Analyzing reactor water level measurements in the Fukushima Daiichi 1 accident

Tuomo Sevón

doi:10.1016/j.pnucene.2023.104707

Analyzing reactor water level measurements in the Fukushima Daiichi 1 accident

Tuomo Sevón (Corresponding Author)

BA4503 Severe accident analysis

Research output: Contribution to journal › Article › Scientific › peer-review

3 Citations (Scopus)

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Abstract

Measuring the water level in the Fukushima Daiichi reactors was based on measuring the pressure difference between two pipes, connected to the reactor at different elevations and filled with water. Boiling of the water in the measurement system distorted the measurements. The water level readings during the unit 1 accident were analyzed with the MELCOR code. The behavior of the measurement system can be reproduced by assuming a small leak of superheated steam from a steam line to the drywell before 6.5 h after the earthquake. This confirms earlier conclusions of a Japanese accident investigation committee and analyses performed by TEPCO. The steam leak did not have any significant effect on the cesium release to the environment.

Original language	English
Article number	104707
Number of pages	6
Journal	Progress in Nuclear Energy
Volume	160
DOIs	https://doi.org/10.1016/j.pnucene.2023.104707
Publication status	Published - Jun 2023
MoE publication type	A1 Journal article-refereed

Keywords

BWR
Fukushima Daiichi
MELCOR
Reactor water level measurement

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10.1016/j.pnucene.2023.104707Licence: CC BY

j.pnucene.2023.104707Final published version, 603 KBLicence: CC BY

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title = "Analyzing reactor water level measurements in the Fukushima Daiichi 1 accident",

abstract = "Measuring the water level in the Fukushima Daiichi reactors was based on measuring the pressure difference between two pipes, connected to the reactor at different elevations and filled with water. Boiling of the water in the measurement system distorted the measurements. The water level readings during the unit 1 accident were analyzed with the MELCOR code. The behavior of the measurement system can be reproduced by assuming a small leak of superheated steam from a steam line to the drywell before 6.5 h after the earthquake. This confirms earlier conclusions of a Japanese accident investigation committee and analyses performed by TEPCO. The steam leak did not have any significant effect on the cesium release to the environment.",

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author = "Tuomo Sev{\'o}n",

note = "Funding Information: Funding for the work was obtained from SAFIR2022, the Finnish research programme on nuclear power plant safety. The analysis work has greatly benefited from the plant data obtained from the OECD NEA project BSAF-2, and from the discussions in the BSAF-2 and ARC-F project meetings.",

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N2 - Measuring the water level in the Fukushima Daiichi reactors was based on measuring the pressure difference between two pipes, connected to the reactor at different elevations and filled with water. Boiling of the water in the measurement system distorted the measurements. The water level readings during the unit 1 accident were analyzed with the MELCOR code. The behavior of the measurement system can be reproduced by assuming a small leak of superheated steam from a steam line to the drywell before 6.5 h after the earthquake. This confirms earlier conclusions of a Japanese accident investigation committee and analyses performed by TEPCO. The steam leak did not have any significant effect on the cesium release to the environment.

AB - Measuring the water level in the Fukushima Daiichi reactors was based on measuring the pressure difference between two pipes, connected to the reactor at different elevations and filled with water. Boiling of the water in the measurement system distorted the measurements. The water level readings during the unit 1 accident were analyzed with the MELCOR code. The behavior of the measurement system can be reproduced by assuming a small leak of superheated steam from a steam line to the drywell before 6.5 h after the earthquake. This confirms earlier conclusions of a Japanese accident investigation committee and analyses performed by TEPCO. The steam leak did not have any significant effect on the cesium release to the environment.

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Analyzing reactor water level measurements in the Fukushima Daiichi 1 accident

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Keywords

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