Fuel debris water jet recovery system

Abstract

To recover fuel debris dissolved in concrete in water.SOLUTION: A system discharges a large amount of water from a branch pipe of an injection line 1 in front of a fuel cone to outside of the cone to flow the water on an upper surface of the cone to prevent powder of fuel debris 7 pulverized in a cone 4 from coming out of the cone, and the water flows in from the outside of the cone through a gap and does not leak to the outside. The cone is simultaneously pressed against an adhesive surface, and a bypass line 6 is provided to prevent the cone from separating from the adhesive surface. With respect to a characteristic that has a problem with fuel debris also being easily critical, boron nitride has the effect of absorbing neutrons and suppressing criticality. Boron nitride crystal is used as a blast material for the water jet. An access method includes discharging compressed air from propulsion nozzles with valves arranged vertically and horizontally in four directions inside and outside the cone attached to a tip of a flexible hose, and moving the cone to a fuel debris installation location while confirming using a television camera inside the cone.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention is applied to a device for recovering fuel debris trapped within the Fukushima Daiichi Nuclear Power Plant.

[0002] This is applied to equipment for removing concrete from underwater. [Background technology] A robotic arm is being developed to remove fuel debris from the Fukushima Daiichi Nuclear Power Plant, but obstacles have been found along the access route, making things difficult. [Prior art documents]

[0003] None

[0004] [Patent documents] [Patent documents] Patent application 2021-121025 Fuel debris collection method Summary of the Invention

[0005] The main equipment of the fuel debris water jet collection device is a circulation line that connects the injection line and the collection line. The main role of the injection line is to inject high-pressure water at the fuel debris to break it up, while the recovery line collects the water containing the broken-up fuel debris into the fuel debris storage container. A recovery building will be set up outside the reactor building. A circulation line will be set up between this recovery building and the site where the fuel debris will be collected. A recovery pump, fuel debris storage container, filter tank, injection pump, and boron nitride tank will be placed on the circulation line of the recovery building. The injection line involves an injection pump drawing in filtered water from the filter tank in the recovery building, and then using a water jet to inject high-pressure water from a jet pipe inside a cone installed at the fuel debris collection site inside the containment vessel, through piping laid inside the reactor building, to break up the fuel debris that has accumulated in the concrete and bedrock. The recovery line uses a recovery pump installed in the recovery building to draw water containing crushed fuel debris from the top of a cone installed at the fuel debris collection site through piping laid inside the reactor building, and sends it to a fuel debris storage container inside the recovery building. The diameter of the fuel debris storage container is more than 100 times that of the suction pipe, and the water flow rate is 1 / 10,000 or less. Here, the flow rate approaches zero, so most of the fuel debris powder is deposited and collected. The circulating water is then filtered by the filter in the filter tank and returned to the injection pump. This is the general flow of the system. The following two lines will be added as additional lines: A large amount of water is sprayed onto the outside of the cone from a branch pipe of the spray line just before the cone, causing the water to flow over the top of the cone, and the water flows in through the gaps from the outside of the cone, preventing it from leaking out. At the same time, a bypass line is provided to press the cone against the adhesive surface, preventing the cone from separating from the adhesive surface. Fuel debris is extremely hard, but at the same time it contains plutonium, which means that even a single atomic nucleus can easily undergo nuclear fission, and it can also easily go critical, but boron nitride crystals solve these problems at the same time. Depending on the manufacturing method, boron nitride can be harder than diamond, and at the same time, boron has the effect of absorbing neutrons and suppressing criticality. Boron nitride crystals are used as the blasting material for this water jet. An addition line that adds boron nitride crystals from a boron nitride tank is connected above the jet tube. At this time, since the injection line and the recovery line are in the same circulation line, the amount of water in each of the injection line and the recovery line is the same, and the total amount of water released from the jet pipe and the amount of water in the bypass line is also equal. The access method is to release compressed air from valved propulsion nozzles arranged vertically, horizontally, and outside a cone attached to the end of a flexible hose, and the cone is moved to the fuel debris placement location while being monitored by a television camera inside the cone. [Problem to be solved by the invention]

[0006] Move the fuel debris collection device to any location

[0007] Prevent fuel debris from going critical.

[0008] Breaking up hard fuel debris [Means for solving the problem]

[0009] In order to prevent the powder of the crushed fuel debris inside the cone from escaping from the cone, a large amount of water is discharged from a branch pipe of the injection line just before the fuel cone onto the outside of the cone, causing water to flow over the top of the cone, and water flows in from the outside of the cone through the gaps, preventing the water inside the cone from leaking out. At the same time, a bypass line is provided to press the cone against the adhesive surface, preventing the cone from separating from the adhesive surface. Fuel debris is extremely hard, but at the same time, it contains plutonium, which means that even a single atomic nucleus can easily undergo nuclear fission, and it can also easily go critical. Boron nitride crystals solve these problems at the same time. Depending on the manufacturing method, boron nitride can be harder than diamond, and at the same time, boron has the effect of absorbing neutrons and suppressing criticality. Boron nitride crystals are used as the blasting material for this water jet. The fuel debris collection device is first temporarily placed in the penetration sleeve that penetrates the reactor containment vessel, and compressed air is released from the four vertical and horizontal propulsion jet nozzles 25 to pull the propulsion flexible hose and guide it to the desired location while checking with the camera with a shielding door inside the cone. The door of the camera with a shielding door inside the cone is closed during cutting. Effect of the Invention

[0010] The powder of the crushed fuel debris inside the cone must be collected without escaping from the cone.

[0011] The fuel debris contains plutonium that undergoes spontaneous fission, preventing a chain reaction that would lead to criticality.

[0012] Breaking up hard fuel debris.

[0013] Move the fuel debris collection device to any location [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 shows the fuel debris collection device. The injection line 1 injects water 8 from a jet tube 5 inside the cone 4 onto the fuel debris 7, pulverizing the fuel debris 7, while the collection line 2 above the cone 4 collects the water containing the floating fuel debris powder. The branch pipe of the injection line 1 connects to the injection bypass line 6, and the water flows into the cone 4 from outside the cone as gap water between the bottom of the cone and the adhesive surface. This injection bypass line 6 prevents the fuel debris powder from leaking outside the cone 4, and allows the cone 4 to adhere to the adhesive surface. The flow rate of the injection bypass line 6 is adjusted by the injection bypass line valve 10. The fuel debris collection device has propulsion jet nozzles 25 arranged vertically and horizontally inside and outside the cone in order to move underwater or through air. It is propelled using compressed air while being checked by a camera 28 with a shielding door inside the cone. [Diagram 2]Figure 2 shows an overall view of the fuel debris water jet collection system. Fuel debris 7 falls from the reactor pressure vessel 11 in the reactor building 13 to the bottom of the containment vessel 12. The fuel debris collection device 24 is connected to the injection line 1, collection line 2, and addition line 3, and the tip 10m is wrapped around the periphery of the flexible hose 27. The main role of the injection line 1 is to inject high-pressure water at the fuel debris 7 to crush it. The collection line 2 collects the water containing the crushed fuel debris into the fuel debris storage vessel 14. A collection building 22 is installed outside the reactor building 13. Inside the collection building 22, a collection pump 18, fuel debris storage vessel 14, filter tank 15, boron nitride tank 16, and injection pump 17 are installed. Between the collection building 22 and the containment vessel 12, the injection line 1, collection line 2, and addition line 3 are provided with shielding water 19 as shown in the transport cross section 23 in order to shield the radial edge. In the injection line 1, the injection pump 17 sucks in filtered water from the filter tank 15 in the recovery building 22, and through piping laid in the reactor building 13, high-pressure water is injected using a water jet from the jet pipe 5 in the cone 4 installed at the fuel debris collection site in the containment vessel, and the fuel debris 7 accumulated in the concrete or bedrock is crushed. The recovery line 2 sucks in water containing crushed fuel debris from the upper part of the cone 4 installed at the fuel debris 7 collection site through piping laid in the reactor building 13 by the recovery pump 18 installed in the recovery building 22, and sends it to the fuel debris storage container 14 in the recovery building 22. The diameter of the fuel debris storage container 14 is more than 100 times the diameter of the piping of the recovery line, and the flow rate of the water is 1 / 10,000 or less. Here, the flow rate approaches zero, so most of the fuel debris powder is accumulated and collected. The collected water is further filtered by the filter in the filter tank 15 and sucked into the injection pump 17. This is the general flow of the system. The following two lines are added as auxiliary lines: A large amount of water is discharged from the branch pipe of the injection line 1 just before the cone 4 to the outside of the cone, causing the top surface of the cone 4 to flow, and the gap water 9 flows in through the gap from the outside of the cone 4, so that the water inside the cone does not leak out. At the same time, an injection bypass line 6 is provided to press the cone 4 against the adhesive surface, preventing the cone 4 from separating from the adhesive surface.Fuel debris 7 is very hard, but at the same time it contains plutonium, making it susceptible to nuclear fission even with a single atomic nucleus, and also prone to criticality, both of which are problems that can be solved by boron nitride crystals. Depending on the manufacturing method, boron nitride can be harder than diamond, and at the same time, boron has the effect of absorbing neutrons and suppressing criticality. Boron nitride crystals are used as the blasting material for this water jet. An addition line 3 that adds boron nitride crystals from a boron nitride tank 16 is connected above the jet tube 5. At this time, since the injection line 1 and the recovery line 2 are both in the same circulation line, the amount of water in each of the injection line 1 and the recovery line 2 is the same, and the total amount of water released from the jet tube 5 and the amount of water in the injection bypass line 6 is also the same. The fuel debris collection device 24 is first temporarily placed in the penetration sleeve 26 that penetrates the reactor containment vessel 12, and compressed air is released from the four vertical and horizontal propulsion jet nozzles 25 to pull the propulsion flexible hose 27, and it is guided to the desired location while being checked by the camera 28 with a shielding door inside the cone. During cutting, the door of the camera 28 with a shielding door inside the cone is closed. [Industrial Applicability]

[0015] Pile Drilling Rig [Explanation of symbols]

[0016] 1. Injection line 18. Recovery pump 2. Recovery line 19. Shielding water 3.Addition line 20.Removal of fuel debris storage container 4. Cone 21. Trailer 5. Jet Tube 22. Recovery Building 6. Injection bypass line 23. Transport section 7. Fuel debris 24. Fuel debris collection equipment 8. Water jet 25. Propulsion jet nozzle 9. Gap water 26. Through sleeve 10. Injection bypass line valve 27. Flexible hose 11. Reactor pressure vessel 28. Camera with shielded door inside the cone 12. Nuclear Reactor Containment Vessel 13. Reactor building 14. Fuel Debris Storage Container 15. Filter tank 16. Boron nitride tank 17. Injection pump

Claims

1. This system is composed of a jet pump sucking in filtered water from the filter tank in the recovery building, and sending it through a jet line of piping installed inside the reactor building to a downward jet pipe inside a bottomless cone installed at the fuel debris accumulation site, where high-pressure water is sprayed onto the fuel debris submerged in the water at the bottom of the cone using a water jet, crushing the fuel debris, and a recovery pump installed in the recovery building sucking in water containing floating fuel debris inside the cone through piping installed inside the reactor building, sending it to the fuel debris storage tank in the recovery building, and a recovery line where the fuel debris settles. In addition to the main equipment, which connects the jet line and the recovery line by sending water from the fuel debris storage tank to the filter tank to form a circulation line, a recovery lane is also installed as an auxiliary equipment. The system also has an additive line that connects boron nitride crystals, air, and water from a boron nitride tank installed in the recovery building to a jet tube in the cone, which releases high-pressure water from a branch of the injection line installed above the cone to prevent water from escaping the cone through the gap between the bottom of the cone, which is the starting point of the inflow, and the adhesive surface, and flows over the top of the cone and into the gap at the bottom of the cone from outside, while at the same time pushing the cone against the adhesive surface, preventing the cone from separating from the adhesive surface.The system also has an additive line that connects boron nitride crystals, air, and water from a boron nitride tank installed in the recovery building to a jet tube in the cone, which connects high-pressure water from a branch of the injection line installed above the cone to a jet tube in the cone, which flows over the top of the cone and flows in from outside the gap at the bottom of the cone, and presses the cone against the adhesive surface, preventing the cone from separating from the adhesive surface.The boron nitride crystals are said to be harder than diamonds, and cut the fuel debris, which is extremely hard and contains plutonium, making it easy for even a single atomic nucleus to undergo nuclear fission and also prone to criticality, and the boron absorbs neutrons to suppress criticality.

2. The cone is attached to the end of a flexible hose and is equipped with propulsion equipment that releases compressed air from valved propulsion nozzles arranged vertically, horizontally, and outside the cone, and moves the cone to the fuel debris placement location while being monitored by a television camera inside the cone.

3. A ring-shaped rubber tube is attached to the outside of the penetration hole in the reactor containment vessel, and a flexible hose with a cone attached to the tip is inserted into the ring. Pressurizing the rubber tube increases the airtightness of the reactor containment vessel, and when the cone gains a certain amount of propulsive force from the compressed air jet, the rubber tube is depressurized, causing the cone to move into the reactor containment vessel.

Images