JPH0540197A - Refueling method for reactor - Google Patents

Abstract

PURPOSE:To veduce the reactor vessel diameter by providing upper core structure on a small rotary plug placed eccentrically on a large rotary plug placed eccentrically on a fixed plug and inserting a refueling machine instead of this mechanism when refueling. CONSTITUTION:Upper core structure UCS 30 is put on a small rotary plug 43. For refueling in the core, the cylindrical UCS part 31 of the UCS 30 is drawn out and instead, a special plug loading a refueling machine 50 is inserted. By extending an offset arm 51, a refueling gripper 52 is set on the position having an offset from the refueling machine 50. And the gripper 52 can access an arbitrary position in the access range in the core and grips and removes at the incore fuel relay position 53 by making use of the radius and rotation angle of the large rotary plug 42, those of plug 43, the offset of the refueling machine and arm 51 rotation angle and placing of each component. Thus, the escaping of the UCS 30 from immediately above the core is not necessary and so minimizing of the reactor vessel 40 diameter is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an improvement of a fuel exchange method of a system for exchanging fuel in a reactor under the lid without opening the entire lid (plug) for sealing the reactor vessel top of the fast breeder reactor. More specifically, the present invention relates to a method of exchanging fuel in a nuclear reactor that can reduce the diameter of the nuclear reactor vessel.

[0002]

2. Description of the Related Art FIG. 6 and FIG. 7 show examples of the internal structure of a reactor vessel during power operation of a fast breeder reactor. In the liquid sodium 2 as a coolant contained in the reactor vessel 1, a core 3 composed of fuel rods, control rods, reflectors, etc. which cause a nuclear thermal reaction.
A cylindrical core upper part mechanism (hereinafter abbreviated as UCS) 4 hangs from directly above the core 3. The top of the reactor vessel 1 is sealed with a lid, and the lid is composed of a fixed plug 5 and a rotatable rotary plug 6 placed eccentrically with respect to the fixed plug, and the UCS 4 is eccentrically attached to the rotary plug 6. It has been placed. Further, an in-reactor relay mechanism hole plug 7 is provided in a part of the fixed plug 5, and a fuel exchanger hole plug 8 is provided in a part of the rotary plug 6. U
The CS4 has a large number of control rod drive mechanisms and core upper part measuring instruments housed therein, and the control rod drive mechanism can adjust the position of the control rods in the core 3 to control the reactor power. With the above-mentioned configuration, sodium 2 can be circulated through the pipe (not shown) connected to the reactor vessel 1 to take out the nuclear reaction heat.

Even in a fast breeder reactor, it is necessary to periodically replace the core fuel and the like, but liquid sodium as a coolant is chemically very active and has the property of burning out when it comes into contact with air. There is. Therefore, it is necessary to perform the fuel refueling work inside the reactor under the lid by opening the minimum lid while shutting off the outside air without opening the entire lid at the top of the reactor vessel. This is called the under the plug method because it is performed.

Refueling work in the reactor by this system will be described with reference to FIGS. 8 and 9 corresponding to FIGS. 6 and 7. In the refueling work, first, the in-reactor relay mechanism hole plug 7 and the fuel exchanger hole plug 8 in FIG. 6 are removed while avoiding contact with the outside air, and the in-reactor relay mechanism 9 and the fuel exchanger 10 are inserted and installed in the holes, respectively. To do. The in-reactor relay mechanism 9 has a structure in which a rotating disk 11 is provided at the lower end of a cylinder, and the rotating disk 11 has two holes for hanging a fuel transfer pot 12 for receiving new and old fuel. The rotary disk 11 enables relay transfer of the fuel 13 between the fuel exchanger 10 and a fuel inlet / outlet machine (not shown). The refueling machine 10 is provided with an offset arm 14 for giving an offset amount L from the main body, the offset arm 14 is capable of turning (θ), and a gripper 15 for gripping / releasing fuel is provided at the tip thereof. ing. Further, the main body of the fuel exchanger 10 can move up and down so that the fuel 13 can be extracted and inserted from the core 3 and the in-core relay mechanism 9, and the offset arm 14 can be folded when the fuel exchanger 10 is inserted into and extracted from the reactor. There is.

Next, in order to position the fuel exchanger 10 above the core 3, the rotary plug 6 on which the fuel exchanger is mounted is rotated (θ '). This inevitably causes the UCS 4 to be retracted from above the core, while the refueling machine 10 body is provided with a rotation angle of radius R with respect to the center of rotation of the rotating plug 6. Thus, the gripper 15 of the refueling machine 10
From the viewpoint, it becomes possible to access the fuel at any position (address) of the core 3 by the combination of θ and θ ′ within the access region in the reactor defined by L, R, θ and θ ′.

The operation of each of the above-described devices at the time of refueling work will be described step by step as follows. 1) Refueling machine gripper 15 directly above the fuel to be replaced
The rotating plug 6 is rotated and the refueling machine offset arm 14 is swung so that the position is positioned. (The UCS 4 is retracted from above the core 3 by the rotation of the rotary plug 6.) 2) The main body of the fuel exchanger 10 is lowered, and the spent fuel is grasped by the claws at the tip of the fuel exchanger gripper 15. 3) The main body of the refueling machine 10 is lifted up, and the spent fuel that is grasped is pulled out from the core 3. 4) Rotating plug 6 and refueling machine offset arm 14
Is rotated, the spent fuel 13 is transferred to above the fuel transfer pot 12 in one hole of the rotary disk 11 of the in-core relay mechanism 9, the main body of the fuel exchanger 10 is lowered, and the spent fuel 13 is released. 10 Lift the main body and wait at that position. 5) At this time, inside the cylinder of the in-reactor relay mechanism 9, a gripper of a fuel inlet / outlet machine (not shown) holds the fuel transfer pot 12 containing new fuel and stands by. 6) Rotating disc 1 so that the vacant hole of rotating disc 11 of in-reactor relay mechanism 9 is directly below the fuel gripper gripper.
Turn 1 to insert the fuel transfer pot 12 containing the new fuel into the empty hole of the rotating disk 11. Raise the fuel entry / exit gripper slightly. 7) Rotate the rotating disk 11 so that the fuel transfer pot 12 of the in-reactor relay mechanism 9 containing the new fuel is directly below the fuel exchanger gripper 15. 8) The new fuel is gripped by the refueling machine gripper 15 and loaded at a predetermined address of the core 3 in the reverse order of the above. 9) The rotating disk 11 is rotated so that the spent fuel is directly below the fuel inlet / outlet gripper, and the fuel transfer pot 12 containing the spent fuel is lifted by the fuel inlet / outlet gripper.
Transfer to the outside of the reactor vessel 1.

[0007]

By the way, in order to rationalize the fast breeder reactor in the future, how to downsize the reactor vessel in comparison with the size of the core becomes very important. There is. Focusing on the diameter of the reactor vessel, there are two main determinants. One is the size of the character that is determined by the size of the core and the total size of the internal structures (for convenience, it is called the "core inside size").
One is a dimension determined by the constraint on the fuel exchange system by the under-the-plug method that the UCS having the same dimension as the core fuel region must be evacuated from above the core (for convenience, "the dimension determined on the plug side" ”)
Is.

The "plug-side determined dimension" will be briefly described. If the diameter of the core fuel region is d and the UCS diameter is also d (see FIG. 11), the diameter of the reactor vessel of the axisymmetric cylindrical structure is naturally Since the center of the reactor core is placed at the center of the reactor vessel, a dimension of 2d to 3d or more is required. Actually, in addition to the above-mentioned restriction of the theoretical size, the width of the bearing of the rotary plug, the plate thickness of each structure, the tightening margin of the bolt, the thermal insulation thickness, etc. are also added to determine the “plug-side determination size”. ..

Further, the above-mentioned "reactor inside dimension" is the same as that for designing a loop type fast breeder reactor for the purpose of power generation.
Since it can be designed to be smaller than the "plug-side determined dimension", the "plug-side determined dimension" is the deciding factor of the reactor vessel diameter in the end. By the way, in the case of a loop type fast breeder reactor with a UCS diameter of 3360 mm, which is being designed by the applicant of the present application, the Power Reactor and Nuclear Fuel Development Corporation, the “reactor inside dimension” is about 8.4 m. Thus, the “plug-side determined dimension” becomes 9.2 m to 12.6 m when calculated for various variations of the under-the-plug fuel exchange system.

Therefore, the present invention is based on the "determined dimension on the plug side".
The present invention aims to provide a novel method for refueling fuel in a nuclear reactor, which can eliminate the above-mentioned from the determinants of the diameter of the nuclear reactor vessel, and thereby reduce the diameter of the nuclear reactor vessel.

[0011]

The inventors of the present invention have formed a UCS portion that can be pulled out in the vertical direction inside a conventional UCS mounted on a rotary plug as described above, and this UCS portion is used at the time of fuel exchange in the reactor. This invention has been completed by focusing on the fact that it is not necessary to evacuate the entire UCS from directly above the core at the time of refueling by redrawing the part and inserting a fuel exchanger into the extracted part for refueling. ..

That is, according to the method of refueling in a nuclear reactor of the present invention, a fixed plug, a rotatable large rotation plug eccentrically mounted on the fixed plug, and an eccentric mounting on the large rotation plug. A UCS having a large number of control rod drive mechanisms is mounted on the small rotation plug of the reactor vessel top lid having a rotatable small rotation plug.
A removable UCS part is formed in the inside of the reactor, and at the time of fuel exchange in the reactor, the UCS part is withdrawn, and a fuel exchange machine equipped with a swivelable offset arm is inserted and installed in the extracted part, and a large rotation plug and It is characterized in that the fuel replacement work at an arbitrary position in the core is performed by the rotary motion of the small rotary plug and the turning motion of the offset arm of the refueling machine.

The present invention can be applied to a case where a direct-acting type fuel exchanger is used in addition to the offset arm type fuel exchanger. The direct drive type fuel exchange machine is a type of fuel exchange machine in which a gripper is directly attached to the tip of a cylindrical fuel exchange machine body and does not have an offset amount. In this case, the UCS is rotatably mounted on the small rotary plug, and the retractable UCS portion inside the UCS is formed eccentrically from the UCS center. At the time of refueling in the reactor, a direct-acting fuel exchange machine is inserted and installed after pulling out the extractable UCS part, and the rotary motion of the large rotary plug and the small rotary plug and the rotary motion of the UCS allows the arbitrary position in the core. The fuel replacement work can be performed.

[0014]

According to the method of the present invention as described above, it is not necessary to retract the UCS from immediately above the core at a distance in the radial direction of the reactor vessel at the time of refueling, and in the state where the UCS is installed directly above the core, It becomes possible to perform internal fuel exchange. As a result, the above-mentioned "plug-side deciding dimension" can be excluded from the determinants of the reactor vessel diameter, and the reactor vessel diameter can be designed substantially only by the "reactor inside deciding dimension", thus reducing the reactor vessel diameter. Can be planned.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. Figure 1 shows a concrete core matrix,
In each case, a fuel rod having a hexagonal cross section, a shield, and a control rod are arranged at predetermined positions. In the drawing, the hexagons drawn with thick lines represent the positions of the control rods (main furnace stop system control rods and secondary furnace stop system control rods) 20. The circle overlaid on the core matrix represents the diameter of the UCS 30, and the area within this circle is approximately equal to the area to be refueled. The circle shown in the circle of the UCS 30 represents the diameter of a vertically-drawable cylindrical UCS portion 31 formed inside the UCS. The formation position and size of the UCS portion 31 are determined in consideration of the control rod arrangement in the core matrix and the offset arm type fuel exchanger size. In the example shown, the diameter of the UCS 30 is 3.36 m, the diameter of the UCS portion 31 inside this UCS is 1.75 m,
The S portion 31 includes nine control rod drive mechanisms corresponding to nine control rods.

FIG. 2 illustrates the relationship between the UCS 30 shown in FIG. 1 and the withdrawable cylindrical UCS portion 31 formed therein. Since the UCS portion 31 is formed inside the UCS, the UCS 30 It can be seen that the outer shape of (1) maintains the same cylindrical shape as the conventional one. Like this UC
Since the outer shape of S does not change, the design such as the distribution of the coolant flow rate in the reactor vessel can be performed as in the conventional case.

FIG. 3 is a plan view showing a state where the UCS 30 having the UCS portion 31 formed therein is placed on the lid on the top of the reactor vessel. That is, on the fixed plug 41 of the reactor vessel 40, a large rotation plug 42, which is designed to be rotatable and whose center position is different from the center of the reactor vessel, is placed. On the large rotation plug 42, a small rotation plug 43, which is rotatably designed with its center position different from the center of the large rotation plug, is placed. U for this small rotation plug 43
CS30 is mounted.

At the time of refueling in the reactor, the cylindrical UCS
The portion 31 is pulled out, and a dedicated plug equipped with the fuel exchanger 50 with the offset arm 51 folded is inserted into the pulled-out portion, and when the offset arm 51 is extended after the fuel exchanger is inserted, the fuel exchanger gripper 52 causes the fuel to move. The switch 50 is set at a position having an offset amount with respect to the main body. In the illustrated example, since the offset length of the offset arm 51 is set within the diameter of the UCS portion 31, the offset arm 51 does not necessarily have to be foldable. The offset arm 51 is the refueling machine 5.
It is provided so as to be turnable with respect to zero. Thus, the refueling machine gripper 52 uses the radius and rotation angle of the large rotation plug 42, the radius and rotation angle of the small rotation plug 43, the offset amount of the refueling machine 50 and the swing angle of the offset arm 51, and the mounting position of each device. It is possible to arbitrarily access the inside of the access range (circle of alternate long and short dash line) in the furnace, and the gripper 52 at the fuel relay position 53 in the furnace
The fuel can be gripped and released by.

In the illustrated example, the radius of the fuel exchange target region of the core is 1.68 m, and the fuel relay position 53 is 2.
45 m, the diameter of the large rotation plug 42 is 5.6 m, the diameter of the small rotation plug 43 is 4.1 m, and the diameter of the UCS 30 is 3.3.
6 m, the diameter of the UCS part 31 is 1.75 m, the offset amount of the refueling machine 50 is 0.7 m, and the fuel can be handled between any refueling address in the reactor and the fuel relay position 53. Can understand. In FIG. 3, the state where the fuel exchanger gripper 52 is accessing the fuel relay position 53 is shown by a dotted line. In the figure, reference numeral 54 indicates an in-reactor relay mechanism, and reference numerals 55 and 56 indicate an inlet pipe and an outlet pipe of liquid sodium as a coolant, respectively.

FIG. 4 is a vertical cross-sectional view showing the state in which the top cover structure of FIG. 3 is mounted on a reactor vessel. The same members as those in FIG. That is, as described above, at the time of fuel refueling in the reactor, the cylindrical U inside the UCS 30 having a large number of control rod drive mechanisms 57 incorporated therein.
The CS portion 31 is pulled out by a dedicated handling machine, and a plug having a refueling machine 50 equipped with a foldable offset arm 51 is inserted into the pulled-out portion. Next, when the offset arm 51 of the refueling machine 50 is extended below the plug, the gripper 52 can be turned with respect to the body of the refueling machine 50 with an offset amount.

In this way, the fuel exchange gripper 52
Can arbitrarily access between the refueling target region and the fuel relay position 53 by the turning motion of the offset arm 51 and the rotary motions of the large rotation plug 42 and the small rotation plug 43. The accessed fuel 59 is gripped by the fuel exchanger gripper 52, transferred to the fuel relay position 53, and put in the fuel transfer pot 60. Next, after the fuel transfer pot 60 is tilted toward the peripheral wall of the reactor vessel 40,
Fuel is extracted through the in-reactor relay mechanism 54. The introduction of new fuel into the reactor may be performed in the reverse order of the above.

By the way, the in-reactor relay mechanism 54 for mating with a fuel inlet / outlet (not shown) for transferring fuel outside the reactor,
Due to the design of the fuel inlet / outlet device, it is advantageous to place it on the fixed plug 41 whose coordinate position does not change due to the rotation of the rotary plug. Also, the in-reactor fuel relay position 53 should be as close to the core 5 as possible.
It is advantageous to bring it closer to 8 areas because the rotating plug can be designed smaller. Therefore, as shown in FIG. 3 and FIG. 4, a distance is generated in the radial direction of the reactor vessel 40 between the installation position of the in-reactor relay mechanism 54 and the fuel relay position 53. It is unreasonable to absorb this distance with such a rotating disk 11. Therefore, as described with reference to FIG. 4, the in-reactor relay mechanism of the type in which the fuel transfer pot 60 for accommodating the fuel is tilted is adopted. In order to absorb the distance between the in-reactor relay mechanism 54 and the fuel relay position 53, in addition to the method of tilting the fuel transfer pot 60 shown in the figure, a method of using a link mechanism such as pantograph power supply of a train, or an upright position. Various methods such as a method of sliding the fuel transfer pot sideways can be adopted.

FIG. 5 illustrates an embodiment of the present invention when a direct drive type fuel exchanger is used. In the figure, the same members as those in the embodiment of FIG. In the embodiment shown in FIG. 5, the retractable cylindrical UCS portion 33 formed eccentrically inside the UCS 32 is withdrawn, and after the withdrawal, the direct drive type fuel exchanger 70 is inserted and installed. In addition, the UCS 32 is a small rotation plug 4 that can be freely rotated.
It is placed at 3. Thus, the gripper 71 of the direct drive type refueling machine 70 has the radius and rotation angle of the large rotation plug 42,
Radius and rotation angle of small rotation plug 43, rotation UCS32
Angle of rotation, and the rotation UCS of the direct drive type fuel exchanger 70
By the amount of eccentricity with respect to the center of 32, it is possible to arbitrarily access the inside of the access range (circle of alternate long and short dash line) in the reactor, and it is possible to grip and release the fuel by the gripper 71 at the in-reactor fuel relay position 53. Of. In Figure 5,
The gripper 71 of the direct drive type refueling machine 70 has the fuel relay position 5
The state in which 3 is being accessed is indicated by a dotted line.

In the illustrated example, the radius of the refueling target area of the core is 1.68 m, and the fuel relay position 53 is 2.
45 m, the diameter of the large rotation plug 42 is 6.3 m, the diameter of the small rotation plug 43 is 4.5 m, the diameter of the rotary UCS 32 is 3.36 m, and the eccentric installation amount of the direct drive type fuel exchanger 70 with respect to the center of the rotation UCS 32 is 1.04 m. It was drawn as, and any fuel exchange address and fuel relay position 5 in the furnace
It can be understood that the fuel can be handled between the 3 and the above.

When using a direct drive type fuel exchanger,
The diameter of the retractable cylindrical UCS portion 33 formed inside the UCS 32 can be made smaller than that of the offset arm type fuel exchanger. Therefore, a UCS that can be pulled out to a portion that does not include the control rod drive mechanism inside the UCS 32
Since it is also possible to form the portion 33, the structure of the UCS portion that can be pulled out is facilitated, and since it is light in weight, there is an advantage that it can be easily pulled out.

[0026]

As described above, according to the present invention, it is not necessary to evacuate the UCS from directly above the core at the time of fuel refueling in the reactor.
The size of the reactor vessel does not have to be 2 to 3 times the diameter or more, and the reactor vessel can be downsized, and the plant construction cost can be significantly reduced.

Incidentally, the UCS diameter as described above is 33
When this invention is applied to a 60 mm loop reactor,
The "plug-side determined dimension" is 5.6 to 6.3 m even with the outer diameter dimension of the large rotation plug, which is sufficiently smaller than the "reactor inner-side determined dimension" of 8.4 m. The “plug-side determinant” can be excluded from the determinants, and the reactor vessel diameter can be determined only by the “reactor-inner determinant”.

It is also conceivable to pull out the entire UCS at the time of refueling in the furnace and insert a plug on which a refueling machine is mounted into this pulled out portion. However, in this case, a large diameter UCS handling cask is required. For this reason, a large amount of inert gas is required to replace the gas in the cask when extracting the entire UCS. On the other hand, according to the present invention, since it is only necessary to handle the UCS split body, there is an advantage that the handling cask and the fuel exchanger casing can be downsized and the inert gas consumption amount can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a core matrix, a UCS diameter, and a diameter of a drawable UCS portion.

FIG. 2 is a perspective view showing a relationship between the UCS outer shape shown in FIG. 1 and a retractable UCS portion formed inside thereof.

FIG. 3 is an explanatory view showing the arrangement of a reactor vessel top cover and an offset arm type fuel exchanger at the time of refueling in the reactor.

FIG. 4 is a diagram showing a case where the reactor vessel lid of FIG. 3 is mounted on a reactor vessel,
FIG. 3 is a cross-sectional view of a reactor vessel showing a state in which the refueling method of the present invention is being performed.

FIG. 5 is an explanatory view showing the arrangement of a reactor vessel top cover and a direct-acting type fuel exchange machine at the time of refueling in the reactor.

FIG. 6 is an explanatory view showing the positional relationship of UCS in the nuclear reactor during the output operation of the conventional fast breeder reactor.

7 is a sectional view taken along the line AA of FIG.

FIG. 8 is an explanatory diagram showing a positional relationship of UCS and the like in a nuclear reactor at the time of fuel exchange in the conventional fast breeder reactor.

9 is a sectional view taken along the line BB of FIG. 30, 32 ... Upper core mechanism (UCS), 31, 33 ... Extractable UCS part, 40 ... Reactor vessel, 41 ... Fixed plug, 42 ... Large rotation plug, 43 ... Small rotation plug, 50 ... Offset arm fuel exchange machine , 51 ... Offset arm, 70 ... Direct-acting type fuel exchanger.

Claims (2)

[Claims] 1. An atom having a fixed plug, a rotatable large rotation plug eccentrically mounted on the fixed plug, and a rotatable small rotation plug eccentrically mounted on the large rotation plug. On the small rotation plug of the top lid of the reactor vessel, an upper core mechanism having a large number of control rod drive mechanisms is placed, and a retractable upper core mechanism portion is formed inside the upper core mechanism, and in-core fuel exchange is performed. In some cases, the upper core mechanism part is pulled out, and a fuel exchange machine equipped with a swivelable offset arm is inserted and installed in the pulled out part, the rotary motion of the large rotation plug and the small rotation plug and the rotation of the offset arm of the fuel exchange machine are swung. A method for refueling in a nuclear reactor, characterized in that the fuel is refueled at an arbitrary position in the core by exercise. 2. An atom having a fixed plug, a rotatable large rotation plug eccentrically mounted with respect to the fixed plug, and a rotatable small rotation plug eccentrically mounted with respect to the large rotation plug. A core upper part mechanism having a large number of control rod drive mechanisms is rotatably mounted on the small rotation plug of the top cover of the reactor vessel, and a core upper part mechanism part that can be pulled out is inside the core upper part mechanism. Formed eccentrically from the center,
At the time of fuel refueling in the reactor, the core upper mechanism part is pulled out, and in the extracted portion, a direct-acting fuel exchange machine is inserted and installed, and by the rotary motion of the large rotary plug and the small rotary plug and the rotary motion of the core upper mechanism, A method for refueling an in-reactor, comprising performing a fuel exchange operation at an arbitrary position in the core.