Boiled-up level and boiling two-phase flow dynamics in 5 × 5 heated rod bundle during boil-off process under atmospheric pressure conditions

Takahiro Arai, Masahiro Furuya, Taizo Kanai, Kenetsu Shirakawa, Yoshihisa Nishi

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

2 Citations (Scopus)

Abstract

In the case of an accident and when a water level of a reactor core falls below the top level of active fuel, the cooling limit height becomes a key factor for determining the accident mitigation procedure. To predict the cooling limit height, it is important to clarify a two-phase mixture level in a rod bundle during the boil-off process. The two-phase mixture level depends on the collapsed level and void fraction distribution. During the boil-off process, a boiling two-phase flow in the rod bundle exhibits multidimensional and complex flow structures. The paper addresses a three-dimensional void fraction distribution and a two-phase mixture level in 5 × 5 heated rod bundles during the boil-off process, under atmospheric pressure conditions. The heated rod length is 3.7 m, which is the same as the fuel rod in boiling water-reactor (BWR). The 5x5 rod bundles have an axially and radially uniform power profile, and eight pairs of sheath thermocouples are embedded in the heated rod to monitor their axial surface temperature profiles. The diameter of the heated rod is 10 mm, and the rod pitch is 13 mm. The void fraction distributions were acquired with eight pairs of subchannel void sensors (SCVS) as time series data. The two-phase mixture level was evaluated by side-viewing images acquired with two high-speed digital video cameras. The experimental result exhibits a relationship of the boiling two-phase flow dynamics to the two-phase mixture level, and the void fraction during the boil-off process.

Original languageEnglish
Title of host publicationInternational Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015
PublisherAmerican Nuclear Society
Pages7312-7322
Number of pages11
ISBN (Electronic)9781510811843
Publication statusPublished - 2015 Jan 1
Externally publishedYes
Event16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2015 - Chicago, United States
Duration: 2015 Aug 302015 Sep 4

Publication series

NameInternational Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015
Volume9

Other

Other16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2015
CountryUnited States
CityChicago
Period15/8/3015/9/4

Keywords

  • 5 × 5 heated rod bundle
  • Boil-off
  • Boiling two-phase flow
  • Two-phase mixture level
  • Void fraction

ASJC Scopus subject areas

  • Instrumentation
  • Nuclear Energy and Engineering

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    Arai, T., Furuya, M., Kanai, T., Shirakawa, K., & Nishi, Y. (2015). Boiled-up level and boiling two-phase flow dynamics in 5 × 5 heated rod bundle during boil-off process under atmospheric pressure conditions. In International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015 (pp. 7312-7322). (International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015; Vol. 9). American Nuclear Society.