An investigation into the origin of the interference generated during the measurement of the reactivity in a high burn-up reactor core

After a general review for the technical development before 1980's in the area of nuclear reactor noise analysis, a reactor dynamic parameter, α_c=(144.57±2.09) s^-1, obtained through off-line background processing, is shown. The processed data is measured through double- detector cross correlation frequency spectral analysis (CCFS) for the experimental nuclear power reactor at the burn-up end in sept. 1980. This paper also presents the abnormal situations for data acquisition, the off-line data processing method, the background spectra selection for data processing and the program for the least-squares fit calculation. Here also explains how neutron background is generated and how its strength is calculated. This verifies the fact that after a long-term burn-up run, large γ field must be suppressed and also more attention must be paid to the uncorrelated neutron noise from the fuel burn-up. (authors)