JPS6123996A - Transient relaxing method of heat in liquid-metal cooling fast breeder reactor - 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 <Industrial Application Field> The present invention relates to a method for thermal transient mitigation in a liquid metal cooled fast breeder reactor of a loop-type tanker.

<Prior Art> Generally, in a liquid metal cooled fast breeder reactor (LMFBR), when an abnormal situation occurs during power operation, the reactor shifts to scram force and decay heat removal operation.

That is, as shown in the block diagram of the conventional plant interlock circuit in Figure 4, when a reactor scram (trip) occurs due to a manual trip, a decrease in the primary pump rotation speed, or a decrease in the secondary pump rotation speed, the primary and secondary pumps are simultaneously activated. The main motor of the secondary main circulation pump is tripped, and when each pump reaches the set rotation speed while coasting due to rotational inertia, the low speed of the primary and secondary main pump pony motors that were finally started A method is adopted in which the operation is taken over and then the decay heat removal operation is carried out.

<Disadvantages of Prior Art> However, the conventional method described above has the problem that a temperature stratification phenomenon occurs in the brenum portion of the reactor vessel, and a large thermal transient load is applied to the component equipment.

In order to solve these problems, there is a method of increasing the inertia of the pump, but it has been difficult to optimize the temperature change of the component equipment.

<Problems to be Solved by the Invention> The present invention 8A is aimed at a liquid metal cooled fast breeder reactor (CLMFBR).

Means to solve problems〉 In order to achieve the above-mentioned purpose, during reactor scram,
The rotation speed of the main circulation pump main motor is lowered at an appropriate speed without tripping, and the operation is shifted to decay heat removal operation.
A low coast down curve that will make the thermal transient on the 1y equipment the gentlest is found in advance through analysis, etc., and stored in the digital controller for the pump rotation speed. During a reactor scram, the pump rotation is determined based on the above curve. The present invention provides a method for thermal transient relaxation in a liquid metal cooled fast breeder reactor, which is characterized in that it is fully controlled.

<Function> In the present invention, after the reactor scram, a large amount of low-temperature fluid from the reactor core flows into the earth pre and nam parts compared to the conventional method, and mixing with high-temperature fluid is promoted, so temperature stratification is prevented. As a result, thermal transients applied to each component device are greatly slowed down.

<Example> ν Below, all examples according to the present invention will be described in detail based on FIG. 1 and FIG. 3.

Figure 3 shows the basic concept of plant control system? It is a block diagram showing that each control system in the plant control system (in which the control rod position, pump rotation speed, etc. are controlled by a digital controller.

In addition, in the present invention, among the above-mentioned plant control systems, the program of the digital controller of each control system except the reactor power control system is partially changed, and when a reactor scram occurs, a preset value is set as the runback curve. The entire time series is output to the pump side.

FIG. 2 is a chart showing an example of a run bank curve of rotational speed according to the present invention.
The program is approximated by a polygonal line at about the klo point of this curve.

Furthermore, in order to prevent the temperature stratification phenomenon that occurs when low-temperature fluid from the reactor core flows into the upper brenum after the reactor scram, it is necessary to Since the reactor must be thoroughly mixed with sodium and the core flow rate is small during low power operation, it is necessary to extend the coastdown time.

So, what kind of pump rotation speed runback curve should I ask depending on the operating power level? Prepare it, select the most appropriate one, and output it.

On the other hand, Figure W1 is a block diagram of the plant interlock circuit of the present invention. Conventionally, as shown in Figure 4, the main motor of the pump is tripped, and when the rotation speed reaches the set speed from the coast down, the pump main motor is tripped. The method was to have the pony motor that had already started take over, but according to the present invention, the rotation speed is reduced without tripping the main motor.
Decay heat operation is also continued by the main motor at the set rotation speed.

This eliminates the need for a pony motor to be activated in advance.

<Effects of the Invention> As explained in detail above, the method of thermal transient mitigation in a liquid metal cooled fast breeder reactor according to the present invention utilizes the existing plant control system and partially changes the program for the digital controller. Since it can be implemented with a simple configuration that requires only -mW addition to the plant interlock circuit, a pony motor is not required, and costs can be significantly reduced.

Further, according to the present invention, during a reactor scram, a large amount of low-temperature fluid from the reactor r9 section flows into the upper blenheim section and mixing with the high-temperature fluid is promoted, so that the temperature stratification phenomenon is suppressed and , the thermal transient load applied to the initial temperature control equipment can be significantly alleviated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the plant interlock circuit of the present invention, Fig. 2 is a fixed fit showing an example of a runback curve of the pump rotation speed according to the present invention, and Fig. 3 is a diagram showing the basic concept of the plant control system. Block Diagram FIG. 4 is a block diagram of a conventional plant interlock circuit.

Claims (1)

[Claims] In a liquid metal cooled fast breeder reactor, during the reactor scram, controlling the rotation speed of main circulation pumps such as a primary pump, a secondary pump, and a feed water pump, and the flow rate of the main circulation pumps.
A method for mitigating thermal transients, characterized in that the thermal excess applied to the components of the nuclear reactor stored in a rotational speed control device such as a digital controller is reduced under program control along a curve that makes the thermal excess applied to the components of the nuclear reactor the gentlest.