CN111933312B

CN111933312B - Device for automatically controlling reactivity of nuclear reactor

Info

Publication number: CN111933312B
Application number: CN202010789572.8A
Authority: CN
Inventors: 陈其昌; 赵金坤; 卑华; 汤春桃
Original assignee: Shanghai Nuclear Engineering Research and Design Institute Co Ltd
Current assignee: Shanghai Nuclear Engineering Research and Design Institute Co Ltd
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2022-12-02
Anticipated expiration: 2040-08-07
Also published as: CN111933312A

Abstract

The invention aims to disclose a device for automatically controlling the reactivity of a nuclear reactor, which comprises a totally-enclosed high-temperature resistant pipe shell with a certain length, wherein a lithium vapor cavity and an inert gas cavity are respectively arranged at two ends in the totally-enclosed high-temperature resistant pipe shell, and liquid metal lithium is arranged between the lithium vapor cavity and the inert gas cavity; the reactivity can be automatically and passively introduced or reduced according to the temperature change of the reactor core without controlling a driving mechanism, so that the automatic control of the reactivity of the reactor is realized; the volume is small, the structure is simple, and the required liquid metal lithium loading is less; the volume change caused by the vaporization of the metal lithium is large, the reactivity introduction speed is high, and the neutron absorber displacement and the reactivity negative feedback are large; the lithium melting furnace can work at different temperatures, and the initial temperature point of vaporization and expansion of liquid lithium is controlled through pre-charging pressure regulation; the temperature reactivity negative feedback is adjustable in size, and the displacement of the liquid lithium in the reactor core in unit temperature change can be controlled through the volume of the initial air cavity.

Description

Device for automatically controlling reactivity of nuclear reactor

Technical Field

The present invention relates to an automatic control device, in particular to a device for automatically controlling the reactivity of a nuclear reactor.

Background

The reactivity is a core parameter related to whether the nuclear reactor can safely operate, and the large or small reactivity is directly related to the core arrangement, fuel consumption and the like, and is also closely related to the reactor temperature, the coolant density and the like. Generally, the operating temperature, including the fuel temperature, the coolant temperature, and the like, which most affects the reactivity of a specific core, and the amount of reactivity change caused by a unit temperature change is referred to as a reactivity temperature coefficient. In order to ensure safe operation of the reactor, the reactor must be designed to ensure that the core has a negative and sufficiently large temperature reactivity coefficient, i.e., negative reactivity feedback can be introduced as the temperature increases, thereby maintaining core power stability.

For some reactors, such as gas or liquid metal space reactors with high enrichment fuel, the fuel doppler and the temperature (density) reactivity of the coolant are not obvious or even absent, which makes the operation of the reactor difficult to guarantee. Therefore, other reactivity control mechanisms need to be considered in the design, so that the reactor core has negative temperature reactivity feedback, the negative reactivity is automatically introduced when the power and the temperature of the reactor core are increased, and the power and the temperature of the reactor core are maintained to be stable.

Therefore, there is a particular need for an apparatus for automatic control of the reactivity of a nuclear reactor that solves the above-mentioned existing problems.

Disclosure of Invention

The invention aims to provide a device for automatically controlling the reactivity of a nuclear reactor, which aims at the defects of the prior art and provides negative feedback of temperature reactivity for the reactor, so that negative reactivity is automatically introduced when the temperature of a reactor core rises, and positive reactivity is automatically introduced when the temperature of the reactor core falls, thereby ensuring the operation safety of the reactor.

The technical problem solved by the invention can be realized by adopting the following technical scheme:

the device for automatically controlling the reactivity of the nuclear reactor is characterized by comprising a totally-closed high-temperature-resistant pipe shell with a certain length, wherein a lithium steam cavity and an inert gas cavity are respectively arranged at two ends in the totally-closed high-temperature-resistant pipe shell, and liquid metal lithium is arranged between the lithium steam cavity and the inert gas cavity.

In one embodiment of the invention, the totally-enclosed high temperature resistant pipe shell is made of refractory alloy or ceramic material.

In one embodiment of the invention, the totally-enclosed high-temperature resistant pipe shell is inserted into a reactor core, when the temperature of the reactor rises, part of liquid metal lithium is vaporized, the remaining liquid metal lithium is pushed to move in the totally-enclosed high-temperature resistant pipe shell through expansion of a lithium vapor cavity, and the metal lithium is used as a neutron absorption material and realizes reaction control through entering or moving out of the reactor core.

In one embodiment of the invention, the inert gas air chamber maintains pressure balance with lithium vapor through volume change of the inert gas air chamber, liquid metal lithium moves in the totally-enclosed high-temperature-resistant tube shell under the combined action, and reactivity automatic control of different reactors is realized through adjustment of reserved volume and pre-charging pressure.

In one embodiment of the invention, a multi-layer porous liquid absorption core is arranged in the totally-enclosed high-temperature resistant pipe shell and is used for absorbing liquid metal lithium in the pipe, controlling the distribution of the liquid metal lithium in the pipe, realizing gas-liquid separation and maintaining a gas space.

Compared with the prior art, the device for automatically controlling the reactivity of the nuclear reactor does not need to control a driving mechanism, can fully automatically and passively introduce or reduce the reactivity according to the temperature change of the reactor core, and realizes the automatic control of the reactivity of the reactor; the volume is small, the structure is simple, and the required liquid metal lithium loading is less; the volume change caused by the vaporization of the metal lithium is large, the reactivity introduction speed is high, and the neutron absorber displacement and the reactivity negative feedback are large; the lithium melting furnace can work at different temperatures, and the initial temperature point of vaporization and expansion of liquid lithium is controlled through pre-charging pressure regulation; the temperature response negative feedback is adjustable in size, and the displacement of the liquid lithium in the reactor core per unit temperature change can be controlled through the volume of the initial air cavity, so that the aim of the invention is fulfilled.

The features of the present invention will be apparent from the accompanying drawings and from the detailed description of the preferred embodiments which follows.

Drawings

FIG. 1 is a schematic diagram of the structure of an apparatus for automatic control of the reactivity of a nuclear reactor according to the present invention;

FIG. 2 is a schematic diagram of the automatic control of the apparatus for automatic control of nuclear reactor reactivity according to the present invention;

fig. 3 is a graph illustrating the saturation pressure of lithium according to the present invention as a function of temperature.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained below by combining the specific drawings.

Examples

As shown in fig. 1 to 3, the apparatus for automatically controlling the reactivity of a nuclear reactor according to the present invention includes a totally-enclosed high temperature resistant pipe shell 4 having a certain length, a lithium vapor chamber 1 and an inert gas chamber 3 are respectively disposed at both ends of the totally-enclosed high temperature resistant pipe shell 4, and liquid metal lithium 2 is disposed between the lithium vapor chamber 1 and the inert gas chamber 3.

In this embodiment, the totally-enclosed high temperature resistant tube shell 4 is a totally-enclosed structure, and provides an enclosed space for the lithium vapor chamber 1 and the inert gas chamber 3 of the internal liquid neutron absorber (liquid metal lithium 2), and the totally-enclosed high temperature resistant tube shell 4 is made of a high temperature resistant and radiation resistant structural material (such as a refractory alloy or a ceramic material), and can keep the structural integrity in the reactor core 10.

In this embodiment, a plurality of layers of porous liquid absorption cores 5 are arranged in the totally-enclosed high-temperature resistant pipe shell 4, liquid metal lithium 2 in the totally-enclosed high-temperature resistant pipe shell 4 is absorbed by capillary force, the distribution of the liquid metal lithium 2 in the totally-enclosed high-temperature resistant pipe shell 4 is controlled, when the temperature of a reactor coolant outside the totally-enclosed high-temperature resistant pipe shell 4 rises, liquid in the porous liquid absorption cores 5 is vaporized, meanwhile, the porous liquid absorption cores 5 can absorb the liquid metal lithium 2 for supplement, so that vapor-liquid separation is realized, and a gas space is maintained.

One end in the totally-enclosed high-temperature resistant pipe shell 4 is filled with a certain amount of liquid metal lithium 2, wherein the lithium element can be controlled to a certain degree according to the reactivity (Li) ⁶ ) Enriched, liquid metal lithium 2 acts as a neutron absorbing material that controls the core reactivity within the core. The liquid metal lithium 2 realizes the movement of a liquid column in the reactor core through partial vaporization expansion, thereby realizing the automatic control of the reactivity; the other end in the totally-enclosed high-temperature resistant pipe shell 4 is an inert gas air cavity 3, the pressure of the inert gas air cavity 3 can be controlled in advance according to the reactivity control requirement of a reactor where the device is located, and when the hot-end liquid lithium is vaporized and expanded, the inert gas air cavity 3 is compressed, so that a moving space is provided for the liquid neutron absorber.

When the device for automatically controlling the reactivity of the nuclear reactor is used, the device is integrally inserted into a reactor core 10, wherein one end, which is reserved with liquid metal lithium 2, is positioned at a reactor coolant outlet 12 (hot end), and the other end, which is reserved with an inert gas air cavity 3, is positioned at a coolant inlet 11 (cold end);

when the temperature of the reactor core coolant outlet is lower, the saturation pressure of corresponding lithium is also lower, and when the temperature of the reactor core coolant outlet is lower than the pressure of the air cavity in the pipe, the liquid metal lithium in the pipe is kept in a liquid state, most of the liquid metal lithium is positioned outside the reactor core active area, and the reactor core reactivity is maintained stably;

when the temperature of the core coolant outlet is increased, the saturation pressure of the corresponding lithium is correspondingly increased (as shown in fig. 3), when the saturation pressure is higher than the pressure of the air cavity in the pipe, the liquid lithium starts to vaporize and expand, the liquid lithium is pushed to enter the core active area, and the core introduces negative reactivity because the liquid lithium has a larger neutron absorption cross section;

along with the vaporization of the liquid lithium, the lithium vapor space is continuously expanded, the inert gas air cavity is continuously compressed, the pressure in the tube is continuously increased, when the pressure in the tube is equal to the lithium vapor saturation pressure corresponding to the temperature of the hot end, the vaporization of the liquid lithium is stopped, the liquid lithium is maintained stable at the position in the reactor core, and the reactive introduction of the reactor core is stopped;

when the temperature of the reactor core coolant outlet is reduced, the saturation pressure of corresponding lithium is correspondingly reduced, when the saturation pressure of the reactor core coolant outlet is smaller than the pressure of an air cavity in a pipe, lithium vapor is condensed and liquefied, the inert gas air cavity expands to push liquid lithium to move out of the active region of the reactor core, and the reactor core introduces positive reactivity;

with the condensation of lithium steam, the lithium steam space is continuously contracted, the inert gas air cavity is continuously expanded, the pressure in the pipe is continuously reduced, when the pressure in the pipe is equal to the lithium steam saturation pressure corresponding to the temperature of the hot end, the condensation of the lithium steam is stopped, the liquid lithium is stably maintained at the position in the reactor core, and the reactive introduction of the reactor core is stopped;

according to the relation that the lithium saturation pressure changes along with the temperature (figure 3), the device can control the initial temperature of the automatic reactivity introduction by controlling the pressure of the initial inert gas cavity, and simultaneously can control the displacement of the neutron absorber in the reactor core by unit temperature change through the volume of the inert gas cavity, thereby controlling the reactivity introduction rate.

The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined by the appended claims and their equivalents.

Claims

1. The device for automatically controlling the reactivity of the nuclear reactor is characterized by comprising a totally-closed high-temperature-resistant pipe shell with a certain length, wherein a lithium steam cavity and an inert gas cavity are respectively arranged at two ends in the totally-closed high-temperature-resistant pipe shell, and liquid metal lithium is arranged between the lithium steam cavity and the inert gas cavity.

2. The apparatus of claim 1 wherein the totally enclosed refractory vessel is made of refractory alloy or ceramic material.

3. The apparatus of claim 1, wherein the totally enclosed refractory tube shell is inserted into a reactor core, and when the reactor temperature rises, part of the liquid metal lithium is vaporized, and the remaining liquid metal lithium is pushed to move in the totally enclosed refractory tube shell by expansion of the lithium vapor cavity, and the metal lithium is used as a neutron absorbing material to realize reaction control by entering or removing from the reactor core.

4. The apparatus of claim 1, wherein the inert gas chamber maintains a pressure balance with lithium vapor by its volume change, and the inert gas chamber and the lithium vapor together move liquid metal lithium in the totally enclosed refractory tube shell, and the reactivity of different reactors can be automatically controlled by adjusting the reserved volume and the pre-charging pressure.

5. The apparatus of claim 1, wherein the totally enclosed refractory tube housing has a plurality of porous wicks disposed therein for adsorbing liquid lithium metal in the tube, controlling the distribution of the liquid lithium metal in the tube, achieving vapor-liquid separation, and maintaining a gas space.