JPH09127282A - Fast reactor core and its special assembly - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent void reactivity of coolant (Na) from increasing during the trip of primary system main pump. SOLUTION: By loading special fuel assemblies 1 containing gas cans 3, 4 in wrapper tubes 2 in the core, a fast reactor core is constituted. The gas cans 3, 4 locate in core region 5 as shown in (b) and move to the regions of upper and lower axial blankets 6, 7 during the trip of the primary system main pump as shown in (c). As the gas cans 3, 4 increase neutron leakage out of the core when the primary main pump tripped and coolant flow stopped, negative reactivity can be added in the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fast reactor core using liquid metal sodium as a coolant for a core fuel, and a special assembly loaded in the core.

[0002]

2. Description of the Related Art Generally, a fast reactor core is composed of a large number of fuel assemblies loaded with fissile material, and liquid sodium is mainly used as a coolant for removing heat from the fuel. Normally, the temperature of each part of the core is stably maintained by keeping the flow rate constant, but it is now possible to safely stop the core even if the cooling capacity drops, such as by stopping the coolant pump. ing.

When an abnormal phenomenon such as a decrease in flow rate occurs in the nuclear reactor, the scram signal promptly scrams to shut down the nuclear reactor, resulting in a sufficiently safe reactor shutdown state. On the other hand, even if you can not scrum,
If the negative reactivity is passively input and the reactor power decreases,
The integrity of the core is secured.

As a passive reactor shutdown mechanism for that purpose, a special assembly in which a gas is enclosed has been proposed, and a core in which a special assembly a as shown in FIG. 24 is arranged between fuel assemblies or in the peripheral portion is considered. There is.

This special assembly a has a trumpet tube f, sodium b which flows in through an orifice e of an entrance nozzle d connected to the lower part of the trumpet tube f, and an enclosed gas c which covers the liquid surface of the sodium b. A shielding plate g and a trumpet tube f are included, a handling head h is connected to the upper part of the trumpet tube f for easy handling, and a lifting prevention weight (lower shield) i is arranged below the trumpet tube f. .

However, the special assembly a is
The enclosed gas c is compressed by the discharge pressure of the pump, and the sodium coolant liquid level h rises from the core upper end level m to the vicinity of the upper shaft blanket upper end level 1 above. On the other hand, when the sodium coolant pressure drops due to a pump stop accident, etc., the liquid level drops, and drops from the core lower end level n to the pump stop liquid level j near the lower lower blanket lower end level σ. . As a result, neutrons from the core can be streamed up and down through the gas space of the special assembly to give a negative reactivity to the core and safely stop the reactor.

FIG. 25 is a schematic top view of the special assembly a loaded in a fast reactor core. In the figure, symbol p is a core fuel assembly, q is a blanket fuel assembly, and γ is a neutron shield. s indicates control rods, respectively.

[0008]

In a fast reactor which uses liquid metal sodium as a coolant for the core fuel, the primary system main pump trips during the operation of the reactor, and the flow of the coolant is lost, so that the control rod should be removed. If the reactor cannot be stopped without being inserted into the core properly, the core fuel will not be cooled. Then, the temperature of the coolant rises, the coolant density decreases, and a positive reactivity is added to the core. As a result, the power output of the core increases and there is a risk that the core fuel will be damaged.

In order to avoid this, a function of adding a negative reactivity to the core is provided when the primary system main pump trips,
It is necessary to make the positive reactivity added to the core sufficiently smaller than that of the conventional fast reactor core. However, conventionally, there is a problem that a device or the like that can add a negative reactivity to the core when the primary system main pump is tripped is not installed.

The present invention has been made to solve the above problems, and in a fast reactor using liquid metal sodium as a coolant for a core fuel and a special fuel assembly loaded in the core, a trip of a primary system main pump is performed. It is another object of the present invention to provide a fast reactor core and a special assembly thereof in which a negative reactivity can be added to the core by increasing the neutron leakage to the outside of the core when the flow of the coolant disappears.

[0011]

According to a first aspect of the present invention, there is provided a fast reactor core in which a core region is composed of a large number of fuel assemblies loaded with fissile material, and liquid metal sodium is used as a coolant. It is characterized in that a special assembly in which a gas can that can move in the vertical direction with the flow of the coolant is arranged in a trumpet tube is loaded in the core region.

According to a second aspect of the present invention, the special assembly includes a trumpet tube and at least one gas can disposed in the trumpet tube, and the trumpet tube has a central portion with the core region. Located at the center of the core along the axial direction, the upper and lower parts have a length that is located in the vertical shaft blanket, the gas can is located near the center of the core region during operation of the primary system main pump, and when the pump trips, It is characterized by having a function of moving to at least one of the upper and lower ends of the core region.

According to a third aspect of the present invention, the special assembly has a flow rate distribution mechanism capable of moving the gas can up and down in the trumpet pipe together with the flow of the coolant during the operation of the primary system main pump and the trip. It is characterized by

According to a fourth aspect of the present invention, an entrance nozzle having a coolant inflow hole is connected to a lower part of the trumpet pipe, and a handling head having a coolant outflow hole is connected to an upper part thereof.
An inner pipe having concentric coolant channels is provided in the trumpet pipe, an intermediate orifice is provided across the center of the inner pipe, and an upper gas can and a lower gas are provided above and below the intermediate orifice. A can is provided, and a communication hole communicating with the coolant channel is provided on a side surface of the inner pipe near the intermediate orifice.

A fifth aspect of the present invention is characterized in that each of the gas cans is subdivided in a vertical direction or a horizontal direction.
A sixth aspect of the present invention is characterized in that a diffuser is provided on an outer surface of the inner pipe in which the intermediate orifice is located, and a communication hole communicating with the inside of the inner pipe is provided in the diffuser.

According to a seventh aspect of the present invention, a partition plate is provided instead of the intermediate orifice, a communication hole is provided in the inner pipe in the upper and lower portions of the partition plate, and a stopper is provided at the upper end of the inner pipe. It is characterized by

According to claim 8 of the present invention, an intermediate stopper is provided in place of the intermediate orifice, a communication hole is provided in the inner pipe in the vicinity of the upper and lower sides of the intermediate stopper, and a downward flow path is provided at the upper end of the inner pipe. It is characterized by being provided.

According to a ninth aspect of the present invention, a partition plate is provided in place of the intermediate orifice, a communication hole is provided in the inner pipe at a position near the partition plate in the vertical direction, and is located above the partition plate. The inner tube is provided with an annulus passage,
An upper orifice plate is provided in the vicinity of the upper end of the inner pipe, an outer closing plate is provided in a coolant passage in which the upper orifice plate is located, and a communication hole communicating with the coolant passage and the inner pipe is provided. Is characterized by.

According to a tenth aspect of the present invention, a ring head is provided with a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end, and an annulus passage and a center along an axial direction of a central portion in a trumpet pipe. A flow path member having a flow path is provided, a partition plate is provided at a central portion in the horizontal direction in the trumpet tube, and donut-shaped gas cans are provided above and below the partition plate, respectively.

According to an eleventh aspect of the present invention, an outlet hole is provided in a central side surface of a trumpet pipe having a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end, and the outlet pipe is provided. A flow path pipe having a central flow path is provided in the central part in the axial direction of, and a flow path hole is provided in the upper part of the flow path pipe, and a small-diameter partition plate is provided in the central part of the flow path. Each is characterized by being provided with a donut-shaped gas can.

According to a twelfth aspect of the present invention, a cooling medium is concentrically provided between the handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end and concentrically with the wrapper pipe. An inner cylinder is provided with a flow path, and a perforated plate is attached to the horizontal center of the inner cylinder.
It is characterized in that a plurality of gas-filled balls are arranged above and below the perforated plate.

According to a thirteenth aspect of the present invention, an upper gas can and a lower gas can are stacked and arranged in a trumpet pipe having a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end. A shape memory alloy spring is interposed between the upper gas can and the handling head, and between the lower gas can and the upper part of the entrance nozzle, respectively.

According to a fourteenth aspect of the present invention, a cooling medium is concentrically provided between the handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end and concentrically with the wrapper pipe. An inner cylinder having a flow path is provided, a guide rod is provided at a central portion in the inner cylinder along the axial direction, and a pair of donut-shaped gas cans having a fitting structure that move up and down along the guide rod are provided. It is characterized by

A fifteenth aspect of the present invention is characterized in that the pair of donut-shaped gas cans having the fitting structure are formed in a wedge shape in which the fitting portions are fitted to each other. According to a sixteenth aspect of the present invention, a coolant channel is concentrically provided between the handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end and concentrically with the wrapper pipe. An inner cylinder is provided, an intermediate orifice is provided in the inner cylinder below the core center plane, and a gas can is arranged on the intermediate orifice.

According to a seventeenth aspect of the present invention, an intermediate orifice is provided above the center surface of the core in a trumpet tube having a handling head having a coolant outlet hole at the upper end and an entrance nozzle having a coolant inlet hole at the lower end. A gas can is arranged below the intermediate orifice.

According to the eighteenth aspect of the present invention, a cooling medium outlet hole is provided at a central portion along an axial direction in a trumpet pipe provided with a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end. A central flow path tube having the core tube is provided, a stopper is provided on an inner surface of the trumpet tube above a core center surface, and a donut-shaped gas can guided below the stopper is provided along the central flow path tube. Is characterized by.

In a nineteenth aspect of the present invention, an intermediate orifice is provided above the core center plane on the inner surface of a trumpet tube having a handling head having a coolant outlet hole at the upper end and an entrance nozzle having a coolant inlet hole at the lower end. It is characterized in that a plurality of gas-filled balls are arranged below the intermediate orifice.

According to a twentieth aspect of the present invention, a plurality of gas-filled spheres connected by a chain are provided in a trumpet tube provided with a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end. The chain is fixed to the lower part of the trumpet tube, and the length of the chain is set so that the uppermost gas-filled ball is located above the core center plane when the gas-filled ball floats. And

According to a twenty-first aspect of the present invention, an intermediate orifice is provided above the core center plane in a trumpet tube provided with a handling head having a coolant outlet hole at the upper end and an entrance nozzle having a coolant inlet hole at the lower end. It is characterized in that a plurality of gas-filled disks connected by a chain are provided below the intermediate orifice.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, the axial distribution of the coolant void reactivity in the special assembly 1 inserted in the core of a fast reactor shows a positive reactivity in the center of the core, Near the outer end of 1 and the upper and lower axial blankets 2 and 3, a negative reactivity is shown due to the leakage of neutrons out of the system. The present invention effectively utilizes the axial distribution of the coolant void reactivity in the special assembly 1.

FIG. 1A shows the axial distribution of the reactivity of the coolant (Na) void in the core region 5 of the special assembly 1. FIG. 1B corresponds to the axial distribution of FIG. 1A, and the positions of the upper and lower gas cans 3 and 4 in the trumpet pipe 2 in the first example of the special fuel assembly 1 during pump operation. FIG. 3 is a vertical cross-sectional view schematically showing this state. FIG. 1C is a vertical cross-sectional view schematically showing the state of the upper and lower gas cans 3 and 4 in the trumpet tube 2 of the special fuel assembly 1 at the time of pump trip.

In the fast reactor core, as shown in FIG. 1A, the coolant (Na) void reactivity has a positive value in the center of the core region 5, and the upper and lower axial blankets 6 and 7 have negative values. ing.

The special fuel assembly 1 has an upper gas can 3 and a lower gas can 4 housed in a trumpet tube 2 as shown in FIG. 1 (b). These upper gas can 3 and lower gas can 4
Are located in the core region 5 during pump operation, and are located in the upper shaft blanket 6 and the lower shaft blanket 7 during pump trip.

When the nuclear reactor is operating and the primary system main pump is operating, as shown in FIG. 1 (b), the special assembly 1 inserted in the core region is vertically moved near the core surface. The partial gas cans 3, 4 are located. These gas cans 3,
4 is divided into upper and lower parts, which can move up and down in the special assembly 1 with the flow of the coolant, and when the primary pump trips, the upper gas can 3 moves to the upper core end, that is, near the upper shaft blanket 6, Further, the lower gas can 4 moves to the lower core end, that is, near the lower shaft blanket 7.

The upper and lower gas cans 3 and 4 are made of stainless steel and are filled with a rare gas such as helium or argon. As a result, the coolant (N
a) The void reactivity region can be used simultaneously.

That is, the movement of the respective gas cans 3 and 4 causes the coolant to flow into the central original gas can position in the special assembly 1. At the center of the special assembly 1, a positive reactivity is added when the coolant is voided, so that a negative reactivity is added to the core by the inflow of the coolant. Furthermore, as a result, the coolant is removed and the gas flows in near the upper and lower shaft blankets 6 and 7, and the leakage of neutrons to the outside of the system increases.

As a result, in addition to the addition of the negative reactivity in the center of the core, the insertion amount of the negative coolant (Na) void reactivity can be further increased. Therefore, the number of cores required for the special assembly can be reduced as compared with the special assembly having only one gas can.

FIG. 2 shows a second example of the special assembly shown in FIG. 1 in which one long gas can 8 is inserted (stored) in the trumpet tube 2, and the other parts are shown in FIG. 1 (b). Is the same as. In FIG. 2, the same portions as those in FIG. 1 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted.

The second example is different from the first example in that only one long gas can 8 is inserted in the trumpet tube 2. This long gas can 8 is used in the core region 5 during the operation of the primary main pump.
It is located in the upper shaft or lower shaft blanket 6, 7 when the primary main pump trips.

That is, when the primary main pump trips, the long gas can 8 moves from the center of the core to the vicinity of the upper or lower core boundary. In this case, it is necessary to increase the number of special assemblies required by about 30% from the number of special assemblies in which two gas cans 3 and 4 are inserted as in the first example. FIG. 3A shows a cross section of the long gas can 8 of the special fuel assembly 1 shown in FIG. 2B.

As shown in FIG. 3 (a), the flow passage 9 for the coolant is made slightly wider so as not to hinder the movement of the gas can 8 in the trumpet can 2. FIG. 3B shows an application example in which the gas can is divided, and in this example, the small gas cans 8a to 8g are obtained by subdividing the gas can 8 of FIG. 3A into seven pieces in the vertical direction. The seven small gas cans 8a to 8g are connected to each other by chains (not shown) or the like so as not to be separated from each other in the vertical direction. The movement to the left and right can be freely done within the range of the gap.

Next, an application example in which the upper gas can 3 and the lower gas can 4 shown in FIG. 1B are divided will be described with reference to FIG. That is, the upper gas pipe 3 and the lower gas can 4 are laterally divided into three, respectively, into small cans 3a to 3c and 4a to 4c, and the small cans 3a to 3c and 4a to 4c are connected by a chain 10 and The distance between them is set so that they can be moved to the left and right freely within the range of the gap.

Next, the effect of Na voids on the reactivity caused by the vertical movement of the gas can and the appropriate gas can length to be taken will be described. The gas can can move up and down in the cooling pipe (Na) in the trumpet tube 2 by the balance of buoyancy and power. As shown in FIG. 2A, the axial distribution of the coolant void reactivity of the core fuel assembly inserted in the homogeneous fast reactor core shows a positive reactivity in the vicinity of the center plane of the core region 5, Near the outer end of the core region and the axial blankets 6 and 7, negative reactivity is shown.

Further, the length of the axial region showing the positive reactivity is generally long in the core fuel inserted in the central region of the homogeneous core and short in the outer core region. In the case of the special assembly inserted in the core region, the coolant (Na) void axial distribution is almost the same as that of the core fuel.

Therefore, in the homogeneous fast reactor core in which such a special assembly 1 is inserted, the length of the gas can is set to be substantially the same as the length of the region showing the positive coolant (Na) void reactivity, The gas can floats in the center of the reactor in balance between buoyancy and gravity as shown in FIG. 2 (b) during the reactor rated output operation, that is, during the primary system main pump rated output operation.

If a stopper is provided in the trumpet tube 2 on the side where the gas can 8 does not move, the gas can 8 can be reliably positioned near the center plane of the core. When the primary system main pump stops operating (trips) for some reason, the gas can 8 moves to the upper or lower end of the core region 5 and the vertical axis blanket region due to the balance between buoyancy and gravity.

By doing so, in this case, the coolant (N
a) The void reactivity is as follows. When the gas can located at the center of the core moves up or down, first, the coolant flows into the position where the central gas can was located, so a phenomenon opposite to the coolant (Na) void occurs. That is, the negative reactivity is inserted.

At the end of the core region and the axial blanket region, it is equivalent to the fact that the coolant (Na) becomes void due to the arrival of the gas can. Therefore, the leakage of neutrons from the core region increases and the negative Is added to the core. Thus, by moving the gas can from the center of the core to the vicinity of the end of the core region, the negative reactivity of both the center of the core and the vicinity of the outer end of the core is inserted into the core, so that the effect becomes large. .

Further, the length of the gas can is properly adjusted by the insertion core region of the special assembly, that is, the positive direction of the coolant (Na) void reactivity in the positive axial direction of each position in the core region. It is important to take the same length as the area length.
Since this special assembly does not contain fissile material such as core fuel, there is almost no heat generation during reactor operation and there is no cooling problem.

Electric output of the special assembly with a built-in gas can of the present invention
The amount of negative reactivity added when the primary system main pump trips when inserted into the core region of a large fast reactor using 1 million kWh of MOX fuel is shown below.

The fast reactor core of the present invention is a homogeneous two-zone core having a height of 1 m. The fuel used is MOX. In this core region, 43 special assemblies with built-in gas cans are inserted as shown in FIG. The length of this gas can corresponds to the region where the Na void reactivity is almost positive, and the length of each can in the case of the two upper and lower gas cans 4 and 5 shown in FIG. Each is about 30 cm.

The volume ratio of the gas in the gas cans 4 and 5 is about 75% in the special assembly trumpet pipe 6 in cross section. By moving these two gas cans 4 and 5 up and down during a pump trip, the center area of the core area 1 costs about -1.5 $, the upper and lower shaft blankets 2 and 3 cost about -2.5 $, and the total amount of about- 4 $ reactivity is added.

On the other hand, since the coolant void reactivity of the core fuel in the core assembly is about 5 $, the control rod is virtually not inserted into the core during the primary system main pump trip, and the core fuel is further cooled. Without doing so, the coolant in the reactor core is voided and about 5
When a reactivity of $ is inserted into the core, it is possible to suppress the nuclear runaway of the core by suppressing the overall reactivity added to the core by 43 special assemblies with built-in gas cans to 1 $ or less. is there.

In this case, it is considered that the nuclear runaway of the core at the time of trip of the primary system main pump is suppressed only by the special assembly with built-in gas can, but in reality, other negative core characteristics, that is,
Doppler reactivity, fuel expansion, and outward bending of core fuel are added to the core, so 43 special assemblies with built-in gas cans are not required. The required number is determined by the core design.

When the primary system main pump is started at the time of starting the operation of the nuclear reactor, the dispersed gas cans approach the core center plane, and a positive reactivity is inserted into the core. If the coolant void reactivity by the special assembly with built-in gas can is 4 $, the reactivity required up to the rated output of this reactor is 6
Since it is about $, the heat output of the reactor does not reach the rated output even when the main pump is operating at the rated output, and the temperature of the core fuel and the like is lower than that in the rated operation of the reactor. Rated operation of the reactor is achieved by pulling the control rods out of the core.

Next, the structure of the special assembly 1 containing the two gas cans 3 and 4 shown in FIG. 1 (b) and the two gas cans 3 during operation and trip of the primary system main pump are shown. The movement state of No. 4 will be specifically described.

FIG. 6 shows a vertical cross section of the structure of the special assembly 1a having two gas cans 3 and 4, the flow of the coolant, and the two gas cans at the time of operation and trip of the primary system main pump. Indicates the position of. Further, FIG. 7 shows the horizontal section and the size of the gas can.

In the following, two gas cans 3 and 4 are shown in FIG.
It is specifically noted that the position can be moved to the position shown in (c) and FIG. 6 (b). First, the conditions under which the two gas cans can move to the positions shown in FIGS. 1C and 6B will be described below.

FIG. 6 (a) shows the first in the special aggregate 1a.
6 (b) shows a pump trip, and FIG. 6 (c) shows a flow path equivalent circuit diagram of the special assembly. P _{1 to} P in FIG. 6C
₅ corresponds to P _{1 to} P ₅ shown in FIG.

In the special assembly 1a shown in FIG. 6 (a), the entrance nozzle 11 is connected to the lower end of the trumpet tube 2 and the handling head 12 is provided at the upper end. The entrance nozzle 11 is provided with a coolant inflow hole 13, and the handling head 12 is provided with a coolant outflow hole 14.

An inner pipe 15 is concentrically provided in the trumpet pipe 2 with a coolant passage 9, and an intermediate orifice 16 is provided at the center of the inner pipe 15 to divide the inner pipe 15 into upper and lower parts. An upper gas can 3 and a lower gas can 4 are arranged above and below the intermediate orifice 16.

A communication hole 18 is provided on the side surface of the inner pipe 15 slightly above the position where the intermediate orifice 16 is attached, and the side surface of the trumpet pipe 2 facing the communication hole 18 flows out through a flow passage pipe 19. A hole 20 is formed. The flow passage pipe 19 is interposed between the inner pipe 15 and the trumpet pipe 2 across the coolant flow passage 9.
It communicates with the communication hole 18 and the outflow hole 20.

In FIG. 6A, m ₁ and m ₂ are weights of gas cans, 1 is a lower gas can, 2 is an upper gas can,
Fu ₁ and Fu ₂ are buoyant forces, and Fp ₁ and Fp ₂ are forces due to the pressure difference. 6 (b) is a state in which the gas cans 3, 4 are moved up and down in FIG. 6 (a), the same parts as those in FIG. 6 (a) are designated by the same reference numerals, and the description of the overlapping parts will be omitted. . FIG. 7A is a cross-sectional view taken along the line X-X of FIG. 6A, and FIG. 7B shows the gas cans 3 and 4 of FIG. 7A.

(I) Upper and lower gas cans 3 and 4 during pump operation
Exists at the center of the core (1) The condition that the upper gas can 3 exists at the position A due to the pressure balance of the upper gas pipe 3 Fp ₂ + m ₂ > Fu ₂ (1) (2) Lower gas pipe 4 Condition that lower gas can 4 exists at position B due to the pressure balance of Fp ₁ + Fu ₁ > m ₁ (2)

(II) Condition that upper and lower gas cans 3 and 4 exist above and below the core at the time of pump trip (1) Due to the power balance of the upper gas can 3, the upper gas can 3 is in buoyancy to the A'position. Condition m ₂ <Fu ₂ ··· (3) (2) Condition for lower gas can 4 to be in position B ′ due to power balance of lower gas can 4 Fu ₁ <m ₁ ··· (4) If the above four conditions are satisfied, the gas can structure in the special assembly is established.

Here, the pressures of P _{0 to} P ₅ are set as follows, but this is structurally possible. However, A is the area (cm ² ) of the horizontal cross section of the gas can. During pump operation (unit: kg / cm ² ) P ₀ = 8A, P ₁ = 5A, P ₂ = 4A, P ₃ = 4A, P
₄ = 3.5 A, when P ₅ = 2.5 A pump trip _{P 0 ~P 1 ~P 2 ~P 3} ~P 4 ~P 5 ( liquid level difference only)

The volume V, weight m and cross-sectional area (pressure receiving surface) A of the gas can shown in FIG. 7 are as follows. V = 4.66 x 10 ^-3 m ³ m ₁ = 4.17 kg (lower gas can) m ₂ = 3.84 kg (upper gas can) A = 1.55 x 10 ² cm ²

By using these values, it is shown that the above-mentioned four conditions are satisfied. (A) In the case of lower gas can (A-1) During pump operation (equation (2)) F _P1 + F _u1 = 155 +3.96 = 158.96 kg m ₁ = 4.17 kg ∴F _P1 + F _u1 > m ₁ (A- 2) During pump trip (Equation (4)) F _u1 = 3.96 kg m ₁ = 4.17 ∴F _u1 <m ₁

(B) In the case of upper gas can (B-1) During pump operation (equation (1)) F _p2 + m ₂ = 77.7 + 3.84 = 81.54 kg F _u2 = 3.96 kg ∴F _p2 + m ₂ > F _u2 (B-2) Pump trip (Equation (3)) m ₂ = 3.844kg F _u2 = 3.96 kg ∴m ₂ <F _u2 Due to the above, the gas cans are shown in Figs. 1 (b), 1 (c) and 6
It is clear that it can be moved to the position shown in.

The difference in weight (force) between (A-2) and (B-2) (100 to 200 g) is small, but
In the case of (A-2), the weight of m ₁ is increased (with a weight), and in the case of (B-2), the difference in thickness can be increased by slightly reducing the wall thickness of the gas can, The moving speed of the gas can can be increased.

Next, second to sixteenth embodiments of the special assembly to be loaded into the fast reactor core according to the present invention will be described with reference to FIGS.
This will be described with reference to FIG. In addition, in each figure, FIG.
The same reference numerals are given to the same portions or portions having the same functions, and the description of the overlapping portions is omitted. Further, in each figure, (a) shows a state during pump operation, and (b) shows a state during pump trip.

FIG. 8 shows a special aggregate 1b according to claim 6.
In the second embodiment of the present invention, this special assembly 1b is provided with a diffuser 21 on the outer surface of the central portion of the inner cylinder 15, and a communication hole 18 is formed in this diffuser 21 so that the inside of the inner cylinder 15 and the coolant passage 9 are formed. Is in communication with. Inside the inner cylinder 15 in which the diffuser 21 is located, a perforated plate 44 that divides the upper gas can 3 and the lower gas can 4 is provided.

In this example, the coolant flowing from the diffuser 21 into the inner can 15 is caused to flow into the coolant passage 9 on the outer side to form a passage for pump operation. The portion of the diffuser 21 becomes a low pressure portion, and by providing the diffuser 21, a low pressure field can be easily obtained. Further, since it is not necessary to provide the outflow hole 20 of the trumpet tube 2 shown in FIG. 6, there is an effect that the structure becomes easy.

FIG. 9 is a special assembly 1c corresponding to claim 7.
In the third embodiment, the special assembly 1c is provided with a partition plate 22 in place of the intermediate orifice 16 shown in FIG. 6, and a communication hole 18 is provided in the inner pipe 15 near the partition plate 22 in the vertical direction. It is provided.

In this example, the partition plate 22 allows the coolant to flow from the upper and lower communication holes 18 to the trumpet tube 2 side, and the outflow hole 20 provided in the trumpet tube 2 shown in FIG. It has the effect of being easy.

FIG. 10 shows a special aggregate 1d corresponding to claim 8.
In the fourth embodiment, the special assembly 1d is provided with an intermediate stopper 23 instead of the intermediate orifice 16 shown in FIG.
The communication hole 18 is provided in the inner pipe 15, and the descending flow path 24 is provided at the upper end of the inner pipe 15 toward the inner pipe 15.

According to this example, the intermediate stopper 23 is provided, and the middle orifice 16 shown in FIG. 6 and the partition plate 22 shown in FIG. The configuration is such that there are many. Therefore, since only the intermediate stopper 23, the opening area of the coolant increases,
The vertical movement of the gas cans 3 and 4 can be performed quickly.

FIG. 11 shows a special assembly 1e corresponding to claim 9.
In the fifth embodiment, the special assembly 1e is provided with the partition plate 22 in the center of the inner pipe 15 and the annulus passage 25 extending from the vicinity of the lower portion of the partition plate 22 to the upper end.
Inner pipes communicating with the annulus passage 25 near the top and bottom of the partition plate 22
A communication hole 18 is provided in 15 and an upper orifice plate 26 is provided in the inner pipe 15 near the upper end. An outer closing plate 27 is provided between the outer surface of the upper end of the inner tube 15 and the inner surface of the trumpet tube 2. In addition, a flow passage hole 45 that communicates with the coolant flow passage 9 and the inner pipe 15
Is provided on the upper part of the inner pipe 15.

According to this example, the inside of the annulus channel 25 has a low pressure field similar to the outlet pressure of the assembly 1e, and the low-pressure side channel can be surely kept independent by the annulus channel 25, Further, since the source pressures to the upper gas can 3 and the lower gas can 4 are parallel paths, they are secured without interference.

FIG. 12 shows a special aggregate 1f corresponding to claim 10.
The sixth embodiment of is shown. That is, the special assembly 1f is provided with a partition plate 22 in the horizontal center of the trumpet tube 2, and penetrates through the center of the partition plate 22 to form the annulus passage 25.
And a flow path member having a central flow path 46 that flows through the central portion in the axial direction
This is because the upper and lower donut-shaped gas cans 28 (28a, 28b) are provided with the partition plate 22 as a sakai so as to be inserted through the flow path member 47.

An upper closing plate 48 is attached to the upper end of the flow path member 47. A central outlet 29 communicating with the central flow path 47 and a plurality of small holes 49 communicating with the inside of the trumpet tube 2 are formed in the center of the upper blocking plate 48. An annulus inlet 30 is formed in the lower part of the flow path member 47.

According to this example, the inner pipe 15 shown in FIG. 6 is removed, an annulus passage is provided at the center, and the central flow passage outlet 29 is used as a low pressure field to allow the coolant to flow out. Since the gas can is doughnut-shaped and the can diameter can be increased, the gas volume can be increased and the manufacturability is improved by providing the annulus passage in the center.

FIG. 13 shows a special aggregate 1g corresponding to claim 11.
The seventh embodiment of is shown. That is, the special assembly 1g is provided with the outflow hole 20 in the side surface of the central portion of the trumpet tube 2, the channel tube 50 having the central channel 31 in the axial center of the trumpet tube 2, and the upper portion of the channel tube 50. A flow path hole 51 is provided in the
A small-diameter partition plate 52 is provided in the central portion of 50, and donut-shaped gas cans 28a and 28b are provided above and below the small-diameter partition plate 52, respectively. In this example, as in FIG. 12, the inner tube 15 is not provided and the central flow path 31 is provided at the center of the special assembly 1g, so that the structure is simple and the manufacture is easy.

FIG. 14 is a special assembly 1h corresponding to claim 12.
The eighth embodiment of the present invention is shown. That is, the special assembly 1h has a small diameter nozzle plate at the lower end of the inner pipe 15 in the trumpet pipe 2.
It has 53 and has a perforated plate 44 attached to the horizontal central portion of the inner pipe 15, and a large number of gas-filled balls 32 are arranged above and below the perforated plate 44. The movement of the gas filled sphere 32 is smoothly performed by the flow of the coolant. According to this example, since the gas is enclosed in the spherical body, the operation can be smoothly performed when the pump is started and stopped.

FIG. 15 shows a special aggregate 1i corresponding to claim 13.
9 shows a ninth embodiment of the present invention. That is, the special assembly 1i is provided with a large diameter nozzle plate 54 slightly above the mounting portion of the entrance nozzle 11 in the trumpet tube 2, and is made of a shape memory alloy between the large diameter nozzle plate 54 and the lower gas can 4. The lower gas can 4 and the upper gas can 3 are stacked on the shape memory alloy spring with the spring 33 interposed, and the shape memory alloy spring 33 is interposed between the upper gas can 3 and the handling head 2. Especially.

According to this example, by interposing the shape memory alloy springs 33 on the upper and lower surfaces of the gas cans 3 and 4, respectively,
These springs 33 have a function of expanding when the temperature of the coolant is lower than a certain set value and contracting when the temperature of the coolant is high. Therefore, when the pump is operating, the temperature of the coolant is low, so the spring 33 expands, and when the pump trips, the spring 33 contracts.
The gas cans 3 and 4 move as shown in FIG. Therefore, since the shape memory alloy spring 33 operates due to the temperature change due to the abnormality of the core, it is possible to improve the safety.

FIG. 16 shows a special aggregate 1i corresponding to claim 14.
10 shows a tenth embodiment of the present invention. This special aggregate 1j
Is provided with a guide rod 36 at the center along the axial direction in the inner cylinder 15 provided in the trumpet can 2. The lower fitting gas can 34 and the upper fitting gas that move up and down along the guide rod 36. A can 35 is provided. These gas cans 34, 35 are doughnut-shaped and have gas enclosed therein. As shown in FIG. 16 (b), a recess 34a is formed on the upper surface of the fitting lower gas can 34,
A convex portion 35a is formed on the lower surface of the fitting upper gas can 35,
The concave portion 34a and the convex portion 35a are fitted together.

According to this example, since the gas cans 34 and 35 are fitted to each other, the core insertion of void reactivity is slowed down, and the upper and lower gas cans are integrated when the pump is driven to increase the gas density in the central portion. You can

FIG. 17 shows a special assembly 1k corresponding to claim 15.
11 shows the eleventh embodiment of. This special aggregate 1k
16 is that the fitting lower gas can 34 and the fitting upper gas pipe 35 of the special assembly 1g in FIG. 16 are replaced by a wedge-shaped lower gas can 37 and a wedge-shaped upper gas can 38, and the other parts are shown in FIG.
Is the same as That is, as shown in FIG. 17 (b), a pair of donut-shaped gas cans having a fitting structure are formed with a V-shaped recess 37a in a wedge-shaped lower gas can 37, and a convex part 38a that fits into the V-shaped recess 37a is wedged. The lower gas can 38 is formed.

According to this example, as in the case of FIG. 16, the core insertion of the void reactivity is made slower, and in addition, even if the upper and lower positions are slightly displaced, they can be surely combined. In addition, since it is not necessary to increase the accuracy so much as compared with FIG. 16, it is easy to manufacture.

FIG. 18 shows a special assembly 1l corresponding to claim 16.
12 shows a twelfth embodiment of the present invention. This special aggregate 1l
Is only one long gas can 8 Intermediate orifice 16 in the inner tube 15
It is arranged on the upper side so that the long gas can moves to the upper part in the trumpet tube 2 when the pump trips. During the pump operation, the pressure on the upper surface of the long gas can 8 is adjusted to be higher than that on the lower surface. Therefore, the intermediate orifice 16 is provided below the core center plane.

According to this example, since only one long gas can 8 needs to be provided, the structure is simple and the manufacturability is excellent. The length of the long gas can 8 is preferably equal to the length of the core region, but the length is not limited to this.

FIG. 19 shows a special assembly 1m corresponding to claim 17.
13 shows a thirteenth embodiment of the present invention. This special aggregate 1m
Is to provide an intermediate orifice 16 at a position above the center plane of the core in the trumpet tube 2 and to arrange only one long gas can 8 below the intermediate orifice 16.

According to this example, the inner cylinder is not provided in the trumpet tube 2 and the intermediate orifice 16 is directly attached to the inner surface of the trumpet tube 2, and the attachment position of the intermediate orifice 16 is above the center plane of the core. Therefore, the movement of the long gas can 8 is determined by the balance between the gravity and the gravity pressure when the pump is driven by one long gas can 8, and the design is easy.

FIG. 20 shows a special assembly 1n corresponding to claim 18.
14 shows a fourteenth embodiment thereof. This special aggregate 1n
Is provided with a central flow passage tube 40 at the center of the trumpet tube 2 along the axis, and a stopper is provided on the inner surface of the trumpet tube 2 above the core center plane.
A doughnut-shaped gas can 28, which is guided by a central channel pipe, is arranged below the stopper 39. Coolant outflow holes 54 are provided in the lower part and the upper end of the central flow path pipe 40.

In this example, the doughnut-shaped gas can 28 is guided by the central channel can 40 in the trumpet can 2 and moves downward when the pump trips. As the doughnut-shaped gas can 28 descends, the coolant outflow holes 54 in the lower portion of the central flow path pipe 40 are closed. Forming the gas can in a donut shape has the effect of increasing the volume of gas enclosed.

FIG. 21 shows a special aggregate 1σ corresponding to claim 19.
The fifteenth embodiment of is shown. This special aggregate 1σ
Is provided with an intermediate nozzle 16 above the inner surface of the trumpet tube 2 by the center surface of the core, a plurality of gas-filled balls 41 are provided below the intermediate nozzle 16, and a flow control plate 55 is provided inside the entrance nozzle 11. . The flow control plate 55 regulates the flow rate of the coolant and at the same time prevents the gas-filled sphere 41 from falling into the entrance nozzle 11.

According to this example, the gas-filled sphere 41 is not connected by a chain or the like and can move freely, and moves to the lower part in the trumpet tube 2 when the pump trips. The spherical shape of the gas can has the effect of smooth movement.

FIG. 22 shows a special assembly 1p corresponding to claim 20.
16 shows a sixteenth embodiment thereof. This special aggregate 1p
Attaches a fixing member 56 for fixing both ends of the chain 42 to the lower end of the trumpet tube 2, and the gas-filled ball 41 is attached to the fixing member 56.
This is because the chain 42, which is a chain of beads, is fixed.

The length of the chain 42 must be set so that when the gas-filled sphere 41 floats, the chain 42 forms a loop and the uppermost gas-filled sphere is located above the core center plane. Is. A flow control plate 55 is provided in the entrance nozzle 11 to prevent the gas filled sphere 41 from falling. Figure
22 (b) shows a state in which the gas-filled sphere 41 has dropped and moved during a pump trip.

According to this example, the gas-filled sphere 41 is the chain.
Since it is connected by 42, the position of the gas-filled sphere 41 is set and the reactivity calculation is easy. Moreover, since it is not necessary to provide an inner tube or an intermediate orifice in the trumpet tube 2, the structure is simple and the manufacture is easy. It's easy. Furthermore, after the pump trip,
The gas-filled sphere 41 has a function of moving near the boundary between the core and the lower shaft blanket.

FIG. 23 is a special assembly 1Q corresponding to claim 21.
17 shows a seventeenth embodiment thereof. This special aggregate 1Q
Is an intermediate nozzle 16 inside the trumpet tube 2 and above the core center plane.
A plurality of gas-filled discs 43 are arranged below the intermediate orifice 16 and connected by a chain 42.

This chain 42 is not fixed in the trumpet tube 2 and has the function of being able to move to the vicinity of the boundary between the core and the lower shaft blanket after the pump trip as shown in FIG. 23 (b). There is. According to this example, the gas-filled disk 43 has an advantage that it is easy to combine at the upper part due to the pump pressure.

[0104]

According to the present invention, when the primary system main pump is in operation, the gas can located in the center of the core of the special assembly has a shaft located above and below the center of the core when the primary system pump trips. It moves to the vicinity of the blanket, that is, to the negative void region, and the movement causes the coolant to flow into the center of the core to add a negative reactivity to the core.

Further, as a result, the coolant was removed near the upper and lower shaft blankets, and the gas flowed in. Therefore, in addition to the addition of the negative reactivity in the center of the core, further negative reactivity was introduced into the core. Will be added.

As a result, the primary system main pump trips,
Moreover, when the control rod is not inserted into the core, the special assembly containing the gas can prevents the coolant from boiling and improves the safety of the core.

[Brief description of the drawings]

1A is an axial distribution diagram of a coolant void reactivity for explaining an embodiment of a fast reactor according to the present invention, FIG.
(B) is a longitudinal sectional view showing a state during pump operation in a first example of the special assembly in the present embodiment, and (c) is a longitudinal sectional view showing a state at the time of pump trip from the state of (b).

2 (a) is an axial distribution diagram of the coolant void reactivity as in FIG. 1 (a), and FIG. 2 (b) is a second example of the special assembly according to the present embodiment, showing a state during pump operation. Is a vertical cross-sectional view showing the state, and (c) is a vertical cross-sectional view showing the state at the time of pump trip from the state of (b).

3 (a) is a transverse cross-sectional view schematically showing an enlarged view of the special assembly in FIG. 2 (b), and FIG. 3 (b) schematically shows an application example in which the gas can in FIG. Cross-sectional view.

FIG. 4 is a vertical cross-sectional view schematically showing an application example in which two gas cans of the special assembly in FIG. 1B are each divided into three.

FIG. 5 is a cross-sectional view schematically showing a fast reactor core in which the special assembly shown in FIGS. 1 to 4 is loaded in the core.

6 (a) is a vertical cross-sectional view showing a concrete structure of the special assembly in FIG. 1 (b) as a first embodiment in a state during pump operation, and FIG. 6 (b) is also a state during pump trip. Is a longitudinal sectional view, and (c) is a flow path equivalent circuit diagram in (a).

7 (a) is a cross-sectional view taken along the line X-X of the special assembly in FIG. 6, and FIG. 7 (b) is an elevation view showing the gas can in FIG.

FIG. 8 (a) is a vertical cross-sectional view showing a state during pump operation in the second embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 9 (a) is a vertical cross-sectional view showing a state during pump operation in the third embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 10 (a) is a vertical cross-sectional view showing a state during pump operation in the fourth embodiment of the special assembly according to the present invention;
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 11A is a vertical cross-sectional view showing a state during pump operation in the fifth embodiment of the special assembly according to the present invention;
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 12 (a) is a vertical cross-sectional view showing a state during pump operation in the sixth embodiment of the special assembly according to the present invention;
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 13 (a) is a vertical cross-sectional view showing a state during pump operation in the seventh embodiment of the special assembly according to the present invention;
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 14A is a vertical cross-sectional view showing a state during pump operation of the special assembly according to the eighth embodiment of the present invention;
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 15 (a) is a vertical cross-sectional view showing a state during pump operation in the special assembly according to the ninth embodiment of the present invention;
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 16 (a) is a vertical cross-sectional view showing a state during pump operation in the tenth embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 17 (a) is a longitudinal sectional view showing a state during pump operation in the eleventh embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 18 (a) is a vertical sectional view showing a state during pump operation in the twelfth embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 19 (a) is a vertical sectional view showing a state during pump operation in the thirteenth embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 20 (a) is a vertical cross-sectional view showing a state during pump operation in the fourteenth embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 21 (a) is a longitudinal sectional view showing a state during pump operation in the fifteenth embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 22 (a) is a vertical cross-sectional view showing a state during pump operation in the sixteenth embodiment of the special assembly according to the present invention,
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 23 (a) is a longitudinal sectional view showing a state during pump operation in the seventeenth embodiment of the special assembly according to the present invention;
(B) is a longitudinal cross-sectional view showing a state at the time of pump trip in (a).

FIG. 24 is a vertical sectional view schematically showing a special assembly loaded in a conventional fast reactor core.

FIG. 25 is a top view schematically showing a fast reactor core loaded with a conventional special assembly.

[Explanation of symbols]

1, 1a to 1Q ... Special assembly, 2 ... Trumpet tube, 3 ... Upper gas can, 4 ... Lower gas can, 5 ... Core region, 6 ... Upper shaft blanket, 7 ... Lower shaft blanket, 8 ... Long gas can , 9 ... Coolant channel, 10 ... Chain, 11 ... Entrance nozzle, 12 ... Handling head, 13 ... Coolant inflow hole, 14 ...
Coolant outflow hole, 15 ... Inner pipe, 16 ... Intermediate orifice, 17 ... Upper stopper, 18 ... Communication hole, 19 ... Flow path pipe, 20 ... Outflow hole, 21
... Diffuser, 22 ... Partition plate, 23 ... Intermediate stopper, 24 ...
Downflow channel, 25 ... Annulus channel, 26 ... Upper orifice plate, 27 ... Outer closing plate, 28 ... Donut-shaped gas can, 29 ... Central outlet port, 30 ... Annulus inlet port, 31 ... Central channel channel, 32 ... Gas filling Ball, 33 ... Shape memory alloy spring, 34 ... Fitting lower gas can, 35 ... Fitting upper gas can, 36 ... Guide rod, 37 ... Wedge-shaped lower gas can, 38 ... Wedge-shaped upper gas can, 39 ... Stopper ,
40 ... central flow pipe, 41 ... gas filled sphere, 42 ... chain, 43 ...
Gas-filled disc, 44 ... Dish plate, 45 ... Flow path hole, 46 ... Central flow path, 47 ... Flow path member, 48 ... Upper closing plate, 49 ... Small hole, 50 ... Small hole, 51 ... Flow path hole, 52 ... Small diameter partition plate, 53 ... Small diameter nozzle plate,
43 ... Coolant outflow hole, 55 ... Flow control plate, 56 ... Fixing member.

Claims (21)

[Claims] 1. In a fast reactor core in which the core region is composed of a large number of fuel assemblies loaded with fissile material, and liquid metal sodium is used as a coolant, a gas can which can move vertically with the flow of the coolant. A fast-reactor core, characterized in that a special assembly in which a lamp is placed in a trumpet tube is loaded in the core region. 2. The special assembly includes a trumpet tube and at least one gas can disposed in the trumpet tube, the trumpet tube having a central portion in the center of the core along the axial direction of the core region. The upper and lower ends of the core region are located near the center of the core region during operation of the primary system main pump and have a length such that the upper and lower parts are located in the vertical blanket. 2. A function for moving to at least one of the vicinity is provided.
Fast reactor core described. 3. The special assembly has a flow rate distribution mechanism capable of moving the gas can up and down in the trumpet pipe together with the flow of the coolant during the operation and trip of the primary system main pump. Item 1. A fast reactor core according to item 1. 4. An entrance nozzle having a coolant inflow hole is connected to a lower part of the trumpet tube, a handling head having a coolant outflow hole is connected to an upper part of the trumpet tube, and a concentric coolant channel is provided in the trumpet tube. Inner pipe is provided, an intermediate orifice is provided across the center of the inner pipe, upper and lower gas cans are provided in the upper and lower regions of the intermediate orifice, and the inner pipe side surface near the intermediate orifice is provided. A special assembly, characterized in that a communication hole communicating with the coolant channel is provided in the. 5. The special assembly according to claim 4, wherein each of the gas cans is subdivided in a vertical direction or a horizontal direction. 6. The special assembly according to claim 4, wherein a diffuser is provided on an outer surface of the inner pipe in which the intermediate orifice is located, and a communication hole communicating with the inside of the inner pipe is provided in the diffuser. 7. A partition plate is provided instead of the intermediate orifice, a communication hole is provided in the inner pipe in the vicinity of the upper and lower sides of the partition plate, and a stopper is provided at an upper end portion of the inner pipe. The special assembly according to claim 4. 8. An intermediate stopper is provided in place of the intermediate orifice, a communication hole is provided in the inner pipe near the upper and lower sides of the intermediate stopper, and a descending flow path is provided at an upper end portion of the inner pipe. The special assembly according to claim 4. 9. A partition plate is provided instead of the intermediate orifice, a communication hole is provided in the inner pipe in the vicinity of the upper and lower sides of the partition plate, and an annulus passage is provided in the inner pipe located above the vicinity of the partition plate. An upper orifice plate is provided in the vicinity of the upper end of the inner pipe, an outer closing plate is provided in a coolant passage in which the upper orifice plate is located, and a communication hole communicating with the coolant passage and the inner pipe is provided. The special assembly according to claim 4, wherein 10. A flow having an annulus passage and a central passage along an axial direction of a central portion in a trumpet pipe provided with a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end. A special assembly characterized in that a passage member is provided, a partition plate is provided at a central portion in the horizontal direction in the trumpet pipe, and doughnut-shaped gas cans are provided above and below the partition plate, respectively. 11. An outlet hole is provided in a central side surface of a trumpet pipe having a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end,
A flow path tube having a central flow path is provided in the axial center of the trumpet tube, a flow path hole is provided in the upper part of the flow path tube, and a small-diameter partition plate is provided in the central part of the flow path. A special assembly characterized in that donut-shaped gas cans are provided above and below, respectively. 12. A concentric circular coolant passage is provided between the handling head having a coolant outlet hole at the upper end and an entrance nozzle having a coolant inlet hole at the lower end and concentrically with the wrapper pipe. A special assembly characterized in that an inner cylinder is provided, a perforated plate is attached to a central portion of the inner cylinder in the horizontal direction, and a plurality of gas-filled balls are arranged above and below the perforated plate. 13. An upper gas can and a lower gas can are stacked in a trumpet pipe having a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end, and the upper gas can and the upper gas can are stacked together. A special assembly, wherein a shape memory alloy spring is interposed between the handling head and between the lower gas can and the upper portion of the entrance nozzle. 14. A cooling pipe is concentrically provided between a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end and concentrically with the wrapper pipe. An inner cylinder is provided, a guide rod is provided at a central portion along the axial direction in the inner cylinder, and a pair of donut-shaped gas cans having a fitting structure that move up and down along the guide rod are provided. Special aggregate. 15. The special assembly according to claim 14, wherein the pair of donut-shaped gas cans having the fitting structure are formed in a wedge shape in which the fitting portions are fitted to each other. 16. A cooling pipe is concentrically provided between the handling head having a coolant outlet hole at the upper end and an entrance nozzle having a coolant inlet hole at the lower end, and concentrically with the wrapper pipe. A special assembly characterized in that an inner cylinder is provided, an intermediate orifice is provided in the inner cylinder below a core center plane, and a gas can is arranged above the intermediate orifice. 17. An intermediate orifice is provided above the core center plane in a trumpet tube having a handling head having a coolant outlet hole at the upper end and an entrance nozzle having a coolant inlet hole at the lower end, and below the intermediate orifice. A special assembly characterized by arranging gas cans. 18. A central flow pipe having a coolant outlet hole in a central portion along an axial direction in a trumpet pipe provided with a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end. A special assembly characterized in that a stopper is provided on the inner surface of the trumpet tube above the center surface of the core, and a donut-shaped gas can guided below the stopper along the central flow path tube is provided. body. 19. An intermediate orifice is provided above the core center plane on the inner surface of a trumpet tube provided with a handling head having a coolant outlet hole at the upper end and an entrance nozzle having a coolant inlet hole at the lower end, and below this intermediate orifice. A special assembly characterized by arranging multiple gas-filled balls on the side. 20. A plurality of gas-filled balls connected by a chain are provided in a trumpet tube having a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end, and the chain is connected to the trumpet. A special assembly characterized in that it is fixed to the lower part of a pipe and the length of the chain is set so that the uppermost gas-filled ball is located above the core center plane when the gas-filled ball floats. 21. An intermediate orifice is provided above a core center plane in a trumpet tube having a handling head having a coolant outlet hole at an upper end and an entrance nozzle having a coolant inlet hole at a lower end, and the intermediate orifice is provided below the intermediate orifice. A special assembly characterized by comprising a plurality of gas-filled disks connected by a chain.