KR20010114106A - Dissipation Method of Coil Energy of Control Element Drive Mechanism for Nuclear Reactor - Google Patents

Abstract

The present invention relates to a method of releasing residual energy of a coil; Its purpose is to facilitate the adjustment of the mechanical motion dismantling delay time in the existing control rod drive system through the application of negative voltage, so that the power performance applied to the control rod drive device even when the control object is changed, such as the design change of the control rod drive device, The present invention provides a method of releasing residual energy of a nuclear reactor control rod drive system which can be improved and facilitated to change the control logic.

Description

Dissipation Method of Coil Energy of Control Element Drive Mechanism for Nuclear Reactor

The present invention relates to the improvement of the control logic of the reactor control rod drive device through the negative voltage application method.

The conventional control rod drive device obtains the desired mechanical dismantling delay time by applying the divergent resistor to the power supply device as shown in FIG. 1 to reduce the time constant value of the load. Mechanical dismantling delay time is one of the important factors that determine the control sequence used to drive the control rod drive system. Therefore, the driving interval of the control rod drive device is determined by adjusting the mechanical dismantling delay time. However, it is not easy to adjust the mechanical dismantling delay time according to the driving speed because divergent resistors use optimized resistance values in design. In order to adjust the mechanical dismantling delay time, it is necessary to adjust the time constant of the load by changing the resistance value of the divergent resistor, because the change of the time constant of the load may provide a cause of instability of the power supply. In addition, the design of the power supply device is limited when the divergent resistor method is used. That is, it is difficult to use the power control technology using the latest technology, such as the propagation pulse width modulation method, since the switch must always be open when outputting zero voltage as shown in FIG.

In order to solve the conventional problems, the present invention allows the mechanical dismantling delay time to be freely adjusted within a certain range by using a negative voltage application method different from the conventional divergence resistor method, thereby controlling the control time accordingly. In addition to facilitating the change of the quantum, when applying the technology to the reactor control rod drive system that can more easily control the power supply such as the full bridge pulse width modulation feedback control method. The purpose of the present invention is to propose a method of releasing residual energy of nuclear reactor control rod drive system.

1 is a conceptual diagram of a residual energy dissipation method by a conventional divergence resistor method

2 is a flowchart illustrating a negative voltage causal process.

3 is a current response characteristics and mechanical behavior of the control rod drive device according to the voltage applied

4 is a conceptual diagram of a control rod driving device power supply method using a negative voltage applying method

The present invention relates to a method of releasing residual energy of a coil; More specifically, the present invention relates to a method for releasing residual energy of a reactor control rod drive device that increases the design flexibility of a power supply device and facilitates a change of control logic by adopting a negative voltage application method instead of a resistor divergence method.

Control of the control rod drive device is composed of an electromagnet driving the jack and an electromagnet lifting it, these electromagnets are supplied with magnetic energy by the corresponding coils. The power supply device applies a DC voltage to each coil so that a current flows, which is converted into magnetic energy by the electromagnet and then converted into mechanical energy, thereby providing jack torque or lifting force of the control rod.

2 is a flowchart illustrating a process of applying a negative voltage according to the present invention. The control rod drive device repeats the process of mechanical movement, holding of mechanical movement, and mechanical disengagement by releasing residual energy to drive the control rod (see FIG. 3). When dismantling, a negative voltage is applied to increase the potential difference to shorten the mechanical motion dismantling delay time. Calculate the expected negative potential difference according to the drive speed for the change of the external drive speed such as the operator. The driving speed is determined by the mechanical motion occurrence delay time, mechanical motion dismantling delay time and the time to minimize the electromagnetic interference of adjacent coil days. Can handle The expected mechanical dismantling delay time is calculated from the drive speed, from which the expected negative voltage is calculated. In order to generate the negative voltage, the propagation type switching is performed through the pulse width modulation corresponding to the negative voltage, and the negative voltage is applied, and the current response characteristic decreases exponentially according to the time constant of the coil load of the control rod drive device. (Mechanical dismantling current) is reached. In this case, the current signal flowing through the coil from the current sensor is analyzed, and the actual mechanical dismantling delay time is analyzed, and the corresponding negative voltage is calculated and compared with the expected negative voltage calculated through the driving speed requirement. This optimizes the applied negative voltage for residual energy dissipation.

The above is described in detail according to the mechanical motion principle of the control rod drive device as follows. The most important factors in determining the time range of the control logic are the mechanical motion occurrence delay time and the mechanical motion release delay time. Two variables depend on the value of the time constant of the coil located in the control rod drive system. The mechanical motion generation delay time is the time interval until the electrical energy is converted into mechanical motion requiring a constant energy. Mechanical dismantling delay time is similar in concept to mechanical motion occurrence delay time, but it means the time interval from dismantling electric energy to dismantling mechanical motion.

The factors that determine the two factors are determined by the balance between electromagnetic and mechanical forces.

The current for supplying the magnetic energy required for the mechanical device to move is called I _e , and the inductance of the coil is L (I), which varies according to the current response according to the magnetization of the electromagnet, the resistance of the coil R, and the power supply device. If the voltage applied from V _h is the current flowing in the coil can be expressed as follows.

here ,

The mechanical motion generating delay time is the time from the application of the voltage V _h until the current reaches I _e and the mechanical motion occurs.

Becomes

Where x is the displacement of the mechanical system, Is determined by the degree of magnetization of the electromagnet, which can be interpreted in two ways: when the electromagnet is saturated and when it is not saturated.

The mechanical dismantling delay time can be approached similarly to the mechanical motion occurrence delay time.

When the mechanical system drops the voltage to zero voltage while maintaining the displacement previously generated by the magnetic force by the constant current supply, the current responds as follows.

Finding the mechanical dismantling delay time t _d

Becomes Where I _d is the current value when mechanical disintegration occurs.

In the case of a control rod driving device composed of a plurality of magnets, if one electromagnet is mechanically generated or dismantled, it is generally impossible to perform mechanical motion by other electromagnets in parallel. Therefore, the mechanical motion generation delay time or mechanical motion release delay time is the most important factor in the control sequence. In a system with an arbitrary time constant, the shortest driving sequence exists. If a shorter driving sequence is required, an analysis is required along with additional devices that can reduce the mechanical motion generation delay time or mechanical dismantling delay time. . Existing nuclear power plants use the method of reducing the time constant when the applied voltage is off by using the divergent resistor. Inserting divergence resistors ( ) And not inserted ( The time constants of) are compared as follows.

Where R _L is the resistance of the coil and R _d is the divergence resistance.

The reduction effect of mechanical dismantling delay time is shown in FIG.

However, in the divergent resistance method, as shown in FIG. 1, the load must be isolated from the power supply to form a closed loop including the divergent resistor, so that the load is not electrically disconnected from the power supply when the mechanical motion is dismantled. It is difficult to use.

The present invention uses a negative voltage application method different from the conventional divergent resistor system. The theoretical background for this is as follows. The initial current flowing through the control rod drive coil is I _L as the holding current, and the inductance of the coil is expressed by the following equation when L (I, x) applied negative voltage is V _N.

,

In this case, it can be assumed that the inductance L (I, x) is a constant for a certain section with respect to time except for a period during which mechanical displacement occurs. Solving the differential equation, the current is

Where I _N is the maximum negative current in the negative voltage applied. Case 2 of Figure 3 as a graph showing the above equation Is assumed to be a constant. Until a mechanical displacement actually occurs Has two constant values. This value is determined by the saturation of the electromagnet. Therefore, if we solve the above equation, the time until the mechanical dismantling occurs is given by

From here Is the current value at which mechanical motion starts to disintegrate, and I _N is the maximum current in the negative direction when the negative voltage V _N is applied. Therefore, as shown in FIG. 3, the mechanical dismantling delay time can be adjusted by applying the negative voltage V _N.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by those skilled in the art without departing from the gist of the present invention as claimed in the claims. Of course, such changes will fall within the scope of the claims.

In the present invention, as a method of dissipating the residual energy of the coil, it is possible to easily control the driving sequence of the control rod drive device by applying a negative voltage instead of the passive method by the conventional divergence resistor to dissipate the residual energy of the coil in an active manner. It was made. In addition, by changing the coil residual energy dissipation circuit that acted as a limiting factor in the design of the power supply, the advanced power supply such as the propagation feedback control method can be used to control the control rod drive system.

Claims (3)

By adopting a method of dissipating coil residual energy by applying a negative voltage in the control rod driving device of a light reactor Requesting a change in the drive speed of the control rod from the operator or outside, Calculating the dismantling delay time of the mechanical motion in the control rod drive device by the required drive speed, Calculating an expected negative voltage using the calculated dismantling delay time of the mechanical motion, And generating a negative voltage based on the calculated negative voltage, and applying the generated negative voltage to dissipate the residual energy of the control rod driving coil. The method according to claim 1, The applied negative voltage dissipates the residual energy of the reactor control rod drive device, characterized in that the negative voltage can be changed and supplied by calculating and calculating the dismantling delay time of the mechanical motion according to the change of the driving speed of the control rod from the operator or the outside. Way. In the control rod drive device of a light reactor, Drive speed change input unit for changing the drive speed of the control rod from the operator or outside, An arithmetic unit for calculating an expected negative voltage by using the dismantling delay time of the mechanical motion in the control rod drive device and the calculated dismantling delay time of the mechanical motion by the required driving speed; A method for releasing residual energy of a reactor control rod driving apparatus, comprising: a negative voltage generator for generating a negative voltage based on the calculated negative voltage; and applying a generated negative voltage to a signal for releasing residual energy of the control rod driving coil. .