JP2718855B2 - Nuclear fuel channel and its own safe water cooled tube reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear fission reactor, and more particularly, to a nuclear fuel channel and a nuclear fuel channel which can be used in a nuclear power plant, a district heating reactor, a combined heat reactor and a research reactor. It relates to the intrinsically safe water cooled tube reactor used.

[0002]

2. Description of the Related Art In general, a nuclear reactor is a device that can control the fission of uranium and plutonium in a controllable state and can use the generated energy. , A district heating reactor and a research reactor. Reactor types include a water-cooled reactor (Water-Cooled Reactor) and a gas-cooled reactor (Gas-Cooled R).
eactor), Liquid Metal-Cooled Reac
Water-cooled reactors are among the most technologically developed of these, and are currently the mainstream of nuclear power in the world. Water-cooled reactors use water as a coolant (Coolant) to cool nuclear fuel that causes fission, and can be used as a pressurized water reactor (Pressurized Water Reactor) or pressurized heavy water reactor (Pr
essurized Heavy Water Reactor, Boiling Water Reactor
Water Reactor).

[0003] Unlike nuclear power, thermal power, etc., nuclear fission in a nuclear reactor generates radioactive materials and the like, so safety issues are important. During normal operation, workers or nearby areas receive very little radiation from the reactor, so it does not harm health. However, if an unexpected and serious accident occurs and sufficient action is not taken,
Causes serious damage to humans and the environment. Therefore, each reactor type must be designed to minimize the possibility of external leakage of radioactive material and to minimize the damage in the event of a leakage accident.

[0004] The nuclear reactor is equipped with various kinds of protective safety devices, and the reactor is automatically shut down in the event of an accident that may cause the external leakage of radioactive materials or when a sign thereof is observed. However, in a nuclear reactor, heat (residual heat or decay heat) due to radioactive decay of fission products and the like is continuously generated, and if this is not cooled efficiently, a serious accident may occur in which the core melts. it can. Therefore, in water-cooled reactors, the Emergency Core Cooling System,
If the normal cooling system does not operate, emergency cooling water is supplied to the core to remove decay heat.

[0005]

Existing nuclear power plants are rated as having a lower risk to humans and the environment when compared to other means of power generation (coal or oil-fired power plants). However, the public's concern about nuclear safety is increasing, and the concept of the need for innovative improvements in nuclear safety in the world's nuclear community is widespread. The new safety reactor has been developed based on this concept. The features of the new safety reactor are different from existing reactors, which mainly rely on driven equipment (equipment that requires driving force) such as pumps and valves to operate the safety equipment of the reactor. It is said that the principle of nature (driven safety) is mainly used. The new safety reactors have been evaluated as significantly improving the safety of existing reactors.

A circuit-type water-cooled reactor (Loop-typ) that can make the most of the technology that has already been proven among the new safety reactors
e Water-Cooled Reactor). It is expected that the reactors belonging to this system can greatly improve safety while simplifying the system.However, for efficient core injection of emergency core cooling water, depressurization using driven equipment is required. Requires a system (Depressurization System). Therefore, in order to make the safety closer to the absolute safety, it is necessary to develop a reactor that does not require the emergency core cooling device itself.

[0007]

SUMMARY OF THE INVENTION The present invention separates the moderator and the coolant so that the nuclear fuel channel in the form of a tube is immersed in a large volume moderator so that the coolant is maintained during normal operation. A nuclear fuel channel configured to remove fission energy and prevent the decay heat from being transferred to the moderator to cause an excessive rise in the temperature of the nuclear fuel channel if a coolant loss accident or normal cooling by the coolant is not possible. And a unique safety water-cooled tube reactor utilizing the same.

[0008]

The present invention adopts a uniquely designed tubular core, which allows the metal nuclear fuel matrix or Zircaloy matrix not only to function as a heat conductor during normal operation and accidents, but also to reduce decay heat immediately after a coolant loss accident. It functions as an absorber, and the moderator is cooled by forced circulation by a pump during normal operation, but the decay heat at the time of the accident is transferred to the moderator tank located at the top of the reactor in the containment vessel (Containment). The atmosphere in the containment vessel (Containment Atmosphe) by natural circulation of air and opening of the moderator tank safety valve
re) and is driven and cooled by the containment vessel. Further, according to the intrinsically safe water-cooled tube reactor of the present invention, there is no need to provide a separate emergency core cooling device, no driven equipment is used to remove decay heat after an accident, and heat conduction and heat are eliminated. An inherently safe furnace can be obtained which depends entirely on the driven safety, such as radiation, natural circulation, pressure and the like.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. 1, 2 and 3 are cross-sectional views of a nuclear fuel channel according to the present invention.
2 shows a cross section of a nuclear fuel channel using a metal nuclear fuel matrix (FIG. 1) and a nuclear fuel channel using a Zircaloy matrix (FIGS. 2 and 3), which are main parts of Safe and Simple Tube Reactor (ISSTER). .

In the case of a nuclear fuel channel 1 using a metal nuclear fuel matrix shown in FIG. 1, a nuclear fuel matrix 4 is incorporated with a gap of several millimeters in a nuclear fuel channel tube 2 of a long circular tube made of a zirconium alloy. I have. Here, the metal nuclear fuel matrix 4
Is formed by stacking a plurality of short-length, substantially columnar shaped pieces of metal uranium, metal plutonium, metal thorium, etc. in the nuclear fuel channel tube 2. The space 3 between the nuclear fuel channel tube 2 and the metal nuclear fuel matrix 4 is filled with helium (He) gas or the like.
Coolant holes 5 are formed in the metal nuclear fuel matrix 4 in a distributed manner, and a coolant hole tube 6 made of Zircaloy prevents direct contact between the metal fuel and the coolant. A burnable poison or a core measuring device can be inserted into the hole 5A located at the center.

In the case of the nuclear fuel channels 10 and 20 utilizing the Zircaloy matrix shown in FIGS. 2 and 3, the moderator is located only on the outside of the nuclear fuel channel 10 (FIG. 2) and on both the inner and outer sides. It can be roughly classified into two types of annular shapes (FIG. 3).
First, a cylindrical Zircaloy nuclear fuel matrix 14 is formed by integrally molding an alloy of nuclear fuel and Zircaloy, and has several holes 11A, 11B, 11C.
Nuclear fuel (uranium dioxide) is put in some holes 11A, and coolant (Cool) is put in the remaining holes 11B (coolant holes).
(Lant) flows. If necessary, an in-core measuring device (In-Core Instrument)
mentation) or a burnable poison (Burn)
A hole 11 </ b> C for inserting an Able Poison can be placed in the center of the nuclear fuel matrix 14.
At this time, the gap 13 formed between the nuclear fuel channel tube 12 and the nuclear fuel matrix 14 also contains helium (H
e) Gas or the like is filled.

The structure of the annular tubular nuclear fuel channel 20 shown in FIG.
Numeral 0 denotes a zircaloy nuclear fuel matrix 24 in which an alloy of nuclear fuel and zircaloy is integrally formed into a substantially cylindrical shape. A plurality of holes 25 and 26 are provided. Nuclear fuel (uranium dioxide) is put in some holes 25, and the remaining holes are provided. Coolant (Cool) 26
ant) flows, and further, the inner nuclear fuel tube 2 is provided inside the Zircaloy nuclear fuel matrix 24.
2A, an outer nuclear fuel tube 22B is disposed concentrically on the outer side, and a gap 23 between the Zircaloy nuclear fuel matrix 24 and the inner and outer nuclear fuel tubes 22A, 22B is filled with helium (He) gas or the like. In such an annular nuclear fuel channel 20, the moderator is located inside the inner nuclear fuel tube 22A and outside the outer nuclear fuel tube 22B (described later in detail in FIG. 4).

The nuclear fuel channels 1, 10 or 20 are arranged in a large cylindrical reactor vessel 40 as shown in FIG. 4, and are immersed in a moderator 41 having a lower pressure than the coolant. Here, the number of the nuclear fuel channels 1, 10 or 20 varies depending on the power of the nuclear reactor. The arrangement of the nuclear fuel channels 1, 10 or 20 is a square arrangement (Square).
Array), but other arrangements are possible in some cases. A moderator inlet nozzle 42 and an outlet nozzle 43 are located at a lower portion and an upper portion of the reactor vessel 40, respectively. Here, the combination of the three ways as moderator and coolant _{(D 2} O coolant -D ₂ O moderator, _{H 2} O coolant -D ₂ O moderator, _{H 2}
O coolant -H ₂ O moderator) is possible. From the physical characteristics of the nuclear reactor, it is determined that it is desirable to use D ₂ O as the moderator. As the use of heavy water is increased, the reactivity feedback is better and the enrichment of nuclear fuel can be reduced, but an auxiliary system for heavy water treatment must be added.

FIG. 5 shows a configuration diagram of a nuclear steam supply system (NSSS) of a nuclear power plant utilizing the nuclear reactor of the present invention. That is, a nuclear steam supply system is realized by one nuclear reactor 50, one pressurizer 51, and a coolant circuit whose number can be changed depending on the output. Each coolant circuit is a steam generator 5
2. It is composed of a coolant pump 53 and piping (high-temperature pipe and low-temperature pipe) 54. A circuit 55 for circulating the moderator is disposed between the reactor 50 and a moderator tank 56 (located in the containment) above the reactor 50. Here, the reactor 50 is located horizontally (the cylindrical reactor vessel 4 placed horizontally).
0, nuclear fuel channels and the like 1, 10 and 20 can be arranged horizontally, and the nuclear fuel channels and the like 1, 10, and 20 can be arranged in a vertical position (a vertically-standing cylindrical reactor vessel 40).
20 can be arranged vertically).

Most of the energy generated in nuclear fuel by nuclear fission during normal operation of the nuclear reactor of the present invention is transferred to the coolant by heat conduction. The coolant produces steam in the steam generator 52, which turns the turbine to produce electricity. For this purpose, the coolant must be at a high pressure. However, as in the case of existing pressurized heavy water reactors or pressurized light water reactors,
0 to 155 atm is suitable. The coolant pressure boundary in the reactor is the coolant bore tube 6 (FIG. 1) for the nuclear fuel channel 1 (FIG. 1) using a metal nuclear fuel matrix, and for the nuclear fuel channels 10, 20 using a Zircaloy matrix. The Zircaloy nuclear fuel matrices 14, 24 themselves, but the nuclear fuel channel tubes 12, 22A, 22B are also designed for coolant pressure in preparation for these cracks or breaks. In this case, the nuclear fuel matrices 4, 14,
Even if 24 local damages occur, the operation can be continued without stopping the reactor. On the other hand, the pressure of the moderator is maintained at atmospheric pressure or a slightly higher pressure.

Most of the fission energy during normal operation is cooled by the coolant, but most of the neutron-generated energy and a significant portion of the gamma-ray energy is transferred to the moderator. Each nuclear fuel matrix 4, 14, 24
Heat can also be transferred to the moderator through the gaps (Gap) 3, 13, 23 between the channel tubes 2, 12, 22A, 22B, but the amount is kept very small. As a result, about 5% of the total fission energy is transferred to the moderator, which can be boiled unless it is properly cooled.
Occurs, and the neutron moderating ability is rapidly reduced.

Therefore, the present invention adopts a unique moderator circulation circuit, whereby the low-temperature moderator in the moderator tank 56 is injected into the lower part of the reactor, heated in the reactor, and then further cooled in the moderator tank. Ascended to 56 and mixed directly. Such moderator circulation is maintained by a moderator circulation pump 57 to prevent moderator boiling in the reactor. The moderator in the moderator tank 56 flows into the moderator cooling heat exchanger 59 through the device cooling water inlet 60 by a separate circuit, and is cooled by the device cooling water flowing out from the device cooling water outlet 61. Is the existing CANDU (Ca
nadian Deuterium Uranium).

For any reason, the reactor may be subject to transient conditions, such as changes in power or coolant flow, or loss of coolant. Among them, the most extreme accident from the viewpoint of safety is a state in which cooling with a coolant is completely impossible. Therefore, in the present invention, a design in which decay heat is cooled without the operation of a special driven device even in the event of an accident in which the coolant is completely lost has been devised so that no serious accident will occur in any case.

The response of ISSTER in the event of a complete loss of coolant is as follows. First, when a coolant loss accident occurs, control rod insertion or coolant non-reactivity coefficient (Negative
Reactivity Coefficient) shuts down the reactor,
Reactor power immediately drops to decay heat level. However, since the cooling by the coolant is not performed, the amount of heat transferred to the moderator gradually increases while the temperature of the nuclear fuel matrix 4, 14, 24 gradually increases. Here, the decay heat generated in the nuclear fuel is transferred to the metal nuclear fuel matrix 4 (FIG. 1) or the Zircaloy nuclear fuel matrices 14, 24 (FIGS. 2 and 3), and the nuclear fuel matrices 4, 14, 2
4, heat radiation and heat conduction between the channel tubes 2, 12, 22A and 22B (by a filling gas such as He), heat conduction to the channel tubes 2, 12, 22A and 22B,
The heat is transferred to the moderator in the order of convective heat transfer or boiling heat transfer between the channel tubes 2, 12, 22A, 22B and the moderator. The temperature of the nuclear fuel matrix 4, 14, 24 rises until the generated decay heat is in equilibrium with the amount of heat transferred to the moderator, after which it gradually falls due to the decrease in decay heat. The reactor according to the invention is designed in such a way that the temperature of the nuclear fuel matrix 4, 14, 24 does not exceed the tolerances anywhere.

In the event of a coolant loss accident, the moderator circulation pump 57
Operates normally and the cooling through the moderator cooling heat exchanger 59 is performed normally, the decay heat transmitted to the moderator by the stepwise forced convection heat transfer is performed similarly to the moderator cooling in the normal operation. Cooled. However, in the present invention, all pumps 5
Even if the operation is stopped, the decay heat is safely removed by natural circulation of the moderator. The operation principle will be described below.

When the moderator circulating pump 57 stops, the moderator circulating capacity decreases, and therefore, nucleate boiling (Nu) occurs on the wall surfaces of the nuclear fuel channel tubes 2, 12, 22A and 22B.
cleate Boiling) occurs. Therefore, the moderator extracted to the upper part of the reactor is steam in which steam and liquid are mixed,
This water vapor condenses in the moderator tank 56 while being mixed with lower temperature water. The density difference between the moderator outlet 43 side and the inlet 42 side immediately forms a two-phase natural circulation (Two-Phase Natural Circulation) flow in the moderator circulation circuit 55. As time passes, the decay heat is continuously transmitted to the moderator, but the moderator cooling is not performed.
Of water reaches a saturated state. After this point, saturated water enters the moderator inlet nozzle 42 of the reactor, and the outlet nozzle 43 maintains a natural circulation of saturated water-steam multiphase flow, and the nuclear fuel channel tubes 2, 12. , 22A and 22B, the saturated boiling of the moderator removes the decay heat.

After the moderator reaches a saturated state, the steam continuously generated by the decay heat increases the pressure in the moderator system. Therefore, a safety valve 58 or the like is provided at the upper part of the moderator tank 56, and when the moderator pressure reaches a certain limit value, it is naturally released, and water vapor is released from the atmosphere (Cont.
ainment Atmosphere). Thus, the decay heat is transmitted to the atmosphere of the containment vessel, and the atmosphere of the containment vessel is cooled by the driven cooling system of the containment vessel. Therefore, if the capacity of the moderator tank 56 is determined to be sufficiently large based on the amount of water that the decay heat can vaporize, one week or three weeks
The reactor will be safely cooled without the operation of driven equipment or operator intervention for more than a day. Thereafter, supplying cooling water to the moderator tank 56 through an appropriate route requires no additional measures to keep the reactor safe.

The present invention ensures absolute safety against a loss of coolant accident by separating coolant and moderator, employing a matrix-shaped nuclear fuel channel and a unique moderator system. Separation of the coolant and the moderator prevents simultaneous loss of the coolant and the moderator, so that the moderator pressure can be maintained at the atmospheric pressure level. The low moderator system pressure increases the reliability of the control rod device inserted on the moderator side and facilitates the design of other auxiliary systems. The metal nuclear fuel or zircaloy matrix in the nuclear fuel channels 1, 10, 20 is a thermal conductor that transfers fission energy to the coolant during normal operation. In the case of a loss of coolant accident, the reactor functions as a heat absorber that accumulates decay heat immediately after the reactor shuts down, and then acts as a heat conductor that promotes the decay heat transfer to the moderator, resulting in nuclear fuel. Prevents excessive channel temperature rise. The moderator circulation circuit 55 associated with the moderator tank 56 at the upper part of the reactor and the safety valve 58 at the upper part of the moderator tank 56 directly transmit the decay heat after the accident to the atmosphere of the containment vessel, and are operated by the driven cooling system of the containment vessel. Cooling allows safe cooling of the core without using an emergency core cooling device.

[0024]

The inherently safe water-cooled tube reactor of the present invention has an inherent safety that does not require an "emergency core cooling device" which is the most important design of a conventional water-cooled reactor. In addition, the safety of the reactor after the accident was determined by heat conduction, heat radiation,
By eliminating the possibility of failure of the cooling operation in an emergency only by relying on passive natural principles such as natural convection and pressure,
Compared to conventional reactors or new safety reactors currently under study, the safety of the reactor can be greatly improved.

Also, in the intrinsically safe water-cooled tube reactor of the present invention, the elimination of the emergency core cooling device greatly simplifies the reactor system. The simplification of the system directly leads to the improvement of economy. In addition, the design of reactors other than the reactor and moderator system is expected to be commercialized as soon as possible by using the design technology of conventional light water reactors as it is. It is simpler than a furnace or the like. That is, according to the nuclear reactor of the present invention, only the heat removal capability for a single nuclear fuel channel and the proper operation of the coolant circulation circuit are important verification items. In the practical application stage, various selections and applications are possible, that is, various types of reactor systems can be designed, including material changes of coolant and moderator, and nuclear power plants and district heating systems can be designed. It can be applied to various applications such as reactors, combined heat and power reactors, and research reactors.

[Brief description of the drawings]

FIG. 1 is a sectional view of a nuclear fuel channel according to the present invention.

FIG. 2 is a sectional view of a nuclear fuel channel according to the present invention.

FIG. 3 is a sectional view of a nuclear fuel channel according to the present invention.

FIG. 4 is a view showing an example of a nuclear fuel channel arrangement in a reactor vessel.

FIG. 5 is a diagram of a nuclear steam supply system of a nuclear power plant using the nuclear reactor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nuclear fuel channel 2 Nuclear fuel channel tube 3 Gap 4 Metal nuclear fuel matrix 5 Coolant hole 10 Nuclear fuel channel 11B Coolant hole 12 Nuclear fuel channel tube 13 Gap 14 Zircaloy nuclear fuel matrix 20 Nuclear fuel channel 22A Inner nuclear fuel channel tube 22B Outer nuclear fuel channel tube 23 Gap 24 Zircaloy nuclear fuel matrix 26 coolant holes 40 reactor vessel 50 reactor 51 pressurizer 52 steam generator 56 moderator tank 58 safety valve 59 moderator cooling heat exchanger

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-52098 (JP, A) JP-A-47-28872 (JP, A) JP-A-50-89790 (JP, A) 55195 (JP, U) "New Edition Nuclear Handbook" 1st Edition (1989-3-30) Ohmsha Co., Ltd. 377

Claims (10)

(57) [Claims] A cylindrical metal nuclear fuel matrix (4) for maintaining a predetermined gap (3) with said nuclear fuel channel tube (2) in a nuclear fuel channel tube (2) comprising a cylindrical tube of a zirconium alloy, A nuclear fuel channel characterized in that a number of coolant holes (5 and 5A) are formed in the metal nuclear fuel matrix (4) to allow coolant to flow. 2. A hole (5) formed in the center of said metal nuclear fuel matrix (4) in said plurality of coolant holes (5).
2. The nuclear fuel channel according to claim 1, wherein a burnable poison and a core measuring device are inserted in A). 3. The nuclear fuel channel according to claim 1, wherein the gap is filled with a helium (He) gas. 4. A zircaloy nuclear fuel matrix (14) for maintaining a predetermined gap (13) with said nuclear fuel channel tube (12) in a nuclear fuel channel tube (12) formed in a zirconium alloy cylindrical tube,
A large number of holes (11A, 11B and 11C) are formed in the Zircaloy nuclear fuel matrix (14), nuclear fuel is put in some holes (11A), and some holes (11B) are used as coolant holes. Nuclear fuel channel characterized by the following. 5. The multiple holes (11A, 11B and 11B).
The nuclear fuel channel according to claim 4, characterized in that a burnable poison or a core measuring device is inserted into the hole (11C) located at the center in (C). 6. A nuclear fuel channel tube (2) divided into an inner nuclear fuel channel tube (22A) and an outer nuclear fuel channel tube (22B) arranged concentrically.
2A, 22B), a Zircaloy nuclear fuel matrix (24) is located in the space between the two nuclear fuel channel tubes (22A, 22B) and the nuclear fuel matrix (2).
4), a predetermined gap (23) is maintained, and a large number of holes (2) are formed in the Zircaloy nuclear fuel matrix (24).
5. Nuclear fuel according to claim 4, characterized in that nuclear fuel is introduced into some of the holes (25) so that the coolant flows through the remaining coolant holes (26). Channel. 7. The helium (He) gas is filled in each of the gaps (13 or 23).
Alternatively, a nuclear fuel channel according to any of the preceding claims. 8. A reactor (50) having a number of nuclear fuel channels arranged in a reactor vessel (40) immersed in a moderator having a lower pressure than a coolant, and an upper part of the reactor (50). The moderator in the reactor (50) communicates with the reactor vessel (40) in the reactor (50) by a moderator circulation circuit (55) having a moderator circulation pump (57). Configured to circulate,
A moderator tank (56) provided with at least one safety valve (58) that opens and closes naturally by pressure; and a coolant inlet and outlet (60 and 61) communicating with the moderator tank (56). Moderator cooling heat exchanger (59) for inflowing and outflowing cooling water from the reactor and cooling the moderator with the cooling water, and a coolant pipe (5) having a reactor coolant pump (53).
4) at least one steam generator (52) connected to the reactor (50) through energy generated by the reactor (50), and one of the steam generators (52); A pressurizer (51) connected to a connected high-temperature pipe and pressurizing a coolant flowing into the steam generator (52), wherein the nuclear fuel channel comprises: A cylindrical metal nuclear fuel matrix (4) for maintaining a predetermined gap (3) with the nuclear fuel channel tube (2) is disposed in a nuclear fuel channel tube (2) composed of a zirconium alloy cylindrical tube, (4) A plurality of circular coolant holes (5 and 5A) are formed so as to allow the coolant to flow therethrough. The furnace. 9. A reactor (50) having a number of nuclear fuel channels arranged in a reactor vessel (40) immersed in a moderator having a lower pressure than a coolant, and an upper portion of the reactor (50). The moderator in the reactor (50) communicates with the reactor vessel (40) in the reactor (50) by a moderator circulation circuit (55) having a moderator circulation pump (57). Configured to circulate,
A moderator tank (56) provided with at least one safety valve (58) that opens and closes naturally by pressure; and a coolant inlet and outlet (60 and 61) communicating with the moderator tank (56). Moderator cooling heat exchanger (59) for inflowing and outflowing cooling water from the reactor and cooling the moderator with the cooling water, and a coolant pipe (5) having a reactor coolant pump (53).
4) at least one steam generator (52) connected to the reactor (50) through energy generated by the reactor (50), and one of the steam generators (52); A pressurizer (51) connected to a connected high-temperature pipe and pressurizing a coolant flowing into the steam generator (52), wherein the nuclear fuel channel comprises: A zircaloy nuclear fuel matrix (14) for maintaining a predetermined gap (13) with the nuclear fuel channel tube (12) is positioned in a nuclear fuel channel tube (12) made of a zirconium alloy cylindrical shape. Forms a number of holes (11A, 11B and 11C), a portion of holes (11A) is filled with nuclear fuel, and a portion of holes (11B) is Specific safety water cooling tube reactor, characterized in that so as to use as a 却材 hole. 10. A reactor vessel (40) with a number of nuclear fuel channels immersed in a moderator having a lower pressure than a coolant.
And a moderator circulation circuit (55) provided above the reactor (50) and having a moderator circulation pump (57). And configured to circulate the moderator in the reactor (50) in communication with the reactor vessel (40);
A moderator tank (56) provided with at least one safety valve (58) that opens and closes naturally by pressure; and a coolant inlet and outlet (60 and 61) communicating with the moderator tank (56). Moderator cooling heat exchanger (59) for inflowing and outflowing cooling water from the reactor and cooling the moderator with the cooling water, and a coolant pipe (5) having a reactor coolant pump (53).
4) at least one steam generator (52) connected to the reactor (50) through energy generated by the reactor (50), and one of the steam generators (52); A pressurizer (51) connected to a connected high-temperature pipe and pressurizing a coolant flowing into the steam generator (52), wherein the nuclear fuel channel comprises: The inner nuclear fuel channel tube (22A) and the outer nuclear fuel channel tube (22B) are arranged concentrically, and the Zircaloy nuclear fuel matrix (24) is located in the space between the two nuclear fuel channel tubes (22A, 22B). A predetermined gap (23) is maintained between the nuclear fuel channel tubes (22A, 22B) and the nuclear fuel matrix (24). A large number of holes (25, 26) are formed in the Zircaloy nuclear fuel matrix (24), nuclear fuel is put into some of the holes (25), and coolant flows through the remaining holes (26). An inherently safe water-cooled tube reactor.