Reactive Control Capability Research Articles

Comparison of BANDI-60 core designs using Pyrex burnable absorber and annular fuel embedding gadolinia wire

The BANDI-60 Soluble Boron-Free Small Modular Reactor (SMR) developed by KEPCO E&C is a Pressurized Water Reactor producing 200 MW of thermal power. This study proposes core designs for the BANDI-60 using two types of burnable absorbers (BAs) and compares their characteristics. One core uses the discrete Pyrex BA, and the other uses a new BA design named “cylindrically inserted and mechanically separated burnable absorber” (CIMBA). Pyrex is the borosilicate glass consisting of B2O3-SiO2, which suppresses excess reactivity to achieve a long cycle length. CIMBA is a wire-type gadolinia (Gd2O3) BA inserted into annular fuel pellets, which utilizes a spatial self-shielding effect on the fuel material and has a greater fuel inventory than discrete BAs. The core designs are performed using a McCARD code, and the results showed both cores can operate over an approximate cycle length of 4.9 years and possess a reactivity control capability ensuring a safe shutdown.

A method to control distributed energy resources in distribution networks using smart meter data

Voltage regulation has been one of the major challenges for distribution network operators (DNOs) due to the integration of distributed energy resources in the recent years. Control approaches mitigating over-voltage (OV) generally require full network model, which for low-voltage distribution networks (LVDNs), can be inaccessible to DNOs. This paper presents a novel data-driven model-free control framework for improving voltage regulation in 4-wire 3-phase LVDNs. In the proposed approach, first, using smart meter data, the aggregated resistance and reactance matrices of the network are estimated. Then, these matrices serve as an input for the proposed optimal power flow (OPF) method to control the DERs’ active and reactive power outputs. This method also lets the DNO adjust the fairness in prosumers’ generation curtailment. The performance of the proposed approach is evaluated in various case studies conducted on a real-world low-voltage test feeder. The simulation results exhibit significant effectiveness in solving the OV problem associated with DERs. For example, in the studied network, the proposed approach limits the maximum voltage of the network to 1.1 pu, while without having control over the DERs output power, it can even overpass 1.17 pu during the peak generation period. In addition, utilizing DERs’ reactive control capability reduces the amount of active power curtailment, and prosumers are able to collectively inject 5.66% more active power.

Active control method of large‐scale wind integrated power system with enhanced reactive power support for wind speed fluctuation

A regional power grid containing high-density wind power is generally connected to a load centre through long-distance transmission lines. Voltage problems, caused by wind speed fluctuation, in the sending-end grid have become increasingly serious. The variable speed wind turbine has been used to compensate the deficit in reactive power. However, the available methods could not meet the requirement because the controllable range of reactive power contributed by wind farms cannot be adjusted. A new idea of reactive power control realised by the active control before wind speed fluctuation was proposed to prevent the voltage variation. Firstly, the influence of wind speed fluctuation on voltage was analysed, and the power controllable range of wind turbines was studied. The principle and strategy of the active control of reactive power were proposed based on the model predictive control theory. Then, the active control model was established according to the system dynamic demand for reactive power. According to wind speed forecasting, the reactive control capability of wind turbine was excavated to meet the grid demand by adjusting active power before wind speed variation, and the reduced active power of wind farms is optimally compensated by thermal powers. Finally, the method was proven to solve voltage problems.

Study on Optimization Design for CSR1000 Core

An optimization design of China supercritical water-cooled reactor (SCWR) with the rated electric power of 1000 MWe (CSR1000) conceptual core is proposed. Steady-state performance of the proposed core is then studied with the SCWR core steady-state analysis code system SNTA. These key parameters such as burnup performance, reactivity control capability, power distribution, maximum fuel cladding temperature, and maximum linear power density are analyzed. The relative coolant flow rate of the second flow path, which is suited with assembly power, is also presented. The study shows that the refueling cycle of CSR1000 core can be extended effectively under the optimization design.

A Bidirectional Battery Charger With Modular Integrated Charge Equalization Circuit

High-voltage battery pack and charger structure are the main concerns of the electric vehicle (EV) developments. To achieve required voltage and power in propulsion systems, cascading battery stacks is essential. However, due to small discrepancies between different cells, charge imbalance occurs. Charge imbalance reduces battery cells life cycle, accessible energy, and system performance. Hence, charge equalization among battery stacks is necessary. Furthermore, EVs should have some essential requirements to provide desired contributions in future networks. Therefore, bidirectional power flow and reactive power control are other important capabilities of the battery charger system. In this paper, a bidirectional structure with two operation modes for a modular battery stack is developed. The developed structure has active and reactive control capabilities during grid to vehicle and vehicle to grid operations. To improve the battery system performance, a modular charge equalizer circuit (CEC) for both operation modes is developed. The modular configuration of the battery stack improves the system reliability and flexibility. Moreover, the overall system performance for the CEC and converter is improved by utilizing the integrated control strategy. Performance of the proposed structure is evaluated using simulations and laboratory experiments. The results confirm the capability of the proposed structure.

A New Boiling Water Reactor Core Concept for a Next-Generation Light Water Reactor

In this paper a boiling water reactor (BWR) core concept that meets various requirements for a next-generation light water reactor is proposed. This BWR core can be operated as either a high-burnup core or a high-conversion core simply by replacing the fuel assemblies and control rods. The high-burnup core is suitable for a once-through nuclear fuel cycle and has a low fuel cycle cost due to the adoption of advanced spectral shift technology. The high-conversion core is suitable for nuclear fuel recycling and reaches a high-conversion ratio by adopting a tight-lattice arrangement of mixed-oxide fuel rods in the fuel assemblies and using control rods with a zirconium follower. The reactor structures are essentially identical, and they are designed to be as simple as the current BWR to achieve high reliability. The reactor core also has high operability due to the spectral shift water rods that are operated with all control rods withdrawn. At reactor shutdown, the core has a large reactivity control capability due to the cruciform control rods with wider blades and has an ample safety margin.

Reactivity Control Capability of Fuel-Salt Processing System in a Molten-Salt Breeder Reactor

Reactivity Control Capability of Fuel-Salt Processing System in a Molten-Salt Breeder Reactor

Reactivity Control Capability of Fuel-Salt Processing System in a Molten-Salt Breeder Reactor

An evaluation is made of the reactivity control capability of the fuel processing system (FPS) in a molten-salt breeder reactor. The principal functions required of the FPS are : (a) Isolation of 233Pa from regions of high neutron flux during its decay to 233U, and (b) the removal of fission products from the system. The FPS can very usefully serve also to control the primary system reactivity by appropriately utilizing its function of extracting uranium and reconstituting the fuel contained in the salt. The principles of operation are quite similar to the chemical shim control system currently installed in PWR's whereby the core reactivity, affected by changes in the moderator temperature, fuel burnup and transient Xe, is adjusted by regulating the concentration of boric acid introducted in the moderator as neutron absorber. The present study examines the capability of the FPS to follow transient Xe as in PWR's, and proves that the FPS should effectively serve as a system for adjusting not only long-term changes in reactivity but also short-term transient variations without any accompanying difficulties foreseen in operation.