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[en] Accurate measurement of the reactivity worth of safety rods is very important for the safe reactor operation, in normal and emergency conditions. In this paper, the reactivity worth of safety rods in Heavy Water Zero Power Reactor (HWZPR) in the new lattice pitch is measured by advanced source jerk method. The average of the results related to two different detectors is equal to 29.88 mk. In order to verify the result, this parameter was compared to the previously measured value by subcritical to critical approach. Different experiment results are finally compared with corresponding calculated result. Difference between the average experimental and calculated results is equal to2.2%
[en] The neutron decay constant, α, and effective delayed neutron fraction, β_e_f_f, 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, β_e_f_f 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 β_e_f_f value of 7.58e-3 was obtained for the reactor under study. Thus, the relative difference between the β_e_f_f values determined experimentally and by Monte Carlo methods was estimated to be < 4%
[en] A new method, based on reactor prompt gamma radiation detection, for reactor power measurement is introduced and validated. To verify, the ex-core gamma radiation spectrum from the Iranian Heavy Water Zero Power Reactor (HWZPR) were measured by HPGe and NaI detectors each suitably positioned. The collective prompt gamma count rates for all or for a portion of each of 2″×2″ NaI detector spectra were obtained for seven power level readings from calibrated reactor power monitors. A good linear behavior was found between gamma count rate and reactor power. The method of calibrated prompt gamma reactor power determination is a stable and reliable tool, on-line, sensitive to sudden variation of power, working in pulse mode, increasing redundancy and diversity and so improving the reactor safety. The prompt gamma counting system can be adopted and installed in other nuclear reactors to measure power. - Highlights: • In this paper introduces and validates a new application of neutron capture prompt gamma radiation. • This application of prompt gamma radiation represents a reactor power measurement. • The power measurement has been validated by prompt gamma rays from a HWZPR reactor. • This technique for power measurement can complement and increase redundancy for existing reactor power measurement. • This technique is on-line, prompt
[en] In design of a nuclear reactor core, in view of neutronic calculations, some parameters play vital roles in final decision making. The important parameters are: 1-effective multiplication reactor Keff, 2-control rode reactivity worth, 3-change of fuel composition as a result of fuel burn up, 4-time dependent effective macroscopic cross sections such as 5- spectrum dependent reactivity, and 6- temperature dependent coefficients of reactivity, αf, αm, αd, αv, 7-stability function of reactor in feedback effect. In most cases for final decision making, preliminary calculations are done using advanced code and up-to-date data library. In order to be certain of outcome, one has t o compare the results with the experimental or benchmark values. In this project we have tried to calculate some of the core parameters using internationally well known codes(WIMS and CITATION) and compare the results with the measured parameters. The comparison showed very good agreement between calculated and measured parameters such as Keff within experimental error for a heavy water moderated natural uranium reactor
[en] Highlights: • The photoneutron coefficient in HWZPR is an important parameter in safety consideration. • The decay curve of the neutron intensity in the HWZPR was obtained after shutdown. • Using the theory of point kinetics, the effective photoneutron coefficient was measured. • The photoneutron coefficient was calculated with MCNPX code. • The results of the experiment, is compared with MCNPX calculation result. - Abstract: In Heavy Water Zero Power Reactor (HWZPR), the photoneutron coefficient is a parameter of special significance for reactor safe operation and accurate measurement of the reactor power ascending period. Although, in the stable power operation, the fission delayed neutrons and the delayed photoneutrons are only the small fractions of the total neutrons in the reactor, but the certain time after the reactor shutdown they become the main neutron source. In order to measuring the effective photoneutron coefficient, the decay curve of the neutron intensity in the HWZPR was obtained as a function of time after shutdown. The experiment was repeated in the different reactor powers, lower than 40 W. The reactor was in the stable power for 40 min, before shutdown. By analyzing the decay curve into a sum of decreasing exponentials and using the theory of point kinetics, the effective photoneutron coefficient was measured. The delayed neutron and photoneutron counts were corrected to infinite irradiation time. According to the experimental results, the effective delay photoneutron coefficient is equal to 0.31. In continue, this parameter was calculated by MCNPX code. The comparison of the experimental and calculated results show that the relative difference between them is less than 4% and the MCNPX calculated results is verified.
[en] In this report application of the MCNP4B transport code in simulation of Heavy Water Zero Power Reactor (HWZPR) experiment in Nuclear Engineering Department of the Esfahan Research and Fuel Production Center (ERFPC) is verified. It should be noted that because MCNP4B code be able simulated HWZPR physically and geometrically and the lack of benchmark experiment data, this reactor is a suitable case to be simulated by MCNP4B. The continuous energy cross section data from ENDF/B-VI libraries and (α,β) thermal scattering treatment were used in calculations. The goal of the calculations were to determine the following parameters:The effective multiplication factor (Keff); Radial and axial flux distribution in core; Distribution of radial and axial cadmium ratio; This parameters is compared with experimental data and consistency and accuracy of the MCNP4B simulation HWZPR experiments established
[en] Highlights: • An embedded measuring system with enhanced operational capabilities is introduced to the scientists. • The design is low cost and reprogrammable. • The system design is dedicated to multi-detector experiments with huge data collection. • Non count loss effect Feynman-α experiment is performed in EHWZPR. • The results is compared with endogenous/inherent pulsed neutron source experiment. - Abstract: In this work, an embedded multi-input multi-million-channel MCS in a newly design is constructed for multi-detector experimental research applications. Important characteristics of the system are possible to be tuned based on experimental case studies utilizing the reprogrammable nature of the silicon. By means of differentiation of the integrated counts registered in memory, this system is featured as a zero channel advance time measuring tool ideal for experiments on time correlated random processes. Using this equipment, Feynman-α experiment is performed in Esfahan Heavy Water Zero Power Reactor (EHWZPR) utilizing three different in-core neutron detectors. One million channel data is collected by the system in 5 ms gate time from each neutron detector simultaneously. As heavy water moderated reactors are significantly slow systems, a huge number of data channels is required to be collected. Then, by making in use of bunching method, the data is analyzed and prompt neutron decay constant of the system is estimated for each neutron detector positioned in the core. The results are compared with the information provided by endogenous pulsed neutron source experiment and a good agreement is seen within the statistical uncertainties of the results. This equipment makes further research in depth possible in a range of stochastic experiments in nuclear physics such as cross correlation analysis of multi-detector experiments.
[en] Highlights: • In this paper we developed some parameters for the HWZPR core using MCNP4c code. • The benchmark calculations were performed to estimate Keff, ν, and Q. • The physics of HWZPR calculations was presented. • HWZPR uses natural metallic uranium as the fuel. • HWZPR uses heavy water as the moderator, and graphite as the reflector. - Abstract: The MCNP4c code, based on the probabilistic approach, is applied in modeling the 3D configuration of the Heavy Water Zero Power Reactors (HWZPRs) core. All of the constituents of the core such as fuel pellets, fuel elements, moderator (D2O) and annular graphite reflector are simulated using the MCNP4c code. The benchmark calculations are made to estimate various parameters including effective multiplication factor (Keff), number of neutron production per fission (ν), and energy release in the fuel per fission (Q). The (n,Xn) reaction with changes in water level are investigated. In order to validate the MCNP4c calculations, the obtained critical water level is compared to that of the experimental data. Good consistency is observed between calculated and experimental data
[en] Highlights: ► A new approach for reactor power measurement is proposed. ► The proposed technique has been applied for gamma and neutron radiation from HWZPR reactor. ► NE213 detector has been used for reactor power measurement. ► The proposed technique has increased the redundancy and diversity for reactor power measurement. ► This proposed technique is on-line, prompt, and independent of safety and control rods and fuel configuration. - Abstract: Both gamma rays and neutrons are produced and distributed in different nuclear reactions within the Heavy Water Zero Power Reactor (HWZPR) core. The intensities of distributed gamma rays and neutrons from the reactor core are proportional to the reactor power. The NE213 organic scintillation detector can detect both gamma and neutron simultaneously. In this article, a new method has been used for calibration of the reactor power by measurement of gamma rays and neutrons with the 2″ × 2″ dimensions NE213 detector and suitable nuclear electronic equipments outside of core. The reactor calibrated power by this technique is on-line, prompt, and independent of safety and control rods and fuel configuration of the reactor with a good efficiency. The detector, when used 7–10 m from the core center, has necessary efficiency for full-power range measurement (100 W) and in case of accident occurring and sudden increase of the power up to 170 W
[en] Research highlights: → In this study all of the constituents of the core were modeled using MCNP4c code. → In this study calculations of axial and radial neutron fluxes were performed in three energy groups. → In this study the cadmium ratio was calculated as well and the neutron flux parameters were computed using cadmium ratio. → This study showed that the MCNP4c model of the HWZPR was validated. - Abstract: The MCNP4c code, based on the probabilistic approach, was used to simulate 3D configuration of the core of the heavy water zero power reactor (HWZPR). In present work, first, all of the constituents of the core such as fuel pellets, fuel element, moderator (D2O) and annular graphite reflector were modeled using MCNP4c code. Then calculations of axial and radial neutron fluxes were performed in three energy groups such as thermal (0-0.625 eV), epithermal (0.625-550 eV), and fast (0.550-20 MeV). The cadmium ratio was calculated as well and the neutron flux parameters such as extrapolated height (He), extrapolated radius (Re) and physical center of the core (z0) were computed using cadmium ratio. Comparison of the neutron flux parameters with the experimental data showed that the MCNP4c model of the HWZPR was validated.