JP2003075597A - Nuclear spallation neutron source facility and target vessel for nuclear spallation neutron source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nuclear spallation neutron source target capable of being cooled with a simple structure. SOLUTION: A partitioning plate 7 is bonded within a target to partition the connecting pipe 3 and connecting pipe 4 of a target vessel 2, and the proton beam incident-side tip part of the partitioning plate 7 is opened to constitute an inlet-side passage 5 and an outlet-side passage 6. A proton beam is incident on a proton beam incident surface 1 shifted from the central axis 24 of the target vessel 2 to the outlet-side passage 6. A stagnation preventive hole 8 is provided on the partitioning plate 7, and a guide blade 9 equipped with an inlet narrowing plate 10 is further provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a spallation neutron source facility and a spallation neutron source target adopted in the facility.

[0002]

2. Description of the Related Art A neutron generator that irradiates a heavy metal target with a high-energy proton beam to generate high-density neutrons by a spallation reaction can generate most neutrons with respect to incident energy. The equipment is simpler than that of a nuclear reactor. Therefore, for the purpose of using neutrons in various fields such as life sciences, materials / materials research, nuclear physics, and medicine, MW is used worldwide in Europe, the United States, and Japan.
Construction of a neutron source facility with high output up to the class is planned.

As an existing neutron source facility utilizing the spallation reaction, I of Rutherford Appleton Research Institute in England is available.
There are SIS (160 kW), LANSCE (56 kW) from Los Alamos National Laboratory in the United States, and KENS (2.5 kW) from Japan High Energy Accelerator Research Organization.

In any of the neutron source facilities, solid heavy metals such as tantalum and tungsten are used as target materials, and cooling water is made to flow through the gap between a plurality of target thin plates arranged to cool the target. As an example,
JP-A-11-238598 is cited.

However, in the next-generation MW class neutron source facility, the heat generation density of the target material increases as the output power increases, and it becomes difficult to cool the solid heavy metal target.
Therefore, in the high power neutron source facility, it is planned to use a liquid metal that can also serve as a heat medium as a new target material. As one example thereof, Japanese Patent Laid-Open No. 11-22
4798 and Japanese Patent Laid-Open No. 2000-162400 are listed.

[0006]

When liquid metal, which can also be used as a heat medium, is used as a target material, the temperature of the liquid metal increases due to heat generated by the spallation reaction of the liquid metal. Then, the corrosion of the structural material by the liquid metal is accelerated. Further, since the target container, particularly the proton beam incident surface thereof, has a high heat generation density, if sufficient heat cannot be removed, the target container may be damaged by excessive thermal stress.

Therefore, it is necessary to make the temperature of the liquid metal in the target container uniform, suppress the local temperature rise, and improve the cooling property of the proton beam incident surface. Further, since irradiation damage to the container material due to protons and neutrons is severe, it is necessary to keep the structural integrity by simplifying the target structure and minimizing the welding line.

At the high-power neutron source facility currently planned, mercury is assumed as the liquid metal, and a target structure that can solve the above problems is under study. The target structures that have been proposed so far are
It can be roughly classified into a return flow type as disclosed in JP-A-11-224798 and a cross flow type as disclosed in JP-A-2000-162400.

The return flow type has a structure proposed in the SNS plan in the United States and the ESS plan in Europe. After the mercury is once flowed to the tip of the target container from both sides of the proton beam irradiation area, the vicinity of the proton beam incident surface is determined. The flow is reversed by and the mercury is made to flow downstream in parallel with the incident direction of the proton beam. Therefore, mercury does not require complicated control because it only flows toward the outlet of the target container while being irradiated with a proton beam, and the internal structure is very simple.

However, stagnation is likely to occur at the confluence reversal portion of the flow near the proton beam incident surface, and it is difficult to remove heat from the proton beam incident surface. For this reason, in the SNS plan, the cooling performance is planned to be ensured by flowing mercury for cooling the proton beam incident surface into the gap formed by the double structure with the target container as a double structure. Becomes complicated, such as doubled.

On the other hand, the cross flow type has a structure proposed in the neutron source facility of the Japan High Intensity Proton Accelerator Project, in which mercury is made to flow so as to be orthogonal to the incident direction of the proton beam. Therefore, since mercury flows along the proton beam incident surface, the proton beam incident surface has good cooling performance, but in the proton beam irradiation area, it is necessary to distribute the flow rate of mercury according to the heat generation density distribution, which is realized. Therefore, the internal structure becomes complicated.

An object of the present invention is to realize a simple structure for suppressing damage to a target container for a spallation neutron source, improving heat removal performance of a proton beam incident surface, and reducing the maximum temperature by homogenizing the temperature of liquid metal. Especially.

[0013]

In order to achieve the above object, a neutron that irradiates a liquid metal with a high-energy proton beam to generate high-density neutrons by a spallation reaction and uses the liquid metal as a heat medium. In the source liquid metal target, a target container for irradiating a proton beam, an inlet side flow passage and an outlet side flow passage for circulating the liquid metal from the outside to the target container are provided, and the outlet side flow passage of the target container is extended. It is characterized by irradiating a proton beam on the line.

More preferably, a partition plate that divides the inside of the target container into an inlet-side flow path and an outlet-side flow path is provided, and the tip of the partition plate on the proton beam incident side is opened so as to be a liquid metal flow path. However, it is characterized in that the exit side flow path is irradiated with a proton beam.

More preferably, a guide vane is provided at the tip of the partition plate on the proton beam incident side.

More preferably, the partition plate is provided with a stagnation preventing hole as an opening.

More preferably, the flow path inside the target container is provided with a rectifying plate.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The overall structure of a spallation neutron source facility is shown in FIG. In FIG. 14, a moderator 26 is installed adjacent to the target container 2, and both are surrounded by a reflector 28. The target container 2, moderator 26, and reflector 28 are housed inside the target vessel 32. The area around the target vessel 32 is covered with a thick shield 29 made of iron or concrete. Further, a proton beam line 23 used as a means for guiding the proton beam generated by the high-intensity proton accelerator to the target container 2 side, and a neutron beam line for guiding the neutrons generated at the target container 2 to the neutron utilization experimental apparatus 31 side. Three
0 penetrates the shield 29.

The high-energy proton p ⁺ accelerated to the GeV order by the accelerator enters the target container 2 through the proton beam line 23. In the target container 2, a large amount of high-energy neutrons are generated by the spallation reaction of a liquid metal (target material) such as mercury by the high-energy proton p ⁺ . At this time, the nuclear reaction causes high density heat generation between the target container 2 and the target material, so that the target cooling system 25 circulates and cools the liquid metal as the target material.

The high-energy neutrons generated are reflected by the reflector 2.
8 effectively collects them in the moderator 26 and decelerates them to the energy level required for the study in which neutrons are desired. Since the moderator 26 also generates heat when neutrons enter, it is used while being circulated and cooled by the moderator cooling system 27. The decelerated low-energy neutrons are transported to the neutron utilization experimental apparatus 31 through the neutron beam line 30.

Secondary radiation such as protons, neutrons, and γ rays is generated from the inside of the target container 2, so that the target vessel 32 is covered with a thick shield 29 to shield the secondary radiation. To prevent radiation exposure.

As the researches that want to use neutrons, various research objects such as material structure research for the development of superconducting materials and next-generation magnetic recording elements, life science research such as elucidation of protein function and drug development are conducted. Therefore, a spallation neutron source facility is needed for future innovative research.

A first embodiment of the target container 2 used in the spallation neutron source facility will be described below with reference to FIGS. 1 to 6. 1 is a top view of the target container 2, FIG. 2 is a side view of the target container 2, FIG. 3 is a BB cross-sectional view taken along the central axis 24 of the target container 2 of FIG. 2, and FIG. 4 is the target container of FIG. 2 is a sectional view taken along the line A-A along the central axis 24, FIG. 5 is a view taken along the line CC of FIG. 2, and FIG. 6 is a view taken along the line D-D of FIG.

A target pipe 2 for irradiating a proton beam is connected with a connecting pipe 3 and a connecting pipe 4 for circulating a liquid metal from the outside, and the respective pipes 3, 4 are flanges 13, 14, 15 respectively. , 16 are connected to the inlet pipe 11 and the outlet pipe 12 of the target cooling system 25.

Mercury, that is, liquid metal, flowing from the inlet pipe 11 into the target container 2 through the connecting pipe 3 is irradiated with the high-energy proton beam guided by the proton beam line 23 in the target container 2, and a large amount of it is irradiated. Neutrons are generated and nuclear heat is generated, and then the neutrons are discharged from the connecting pipe 4 and circulate in a closed loop that returns to the target cooling system 25 through the outlet pipe 12.

A partition plate 7 is provided inside the target container 2 so as to partition the liquid metal inflow portion of the connection pipe 3 and the outflow portion of the connection pipe 4. A folded flow path is created by opening the end of the partition plate 7 on the proton beam incident side. The folded back flow path is a semi-circular flow path that connects the inlet side flow path 5 and the outlet side flow path 6 divided by the partition plate 7. The liquid metal that has flowed into the target container 2 from the connecting pipe 3 passes through the inlet-side flow path 5 and has a folded flow path.
After flowing to the tip part of the, the flow direction is changed along the proton beam incident surface 1 by a folded flow path to enter the exit side flow path 6, and in parallel with the incident direction of the proton beam into the target container 2. And flows to the downstream side, that is, the connecting pipe 4.

The proton beam is applied to the outlet side flow passage 6 from the proton beam incident surface 1 at a position displaced from the central axis 24 of the target container 2 to the outlet side flow passage 6 side. The smooth flow of the liquid metal near the proton beam entrance surface 1 can improve the cooling performance of the proton beam entrance surface 1, and the liquid metal flows more parallel to the proton beam entrance direction as compared with the conventional case. It is possible to achieve uniform mercury temperature with a simple internal structure of the target container 2 without adopting an internal structure for distributing the flow rate.

A guide vane 9 is provided at the tip of the partition plate 7 on the proton beam incident side, and the liquid metal flowing through the inlet side flow path 5 is gently changed in direction to be separated from the liquid metal flow. It has a structure that does not easily occur.

Further, the partition plate 7 is provided with a stagnation preventing hole 8 and the liquid metal in the inlet side flow path 5 flows out from the stagnation preventing hole 8 so that the flow metal is likely to be generated at the turnaround reversal portion. It is possible to suppress the circulating flow and prevent the formation of local hot spots.

Further, an inlet diaphragm plate 10 is provided at the tip of the guide blade 9, and by controlling the flow rate of the liquid metal flowing into the guide blade 9, the stagnation of the liquid metal in the guide blade 9 is prevented. Then, even if a shake occurs in the incident direction of the proton beam, a high temperature portion does not occur.

The liquid metal makes a U-turn in the target container 2 and flows out into the outlet pipe 12 via the connecting pipe 4. The liquid metal that flows out becomes a high temperature and serves as a coolant for cooling the target container 2. The function of is degraded. In order to improve the function, the liquid metal discharged from the target container 2 into the outlet pipe 12 and having a high temperature is cooled by the target cooling system 25.

The target cooling system 25 has a system configuration in which a liquid metal circulates between the heat exchanger 19 and the inside of the target container 2 as shown in FIG. That is, the high-temperature liquid metal discharged from the target container 2 enters the surge tank 17 through the outlet pipe 12, and is driven by the pump 18 from inside the surge tank 17 to move inside the heat transfer tube inside the heat exchanger 19. It passes through and exchanges heat with the coolant (secondary cooling water) outside the heat transfer tube in the heat exchanger 19. The liquid metal deprived of heat by the heat exchange due to the heat exchange is cooled and the heat is passed from the heat exchanger 19 to the inlet pipe 1
It is used as a coolant and a target material that passes through the inside of the target container 1 and enters the inlet side flow path in the target container 2 to cool the target container 2 again.

On the other hand, the secondary cooling water is supplied from the secondary cooling water inlet 20 to the heat exchanger 19, and the secondary cooling water heated by removing heat from the liquid metal here is the secondary cooling water outlet. The heat discharged from 21 is sent to a cooling tower (not shown) or the like, and the heat taken away is finally released into the atmosphere.

In this way, the liquid metal that has generated heat due to the spallation reaction is circulated and reused while being cooled by the target cooling system 25 outside the target container 2. Also,
An inert gas such as helium is enclosed as a pressurized gas in the upper space of the surge tank 17, and the pressure inside the cooling system is increased by pressurizing the inside of the cooling system with the pressure of this gas. The liquid metal pressure of is kept constant.

FIGS. 8 to 12 show another embodiment of the target container 2 for the spallation neutron source used in the spallation neutron source facility of FIG. 14, and the difference from the first embodiment is the target container. Since it is only the internal structure of
Only the figure corresponding to the -B section is shown. Therefore, the other structure is basically the same as that of the first embodiment, and the configuration shown in FIG. 7 can be applied to the liquid metal target cooling system 25.

FIG. 8 shows a second embodiment of the target container 2 for the spallation neutron source. In the first embodiment shown in FIG. 3, the guide vane 9 and the inlet diaphragm plate 10 at the tip of the partition plate 7 are removed, and the inner structure is the simplest. In the case of this structure, after the liquid metal is inverted from the inlet side flow path 5 to the outlet side flow path 6 at the tip of the partition plate 107, a separation region or a circulating flow is likely to occur in the vicinity of the partition plate 107 of the outlet side flow path 6. However, when the flow velocity of the liquid metal is low or when the distance between the irradiation region of the proton beam and the partition plate 107 can be sufficiently secured, the target container 2 according to the second embodiment as described above.
However, the soundness of the target container 2 can be ensured without causing hot spots locally.

FIG. 9 shows a third embodiment of the target container for the spallation neutron source. In the third embodiment, the partition plate 107 in the second embodiment is thickened as shown in FIG.
A curved surface was formed at the tip of the proton beam entrance side of 107. In the third embodiment using such a partition plate 207, it is possible to suppress the peeling of the liquid metal and the generation of the circulation flow with a simpler structure than the first embodiment, and to prevent the generation of hot spots. The soundness of 2 can be secured.

FIG. 10 shows a fourth embodiment of the target container 2 for the spallation neutron source. In the fourth embodiment, a stagnation prevention hole 308 is formed in the tip of the partition plate 207 in the third embodiment.
The partition plate 307 provided with is used, and the circulation flow can be further suppressed by causing the liquid metal of the inlet-side flow path 5 to flow out from the stagnation prevention hole 308 to the opposite side. Therefore, the occurrence of hot spots can be further suppressed, and the soundness of the target container 2 can be further ensured.

FIG. 11 shows a fifth embodiment of the target container 2 for the spallation neutron source. The fifth embodiment is a partition plate 4 in which the inside of the partition plate 207 in the third embodiment is hollow.
And the partition plate 407 of the outlet side flow path 6
The separation of the flow of the liquid metal and the generation of the circulation flow which are likely to occur in the vicinity can be smoothly suppressed by the curved surface of the end of the partition plate 407, and the vibration of the proton beam and the spallation reaction 2 The nuclear heat generation of the partition plate itself due to the secondary particles can be reduced by the hollow structure. That is, when the partition plate 407 has a hollow structure, the mass that reacts with the protons is smaller than that of the solid structure, and the amount of heat generated by the reaction is smaller accordingly. Therefore, the temperature rise of the partition plate 407 can be further suppressed.

12 and 13 show a sixth embodiment of the target container 2 for the spallation neutron source. In the sixth embodiment, the rectifying plate 22 is formed along the central axis 24 of the target container 2 in the extension direction of the partition plate 207 at the end portion of the partition plate 207 of the third embodiment shown in FIG. A plate is provided and the flow of the liquid metal is controlled by the straightening plate 22.

FIG. 13 is a view showing a cross section taken along the line AA of FIG. 12, in which a large number of holes are formed in the current plate 22, and the distribution of the opening area of the current plate 22 by these holes is changed so that the liquid metal is formed. Flow, that is, the flow velocity distribution is finely adjusted, and the proton beam incident surface 1
It is possible to effectively carry out the cooling and uniforming of the temperature rise of the liquid metal.

For example, the opening area of the hole of the straightening plate 22 near the left end side of the partition plate 507 of FIGS. 12 and 13 is small,
In comparison with this, the opening area of the holes of the flow regulating plate 22 near the left end side of the target container 2 is increased to slow the flow velocity of the liquid metal near the left end side of the partition plate 507, and to reduce the liquid near the inner wall surface of the target container 2. Increase the flow velocity of metal.

When the flow velocity of the liquid metal is distributed in this manner, a gentle flow is formed near the left end side of the partition plate 507, and a separation flow or a circulation flow is unlikely to occur, and it is fast along the inner wall surface of the target container 2. As a result, the cooling effect of the liquid metal on the wall surface of the target container is improved. Therefore, the proton beam incident surface 1 can be cooled efficiently.

In order to avoid nuclear heat generation and irradiation damage of the rectifying plate 22, the rectifying plate 22 is preferably installed on the upstream side of the proton beam incident surface 1. The current plate 22 can be applied to the structure of the target container 2 shown in all of the above embodiments.

In any of the embodiments, the incident surface of the proton beam radiated toward the target container 2 to the target container 2, that is, the proton beam incident surface 1 is a flow path on the outlet side of the central axis 24 of the target container 2. It is set to shift in the direction of 6. Therefore, when the target container 2 of each example is adopted and used in a spallation neutron source facility, the proton beam irradiated toward the target container 2 is the target container 2.
Although it is parallel to the central axis 24 of the above, it is incident on the proton beam incident surface 1 which is deviated from the central axis 24 in the direction of the outlet side flow path 6.

As described above, in any of the embodiments, the target container for irradiating the proton beam, the inlet side flow passage for flowing the liquid metal from the outside to the target container and the outlet side flow passage are provided, and the target container By irradiating the proton beam off the central axis, the cooling properties of the proton beam incident surface and the liquid metal were improved, and the spallation neutron source facility with excellent structural soundness and the structural soundness used for the facility were excellent. A target container can be realized.

Further, a partition plate which divides the inside of the target container into an inlet side flow passage and an outlet side flow passage is provided, and the tip of the partition plate on the proton beam incident side is opened so as to form a liquid metal flow passage. In the example of irradiating the exit side channel with a proton beam, the simple structure is used to improve the cooling property of the proton beam entrance surface and the liquid metal, and the spallation neutron source facility and its facility with excellent structural soundness. It is possible to realize a target container having excellent structural soundness used for.

Further, in the example in which the guide vanes are provided at the tip of the partition plate on the proton beam incident side, the separation of the flow of the liquid metal and the generation of the circulating flow in the outlet side flow passage are suppressed to prevent the generation of hot spots. As a result, the cooling property of the liquid metal can be improved, and a spallation neutron source facility having excellent structural soundness and a target container having excellent structural soundness used in the facility can be realized.

In the example in which the partition plate is provided with the stagnation prevention hole, the liquid metal is caused to flow from the inlet side flow passage to the vicinity of the partition plate of the outlet side flow passage, thereby suppressing the generation of a circulating flow and generating a hot spot. It is possible to realize a spallation neutron source facility having excellent structural soundness and a target container having excellent structural soundness, which is used for the facility, by preventing the above, improving the cooling property of the liquid metal.

Further, in the example in which the flow straightening plate is provided in the channel inside the target container, the flowability of the liquid metal in the outlet side channel is controlled to improve the cooling property of the proton beam incident surface and the liquid metal, It is possible to realize a spallation neutron source facility having excellent structural soundness and a target container having excellent structural soundness used in the facility.

[0051]

As described above, according to the target container for the spallation neutron source of the present invention, the soundness of the target container can be easily ensured with a simple structure. Moreover, if the spallation neutron source facility of the present invention is approached, the soundness of the target container constituting the facility can be easily ensured with a simple configuration, so the reliability of the facility is improved.

[Brief description of drawings]

FIG. 1 is a top view of a target container for a spallation neutron source according to a first embodiment of the present invention.

FIG. 2 is a side view of the target container for the spallation neutron source of FIG.

3 is a sectional view taken along line BB of FIG.

FIG. 4 is a sectional view taken along line AA of FIG.

FIG. 5 is a view on arrow CC of FIG.

FIG. 6 is a view on arrow DD of FIG.

FIG. 7 is a system diagram of a target cooling system of a spallation neutron source facility according to the present invention.

FIG. 8 is a view of a target container for a spallation neutron source according to a second embodiment of the present invention, taken along the line BB in FIG.

FIG. 9 is a view of a target container for a spallation neutron source according to a third embodiment of the present invention, corresponding to the BB cross section of FIG. 2;

FIG. 10 is a view of a target container for a spallation neutron source according to a fourth embodiment of the present invention, taken along the line BB in FIG.

FIG. 11 is a view of a target container for a spallation neutron source according to a fifth embodiment of the present invention, corresponding to the BB cross section of FIG. 2;

FIG. 12 is a view of a target container for a spallation neutron source according to a sixth embodiment of the present invention, taken along the line BB in FIG.

13 is a sectional view taken along line AA of FIG.

FIG. 14 is an overall view of a spallation neutron source facility according to the present invention.

[Explanation of symbols]

1 ... Proton beam incident surface, 2 ... Target container, 3, 4 ...
Connection pipe, 5 ... Inlet side flow passage, 6 ... Outlet side flow passage, 7, 10
7, 207, 307, 407, 507 ... Partition plates, 8, 3
08 ... stagnation prevention hole, 9 ... guide blade, 10 ... entrance diaphragm plate,
11 ... Inlet piping, 12 ... Outlet piping, 13, 14, 15,
16 ... Flange, 17 ... Surge tank, 18 ... Circulation pump, 19 ... Heat exchanger, 20 ... Secondary cooling water inlet, 21 ... 2
Next cooling water outlet, 22 ... Straightening plate, 23 ... Proton beam line, 24 ... Central axis of target container, 25 ... Target cooling system, 26 ... Moderator, 27 ... Moderator cooling system, 28 ... Reflector, 29 ... Shield Body, 30 ... Neutron beam line, 31
… Neutron experiment equipment, 32… Target vessel, p
⁺ … Proton, n… neutron.

Claims (11)

[Claims] 1. A cross-flow type target container in which a liquid metal flows back from an inlet side flow passage to an outlet side flow passage,
Guide means for guiding a proton beam to the target container, means for guiding neutrons emitted from the liquid metal in the target container hit by the proton beam to neutron utilizing means, and cooling the liquid metal to the target A nuclear spallation neutron source facility, which is provided with a means for circulating it to a container, and in which an incident position of the proton beam guided by the guiding means to the target container is set on an extension line of the outlet side flow path. 2. The spallation neutron source facility according to claim 1, wherein a partition plate is provided at a boundary between the inlet side flow passage and the outlet side flow passage. 3. The spallation neutron source facility according to claim 2, wherein the partition plate on the side where the liquid metal flow is turned back is equipped with a curved surface that smoothly guides the turning flow. 4. The spallation neutron source facility according to claim 2 or 3, wherein the partition plate is provided with a hole for passing the liquid metal near the inlet side channel of the target container to the channel near the outlet side channel. 5. The spallation neutron source facility according to claim 2, 3 or 4, wherein a flow straightening plate is provided in the middle of the flow path where the flow of the liquid metal is turned back. 6. An inlet side flow passage, an outlet side flow passage, and a flow passage which is folded back between the both flow passages are provided inside the container, and a plane of incidence of a proton beam is set on an extension line of the outlet side flow passage. Target container for spallation neutron source. 7. The target container for spallation neutron source according to claim 6, wherein a partition plate is provided at a boundary between the inlet side flow passage and the outlet side flow passage. 8. The target container for a spallation neutron source according to claim 7, wherein the partition plate on the side where the flow of the liquid metal is turned back is equipped with a curved surface for smoothly guiding the turning flow. 9. The target for spallation neutron source according to claim 7 or 8, wherein a partition plate is provided with a hole for passing the liquid metal near the inlet side channel of the target container to the channel near the outlet side channel. container. 10. The target container for spallation neutron source according to claim 7, 8 or 9, wherein a rectifying plate is arranged in the middle of the flow path where the flow of the liquid metal is turned back. 11. A spallation neutron source target in which a liquid metal is circulated in the target container according to any one of claims 6 to 10.