Reactivity estimation using digital nonlinear H estimator for VHTRC experiment

Suzuki, Katsuo; Nabeshima, Kunihiko  ; Yamane, Tsuyoshi; Fujii, Yoshio*

On-line and real-time estimation of time-varying reactivity in a nuclear reactor is necessary for early detection of reactivity anomaly and safe operation. Using a digital nonlinear H estimator, an experiment of real-time dynamic reactivity estimation was carried out in the VHTRC of JAERI. Some technical issues of the experiment are described, such as reactivity insertion, data sampling frequency, anti-aliasing filter, experimental circuit and digitalizing nonlinear H reactivity estimator, and so on. Then, we discussed the experimental results obtained by the digital nonlinear H estimator with sampled data of the nuclear instrumentation signal for the power responses under various reactivity insertions. Good performances of estimated reactivity were observed, with almost no delay to the true reactivity and sufficient accuracy between 0.05cent and 0.1cent. From the results of the experiment, it is concluded that the digital nonlinear H reactivity estimator can be applied as on-line real-time reactivity meter for actual nuclear plants.