JPH0750188B2 - Self-actuated reactor controller - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention introduces the liquid neutron absorber into the core by the rapid volume expansion accompanied by boiling of the liquid, and also discharges the liquid neutron absorber to the outside of the core by the rapid volume contraction accompanying the liquefaction of the liquid, atomic The present invention relates to a self-operating nuclear reactor control device that adjusts or shuts down the power output of a reactor.

[Prior art]

Conventionally, the power output of a nuclear reactor is adjusted or stopped by inserting or pulling out control rods. For this reason, it is necessary to always control the position of the control rod externally.Therefore, there is a possibility that the control of the furnace may be difficult due to the failure or operation of the control system such as the control rod drive device, and the control rod may be damaged due to an earthquake. There is a possibility that the guide rod may be displaced or bent, which makes it difficult to insert the control rod. Also, as a backup, there is a self-operating type furnace stop mechanism that is set to automatically operate at a constant temperature as one of the furnace stop mechanisms dedicated to scrum, but the temperature is momentary and temporary due to fluctuations in the furnace. Even if the value exceeds the set value, there is a risk of activation, and once activated, the control rod will fall and stop the furnace, which may cause a significant hindrance to operation.

[Problems to be Solved by the Invention]

In view of the drawbacks associated with the output adjusting / stopping device using the control rods described above, the present invention is not dependent on the control rods, and by using a self-actuated reactor control device that does not require external control, the output adjustment is of course performed. The purpose of the present invention is to reduce the possibility of scrum failure even when used as a self-actuated reactor shutdown mechanism dedicated to scrum, and to prevent adverse effects on operation due to malfunction.

[Means for Solving the Problems]

In order to achieve the above object, in the present invention, a carrier material having a boiling point slightly higher than the steady operating temperature of the furnace,
A boiling-liquefying chamber containing a liquid neutron absorber that is liquid at a temperature in a steady state of operation of the furnace and has a boiling point sufficiently higher than that of the carrier substance is provided close to the coolant outlet of the fuel assembly. The tubular chabah is disposed at a position in the core surrounded by a plurality of fuel assemblies, and the boiling-liquefying chamber and the tubular chabah are a boiling-liquefying moving tube attached to the bottom of the chamber. It is inserted and connected in the cylindrical chamber. The above-mentioned tubular chamber is of a hermetically sealed type, the expansion chamber is connected to the tubular chamber, and a pipe is provided to connect the tubular chamber to the expansion chamber, and an inert gas is sealed inside. An example of the installation location of the expansion / absorption chamber is below the cylindrical chamber.

[Work]

Since the carrier substance in the boiling-liquefying chamber is boiled and expands in volume by heating with the high-temperature coolant, the liquid neutron absorber in the boiling-liquefying chamber is introduced into the cylindrical chamber through the moving pipe. . The liquid neutron absorber introduced into the cylindrical chamber controls the nuclear reaction. When the temperature of the high temperature coolant is lowered by the control of this nuclear reaction, the carrier substance in the boiling-liquefying chamber is liquefied and the volume is contracted, so that the liquid neutron absorber in the cylindrical chamber passes through the moving tube. Boiling-
It is returned to the liquefaction chamber. There, the nuclear reaction becomes active again. Even if the cylindrical chamber is a closed type, if the expansion chamber is communicated with the expansion chamber so that the pressure can be balanced, the pressure in the cylindrical chamber increases and the boiling-liquefying chamber moves to the cylindrical chamber. It is possible to deliver the liquid neutron absorber of, and the delivery amount of the liquid neutron absorber in this case is not affected by the pressure of the external environment, and the delivery amount is always determined only by the environmental temperature. Is suitable.

【Example】

1A to 1C showing the first embodiment of the present invention,
Reference numeral 10 is a fuel assembly, and the nuclear fuel is indicated by a grid-like diagonal line.
It shows the loading position of. The coolant such as Na is fed from the coolant inlet below the fuel assembly 10 as shown by the arrow, becomes high temperature, and exits from the coolant outlet at the upper end of the fuel assembly 10. A boiling-liquefying chamber 1 is installed in the core upper position near the coolant outlet and in contact with the high temperature coolant. In the boiling-liquefying chamber 1, a carrier substance a having a boiling point Tvap slightly higher than the steady operating temperature of the furnace,
A liquid neutron absorber b having a neutron absorbing capacity is stored. The liquid neutron absorber b is liquid at the temperature in the steady operation state of the furnace, and its boiling point is sufficiently higher than that of the carrier substance a. As an example, in the case of a fast reactor, the material a for transportation has Cs (boiling point 637 ° C) and Rb (boiling point 686 ° C), and the liquid neutron absorber b contains K containing B ₄ C fine particles.
(Boiling point 756 ℃), Na (Boiling point 882 ℃), Li (Boiling point 1342 ℃). In the case of a light water reactor, the substance a for transportation is diphenyl ether (boiling point 257 ° C), and the liquid neutron absorber b
Is diethyl amine containing B ₄ C particles (boiling point 320
℃). A connecting pipe 3 is attached to the bottom of the boiling-liquefying chamber 1. The connecting pipe 3 is inserted into a conventional control rod guide pipe or near a lower portion of a cylindrical chamber 2 surrounded by a plurality of fuel assemblies 10 installed at that position.
A communication pipe 4 is attached to the upper end of the cylindrical chamber 2 to open the inside of the cylindrical chamber 2 to the core gas space in the reactor. To explain the operation in the case of the above configuration, since the boiling point Tvap of the carrier substance a is higher at the steady operating temperature, the carrier substance a is in a liquid or solid state. In this state,
As shown in FIG. 1A, the liquid neutron absorber b is moved to the boiling-liquefying chamber 1 by the pressure of an inert gas such as argon filled in the core through the communication pipe 4 and filling the core. And the nuclear fuel 11 is not affected by the liquid neutron absorber b. Therefore, the reactor continues the fission reaction.
However, the nuclear reaction of the furnace is increased, the temperature of the coolant from the outlet of the fuel assembly 10 rises, and eventually the boiling point Tvap of the substance a for transport is increased.
When it is substantially equal to or exceeds, the carrier substance a is vaporized and its volume is expanded rapidly, so that the pressure in the boiling-liquefying chamber 1 is rapidly increased and the liquid neutron absorption b is transferred to the cylindrical chamber 2. Send by pressure. In this way, the reaction of the furnace is suppressed by the liquid neutron absorber b in the cylindrical chamber 2. This state is shown in FIG. 1B. The liquid neutron absorber b in the cylindrical chamber 2 is filled up to the height of the nuclear fuel 11 loading portion in the state of FIG. 1C in which all of the carrier substance a is vaporized. When the nuclear reaction is suppressed by the liquid neutron absorber b in the cylindrical chamber 2 and the coolant temperature from the coolant outlet of the fuel assembly 10 falls below the liquefaction point of the carrier substance a, the carrier substance a is liquefied. However, since the pressure in the boiling-liquefying chamber 1 drops sharply, the liquid neutron absorber b in the cylindrical chamber 2 is returned to the boiling-liquefying chamber 1, and as a result, the nuclear reaction of the reactor becomes active again. become. If the saturated vapor pressure of the above-mentioned carrier substance a is abruptly changed at the boiling point, the response performance of the operation is excellent and it is advantageous for scrum, but it is not suitable for output adjustment and the output of the furnace vibrates. Will be done. On the other hand, if the saturated vapor pressure of the substance a for transportation changes relatively gently near the boiling point, fluctuations in the output of the furnace can be reduced and output adjustment is possible, but the rapid temperature change of the furnace The response to the rise is slow and the scrum function is reduced. Therefore, adjusting the power output of the reactor
Alternatively, it is necessary to select an appropriate substance a for transportation depending on the purpose of use, such as exclusive use for scrum. In FIGS. 1A to 1C, the cylindrical chamber 2 is opened to the gas space in the core through the communication pipe 4, but the present invention is not limited to this, and the cylindrical chamber 2 is not limited to this. It can also be closed. A cylindrical chamber 2 corresponding to FIGS. 1A to 1C when the cylindrical chamber 2 is of an open type.
The case of the closed type is shown in FIGS. 2A to 2C. An expansion / absorption chamber 5 is continuously provided below the cylindrical chamber 2, and the cylindrical chamber 2 and the expansion / absorption chamber 5 are connected by a pipe 6. Further, an inert gas such as argon is sealed inside. In this way, even if the internal pressure of the cylindrical chamber 2 is increased, the escape pressure is relieved to the expansion absorption chamber 5 through the pipe 6, so that there is no problem in receiving the liquid neutron absorber b. The height of the tube 6 is set higher than the height of the portion where the nuclear fuel 11 is loaded so that the liquid neutron absorber b is not placed in the expansion absorption chamber 5. As shown in FIG. 2A, in order to hold the liquid neutron absorber b in the boiling-liquefying chamber 1, the argon (A) enclosed in the volumes V _{B, C} of the cylindrical chamber 2 and the expansion absorbing chamber 5 ( The pressure P _{B, C at the} number of moles n _AR and the temperature T _{B, C} may be balanced with the pressure due to the head h of the liquid neutron absorber b (density ρ). At that time, since the relational expression P _{B, C} · V _{B, C} = n _AR · R · T _{B, C} P _{B, C} = h · ρ holds, n _AR = h · ρ · V _{B, C} / R -T _{B, C} mol of argon may be enclosed. The value of V _{B, C} , h depends on the chamber shape. Further, as shown in FIG. 2C, in order to hold the liquid neutron absorber b in the cylindrical chamber 2, vaporization of the carrier substance a (mol number n _a , temperature T _{B, C} ) in the boiling-liquefying chamber 1 is performed. The internal pressure due to the above may be balanced with the increase in the internal pressure of the cylindrical chamber 2 (volume V _B ) and the expansion absorption chamber 5 (volume V _C ) due to the movement of the liquid neutron absorber b. Assuming that the volume of the moving liquid neutron absorber b is V _b and the volume when the transporting substance a is completely vaporized is V _a , V _a = V _b , and at that time, the relational expression P _{B, C} ( V _{B, C} −V _b ) = n _AR RT _{B, C} P _A · V _b = n _a · R · T _A P _{B, C} = P _A holds, so V _{B, C} = V _b n _AR T The values of _{B, C} / n _a T _A temperature T _A , T _{B, C} are determined by the operating conditions of the reactor, and the value of V _b is determined by the volume of the liquid neutron absorber b required to shut down the reactor, If V _{B, C} is determined in advance, n _AR is determined.
Expansion volume V _C of the absorption chamber 5, V _B, can be determined by appropriately distributing the _C -V _b in both chambers 2 and 5. FIG. 3 shows a specific structure of the boiling-liquefying chamber 1 in FIG. 2A. That is, the boiling-liquefying chamber 1 provided at the upper end of the cylindrical chamber 2 is formed with a plurality of overhanging chamber portions 1a that overhang in the radial direction.
During the period 1a, the high temperature coolant flowing out from the coolant outlet of the fuel assembly 10 passes. Therefore, the carrier substance a and the liquid neutron absorber b contained in each of the overhanging chambers 1a can respond to the temperature of the high temperature coolant from the fuel assembly 10 as quickly as possible, and evaporate by boiling. The transported substance a is not liquefied again before the output of the furnace is reduced.

【The invention's effect】

As can be seen from the above description, the present invention is boiling-liquefaction of the carrier substance by the coolant outlet temperature of the fuel assembly in response to the core temperature, liquid neutron absorber absorption by the volume change of the carrier substance at that time Since the body is moved so as to be introduced into the core or discharged to the outside of the core, there is no need for external control as in the conventional case, and a mechanically movable part such as a control rod drive mechanism is not required. It can be eliminated, scram is possible even in the case of a large-scale earthquake in which the conventional control rod guide tube is significantly curved, and the risk of scrum failure is extremely small. In addition, even if the outlet temperature of the coolant rises momentarily and temporarily, and even if the liquid neutron absorber is temporarily fed into the core, the liquid neutron absorption immediately decreases as the reactor output decreases and the temperature drops. Since the body is discharged to the outside of the core, the power of the furnace rises again and naturally returns to the original steady state, and even if it operates, it has practically no effect on operation. Furthermore, when there is no fear of malfunction, the operating temperature can be set low, which contributes to improving the reliability of the operating response in the event of an abnormality. The device of the present invention is suitable for being of a sealed type. Unlike the open type, the closed type has the advantage that there is no entry and exit of substances from the outside, it operates only at temperature without being affected by the external pressure, and the operating temperature is always constant. In the case of the closed type, the expansion and absorption chamber is connected to the cylindrical chamber, and a pipe for connecting the cylindrical chamber and the expansion and absorption chamber is provided.
Since it is possible to prevent the pressure in the cylindrical chamber 2 from increasing with the boiling of water, the boiling-liquefying chamber 1 to the cylindrical chamber 2
It is possible to prevent the delivery efficiency of the liquid neutron absorber b to be not disturbed.

[Brief description of drawings]

1A to 1C are explanatory views of a first embodiment of the apparatus according to the present invention, FIGS. 2A to 2C are sectional views of the apparatus, and FIG. 3 is an explanatory view of a second embodiment of the apparatus according to the present invention. is there. 1 ... Boiling-liquefaction chamber, 2 ... Cylindrical chamber, 3
...... Communication pipe, 4 ... Communication pipe, 5 ... Expansion absorption chamber, 6 ... Pipe, 10 ... Fuel assembly, 11 ... Nuclear fuel, a ...
... Transport material, b ... Liquid neutron absorber.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-284289 (JP, A) JP 57-45489 (JP, A) JP 50-36897 (JP, A) Practical application Sho 57- 31700 (JP, U)

Claims (2)

[Claims] 1. A carrier material having a boiling point slightly higher than the steady-state operating temperature of the furnace, and a liquid neutron absorption which is liquid at a temperature in the steady-state operating state of the furnace and has a boiling point sufficiently higher than that of the carrier material. Boiling containing the body-a liquefying chamber is arranged in the vicinity of the coolant outlet of the fuel assembly, and a cylindrical chamber is arranged at a position in the core surrounded by a plurality of fuel assemblies, and the boiling- A self-actuating nuclear reactor control device, wherein the liquefaction chamber and the tubular chamber are connected by inserting a moving pipe attached to the bottom of the boiling-liquefaction chamber into the tubular chamber. 2. The cylindrical chamber is hermetically sealed, an expansion absorbing chamber is connected to the cylindrical chamber, and a pipe is provided for connecting the cylindrical chamber and the expansion absorbing chamber, and an inert gas is sealed inside. The self-actuating nuclear reactor control device according to claim 1.