JP3199337B2 - Core components of fast reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a fast reactor, to fast reactor core components of utilizing the void reactivity of sodium c arm to particularly smoothly the core stop when excessive variation.

[0002]

2. Description of the Related Art Generally, the core of a fast reactor is composed of a large number of fuel assemblies loaded with fissile material, and sodium is mainly used as a coolant for removing heat from fuel. Normally, sodium is not boiled by boiling, but in the unlikely event of an accident, it has been confirmed that the core can be safely shut down even if sodium is voided.

As a response when sodium is voided, when the reactor core is small, neutrons leak from the reactor core greatly, so that a negative reactivity enters and the reactor core shuts down safely. However, the larger the core, the less neutron leakage,
The reactivity when sodium is voided is positive, and it is necessary to confirm the safety by performing a detailed analysis including other reactivity factors to determine whether or not the core shuts down safely. Therefore, if the void reactivity of the reactor core can be reduced at the time of an accident, it is very valuable in terms of safety design.

Hereinafter, a conventional core component described above will be described with reference to FIG. In FIG. 5, a core component 11 constituting the core of the fast reactor has an outer portion formed by a trumpet tube 1 and an entrance nozzle 2 at a lower portion. A support plate 3 that supports a heating element 4 whose upper part is open is provided in the wrapper tube 1. A coolant channel 6 through which coolant flows is formed at the outer periphery of the support plate, and a coolant introduction hole 5 for guiding the coolant above the heating element 4 is formed at the center.

[0005]

The core components described above have an open end at the top of the heating element, and the generated voids are cooled by sodium in the upper plenum and shrinkage and re-expansion of the voids occur. Can cause. When the void shrinks, sodium may flow into the core position and have a positive reactivity.

The present invention has been made in view of such circumstances, and has as its object to provide a structure for suppressing sodium voids from contracting by the coolant in the upper plenum.

[0007] To achieve the above object, the present invention, the internal in core components of a fast reactor with pyrogenic substances other than the liquid metal is circulated and fissile material, the upper
The first is composed of the exothermic substance,
And the first cylindrical body which is open at the bottom and
The heat generating member is provided so as to surround the upper portion of the first cylindrical body which is spaced apart from the first cylindrical body.
A second cylindrical body for collecting air bubbles generated from the volatile substance.
Providing core elements of a fast reactor, characterized by Bei.

[0008]

In the core component of the fast reactor constructed as described above, when the exothermic substance evaporates the liquid metal to form a void, the void is captured by the void capturing structure disposed above. The neutrons generated in the core by the void leak in the vertical direction of the core, giving a negative reactivity effect to the core and increasing the safety.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention. A support plate 3 for holding a heating element 4 is disposed inside the wrapper tube 1 constituting the core component 20. The support plate 3 and the heating element 4 have a coolant introduction hole 5 that penetrates the support 3 and the heating element 4 and draws sodium into the heating element 4.
Are formed. An entrance nozzle 2 formed below the wrapper tube 1 introduces a coolant into the core component 20, and a coolant channel 6 that draws in sodium necessary for cooling the wrapper tube 1 is provided in the support plate 3. Are formed. A void capturing structure 7 is provided above the heating element 4 so as to surround the heating element 4. That is, as shown in FIG.
As shown, the heating element 4 is open at the
As a first cylindrical body made of a material, a void capturing structure
The body 7 is open at the bottom and separated from the first cylindrical body.
The exothermic substance provided surrounding the upper portion of the first cylindrical body;
As a second cylindrical body that collects air bubbles generated from the material.
Each is installed and has a double cylinder structure as a whole.
Further, the total amount of the heating element and the diameter of the coolant introduction hole 5 are set so that the sodium inside the heating element 4 is slightly lower than the boiling temperature of sodium during normal operation. The material of the heating element 4 is a heat- generating substance that generates heat when irradiated with γ-rays, and is other than a fissile substance. For example , hafnium or a hafnium alloy, tantalum, stainless steel can be mentioned up.

With the above configuration, the void generated in the heating element 4 starts to rise due to its own buoyancy, but is prevented from rising by the void capturing structure 7 provided on the heating element 4 and formed by the void. The space expands while extruding the coolant in the gap formed by the void capturing structure 7 and the heating element 4.

As a result, the core component 20 of the present embodiment allows the generated voids to remain in the assembly for a longer time than the conventional structure in which the upper portion of the heating element is open. The time period during which the void reactivity of the core is reduced or negative than that of the body can be increased.

The temperature of the void capturing structure 7 can be reduced by forming the void capturing structure 7 as a material equivalent to the heating element 4 or attaching a material equivalent to the heating element 4 inside the void capturing structure 7. The temperature can be higher than the sodium saturation temperature, and the captured voids can be maintained for a long time.

FIG. 2 is a longitudinal sectional view showing a modification of the first embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and
Is omitted.

In FIG. 2, a boiling promoting hole 8 is formed inside the heating element 4 to promote the boiling of sodium. The sodium in the boiling accelerating hole 8 is hardly affected by the sodium flowing inside the heating element, and can always maintain the saturated steam temperature. Therefore, when the flow rate of the coolant is reduced or the reactivity is inserted, sodium can be quickly boiled to generate voids.

FIG. 3 is a longitudinal sectional view showing a second embodiment of the present invention. In FIG. 3, the same portions as those in FIG. 1 are denoted by the same reference numerals, and the description of the configuration of the portions will be omitted. In FIG. 3, a structural material 9 having a coolant inflow hole 21 formed at the center thereof is installed at a position of a core region in the axial direction in the heating element 4. Therefore, the void ratio near the core center plane level is reduced, the void reactivity of the positive core is suppressed, and the void reactivity of negative sodium above the axial blanket can be efficiently used.

FIG. 4 is a longitudinal sectional view showing a third embodiment of the present invention. In FIG. 4, the same portions as those in FIG. 3 are denoted by the same reference numerals, and description of the configuration of the portions will be omitted. In FIG. 4, a structural material 9 containing a coolant 10 is provided at a position in the core region in the axial direction in the heating element 4. As coolant
Preferably, liquid metal is used. With this configuration, it is possible to suppress the void reactivity of the positive core near the core center plane level and efficiently utilize the void reactivity of negative sodium above the axial blanket. Becomes

The structure of the assembly of the fast reactor according to the present invention is not limited to the above example, but may be any structure that causes sodium voids in the assembly during an accident. For example, a configuration is possible in which a gas region is included in the aggregate and sodium is voided due to a decrease in internal pressure or the like.

[0018]

According to the present invention, the generation of voids in the preceding void channel can be promoted and the retention time can be increased, and the safety can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of core components of a fast reactor showing a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a main part showing a modification of the first embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of core components of a fast reactor showing a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of core components of a fast reactor showing a third embodiment of the present invention.

FIG. 5 is a longitudinal sectional view showing a conventional example of core components of a fast reactor.

[Explanation of symbols]

1 ... horn tube, 2 ... entrance nozzle, 3 ... support plate,
4 ... heating element, 5 ... coolant introduction hole, 6 ... coolant passage, 7 ...
Void trapping structure, 8 ... Boiling promotion hole, 9 ... Structural material, 10 ...
Coolant.

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Claims (4)

(57) [Claims] 1. A core component of a fast reactor having a heat generating substance other than a fissile substance through which a liquid metal flows therein, wherein an upper part of the core element is opened and formed of the heat generating substance.
A first cylindrical body to be opened, and the first
Second cylindrical collecting the bubbles spaced from the cylindrical body is provided so as to surround the upper portion of the first tubular member generated from <br/> the pyrogen
And a core component of the fast reactor. 2. The core component of a fast reactor according to claim 1, wherein a hole for promoting boiling is formed on an inner surface of said first cylindrical body . 3. A structure in which a structural material for suppressing void reactivity of a positive core is disposed at a position of an axial core region of the first tubular body. A core component of the described fast reactor. 4. The core component of a fast reactor according to claim 3, wherein a liquid metal used as a coolant is accommodated inside the structural material.