Abstract: The present invention relates to a method for controlling a pressurized water reactor (100) comprising the steps that involve measuring the effective power (Pe) of the nuclear reactor; acquiring a reference value for the desired power (Pc); acquiring an estimated duration (DURATION) for the increase in power in order to achieve said reference value of the target power (Pc) desired, said estimated duration (DURATION) corresponding to the time taken for the power to increase from said effective power (Pe) to said reference value for the target power (Pc); determining the reference position (Z) of at least one control rod cluster among said plurality of control rod clusters (40) in order to achieve said reference value for said target power (Pc) desired as a function of said estimated duration (DURATION), of said measured effective power (Pe) and of said reference value for said target power (Pc); monitoring the position of said at least one control rod cluster so as to position it in its reference position (Z).

Abstract: In order to realize a semiconductor device of enhanced TFT characteristics, a semiconductor thin film is selectively irradiated with a laser beam at the step of crystallizing the semiconductor thin film by the irradiation with the laser beam. By way of example, only driver regions (103 in FIG. 1) are irradiated with the laser beam in a method of fabricating a display device of active matrix type. Thus, it is permitted to obtain the display device (such as liquid crystal display device or EL display device) of high reliability as comprises the driver regions (103) made of crystalline semiconductor films, and a pixel region (102) made of an amorphous semiconductor film.

Abstract: This document's object is to provide an axial power distribution control method in which only the control of an axial power distribution in a nuclear reactor with a simple operation with a clear operational target keeps the control of a xenon oscillation, thereby suppressing the xenon oscillation to an extremely small magnitude in advance at the same time.

Abstract: An axial power distribution control device includes an axial offset calculation unit 52, a parameter calculation unit 53, and an axial offset determining unit 55. The axial offset determining unit 55 predicts whether a core axial offset of the power distribution is increased or decreased after a current time, based on a major axis of an ellipse drawn by the xenon parameter and the iodine parameter calculated by the parameter calculation unit 53 and the xenon parameter and the iodine parameter at the current time. This makes it possible to predict a change of the axial offset of the power distribution of a reactor for suppressing a xenon oscillation in the reactor.

Abstract: To predict xenon oscillation at the present time and later. For this purpose, as an axial offset of a power distribution of a reactor is represented by AOp, an axial offset of a power distribution based on xenon distribution is represented by AOx, and an axial offset of a power distribution based on an iodine distribution is represented by AOi, a parameter DAOpx(=AOp?AOx) and a parameter DAOix(=AOi?AOx) are described by a relational expression of a trigonometric function and an exponential function using an angular frequency of xenon oscillation. Next, phases with respect to initial values of the parameters DAOpx and DAOix are obtained (Step S101). The parameter DAOpx and the parameter DAOix expressed by the obtained phase and a coefficient of the relational expression obtained from this phase are plotted on an X coordinate and a Y coordinate, respectively.

Abstract: In one embodiment, the method includes determining the safety limit minimum critical power ratio using the operating limit minimum critical power ratio, a change-in-critical-power-ratio distribution bias and a change-in-critical-power-ratio distribution standard deviation.

Abstract: Discussed is a method and device for increasing the operational flexibility of a current-generating system with a turboset, comprising a turbine coupled to an electrical generator, a power set point value being predefined, and a future target time at which the turboset is supposed to be at the power set point value, so that a power curve is determined via the power set point value and the target time, the turboset being operated starting from a actual power value at an actual time along the power curve such that the predefined power set point value is reached at the predefined target time. Also discussed is a gas turbine and to a steam turbine in accordance with the above description.

Abstract: To predict xenon oscillation at the present time and later. For this purpose, as an axial offset of a power distribution of a reactor is represented by AOp, an axial offset of a power distribution based on xenon distribution is represented by AOx, and an axial offset of a power distribution based on an iodine distribution is represented by AOi, a parameter DAOpx(=AOp?AOx) and a parameter DAOix(=AOi?AOx) are described by a relational expression of a trigonometric function and an exponential function using an angular frequency of xenon oscillation. Next, phases with respect to initial values of the parameters DAOpx and DAOix are obtained (Step S101). The parameter DAOpx and the parameter DAOix expressed by the obtained phase and a coefficient of the relational expression obtained from this phase are plotted on an X coordinate and a Y coordinate, respectively.

Abstract: A method of controlling a nuclear power plant includes determining a first maximum linear heat generation rate and a first minimum critical power ratio by a core monitoring system, and determining a second maximum linear heat generation rate and a second minimum critical power ratio by utilizing the first maximum linear heat generation rate and the first minimum critical power ratio determined by the core monitoring system and plant data. The second maximum linear heat generation rate and the second minimum critical power ratio are compared with predetermined thermal limit values and a control signal outputted from an automatic power regulator system to a re-circulation flow control system and to a control rod control system is held when at least one of the second maximum linear heat generation rate and the second minimum critical power ratio exceeds the predetermined thermal limit values.

Abstract: A control system, and a control method, of a nuclear power plant capable of easily executing automatic output regulation by an automatic power regulator system even when a lower-accuracy maximum linear heat generation rate and a lower-accuracy minimum critical power ratio are determined in a short cycle by using brief calculation. While a core monitoring system does not calculate a maximum linear heat generation rate and a minimum critical power ratio, they are determined by utilizing the maximum linear heat generation rate and the minimum critical power ratio calculated by the core monitoring system as well as plant data, and the lower-accuracy maximum linear heat generation rate and the lower-accuracy minimum critical power ratio so determined are compared with predetermined thermal limit values.

Abstract: The present invention is a system that updates a pressurized water reactor core model, or data file describing the core, periodically using measured values determinable from core instrumentation. The system starts with a calibrated model calibrated from a flux map and a boron concentration measurement both determined monthly. Reactor system measurements are performed and the model is updated from the measurements using a standard depletion calculation. Some of the measured values are also used to determine measured actual values of axial offset and pinch. Standard neutronics equations are used to calculate analytical values of axial offset and pinch from the model, and the measured and calculated values are compared. If a deviation beyond a certain magnitude is detected, buckling coefficients in the model are adjusted to compensate for model drift. The updated model is stored and a time-out period is entered until it is time for another drift compensation cycle to start.

Abstract: In a nuclear electric power generating plant connected to an electric power system, an output of a nuclear reactor of the plant is reduced during a nighttime operation, increased to a predetermined level during a daytime operation and reduced during a lunch time operation in which a poisonous effect of fission products, i.e., X.sub.e.sup.135 produced during a decreased output running during a nighttime operation becomes significant.

Abstract: A mechanical spectral shift reactor comprises apparatus for inserting and withdrawing water displacer elements having differing neutron absorbing capabilities for selectively changing the water-moderator volume in the core thereby changing the reactivity of the core. The displacer elements may comprise substantially hollow cylindrical low neutron absorbing rods and substantially hollow cylindrical thick walled stainless rods. Since the stainless steel displacer rod have greater neutron absorbing capability, they can effect greater reactivity change per rod. However, by arranging fewer stainless steel displacer rods in a cluster, the reactivity worth of the stainless steel displacer rod cluster can be less than a low neutron absorbing displacer rod cluster.

Abstract: Axially spaced measurements of the neutron flux in a pressurized water reactor are used to generate point-by-point signals representative of the core average xenon-135 axial distribution and the rate of change thereof. These signals may be used directly to generate visual displays representative of the xenon-135 distribution and/or can be used to generate a skewness signal representative of divergence of the xenon-135 distribution from the equilibrium, full power axial xenon-135 distribution and a rate of change of the skewness signal. A two dimensional comparison of the skewness and rate of change of skewness signals can be used in a xenon control mode of a wide band constant axial offset control system to automatically position the control rods to dampen the xenon transients.

Abstract: The fissile inventory required in operating a negative power coefficient nuclear reactor in an electric power generating system is reduced by cycling the load imposed on the system when 100% power can no longer be maintained at equilibrium due to xenon poisoning in order to induce an oscillation in the xenon concentration which is in antiphase wtih the power requirements so that 100% power can be maintained at least during part of the day. The load can be progressively reduced by a preset amount each night or a xenon suppression controller which forecasts the xenon reactivity at the time selected for a return to full power as a function reactor history, current reactor flux and an arbitrary load schedule can be used to determine the maximum reduced power level that will permit operation at full power at the selected time.

Abstract: A power change operating method of a boiling water reactor, in which an operation allowable range is defined by the relation between xenon and iodine concentrations, the present concentrations is compared with the allowable range, and the core flow is controlled so that the concentrations after the change can be included within the allowable range.

Abstract: A method of operating a nuclear reactor adapted to use cross-shaped control rods. The control rods are grouped into a plurality of groups having a first group consisting of a control rod located at the center of the core, a second group consisting of 8 control rods surrounding the control rod of the first group, a third group consisting of control rods located adjacent to and outside of the control rods of the second group, and other groups determined successively in the same manner as in the third group. During the operation period other than the period in which the number of the control rods to be inserted for realizing the critical condition of said nuclear reactor is less than 6, the nuclear reactor is operated with control rod patterns in which the inserted control rods are selected from control rods of alternate or every other groups of said groups so as to include at least a pair of control rods which are located in a similar manner to that of the KNIGHT's movement on a chess board.