JPS608792A - Cooling device for fuel exchanger of pressure tube reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a pressure pipe in a nuclear reactor that is equipped with a reactor decay heat cooling system and that contains reactor fuel and is filled with cooling water. The present invention relates to a cooling device for a fuel exchanger that is attached to and detached from a fuel exchanger and exchanges reactor fuel in a pressure pipe while the main body is in communication with the cooling water.

[Prior art and its problems]

First, an overview of the fuel exchanger will be explained. FIG. 1 is a diagram showing the arrangement of a fuel exchanger and a pressure tube reactor. 1st
In the figure, a pressure tube type nuclear reactor 1 installed on a concrete floor slab constitutes a core by collecting a large number of pressure tubes 2, and each pressure tube L2 contains reactor fuel as well as cooling water as a primary coolant. is loaded. A fuel exchanger 3 is located below the core of the nuclear reactor 1. This fuel exchange MA3
5. is a traveling bogie 5. which runs on rails 4 laid along the fuel transfer route. A traversing truck 6 that moves on a running vehicle and various devices mounted on the traversing truck 6.

That is, it consists of a pressure vessel, an exchanger body equipped with a snout, etc., equipment such as a cooler and a pump, and piping. Figure 2 shows the exchanger body of the fuel exchanger.
The main body of the exchanger includes a pressure vessel 7 equipped with a snout 9 and a snout valve 10 that can be raised and lowered by a lifting device (not shown) at the top to connect to and disconnect from the pressure pipe 2, and a pressure vessel 7 that is housed inside the pressure vessel 7. It consists of various internal mechanisms arranged as described below, and the inside of the pressure vessel 7 is filled with the same cooling water as the primary coolant on the core side. The internal mechanism is a magazine 1 that individually stores new fuel, spent fuel, dry plugs, etc.
1. Grab for grabbing fuel 12° Winding mechanism for hose for grab operation 13. It is composed of a grab lifting/lowering drive mechanism 14, an internal structure 15 that supports each of these parts, and the like. The inlet nozzle 7a and the outlet nozzle 7b of the pressure vessel 7 are the inlet and outlet of cooling water, which is the same as the primary coolant for cooling the decay heat of the spent fuel, and the nozzle 7c connects the snout 9 to the pressure pipe 2.
When connected to, this is an inlet for feeding the same cooling water as the primary coolant from the water supply source into the pressure pipe 2 through the inside of the pressure vessel 7.

FIG. 3 shows a conventional cooling circuit for cooling the decay heat of the spent fuel contained in the pressure vessel 7. As shown in FIG.

In FIG. 3, spent fuel 16rr is stored in the magazine 11 shown in FIG. 2, and a cooling circuit for cooling this decay heat is connected to a cooler 17. Circulation pump 18. A closed circuit is constituted by valves 19, 19a and check valve 20@.

Still apart from this, when the snout 9 is connected to the pressure pipe 2, a circuit is shown for feeding the same cooling water from the water supply 23 through the valve 21 into the pressure vessel 7. In these circuits, the equipment on the side of the pressure vessel 7 of the flange 22 is mounted on the traversing truck 6 shown in FIG. 1, and the refueling machine can be moved through the 7-lexiple conduit 22a.

Next, the flow of cooling water, which is the same as the primary coolant, through this cooling circuit will be explained. First, snout 9 cuts from pressure pipe 2 1! If so, the snout valve 10 and the pulp 21 are closed, the valve 19.19a is opened, and the circulation pump 18 sends the cooling water through the inlet nozzle 7a and into the pressure vessel 7 through the check valve 20. The cooling water, whose temperature has risen due to decay heat from the spent fuel, is sent out through the outlet nozzle 7b at the top of the pressure vessel 7, cooled by the cooler 17, and returned to the inlet of the circulation pump 18. This cooling water circulation is repeated to cool down the decay heat. Cooler 17
Cooling water from a water supply source (not shown) is sent into the cooler 17 for heat exchange. On the other hand, when the snout 9 is connected to the pressure pipe 2, the method for cooling the spent fuel 16 in the pressure vessel 7 is the same as when the snout 9 is disconnected from the pressure pipe 2, but the valve 21 is The water supply source 23 is opened and the same cooling water as the sequential coolant is passed through the pressure vessel 7 into the pressure pipe 2.
By pumping it into the pressure vessel 7, the radioactive cladding is suspended in the cooling water of the primary coolant in the pressure pipe 2.
Falling inwards is reduced. By the way, as part of an in-service inspection of a nuclear reactor plant, maintenance personnel approach equipment such as pressure vessels, coolers, pumps, and pulp to conduct a disassembly inspection. However, while the fuel exchanger is connected to the pressure pipe 2 to perform fuel exchange, the reactor core side and the pressure vessel 7 communicate with each other through the snout 9. Even if the fall of radioactive crud adhering to shodashi, fuel, pressure pipes, etc. is reduced by the method described above, the intrusion of said crud into the pressure vessel 7 is unavoidable. The spent fuel in the pressure vessel 7 generates p-radioactive crud, causing the pressure vessel 7. Cooler 17.
H, crud is precipitated and deposited on the surfaces and gaps of the current pump 18, pulp 19, etc. Therefore, maintenance personnel check the radiation level after stopping operations, and if the level is high, perform time-consuming crud decontamination work and disassemble it.
This method had the disadvantage that inspections had to be carried out and that maintenance personnel were exposed to a large amount of radiation.

[Purpose of the invention]

In the cooling system of a fuel exchanger, it reduces the precipitation and accumulation of radioactive cladding on the surfaces of equipment and in gaps.
It is an object of the present invention to provide a cooling device for a fuel exchange machine for a pressure tube type nuclear reactor, which reduces the radiation exposure of maintenance personnel during inspection and maintenance by <mk, and facilitates inspection and maintenance.

[Summary of the invention]

In order to achieve the above object, the present invention is a fuel exchanger in which the decay heat of the spent fuel stored in the pressure vessel of the exchanger body is cooled by a reactor decay heat cooling system. The pressure vessel has a cooling water inlet pipe and a cooling water outlet pipe that communicate with the downstream and upstream sides of the I-1 pump, which serves as cooling water circulation means for the reactor decay heat cooling system, through first and second valves, respectively. is connected.

While the refueling machine is installed in the pressure chamber of the reactor for fuel exchange, the first valve is opened, the second valve is closed, and the cooling water introduced into the exchanger body from the cooling water introduction pipe is supplied to the reactor. The exchanger main body and pressure pipe are separated from each other after the fuel exchange is completed, and the second valve is opened to cool the reactor. Cooling water introduced into the exchanger body from the water inlet pipe is circulated to the reactor decay heat cooling system.

[Embodiments of the invention]

FIG. 4 shows a cooling circuit according to the present invention in which the cooler in the cooling circuit of a fuel exchanger in the prior art is deleted, and the decay heat cooling of the spent fuel in the exchanger body is performed by the reactor decay heat cooling system. Please use the one that shows. In the drawings, the same parts as in FIGS. 1 to 3 are given the same reference numerals. In Figure 4, the reactor decay heat cooling system is the circulation pump 2.
4. Cooler 25. By connecting the circuit connecting the filtration and demineralization device 26 to the reactor-subcooling system 30,! The decay heat cooling of the reactor is performed after the reactor is shut down. The decay heat cooling system for the spent fuel 16 stored in the pressure vessel 7 of the exchanger body includes a booster pump 27 and a regulating valve 28.
．． First valve 19. Check valve 20° pressure vessel 7. second valve 1
9a, circulation pump 24 via pump inlet pipe 24a
．． Cooler 25. Via the filtration desalination device 26, the pipe line 26a
The booster pump inlet pipe 27a is connected to the booster pump inlet pipe 27a. Note that the equipment on the pressure vessel side of the flange 22 is mounted on the traversing truck 6 shown in FIG. 1, as in the prior art, and the fuel exchanger can be moved through the flexible conduit 22a.

Next, the flow of cooling water in the primary cooling blade during reactor decay heat cooling in the reactor decay heat cooling system will be explained.

After the reactor was shut down, the temperature of the reactor rose due to the decay heat of the reactor.
The cooling water of the secondary cooling system 30 is sent to the cooler 25 by the circulation pump 24 via the pipe 30a and the circulation pump inlet pipe 24a, and then flows to the cooler from a water supply source (not shown). It is cooled by heat exchange with the cooling water, and then sent to the filtration desalination equipment 2.
6, the radioactive crud is captured and sent to the reactor-subcooling system 3 via pipe 26a and pipe 30b.
By repeating this cycle, the decay heat of the reactor is cooled down. On the other hand, the decay heat of the spent fuel stored in the pressure vessel 7 of the conversion base is cooled down inside the exchanger body. The flow of the primary cooling water that flows differs depending on whether the snout 9 is connected to the pressure pipe 2 or disconnected. First, Snout 9
A case will be explained in which the pressure pipe 2 is connected to the pressure pipe 2. In this case, the second valve 19a is closed, and the first valve 19 and the snout valve IO are turned on. At this time, the primary cooling water whose temperature has risen due to the decay heat of the spent fuel in the pressure vessel 7 is
9 to the pressure pipe 2. Here, since the pressure pipe 2 is an IM component of the reactor-secondary cooling system 30, the cooling water flowing into the pressure pipe 2 becomes together with the cooling water of the primary coolant for cooling the reactor decay heat, On the circuit, it is included in the reactor-subcooling system 30 in FIG. 4, and is sludged and cooled through the same route as in the decay heat cooling of the reactor described above. However, after passing through the filtration and desalination equipment 26, it is routed through a pipe 27a in a direction different from the direction to the reactor-secondary cooling system 30, which is separated at the tube bed of the pipe 26a. A part of the cooling water is sent to the booster pump 27 after being pressurized, and is sent to the regulating valve 2.
8, the flow rate is adjusted, the fuel flows into the pressure vessel 7 and returns to the snout 9, and this circulation is repeated to cool down the decay heat of the spent fuel in the pressure vessel. On the other hand, the cooling water for the primary coolant that cools down the decay heat of the reactor passes through the filtration and desalination equipment 26 and then il! , a nuclear reactor separated in the tube bed of the conduit 26a.
The decay heat of the nuclear reactor is cooled by being returned to the reactor-subcooling system 30 via the pipe line 30b heading toward the sub-cooling system 30.

Next, when the snout 9 is separated from the pressure pipe 2,
The snout valve 10 is closed, and the first valve 19 and second valve 19a are opened. At this time, the cooling water of the primary coolant whose temperature has risen due to the decay heat of the spent fuel 16 in the pressure vessel 7 is
The circulation pump 24 of the reactor decay heat cooling system is connected via the valve 19a of the reactor decay heat cooling system. The water is cooled via the cooler 25 and the filtration desalination device 26, and is then pressurized by the booster pump 28 via the pipes 26a and 27a. The cycle of return and return is repeated to cool down the decay heat of the spent fuel. On the other hand, the decay heat of the reactor is cooled by the same flow of cooling water from the primary cooling system as described above, from the reactor to the secondary cooling system 30 to the circulation pump 24. It is returned to the sub-reactor cooling system 30 via the cooler 25 and the filtration/desalination device 26.

In any case, the reactor decay heat cooling system cooler is used to cool the decay heat of the spent fuel stored in the pressure vessel 7, and the reactor decay heat cooling system cooler is used to cool the decay heat of the spent fuel stored in the pressure vessel 7. Radioactive crud in the cooling water of the next coolant is captured.

〔Effect of the invention〕

As described above, according to the present invention, the decay heat of the spent fuel stored in the pressure vessel of the exchanger body of the fuel exchanger is cooled by the cooler of the reactor decay heat cooling system. In technology, it is possible to eliminate the cooler and its attached piping in the cooling circuit of a fuel exchanger, which reduces manufacturing costs, eliminates the need for inspection and maintenance of the cooler, and reduces radiation exposure for maintenance personnel. reduce -P, since the radioactive crats in the cooling water of the reactor decay heat cooling system are captured and reduced by the filtration desalination equipment in the reactor decay heat cooling system, the decay heat of the spent fuel in the exchanger body is cooled. Therefore, there is less radioactive crud that settles and accumulates on the surfaces and crevices of equipment such as pumps and valves installed.
The radiation exposure dose for maintenance personnel during inspection and maintenance is extremely low, making inspection and maintenance easier.

[Brief explanation of the drawing]

Figure 1 is a layout diagram of a fuel exchanger in a pressure tube reactor facility, Figure 2 is a sectional view of the exchanger body, Figure 3 is a cooling circuit diagram for cooling spent fuel decay heat in a conventional fuel exchanger, FIG. 4 is a cooling circuit diagram for cooling spent fuel decay heat in a fuel exchanger implementing the present invention.0 1: Core of pressure tube reactor, 2: Pressure tube, 3: Fuel exchanger, 7: Pressure Container, 9: Snout, 10: Snout valve,
16: Spent fuel, 17: Cooler of the cooling circuit of the fuel exchange device, 19: First valve, 19a: Second valve, 25: Cooler of the reactor decay heat cooling system.

Claims (1)

[Claims] 1) The reactor fuel of a nuclear reactor equipped with a yjL sub-reactor decay heat cooling system is attached to and detached from a pressure pipe filled with cooling water, and the main body is connected to the cooling water inside the pressure pipe. In a cooling device for a fuel exchanger for exchanging reactor fuel, a cooling water inlet pipe is connected to the exchanger body to the downstream and upstream sides of the cooling water circulation means of the reactor decay heat cooling system through first and second valves, respectively. A cooling water outlet pipe is connected, and while a fuel exchanger is attached to the pressure pipe and fuel is being exchanged, the first valve is opened and the second valve is closed, and the cooling water is introduced from the cooling water inlet pipe into the exchanger main body. The cooling water introduced into the exchanger body from the cooling water introduction pipe is guided to the pressure pipe, and after the fuel exchange is completed, a second valve is opened to circulate the cooling water introduced into the exchanger body from the cooling water introduction pipe to the reactor decay heat cooling system. A cooling device for a fuel exchanger for a pressure tube nuclear reactor, characterized by the following features: