JPS58221190A - Reactor power control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor power control device that monitors fluctuations in feed water temperature, which are a factor of power fluctuations, and performs appropriate control.

As for conventional technology, there is no example of output control based on feed water temperature in a boiling water reactor. Although there is a patented example of detecting a drop in feed water temperature and running back the recirculation flow rate, this method results in a high heat flux scram, which does not achieve the original purpose from the viewpoint of improving drivability.

The purpose of the present invention is to detect a drop in feed water temperature that causes an excessive increase in output, and if the temperature decrease exceeds an allowable value, to quickly reduce the output by inserting a selective control rod, thereby preventing an excessive increase in output. The object of the present invention is to provide a device that reduces thermal severity while allowing continued operation.

The present invention focuses on the fact that during normal operation, the feed water temperature changes constantly depending on the reactor output, and when the feed water temperature drops beyond this range, the feed water heating system or turbine bypass system is activated. Assuming that an abnormality has occurred, selective control rods are inserted in advance to prevent an excessive increase in output.

FIG. 1 is a schematic diagram of a boiling water reactor system.

Steam generated in the nuclear reactor 1 typically passes through a control valve 4 and reaches a turbine 6 to perform work. When an abnormal rise in pressure or a disturbance in the system load occurs, the bypass valve 5 opens to suppress an excessive rise in pressure.

On the other hand, the steam that has done work in the turbine 6 is cooled in a condenser 7, becomes cold water, and reaches a water supply pump 8.

The feed water is pressurized by the feed water pump 8, passes through the bleed line 10, is heated by the bleed steam supplied from the turbine 6 in the feed water heater 9, and is supplied to the nuclear reactor.

The reactor output is detected by the neutron flux detector 3.

The feed water temperature is detected by a feed water temperature detector 11. A drop in the feed water temperature occurs when the bypass valve opens and the bleed steam decreases, or when the heating capacity decreases due to a failure of the feed water heater 9.

Three control rods, which are reactor power control equipment, can be pulled out and inserted at normal speeds, as well as by rapid insertion of some control rods (selective control rod insertion) or rapid insertion of all control rods (scram). can perform rapid descents.

FIG. 1 shows a flow rate control curve for a boiling water plant. This figure shows the relationship between the reactor output and the core flow rate in the natural circulation operation state. This shows the correlation between the core flow rate and the reactor output when the reactor outlet flow rate is changed with the control rod pattern having the rated output at the rated core flow rate.
Most of the operation will be carried out on this rated output control curve. This is the heat flux high scram setting value, which is set to maintain the integrity of the fuel.

If a significant drop in feedwater temperature occurs, the temperature of the core cooling water will drop, reducing the core void fraction.

A unique characteristic of boiling water reactors is that the reactor power increases to keep the core void fraction constant. As a result, core flow 1
remains approximately constant, the furnace power will increase, and the heat flux high scram set point will be reached.

FIG. 3 is a correlation diagram between reactor power and feed water temperature. The fluctuation range of the feed water temperature during normal operation is small, and the curve is almost constant as shown in the curve. On the other hand, if a disturbance occurs,
For example, if the feed water heater is bypassed, the feed water temperature will drop significantly from this curve. The curved line indicates the lower limit of the feed water temperature that is allowable from the viewpoint of preventing a high heat flux scram or a decrease in stability due to an increase in output. In the present invention, the reactor output is detected, and the allowable feed water temperature is determined according to the reactor output.
It is determined from the feed water temperature allowable curve E and compared with the reactor feed water temperature, and if this falls below the allowable temperature curve, selective control rods are promptly inserted to suppress the increase in power.

FIG. 4 shows the alms II (+7) of the present invention.

In order to determine the allowable feed water temperature, the average neutron flux signal 12 is passed through a first-order lag circuit 13. - In order to avoid malfunction of the next delay circuit 14 due to neutron flux noise, etc., set a time constant of approximately 6 seconds so that the signal corresponds to the heat flux. The temperature program circuit 15 is a circuit for determining the allowable feed water temperature, as shown in FIG. 3, based on the reactor output signal (heat flux equivalent signal). This allowable feed water temperature is compared with the feed water temperature signal 13 in an adder 16, and if the feed water temperature signal 13 is lower than the allowable feed water temperature, a selection control rod insertion signal is issued from the alarm setting device and output. descend quickly.

FIG. 5 is a diagram illustrating the present invention in detail.

By implementing the present invention, the cause of the abnormal rise in the reactor can be quickly detected and proactive output control can be performed.
It is possible to suppress excessive output increases, avoid heat flux scrams, improve operating efficiency, and increase thermal margin.

In FIG. 3, average neutron flux signal 1 is used as the reactor output equivalent signal, but equivalent performance can be expected with steam flow No. 11.

In addition, selective control rod insertion is used as a reactor power control means, but as an alternative means, for example, if automatic output control using normal control rod operation is possible, by changing to this, equivalent performance can be achieved. can be obtained.

According to the present invention, since a drop in feed water temperature, which causes an abnormal increase in reactor output, is directly detected, it is possible to detect an abnormality before this influence is significantly exerted on the reactor, and by inserting selective control rods. It not only enables appropriate output control and avoids high heat flux scrams, etc., but also improves the operating rate.
The thermal margin can be increased, and the degree of freedom in core operation can be greatly increased.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the reactor and water supply system, Fig. 2 is a flow control curve diagram of the reactor, Fig. 3 is a correlation diagram between reactor output and feed water temperature, and Fig. 4 is a diagram of the power control function according to the present invention. The explanatory diagram, FIG. 5, is a diagram illustrating the effect of implementing the present invention. 1... Nuclear reactor, 2... Control rod, 3... Neutron detector, 4... Turbine control valve, 5... Turbine bypass valve, 6... Turbine, 7... Condensate 8...Water pump, 9...Water heater, 10...Bleed air line, 11...Temperature detection $2 S diagram

Claims (1)

[Claims] 1. In a boiling water reactor, the feed water temperature is monitored and the output is automatically controlled to be within a predetermined deviation with respect to the feed water temperature set value programmed with the reactor output. Reactor power control device. 2. Reactor power control according to claim 1, wherein the feed water temperature and the reactor power equivalent signal are detected, and the power is automatically controlled by control rod operation so that the feed water temperature and the reactor power equivalent signal are within a predetermined deviation. Device. 3. In claim 2, the feed water temperature setting value is the feed water temperature in the normal operating state, and when the temperature deviation exceeds a temperature deviation determined to prevent an excessive increase in output, the output is adjusted by inserting a selective control rod. A nuclear reactor power control device that suppresses the increase in power.