A new dynamic rod worth measurement method based on the transient spatial factor.

• A new dynamic rod worth measurement method based on the transient spatial factor has been proposed. • A transient spatial factor is proposed to consider the transient spatial effect caused by the change in the shape distribution of neutron flux. • A new dynamic rod worth measurement method based on the transient spatial factor is applied to a commercial CNP1000 reactor employing the measurement data. • A comparison is made between the control rod worth measured by the transient spatial factor and that measured by the static spatial factor and dynamic spatial factor. Given the responsibility of the control rod for controlling reactivity in commercial PWRs, accurate measurement of it is of great significance. To measure the control rod worth in the zero-power physics test, this paper proposes a new dynamic rod worth measurement method by using the definition of the transient spatial factor. During the process of dynamic rod worth measurement, it was found that the rapid movement of the control rod in the timescale of seconds causes a substantial change in the shape of neutron flux in the 3D space, which significantly affects the power-range detector signals, resulting in an incorrect estimation of reactivity by the reactimeter. To eliminate the transient spatial effect of neutron flux, a transient spatial factor is proposed, which is provided by calculating the process of control rod insertion based on the 3D time-dependent neutron diffusion calculation. Thus, a new DRWM method based on the transient spatial factor has been applied and validated in a CNP1000 reactor. Results of the control rod worth are presented in this paper to demonstrate its performance in engineering applications. [ABSTRACT FROM AUTHOR]