A comparison of void-fraction measurements during flashing-induced instabilities obtained with a wire-mesh sensor and a gamma-transmission set-up


A comparison of void-fraction measurements during flashing-induced instabilities obtained with a wire-mesh sensor and a gamma-transmission set-up

Manera, A.; Prasser, H.-M.; van der Hagen, T. H. J. J.; Mudde, R. F.; de Kruijf, W. J. M.

The void fraction produced in an adiabatic section (riser) during flashing-induced instabilities in a natural-circulation steam/water loop is measured by means of a wire-mesh sensor and two gamma-transmission set-ups located just above and below the wire-mesh sensor respectively. In this paper a comparison between the two different measuring techniques is given. The wire-mesh sensor is capable of measuring the time-dependent two-dimensional void-fraction distribution on a grid of 16x16 points equally distributed over a cross section of the riser, while the gamma-transmission set-ups measure the chordal void fraction along a collimated beam through the riser at a certain height.
The high sampling rate of the wire-mesh sensor (up to 1200 Hz) allows to detect both the frequencies characteristic of the flashing process (between 2 and 4 Hz) and the frequencies characteristic of the flashing-induced flow oscillation (below 0.05 Hz). The former frequencies are less visible in the spectrum of the gamma-transmission signal due to the lower signal-to-noise ratio.
The effect of the wire-mesh sensor on the triggering of void production due to the provision of extra nucleation sites is also studied; no significant differences are observed in the main parameters of the instability if the wire-mesh sensor is removed from the experimental loop.

Keywords: boiling water reactor stability; two-phase flow; wire-mesh sensors; gamma densitometers; void fraction measurement

  • Lecture (Conference)
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 436.
  • Contribution to proceedings
    4th International Conference on Multiphase Flow, New Orleans, Lousiana, USA - May 27 to June 1, 2001. Proc. CD-ROM, paper 436.

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Publ.-Id: 3851