JPH0346594A - Method for handling used core constituting element of fast reactor - Google Patents

Abstract

PURPOSE:To assure safe washing, transporting and storing without requiring special equipment by supplying the metal which has a high m.p. and is higher in sp. gr. than Na in a molten state to a separating tank housing the used core constituting elements and removing the Na, then solidifying the metal. CONSTITUTION:For example, the used fuel 2 generated in the reactor core 1 is inserted into a fuel transfer port 6 and is transferred through an out-pile relay layer 10 into the separating tank 12. The metal which has the high m.p., is larger in sp. gr. than Na, does not react with the Na and water and has an excellent thermal conductivity is melted and supplied into the tank 12 to allow the Na previously put therein to flow over the tank. After this Na is removed, the molten metal is naturally cooled and solidified to seal the internal fuel 2. The fuel 2 made into the ingot state is pulled up together with the pot 6 from the inside of the tank 12 and is transferred through a basement 14 and an air cell 13 into an underground storage house 17 where the fuel is stored. The similar method is also applicable to the used control rod and shielding bodies. The need for the equipment for handling the broken fuel is eliminated and the system for handling the fuel is simplified; in addition, radioactive waste is hardly produced.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a method for transporting spent core components such as spent fuel, spent control rods, and spent shields of a fast breeder reactor from a nuclear reactor. , relates to a handling method for cleaning and removing adhering sodium (coolant) and transporting and storing spent core components in the form of ingots during storage.

[Conventional technology]

When transporting spent core components of a fast breeder reactor, such as spent fuel, from the reactor, it is necessary to clean and remove adhering sodium (reactor coolant).

Normally, in a practical plant, when removing high-heat generating spent fuel from the reactor core, it is necessary to handle it in a pot filled with sodium, but this pot filled with sodium is submerged in water in a pool. That is Na-
This is not possible due to the need to prevent water reactions, and it is necessary to wash the spent fuel to remove the sodium attached to it.

For this reason, recently, before storing the spent fuel extracted from the reactor core in a water boule, the pot containing the spent fuel extracted from the reactor core was placed in a separation tank filled with sodium. Then, a molten metal that has a higher specific gravity than sodium and a melting point lower than the temperature of sodium in the separation tank and has low reactivity with the sodium and water in the water boule is supplied into the separation tank to remove sodium. The spent fuel is then transferred with the molten metal in the pot into a water bucket, and the bare spent fuel is removed from the pot and stored in the water bucket. There is a fast reactor spent fuel cleaning method. As a prior art document, there is Japanese Patent Application Laid-Open No. 63-21597.

[Problem to be solved by the invention] By the way, in the above-mentioned fast reactor spent fuel cleaning method, since the spent fuel is stored naked in a water bucket, separate equipment such as canning is required to handle the damaged fuel. be. Furthermore, since low melting point metals are mixed into the water in the water tank, it is necessary to remove them using a water tank purification system, and equipment for this purpose is also required. Furthermore, since a water boule is used as a storage facility, a relatively large amount of radioactive waste is generated from the boule water purification system.

Therefore, the present invention eliminates the need for equipment for handling damaged fuel, prevents metals from being mixed into the water in the water boule even when a water boule is used, and prevents the generation of radioactive waste. The aim is to propose a handling method for cleaning, transporting, and storing spent fast reactor core components such as used control rods and used shields.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the fast reactor spent core component handling method of the present invention involves removing the spent core components from the reactor while being stored in a sodium-containing fuel transfer pot. Then, a metal with a high melting point, a higher specific gravity than sodium, and which does not dissolve with sodium at high temperatures and has excellent heat transfer properties is supplied into the separation tank in a molten state, and the sodium floats to the top. The high melting point metal in the fuel transfer pot is then solidified, and the spent core components are then transported and stored in the form of an ingot.

[Effect]

As mentioned above, the method for handling spent fast reactor core components of the present invention involves placing the sodium-containing fuel transfer pot containing the spent core components into a separation tank, and then dissolving the sodium, which has a higher specific gravity than sodium and is dissolved at high temperature. A high-melting point molten metal with excellent heat transfer properties is introduced into the fuel transfer pot to float the sodium above and remove it, solidifying the molten metal and solidifying the spent core components in the fuel transfer pot. Since it is stored sealed in metal, for example, if the spent core component is damaged fuel, the damaged hole is sealed with molten metal, so it can be handled in the same way as healthy fuel, and no special equipment is required. It is. Furthermore, if the outer surface of the fuel transfer pot is stored while being cooled with air, little radioactive waste will be generated. Furthermore, by using metals that have no reactivity with water, even if a water pool is used for storage, metals will not be mixed into the water in the pool, so there is no need for equipment to remove metals in the water pool purification system. In addition, since the sodium remaining on the surface of spent fuel does not come into contact with water and no reaction occurs, radioactive corrosion products do not spread, making maintenance and maintenance easier.
Radiation exposure associated with repairs is also low.

It is also possible to handle the damaged fuel by making it into an ingot, returning it to the furnace, and storing it in a damaged fuel storage area in the furnace.

[Example] An example of the fast reactor spent core component handling method of the present invention will be described with reference to FIG. It is carried to position 5 and inserted into the previously prepared fuel transfer pot 6. The fuel transfer pot 6 is pulled up into the Ar gas cell 9 through the slope 8 by the fuel inlet/outlet machine 7.
The outer relay layer 10 is
Store it inside for a while.

Thereafter, the fuel transfer pot 6 is lifted up from the inside of the relay layer 10 outside the reactor by the fuel transfer device 11, transferred, and suspended into the separation [12]. Next, in the separation tank 12, a metal such as AI (melting point 6
60℃, specific gravity 3) or A1 alloy such as Al-3i 13% alloy (called sill main, melting point 570℃, specific gravity about 3), or Cadlam (melting point 321℃, specific gravity about 8.6) etc. are supplied in a molten state and introduced into the fuel transfer pot 6, and the previously present sodium is removed by reoverflowing through the upper overflow hole. Next, the molten metal in the fuel transfer pot 6 is solidified by natural cooling, and the spent fuel 2 therein is enclosed. The spent fuel 2 that has become an ingot in this way is pulled up from the separation tank 12 by the fuel transfer machine 11 for each fuel transfer bot 6 and transferred to the underground chamber 14 where the Ar gas cell 9 connects to the adjacent air cell 13. This fuel transfer trolley 1 is lowered onto a trolley 15.
5 is transferred to the air cell 13 side, and the air cell 13
The fuel transfer pot 6 is pulled up and transferred from the fuel transfer truck 15 into the air cell 13 by the fuel transfer device 16 inside, and is suspended and stored in the underground storage 17.

As described above, in the fast reactor spent core component handling method of the present invention, the sodium-containing fuel transfer bot 6 containing the spent fuel 2 is placed in the separated phase 12, and the fuel transfer bot 6 is filled with sodium having a specific gravity higher than that of sodium. A metal with low reactivity with sodium and a high melting point is introduced in a molten state, the sodium is removed by overflow, the molten metal is solidified, and the spent fuel 2 is stored sealed in an ingot. If the fuel 2 is damaged, the damaged hole is sealed with molten metal and solidified. Therefore, it can be handled in the same way as healthy spent fuel 2, and no special equipment is required. Furthermore, when storing the fuel in the underground storage 17, air is blown into the storage 17 by the blower 18 as shown in FIG. Almost no radioactive waste is generated. Furthermore, if a metal that does not react with water is used instead of storing it in the underground storage 17, the water boule 1 shown in FIG.
When stored in the storage rack 20 in the spent fuel 9, metals will not be mixed into the water in the water bucket 19, so there is no need for equipment to remove metals in the water bucket purification system. Residual sodium does not come into contact with water,
No reaction occurs.

In the above embodiment, the method of handling spent fuel has been described, but the handling of spent control rods and spent shielding bodies is carried out in the same manner.

[Effects of the Invention] As can be seen from the above explanation, according to the method for handling components of a spent fast reactor core of the present invention, the equipment for handling damaged fuel that was conventionally required is not required, and the fuel handling system can be simplified. It is. Additionally, since the spent core components are stored encapsulated in ingots within the fuel transfer pot, little radioactive waste is generated by storing the fuel transfer pot while it is cooled. Furthermore, if the above-mentioned fuel transfer bot is stored in a water pool, metals will not be mixed into the water in the water pool, so there is no need for metal removal equipment in the water pool purification system. Even if sodium remains attached, it is sealed in the ingot and does not directly react with the water in the water pool, so a water boule storage system can be established.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a fuel handling system that implements the fast reactor spent core component handling method of the present invention, and FIG. 2 is a diagram showing a partially modified example of FIG. 1.

Claims (1)

[Claims] 1) The spent core components are stored in a sodium-containing fuel transfer pot and removed from the reactor and placed in a separation tank.Then, in the separation tank, the spent core components are stored in a fuel transfer pot containing sodium and are dissolved at high temperatures with the sodium, which has a high melting point and a higher specific gravity than sodium. The high melting point metal in the fuel transfer pot is then solidified, after which the metal with excellent heat transfer properties is supplied in a molten state, and the sodium is floated to the top to be removed by overflow. A method for handling spent core components of a fast reactor, characterized by transporting and storing spent core components.