JPS6324274B2 - - Google Patents

Description

Detailed Description of the Invention The present invention uses hydrogen isotope gas, which is an unreacted fuel substance, and helium gas, which is a reaction ash substance, contained in the exhaust gas of a nuclear fusion reactor, to improve the hydrogen isotope permeability of a palladium alloy plate. This invention relates to a nuclear fusion device that separates nuclear fusion plasma by utilizing the vacuum evacuation effect.

Generally, in order to cause a nuclear fusion reaction using hydrogen isotope plasma, the fusion plasma density must be
It is necessary to make the plasma temperature 1.5×10 ²⁰ m ^-3 or more, the plasma temperature 10 keV or more, and the plasma confinement time 1 second or more. On the other hand, as a result of the hydrogen isotope fusion reaction, helium ions are produced as reaction ash material. The generated helium ions act to increase the plasma pressure, and as a result, become a cause of unstable plasma discharge. From the standpoint of maintaining and continuing stable fusion plasma, the maximum allowable helium ion accumulation amount is 10% of the total number of plasmas.
If the number of helium ions increases beyond this level, it will no longer be possible to maintain a stable plasma discharge, that is, it will no longer be possible to continue the nuclear fusion reaction. Therefore, in order to sustain the fusion reaction, it is necessary to selectively exhaust and remove helium ions so that the concentration of helium ions contained in the fusion plasma is always 10% or less.

Conventionally, the plasma collection method for removing helium ions contained in fusion plasma from fusion plasma has been to guide fusion plasma to a divertor chamber using magnetic lines of force (divertor action).
A divertor method and a limiter method in which plasma particles are directly collected using a mechanical limiter have been considered. By these methods, particles constituting the plasma are converted into electrically neutral hydrogen isotopes and helium gas, which are then evacuated and removed using a vacuum pump such as a cryopump or a turbomolecular pump. However, due to their performance, known vacuum pumps such as cryopumps and turbomolecular pumps cannot selectively exhaust and remove only helium gas, so they must also exhaust and remove hydrogen isotope gas, which is unreacted fuel material. It has the property of causing Therefore, a vacuum evacuation device with a larger evacuation capacity than necessary is required. For example, when comparing the amount of increase in pumping capacity of a vacuum pumping system by pumping out hydrogen isotopes together with helium, when using a cryopump of 100,000 sec ^-1 , pumping only helium gas is 42~ 70 Torr・・
Although an exhaust capacity of sec ^-1 is sufficient, if hydrogen isotopes of unreacted fuel materials are also exhausted at the same time, the exhaust capacity is 420 sec -1.
It will be necessary to install a cryopump with a pumping capacity of ~700 Torr...sec ^-1 , or about 10 times as much. Therefore, in the conventional helium exhaust removal method from fusion plasma, (1) the fuel utilization efficiency of hydrogen isotope, which is a fuel substance, decreases; (2) hydrogen isotope is also exhausted and removed at the same time as helium gas, so (3) Because the load on the pump increases and a vacuum pump with a large pumping capacity is required, the construction cost of the equipment increases. The disadvantage is that operation and maintenance become complicated and operating costs increase. For this reason, there has been a strong desire to develop a nuclear fusion device that can efficiently separate hydrogen isotope and helium gas from a mixed gas of hydrogen isotope and helium at the front stage of a vacuum pumping device.

The inventors of the present invention have conducted intensive research to develop a nuclear fusion device that can efficiently separate hydrogen isotopes and helium gas, and have found that only hydrogen isotopes are selectively permeable in a moderate temperature range of palladium alloy plates. We have discovered that by combining the characteristics of fusion plasma with the ability to select and separate all types of gases, it is possible to create a fusion device that has the ability to efficiently separate helium and hydrogen isotope gases. In other words, it is known that palladium alloy plates have the property of only allowing hydrogen isotopes to permeate from the high-pressure side to the low-pressure side if there is a pressure difference between the hydrogen isotopes before and after the palladium alloy plate in a moderate temperature range. Utilizing this characteristic, it plays the role of selectively permeating and separating only hydrogen isotopes from a hydrogen isotope/helium mixture gas.
On the other hand, nuclear fusion plasma reduces the hydrogen isotope pressure on the exhaust side (low pressure side) of the palladium alloy plate due to its selection and separation effects, creating a constant hydrogen isotope pressure difference across the palladium alloy plate. play the role of

The present invention is a nuclear fusion device that efficiently separates hydrogen isotopes and helium gas by combining the characteristics of the above-mentioned palladium alloy plate and nuclear fusion plasma.

The nuclear fusion device having a hydrogen isotope/helium separation function of the present invention includes a palladium alloy plate attached to the first wall of the fusion device, a part of the radiation shield or the blanket, and a heating heater provided on the palladium alloy plate. Furthermore, it is composed of a movable slit plate that variably controls the flow rate of the exhaust gas mixture flowing into the vacuum exhaust system.

More specifically, the nuclear fusion device of the present invention includes:
In a nuclear fusion reactor consisting of core plasma and a highly vacuum vessel configured of a first wall containing the core plasma, a blanket, a radiation shield, and an outer wall, there is unreacted fuel material between the blanket and the radiation shield. A passage leading to the exhaust vacuum system for fusion plasma exhaust gas consisting of hydrogen isotope gas and helium as a fusion reaction product (ash substance) is provided, and an opening is provided in the passage through the first wall and the blanket. a palladium alloy plate having a property of transmitting a hydrogen isotope gas at a specific temperature is attached to the opening, and a heating means is provided on the palladium alloy plate. This is a nuclear fusion device that has the function of separating hydrogen isotopes and helium by circulating isotopic hydrogen into the core plasma.

Note that the palladium alloy plate used in the present invention has the following characteristics.

Composition: Pd:Ag=0.76:0.24 (atomic ratio) Operating temperature: Around 500℃ Hydrogen isotope permeation characteristics: 7 in terms of pumping speed
~15 1Sec ^-1 cm ^-2 (When alloy plate thickness: 0.1 mm) To explain a specific example of the device of the present invention with reference to drawings, in Fig. 1, a part of blanket 1 of a torus fusion device with a divertor is A palladium alloy plate 3 with a heater 2 is attached. Further, a movable slit plate 5 is provided in the exhaust gas passage between the blanket 1 and the radiation shield 4 to variably control the flow rate of the exhaust gas mixture. The fusion plasma (consisting of hydrogen isotope ions and helium ions) 6 collides with the divertor plate 7 in the divertor chamber under the action of the divertor magnetic field coil (not shown) according to the solid arrow, and removes the retained electric charge. The particles are released to the diverter plate 7 and become electrically neutral particles. These electrically neutral hydrogen isotopes and helium gas pass through the passage between the blanket 1 and the radiation shield 4 according to the solid line arrow, and the overall flow rate is controlled by the movable slit 5, and then the palladium alloy plate 3 The hydrogen isotope and helium gas are separated at the portion, and the hydrogen isotope passes through the palladium alloy plate 3 as indicated by the solid line arrow and is returned to the plasma by the selection and separation action of the fusion plasma 6 to be reused as fuel. On the other hand, helium passes through an exhaust duct 8 and a vacuum valve 9, and is exhausted and removed by a known vacuum pump 10 such as a cryopump or a turbomolecular pump. FIG. 2 shows a detailed view of section A in FIG. 1. Palladium alloy plate 3
As a heating method, a thermal filament is attached near the palladium alloy plate to perform heating action and a thermal dissociation reaction of molecular hydrogen isotopes to atomic hydrogen isotopes at the same time, indirect heating method, direct heating method of palladium alloy plate, etc. Any one of an electrical heating method, a heating method using thermal radiation from nuclear fusion plasma, a heating method using heat generated by a blanket, or any combination thereof may be used.

The palladium alloy plate has a bellows shape in order to increase the permeation area of hydrogen isotopes and improve the mechanical strength of the structure. Furthermore, in order to prevent the palladium alloy plate 3 from being directly exposed to neutral high-energy particles leaking from the fusion plasma due to charge exchange reactions and being damaged by sputtering and blistering effects, for example, the blanket 1 is A part of the palladium alloy plate is made to protrude between the palladium alloy plate 3 and the fusion plasma 6, so that the structure is such that the palladium alloy plate cannot be directly seen from the fusion plasma 6. The movable slit plate 5 for variably controlling the flow rate of the exhaust gas mixture is installed upstream of the palladium alloy plate, and may have any structure as long as it can variably control the gas flow rate.

In summary, the nuclear fusion device of the present invention is constructed by utilizing the following two principles and functions.

1 When a palladium alloy plate is heated and maintained at a moderate temperature (for example, around 500°C) with a difference in hydrogen isotope gas pressure across the palladium alloy plate, the hydrogen isotope gas on the side with higher hydrogen isotope gas pressure permeates and moves through the palladium alloy plate and flows toward the side with lower hydrogen isotope gas pressure. The fact that this phenomenon only occurs when a palladium alloy plate and hydrogen isotope gas are combined, and 2. Fusion plasma can maintain itself in space while at the same time absorbing all types of plasma that exist around it. It has the characteristic of ionizing gas, attracting it into the fusion plasma, and self-retaining it, and as a result, the gas existing around the plasma is pumped out in an extremely large amount, which is determined approximately in proportion to the surface area of the fusion plasma. The fact that it has the ideal vacuum pump function of constantly selecting and separating at speed.

The effects of the present invention, which is constructed using the above two facts, will be explained in more detail with reference to the drawings. 6 and the palladium alloy plate 3 as a boundary, and when the fusion plasma 6 is generated, the gas in the space existing between the fusion plasma 6 and the palladium alloy plate 3 becomes the fusion plasma. Due to the vacuum pump function of lower than the side. That is, a pressure gradient from a higher gas pressure side to a lower gas pressure side always exists in the direction of the fusion plasma 6 through the palladium alloy plate 3. On the other hand, when the palladium alloy plate 3 is heated and maintained at about 500° C., only the hydrogen isotope permeates through the palladium alloy plate 3 from the high gas pressure side to the low gas pressure side, as described above. Therefore, the inside of the exhaust duct 8 is vacuum-exhausted by the evacuation device 1.
From the mixed exhaust gas of hydrogen isotope gas and helium flowing in the direction of 0, only the hydrogen isotope gas passes through the palladium alloy plate 3 according to the arrow and constantly flows back to the fusion plasma side.

A nuclear fusion device having the functions of the present invention has the following advantages compared to conventional nuclear fusion devices.

(1) The hydrogen isotope and helium gas in the exhaust gas mixture can be separated, and the hydrogen isotope can be returned to the fusion plasma, increasing the fuel usage efficiency of the hydrogen isotope as a fuel material. can.

(2) Since only the helium in the exhaust gas mixture needs to be exhausted and removed by the vacuum exhaust device, the exhaust capacity (load) of the vacuum pump can be reduced, and the construction cost of the device can be reduced accordingly.

(3) Since the amount of tritium, which is a radioactive substance, flowing into the vacuum evacuation equipment is reduced, operation and maintenance of the evacuation equipment is easier from a radiation control perspective.

(4) Since the amount of radioactive tritium contained in the exhaust gas discharged from the vacuum exhaust equipment is reduced, exhaust gas treatment becomes easier.

(5) Applicable not only to poloidal diverter type fusion devices, but also to all other diverter types (bundle, helical, branch, etc.) and mechanical limiter types.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the configuration of an example of the apparatus of the present invention, and FIG. 2 is an enlarged longitudinal sectional view showing a section A in FIG. 1... Blanket, 2... Heater, 3...
...Palladium alloy plate, 4...Radiation shield, 5...
...Movable slit plate, 6...Fusion plasma, 7...
... Diverter plate, 8 ... Exhaust duct, 9 ... Vacuum valve, 10 ... Vacuum exhaust device, 11 ... Vacuum container outer wall.

Claims (1)

[Scope of Claims] 1. A nuclear fusion reactor comprising core plasma and a high vacuum vessel configured of a first wall containing the core plasma, a blanket, a radiation shield and an outer wall, wherein the blanket, the radiation shield and A passageway leading to an exhaust vacuum system for fusion plasma exhaust gas consisting of hydrogen isotope gas, which is an unreacted fuel substance, and helium, which is a fusion reaction product (ash substance), is provided between the first wall and the first wall. and an opening is provided through the blanket, a palladium alloy plate having a property of transmitting hydrogen isotope gas at a specific temperature is attached to the opening, and a heating means is provided on the palladium alloy plate. A nuclear fusion device that has a hydrogen isotope/helium separation function by passing isotopic hydrogen through the palladium alloy plate and circulating it back into the core plasma. 2. The opening is configured to prevent the palladium alloy plate from being directly exposed to the fusion plasma.
2. The nuclear fusion device according to claim 1, wherein a portion of the blanket is formed to extend between the palladium alloy plate and the fusion plasma. 3. The nuclear fusion device according to item 1, wherein a movable slit plate for controlling the gas flow rate is installed upstream of the palladium alloy plate in the passage.