JPS6227917Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a direct cooling gas circuit for a fuel inlet/output machine of a liquid metal cooled fast breeder reactor.

Spent fuel from liquid metal cooled fast breeder reactors has an extremely large decay calorific value when removed from the reactor vessel, so it is placed in a pot filled with liquid metal (usually sodium) and kept in an inert gas atmosphere to prevent it from melting. The fuel is drawn into the container and transferred to the external fuel storage tank while forcibly cooling the outer wall of the container, and the decay calorific value is sufficiently reduced in the external fuel storage tank, so that even when handled in gas, the fuel will not melt or break. It is stored until it no longer occurs. At this stage, the fuel alone is taken out of the out-of-core fuel storage tank and is carried out of the reactor through procedures such as cleaning, canning, and cask loading. A typical cooling method when a single fuel is taken out from an external fuel storage tank, stored in a fuel loading/unloading machine, and transferred will be explained with reference to FIG. 1 as follows.

That is, first, the spent fuel 10 is lifted from the ex-core fuel storage tank 12 by the gripper 14 and the gripper drive device 16 and stored in the fuel loading/unloading machine 18 . Note that the time required for lifting is several minutes, and forced cooling of the fuel during lifting is usually not performed.

Next, after storing the spent fuel 10 in the fuel loading/unloading machine,
Entrance/exit machine side door valve 20 and floor side door valve 2
2 and start the direct cooling blower 24. In this case, in order to prevent the sodium adhering to the spent fuel 10 and the grippers 14 from sticking, the inlet temperature of the fuel inlet/outlet machine 18 is set to 150°C by the heater 26.
It is necessary to raise the temperature to a certain degree.

Furthermore, the inert gas for direct cooling sent into the fuel inlet/outlet machine 18 passes through the inside of the spent fuel 10 and then passes through the mist trap 28 to the cooler 30.
cooled down.

However, such conventional spent fuel cooling systems have the following drawbacks. In other words, since the blower is started after the spent fuel is stored in the fuel inlet/outlet machine, it is impossible to instantly raise the inlet temperature of the fuel inlet/outlet machine to approximately 150°C, and therefore, measures to prevent sodium solidification are not possible. Enough is enough.
Furthermore, if prevention of solidification of sodium adhering to spent fuel and grippers is insufficient, the cooling path for spent fuel will become smaller, increasing flow path resistance and making it impossible to secure the flow rate necessary for cooling. As a result, cooling capacity decreases.

Therefore, the purpose of this invention is to overcome the above-mentioned difficulties and provide a more reliable cooling gas circuit for spent fuel with simple equipment.

In order to achieve this purpose, this invention consists of a series circuit of a coolant mist trap, a cooler, a blower, and a heater, and the coolant mist trap side end and the heater side end of the series circuit are connected through valves, respectively. In the cooling gas circuit of the fuel intake/discharge machine connected to the fuel intake/discharge machine, a valve is operated to open and close the series circuit in order to maintain a constant temperature at the outlet of the coolant heater and maintain a specified flow rate. The feature is that bypass circuits equipped with flow rate regulators are connected in parallel.

Next, a typical embodiment of this invention will be described in detail below with reference to FIG.

The fuel inlet/output device 32 includes a main body 34 including a co-fin and a shield, a gripper drive device 36 installed on the main body, and a gripper 40 suspended from the gripper drive device 36 via a stainless steel tape 38.
and a door valve 42 provided at the bottom of the main body 34.
The gripper 40 holds the spent fuel 44.

A direct cooling system 46 for spent fuel is connected between the upper and lower parts of the main body of the fuel inlet/outlet machine.

In the direct cooling system 46, an electric valve 48, a mist trap 50, a cooler 52, a blower 54, a heater 56, and an electric valve 58 are sequentially arranged at predetermined intervals.

Electric valve 48, mist trap 50, and electric valve 5
A bypass 60 is provided between the heater 8 and the heater 56, and an electric valve 62 and a flow rate regulator 64 are arranged on the bypass 60 at a predetermined interval.

Next, the operation of the direct cooling system of the fuel inlet/outlet machine according to the present invention configured in this way will be explained.
8 and the electric valve 58 are closed, while the electric valve 62 is open. When the blower is started in this state, a specified flow rate is set under the action of the flow rate regulator 64 in the bypass circuit, and the outlet temperature of the heater 56 is controlled to be approximately 150°C. Heater 56
After the outlet temperature becomes constant at approximately 150°C, the spent fuel is stored in the fuel inlet/outlet machine 32, the door valve 42 of the fuel inlet/outlet machine is closed, and the electric valves 48 and 5 are closed.
8 is gradually opened, while the electric valve 62 is closed.

According to the spent fuel cooling system according to the invention described above, gas with a temperature below about 150°C is not introduced into the fuel inlet/outlet machine, so the sodium attached to the grippers and spent fuel does not solidify. and,
Since sodium solidification is completely prevented, not only is the spent fuel reliably cooled, but the cooling path is constant, so the cooling flow rate is guaranteed, and a decline in cooling capacity can be prevented.

Although the typical embodiment of the direct cooling system for the fuel inlet/outlet machine according to this invention has been described above, it goes without saying that various changes can be made without departing from the spirit of this invention. for example,
Any suitable resistor can be selectively used as a flow regulator.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional direct cooling system of a fuel inlet/outlet machine, and FIG. 2 is an explanatory diagram of a direct cooling system of a fuel inlet/outlet machine according to this invention. 10...Spent fuel, 12...Outside fuel storage tank, 14...Gripper, 16...Gripper drive device, 18...Fuel inlet/outlet machine, 20...Door valve,
22...Floor side door valve, 24...Blower, 26
... Heater, 28 ... Mist trap, 30 ...
Cooler, 32...Fuel intake/discharge machine, 34...Main body, 3
6...Gripper drive device, 38...Stainless steel tape, 40...Gripper, 42...Door valve,
44... Spent fuel, 46... Direct cooling system, 48
...Electric valve, 50...Mist trap, 52...
Cooler, 54... Blower, 56... Heater, 58
...Motorized valve, 60...Bypass, 62...Motorized valve, 64...Flow rate regulator.

Claims (1)

[Scope of utility model registration request] The fuel inlet/outlet is equipped with a series circuit of a coolant mist trap, a cooler, a blower, and a heater, and the coolant mist trap side end and the heater side end of this series circuit are connected to the co-in of the fuel inlet/outlet machine via valves, respectively. In the cooling gas circuit of the machine, a bypass circuit is connected in parallel to the series circuit, which is equipped with a valve and a flow rate regulator that are operated to open and close in order to maintain a constant temperature at the outlet of the coolant heater and a specified flow rate. A cooling gas circuit for a fuel inlet/outlet machine.