JPS6394199A - Spent fuel treating facility for nuclear reactor facility - Google Patents

Abstract

(57) [Abstract] 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 spent fuel handling equipment for nuclear reactor facilities intended for fast breeder reactors that use liquid metals such as sodium as the primary coolant.

[Prior art and its problems]

As is well known, spent fuel removed from the above-mentioned nuclear reactor is generally first cleaned of liquid metals such as sodium adhering to it, and then transported into a fuel storage pool and stored. ing. Conventionally, spent fuel cleaning equipment in this case sprays wet gas containing steam onto the spent fuel while it is housed in a cleaning tank, then washes it with water and then dries it with warm air, etc. A cleaning device using a steam-water cleaning method is generally employed. Here, conventional spent fuel handling equipment incorporating the above-mentioned steam-water cleaning system is shown in Figs. 4 and 5. In Fig. 0, 1 is a nuclear reactor, 2 is a fuel storage pool,
3 is a spent fuel cleaning device using a steam-water cleaning method installed on the fuel transfer path between the reactor 1 and the fuel storage pool 2, and the cleaning device 3 has multiple cleaning units lined up on the floor. It consists of tanks 3a and 3b, a cleaning waste liquid recovery tank 3c connected to each cleaning tank via piping, and auxiliary equipment (not shown) such as a steam, water, and inert gas supply system. Next, to explain the procedure for handling spent fuel, the spent fuel 5 taken out from the reactor 1 by fuel handling 8!4 is carried out to the relay tank 6, and from there the spent fuel cleaning equipment 2 is cleaned by the incel crane 7. It is carried into a tank and cleaned using the steam-water cleaning method described above. The cleaning waste liquid generated during cleaning is temporarily stored in the waste liquid recovery tank 3C.
From there, it is sent to the liquid waste treatment system within the nuclear reactor facility for treatment. On the other hand, the spent fuel that has been cleaned is transferred again to the traveling trolley 8 under the floor by the incel crane 7, and then transferred to another incel crane 9. Underwater traveling trolley 10. The fuel is stored in the storage rack 2a in the fuel storage pool 2 via the pool transfer device 11. However, in the spent fuel cleaning equipment using the steam-water cleaning method described above, it takes more than an hour to clean one spent fuel, so one cleaning tank is sufficient for fuel exchange work. Depending on the size of the reactor, it is usually possible to deal with this situation by equipping multiple cleaning tanks so that multiple spent fuel can be cleaned in parallel. In addition, in the steam-water cleaning described above, a large amount of radioactive cleaning waste liquid containing about 1.5 tons of radioactive crud, radioactive corrosion products, etc. is generated per spent fuel.
Troublesome problems arise in waste treatment, such as an increase in the size of equipment including the cleaning waste liquid collection tank 3c and a waste liquid treatment system, and an increase in radioactive contamination. As a result, in spent fuel handling facilities, the number of cleaning equipment used has increased.
Moreover, a large amount of space is required for its arrangement. On the other hand, as an alternative to the conventional steam-water cleaning method described above, a new dry cleaning method has been proposed for cleaning spent fuel without generating radioactive waste liquid. The principle of this dry cleaning method is to heat and raise the temperature of spent fuel while it is housed in a cleaning tank, thereby melting and evaporating the sodium adhering to the spent fuel and cleaning it. More specifically, there is a high-temperature gas blow cleaning method that removes evaporated sodium vapor and mist from the surface of the spent fuel by blowing heated inert gas toward the spent fuel in the heating process, or the above-mentioned method. After preheating the spent fuel in the heating process, the atmosphere in the cleaning tank is further reduced in pressure to below the saturated vapor pressure of sodium relative to the preheating temperature, thereby promoting evaporation of the liquid metal adhering to the spent fuel. There are vacuum cleaning methods for cleaning. According to this dry cleaning method, steam is generated during the cleaning process. Since no water is used, there is no generation of radioactive waste liquid due to cleaning, and it is possible to effectively clean spent fuel by treating only a small amount of exhaust gas. The recovery tank can be omitted, and the equipment can be made more compact by simply installing a small sodium drain tank to recover the sodium removed from the cleaning tank, and the time required to clean the spent fuel can also be reduced. Compared to the air-water cleaning method, the time can be significantly reduced.
1il approved.

[Purpose of the invention]

This invention was developed in consideration of the above points, and eliminates the difficulties of conventional spent fuel handling equipment, does not require large-scale waste liquid treatment equipment, and moreover reduces the space required for the entire equipment, making it compact and compact. The purpose is to provide spent fuel handling equipment for nuclear reactor facilities that can be installed compactly.

[Key points of the invention]

In order to achieve the above object, the present invention focuses on the fact that the dry cleaning method described above does not generate cleaning waste liquid due to cleaning, and that the cleaning time is short. A dry-cleaning type spent fuel cleaning device is installed on the spent fuel transfer route that heats the spent fuel to raise its temperature to melt and evaporate sodium, etc. attached to the spent fuel. This is designed to simplify and downsize the handling equipment.

[Embodiments of the Invention] Figures 1 and 2 are overall configuration diagrams of spent fuel handling equipment according to embodiments of the present invention, and Figure 3 is a system diagram of spent fuel cleaning equipment using a dry vacuum cleaning method. The same members as in FIGS. 4 and 5 are given the same reference numerals. That is, in FIGS. 1 and 2, according to the present invention, a dry cleaning method designated by 12 is installed as a spent fuel cleaning device on the spent fuel transfer path between the reactor 1 and the fuel storage pool 2. A spent fuel cleaning device is installed. This cleaning device 12 has a cleaning tank 14 with a door pulp 13 facing above the floor. A small-capacity drain tank 15 for collecting sodium drain discharged from the cleaning tank 14. It consists of additional equipment, etc., which will be described later. The spent fuel transfer route is almost the same as that shown in FIGS. 4 and 5, and the spent fuel 5 taken out from the reactor 1 by the fuel exchanger 4 is transferred into the cleaning tank 14 of the cleaning device 12 by the in-cell crane 7. It is carried in, and dry cleaning is performed here (details of the dry cleaning method will be described later). After the cleaning is completed here, the spent fuel 5 is transferred to the incel crane 7, the traveling truck 8. Incel crane9.
Underwater traveling trolley 10. The fuel is transferred to the storage rack 2a of the fuel storage pool 2 via the pool transfer device 11. Next, the configuration and cleaning operation of the spent fuel cleaning system using the dry cleaning method, especially the vacuum cleaning method, will be explained with reference to FIG. 3. 16. Gas heater 17.
Gas cooler18. A gas circulation line 20 equipped with a vapor trap 19 and the like and connected to the cleaning tank 1. and means for preheating the spent fuel assembly including an inert gas i1!21, such as argon gas, connected to the gas circulation line 20, and a vacuum tank 22. Vacuum pump 23. Gaseous waste treatment system 2 via vapor trap 24 etc.
A decompression means in the form of a decompression exhaust line 26 leading to 5 is additionally provided. Furthermore, a sodium drain tank 15 is connected to the cleaning tank 14 and the vacuum tank 22 by connecting piping to the bottom thereof. Next, the procedure for cleaning spent fuel with the above configuration will be explained. First, the spent fuel 5 taken out from the reactor
is accommodated in the cleaning tank 14 through the door pulp 13. At this point, the pulp in the gas circulation line 20 is opened, a predetermined amount of argon gas is introduced into the system from the inert gas source 21, and the blower 16. The gas heater 17 is started, the heated gas is circulated into the cleaning tank 14, and the entire area of the spent fuel 5, including the fuel pin that generates decay heat and non-heat generating parts other than the fuel pin, is melted with sodium. , the temperature is raised to a predetermined preheating temperature (preferably about 450 to 550°C) that is higher than the evaporation temperature. Additionally, if the temperature of the spent fuel 5, especially the surface temperature of the fuel pin that generates decay heat, reaches a permissible temperature during this preheating process, the gas cooler 18 of the gas circulation line 20 temporarily is started to lower the circulating gas temperature, and temperature 111 is performed to maintain the spent fuel 5 at a predetermined preheating temperature.Meanwhile, while this preheating process is being performed, the cleaning tank 14 is The vacuum pump 23 is started to reduce the pressure inside the vacuum tank 22 while the pulp between the two is closed. When the spent fuel 5 reaches a predetermined preheating temperature through the preheating process described above, the cleaning tank 14 and the gas circulation line 20 are once disconnected, and then the pulp leading to the vacuum tank 22 is opened and the cleaning tank 14 is opened. The pressure inside the cleaning tank 14 is rapidly reduced, and then the inside of the cleaning tank 14 is further evacuated by the vacuum pump 23, so that the internal pressure in the cleaning tank is lower than the sodium saturated vapor pressure at that temperature, for example, about 4 to 10 Torr. Exhaust. This accelerates the evaporation of the sodium adhering to the surface and inside of the spent fuel 5.
Sodium vapor and mist are cleaned and removed from the spent fuel. Note that most of the sodium fumes and mist generated during this process are in the cleaning tank 14. and vacuum tank 22
The remaining floating air and mist are adsorbed and removed by the vapor trap 24 in the vacuum exhaust line 26 along with the exhaust gas, and only the exhaust gas in an amount corresponding to the internal volume of the cleaning tank 14 is converted into gas. The waste is sent to the waste treatment system 25 and processed. In addition, the purified inert gas is returned to the inert gas source and used again to preheat the spent fuel. Please repeat the above cleaning procedure several times as necessary.
The spent fuel assembly 3 is thoroughly cleaned and the series of cleaning steps is completed. Also, along with the above-mentioned cleaning, the cleaning tank 14. The sodium deposited in the vacuum tank 22 is heated by a cleaning tank, a heater (not shown) installed in the vacuum tank, and the heat generated by the collapse of the spent fuel assembly itself to melt the sodium, and then drain the sodium. It is discharged and stored in the tank 15, from which it is sent to a sodium recovery system (not shown). In this case, the amount of sodium recovered is approximately 0.5 kg per spent fuel, and therefore the volume of the sodium drain tank 15 is much smaller than the volume of the cleaning waste liquid recovery tank in the steam-water cleaning method. Also, the time required for cleaning is approximately half that of conventional cleaning methods, so as shown in Figure 1, fuel exchange can be done by simply installing one cleaning device in the spent fuel handling facility. You will be able to proceed with your work without any problems. Note that the high-temperature gas blow cleaning method described above does not include the vacuum exhaust line 26 in the dry vacuum cleaning device shown in FIG. 3, and uses only the gas circulation line 20 to heat the spent fuel 5 and blow out the high-temperature gas. The system is designed to evaporate and remove adhering sodium from burned fuel.

【Effect of the invention】

As described above, according to the present invention, a dry cleaning type spent fuel cleaning device is installed in the middle of the spent fuel transfer route between the reactor and the fuel storage pool.
Compared to conventional spent fuel handling equipment that uses water cleaning equipment and is installed within the facility, there is no generation of waste liquid that is troublesome to process when cleaning spent fuel, and the waste liquid processing equipment is large-scale. Moreover, in practical terms, a single cleaning tank can handle fuel exchange operations without any problems. Therefore, compared to conventional equipment, the components and installation space of the spent fuel handling equipment can be reduced, and the entire equipment can be simplified and made smaller and more compact.

[Brief explanation of the drawing]

1 and 2 are a side sectional view and a plan view showing the configuration and arrangement of spent fuel handling equipment according to an embodiment of the present invention, respectively, and FIG. 3 is a spent fuel cleaning method using the dry vacuum cleaning method in FIG. 1. The system diagram of the device, FIGS. 4 and 5, are a side sectional view and a plan view showing the configuration and arrangement of conventional spent fuel handling equipment. In each figure, 1: Nuclear reactor, 2: Fuel storage pool, 4: Fuel exchange machine, 5
: Spent fuel, 7.9: Incel crane, 8,10:
Transfer trolley, 11: Pool transfer machine, 12: Dry cleaning device,
14: Cleaning tank, 15: Drain tank. Figure 2 Figure 3

Claims (1)

[Claims] 1) In spent fuel handling equipment where spent fuel is taken out from a nuclear reactor that uses liquid metal such as sodium as the primary coolant and then transported to the fuel storage pool, The nuclear power plant is characterized by being equipped with a dry cleaning type spent fuel cleaning device that melts and evaporates sodium, etc. adhering to the spent fuel by heating the spent fuel and raising its temperature in the middle of the spent fuel transfer route. Spent fuel handling equipment for reactor facilities.