JPS5953518B2 - Device for reducing hydrogen isotope permeation in piping systems of gas-cooled nuclear reactors and fusion reactors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for reducing the amount of permeation of hydrogen isotopes in piping systems of gas-cooled nuclear reactors and nuclear fusion reactors.

For example, Li is used as a material for fusion reactor blankets.

In piping systems where O gas is used and He gas is used as a coolant, especially in the coolant primary circulation loop, the generated hydrogen isotopes (H., D., T2) become H as impurities.
Exists in e-gas. Among these hydrogen isotopes, T. is about 1
They are radioactive impurities with a half-life of 2.5 years, and these hydrogen isotopes have the property of penetrating metal walls at high temperatures and leaking into the containment vessel and the secondary coolant circulation loop. If it leaks into the interior or the secondary coolant circulation loop, there is a risk of pollution due to radioactive contamination of the atmosphere. Also, the above T. Because it itself becomes nuclear fuel, it is necessary to recover as much as possible. Conventional methods for removing and recovering hydrogen isotopes from the primary coolant circulation loop of gas-cooled nuclear reactors and nuclear fusion reactors include absorbing them into titanium metal, and converting hydrogen isotopes into water using oxidation catalyst towers. There is a method of adsorbing the hydrogen isotope on a moisture absorbing material after the hydrogen isolating, but these methods cannot reduce the permeation of hydrogen isotopes from the piping of the primary coolant circulation loop, and the tower itself becomes large.

For this reason, the containment vessel must be expanded, making the gas-cooled nuclear reactor and nuclear fusion reactor plant large-scale, and the installation cost becomes enormous.

The present invention was made in view of the above circumstances, and it is possible to eliminate the need for conventional oxidation catalyst towers and hydrogen isotope removal towers.
Convert as much hydrogen isotope as possible to water within existing piping,
It is an object of the present invention to provide a device that reduces the partial pressure of hydrogen isotope gas and reduces the amount of hydrogen isotope permeated through piping.

The hydrogen isotope permeation amount reducing device according to the present invention is used in piping systems of fugas-cooled nuclear reactors and nuclear fusion reactors, from at least the core outlet of the coolant primary circulation loop to the inlet of an intermediate heat exchanger including a heat storage device. If the inner surface of the piping leading to the reactor is coated with an oxidation catalyst such as platinum or palladium, or a net of the oxidation catalyst is stretched, oxygen will be supplied to the piping near the reactor core exit and in the middle of the bypass pipe that detours around the reactor core. It is made up of connected systems. An example of this will be explained based on drawings in the case of a fusion reactor. Figure 1 shows an outline of the primary circulation loop of coolant in the piping system of a fusion reactor, and He gas as a coolant is The coolant primary circulation loop becomes high temperature through the reactor core 1, passes through the heat storage device 2, enters the intermediate heat exchanger 3, exchanges heat with He gas, which is the coolant of the coolant secondary circulation loop (not shown), and lowers the temperature. He gas is sent to Proa-14,
It is then sent to the core 1 again.

That is, He gas, which is the primary coolant, is circulated in a closed circuit for heat removal. In order to avoid thermal shock to the core blanket due to the pulse operation of the fusion reactor, He gas, which is a primary coolant, is periodically sent to the heat storage device 2 through a bypass pipe 5 that bypasses the core 1. Reference numeral 6 denotes a hydrogen isotope separation and recovery section, which separates water (described in detail later) that is sucked together with the He gas by the proa 1 4 from the He gas, and further separates and recovers the hydrogen isotope. However, in the hydrogen isotope permeation amount reduction device according to the present invention, in the primary coolant circulation loop, from the outlet of the core 1 to the regenerator 2.
An oxidation catalyst such as platinum or palladium is coated on the inner surface of the pipe 7 leading to the inlet of the intermediate heat exchanger 3 containing Oxygen supply systems 8 and 8'' are connected to the middle of a bypass pipe 5 that bypasses the oxygen supply system 1, respectively.

In the hydrogen isotope permeation amount reducing device of the present invention,
If the inner surface of the pipe 7 is coated with an oxidation catalyst such as platinum or palladium, the hydrogen isotopes present in the He gas, which is the coolant that exits the core 1 and passes through the pipe 7, and the oxygen supply system 8 from the pipe The oxygen injected into the pipe 7 diffuses toward the inner surface of the pipe 7.

When the gas eventually reaches the inner surface of the pipe 7, that is, the oxidation catalyst, the hydrogen isotope and oxygen are converted into water by its catalytic action. The reaction between this hydrogen isotope and oxygen is shown below using tritium as an example. In this way, the hydrogen isotope present in the H2 gas is gradually converted to water while passing through the pipe 7, so the partial pressure of the hydrogen isotope gas in the pipe 7 is reduced, and the hydrogen isotope from the pipe 7 is The amount of permeation can be reduced,
The leakage of hydrogen isotopes into the containment vessel can be sufficiently suppressed to below the permissible value.

Furthermore, since there is very little hydrogen isotope in the H2 gas that entered the intermediate heat exchanger 3 through the pipe 7, the hydrogen isotope gas partial pressure is extremely low and permeates through the heat exchanger tubes of the intermediate heat exchanger 3. The amount of hydrogen isotope flowing out into the secondary coolant circulation loop is very small and does not pose a safety problem.
On the other hand, if a net made of an oxidation catalyst such as platinum or palladium is installed on the inner surface of the pipe 7, hydrogen isotopes in the H2 gas exiting the reactor core and oxygen injected from the oxygen supply system 8 flow together in the pipe 7, and when they come into contact with the oxidation catalyst network,
Its catalytic action converts hydrogen isotopes and oxygen into water.

In this way, the hydrogen isotope in the H2 gas is gradually converted to water while passing through the pipe 7, so the partial pressure of the hydrogen isotope gas in the pipe 7 is reduced, and the amount of hydrogen isotope permeated from the pipe 7 is reduced. It has the same effect as above.

In this case, since the oxidation catalyst network is stretched over the inner surface of the pipe 7, pressure loss inside the pipe 7 becomes a problem, but this can be overcome by reducing the number of meshes or the number of meshes in the pipe 7. It is possible to set the pressure drop to a value that

On the other hand, if you want to increase the oxidation rate of hydrogen isotopes, in other words, if you want to convert them into water even more, you can do this by increasing the number of meshes or the number of meshes. That is, the number of meshes and the number of meshes may be determined based on the required oxidation rate of the hydrogen isotope and the allowable pressure loss. However, as mentioned above, the He gas that has entered the intermediate heat exchanger 3 exchanges heat with the He gas, which is the coolant of the secondary coolant circulation group, and its temperature is lowered. 1 and sucked together with the He gas, the water is sent to a hydrogen isotope separation and recovery section 6, where hydrogen isotopes are recovered while passing therethrough. In addition, in a fusion reactor, in order to avoid thermal shock to the core blanket due to pulse operation, He gas, which is a coolant, is periodically passed through a bypass pipe 5 to the core 1.
bypass.

In this case, oxygen is injected into the He gas passing through the bypass pipe 5 from the oxygen supply system 8'' connected midway through the bypass pipe 5, flows through the bypass pipe 5 together with hydrogen isotopes in the He gas, and flows into the heat storage device 2. Since an oxidation catalyst is coated or an oxidation catalyst network is installed on the inner surface of the pipe 7 containing the heat storage device 2, the He gas in the He gas passes through the heat storage device 2 and the pipe 7 as described above. The hydrogen isotope and oxygen react with each other through the catalytic action of the oxidation catalyst coating or network and are converted into water, gradually reducing the partial pressure of the hydrogen isotope gas in the pipe 7 and reducing the amount of hydrogen isotope permeated from the pipe 7. The above embodiment of the hydrogen isotope permeation amount reduction device according to the present invention is provided between the outlet of the core 1 of the primary coolant circulation loop and the inlet of the intermediate heat exchanger 3 including the heat storage device 2. However, an oxidation catalyst such as platinum or palladium for oxidizing hydrogen isotopes in He gas may be provided in the entire primary coolant circulation loop as shown in Figure 2, or in the third As shown in the figure, it is installed not only in the primary coolant circulation loop but also in the piping 7'' from the outlet of the primary intermediate heat exchanger 3 to the inlet of the steam generator 9 in the secondary coolant circulation loop. An oxygen supply system 8'' may be connected near the outlet of the heat exchanger 3.

In this way, in the example shown in Figure 2, hydrogen isotopes in the He gas can be converted to water even after the intermediate heat exchanger 3, so the permeation of hydrogen isotopes is extremely small, and hydrogen It is possible to increase the amount of isotope separation and recovery, and in the example shown in Fig. 3, it permeates through the intermediate heat exchanger 3 and flows into the He gas flowing through the pipe 7'' of the secondary coolant circulation loop. Safety can be ensured by converting the small amount of hydrogen isotope produced into water and preventing it from permeating through the pipe 7''. Furthermore, in the embodiment of the hydrogen isotope permeation amount reducing device according to the present invention shown in FIG.
Coating with an oxidation catalyst such as palladium or installing a net made of the oxidation catalyst is sufficient, but in cases where the required oxidation rate of hydrogen isotope is extremely high and the allowable pressure drop is small. In this case, it is preferable to coat the oxidation catalyst and provide an oxidation catalyst network.

As detailed above, according to the hydrogen isotope permeation amount reduction device according to the present invention, He gas exists at least in the piping from the core outlet of the coolant primary circulation loop to the intermediate heat exchanger inlet including the regenerator. Since the hydrogen isotope that is present in the pipe is oxidized and gradually converted to water, the partial pressure of the hydrogen isotope gas in the pipe is reduced, and the amount of hydrogen isotope that permeates from the pipe can be reduced. It is safe because the outflow of the body can be kept below the allowable value.

In addition, since the amount of hydrogen isotopes present in the He gas that entered the intermediate heat exchanger through the pipe is small, the hydrogen isotope gas partial pressure is extremely low, and the hydrogen isotope gas that passes through the heat exchanger tubes of the intermediate heat exchanger is The amount of hydrogen isotopes flowing out into the secondary coolant circulation loop can be kept below the permissible value and is therefore safe. Therefore, there is no need to expand the containment vessel as in the past, and it is possible to downsize the gas-cooled nuclear reactor and nuclear fusion reactor plant, thereby reducing installation costs. Furthermore, since the device of the present invention converts hydrogen isotopes in the He gas flowing through the piping into water as described above, the amount of hydrogen isotopes lost through permeation is small, and therefore the amount of hydrogen isotopes lost in the hydrogen isotope separation and recovery section is small. Since the amount of hydrogen isotopes that can be separated and recovered from the sent water is large, especially in the case of tritium, it can be used again as nuclear fuel, so increasing the amount of separated and recovered not only contributes to resource reuse, but also
This has the effect of reducing the operating cost, or fuel cost, of a nuclear fusion reactor.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the primary coolant circulation loop of a fusion reactor equipped with a hydrogen isotope permeation amount reduction device according to the present invention, and Fig. 2 is a schematic diagram of the primary coolant circulation loop showing a modification of Fig. 1. 3 are schematic diagrams of a primary coolant circulation loop and a secondary coolant circulation loop of a fusion reactor equipped with a device of the present invention. 1...Reactor core, 2...Regenerator, 3...
...Intermediate heat exchanger, 4,4''...Proa 1,
5...Bypass pipe, 6,6''...Hydrogen isotope separation and recovery section, 7,7''...Piping, 8,
8″, 8″″...Oxygen supply system, 9...
steam generator.

Claims (1)

[Claims] 1. In the piping systems of gas-cooled nuclear reactors and nuclear fusion reactors,
Coating at least an oxidation catalyst such as platinum or palladium on the inner surface of the piping from the core outlet of the coolant primary circulation loop to the inlet of the intermediate heat exchanger including the heat storage device, or extending a network of the oxidation catalyst, A device for reducing the permeation amount of hydrogen isotopes in the piping systems of gas-cooled nuclear reactors and nuclear fusion reactors, which comprises an oxygen supply system connected to the piping near the reactor core exit and in the middle of a bypass pipe that bypasses the reactor core.