Advances in time-dependent Monte Carlo simulations for void velocity determination using neutron noise techniques. (August 2021)

• Record Type: Journal Article
• Authors: Yamamoto, Toshihiro; Shen, Xiuzhong; Sakamoto, Hiroki
• Is Part Of: Progress in nuclear energy. Volume 138(2021)
• Publication Date: 2021-08
• Subjects: Void velocity -- Neutron noise -- Monte Carlo -- Simulation; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 333.7924
• DOI: 10.1016/j.pnucene.2021.103840
• Languages: English
• ISSNs: 0149-1970

Abstract

Abstract: Neutron noise measurements for estimating void velocity in a void-containing water flow where spherical bubbles move upward are simulated using a continuous energy Monte Carlo method. The method is newly equipped with a function for handling time-varying locations of void bubbles. In the simulations, time-series data of neutron counts in axially-placed detectors are obtained. The data are subsequently processed to yield the cross-correlation function (CCF), cross-power spectral density (CPSD), and auto power spectral density (APSD). The void velocities are estimated from the maximum CCF, slope of the phase of the CPSD as a function of frequency, and dip frequency of the APSD. These three methods yield a constant void velocity estimation. The simulations demonstrate that the noise techniques are insensitive to a void flow that contains smaller bubbles. Highlights: Neutron noise measurements in a void-containing water are simulated using Monte Carlo method. Time-series data of neutron counts in axially-placed detectors are obtained. The void velocities are accurately estimated from CCF, CPSD, and APSD.