Nuclear Refueling Research Articles

Market Power in the New England Electricity Market: Evidence from Nuclear Refueling Outages

Market Power in the New England Electricity Market: Evidence from Nuclear Refueling Outages

Adaptive Neural Network Control of an Uncertain Nuclear Refueling Machine With Input Backlash and Asymmetric Output Constraint

This paper studies the control problem of an uncertain nuclear refueling machine (RM) system in the presence of uncertainty, external disturbance, input backlash and asymmetric output constraint. Taking into account the effects of external disturbance and input backlash, the RM system with fuel rod is modeled as a copling partial differential equation-ordinary differential equation (PDE-ODE). Using the backstepping method, an adaptive neural network control scheme is designed to drive the RM and bridge to the desired positions and simultaneously reduce the vibration of fuel rod. A novel asymmetric tangent-type barrier Lyapunov function (Tan-BLF) is constructed to restrict the position tracking error into the given range. The formulation of backlash nonlinearity is transformed into the expected input and nonlinear error. Then the combination of input backlash error and boundary disturbance is defined as a disturbance-like item. Applying the robust control strategy and adaptive technique, two auxiliary input signals are proposed to offset the impact of the disturbance-like item. The adaptive neural network (NN) is employed to compensate for the system uncertainty. The practical stability of the RM system with the proposed control is demonstrated via the theoretical Lyapunov analysis. Simulation verifies the performance of the designed control scheme.

The search for baseline events for assessing the safety of nuclear refueling operations at nuclear power plants

The relevance of the topic of the safety of nuclear refueling operations is associated with the specificity of exploitation of RBMK units. One of the most hazardous, from the perspective of accidents at modern nuclear power plants, is the process of nuclear fuel reloading. The operations on rearrangement of fuel cartridges entail the risk of fuel damage, and thus, the likelihood of the release of radioactive substances exceeding the permissible limits. The process of reloading RBMK, if the reactor is at full capacity, consists of the vast number of complex operations characterized by a range parameters. Non-observance of the criteria for carrying out operations, or if the parameter values exceed permissible limits, with high probability leads to an accident. This article explores the possibility of application of formalized approach towards determination of the baseline events that may cause accidents for the purpose of the development of essential protection instruments. The formal approach would allow detecting the excessiveness in protection instruments on the existing blocks, as well as revealing the accident situations that cannot be prevented using these protection instruments. The author formulated systemic approach towards comprehensive assessment of the accident rate of structurally complex systems. Adaptation of this method relative to REM allows systematizing the search for baseline vents that entail uncontrolled situations, as well as optimizing the protection instruments that would ultimately enhance reliability of the system, simplify the exploitation process, and reduce the time of operating cycle of the controller for processing of the protection.

Active vibration control of a flexible rod moving in water: Application to nuclear refueling machines

This paper addresses a simultaneous control of the positions of the bridge and trolley and the vibrations of the load of a nuclear refueling machine (RM) that transports nuclear fuel rods to given locations in the nuclear reactor. Hamilton’s principle is used to develop the equations of motion of the RM. The lateral and transverse vibrations of the fuel rods during their transportation in water are analyzed. In deriving the control law, the nonlinear hydrodynamic forces acting on the rod are considered. Then, a boundary control scheme is developed, which suppresses the lateral and transverse vibrations simultaneously in the course of the transportation of the fuel rod to the desired locations. Furthermore, Lyapunov function-based stability analyses are performed to prove the uniform ultimate boundedness of the closed loop system as well as the simultaneous control of the positions of the bridge and trolley under the influence of nonlinear hydrodynamic forces. Finally, experimental and simulation results are provided to demonstrate the effectiveness of the proposed control scheme.