JPH0738037B2 - Temperature control type material irradiation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material irradiation apparatus used for testing the effects of irradiation on core materials.

[0002]

This temperature control type material irradiation device irradiates a sample of core material such as a cladding tube with radiation at a constant temperature,
It is used to measure the characteristic change of the sample due to radiation irradiation, and is arranged between the fuel assemblies in the reactor core filled with liquid sodium.

When the irradiated sample is irradiated with radiation, the temperature of the irradiated sample rises and the temperature of the irradiated sample rises, but it is required from the test that irradiation is performed while the temperature of the irradiated sample is kept at a predetermined value. . In order to meet such requirements, the above-mentioned conventional technology uses a device composed of an inner tube and an outer tube as described in the pamphlet PNC TN2530 90-001 of the Power Reactor and Nuclear Fuel Development Corporation. . The irradiated sample is held in the inner tube and immersed in sodium. Sodium flows into the inner tube from the core through a sodium inflow tube provided on the end surface of the inner tube, and irradiates the irradiation sample and the inner tube with a kind of gamma ray of radiation. The heat generated there is transferred to the inner tube by sodium. A gas gap is provided between the inner cylindrical pipe and the outer cylindrical pipe, and the gas is cooled by filling and replacing the gas with the cooling temperature control gas inflow / outflow pipes provided at the end surface of the outer cylindrical pipe. The cooling temperature control gas is a mixture of helium gas with good thermal conductivity and argon gas with poor thermal conductivity, set to a mixing ratio that matches the core output at that time, and the heat from the inner tube to the outer tube is set. Control the transfer to keep the temperature of the irradiated sample constant.

The inner tube temperature is constantly monitored, and the above-mentioned mixing ratio of the mixed gas is set by the temperature control system according to the temperature change caused by the fluctuation of the core output, etc., and the gas mixing tank is installed separately. The mixed gas is manufactured and filled, the gas is sent from the gas inflow pipe to the gas gap, and the existing gas is flowed out from the gas outflow pipe to be replaced.

[0005]

In the above-mentioned prior art, in order to replace the gas in the gas gap after detecting the change in the temperature in the inner cylinder being monitored, it takes about 10 minutes to prepare the mixed gas and replace the gas. Therefore, the temperature control inevitably has a time delay with respect to the temperature change in the inner cylinder pipe due to the core output fluctuation and the like over a long period of time.

Further, since the temperature is controlled by substituting the mixed gas, the temperature to be controlled has a stepwise shape, so that the temperature of the sample has a stepwise shape, and the mixed gas is set with high accuracy by the control system. If the temperature is not controlled, the temperature inside the inner tube fluctuates up and down around the target temperature and vibration occurs. Therefore, it is necessary to control the temperature so that the target temperature can be continuously and quickly obtained.

Particularly, the irradiation temperature of the irradiated sample has a great influence on the test result of the irradiated material and is a very important factor in the test. Therefore, the irradiation material providing side requires an irradiation temperature with a minimum change, and a stepwise temperature change is not preferable.

It is an object of the present invention to prevent the temperature change of an irradiated sample caused by fluctuations in core power, etc. without replacing the cooling temperature control gas, and to keep the temperature of the irradiated sample constant. It is to provide a device.

[0009]

In order to achieve the above object, an inner cylindrical tube having both ends closed to accommodate an irradiation sample and an outer cylindrical tube having both ends closed to accommodate the inner cylindrical tube concentrically A temperature provided with a sodium inflow pipe connected to one end surface of the inner cylindrical pipe and a sodium outflow pipe connected to the other end surface, and a gas supply pipe and an outflow pipe connected to the outer cylindrical pipe. In the control type material irradiation device, the temperature control type material irradiation device is characterized in that the inner cylindrical tube is formed of a material having a larger thermal expansion coefficient than the outer cylindrical tube.

[0010]

With this structure, the above-mentioned object can be achieved by the present invention by the following operations. In the temperature control type material irradiation device, the temperature of the outer tube hardly changes because it is constantly cooled by sodium flowing through the core. However, the member temperature inside the inner tube is cooled from the outside of the outer tube through the gas gap between the outer tube and the inner tube, so it depends on the heat transfer coefficient of the gas gap and is proportional to the core power fluctuation. Fluctuate.

If a material having a coefficient of thermal expansion larger than that of the outer tube is used for the material of the inner tube for holding the irradiated sample, when the output of the reactor core is increased, the heat generated by gamma rays of sodium flowing into the inner tube is generated. Increases, the temperature of the inner tube rises, and the gas gap shrinks accordingly, improving the cooling effect.
Conversely, when the output decreases and the inner tube temperature decreases, the gas gap widens and the cooling effect decreases. In this way, the cooling of the inner tube is controlled, and since it acts so as to cancel the temperature fluctuation of the irradiated sample due to the core power fluctuation, the purpose is achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, the structure of the temperature control type material irradiation device has an inner cylinder composed of an inner cylinder tube 6 holding an irradiation sample 7, an inner cylinder tube end plug 8, a sodium inflow tube 3 and a sodium outflow tube 9. Tube part and outer cylinder tube 4 for holding the cooling temperature control gas 2
And a gas inflow pipe 1, a gas outflow pipe 10, and an outer cylinder pipe end plug 11, which is an outer cylinder portion.

The operation of cooling control by the gas gap 5 will be described. Irradiated sample 7 is sodium 12 in the inner tube.
And is held by the inner tube 6 and the inner tube end plug 8. The sodium 12 flows into the inner cylinder through the sodium inflow pipe 3 and transfers the heat generated by the gamma rays of the irradiation sample 7 and the inner cylinder 6 to the inner cylinder 6.

Since the radiation generated by the core fluctuates in proportion to the fluctuation range of the power output of the reactor core, the amount of gamma heat generated by gamma rays generated in the members of the temperature control type material irradiation apparatus is proportional to the fluctuation amount of the core output. Fluctuate. Since the outer tube 4 of the material irradiation apparatus is constantly cooled by sodium flowing through the core, the temperature change is small enough to be considered to be almost unchanged. However, since the member inside the inner tube 6 is cooled from the outside through the gas gap 5, its temperature fluctuates according to the heat transfer coefficient of the gas gap 5 and the fluctuation of the core output.

Therefore, when a material having a large coefficient of thermal expansion is used for the inner tube 6, the temperature of the inner tube 6 decreases when the gamma heat in the inner tube decreases due to a decrease in core output, and the temperature of the inner tube 6 is proportional to the coefficient of thermal expansion. The diameter shrinks. Since the outer tube 4 is made of a material having a small temperature drop and a small coefficient of thermal expansion, it contracts less than the inner tube 6. As a result, the width of the gas gap 5 increases when the output decreases. As a result, the heat transfer from the inner cylinder tube 6 to the outer cylinder tube 4 deteriorates, and the cooling effect decreases, so that the temperature in the inner cylinder including the inner cylinder tube 6 rises.

On the contrary, when the core output is increased, the radiation of the core is increased, the heat generated by the gamma rays of the members inside the inner tube 6 is increased, and the temperature is increased. Due to this temperature rise, the diameter of the inner cylindrical tube 6 increases due to thermal expansion. Since the outer tube 4 has a low temperature rise and is made of a material having a small coefficient of thermal expansion, the degree of increase is smaller than the diameter of the inner tube 6. This reduces the width of the gas gap 5 when the output increases. As a result, the heat transfer from the inner cylinder pipe 6 to the outer cylinder pipe 4 side is improved, and the cooling effect is increased, so that the temperature in the inner cylinder including the inner cylinder pipe 6 is lowered.

When this embodiment is installed in the reactor core, the output fluctuation of the reactor core is 5%, and
Due to the variation of the radiation dose proportional to this variation, the gamma ray calorific value of the members of the inner cylinder part, that is, the inner cylinder tube 6, the inner cylinder tube end plug 8, the irradiated sample 7, etc., fluctuates and the temperature also fluctuates. The width of the gas gap 5 is controlled by using a material having a coefficient of thermal expansion larger than that of the outer tube 4 due to this temperature fluctuation. For example, by adopting austenitic stainless steel for the inner tubular tube 6 and ferritic stainless steel for the outer tubular tube 4, it is possible to set a difference of about 30% in the coefficient of thermal expansion between the two.

In a normal operating condition, the temperature of the sodium in contact with the outer tube 4 is about 450 degrees, and the temperature of the irradiated sample 7 is about 650 to 700 degrees. The temperature rise of the irradiated sample 7 is about 10 degrees with respect to the 5% power rise of the core. On the other hand, when the gas gap 5 of the present embodiment is 1 mm, the reduction of the gas gap 5 is about 2%, and the heat transfer coefficient is improved by about 2%. As a result, the temperature of the irradiated sample 7 is not lowered. It will be about 8 degrees. In this way, the irradiation sample 7
The temperature rise of the irradiation sample 7 is suppressed and the temperature of the irradiated sample 7 is kept almost constant.

When the gas gap 5 is 0.5 mm, the effect is greater than in the above case, and the temperature rise of the irradiated sample 7 can be suppressed to about 1 degree.

On the other hand, the gas gap 5 expands when the core power decreases. The amount of expansion is the same as the amount of contraction when the output increases,
Therefore, the temperature drop of the irradiated sample 7 can be suppressed to the above-mentioned level.

The temperature control described above is continuous and extremely smooth because the width of the gas gap 5 is contracted / expanded almost at the same time as the core output is increased / decreased. In this case, we considered the case where austenitic stainless steel was used as the material of the inner tube 6 and ferritic stainless steel was used as the material of the outer tube 4, but if a material with a larger difference in thermal expansion coefficient is used, the temperature control effect will be improved. Becomes noticeable.

Further, since the temperature control system including the gas mixing tank is indispensable for the equipment for producing the mixed gas, the entire equipment becomes large-scale, and it is difficult to secure the installation place inside the reactor. . Although the equipment is large and complicated, the possibility of failure increases, but since this equipment is installed inside the core, it is impossible to repair it at any time. According to this embodiment, these large-scale facilities are unnecessary.

[0024]

According to the present invention, since the inner tube is made of a material having a coefficient of thermal expansion larger than that of the outer tube, the gas gap between the inner tube and the outer tube changes according to the temperature of the inner tube. However, the heat transfer coefficient between them changes. As a result, the cooling effect of the inner cylindrical tube changes so as to cancel the temperature change of the inner cylindrical tube, so that there is an effect of keeping the temperature of the irradiated sample substantially constant.

Further, since a large-scale mixed gas production facility is not required, there is an effect that the place where the production facility is installed can be saved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 1 Gas Inflow Pipe 2 Cooling Temperature Control Gas 3 Sodium Inflow Pipe 4 Outer Tube 5 Gas Gap 6 Inner Tube 7 Irradiated Sample 8 Inner Tube End Plug 9 Sodium Outflow Tube 10 Gas Outflow Tube 11 Outer Tube End Plug 12 Sodium

Claims (1)

[Claims] 1. An inner cylindrical tube having both ends closed to accommodate an irradiation sample, an outer cylindrical tube having both ends closed to accommodate the inner cylindrical tube concentrically, and an inner cylindrical tube connected to one end surface of the inner cylindrical tube. In the temperature control type material irradiation device, the inner tube is provided with a sodium inflow tube and a sodium outflow tube connected to the other end surface, and a gas supply tube and an outflow tube connected to the outer tube. The temperature control type material irradiation device is characterized in that the outer tube is made of a material having a coefficient of thermal expansion larger than that of the outer tube.