JPS5953519B2 - nuclear steam generation plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of nuclear steam generation plants such as gas-cooled nuclear reactors and nuclear fusion reactors. The present invention relates to a nuclear steam generation plant in which leakage from a primary coolant circulation loop in a containment vessel to a secondary coolant circulation loop is prevented.

In general, nuclear steam generators such as gas-cooled nuclear reactors and nuclear fusion reactors are designed to extract heat generated in the reactor core without directly transmitting it to the steam generator, in order to prevent radioactive materials from being released to the outside. A primary coolant circulation loop and a secondary coolant circulation loop for further transmitting the heat extracted to the primary coolant circulation loop to the steam generator (or a tertiary coolant circulation loop for transferring the heat extracted to the secondary coolant circulation loop) The system consists of multiple circulation loops, including a coolant circulation loop that transmits the coolant to the steam generator.

An intermediate heat exchanger is used as a means of transmitting the heat extracted from the primary coolant circulation loop to the secondary coolant circulation loop, and this intermediate heat exchanger is the only primary coolant circulation loop and secondary coolant circulation loop. This is the contact area with the material circulation loop. On the other hand, in the reactor core, Li is used as a blanket material.

Since He gas is used as a coolant, a reaction of n+6Li■)T+4He+48MeV n+7Li-)T+4He+n'-25MeV takes place between the Li2O blanket and He gas, and a large amount of radioactivity is generated. Tritium (T), which is a hydrogen isotope tinged with hydrogen, is generated, mixes into the He gas as an impurity, and circulates within the primary coolant circulation loop.

This tritium is a radioactive impurity with a half-life of about 125 years, and at high temperatures it can pass through the piping of the primary coolant circulation loop and flow into the containment vessel, or it can pass through the heat transfer tubes of the intermediate heat exchanger. It mixes into the coolant of the secondary coolant circulation loop, and then leaks out through the piping of the secondary coolant circulation loop and the metal walls of each device, causing pollution due to radioactive contamination of the atmosphere. occurs. Furthermore, since tritium itself becomes nuclear fuel in a fusion reactor, it is necessary to recover as much as possible. Conventionally, as a measure against the permeation of tritium from the intermediate heat exchanger to the secondary coolant circulation loop, tritium removal using titanium metal was carried out from the core of the primary coolant circulation loop to the intermediate heat exchanger '5. By installing a tower, tritium in He gas is absorbed by titanium metal, or by installing an oxidation catalyst tower, converting tritium in He gas into water and then absorbing it into a moisture absorbent material.
The concentration of tritium contained in He gas was lowered to below the allowable value.

However, if these tritium removal towers and oxidation catalyst towers deteriorate during operation of a nuclear steam generation plant such as a gas-cooled nuclear reactor or a nuclear fusion reactor, the tritium concentration in the He gas entering the intermediate heat exchanger may drop below the permissible value. The tritium removal tower and the oxidation catalyst tower must be designed and manufactured with strict precision so that their functionality does not deteriorate, and the tritium removal tower and oxidation catalyst tower must be designed and manufactured strictly to avoid functional deterioration. Requires equipment to compensate for functional decline. In addition, since the tritium removal tower and oxidation catalyst tower are quite large, the containment vessel that houses the primary coolant circulation loop including these towers is also large, so it is difficult to use in gas-cooled nuclear reactors and nuclear fusion reactors. Nuclear steam generation plants such as these have become large-scale, and the equipment costs have become enormous. The present invention has been made in view of the above situation, and the tritium concentration in the He gas entering the intermediate heat exchanger is reduced to a permissible value due to the function of the tritium removal tower or oxidation catalyst tower in the primary coolant circulation loop being reduced. or He enters the intermediate heat exchanger when it functions normally.
Even if the tritium concentration in the gas is below the allowable value, the tritium mixed in the He gas is always converted to water in the intermediate heat exchanger, and the permeation of tritium from the heat transfer tubes of the intermediate heat exchanger is minimized. It is an object of the present invention to provide a nuclear steam generation plant that prevents tritium from leaking into the secondary coolant circulation loop as much as possible.

In the nuclear steam generation plant according to the present invention, an oxidation catalyst such as platinum or palladium is coated on the entire heating side of the intermediate heat exchanger through which the primary coolant passes, and the intermediate heat exchanger in the primary coolant circulation loop is This system is characterized by an oxygen supply device connected near the entrance to the system.

An example of this will be described below with reference to the drawings in the case of nuclear fusion.

The figure shows an outline of the primary coolant circulation loop A and the secondary coolant circulation loop B in the piping system of a fusion reactor.
He gas, which is a coolant, reaches a high temperature through the core 1, passes through a heat storage device 2, a tritium removal tower or an oxidation catalyst tower 3, and enters an intermediate heat exchanger 4, where it becomes a coolant for the secondary coolant circulation loop B. The primary coolant circulation loop A (7) He gas, which has undergone heat exchange with the He gas and whose temperature has decreased, is sent to the reactor core 1 again by the proar 5. That is, He gas, which is the primary coolant, is circulated in a closed circuit to remove heat. In order to avoid thermal shock to the blanket part due to the pulse operation of the core 1 of the fusion reactor (in a fusion reactor, the inside of the reactor is periodically evacuated to remove impurities generated in the plasma). The He gas is sent to the regenerator 2 through a bypass pipe 6 that periodically bypasses the reactor core. 7 is a tritium separation and recovery system, which separates water (described in detail later) that is sucked together with He gas by Proa-1 5 from He gas;
It also separates and recovers tritium. However, in such a primary system coolant circulation loop of a fusion reactor, the present invention is directed to the entire surface of the heating side through which He gas, which is the primary system coolant of the intermediate heat exchanger 4, passes, that is, the outer shell of the intermediate heat exchanger 4. 4
An oxidation catalyst 8 such as platinum or palladium is coated on the inner surface of the tube a and the outer circumferential surface of all the heat transfer tubes 4b, and the intermediate heat exchanger 4 of the pipe 9 is connected from the tritium removal column or the oxidation catalyst column 3 to the intermediate heat exchanger 4. An oxygen supply device 10 is connected to the vicinity of the inlet.

In the nuclear steam generation plant of the present invention, the He gas that has become high temperature through the reactor core 1 passes through the heat storage device 2 and enters the tritium removal tower or oxidation catalyst tower 3, where tritium in the He gas is removed from the tritium removal tower. The water absorbed by the titanium metal or converted into water in the oxidation catalyst tower is absorbed by the moisture absorbing material in the separation and recovery system 7.

) The tritium concentration is reduced below the permissible value. Then, this He gas enters the heating side of the intermediate heat exchanger 4 from the tritium removal tower or the oxidation catalyst tower 3 through the pipe 9. Further, the oxygen injected into the pipe 9 from the oxygen supply device 10 enters the heating side of the intermediate heat exchanger 4. Then, the oxygen and tritium in the He gas diffuse toward the inner surface of the outer shell 4a and the outer peripheral surface of the heat exchanger tube 4b. When the tritium and oxygen eventually reach the inner surface of the outer shell 4a and the inner surface of the heat transfer tube 4b, that is, the oxidation catalyst 8, the tritium and oxygen are converted into water by their catalytic action. The reaction between tritium and oxygen is as follows. In this way, the tritium present in the He gas enters the intermediate heat exchanger 4, and the He gas exchanges heat with the He gas, which is the secondary coolant in the heat transfer tube 2b, and the intermediate heat exchanger 4 is heated. Before it leaves, most of it is converted to water.

Therefore, the tritium concentration in the He gas, which had been lowered below the permissible value before entering the intermediate heat exchanger 4, further decreases, and the gas partial pressure of tritium in the intermediate heat exchanger 4 becomes extremely low. The permeation of tritium from the shell 4a and the heat transfer tubes 4b is extremely reduced, and the outflow of tritium to the secondary coolant circulation loop B side can be prevented as much as possible, so it is extremely safe. Furthermore, even if the function of the tritium removal tower or the oxidation catalyst tower 3 deteriorates and the tritium concentration in the He gas entering the heating side of the intermediate heat exchanger 4 exceeds the permissible value, the tritium concentration in the He gas is the outer shell 4a along with oxygen on the heating side of the intermediate heat exchanger 4 as described above.
and the outer circumferential surface of the heat transfer tube 4b,
When the He gas reaches the oxidation catalyst 8, its catalytic action converts tritium and oxygen into water, so before the He gas leaves the heat exchanger 4, most of the tritium in the He gas is converted to water, and the He gas The tritium concentration in the gas will be significantly lowered below the permissible value.

Since the tritium gas partial pressure in the He gas is greatly reduced, the amount of tritium that permeates through the inner surface of the outer shell 4a and the outer peripheral surface of the heat transfer tube 4b and flows out to the secondary coolant circulation loop is extremely small. There is no problem in terms of safety. In this way, the tritium mixed in the intermediate heat exchanger 4 is converted into water, and the temperature of the He gas, which is the primary coolant, is reduced by heat exchange with the He gas in the secondary coolant circulation loop.
The water is sent to the reactor core 1 again by the proar 15 and sucked together with the He gas, and the water is sent to the tritium separation and recovery system 7, where tritium is recovered while passing through this system.

Note that the nuclear steam generation plant of the present invention includes an intermediate heat exchanger 4
By simply coating an oxidation catalyst such as platinum or palladium on the inner surface of the outer shell 4a and the outer peripheral surface of the heat transfer tubes 4b, which are the heating side of the Although it is possible to sufficiently prevent the outflow of tritium, in consideration of an emergency situation in which the tritium removal tower or oxidation catalyst tower 3 is damaged due to some kind of accident and does not function at all, it is necessary to provide an intermediate heat exchanger 4 for greater safety. Hot side outer shell 4a
A network of oxidation catalysts made of platinum, palladium, etc. is further disposed inside the interior of the intermediate heat exchanger 4 to almost completely convert tritium in the He gas entering the heating side of the intermediate heat exchanger 4 into water, thereby converting the tritium into water as a primary coolant. It is also possible to prevent the coolant from flowing from the circulation loop A to the secondary coolant circulation loop B.

As detailed above, according to the nuclear steam generation plant according to the present invention, He gas passing through the heating side of the intermediate heat exchanger, which is the contact part between the primary coolant circulation loop and the secondary coolant circulation loop, Since the tritium present in the concentration below the permissible value is oxidized and almost converted to water, the permeation of tritium through the heat transfer tubes of the intermediate heat exchanger becomes extremely small.
It is extremely safe because the outflow of tritium into the secondary coolant circulation loop can be prevented as much as possible.

In addition, if the functionality of the existing tritium removal tower or oxidation catalyst tower installed in the primary coolant circulation loop is degraded or damaged and does not function, tritium in the He gas entering the heating side of the intermediate heat exchanger may be tolerated. However, while passing through the intermediate heat exchanger, most of the tritium is converted to water and the tritium concentration in the He gas is significantly lowered below the allowable value, so the tritium in the intermediate heat exchanger is The gas partial pressure becomes extremely low, and therefore the amount of tritium that passes through the heat exchanger tubes and flows out into the secondary coolant circulation loop is extremely small and poses no safety problem. Furthermore, as mentioned above, most of the tritium present in the He gas is converted to water on the heating side of the intermediate heat exchanger, and the amount of tritium lost by permeating through the heat transfer tube is extremely small. Since the amount of tritium that is separated and recovered from the water sent to the separation and recovery system is large, increasing the amount of separated and recovered not only contributes to resource reuse, but also reduces the operating cost, or heating cost, of the fusion reactor. can be reduced.

Furthermore, as mentioned above, even if the tritium concentration in the He gas entering the heating side of the intermediate heat exchanger is above the permissible value, tritium is converted to water and greatly reduced to below the permissible value. Not only can the strict design and manufacture of the tritium removal tower and oxidation catalyst tower be replaced with relatively rough design and manufacture, but they can also be made more compact.

Therefore, there is no need to expand the containment vessel, the nuclear steam generation plant can be downsized, and installation costs can be reduced.

[Brief explanation of drawings]

The figure is a schematic diagram of a primary coolant circulation loop and a secondary coolant circulation loop in the piping system of a nuclear fusion reactor, which is an example of a nuclear steam generation plant according to the present invention. 1...Reactor core, 2...Regenerator, 3...
...Tritium removal tower or oxidation catalyst tower, 4...
・Intermediate heat exchanger, 4a... Outer shell, 4b...
... Heat exchanger tube, 5 ... Proa 1, 6 ...
Bypass pipe, 7... Tritium separation and recovery system, 8
... Oxidation catalyst, 9 ... Piping, 10 ...
...Oxygen supply device, A...Primary system coolant circulation loop, B...Secondary system coolant circulation loop.

Claims (1)

[Claims] 1 In a nuclear steam generation plant, an oxidation catalyst such as platinum or palladium is coated on the entire heating side of the intermediate heat exchanger through which the primary coolant passes, and the intermediate heat exchanger in the primary coolant circulation loop is coated with an oxidation catalyst such as platinum or palladium. A nuclear steam generation plant characterized by having an oxygen supply device connected near the entrance to the plant.