Self-powered Neutron Detectors Research Articles

Comparison of Rhodium, Vanadium, Cobalt, Inconel & Silver Emitter Self-Powered Neutron Detectors: Literature Review Article

Self-Powered Neutron Detectors (SPNDs) are in use as in-core Neutron Fluence Detectors in Nuclear Power Plants. Though the detectors are simple in design and have a common structure for the same application, there are various types of emitters (neutron-sensitive electrodes) that make SPNDs categorized into different types. There are various SPNDs in application at different types of nuclear power reactors. SPND emitters are chosen based on their characteristics/behavior in the neutron & gamma flux environment in the reactor core. A detailed Literature Review was done on five different types of SPNDs. This paper focuses on the physics behind the operation, characteristics, and review of Vanadium, Rhodium, Inconel, and Cobalt & Silver emitter-based SPNDs. A comparison study was done by a literature review on these detectors.

A fast numerical method for calculating SPND space charge effect at steady state

To address the issue of low efficiency and long computation times in calculating the space charge effect in Self-Powered Neutron Detectors (SPNDs), we developed a fast and efficient numerical method to calculate the steady-state electric fields in SPND insulators. Previous calculations have shown that even when the electric field in the SPND insulator reaches 1 GV/m, its effect on electron transport is negligible. Therefore, we assume that the electric field has a negligible effect on electron transport. Based on this assumption, we developed a one-step numerical method for calculating the steady-state electric field in the insulator. This fast method is based on the charge conservation equation in equilibrium, thus requiring only a single charge deposition result without an electric field to obtain the distribution of the electric field under steady-state conditions. We validated our method by comparing it with precise iterative calculation results and experiments. The computational results indicate that, for three typical experimental scenarios, the fast method only takes up to one percent, or even less, of the time required by the iterative method. At the same time, the Mean Relative Error (MRE) in the electric field distribution between the fast method and iterative calculations are 1.48%, 0.31%, and 5.12%, respectively; whereas the relative errors in sensitivity calculations based on the electric field compared to iterative calculations are all less than 2%. Therefore, the fast method can significantly reduce computation time and ensure sufficient accuracy of steady state electric field distribution when the electric field is less than 1 GV/m. The introduction of this method has made it possible to conduct space charge effect assessments and precise sensitivity calculations for the placement of detectors throughout the entire reactor core.

Continuous mapping of nuclear reactor core power using artificial neural network even in the presence of inactive detectors

Monitoring the radial power distribution during the operation of a pressurized light water reactor (PWR) is crucial for ensuring safe operating conditions and achieving high levels of fuel burnup. This paper introduces a methodology utilizing Artificial Neural Networks (ANN) for reconstructing the radial power distribution in the core of a Pressurized Water Reactor (PWR) with a hot full power of 1876 MWth, such as the Angra 1 reactor. This approach uses measurements from Self-Powered Neutron Detectors (SPND), simulated through the SERPENT code. The use of ANN demonstrated good accuracy in predicting the radial power distribution with an average relative error of 1.27%, considering 36 active detectors, with maximum relative error of 6.99%. Moreover, the proposed process demonstrated robust performance, even when measurements from one, two, or three SPND detectors were unavailable, resulting in errors of 1.24%, 1.13 %, and 1.09%, respectively. Therefore, the methodology ensures a reliable reconstruction of the radial power distribution, even when SPND detector measurements are unavailable, enabling the optimization of detector use and contributing to the increase of operational safety margins.

The signal compensation method for the neutron flux in the measurement system using self-powered neutron detector.

Self-powered neutron detectors (SPNDs) have been utilized within in-core instrumentation to measure neutron flux for control and core flux mapping in nuclear reactors. To estimate neutron flux with SPNDs, a mathematical dynamic model correlating neutron flux and SPND material has been established. Estimation and signal compensation for neutron flux have primarily been developed using transfer-function-based methods or state-space-based methods. Particularly for the rhodium SPND, to compensate for its delayed response to incident neutron flux input, both groups of compensation methods have been widely applied. This Review details the signal compensation methods of neutron flux using transfer-function-based methods, such as those employing analog circuits, dynamic modeling of neutron flux, compensation of neutron flux, and direct inversion. In addition, signal compensation and estimation of neutron flux using state-space-based methods, such as the Kalman filter and H-infinity filter, are reviewed, along with basic calculations based on certain assumptions. Since there are differences in the characteristics of the two groups of methods for the same type of SPND, review comments are also included regarding the stability of compensation methods, based on results obtained from calculations using certain assumptions.

Study on structural and material dependence of Rhodium Self-powered Neutron Detector performance

The neutron measurement properties of Rh-SPNDs are greatly affected by their geometric constructions, which needs to be optimized while designing. This effect is reflected in the sensitivities for gamma and neutron detection. However, the influence on gamma sensitivity has not been fully analyzed before, which is of the same importance as neutron sensitivity. Therefore, it is necessary to quantitatively analyze the relationship between detector sensitivity and geometric dimensions. The effect of Rh-SPND structural and material parameters on neutron and gamma sensitivities has been calculated and analyzed through numerical simulations. The research results show that detector sensitivities are strongly depending on the detector size and its emitter shape. Moreover, the detector response to exogenous reactor gamma can be eliminated by optimizing the detector collector size.

A simulation study of the ability to detect power distribution perturbations in the texas A&M TRIGA reactor with self-powered neutron detectors

Given the variety of ways that nuclear reactor core power may be perturbed, reactor operators and developers are keen on understanding the accuracy and convergence time during which perturbations in reactor power distribution may be synthesized (i.e., inferred) from an array of in-core radiation detectors. A simulation study was conducted as described herein using a highly detailed model of the Texas A&M Training, Research, Isotopes, General Atomics Reactor, in which an array of self-powered neutron detectors (SPNDs) was considered for input to the power synthesis methodology. The core power synthesis is conducted using a point-based iterative method with an iterative loop built in to ensure working equation consistency. The forward problem of SPND response to simulated perturbations in reactor power was solved for Gaussian peak-type perturbations in the reactor power distribution. These perturbations varied in variance, amplitude, and core location to assess their impact on synthesis error and to determine the number of iterations required for convergence. A relation between the unique resolvability limit and perturbation width was identified such that the maximum synthesis error increased rapidly when the peak width went beneath this limit (a width approximating half the reactor’s fuel pin-to-pin pitch); this resolvability limit is specific to the SPND configuration and fuel segmentation considered herein. The synthesis error increased linearly with perturbation peak amplitude, whereas the convergence time increased nonlinearly. Perturbations located closer to the center of the core were synthesized more accurately, albeit with a higher number of required iterations. These findings provide a qualitative and quantitative understanding of the accuracy and speed at which different types of spatial power perturbations can be resolved in light-water reactors.

Applicability to DEMO breeding blankets of neutron measurements techniques from fission reactors

Neutron measurements are routinely performed in fission reactors. A lot of experience has been gained at CEA in designing, prototyping and testing neutron sensors and associated acquisition systems in several nuclear facilities with a wide range of demanding conditions. In this paper, the applicability of this experience to neutron diagnostics in the breeding blankets of DEMO is addressed, as a complement to the already planned diagnostic strategy.The breeding blankets are a key component of a fusion reactor such as DEMO. The expected performances and operational constraints are demanding, nevertheless some of those, as the neutron flux range and high temperature, are close to what is encountered in sodium-cooled fast neutron reactors.The strengths and drawbacks of neutron sensors are presented with respect to the performances and constraints. Self-powered neutron detectors and fission chambers benefit from a vast return of experiment in fission reactors and received recent developments in the framework of studies for sodium-cooled fast neutron reactors. The innovative optical fission chamber is discussed for its electromagnetic immunity and high dynamic range demonstrated up to seven decades. Dosimetry with activation foils is also considered for its ability to provide an absolute calibration and spectral unfolding.

An Improved Numerical Model for Quantitatively Computing the Space Charge Effect of Self-Powered Neutron Detector

An Improved Numerical Model for Quantitatively Computing the Space Charge Effect of Self-Powered Neutron Detector

USING SELF-POWERED NEUTRON DETECTORS TO MONITOR NEUTRON-MULTIPLYING CHARACTERISTICS OF THE WATER-WATER POWER REACTOR CORE

A method is described for diagnosing the water-water power reactor core components using self-powered neutron detector (SPND) readings. Self-powered neutron detectors are part of the incore instrumentation system. The method monitors both the detector itself and fuel element. The paper’s authors suggest using both steady state and dynamic reactor core conditions for interpretation of SPND readings. Dynamic conditions can be used to determine the coefficients of neutron flux dynamics that are calculated by analogy with determination of reactivity values from output signals of ion chambers in the reactor control and protection system.

Simulation study of a rhodium self-powered neutron detector for irradiation of nuclear fuel and material reactor

To accurately judge the irradiation test cycle of nuclear fuel and material in-pile irradiation, and provide precise design inputs for the post-irradiation performance evaluation of fuel and material, the NIT-Rh self-powered neutron detector has been designed and developed. The sensitivity characteristics of the detector have been simulated and verified. This study introduces the basic structure and working principle of the rhodium self-powered neutron detector for irradiation of nuclear fuel and materials in the reactor. Additionally, a new computational model has been constructed by the Monte Carlo method, and the current sensitivity of different sizes of emitters and insulators has been analyzed. The model considers a more realistic neutron source and β-electron energy spectrum, accounts for the space charge effect on the signal in the insulator, and compares the simulated sensitivity with the reactor test sensitivity. The results show that the new rhodium self-powered neutron detector calculation model is more accurate, and the relative deviation between the simulated and reactor test sensitivities is only 3.06 %. It can be used for the in-heap irradiation test and provides a method for the application of the irradiation of nuclear fuel and material reactors.

Fault Identification Method for In-Core Self-Powered Neutron Detectors Combing Graph Convolutional Network and Stacking Ensemble Learning

Fault Identification Method for In-Core Self-Powered Neutron Detectors Combing Graph Convolutional Network and Stacking Ensemble Learning

A Monte Carlo method for quantitatively calculating the neutron sensitivity of rhodium self-powered neutron detectors in reactors

A Monte Carlo method for quantitatively calculating the neutron sensitivity of rhodium self-powered neutron detectors in reactors

Study of neutron sensitivity for vanadium self-powered neutron detector in nuclear reactors

Vanadium self-powered neutron detectors (SPNDs) are widely used as in-core unmovable detectors in nuclear power plants to continuously carry out data monitoring of neutron flux and nuclear power. In this study, a theoretical calculation model is presented for determining the signal current and thermal neutron sensitivity of vanadium SPNDs. First, the physical characteristics and reaction mechanisms in vanadium SPNDs irradiated with neutrons were discussed thoroughly. Then, a computational approach to determine the neutron sensitivity of the vanadium SPND based on a Monte Carlo method without assumptions and approximations was introduced. Finally, in order to verify the performance of the vanadium SPND and our methodology, the calculated values were compared with experimental measurements and the previous literature. It can be found that all the results agree well with the experimental measurements and that the maximum differences do not exceed 3%, which demonstrates the reliability and effectiveness of the method and further improves the calculation accuracy.

Monte Carlo analyses and experimental investigation of the vanadium self-powered neutron detector in 60Co source and research pulsed reactor

As the online monitoring apparatus in the reactor, self-powered neutron detectors (SPNDs) have a great potential for development in nuclear energy. To further characterize the SPND response in the actual radiation field, some irradiation experiments and Monte Carlo analyses based on the 60Co gamma-rays source and a research pulsed reactor were performed. During the experiments, the current signals were measured with various reactor irradiation facilities. A series of experimental phenomena, such as the negative current effect of the gamma rays, shutdown attenuation current, and the difference in detector sensitivity, are described and theoretically explained by using a numerical model GEANT4-SPND, an in-house Monte Carlo toolkit for SPND simulation based on Geant4. The numerical model proves to be highly effective in restoring the experimental results for the detector response current, the signal prompt proportion, and the current trend. This work has not only validated the existing calculation method but also provided reference radiation field parameters and detector experimental data for the future development and verification of sensor models. Besides, the analyses results have provided some insights into the study of the mechanism and optimization of detector design.

Analysis of signal cable noise currents in nuclear reactors under high neutron flux irradiation

Cables are indispensable in nuclear power plants for transmitting data measured by various types of detectors, such as self-powered neutron detectors (SPNDs). These cables will generate disturbing signals that must be accurately distinguished and eliminated. Given that the cable current is not very significant, previous research has focused on SPND, with little attention paid to cable evaluation and validation. This paper specifically focuses on the quantitative analysis of cables and proposes a theoretical model to predict cable noise. In this model, the reaction characteristics between irradiated neutrons and cables were discussed thoroughly. Based on the Monte Carlo method, a comprehensive simulation approach of neutron sensitivity was introduced and long-term irradiation experiments in a heavy water reactor (HWR) were designed to verify this model. The theoretical results of this method agree quite well with the experimental measurements, proving that the model is reliable and exhibits excellent accuracy. The experimental data also show that the cable current accounts for approximately 0.2% of the total current at the initial moment, but as the detector gradually depletes, it will contribute more than 2%, making it a non-negligible proportion of the total signal current.

Development of a complete simulation package for Self-Powered Neutron Detectors using the Monte Carlo Method and Geant4 toolkit

In order to provide guidance on the design and use of the Self-Powered Neutron Detector (SPND) and improve measurement accuracy, accurate simulation of SPND is required. Therefore, a complete SPND simulation package was developed, including a particle transport calculation module, an electric field calculation module, a visualization interface and a data post-processing module. Due to electric field produced by space charge in the insulator, Geant4 has been chosen as the particle transport calculation module and an iterative code for the electric field was written to implement the calculation of the electric field in the insulator. To help researchers simplify the process of writing codes, a wizard-like visual interface was developed based on QT for configuring the input files and for performing the calculations. The accuracy of the simulation package was verified by comparing it with other calculation codes. With the help of the simulation package, the user can very easily achieve an accurate simulation of the SPND.

Simulation and Analysis of the Space Charge Effect in a Self-Powered Neutron Detector

Simulation and Analysis of the Space Charge Effect in a Self-Powered Neutron Detector

Twin model-based fault detection and tolerance approach for in-core self-powered neutron detectors

Twin model-based fault detection and tolerance approach for in-core self-powered neutron detectors

A general method for delay compensation of self-powered neutron detectors in reactors

Self-Powered Neutron Detectors (SPNDs) have long been widely used as reactor in-core neutron detectors. However, delayed type SPNDs, a typical type SPND with delayed current component, can not be directly used for real-time neutron flux monitoring. To solve this problem, several researchers have established compensation methods to reconstruct neutron flux. For the various SPNDs with delayed currents, the existing compensation methods are usually case-dependent. Therefore, a general compensation method for delayed type SPNDs with high portability is proposed in this paper. Based on linear equations in the s domain, this method is applicable for all the delayed SPNDs, giving the general compensation solution with definite iterations. Moreover, this compensation method is tested by two typical delayed SPNDs, indicating its high portability and applicability.

Валідація MCNP-моделі формування струму фонової жили детектора прямого заряду у ВВЕР-1000

The article presents the results of the numerical simulation of the signal formation process of the background wires of self-powered neutron detectors (SPND) under the action of gamma radiation in the VVER-1000 core using MCNP code. The validation of the MCNP model was carried out on the results of experimental determination of the current of the background wires of the SPND, obtained at three different power units with VVER-1000 during the fuel campaign. The article also proposes a new gamma-ray method for determining the thermal power of the VVER-1000 reactor (TPR) based on the signals from the background wires of the SPND. TPR is an important safety parameter of VVER-1000, therefore, increasing the accuracy of determining TPR with the introduction of an additional gamma method for its determination is an urgent task, given the plans to increase the TPR of VVER-1000. The results of the experimental determination of the VVER-1000 TPR by the traditional neutron method based on the SPND signals are presented, and problematic issues regarding the error in determining the TPR by the neutron method are pointed out. The article presents the results of modeling to study the influence of the main factors affecting the change in the proportionality coefficient Kgm between the actual TPR and the TPR determined by the gamma method. To improve the accuracy of determining the TPR by the gamma method, a correction model for Kgm is proposed, which takes into account the effect of nuclear fuel burnup on the change in the signal of the background wires of the SPND. Taking into account that the signal of the background wires of the SPND is inertialess with respect to the change in the neutron power of the reactor, the introduction of the method for determining the TPR by the gamma method is promising for the implementation of an additional alternative channel for generating an emergency protection signal in terms of both power and the period of the reactor.