### Abstract

The value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. The absolute magnitude of the MTC is obtained from noise analysis by using the root-mean-square method and the frequency response function technique. Both approaches are used in conjunction with the phase angle method, which determines the MTC sign, to obtain complete information about the MTC. Analytical expressions that are derived show that a limitation exists on the range of MTC values for which the cross-power spectral density phase angle can be used to establish the MTC sign. This research shows that small positive values of the MTC (an unstable condition) can result in a -180-deg phase angle shift, contrary to earlier studies that indicated a stable reactor. The range of sign determinate MTC values is dependent on the driving noise source. Simulated noise data are generated for different MTC values and analyzed to verify the theoretical work. A comparison of the indeterminate regions to allowable MTC values for an operating pressurized water reactor is also presented.

Original language | English (US) |
---|---|

Pages (from-to) | 203-211 |

Number of pages | 9 |

Journal | Nuclear Science and Engineering |

Volume | 119 |

Issue number | 3 |

State | Published - Mar 1995 |

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### ASJC Scopus subject areas

- Nuclear Energy and Engineering

### Cite this

*Nuclear Science and Engineering*,

*119*(3), 203-211.

**Valid ranges for using the cross-power spectral density phase angle for moderator temperature coefficient sign determination.** / Holbert, Keith; Venkatesh, Nikhil.

Research output: Contribution to journal › Article

*Nuclear Science and Engineering*, vol. 119, no. 3, pp. 203-211.

}

TY - JOUR

T1 - Valid ranges for using the cross-power spectral density phase angle for moderator temperature coefficient sign determination

AU - Holbert, Keith

AU - Venkatesh, Nikhil

PY - 1995/3

Y1 - 1995/3

N2 - The value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. The absolute magnitude of the MTC is obtained from noise analysis by using the root-mean-square method and the frequency response function technique. Both approaches are used in conjunction with the phase angle method, which determines the MTC sign, to obtain complete information about the MTC. Analytical expressions that are derived show that a limitation exists on the range of MTC values for which the cross-power spectral density phase angle can be used to establish the MTC sign. This research shows that small positive values of the MTC (an unstable condition) can result in a -180-deg phase angle shift, contrary to earlier studies that indicated a stable reactor. The range of sign determinate MTC values is dependent on the driving noise source. Simulated noise data are generated for different MTC values and analyzed to verify the theoretical work. A comparison of the indeterminate regions to allowable MTC values for an operating pressurized water reactor is also presented.

AB - The value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. The absolute magnitude of the MTC is obtained from noise analysis by using the root-mean-square method and the frequency response function technique. Both approaches are used in conjunction with the phase angle method, which determines the MTC sign, to obtain complete information about the MTC. Analytical expressions that are derived show that a limitation exists on the range of MTC values for which the cross-power spectral density phase angle can be used to establish the MTC sign. This research shows that small positive values of the MTC (an unstable condition) can result in a -180-deg phase angle shift, contrary to earlier studies that indicated a stable reactor. The range of sign determinate MTC values is dependent on the driving noise source. Simulated noise data are generated for different MTC values and analyzed to verify the theoretical work. A comparison of the indeterminate regions to allowable MTC values for an operating pressurized water reactor is also presented.

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M3 - Article

VL - 119

SP - 203

EP - 211

JO - Nuclear Science and Engineering

JF - Nuclear Science and Engineering

SN - 0029-5639

IS - 3

ER -