JPS6154846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an apparatus for refining liquid metal such as liquid sodium used in the secondary cooling system of a fast breeder reactor, and in particular, to ensure air pollution during regeneration of a cold trap. The present invention relates to a liquid metal refining device that can prevent the above.

In the secondary cooling system of a fast breeder reactor plant,
Liquid metal such as liquid sodium is used as a coolant, but hydrogen gets mixed in and diffuses into this liquid metal due to corrosion on the water side of the heat transfer tube while it circulates through the steam generator, so hydrogen is removed using a purification device. Needs to be removed.

A cold trap type is often used as this purification equipment, but the amount of hydrogen diffusion mentioned above is quite large, and cold traps usually become clogged after 2 to 3 years, so regeneration treatment must be performed every time. become. This regeneration of the cold trap takes advantage of the fact that the chemical reaction between hydrogen and sodium is reversible. In other words, the blocked cold trap is
When heated to over 300°C, the partial pressure of hydrogen increases and becomes higher than the vapor pressure of sodium, so the high temperature sodium from the cold trap is introduced into the gas vent and the gas space is filled with hydrogen. If the pressure is reduced to below the partial pressure, the hydrogen in the sodium will be transferred to the gas.

Conventionally, when a cold trap is regenerated in this manner, the generated hydrogen is released into the atmosphere simply by removing sodium paper or sodium mist through one or two stages of paper traps.

By the way, in the secondary cooling system of a fast breeder reactor, it is expected that some of the sodium (tritium) generated in the reactor core will diffuse into the tube walls of the intermediate heat exchanger heat exchanger tubes and enter. This sodium is an isotope of hydrogen, and its behavior and chemical properties are almost the same as that of hydrogen, so it can be used both in the hydrogen captured in the cold trap and in the hydrogen released during its regeneration. It is thought that it contains tritium, albeit in a small amount. Since tritium is radioactive, it is necessary to prevent its release into the atmosphere, even in minute amounts, as much as possible.

The present invention has been developed in view of the above-mentioned circumstances, and when regenerating a cold trap, the generated gas is adsorbed on an adsorption column of a constant temperature bath for cooling, and then the adsorbed contents are transferred to a cylinder. It is an object of the present invention to provide a liquid metal refining apparatus configured to be housed.

The details of the present invention will be explained below with reference to embodiments shown in the drawings.

In FIG. 1, a cold trap 10 has a built-in trap mesh 11, and a cooling fan 12 and a heater 13 are provided on the outside. An inlet valve 15 and an electromagnetic pump 16 are inserted into the inlet pipe 14 of the cold trap 10, and an outlet pipe 17
An outlet valve 18 is inserted therein. Inlet piping 14
The recirculation lines 19 and 20 branched from between the inlet valve 15 and the electromagnetic pump 16 and between the cold trap 10 and the outlet valve 18 of the outlet pipe 17 are connected to the degassing port 23 via line valves 21 and 22, respectively.
It is open inward. A gas venting pipe 2 is placed above the liquid level 24 of sodium stored in the gas venting pot 23.
5 is open. This piping 25 is connected to an adsorption column 30 in a constant temperature cooling bath 29 via paper traps 26 and 27 provided in two stages and an adsorption column inlet valve 28. This constant temperature bath 29 uses a cryogenic liquid such as liquid helium as a refrigerant, and the adsorption column 3
Adsorbs hydrogen and tritium flowing through the air. The outlet side of the adsorption column 30 is connected to the vacuum pump 3 via an adsorption column outlet valve 31 and a vacuum pump inlet valve 32.
3, and its tip is open to the atmosphere. Further, a gas transfer line 34 branched from between the valves 31 and 32 is connected to a cylinder 37 via a line valve 35 and a cylinder inlet valve 36.

In the apparatus of the present invention configured as described above,
Normally, liquid sodium from the secondary cooling system of a fast breeder reactor plant is introduced into the cold trap 10 through the inlet pipe 14, purified as it flows through the trap mesh 11 to release hydrogen and tritium, and then passed through the outlet pipe 17. It is sent back to the secondary cooling system. If the cold trap 10 is blocked, when regenerating it, the inlet valve 15 and outlet valve 18 are closed, the line valves 21 and 22 are opened, and the electromagnetic pump 16 is used to draw liquid sodium into the cold trap. 10 and the gas venting port 23. At this time, when the cold trap 10 is heated and maintained at a temperature of approximately 300°C or higher by the heater 13, the hydrogen and tritium captured in the trap mesh 11 are transferred to the gas venting pot 23 using liquid sodium as a carrier. .

The pressure inside this gas venting pot is reduced by the vacuum pump 33 attached to the tip of the gas venting pipe 25, and the pressure is lower than the hydrogen partial pressure, so hydrogen and tritium in the sodium migrate into the gas. It is discharged via the gas venting pipe 25. that time,
The exhaust gas is stripped of sodium vapor and sodium mist by vapor traps 26 and 27, and is further cooled to the temperature of, for example, helium. Hydrogen and tritium are adsorbed by sieves and activated carbon. Therefore, the gas released into the atmosphere through the open adsorption column outlet valve 31 and the vacuum pump inlet valve 32 does not contain sodium or tritium.

When the regeneration process of the cold trap 10 is completed as described above, the adsorption column inlet valve 28 and the vacuum pump inlet valve 32 are closed, the adsorption column outlet valve 31, the line valve 35 and the cylinder inlet valve 36 are opened, and the adsorption The column 30 is taken out from the constant temperature bath 29 and heated. In this way, the hydrogen and tritium adsorbed in the adsorption column 30 are heated and pressurized, and are transferred to the pump 37 and stored therein.

As described above, in the present invention, the hydrogen generated during the cold trap regeneration process and the tritium mixed therein are adsorbed once in the adsorption column, and after the regeneration process, the hydrogen is stored in a cylinder or the like and disposed of. Therefore, there is no problem such as tritium being emitted into the atmosphere and contaminating it.

FIG. 2 shows another embodiment of the invention. In this figure, the same components as in FIG. 1 are labeled with the same symbols.

As is clear from a comparison with FIG. 1, the embodiment shown in FIG. 2 has the same structure upstream of the vapor trap 27 as shown in FIG. And between this vapor trap 27 and the vacuum pump 33, there is another one.
Adsorption column inlet valve 28a, constant temperature bath 29 for cooling
a, adsorption column 30a, adsorption column outlet valve 31
a. The vacuum pump inlet valve 32a is bypassed and the line valve 35a is connected to the gas transfer line 34a branched from the adsorption column outlet valve 31a.
It is characterized in that its outlet side is shared with the outlet side of the line valve 35 and connected to cylinders 37, 37a arranged in parallel.

When using the apparatus shown in FIG. 2, the same effects as those shown in FIG. 1 can be expected, and continuous operation can be performed by switching the suction columns 30, 30a and the cylinders 37, 37a. In other words, while regenerating the cold trap using one adsorption column, the other full adsorption column is simultaneously heated to raise its temperature, and the hydrogen and tritium adsorbed inside are transferred and stored in the cylinder. can do.

As mentioned above, according to the present invention, although the energy is low, it is possible to prevent the release of tritium containing β radioactivity into the atmosphere, and since the cold trap is easily regenerated, the necessary cold trap can be saved. The number of bases can be drastically reduced.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are system diagrams showing embodiments of essential parts of the apparatus of the present invention. 10... Cold trap, 11... Trap mesh, 12... Cooling fan, 13... Heater, 14... Inlet piping, 15... Inlet valve, 16
...Electromagnetic pump, 17... Outlet piping, 18... Outlet valve, 19, 20... Recirculation line, 21, 22
... Line valve, 23 ... Gas vent pot, 24 ...
... Sodium liquid level, 25 ... Gas venting piping, 2
6, 27... vapor trap, 28, 28a...
Adsorption column inlet valve, 29, 29a... Constant temperature bath for cooling, 30, 30a... Adsorption column, 31, 31a
...Adsorption column outlet valve, 32, 32a...Vacuum pump inlet valve, 33...Vacuum pump, 34, 34a
...Gas transfer line, 35, 35a... Line valve, 36, 36a... Cylinder inlet valve, 37, 37
a...Cylinder.

Claims (1)

[Scope of Claims] 1. In a liquid metal refining device in which liquid metal is fed into a cold trap from an inlet pipe and purified liquid metal is discharged from an outlet pipe, the cold trap and the degassing port are connected by a recirculation line. A liquid metal refining device characterized in that an adsorption column is inserted in a gas vent pipe connected to the gas vent port to reduce the pressure inside the gas vent pot, and the gas adsorbed in the adsorption column can be transferred and stored in a cylinder. 2. The liquid metal refining apparatus according to claim 1, wherein a plurality of adsorption columns are connected in parallel via an inlet valve and an outlet valve.