Detailed observation of seawater precipitation with 5x5 mockup fuel bundle based on x-ray computated tomography technique

Retsu Kojo, Akitoshi Hotta, Masahiro Furuya, Miyuki Akiba, Harutaka Hoshi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Abstract

In order to conform to the new regulatory standard in Japan, seawater is regarded as the alternative water source both for BWRs (Boiling water reactors) and PWRs (Pressurized water reactors). For preventing further accident evolutions occurred in Fukushima Daiichi nuclear power plants, seawater was injected into the reactors for more than one week. With long-term seawater injection, sea salt compositions are condensed and many of them will precipitate when saturated concentrations are exceeded. Unlike corrosion issues, impacts of sea salt precipitation on the heat removal has not been studied widely in the past because it has not been regarded as the alternative water source before Fukushima Daiichi nuclear power plants accident. The existent knowledge base of boric acid precipitation under LOCA conditions was studied. Based on the existent study on impacts of boric acid precipitation under LOCA conditions, the experimental project of seawater consisting of four experiments was proposed. The existent database of physical properties, such as viscosity, of seawater is rather poor under severe accident conditions. In addition, it is likely that boric acid will be injected with water or seawater to prevent re-criticality. It is known that physical properties of boric acid vary widely under high temperature conditions. Measurement of viscosity of the seawater-boric acid mixture was conducted in high temperature using a rotational viscometer. Under conditions equivalent to the estimated bulk coolant conditions under a long-term cooling phase of severe accidents. In this range, no obvious change of viscosity is expected. Then a detailed structure of seawater precipitates was observed using a mockup fuel bundle with 5x5 in the square lattice and 500 mm in the length. Images of precipitates were taken using the X-ray CT. The water level, the concentration of sea salt and the heat flux are employed as experimental parameters. The heat flux, bubble stirring in downstream of spacers and heat loss by a non-heated channel box were identified as influential factors to local and overall precipitates in fuel bundles.

Original languageEnglish
Title of host publicationNuclear Education, Public Acceptance and Related Issues; Instrumentation and Controls (I and C); Fusion Engineering; Beyond Design Basis Events
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791845967
DOIs
Publication statusPublished - 2014
Externally publishedYes
Event2014 22nd International Conference on Nuclear Engineering, ICONE 2014 - Prague, Czech Republic
Duration: 2014 Jul 72014 Jul 11

Publication series

NameInternational Conference on Nuclear Engineering, Proceedings, ICONE
Volume6

Conference

Conference2014 22nd International Conference on Nuclear Engineering, ICONE 2014
CountryCzech Republic
CityPrague
Period14/7/714/7/11

ASJC Scopus subject areas

  • Nuclear Energy and Engineering

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  • Cite this

    Kojo, R., Hotta, A., Furuya, M., Akiba, M., & Hoshi, H. (2014). Detailed observation of seawater precipitation with 5x5 mockup fuel bundle based on x-ray computated tomography technique. In Nuclear Education, Public Acceptance and Related Issues; Instrumentation and Controls (I and C); Fusion Engineering; Beyond Design Basis Events (International Conference on Nuclear Engineering, Proceedings, ICONE; Vol. 6). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/ICONE22-30129