JP6668747B2 - Fuel recovery method - Google Patents

Description

  The present invention relates to a fuel recovery method.

  As is well known, nuclear power plants generate electricity by burning nuclear fuel in nuclear reactors. A nuclear reactor generally includes a reactor pressure vessel and a reactor containment vessel, and nuclear fuel is stored as a plurality of fuel rods in the reactor pressure vessel, and the control fuel is stored in the reactor pressure vessel together with the fuel rods. The rod controls the nuclear reaction.

  Patent Literature 1 below discloses a technique for recovering nuclear fuel (fuel debris) from a reactor pressure vessel when the reactor is in a severe accident state. In such a case, the so-called “submergence method”, that is, a method of recovering fuel debris in a state where the influence of radioactivity is reduced by immersing the reactor pressure vessel in water, is adopted. In the technology, a hollow body containing a radiation shielding material in place of water is filled into the reactor pressure vessel and the reactor containment vessel, and in this state, a workbench provided above the reactor pressure vessel is used to fill the reactor pressure vessel. The fuel debris is cut and collected by inserting a cutter into the fuel cell.

JP 2014-109444 A

  In the technique of Patent Document 1 described above, since the cutting and collection of the fuel debris is performed in a state where the hollow body is filled, the hollow body obstructs the insertion of the cutter into the reactor containment vessel, and the insertion of the cutter makes the hollow. There is a problem that the body is damaged.

  The present invention has been made in view of the above circumstances, and has as its object to recover radioactive fuel from a reactor pressure vessel or a reactor containment vessel while reducing leakage of radioactivity in the air.

  In order to achieve the above object, according to the present invention, as a first solving means according to a fuel recovery method, radioactive fuel remaining in a reactor pressure vessel and / or a containment vessel is supplied to the nuclear reactor via a predetermined arrival path. A method for recovering fuel from a reactor pressure vessel and / or a containment vessel, comprising: a first shielding means setting step of providing an openable and closable first radioactive shielding means on the arrival path; A second shielding means setting step of providing an openable and closable second radiation shielding means, wherein said first and second radiation shielding means are opened and closed under different conditions. Adopt means.

  In the present invention, as a second solving means according to the fuel recovery method, in the first solving means, the first radioactive shielding means comprises a plurality of sliding doors sliding in a direction intersecting the arrival path. The second radiation shielding means includes a plurality of pivoting doors pivoting about a pivot axis in a direction intersecting the arrival path.

  According to a third aspect of the present invention, as the third aspect of the fuel recovery method, in the first or second aspect, the arrival path is via a shielding plug provided on an operation floor of a reactor building. The first radioactive ray shielding means and the second radioactive ray shielding means adopt a means in which an opening is provided in the shielding plug or the shielding plug is removed and provided.

  According to a fourth aspect of the present invention, as a fourth aspect of the fuel recovery method, in the third aspect, an apparatus necessary for recovering the radioactive fuel is provided from the operation floor to the first radioactive shielding means and the second Means for recovering the radioactive fuel by drooping through the radioactive shielding means.

  According to a fifth aspect of the present invention, as the fifth aspect of the fuel recovery method, in the third or fourth aspect, a shielding wall is constructed on the operation floor so as to surround a space around the shielding plug. Means to collect the data.

  According to the present invention, the first radioactive ray shielding means and the second radioactive ray shielding means open and close under different conditions, so that the reactor pressure vessel and the reactor containment vessel can be reduced while reducing the leakage of radioactivity in the air. It is possible to recover radioactive fuel.

FIG. 1 is a cross-sectional view illustrating a reactor in a severe accident state according to an embodiment of the present invention. It is sectional drawing (a) which shows the shield plug removal process of the fuel recovery method which concerns on one Embodiment of this invention, sectional drawing (b) which shows a shield port installation process, and front view (c). It is sectional drawing (a) and front view (b) which show the shielding cover installation process of the fuel collection method concerning one Embodiment of this invention. FIG. 2 is a cross-sectional view illustrating a state in which fuel debris (radioactive fuel) is recovered from a reactor pressure vessel using the fuel recovery method according to one embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a state in which fuel debris (radioactive fuel) is recovered from a containment vessel using the fuel recovery method according to one embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The reactor is provided in a reactor building 1 as shown in FIG. 1, and includes a reactor containment vessel 2, a reactor base 3, a biological shield wall 4, a shield plug 5, a pedestal 6, a reactor pressure vessel. 7, a suppression chamber 8, an overhead crane 9, and the like. The reactor building 1 is a concrete structure that accommodates each of the above-described components that constitute the reactor.

  The containment vessel 2 is a closed vessel (steel vessel) that functions as a radiation barrier and a pressure barrier. The containment vessel 2 has a vertically long shape as a whole, and houses the substantially containment vessel 2 in a vertical posture.

  The reactor base 3 is a concrete structure that is provided underground and near the center of the reactor building 1 and supports the containment vessel 2. The living body shielding wall 4 is a concrete structure provided around (outer periphery of) the containment vessel 2. The shielding plug 5 is a detachable concrete structure constructed above the reactor containment vessel 2, that is, on the operation floor 1a of the reactor building 1. This shielding plug 5 is composed of three concrete slabs, that is, a first plug 5a, a second plug 5b, and a third plug 5c.

  That is, the steel reactor containment vessel 2 is supported in a state where the outer periphery is covered by the reactor base 3, the living body shielding wall 4 and the shielding plug 5 made of concrete. The space surrounded by the living body shielding wall 4, the shielding plug 5, and the upper part (upper lid) of the reactor containment vessel 2 is a reactor well R.

  The pedestal 6 is a concrete structure provided inside the reactor containment vessel 2 and upward from the lower part. The reactor pressure vessel 7 is a sealed vessel (steel vessel) housed in the reactor containment vessel 2 above the pedestal 6 and functioning as a radiation barrier and a pressure barrier. Although not shown, a plurality of fuel rods and control rods are usually housed in the reactor pressure vessel 7.

  The suppression chamber 8 is a vessel provided in an annular shape (ring shape) around the containment vessel 2. The suppression chamber 8 is provided under the reactor building 1 at an outer periphery of the reactor base 3, that is, at a position corresponding to a lower portion in the height direction of the containment vessel 2. The overhead crane 9 is a transport device for transporting the maintenance device, the shielding plug 5, and the like.

  Here, due to the occurrence of the severe accident, the fuel debris X remains at the bottom of the reactor pressure vessel 7 and / or the containment vessel 2. The fuel debris X is a mass of nuclear fuel (radioactive fuel) in which a plurality of fuel rods have once melted and then solidified.

  Now, with respect to the reactor in such a state, in the fuel recovery method according to the present embodiment, the fuel debris X (radioactive fuel) is supplied to the reactor pressure vessel 7 and / or the reactor pressure vessel 7 via a path passing through the shielding plug 5. Collected from the containment vessel 2. That is, in the present embodiment, a route that passes through the shielding plug 5 is selected as an arrival route (access route) to the fuel debris X for collecting the fuel debris X.

  As the above-mentioned reaching route, in addition to the route passing through the shielding plug 5, for example, a route in which an opening is formed in the living body shielding wall 4 and the fuel debris X reaches from the opening can be considered. On the other hand, the shielding plug 5 is inherently constructed so as to be removable, and the operation floor 1a having a horizontal and relatively large area is present around the periphery, so that the reaching route via the shielding plug 5 is This is a path through which work for collecting fuel debris X can be performed with good workability.

  The reaching route via the shielding plug 5 is such that the bottom of the reactor pressure vessel 7 and / or the reactor containment vessel from the shielding plug 5 via the upper lid of the reactor containment vessel 2 and the upper lid of the reactor pressure vessel 7. 2 reaches the fuel debris X remaining at the bottom. That is, the reaching route to the fuel debris X in the present embodiment is a route extending in the vertical direction (up-down direction).

  In the first step of removing the first shielding plug, as shown in FIG. 2A, a part of the shielding plug 5 provided on the operation floor 1a is removed. That is, of the three concrete slabs (the first plug 5a, the second plug 5b, and the third plug 5c) constituting the shielding plug 5, a part of the first plug 5a and the second plug 5b (a portion near the center) is removed. Remove it. Due to the partial removal of the second plug 5b, a circular opening K (shield plug opening) is formed near the center of the second plug 5b.

  Subsequently, in the shielding port installation step, the shielding port 10 is installed on the shielding plug opening K. The shielding port setting step is a first shielding means setting step in the present embodiment, and the shielding port 10 is a first radioactivity shielding means. As shown in FIGS. 2B and 2C, the shielding port 10 includes a main body 10a and a pair of sliding doors 10b and 10b. The main body 10a is a flat member having a circular opening 10c, and is fixed on the remaining shielding plug 5. The pair of sliding doors 10b, 10b are flat members provided on the main body 10a in a horizontal posture, and close / open the opening 10c by sliding in the horizontal direction as shown by arrows.

  That is, the pair of slide doors 10b and 10b open and close the arrival path by sliding in a direction intersecting (perpendicular to) the above-described arrival path. Such a pair of slide doors 10b, 10b are supported by, for example, a pair of rails laid on the surface of the main body 10a so as to be freely movable in the horizontal direction. In addition, such a pair of sliding doors 10b and 10b move horizontally by a driving function (not shown).

  Subsequently, in a shielding cover installation step, the shielding cover 11 is installed on the shielding port 10. The shielding cover setting step is a second shielding means setting step in the present embodiment, and the shielding cover 11 is a second radiation shielding means. As shown in FIGS. 3A and 3B, the shielding cover 11 is a metal member having a circular flat plate shape as a whole, and includes an outer peripheral base 11a and an inner peripheral opening / closing portion 11b. The outer peripheral base 11a is an annular (ring-shaped) metal member, and an inner peripheral opening / closing part 11b is provided inside. The inner peripheral opening / closing part 11b is constituted by a plurality of pivoting doors 11c, and is rotatably mounted on the outer peripheral base 11a.

  As shown in FIG. 3B, the plurality of pivoting doors 11c have a shape obtained by dividing an inner peripheral space (circular space) of the outer peripheral base 11a at predetermined angles with reference to the center of the inner peripheral space. ing. That is, the inner peripheral space of the outer peripheral base 11a is occupied by the plurality of rotating doors 11c. Further, as shown by the phantom line in FIG. 3A, such a rotating door 11c is rotatably mounted on the outer peripheral base 11a with a connection portion (arc portion) with the outer peripheral base 11a as a fulcrum. ing. That is, the plurality of rotating doors 11c open and close the arrival path by rotating about a rotation axis that intersects (perpendicularly) with the extending direction (vertical direction) of the above-described arrival path.

  Such a rotating door 11c is connected to the outer peripheral base 11a by, for example, an urging spring and a hinge (hinge) to maintain a horizontal state as a reference posture as shown by a solid line in FIG. Further, when receiving a pressing force from below or above, these turning doors 11c turn so as to tilt upward or turn downward as shown by the phantom line in FIG. I do. Although the details will be described later, such a shielding cover 11 opens and closes under conditions different from those of the shielding port 10 because the mechanism (structure) of the shielding cover 11 is different from that of the shielding port 10.

  Further, a plurality of openings 11d through which the lifting cable of the trolley 13a and the supporting cable of the lower platform 14b shown in FIG. 4 are inserted, and a crushing tool 13b attached to the tip of the lifting cable are provided at predetermined positions of the inner peripheral opening / closing section 11b. And a plurality of openings 11e through which a power supply cable for supplying electric power, a control signal, and the like to the collection device 14c attached to the lower platform 14b is formed.

  According to the shielding cover 11 configured as described above, the crushing tool 13b, the collecting container 13c, and the lower platform 14b shown in FIG. 4 can be passed, and the crushing tool 13b, the collecting container 13c, and the lower platform 14b can pass therethrough. In a desired state, the communication between the reactor well R and the shielding room S can be cut off. The operation and effect of the shielding cover 11 will be described later in detail.

  Subsequently, in the facility preparation step, as shown in FIG. 4, a cubic (box-shaped) shielding wall 12 is constructed on the operation floor 1a so as to surround the space around the shielding port 10. The shielding wall 12 is made of a material capable of shielding radioactivity, and an internal space, that is, a space around the shielding port 10 forms a shielding room S. One wall surface of the shielding wall 12 is constructed as an opening / closing shielding door 12a. That is, the shielding room S is a closed space when the shielding door 12a is closed, and communicates with the external space when the shielding door 12a is opened.

  In the shield room S, a cargo handling device 13 and a suspension device 14 are provided. The cargo handling device 13 and the suspension device 14 are devices necessary for collecting the fuel debris X, and are configured to be able to advance and retreat with respect to the shielding room S. Note that the cargo handling device 13 and the suspension device 14 are accommodated in the shielding room S during the collection operation of the fuel debris X, and move to the side of the shielding room S via the shielding door 12a during the non-recovery operation such as maintenance. . For example, a pair of rails are laid from the side of the shielding wall 12 to the inside of the shielding wall 12, and the cargo handling device 13 and the suspension device 14 move into and out of the shielding room S by traveling on the rail. .

  The cargo handling device 13 is, for example, a portal gantry crane provided with a plurality of trolleys 13a, and each trolley 13a is provided with a crushing tool 13b and a collection container 13c. The cargo handling device 13 moves the crushing tool 13b and the collection container 13c in the horizontal and vertical directions via the trolley 13a.

  The suspension device 14 includes an upper platform 14a, a lower platform 14b, and a collection device 14c. The upper platform 14a is an annular steel structure having an opening at the center, and includes an elevating device for elevating the lower platform 14b. The lower platform 14b is a ring-shaped (ring-shaped) metal member supported by the upper platform 14a so as to be able to move up and down via the elevating device.

  The lower platform 14b is supported by the upper platform 14a so as to move up and down in a posture where the central axis is vertical, that is, in a horizontal posture. The collecting device 14c is mounted below the lower platform 14b in such a horizontal posture, and stores the fuel debris X in the collecting container 13c.

  Next, in the second shield plug removing step, as shown in FIG. 4, the cargo handling device 13 and the suspension device 14 prepared in the recovery facility preparing step are remotely operated to control the third plug facing the shield plug opening K. The part near the center of 5c is removed. As a result, the reactor well R is in communication with the shielded room S.

  Further, in the upper cover removing step, the upper cover of the reactor containment vessel 2 and the upper cover of the reactor pressure vessel 7 are removed by remotely controlling the cargo handling device 13 and the suspension device 14 in the closed shielded room S. As a result, the shielded room S, the reactor well R, and the inside of the reactor pressure vessel 7 are in communication with each other. That is, in the upper lid removing step, the upper lid is crushed by the crushing tool 13b, and the crushed material generated at the time is collected in the shielding chamber S using the collection container 13c and the collection device 14c.

  In the first fuel recovery step following the top cover removal step, the crushing tool 13b is lowered to the bottom of the reactor pressure vessel 7 by the loading and unloading device 13, so that the fuel rods are melted into a lump of fuel debris X. Crushed finely. Then, by lowering the recovery container 13c and the recovery device 14c to the bottom of the reactor pressure vessel 7 by the cargo handling device 13 and the suspension device 14, the fuel debris X fined by the crushing is sequentially recovered in the shielding chamber S. In the first fuel recovery step, all the fuel debris X present at the bottom of the reactor pressure vessel 7 is recovered in the shielding room S.

  Here, the fuel debris X generated by the melting of the fuel rods is not only at the bottom of the reactor pressure vessel 7 but also partially at the bottom of the reactor containment vessel 2 by melting the bottom of the reactor pressure vessel 7. May be present. The following second fuel recovery step is performed to recover the fuel debris X also existing at the bottom of the reactor containment vessel 2.

  That is, in the second fuel recovery step, the crushing tool 13b crushes the crushing tool 13b and the recovery vessel 13c at the bottom of the reactor pressure vessel 7 and the portion of the lower platform 14b that obstructs the passage of the lower platform 14b to the bottom of the reactor containment vessel 2. At the same time, the crushed material generated by the crushing is collected in the shielding room S using the collection container 13c and the collection device 14c. This allows the crushing tool 13b, the recovery vessel 13c, and the lower platform 14b to pass through to the bottom of the containment vessel 2.

  Then, in the second fuel recovery step, the crushing tool 13b is lowered to the bottom of the reactor containment vessel 2 by the cargo handling device 13, and the fuel debris X present at the bottom of the reactor containment vessel 2 is crushed. The crushed fuel debris X is sequentially collected in the shielding room S by lowering the collection container 13c and the collection device 14c to the bottom of the containment vessel 2 by the cargo handling device 13 and the suspension device 14. In the second fuel recovery step, all the fuel debris X existing at the bottom of the containment vessel 2 is recovered in the shielded room S.

  In the above-described upper cover removing step, the first fuel recovery step, and the second fuel recovery step, the crushing tool 13b and the recovery vessel 13c and the lower platform 14b are moved by the cargo handling device 13 and the suspension device 14 into the reactor well R, the reactor pressure vessel 7 and the like. This is performed inside or in a state of being suspended in the reactor containment vessel 2. That is, the upper cover removing step, the first fuel recovery step, and the second fuel recovery step are performed in a state where the shielding port 10 is in an open state, that is, in a state where the pair of sliding doors 10b and 10b in the shielding port 10 are moved in a direction away from each other. Will be

  On the other hand, even when the shielding port 10 is in the open state, the shielding cover 11 provided on the shielding port 10 so as to face the shielding port 10 includes the crushing tool 13b, the collection container 13c, and the lower platform 14b. Only when passing, each rotating door 11c is inclined with respect to the outer peripheral base 11a in a horizontal state, and when the crushing tool 13b, the recovery container 13c, and the lower platform 14b do not pass, the inside of the reactor well R and the inside of the reactor pressure vessel 7 And, the communication with the shielding room S in the reactor containment vessel 2 is cut off.

  That is, since the shield cover 11 in the present embodiment opens and closes under conditions different from those of the shield port 10, the shield port 10 shields the reactor well R, the reactor pressure vessel 7, the reactor containment vessel 2, and the shield chamber S from each other. Complement the function. The shield port 10 ensures the shielding performance between the reactor well R, the reactor pressure vessel 7 and the containment vessel 2 and the shielded room S, and thereby the reactor well R, the reactor pressure vessel 7 and the reactor containment. Although it is possible to sufficiently reduce the dose of the radiation leaking from the container 2 to the shielding room S, the shielding performance is further improved by additionally installing the shielding cover 11 with respect to the shielding port 10. It is possible to further reduce the dose of radiation leaking from the reactor pressure vessel 7 and the containment vessel 2 to the shielding room S.

Note that the present invention is not limited to the above embodiment, and for example, the following modified examples can be considered.
(1) In the above-described embodiment, a route via the shielding plug 5 is selected as a route (arrival route) for collecting the fuel debris X, but the present invention is not limited to this. For example, an opening may be formed in the living body shielding wall 4 and an arrival path that reaches the fuel debris X from the opening may be employed.

(2) In the above embodiment, the shielding port 10 is employed as the first radioactivity shielding means, and the shielding cover 11 is employed as the second radioactivity shielding means. However, the present invention is not limited to this. The shielding port 10 and the shielding cover 11 are merely examples, and other mechanisms (structures) may be employed as long as they can be opened and closed under different conditions.

(3) In the above embodiment, the second shield plug removing step was performed after the shield cover installation step, but the present invention is not limited to this. Since the shielding cover 11 is disposed close to the third plug 5c with the shielding port 10 interposed therebetween, the turning door 11c of the shielding cover 11 interferes with the third plug 5c and the workability of removing the third plug 5c. Can be reduced. In order to solve such a concern, a shielding cover setting step may be performed after the second shielding plug removing step.

DESCRIPTION OF SYMBOLS 1 Reactor building 1a Operation floor 2 Reactor containment vessel 3 Reactor base 4 Living body shielding wall 5 Shield plug 6 Pedestal 7 Reactor pressure vessel 8 Suppression chamber 9 Ceiling crane 10 Shielding port (first radiation shielding means)
10a Main body 10b, 10b Sliding door 11 Shielding cover (second radioactive shielding means)
11a outer peripheral base 11b inner peripheral opening / closing portion 11c rotating door 11d opening 11e opening 12 shielding wall 12a shielding door 13 cargo handling device 13a trolley 13b crushing tool 13c collection container 14 suspension device 14a upper platform 14b lower platform 14c collection opening R Reactor well S Shield room X Fuel debris (radioactive fuel)

Claims (5)

Remains in the reactor pressure vessel and / or the containment vessel via an opening provided in a shielding plug provided on the operation floor of the reactor building or an access route via an opening provided by removing the shielding plug. A fuel recovery method for recovering radioactive fuel from the reactor pressure vessel or / and the containment vessel,
A first shielding means installation step of providing a first radioactive shielding means that can be opened and closed on the arrival path;
A second shielding means installation step of providing an openable and closable second radiation shielding means in the arrival path,
The first radioactivity shielding means opens and closes the arrival path in a mode of sliding in a direction intersecting the arrival path, and the second radioactivity shielding means has a rotation axis in a direction intersecting the arrival path. Opening and closing the arrival path in such a manner as to rotate . The first radiation shielding means includes a plurality of sliding doors that slide in a direction intersecting the arrival path,
2. The fuel recovery method according to claim 1, wherein the second radiation shielding means includes a plurality of turning doors that turn on a turning axis in a direction intersecting the arrival path. The fuel recovery method according to claim 1, wherein the first radiation shielding means and the second radiation shielding means are provided in the opening.   The apparatus is characterized in that the radioactive fuel is collected by suspending a device necessary for collecting the radioactive fuel from the operation floor via the first radioactive shielding means and the second radioactive shielding means. The fuel recovery method according to claim 3. 5. The fuel recovery method according to claim 3, wherein a shielding wall is constructed on the operation floor so as to surround a space around the shielding plug, and the radioactive fuel is recovered.

Images