Investigating Dynamic Parameters in HWZPR Based on the Experimental and Calculated Results

The neutron decay constant, α, and effective delayed neutron fraction, βeff, are important parameters for the control of the dynamic behavior of nuclear reactors. For the heavy water zero power reactor (HWZPR), this document describes the measurements of the neutron decay constant by noise analysis methods, including variance to mean (VTM) ratio and endogenous pulse source (EPS) methods. The measured α is successively used to determine the experimental value of the effective delayed neutron fraction as well. According to the experimental results, βeff of the HWZPR reactor under study is equal to 7.84e-3. This value is finally used to validate the calculation of the effective delayed neutron fraction by the Monte Carlo methods that are discussed in the document. Using the Monte Carlo N-Particle (MCNP)-4C code, a βeff value of 7.58e-3 was obtained for the reactor under study. Thus, the relative difference between the βeff values determined experimentally and by Monte Carlo methods was estimated to be < 4%.