Dynamics of reverse osmosis in a standalone cogenerative nuclear reactor (Part II: load changes)
The coupling of desalination units with nuclear power plants has been studied in the present work in this respect, the dynamic behaviour of the pressurised water reactor safety features, represented by the integrity of the fuel cladding, under some transient cases caused by secondary circuit load changes. A cosine-shaped heating through the reactor fuel is taken with its corresponding coolant lumps, to simulate realistic cases encountered in nuclear reactors. As an example, the mathematical model for the Westinghouse 3411 MWth pressurised water reactor, a familiar design with widely published design data was developed. The model consists of two parts; the first one is concerned with the dynamics of the primary side of the reactor; and the second, with the secondary side of the plant. To study the dynamics of the reactor, a 17-lumped parameters model was used. This is a first-order differential equation deduced from the first principles considering six groups of delayed neutrons. A computer program was developed using the Runge-Kutta method to solve these equations and to predict the behaviour of the state variables with time. Two case studies were considered as examples for normal transients. The developed model, which describes the dynamic response of the reactor, primary circuit and secondary circuit, has been analysed and verified with the relevant models. The first case, represented in Part 1 of this study, is concerned with the effect of changes of primary side transient reactivity, including the movement of the reactor control rods. The second one, represented in Part 2 of this study, considers the effect of the secondary side transient reactivity, as the load changes, on the system behaviour. As an example for the secondary side transient, load perturbations, such as load variations in standalone RO desalination units, are selected to study the effect of changing the secondary side conditions on the plant behaviour. The results showed that the reactor components and the fuel matrix should not be affected, and the fuel-cladding integrity is maintained within the safe limits, in all scram cases of RO desalination units coupled with nuclear power plants in the case of either a planned shutdown or an accidental shutdown.
Keywords: nuclear desalination, waterelectricity cogeneration, modelling, dynamic simulation, pressurised water reactors, PWR, reactor neutronics, reactor control, fuel cladding integrity, reverse osmosis, nuclear reactors, load changes, nuclear safety