JPS645669B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a component of a forced cooling circuit that cools spent fuel in combination with equipment that handles spent fuel in a sodium-cooled nuclear reactor, such as a fuel transfer machine. This invention relates to an improvement in a sodium mist trap for removing sodium vapor that is present in the air.

Spent fuel extracted from the above reactor has a high level of calorific value, so it is transferred to an ex-core fuel storage tank that uses liquid metal sodium as a coolant, where the level of calorific value of ring collapse is reduced. It is stored until it is reduced enough to be safely handled in a gas atmosphere. After that, the fuel is taken out from the storage tank individually,
After undergoing sodium cleaning and bottling processes, it is stored in a storage pool. In this case, even when the spent fuel is being pulled out from the storage tank by the fuel loading/unloading machine and transferred to the next process, the spent fuel continues to generate heat due to ring collapse, and in order to prevent fuel damage due to temperature rise during the transfer,
Generally, a forced cooling circuit is connected to the fuel inlet/outlet machine housing the spent fuel, and inert gas is forced to circulate through it to cool the fuel forcibly. Sodium adheres to the surface of the fuel taken out from the out-of-core fuel storage tank, and by passing the cooling gas through the fuel, the cooling gas contains sodium vapor. The freezing point of sodium is approximately 100°C, whereas the surface temperature of the spent fuel stored in the Cofin and transported is much higher, for example, around 500°C.
On the other hand, the forced cooling circuit is configured to cool the gas extracted from the cofuin through heat exchange with a cooler, and send it back to the cofuin via a fan.
In this case extracted from Cohuin as an example
Gas at around 200℃ is cooled to around 80℃ in a cooler due to the operating temperature limit of the fan in the latter stage before being introduced into the fan, and furthermore, the gas discharged from the fan is designed to avoid thermal shock to the fuel. It is reheated to around 150℃ and then sent to Cohuin. If the forced cooling circuit is operated under such temperature conditions, sodium vapor in the gas will solidify and accumulate on the cooler and other circuit equipment, which has a low temperature, leading to a decline in the cooling circuit function or equipment failure. To prevent this, conventionally a sodium mist trap was inserted into the circuit before the cooler.
A widely used method is to remove sodium vapor by adsorbing it to a filter. The filters used here are made by, for example, knitting thin stainless steel wires or entwining them around a base frame, and their sodium adsorption action is based on pure mechanical filtration and the condensation of sodium vapor. It was carried out by However, conventional sodium mist traps have low performance and cannot provide a sufficient filter effect, and there is a demand for improved performance.

This invention has been made in view of the above points, and its purpose is to provide a high-performance sodium mist trap by utilizing the physical properties of sodium.

This purpose is achieved by the present invention, in which a trap body comprising a sodium filter loaded in a case,
From a heat pipe equipped with a heat absorbing part that is in close contact with the periphery of the case for thermal conduction, and a heat radiating part that penetrates a shielding material that shields the radiation of the cooling gas using the case as a cover and is drawn out into the atmosphere. This is achieved by providing a forced cooling means to cool the sodium filter below the sodium solidification temperature, thereby actively coagulating and adsorbing the sodium vapor passing through the trap.

The present invention will be described in detail below based on illustrated embodiments.

First, Figure 1 shows a system diagram of the spent fuel forced cooling circuit combined with the fuel inlet/outlet machine. In the figure, 1 is an extra-core fuel storage tank that uses sodium 2 as a coolant and has a built-in fuel storage rack 3 inside the tank, 4 is its upper door valve, and 5 is a fuel inlet/outlet machine mounted on a traveling truck (not shown). , 6 is the lower door valve of the co-fin, 7 is the gripper for grabbing fuel, 8 is the gripper lifting mechanism, 9 is the gripper 7
This is the spent fuel lifted from the fuel storage tank 1 and stored in the co-fin 5. A sodium mist trap 10, a gas cooler 11, a fan 12, and a gas reheater 13, which are objects of the present invention, are sequentially connected to the cofin 5 between its gas outlet 51 and inlet 52 to force Cooling circuit 1
4 are configured. The cofin 5 is filled with an inert gas such as argon gas, and this gas is used as a heat medium to be circulated between the cooling circuit 14 and the cooling circuit 14 as shown by the arrow, thereby removing the decay heat of the fuel 9 and forcibly cooling it. do.

Next, the structure of the sodium mist trap 10 incorporated in the above circuit will be described with reference to FIGS. 2 and 3. In other words, the sodium mist trap 10 is
A case 103 made of stainless steel having a gas inlet 101 and an outlet 102, a radiation shielding material 104 made of lead that surrounds the outer periphery of the case and shields radiation from the cooling gas, and is loaded in a cassette type inside the case. Sodium filter 105 and base 106
In addition, a large number of heat pipes 107 are disposed on the outer peripheral surface of the case 103 as means for forcedly cooling the trap body. These heat pipes 107 are installed so that their heat absorbing portions are in close contact with the case 103 for thermal conduction, and their heat radiating portions are drawn out into the surrounding atmosphere through the insulation material 104. 108 is a heat radiation fin. Further, the sodium filter 105 is constructed by, for example, a zigzag-shaped filter base frame entwined with thin stainless steel wire, and is loaded into the case 103 in a cassette type so that the filter can be easily replaced. In this case, the sodium filter 105 is preferably set within the case 103 so that good heat conduction can be obtained between the sodium filter 105 and the peripheral wall of the case 103.

According to the above configuration, heat from the case 103 and the filter 105 loaded in the case can be dissipated into the surrounding atmosphere by the action of the heat pipe 107, thereby maintaining the temperature at a low temperature. As a result, the sodium vapor that has flowed into the trap body together with the unused gas is lowered to below the solidification temperature in the process of passing through the filter 103, and is efficiently condensed onto the filter. In this way, a sodium mist trap with high adsorption performance can be obtained in combination with the mechanical filtration action of the filter described above. Note that it is also possible to use cooling means other than heat pipes as the forced cooling means. However, heat pipes do not require power or maintenance, and since the working fluid is sealed within the pipe, they have practical effects such as there is no risk of reaction with sodium, which is highly chemically active. .

[Brief explanation of drawings]

FIG. 1 is a system diagram of a forced cooling circuit combined with a fuel inlet/outlet device, FIG. 2 is a vertical side view of an embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along the direction of the arrow in FIG. 5... Coin, 9... Spent fuel, 10... Sodium mist trap, 11... Cooler, 12... Fan, 101... Gas inlet, 102... Gas outlet, 10
3... Case, 105... Sodium filter, 10
7...Heat pipe.

Claims (1)

[Claims] 1 Sodium mist in a forced cooling circuit for spent fuel configured to forcibly circulate cooling gas by sequentially externally connecting a sodium mist trap, a cooler, and a fan to a co-fin that houses the spent fuel of a sodium-cooled nuclear reactor. It's a trap,
A trap body consisting of a sodium filter loaded in a case having a gas inlet and an outlet, and a heat dissipation section extending into the atmosphere through a shielding material that covers the case and shields radiation from the cooling gas. A sodium mist trap in a forced cooling circuit for spent nuclear reactor fuel, characterized in that a forced cooling means consisting of a heat pipe is provided.