Load-follow Operation Research Articles

Application of Fuzzy Logic Controller to Load-Follow Operations in Pressurized Water Reactors

The fuzzy logic controller was developed to control load-follow operations in pressurized water reactors. The reactor core characteristics change according to different fuel cycles or core exposures, thus making a nonlinear time-varying control problem. This proposed method, however, does not require a mathematical model to design the controller, and so avoids redesigning or tuning controller gain for various cores. Clearly, this method is very suitable for reactor load-following operation control. The control system has two subsystems: one is to track the desired power, and the other is to keep axial offset close to the target value. Both controllers use fuzzy logic: one is the conventional type, and the other uses fuzzy logic to tune the parameters of the controller so the controller can correspond to various core characteristics. Simulation results show that the control system performs well for different cores, and so this system is useful for load-follow operation.

Application of Fuzzy Logic Controller to Load-Follow Operations in Pressurized Water Reactors.

The fuzzy logic controller was developed to control load-follow operations in pressurized water reactors. The reactor core characteristics change according to different fuel cycles or core exposures, thus making a nonlinear time-varying control problem. This proposed method, however, does not require a mathematical model to design the controller, and so avoids redesigning or tuning controller gain for various cores. Clearly, this method is very suitable for reactor load-following operation control. The control system has two subsystems: one is to track the desired power, and the other is to keep axial offset close to the target value. Both controllers use fuzzy logic: one is the conventional type, and the other uses fuzzy logic to tune the parameters of the controller so the controller can correspond to various core characteristics. Simulation results show that the control system performs well for different cores, and so this system is useful for load-follow operation.

Fuel rod and core materials investigations related to LWR extended burnup operation

The paper deals with tests and recent measurements related to extended burnup fuel performance and describes test facilities and results in the areas of waterside cladding corrosion and irradiation-assisted stress corrosion cracking (IASCC). Fuel temperature data suggest a gradual degradation of UO 2 thermal conductivity with exposure in the range 6–8% per 10 MWd/kgUO 2 at temperatures below 700°C. The effect on the fuel microstructure of interlinkage and resintering phenomena is shown by measuring the surface-to-volume ( S/ V) ratio of the fuel. Changes in S/V with burnup are correlated to power rating and fuel operating temperature. No evidence was found of enhanced fission gas release during load-follow operation in the burnup range 25–45 MWd/kgUO 2. The effect of high lithium concentration (high pH) on the corrosion behaviour of pre-irradiated high burnup Zircaloy-4 fuel rods subjected either to nucleate boiling or to one-phase cooling conditions was studied. The oxide thickness growth rates measured at an average burnup up to 40 MWd/kgUO 2 are consistent with literature data and show no evidence of corrosion enhancement due to the high lithium content and little effect of cooling regime. A test facility for exploring the effects of environmental variables on IASCC behaviour of in-core structural materials is described.

Extension of Load Follow Capability of a PWR Reactor by Optimal Control

The problem of extending that part of the fuel life cycle during which a reactor is capable of sustaining load-follow operation is formulated as an optimal control problem. A two-node model representation of pressurized water reactor dynamics is used, leading to a set of non-linear ordinary differential equations. Differential Dynamic Programming is used to solve directly the resulting nonlinear optimization problem and obtain the trajectories of soluble boron concentration and control rod insertion. Results of computations performed for a reference reactor are presented, showing how the optimal control policy stretches the capability of the reactor to follow an average daily load curve towards the end of the fuel life cycle.

Optimal Control of a PWR Reactor to Extend Load Follow Capability

The problem of extending that part of the fuel life cycle during which a reactor is capable of sustaining load-follow operation is formulated as an optimal control problem. A two-node model representation of pressurized water reactor dynamics is used, leading to a set of non-linear ordinary differential equations. Differential Dynamic Programming is used to solve directly the resulting non-linear optimization problem and obtain the trajectories of soluble boron concentration and control rod insertion. Results of computations performed for a reference reactor are presented, showing how the optimal control polijy stretches the capability of the reactor to follow an average daily load curve towards che end of the fuel life cycle.