JPH0359412A - Ultrasonic transducer - Google Patents

Abstract

PURPOSE:To improve the reliability by fitting a cylindrical body on the outer peripheral surface of a metallic case where an ultrasonic vibrator is fixed and incorporating a heater and a heat insulating layer in the cylindrical body. CONSTITUTION:The high-temperature ultrasonic vibrator 3 is fixed on the bottom surface of the metallic case 1 and an electrode 4 is fitted on the top surface of the vibrator 3. The cylinder body 23 is fitted on the lower outer peripheral surface of the case 1, the heater 24 is incorporated in the cylinder body 23, and the vacuum heat insulating layer 25 is provided outside the heater 24. When this ultrasonic transducer is used as an ultrasonic fluoroscope in a fast breeder, the heater 2 is fed with electricity; to generate hear and then liquid sodium which flows in the cylinder body 23 is heated to become higher in temperature than liquid sodium at the periphery of the cylinder body 23. This high- temperature liquid sodium become easy to conform with the bottom surface 1a of the case 1 and the wettability between the case 1 and high-temperature liquid sodium comes to extremely excellent. Therefore, neither an air hole nor gap is formed between the bottom surface 1a of the case 1 and liquid sodium, so the transmission and reception of the vibrator 3 are performed speedily without any error and the response and reliability are both improved.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to the position and shape of structures in a nuclear reactor vessel filled with liquid metal, such as liquid sodium, and various equipment in the reactor. The present invention relates to an ultrasonic transducer for recognition.

(Prior Art) A conventional high-temperature ultrasonic transducer will be described with reference to FIG. That is, in FIG. 2, the opening 1a of the cylindrical stainless steel metal case 1 is covered with the cover 2.
The container is sealed and assembled by welding to form a sealed container. A disk-shaped high-temperature ultrasonic transducer 3 made of lithium niobate is disposed on the bottom inner surface of the metal case 1 . This ultrasonic transducer 3 has a Curie point of 1200°C, an electromechanical coupling coefficient Kt (Kt=y' mechanical output energy/electrical human power energy) of 0.17, a frequency of about 2.5 MHz, and a pulse width of about 50 μsec. . Reference numeral 5 denotes a silver paste which is a bonding member fired at 800° C., and the high-temperature ultrasonic vibrator 3 is bonded to the bottom inner surface of the metal case 1. 6 is a hermetic type seal connector installed through the cover 2, 7 is an electric wire covered with a silicone rubber tube, and the seal connector 6 and the high temperature ultrasonic vibrator 3 are connected.
is connected to the electrode 4 of. 8 is an M1 cable (Mineral In5ula) connected to the sealed connector 6.
ted Cable).

Conventional high-temperature ultrasonic transducers have a Curie point of 1
Since the sealed container containing the high-temperature ultrasonic transducer 3 made of lithium niobate at 200°C consists of a metal case 1 and a cover 2, the operating conditions are a temperature of 200°C to 250°C and radiation of 1. It has corrosion resistance and can be used for a long period of time even in a reactor vessel of ix IORad order. Furthermore, when a predetermined voltage is applied to the high-temperature ultrasonic transducer 3 sealed by the metal case 1 and cover 2, the frequency is 2.5 MHz and the pulse width is 50 μsec.
The ultrasonic wave is transmitted through the bottom of the metal case 1, attenuated or reflected, and sent out of the metal case 1.

An ultrasonic transducer having such a configuration is used, for example, in a sodium fluoroscope in a fast breeder reactor shown in FIG. That is, in FIG. 3, the upper end opening 10 of the reactor vessel 9 is closed with a fixed plug 11 and a rotating plug 12, and a reactor core 13 consisting of a large number of fuel assemblies and control rods is inside the reactor vessel 9. It is located. Liquid sodium coolant 15 flows through this reactor core 13 from an inlet pipe 14, removes heat, and flows out from an outlet pipe 16. Directly above the reactor core 13 is provided a core upper mechanism 17 that is placed on the rotating plug 12 and whose terminal extends above the reactor core 13 . Further, an ultrasonic fluoroscope 18 is provided passing through the fixed plug 11. This ultrasonic fluoroscope 18
The ultrasonic transducer 19 is attached to the tip of the reactor vessel 9, and a reflecting plate 20 is provided on the inner surface of the reactor vessel 9 facing the ultrasonic transducer 19. In the figure, reference numeral 21 indicates the free liquid level of liquid sodium, and 22 indicates the cover gas space.

The above-mentioned ultrasonic fluoroscope 18 observes the floating state of the handling head of the fuel assembly in order to check whether each fuel assembly in the core 13 is loaded in the correct position.

Further, when replacing a fuel assembly or the like, it is necessary to operate the rotary plug 12. In this case, if there is an obstacle between the fuel assembly and the upper core mechanism 17 that interferes with the operation of the rotating plug 12, the fuel assembly will be damaged or cracked.

The presence or absence of this obstacle is determined based on the round trip time or direction of the ultrasonic waves.

(Problems to be Solved by the Invention) If the ultrasonic transducer 19 and the liquid sodium 15 in which it is immersed have poor wettability and lack good adhesion, the above-mentioned ultrasonic fluoroscope 18 or the gap between the rotating plug 12 It goes without saying that monitoring performance will result in a decrease in performance. Therefore, in order to have good adhesion with the liquid sodium 15, it is necessary to completely wet the outer surface of the metal case 1 housing the ultrasonic transducer 3 with the liquid sodium 15.

However, the temperature of liquid sodium 15 is low at about 20
When the temperature is 0° C. or lower, it is difficult to establish complete wettability in a short period of time. In addition, high purity liquid sodium 15
Even if the ultrasonic transducer 19 is used, impurities may adhere to the surface of the metal case 1 of the ultrasonic transducer 19 or a thin gas layer may be formed. This results in insufficient wettability between the surface of the metal case 1 and the liquid sodium 15, resulting in incomplete adhesion between the two.

For this reason, the accuracy of measured values during inspection or observation will be adversely affected. Furthermore, in a fast breeder reactor, the ultrasonic fluoroscope 18 is installed before a short period of time, such as when a fuel assembly is replaced, so that the When the temperature of the liquid sodium 15 is low, impurities or an extremely thin gas layer are formed as described above. Therefore, there are problems in that the transmitted power or energy is not only absorbed by the gas layer and not propagated into the liquid sodium, but also not received.

The present invention has been made in order to solve the above-mentioned problems, and the present invention has been made in such a way that the surface of the metal case of an ultrasonic transducer can always exhibit wettability with liquid sodium in a short period of time in a normal state and maintain good adhesion. An object of the present invention is to provide an ultrasonic transducer.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an ultrasonic transducer in which an ultrasonic transducer is fixed in a sealed metal case, and which emits ultrasonic waves when a voltage is applied to the ultrasonic transducer. A heating source is provided for heating the outer surface of a portion of the metal case to which the ultrasonic transducer is fixed, and a cylindrical body surrounding the outer surface of the portion is attached to the metal case. The cylindrical body is characterized by incorporating a heater and a heat insulating layer on the outside of the heater.

(Function) A case will be described in which the ultrasonic transducer according to the present invention is loaded into liquid sodium of a fast breeder reactor and used as an ultrasonic fluoroscope. That is, the heater is heated by being immersed in liquid sodium in the reactor vessel and built into the cylinder. The temperature of the liquid sodium around the outer surface of the metal case where the ultrasonic transducer is located is maintained higher than that of the liquid sodium. Since the liquid sodium inside the cylinder is heated to a high temperature, the outer surface of the metal case is kept at a high temperature. This high-temperature liquid sodium has extremely good wettability with the outer surface of the metal case, resulting in improved wettability. Furthermore, the heat source provided inside the cylinder reduces the influence of the temperature outside the cylinder, thereby increasing the efficiency of the heat source.

By improving the wettability between the metal case and liquid sodium, the working time of the ultrasonic fluoroscope is shortened, errors in measurement values are reduced, and reliability is improved.

(Embodiment) An embodiment of the ultrasonic transducer according to the present invention will be described with reference to FIG.

In FIG. 1, a disk-shaped high-temperature ultrasonic transducer 3 made of, for example, lithium niobate is fixed to the bottom surface of a metal case 1 made of, for example, cylindrical stainless steel with a silver paste 5 interposed therebetween. An electrode 4 is attached to the upper surface of the ultrasonic transducer 3, and an electric wire 7 is connected to the electrode 4. The electric wire 7 is connected to a sealed connector 6 attached to the cover 2, and the sealed connector 6 is connected to an M1 cable 8. The interior of the metal case 1 is completely sealed by the cover 2. A cylindrical body 23 surrounds the bottom surface 1a of the metal case 1 and is connected to the lower outer peripheral surface of the metal case 1. A heater 24 is built into the cylindrical body 23, and a vacuum heat insulating layer 25 is provided outside the heater 24. Note that the cylindrical body 23. The heater 24 and the vacuum heat insulating layer 25 serve as a heat source for heating the outer surface of the bottom surface (portion a) of the metal case 1 in which the ultrasonic transducer 3 is fixed.

When an ultrasonic transducer configured in this way is used in an ultrasonic fluoroscope in a fast breeder reactor, when the ultrasonic transducer is loaded into liquid sodium, it is naturally heated to the temperature of liquid sodium; In this case, the wettability between the metal case l and liquid sodium is not good.

Therefore, by heating the heater 24 inside the cylindrical body 23, the liquid sodium that has flowed into the cylindrical body 23 is heated and becomes higher in temperature than the liquid sodium surrounding the cylindrical body 23. This high-temperature liquid sodium becomes easily compatible with the bottom surface 1a of the metal case 1, and the wettability between the metal case 2 and the high-temperature liquid sodium becomes extremely good.

Therefore, no holes or gaps are created between the bottom surface of the metal case l and the liquid sodium, so that the ultrasonic transducer 3 can transmit and receive data quickly and without error.

In the above embodiments, the case where the ultrasonic transducer is used in an ultrasonic fluoroscope has been described, but the present invention is not limited to this. Further, even if the metal case is made of cylindrical white stainless steel, the shape is not limited to the type, and the material is not similarly limited. Furthermore, the material and shape of the vacuum insulation layer do not matter as long as it can maintain a temperature difference with the liquid sodium on the outside of the cylinder, and there is no need to evacuate it.

In addition to liquid sodium, other liquid metals can also be used.

[Effects of the Invention] According to the present invention, wettability with liquid metal is improved;
The time for the ultrasonic transducer to leak with liquid metal is reduced. Therefore, when used as an ultrasonic fluoroscope, reliability is improved along with quick response, and work time for ultrasonic measurement, fuel exchange, etc. can be shortened, and operating time can be extended.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of an ultrasonic transducer according to the present invention, FIG. 2 is a vertical cross-sectional view showing a conventional ultrasonic transducer, and FIG. FIG. 2 is a schematic vertical cross-sectional view of a breeder reactor. 1... Metal case 2... Cover 3... Ultrasonic vibrator 4... Electrode 5... Silver paste 6... Seal connector 7... Electric wire 8... M1 cable 9...・Reactor vessel 10...Top opening 11...Fixed plug 12...Rotating plug 13...Reactor core 14...Inlet pipe 15...Liquid sodium 16...Outlet pipe 17...Reactor core Upper mechanism 18... Ultrasonic fluoroscope 19... Ultrasonic transducer 20... Reflection plate 21... Free liquid level of liquid sodium 22... Cover gas space 23... Cylindrical body 24... Heater 25...insulation layer (8733)

Claims (1)

[Claims] (1) In an ultrasonic transducer in which an ultrasonic transducer is fixed in a sealed metal case and which oscillates ultrasonic waves when a voltage is applied to the ultrasonic transducer, the metal to which the ultrasonic transducer is fixed A heating source for heating the outer surface of a portion of the case is provided, and a cylindrical body surrounding the outer surface of the portion is attached to the metal case, and the cylindrical body includes a heater and a heat insulating layer on the outside of the heater. An ultrasonic transducer characterized by incorporating: