Experimental Study on Thermal-Hydraulics During Start-Up in the Natural Circulation Boiling Water Reactor Concept: Effects of System Pressure and Increasing Heat Flux on the Geysering and Density Wave Oscillation

The feasibility study in thermal-hydraulics for the future light water reactor concept is carried out. One of the essential studies is the two-phase flow instability during start-up in the natural circulation boiling water reactor (BWR) concept. It is anticipated that the occurrence of the two-phase flow instabilities during start-up significantly affects the feasibility concept, since it would cause the complexity in raising and maneuvering the power output. The purpose of the current study is to experimentally investigate the driving mechanism of the geysering and density wave oscillation in the natural circulation loop, induced by a range of system operating pressure and increasing heat flux in vertical parallel channels. The pressure range of atmospheric up to about 4 bars, and the input heat flux range of 0 up to 577 kW/m2 are applied in these experiments. An experimental apparatus of twin boiling upflow channels to simulate natural circulation flow loop has been designed, constructed and operated. The natural circulation in the loop occurs due to the density difference between two-phase region in the channels and the single-phase liquid in the downcomer. The objective of the study is to propose a rational start-up procedure in which the geysering and density wave oscillation can be prevented during startup, according to its system pressure and heat flux. Previous studies have clarified that three (3) kinds of thermo-hydraulics instabilities may occur during start-up in the natural circulation BWR depending on its procedure and reactor configuration, which are (1) geysering induced by condensation, (2) natural circulation induced by hydrostatic head fluctuation in steam separator, and (3) density wave oscillation.

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Validation of TRACE Code for Flashing-Induced Density Wave Oscillations in SIRIUS-N Facility, Which Simulates ESBWR

Volume 3: Thermal-Hydraulics; Turbines, Generators, and Auxiliaries ◽

10.1115/icone20-power2012-55132 ◽

2012 ◽

Author(s):

Masahiro Furuya ◽

Yoshihisa Nishi ◽

Nobuyuki Ueda

Keyword(s):

Heat Flux ◽

Natural Circulation ◽

Stability Boundary ◽

Oscillation Amplitude ◽

Density Wave ◽

Stability Limit ◽

Type I ◽

Wave Oscillation ◽

System Pressure ◽

Density Wave Oscillations

The TRACE code was validated against the flashing-induced density wave oscillation in the SIRIUS-N facility at low pressure (from 0.1 to 0.5 MPa) as a part of the international CAMP-Program of USNRC. The SIRIUS-N facility is a scaled copy of natural circulation BWR (ESBWR). Stability map of TRACE agrees with that of SIRIUS-N facility at low subcooling region, though instability observed in the lower heat flux and higher subcooling region from the stability limit of experiment. The TRACE code demonstrates the flashing-induced density wave oscillation characteristics: The oscillation period correlates well with the transit time of single-phase liquid in the chimney regardless of the system pressure, inlet subcooling, and heat flux. Unlike Type-I and II density wave oscillations, the inlet or exit throttling does not affect stability boundary and oscillation amplitude of flashing-induced density wave oscillations significantly. Increasing pressure decreases oscillation amplitude. The comprehensive validation confirms that the TRACE code can demonstrate thermal-hydraulic stability of natural circulation BWRs.

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TWO-PHASE FLOW INSTABILITIES ANALYSES IN BOILING WATER REACTOR

10.26678/abcm.encit2016.cit2016-0140 ◽

2016 ◽

Author(s):

Antonella Lombardi Costa ◽

WILMER ARUQUIPA COLOMA ◽

Antonella Lombardi Costa ◽

Claubia Pereira ◽

Maria Veloso ◽

...

Keyword(s):

Two Phase Flow ◽

Boiling Water ◽

Flow Instabilities ◽

Boiling Water Reactor ◽

Phase Flow ◽

Two Phase ◽

Water Reactor

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Experimental Study on Two-Phase Natural Circulation Flow Instability in Rod Bundle Channel Under Low Pressure Condition

Volume 6A: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-81225 ◽

2018 ◽

Author(s):

Kun Cheng ◽

Sichao Tan ◽

Zheng Liu ◽

Tao Meng

Keyword(s):

Flow Instability ◽

Natural Circulation ◽

Oscillation Amplitude ◽

Density Wave ◽

Low Pressure ◽

Heating Power ◽

Pressure Condition ◽

Two Phase ◽

Rod Bundle ◽

System Pressure

An experimental investigation was conducted in a natural circulation (NC) loop to study the characteristics of two-phase flow instability under low pressure condition. A 3 × 3 rod bundle channel was used as the test section. The effects of heating power, inlet subcooling degree and system pressure on the two-phase NC flow instability types and stable boundaries were studied. The experimental results show that three typical flow conditions can occur in rod bundle channel under NC condition, which are single-phase NC flow, subcooled boiling NC flow oscillation and density wave oscillations (DWO). The oscillation amplitude and period of DWO can be enlarged by increasing the heat flux. Increasing the inlet subcooling degree can increase the marginal heating power of flow instability in NC system. The occurrence of DWO can be suppressed by increasing the system pressure. The flow instability boundary presented by the subcooling number and phase change number was also obtained in present work.

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The Influence of Non-Uniform Heating on Two-Phase Flow Instability in Parallel Channels

Volume 4: Thermal Hydraulics ◽

10.1115/icone21-15231 ◽

2013 ◽

Author(s):

Xiaodong Lu ◽

Linglan Zhou ◽

Hong Zhang ◽

Yingwei Wu ◽

Guanghui Su ◽

...

Keyword(s):

Heat Flux ◽

Two Phase Flow ◽

Flow Instability ◽

System Stability ◽

System Control ◽

Phase Flow ◽

Uniform Heating ◽

Two Phase ◽

System Pressure ◽

Parallel Channels

The two-phase flow instability in parallel channels heated by uniform and non-uniform heat flux has been theoretically studied in this paper. Based on the homogeneous flow model in two-phase region, the system control equations of parallel channels were established. Semi-implicit finite-difference method and staggered mesh method were used to discretize the system control equations and the difference equations were solved with a chasing method. The cosine profile and uniform constant heat flux represent the non-uniform and uniform heating condition, respectively. The marginal stability boundaries (MSB) of parallel channels and the three-dimensional instability spaces (or instability reefs) of different heat flux models were obtained. For cosine profile heating, the stability of parallel channels increases with the increase of the system pressure and inlet resistant coefficient. In high inlet subcooling region, cosine heat flux can strengthen the system stability. However, in low inlet subcooling region, the negative effect to system stability will be caused by non-uniform heating. The increase of inlet resistant coefficient will move the turning point of the MSB to high inlet subcooling number.

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Mass Flux and Enthalpy Distribution in a Rod Bundle for Single- and Two-Phase Flow Conditions

Journal of Heat Transfer ◽

10.1115/1.3449786 ◽

1971 ◽

Vol 93 (2) ◽

pp. 197-206 ◽

Cited By ~ 37

Author(s):

R. T. Lahey ◽

B. S. Shiralkar ◽

D. W. Radcliffe

Keyword(s):

Mass Flux ◽

Operating Conditions ◽

Boiling Water ◽

Flow Diversion ◽

Phase Flow ◽

Flow Conditions ◽

Two Phase ◽

Water Reactor ◽

Rod Bundle ◽

Natural Flow

Diabatic multirod subchannel data have been obtained in a 9-rod bundle for operating conditions typical of a boiling water reactor. These data have been used to obtain both the natural flow and enthalpy distribution in a rod bundle and information on the flow diversion enthalpy and the effective flow diversion length.

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