JP2000111690A - Self-temperature control type uninstrumental material irradiator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an irradiating test on a large number of irradiating samples at the same temperature under a constant temperature condition by providing a self-temperature control function while being an uninstrumental type, reducing a shaft directional temperature gradient, and restraining a temperature change in the irradiating samples caused by an output change in a nuclear reactor. SOLUTION: A structure is provided with an irradiating vessel 30 having a double wall structure and having a space formed as a heat insulating gas layer 32, a heat pipe 40 having the residual part inserted inside the irradiating vessel 30 except for one end part exposed outside the irradiating vessel 30 and plural sample holders 44 dispersively arranged inside the irradiating vessel 30 by housing irradiating samples 46 to house liquid sodium 50 and inert gas in the irradiating vessel 30. The sodium in the irradiating vessel 30 is put in to a degree of completely soaking a sample holder 44. This device is normally loaded in a nuclear reactor, and a coolant of the nuclear reactor flows outside the irradiating vessel 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an irradiation container having a heat-insulating gas layer filled with a liquid, and the temperature of an irradiation sample is controlled to be substantially constant by using a heat pipe. The present invention relates to a material irradiating device that can be used. This apparatus is useful for material irradiation tests in an irradiation field having a temperature gradient or temperature fluctuation, particularly in a nuclear reactor.

[0002]

2. Description of the Related Art For the purpose of research and development of reactor materials and nuclear fuels, irradiation tests in which samples such as material test pieces are placed in a nuclear reactor and exposed to the action of radiation have been performed. This type of material irradiation test apparatus is roughly classified into a non-instrumentation type and an instrumentation type.

Conventionally, as a non-instrumented material irradiation apparatus used in a fast reactor, there is a structure as shown in FIG. 2, for example. In FIG. 2, A is a longitudinal sectional view, and B is a transverse sectional view. A plurality of cylindrical irradiation containers 12 are disposed inside a hexagonal tubular wrapper tube 10. The sample 16 is loaded in the capsule 14, a mixed gas of He (helium) / Ar (argon) is sealed, and the irradiation containers 12 are loaded in multiple stages. Although it is not clear in FIG. 2, the coolant sodium flows inside the irradiation vessel 12 in the fast reactor.

Here, the irradiation temperature of the sample 16 is adjusted by the mixing ratio of the He / Ar mixed gas sealed in the capsule 14. Since He has a higher thermal conductivity between He and Ar, the higher the ratio of Ar, the better the heat insulating effect. Therefore, when the sample temperature is set to be high, the ratio of Ar is set to be high and the sample temperature is set to be low. In this case, the ratio of He is increased. The mixture ratio of the He / Ar mixed gas is set to a predetermined value on condition that the reactor is operated at a constant power.

[0005]

As described above, the conventional non-instrumented material irradiation apparatus has no function of controlling the temperature,
Since the mixing ratio of the / Ar mixed gas is set to a predetermined value on condition that the reactor power is operated at a constant value, when the reactor power fluctuates, the sample temperature in the capsule fluctuates. For example, when the sample temperature is 700 ° C., a temperature fluctuation of about 20 ° C. occurs. In addition, since the sample temperature depends on the γ heat generated by neutrons and the coolant temperature, the central part where the neutron flux is dense and the coolant temperature is high becomes high temperature, whereas the neutron flux is sparse and the coolant temperature becomes high. In the lower position where the temperature is low, the temperature becomes low, and the temperature of the material irradiation device also changes. Such an axial temperature gradient (temperature difference) is similar when the sample temperature is about 70 degrees.
In the case of 0 ° C., it is about 30 ° C. However, if the sample temperature is low, this temperature fluctuation or temperature gradient becomes small.

On the other hand, there is an instrumentation type material irradiation apparatus. This is a method of controlling the temperature from outside the reactor vessel. Although illustration is omitted, for example, a thermocouple and a pipe for replacing a He / Ar mixed gas are inserted into a double-walled capsule, and when the reactor power fluctuates, the temperature is changed according to the temperature fluctuation in the capsule. He / A with different mixing ratio
This is a configuration in which temperature fluctuation is suppressed by substituting with an r mixed gas.

[0007] However, such an instrumentation type material irradiation apparatus is disadvantageous in that it is expensive due to its complicated structure and requires a large number of days for production. Further, there are problems that the irradiation space is limited due to the instrumentation wire routing space, and the irradiation position is limited in order to take out the instrumentation wire and the like outside the reactor vessel.

An object of the present invention is to provide a self-temperature control function in spite of being a non-instrumentation type, to reduce a temperature gradient in an axial direction, and to suppress a temperature fluctuation of an irradiation sample accompanying a fluctuation in power of a nuclear reactor. Accordingly, it is an object of the present invention to provide a material irradiation apparatus capable of performing an irradiation test on a large number of irradiation samples under the same temperature and a constant temperature condition.

[0009]

According to the present invention, there is provided an irradiation container having a double-walled structure and a heat insulating gas layer between them, and the remaining portion excluding one end exposed to the outside of the irradiation container. A heat pipe inserted into the irradiation container, and a plurality of sample holders that store the irradiation sample and are dispersed and disposed inside the irradiation container, wherein the liquid is placed in the irradiation container. This is a self-temperature-controllable non-instrumented material irradiation apparatus having a structure as described above. In the irradiation container, a liquid of the same kind as the coolant of the nuclear reactor is placed so that the sample holder is completely immersed.

The apparatus of the present invention is particularly suitable as a material irradiation apparatus for a fast reactor. In this case, a hexagonal tubular trumpet tube similar to the fuel assembly is used so that it can be handled by the refueling machine. A wrapper tube, an irradiation container shaped to be housed with a gap inside the wrapper tube and having a double-walled structure and a heat insulating gas layer between the wrapper tube, and projecting from upper and lower portions of the irradiation container, respectively Except for the attached portion to the wrapper tube and the one end exposed to the outside of the irradiation container, the remaining portion was inserted into the irradiation container, and liquid sodium and an inert gas were sealed therein. A heat pipe, and a plurality of sample holders for storing a sample for irradiation and dispersed inside the container for irradiation, wherein the container for irradiation is filled with liquid sodium and an inert gas; It is configured so that the coolant sodium flows outside the irradiation container inside the tube. Liquid sodium in the irradiation container is filled to the extent that the sample holder is completely immersed, and an inert gas such as He is sealed in the upper space.

In this case, the irradiation container also has a hexagonal cylindrical shape, and the heat pipe has the remaining portion inserted along the central axis of the irradiation container to the inner bottom except for the upper end exposed at the top of the irradiation container. It is preferable that a plurality of sample holders are equally arranged circumferentially around the heat pipe. As the heat insulating gas layer of the irradiation container, a He / Ar mixed gas is used, and the temperature of sodium in the irradiation container is adjusted by appropriately setting the mixture ratio. Then, the sodium temperature in the irradiation container is kept almost constant by the heat pipe. Thereby, the temperature gradient in the axial direction is reduced, and the temperature fluctuation of the irradiated sample due to the fluctuation of the output of the reactor is suppressed.

[0012]

FIG. 1 is an explanatory view showing one embodiment of a self-temperature control type non-instrumented material irradiation apparatus according to the present invention. In FIG. 1, A is a longitudinal sectional view, and B is a transverse sectional view. This is a material irradiation device used in a fast furnace using sodium as a coolant. A hexagonal tubular trumpet tube 20 similar to a normal fuel assembly is used. An entrance nozzle 24 is provided at a lower portion of the wrapper tube main body 22, and a handling head 26 is attached at an upper portion thereof so that a fuel exchanger can be loaded into a furnace vessel (not shown) of the fast reactor.
Has a structure in which sodium coolant flows as shown by the arrow.

The irradiation container 30 is accommodated in the wrapper tube 20. The irradiation container 30 has the same hexagonal tubular shape as the trumpet tube 20 and has a slightly smaller cross section, and thus has a gap between the trumpet tube 20 and the coolant sodium. The irradiation container 30 has a double wall structure on the side surface and a heat insulating gas layer 32 between the sides, and is filled with a He / Ar mixed gas having an appropriate mixing ratio. Further, a lower mounting portion 34 is provided at a lower portion of the irradiation container 30 so that a tip projects downward in a rod shape and fits into a hole of the support plate 25 above the entrance nozzle 24. The support plate 2 projecting upward and below the handling head 26
An upper mounting portion 36 that fits into the hole 7 is provided. The lower mounting portion 34 has a solid structure, while the upper mounting portion 36 has a frame structure and is provided with holes on the side surface and the upper surface, so that the coolant sodium can freely flow through those holes. .

A heat pipe 40 is inserted from above along the inner central axis of the irradiation container 30. That is, the irradiation container 3
Except for the upper end exposed to the outside, the remaining part is assembled so that the lower end reaches the inner bottom of the irradiation container 30. The heat pipe 40 has liquid sodium 42 and an inert gas (for example, Ar) sealed therein. A plurality of (in this case, six) sample holders 44 are arranged circumferentially so as to surround the heat pipe 40 inside the irradiation container 30.
Is arranged. Each sample holder 44 has an airtight structure and stores a sample (material test piece) 46 therein. Here, a state in which a plurality of samples 46 are stacked in the vertical direction is shown,
Actually, since the irradiation amount differs at the vertical position, a member for fixing the position is provided according to the test conditions and the like, and each sample is fixed at a predetermined axial position. Then, the inside of the irradiation container 30 is filled with liquid sodium and an inert gas. The amount of liquid sodium 50 depends on each sample holder 44
Is completely immersed, and the upper space 52 is filled with an inert gas (for example, He).

In this material irradiation apparatus, since the irradiation container 30 is filled with sodium having good thermal conductivity and fluidity, the internal temperature becomes uniform. Further, since the side surface of the irradiation container 30 is surrounded by the heat-insulating gas layer 32 of the He / Ar mixed gas, the temperature fluctuation due to the fluctuation of the reactor power is suppressed. Furthermore, when the sodium temperature in the irradiation container 30 rises, the sodium in the heat pipe 40 evaporates, and the latent heat of the heat pipe 40 at the center suppresses the temperature rise of sodium in the irradiation container 30. . The sodium evaporated inside the heat pipe 40 moves upward, and is cooled and condensed by the coolant sodium flowing through the inside of the trumpet tube 20. The liquid sodium moves below the heat pipe 40. In this way, the temperature gradient in the axial direction inside the irradiation container 30 is also reduced.

Here, the sodium temperature inside the irradiation container 30 is set as follows. The evaporation temperature of sodium in the heat pipe 40 is set to Ar
Adjust with the gas filling pressure. The temperature of sodium in the irradiation container 30 depends on the heat insulating gas layer 3.
It is adjusted by the mixing ratio of He / Ar mixed gas of 2. As described above, since He has a higher thermal conductivity between He and Ar, the larger the ratio of Ar, the greater the heat insulating effect. Therefore, the ratio of Ar is increased in high-temperature irradiation, and He is increased in low-temperature irradiation.
Increase the ratio.

The device of the present invention can also be applied in principle to an irradiation test in a light water reactor or the like. However, in that case, the efficiency is not very high because the thermal conductivity is much smaller than that of sodium. Therefore, the present invention is a technique that is particularly useful for a material irradiation test in a nuclear reactor using liquid metal as a coolant.

[0018]

As described above, the material irradiation apparatus according to the present invention has a structure in which a liquid is placed in a double-walled irradiation container having a heat insulating gas layer and a heat pipe is inserted, so that the heat insulating property and the internal The temperature of each sample arranged in the axial direction and the radial direction is made uniform by the liquid circulation, heat conduction, and the self-temperature control function by the heat pipe, so that irradiation tests of many samples can be performed at the same temperature.

Since the material irradiation apparatus of the present invention does not require an instrumentation facility, the loading position on the nuclear reactor is not limited, and irradiation can be performed at an arbitrary position.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a self-temperature control type non-instrumented material irradiation apparatus according to the present invention.

FIG. 2 is an explanatory view showing an example of a conventional non-instrumented material irradiation apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 Wrapper tube 30 Irradiation container 32 Thermal insulation gas layer 34 Lower mounting part 36 Upper mounting part 40 Heat pipe 44 Sample holder 46 Sample 50 Sodium

Claims (3)

[Claims] 1. An irradiation container having a double-walled structure and a heat insulating gas layer therebetween, and the remaining portion excluding one end exposed to the outside of the irradiation container is inserted into the irradiation container. A self-temperature-controllable heat pipe, comprising: a heat pipe; and a plurality of sample holders, each containing a sample for irradiation and dispersed and disposed inside the container for irradiation, wherein a liquid is contained in the container for irradiation. Instrumentation material irradiation device. 2. A hexagonal tubular wrapper tube, an irradiation container having a double-walled structure and a heat insulating gas layer formed between the wrapper tubes and having a gap therebetween, Except for an attachment part to the trumpet pipe protruding from the upper part and the lower part of the container, respectively, and the other part excluding one end exposed to the outside of the irradiation container, the remaining part is inserted into the irradiation container, and liquid sodium is contained therein. And a heat pipe filled with an inert gas, and a plurality of sample holders containing a sample for irradiation and dispersed and disposed inside the container for irradiation, wherein the irradiation container contains liquid sodium and A self-temperature-controllable non-instrumented material irradiation apparatus filled with an inert gas and in which sodium coolant flows outside the irradiation container inside the wrapper tube. 3. The irradiation container also has a hexagonal cylindrical shape, the heat-insulating gas layer is filled with a mixed gas of He / Ar, and the heat pipe has the remaining portion excluding the upper end exposed at the upper part of the irradiation container. 3. The self-temperature-controlled non-instrumented material according to claim 2, wherein the sample holder is inserted to the inner bottom along the central axis of the irradiation container, and the plurality of sample holders are evenly arranged circumferentially around the heat pipe. Irradiation device.