Method for removing a vessel from a cavity and associated method for dismantling a reactor in a nuclear power plant
By segmenting the reactor pressure vessel using a robot system with a cutting tool, the method addresses the challenge of dismantling large vessels, achieving efficient and cost-effective removal without heavy lifting equipment.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- FRAMATOME GMBH
- Filing Date
- 2024-11-13
- Publication Date
- 2026-05-21
AI Technical Summary
The dismantling of reactor pressure vessels in nuclear power plants is difficult and expensive due to the need for heavy lifting equipment, making it challenging to remove the massive vessels from their cavities.
A method involving a robot system with a cutting tool to divide the peripheral wall of the reactor pressure vessel into segments, which are then removed using a lifting tool, reducing the vessel's weight to less than 70% of its initial weight, allowing easier handling and removal without heavy equipment.
The method facilitates the dismantling process by enabling the handling of smaller, manageable segments, reducing the need for heavy lifting equipment and lowering costs, thus making the process more efficient and economical.
Smart Images
Figure EP2024082151_21052026_PF_FP_ABST
Abstract
Description
[0001] Method for removing a vessel from a cavity and associated method for dismantling a reactor in a nuclear power plant
[0002] This invention relates to the dismantling of a reactor in nuclear power plants. In particular, this invention deals with the removing of a vessel from a cavity, and in particular of a reactor pressure vessel.
[0003] In nuclear power plants, the reactor comprises a reactor pressure vessel disposed in a cavity. The cavity is for example defined in a concrete shielding structure.
[0004] In the case of a pressurized water reactor (PWR), the reactor pressure vessel is generally suspended in the cavity, for example by means of brackets.
[0005] In the case of a boiling water reactor (BWR), the reactor pressure vessel generally sits on a support frame arranged in the cavity.
[0006] For dismantling a reactor, it is necessary to remove this pressure vessel from the cavity.
[0007] Since the reactor pressure vessel is massive, it is usual to lift the vessel out of the cavity by means of a lifting tool adapted to lift very heavy materials, such as a strand jack for example.
[0008] However, such method is difficult to implement and expensive, in particularly due to the required use of this heavy lifting equipment.
[0009] One aim of the invention is to facilitate the dismantling of the reactor vessel.
[0010] To this end, the invention proposes a method for removing a vessel from a cavity, the vessel comprising a vessel shell with a peripheral wall and a lower calotte,
[0011] the peripheral wall extending according to an elevation direction between an upper edge and a lower edge connected to the lower calotte,
[0012] the peripheral wall being divided, in the elevation direction, into m horizontal portions with m being superior or equal to 2, each horizontal portion extending in the elevation direction between an upper edge and a lower edge,
[0013] the method comprising the following steps:
[0014] a) a first step of arranging at least one robot system on the upper edge of the peripheral wall, the robot system comprising a robot and a cutting tool connected to the robot,
[0015] b) a second step of cutting a plurality of segments from the first horizontal portion of the peripheral wall by means of the cutting tool of the robot system and removing the cut segments by means of a lifting tool, c) a third step of arranging the robot system on the upper edge of the next horizontal portion of the vessel shell, and
[0016] d) a fourth step of repeating the second step and the third step for each j-th horizontal portion, j being between 2 and m.
[0017] In other embodiments, the method comprises one or several of the following features, taken individually or in any technically feasible combination:
[0018] The robot system comprises a platform supporting the robot, the platform being adapted to be fixed to the upper edge of the peripheral wall .
[0019] The platform has a Il-inverted form.
[0020] The robot system comprises an additional telescopic arm between the robot and the cutting tool.
[0021] The cutting tool of the robot system is a thermal cutting tool.
[0022] The cutting tool is chosen between an oxyfuel torch, a plasma torch or a laser cutting head.
[0023] Each horizontal portion represents between 5% and 50% of the total height of the peripheral wall.
[0024] The weight of the remaining vessel shell after the fourth step represents less than 70% of the weight of the initial vessel shell.
[0025] The vessel is suspended in the cavity by means of retaining elements protruding from the upper edge of peripheral wall.
[0026] In the second step, the cutting step is carried out until only N strip-like shell sections remain from this first horizontal portion, with N being superior or equal to 2, each of the remaining strip-like shell sections being attached to a respective one of the retaining elements, and
[0027] The fourth step is performed until the vessel shell consists only of the N strip-like shell sections and the lower calotte.
[0028] N is equal to three.
[0029] The N strip-like shell sections are equidistantly from one another.
[0030] The invention also relates to a method for dismantling a reactor in a nuclear power plant, the reactor comprising a reactor pressure vessel arranged in a cavity, the method comprising the removal of the reactor pressure vessel as described above.
[0031] In a particular embodiment, the reactor is a pressurized water reactor.
[0032] In another particular embodiment, the reactor is a boiling water reactor. The invention and its advantages will be better understood on reading the following description given solely byway of non-limiting examples and with reference to the appended drawings, in which:
[0033] - Figure 1 is a schematic representation of the vessel before and after the performing of the method according to a first embodiment of the invention;
[0034] - Figures 2 to 4 are schematic views of steps of the method for removing a vessel from a cavity according to the first embodiment of the invention; and
[0035] - Figure 5 is a process flow diagram of the method of removing a vessel from a cavity according to the invention.
[0036] A vessel 10, in particular destined to be removed according to the method of the invention, is partly shown in the left part of Figure 1.
[0037] In a particular embodiment, the vessel 10 is a pressure vessel of a reactor.
[0038] In a first embodiment of the invention illustrated on the Figures 1 to 4, the vessel 10 is for example a pressure vessel of a pressurized water reactor (PWR).
[0039] As shown on Figure 1 , the vessel 10 comprises a vessel shell 12 with a peripheral wall 14 and a lower calotte 16.
[0040] More precisely, the vessel shell 12 is hollow.
[0041] Preferably, the vessel shell 12 is open at the top, i.e. opposed to the lower calotte 16 according to an elevation direction Z, by an opening 17. The vessel shell 12 is closed at the bottom by said lower calotte 16.
[0042] In particular, the vessel shell 12 is adapted to contain the fuel assembly coolant and neutron moderator water.
[0043] Preferably, the vessel shell 12 is made of a material adapted to be used in a nuclear power plant, for example in a particular steel alloy.
[0044] As shown on Figure 1 , the peripheral wall 14 extends according to the elevation direction Z between an upper edge 18 and a lower edge 20 connected to the lower calotte 16.
[0045] More precisely, the upper edge 18 defines the outlines of the opening 17 at the top of the vessel shell 12.
[0046] For example, the peripheral wall 14 has a height, measured between the upper edge 18 and the lower edge 20 according to the elevation direction Z, up to 20m.
[0047] For example, the peripheral wall 14 has a thickness up to 600 mm.
[0048] In a particular embodiment, the peripheral wall 14 of the vessel shell 12 has a cylindrical shape, for example with an inner diameter up to 7 m. As visible on Figure 1 , the peripheral wall 14 of the vessel shell 12 is divided, according to the elevation direction Z, into m horizontal portions 22A-D with m being superior or equal to 2; m being preferably comprised between three and twenty.
[0049] In the example shown on Figure 1 , m is equal to four.
[0050] In particular, all the horizontal portions 22A-D together define the peripheral wall 14 on its entirety.
[0051] More precisely, the horizontal portions 22A-D extend in the continuity of each other and in particular, are arranged successively to each other according to the elevation direction Z.
[0052] More precisely, each horizontal portion 22A-D represents between 5% and 50% of the total height of the peripheral wall 14.
[0053] In particular, the m horizontal portions include a first horizontal portion 22A and (m-1) j-th horizontal portion 22B-D, j being comprised between 2 and m.
[0054] By first horizontal portion 22A, it is meant here the horizontal portion 22A defining the top part of the peripheral wall 14.
[0055] In the example shown on Figure 1 , the four horizontal portions include a first horizontal portion 22A and three j-th horizontal portion 22B-D, with j being comprised between 2 and 4, i.e. a second horizontal portion 22B, a third horizontal portion 22C and a fourth horizontal portion 22D.
[0056] Each horizontal portion 22A-D extends in the elevation direction Z between an upper edge 24A-D and a lower edge 26A-D.
[0057] In particular, the upper edge 24A of the first horizontal portion 22A is the upper edge 18 of the peripheral wall 14.
[0058] In particular, for i comprised between 1 and (m-1), the lower edge 26A-C of the i-th horizontal portion 22 A-C is the upper edge of the (i+ 1 )-th horizontal portion 22 B-D.
[0059] More particularly, in the example shown on Figure 1 , the lower edge 26A of the first horizontal portion 22A is the upper edge 24B of the second horizontal portion 22B. The lower edge 26B of the second horizontal portion 22B is the upper edge 24C of the third horizontal portion 22C. The lower edge 26C of the third horizontal portion 22C is the upper edge 24D of the fourth horizontal portion 22D.
[0060] In particular, the lower edge 26D of the m-th horizontal portion 22D is the lower edge 20 of the peripheral wall 14, and in particular is connected to the lower calotte 16.
[0061] In particular, in the example shown on Figure 1 , the lower edge 26D of the fourth horizontal portion 22D is connected to the lower calotte 16.
[0062] The lower calotte 16 closes advantageously the bottom of the vessel shell 12.
[0063] As visible on Figure 1 , the lower calotte 16 has for example a hemispherical shape. In the first embodiment shown on the Figures 1 to 4, the vessel shell 12 further comprises a plurality of retaining elements 28 protruding from the upper edge 18 of peripheral wall 14.
[0064] Preferably, the vessel shell 12 comprises at least three retaining elements 28, and for example more than five.
[0065] In particular, the retaining elements 28 protrude outwards from the upper edge 18 of peripheral wall 14.
[0066] The retaining elements 28 are for example flat brackets or supports protruding outwards from the upper edge 18 of peripheral wall 14.
[0067] In an advantageous example, the retaining elements 28 are uniformly distributed around the upper edge 18 of peripheral wall 14.
[0068] As shown on Figure 2, in the first embodiment shown on the Figures 1 to 4 in which the vessel 10 is for example the pressure vessel of a pressurized water reactor, the vessel 10 during use is suspended in a cavity 30, more particularly in a nuclear power plant.
[0069] For example, the cavity 30 is defined in a structure 32, for example made of concrete. In particular, the structure 32 comprises a top face 34 with an opening from which the cavity 30 extends.
[0070] More precisely, the vessel 10 is suspended in the cavity 30 by means of the retaining elements 28.
[0071] For example, each of the retaining elements 28 rests on a top face 34 of the structure 32 in which the cavity 30 is defined.
[0072] A robot system 36 adapted to be used in the method according to invention will now be described.
[0073] As for example shown on Figure 2, the robot system 36 comprises a robot 37, a cutting tool 38 connected to the robot 37 and also preferably a platform 40 supporting the robot 37.
[0074] The robot 37 is preferably adapted to control the cutting tool 38.
[0075] In particular, the robot 37 is connected, for example wirelessly, to a control system. For example, the robot 37 comprises a camera system and / or sensors, preferably communicating with the control system.
[0076] In a preferred embodiment, the robot 37 stands on the platform 40 and in particular, is firmly attached to it.
[0077] The cutting tool 38 is preferably a thermal cutting tool, in particular adapted to cut the peripheral wall 14 of the vessel 10. The cutting tool 38 is for example chosen between an oxyfuel torch, a plasma torch or a laser cutting head.
[0078] The platform 40 is advantageously adapted to be fixed to the upper edge 18 of the peripheral wall 14.
[0079] For this purpose, the platform 40 has for example a Il-inverted cross-section, such that it could be hooked onto the upper edge 18 of the peripheral wall 14.
[0080] Preferably, the platform 40 also comprises at least one clamping cylinder, more preferably one for each side, to clamp the Il-inverted platform 40 onto the upper edge 18 of the peripheral wall 14.
[0081] The clamping cylinder(s) are for example hydraulic cylinder(s).
[0082] Optionally, the robot system 36 also comprises an additional telescopic arm 48between the robot 37 and the cutting tool 38, in particular to connect the cutting tool 38 on the robot 37 in a movable way.
[0083] An exemplar method 100 for removing the vessel 10 from the cavity 30 according to the invention will now be described in reference to Figure 5.
[0084] In a first step 101 , at least one robot system 36 as described above is arranged on the free upper edge 18 of the peripheral wall 14 of the vessel shell 12.
[0085] In a particular embodiment, only one robot system 36 is arranged.
[0086] In an alternative embodiment, a plurality of robot systems 36, and for example three robot systems 36, are arranged on the upper edge 18 of the peripheral wall 14 of the vessel shell 12.
[0087] For example, the robot system 36 is gripped, lifted and arranged by an existing lifting system (not shown), such as a crane, in particular comprising a suitable gripping system.
[0088] More particularly, the or each robot system 36 is fixed on said upper edge 18 of the peripheral wall 14 of the vessel shell 12.
[0089] For example, the platform 40 of the or each robot system 36 is clamped onto said upper edge 18.
[0090] In a second step 102 shown on Figure 2, a plurality of segments 44 are cut from the first horizontal portion 22A of the peripheral wall 14 by means of the cutting tool 38 of the or each robot system 36.
[0091] In particular, each segment 44 extends on the entire height of the first horizontal portion 22A.
[0092] In other words, each segment 44 is cut between the upper edge 24A and the lower edge 26A of the first horizontal portion 22A. The cut segments 44 have for example a slightly convex rectangular plate shape, as visible on Figure 1.
[0093] In the Figures, the cutting lines are represented as dotted lines.
[0094] In particular, each segment 44 has four cutting lines: two horizontal ones, notably extending along the upper edge 24A and the lower edge 26A of the first horizontal portion 22A, and two vertical ones, in particular extending parallel to the elevation direction Z.
[0095] In an advantageous manner, each of the cut segments 44 is small enough to be fitted into a container, for example in a standardized Konrad Container.
[0096] In particular, each of the cut segments 44 has for example a height smaller than 1.2 m and a width smaller than 2.5 m.
[0097] Advantageously, each of the cut segments 44 has a weight inferior to 4000 kg.
[0098] In the first embodiment shown on the Figures 1 to 4, the cutting step is carried out until only N strip-like shell sections 46 remain from this first horizontal portion 22A, with N being superior or equal to two.
[0099] In other words, the first horizontal portion 22A is for example cut entirely into the segments 44 by means of the cutting tool 38, with the exception of the N strip-like shell sections 46.
[0100] To put it another way, in the first embodiment, after this second step 102, the first horizontal portion 22A consists only of the N strip-like shell sections 46, as visible notably on Figure 3.
[0101] In an advantageous manner, N is equal to three, as shown on the Figures.
[0102] Preferably, the N strip-like shell sections 46 are equidistant from one another.
[0103] For example, as shown on the Figures, the three strip-like shell sections 46 are evenly distributed around the peripheral wall 14.
[0104] Preferably, each of the remaining strip-like shell sections 46 is attached to a respective one of the retaining elements 28.
[0105] Thus, in the first embodiment, the vessel 10 remains suspended in the cavity 30 by means of these retaining elements 28, as visible notably on Figure 3.
[0106] During the cutting step, the robot 37 of the or each robot system 36 carries the cutting tool 38 directly or using its telescopic arm 42.
[0107] In particular, the robot 37 controls the cutting tool 38 such that it performs the cutting inside its working range, i.e. left and right from the platform 40.
[0108] Once the robot 37 has reached its maximum working range, the robot system 36 is preferably repositioned, i.e. moved and fixed to another part of the upper edge 18 of the peripheral wall 14. In particular, the robot system 36 is gripped, lifted and arranged to another part of the upper edge 18 by the same lifting system used to arrange the robot system 36 in the first step 101.
[0109] In the second step 102, the cut segments 44 are removed by a lifting tool (not shown on the Figures).
[0110] This lifting tool is preferably a different lifting system that the one used to arrange the robot system 36.
[0111] This lifting tool is for example a crane with a gripper, preferably a two-jaw gripper. Preferably, before a segment 44 is completely cut off by the cutting tool 38 of the robot system 36, the gripper of the lifting tool grips the segment 44 and secures it from falling.
[0112] For example, the cut segment 44 is then transported away.
[0113] Preferably, the cut segments 44 are thereafter packed in a container, such as a Konrad Container for example, to be then discarded.
[0114] In a third step 103, the or each robot system 36 is arranged on the upper edge of the next horizontal portion of the vessel shell 12, for example on the upper edge 24B of the second horizontal portion 22B as shown in Figure 3.
[0115] In particular, the robot system 36 is gripped, lifted and arranged to the upper edge of the next horizontal portion of the vessel shell 12 by the same lifting system used to arrange the robot system 36 in the first step 101.
[0116] More particularly, the or each robot system 36 is fixed on upper edge 24B, and is for example clamped.
[0117] The method comprises a fourth step 104 of repeating the second step 102 and the third step 103 for each j-th horizontal portion, j being between 2 and m.
[0118] In the first embodiment shown on the Figures 1 to 4the fourth step 104 is preferably performed until the vessel shell 12 consists only of the N strip-like shell sections 46 and the lower calotte 16, as visible on the right part of Figure 1 .
[0119] In particular, in the repetition of the second step 102 for the other horizontal portions 22B-C, the uncut strip-like shell sections 46 extend according to the elevation direction Z in continuity with the uncut strip-like shell sections 46 for the first horizontal portion 22A.
[0120] In other words, in the first embodiment, at the end of step 104, each of strip-like shell section 46 extends on the entire height of the peripheral wall 14 of the vessel shell 12.
[0121] Preferably, the weight of the remaining vessel shell 12’, i.e. the N strip-like shell sections 46 and the lower calotte 16 in the first embodiment, represents often less than 70% of the weight of the initial vessel shell 12.
[0122] In a particular embodiment, the method further comprises a step 106, in which the remaining vessel shell 12’ is lifted by the lifting system to be removed it from the cavity 30. Preferably, the remaining vessel shell 12’ are cut in segments and these are thereafter packed in containers, such as Konrad Containers for example, to be then discarded.
[0123] A method for dismantling a reactor in a nuclear power plant will now be described. The reactor is for example a pressurized water reactor (PWR).
[0124] As described above, the reactor comprises a reactor pressure vessel 10 arranged in a cavity 30.
[0125] The method for dismantling the reactor comprises the removal of the reactor pressure vessel 10 according to the method previously described.
[0126] This method facilitates the dismantling of a reactor pressure vessel 10 in a nuclear power plant.
[0127] Indeed, the cutting of the vessel shell 12 into of plurality of segments 44 allows dealing with smaller pieces, which are easy to remove while the vessel 12 remains in position.
[0128] These segments 44 are easy to lift and do not require the use of a heavy lifting equipment.
[0129] The remaining vessel shell 12 after the cutting steps, i.e. the lower calotte 16 and the strip-like sections 46, is also easy-to lift to be removed from the cavity 30 without the need of a heavy lifting equipment.
[0130] Such a method is thus economically advantageous.
[0131] Furthermore, such a method is also easy to implement, in particular due to the use of at least one robot system 36.
[0132] A second embodiment of the invention (not illustrated) will now be described.
[0133] This second embodiment differs from the first one, in that the vessel 10 is not suspended in the cavity 30 by retaining elements 28, but is standing on a support frame in the cavity 30.
[0134] In this second embodiment, the vessel 10 is for example a pressure vessel of a boiling water reactor (BWR).
[0135] In particular, the reactor to be dismantled is a boiling water reactor (BWR).
[0136] In this second embodiment, the method 100 differs from the one of the first embodiment in that strip-like shell sections 46 are not necessary defined in the second step 102 of the method 100. Indeed, in the second embodiment, since the vessel 10 rests on the support frame, the vessel 10 remains in position in the cavity 30 without retaining elements More particularly, in the second embodiment, the cutting step is for example carried out until all the first horizontal portion 22A is cut into segments 44.
[0137] Furthermore, in the second embodiment, the remaining vessel shell 12’ after the fourth step 104 consists preferably only of the lower calotte 16.
Claims
CLAIMS1 . Method (100) for removing a vessel (10) from a cavity (30),the vessel (10) comprising a vessel shell (12) with a peripheral wall (14) and a lower calotte (16),the peripheral wall (14) extending according to an elevation direction (Z) between an upper edge (18) and a lower edge (20) connected to the lower calotte (16), the peripheral wall (14) being divided, in the elevation direction (Z), into m horizontal portions (22A-D) with m being superior or equal to 2, each horizontal portion (22A-D) extending in the elevation direction (Z) between an upper edge (24A-D) and a lower edge (26A-D),the method comprising the following steps:a) a first step (100) of arranging at least one robot system (36) on the upper edge (18) of the peripheral wall (14), the robot system (36) comprising a robot (37) and a cutting tool (38) connected to the robot (37),b) a second step (102) of cutting a plurality of segments (44) from the first horizontal portion (22A) of the peripheral wall (14) by means of the cutting tool (38) of the robot system (36) and removing the cut segments (44) by means of a lifting tool, c) a third step (103) of arranging the robot system (36) on the upper edge (24B-D) of the next horizontal portion (22B-D) of the vessel shell (14),d) a fourth step (104) of repeating the second step (102) and the third step (103) for each j-th horizontal portion (22B-D), j being between 2 and m.
2. Method (100) according to claim 1 , wherein the robot system (36) comprises a platform (40) supporting the robot (37), the platform (40) being adapted to be fixed to the upper edge (18) of the peripheral wall (14).
3. Method (100) according to claim 2, wherein the platform (40) has a Il-inverted form.
4. Method (100) according to claim 2 or 3, wherein the robot system (36) comprises an additional telescopic arm (48) between the robot (37) and the cutting tool (38).
5. Method (100) according to any one of claims 1 to 4, wherein the cutting tool (38) of the robot system (36) is a thermal cutting tool.
6. Method (100) according to claim 5, wherein the cutting tool (38) is chosen between an oxyfuel torch, a plasma torch or a laser cutting head.
7. Method (100) according to any one of claims 1 to 6, wherein each horizontal portion (22A-D) represents between 5% and 50% of the total height of the peripheral wall (14).
8. Method (100) according to any one of claims 1 to 7, wherein the weight of the remaining vessel shell (12’) after the fourth step (104) represents less than 70% of the weight of the initial vessel shell (12).
9. Method (100) according to any one of claims 1 to 8, wherein the vessel (10) is suspended in the cavity (30) by means of retaining elements (28) protruding from the upper edge (18) of peripheral wall (14).
10. Method (100) according to claim 9, wherein:in the second step (102), the cutting step is carried out until only N striplike shell sections (46) remain from this first horizontal portion (22A), with N being superior or equal to 2, each of the remaining strip-like shell sections (46) being attached to a respective one of the retaining elements (28), andthe fourth step (104) is performed until the vessel shell (12) consists only of the N strip-like shell sections (46) and the lower calotte (16).
11. Method (100) according to claim 10, wherein N is equal to three.
12. Method (100) according to claim 10 or 11 , wherein the N strip-like shell sections (46) are equidistantly from one another.
13. Method for dismantling a reactor in a nuclear power plant, the reactor comprising a reactor pressure vessel (10) arranged in a cavity (30), the method comprising the removal of the reactor pressure vessel (10) according to the method (100) according to any one of claims 1 to 12.
14. Method according to claim 13, wherein the reactor is a pressurized water reactor.
15. Method according to claim 13, wherein the reactor is a boiling water reactor.