 91%

“…During FY2019, the US expert panel also reviewed Attachment [1][2][3][4][5][6][7][8][9][10][11] of Reference [53], which documents the TEPCO Holdings use of air dose rate monitoring, along with other plant instrumentation data, to better understand the 1F1 accident progression. US experts in plant operation found this investigation to be very thorough.…”

Section: Resultsmentioning

confidence: 99%

“…During FY2019, the US expert panel reviewed Attachment [1][2][3][4][5][6][7][8][9][10][11] of Reference [53], which documents the TEPCO Holdings analysis to estimate 1F2 RPV water level at the time of core damage and core melt progression. This work agrees with evaluations documented in Section 7.2.4.2 that indicate that RPV water level had lowered to BAF or below by 18:22 on March 14, 2011.…”

Section: Resultsmentioning

confidence: 99%

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U.S. Efforts in Support of Examinations at Fukushima Daiichi: 2019 Evaluations

Amway¹,

Andrews²,

Basu³

et al. 2019

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Much is still not known about the end-state of core materials in each unit that was operating on March 11, 2011 at the Fukushima Daiichi Nuclear Power Station (Daiichi). Information obtained from Daiichi is required to inform Decontamination and Decommissioning (D&D) activities, improving the ability of the Tokyo Electric Power Company Holdings, Incorporated (TEPCO Holdings) to characterize potential hazards and to ensure the safety of workers involved with cleanup activities. This document, which has been updated to include Fiscal Year 2019 (FY2019) information, summarizes results from a U.S. effort to review Daiichi information and extract insights to enhance the safety of existing and future nuclear power plant designs. This U.S. effort, which was initiated in 2014 by the Department of Energy Office of Nuclear Energy (DOE-NE), is completed by a group of experts in reactor safety and plant operations that identify examination needs and evaluate recent Daiichi examination data to address these needs. Each year, annual reports are issued that document significant safety insights being obtained in areas of special emphasis. For FY2019, the areas emphasized by the expert panel include component performance, radionuclide surveys and sampling, debris end-state location, combustible gas effects, and plant operations and maintenance. In addition to reducing uncertainties related to severe accident modeling progression, these insights have and continue to be used to update guidance for severe accident prevention, mitigation, and emergency planning. Reduced uncertainties in modeling the events at Daiichi improve the realism of reactor safety evaluations that inform future D&D activities. In addition, the process established by this U.S. effort provides an example that Japan may wish to implement in future international efforts to support D&D.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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U.S. Efforts in Support of Examinations at Fukushima Daiichi: 2019 Evaluations

Amway¹,

Andrews²,

Basu³

et al. 2019

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“…As indicated above, there are several potential safety benefits from this U.S. effort. In fact, as discussed in [2,3,4,5] and within this document, the U.S. has already gained significant safety benefit from information obtained from the affected reactors at Daiichi.…”

Section: Objectives and Limitationsmentioning

confidence: 99%

“…To a first order, this data can be used to estimate the amount of core material remaining in the RPV. For an assumed core mass of 240 metric tons, the debris volume would be ~34 m 3 . Based on the dimensions provided in Figure 63, the volume of the spherical lower head is calculated to be ~33 m 3 (which neglects CRD structures in the lower head volume).…”

Section: F2 Examinationsmentioning

confidence: 99%

Light Water Reactor Sustainability Program, U.S. Efforts in Support of Examinations at Fukushima Daiichi-2017 Evaluations

Farmer

2017

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Although the accident signatures from each unit at the Fukushima Daiichi Nuclear Power Station (NPS) [Daiichi] differ, much is not known about the end-state of core materials within these units. Some of this uncertainty can be attributed to a lack of information related to cooling system operation and cooling water injection. There is also uncertainty in our understanding of phenomena affecting: a) in-vessel core damage progression during severe accidents in boiling water reactors (BWRs), and b) accident progression after vessel failure (ex-vessel progression) for BWRs and Pressurized Water Reactors (PWRs). These uncertainties arise due to limited full scale prototypic data. Similar to what occurred after the accident at Three Mile Island Unit 2, these Daiichi units offer the international community a means to reduce such uncertainties by obtaining prototypic data from multiple full-scale BWR severe accidents.Information obtained from Daiichi is required to inform Decontamination and Decommissioning activities, improving the ability of the Tokyo Electric Power Company Holdings, Incorporated (TEPCO Holdings) to characterize potential hazards and to ensure the safety of workers involved with cleanup activities. This document, which has been updated to include FY2017 information, summarizes results from U.S. efforts to use information obtained by TEPCO Holdings to enhance the safety of existing and future nuclear power plant designs. This effort, which was initiated in 2014 by the Reactor Safety Technologies Pathway of the Department of Energy Office of Nuclear Energy Light Water Reactor (LWR) Sustainability Program, consists of a group of U.S. experts in LWR safety and plant operations that have identified examination needs and are evaluating TEPCO Holdings information from Daiichi that address these needs. Each year, annual reports include examples demonstrating that significant safety insights are being obtained in the areas of component performance, fission product release and transport, debris end-state location, and combustible gas generation and transport. In addition to reducing uncertainties related to severe accident modeling progression, these insights are being used to update guidance for severe accident prevention, mitigation, and emergency planning. Furthermore, reduced uncertainties in modeling the events at Daiichi will improve the realism of reactor safety evaluations and inform future D&D activities by improving the capability for characterizing potential hazards to workers involved with cleanup activities.Highlights in this FY2017 report include new insights with respect to the forces required to produce the observed Daiichi Unit 1 (1F1) shield plug endstate, the observed leakage from 1F1 components, and the amount of combustible gas generation required to produce the observed explosions in Daiichi Units 3 and 4 (1F3 and 1F4). This report contains an appendix with a list of examination needs that was updated after U.S. experts reviewed recently obtained information from examinations at Daiichi. A...

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