JPS632326B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an in-reactor inspection system that can quickly detect abnormalities in a reactor core, particularly abnormalities in the loading state of fuel assemblies.

For example, in nuclear reactors such as fast breeder reactors, the nuclear fuel assemblies loaded in the reactor core are not firmly fixed in the reactor vessel in order to facilitate replacement and absorb thermal deformation, but are simply planted. It has become a state of being. For this reason, if the planting configuration shifts for some reason, a levitation force will be generated due to the pressure of the coolant.
A floating phenomenon occurs. When the nuclear fuel assembly floats in this way, the reactivity is affected. Furthermore, when moving the upper reactor mechanism from above the reactor core, there is a possibility of collision with the nuclear fuel assembly or control rods unless it is confirmed that the nuclear fuel assemblies are correctly loaded and that the control rods are completely separated.

Therefore, in order to eliminate such problems, it is necessary to detect the loading status of the nuclear fuel assembly and control rods by some means, and then reset them to their normal positions based on this. However, many coolants are opaque substances such as sodium, making them difficult to detect. Therefore, there is a demand for a nuclear reactor equipped with this type of detection system.

The present invention was made to meet these demands, and its purpose is to prevent abnormal conditions in the nuclear fuel assemblies and control rods loaded in the reactor core, or in the event that foreign objects float above the reactor core. In such a case, it is an object of the present invention to provide a highly safe nuclear reactor inspection system that can immediately detect the abnormal state and position and take appropriate measures based on this.

Conventionally, a sodium fluoroscopy device used as this type of inspection system has a transducer 1 immersed in molten sodium 2 at a high temperature of about 300°C to 600°C, as shown in Figure 1. and a drive mechanism 5 that scans the transducer and the reflector plate 4, which are installed opposite to each other so as to sandwich the reactor core 3, in a fan shape in a horizontal plane, adjusts the position and angle, and detects the position of the transducer. It is composed of a drive mechanism control section 6, a signal processing device 8, and an image display device 9. Note that the reference numeral 7 is a transmission/reception control section.

In such a configuration, ultrasonic pulses are emitted from the transducer. Ultrasonic is Core
It passes through Gap10, is reflected by a reflector, and is received by the same transducer. At this time, if a nuclear fuel assembly or control rod exists in the propagation path of the ultrasonic waves, the ultrasonic waves will be blocked and the echo level from the reflector will decrease. Therefore, it is possible to detect the magnitude of the echo signal received by the transducer, undergo appropriate signal processing, and display an image as a signal proportional to the gap.

However, the above-mentioned in-core inspection system has the following drawbacks.

Since the ultrasonic waves emitted from the transducer are reflected by a reflector and received, the inspection system becomes larger and more complex.

Therefore, the inspection system occupies a large area within the reactor vessel, making maintenance and inspection difficult. In addition, there were other problems such as high costs for manufacturing and installing the reflector.

The present invention was made to eliminate such conventional drawbacks, and an object of the present invention is to provide an in-reactor inspection system that occupies a small area and is easy to maintain.

That is, the present invention includes an ultrasonic transducer installed in a nuclear reactor, a drive mechanism that drives this transducer, and a system that controls this drive mechanism and receives signals from this drive mechanism to operate the transducer. a control unit that sends a signal indicating an ultrasound transmission/reception direction to an image processing device; a transmission/reception control unit that sends an ultrasound transmission signal to the transducer and receives an ultrasound reception signal sent from the transducer; a signal selection device that receives an ultrasonic reception signal from the transmission/reception control unit and performs addition processing on the received ultrasonic signal;
a signal processing device that receives a signal after addition processing from the signal sorting device and converts it into a signal indicating the presence or absence of an obstacle in the reactor; and an image processing device that receives signals from the signal processing device and the control section and processes the signals into images. This is an in-reactor inspection system comprising a processing device.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

In FIG. 2, the upper opening of the furnace vessel 11 is sealed by a rotating plug 12. In FIG. In the reactor vessel 11, a plurality of nuclear fuel assemblies are planted in the reactor core section 3, and the reactor upper mechanism 12 is used to operate the control rods, and the fuel is used when exchanging fuel. A switch 14 etc. are provided respectively. The reactor core section 3 is composed of a reactor core 3a and a blanket section 3b surrounding it.

Furthermore, a coolant 2 typified by liquid sodium flows into the furnace vessel 11 from an inlet 15 at the bottom of the furnace vessel 11 and flows out from an outlet 16 . On the other hand, an operating shaft 18 that can be rotated and moved in the vertical direction by the drive mechanism 5 is provided on the side of the furnace upper mechanism 12.
is suspended from the rotating plug, and its operating shaft 1
A transducer 1 is installed at 8.

As shown in FIG. 3, the transducer 1 is constructed by fixing a container 20, which is also made of stainless steel and having a thick wall, to a pipe 19 made of, for example, stainless steel. An insulating tube 21, an insulating plate 22, a metal plate 23, a spring 24, a metal plate 25, an acoustic coupling material 26, a piezoelectric element 27 formed of LiNbo ₃ , etc., and an acoustic coupling material 2
8 is housed as shown in the figure, and in this state, a stainless steel cap 29 is attached to the opening of the container 20, which has a thin wall only at the part that contacts the acoustic coupling material 28.
The metal plate 23 is electrically connected to the core wire 31 of the cable 30 inserted into the pipe 19.

Further, the drive mechanism 5 that causes the transducer 1 to scan is configured as follows. In other words, it consists of one drive source, transmission mechanism, reversible motor, reduction gear, rotation reversal mechanism, etc.
It is fixed to the upper part of the rotating plug 12 via a flange. Although not shown, a reduction gear is connected to the operating shaft 18 on which the transducer 1 is mounted, and the transducer is scanned in a horizontal fan shape at a desired speed by a reversible motor. On the other hand, the longitudinal scanning of the transducer 1 is performed by a device consisting of a reversible motor, a reversing mechanism, and a rotary linear motion conversion mechanism (for example, a pinion rack). These operations are performed by the drive mechanism control section 6, and signals representing the position and angle of the transducer 1 are input to the image processing device 9 as outputs.

In FIGS. 2 and 4, the ultrasonic waves emitted by the transducer 1 pass through the core gap 10 between the upper reactor mechanism 13 and the nuclear fuel assembly 3 to the inner wall 11a of the reactor vessel, where they are reflected. The reflected echo signal is received by the transducer again and input to the signal selection device 17. The applied echo signal has an S/
The N ratio is poor and images cannot be displayed as is.

Therefore, the signal selection device 17 described above improves the S/N and transmits the signal to the signal processing device 18. That is, the ultrasonic waves emitted by the transducer 1 are not always reflected toward the transducer 1 due to the surface condition, position, angle, etc. of the inner wall 11a of the furnace vessel. Therefore, there is a lot of noise and it is difficult to distinguish it from the real signal. Therefore, the signal selection device 17 converts the signal with S/N<1 to S/N>1 and transmits it to the signal processing device 18. In other words, the ultrasonic waves emitted by the transducer 1 are reflected by the inner wall 11a of the reactor vessel, and the echo signals are dispersed in various directions, leaving a very small amount of true signals as noise that is received by the transducer. Ru. However, since the noise signal does not always have a constant period, by adding the signals received by the transducer 1 many times, it is possible to extract the signal buried in the noise. This extraction device is called a signal selection device 17, and the extracted signal is subjected to DA conversion and outputted to a signal processing device 18. The signal input to the signal processing device 18 undergoes appropriate signal processing and is applied to the image processing device 9 as a signal proportional to the gap.

Therefore, the drive mechanism 5 and the drive mechanism control section 6
As described above, the transducer 1 is moved in the vertical direction and the horizontal sector direction, and the furnace upper mechanism 1 is moved.
3 and the fuel exchanger 14, the image processing device displays the outlines of the upper reactor mechanism, the fuel exchanger, the nuclear fuel assembly 3, etc., as shown in FIG. You can visually check the current location and whether or not it is working properly.

Since the present invention is configured as described above, the area occupied by the inspection system in the reactor vessel is small, and maintenance and
Inspection is easier, and since there is no need to manufacture or install a reflector, it is inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view schematically showing a conventional inspection system, FIG. 2 is a longitudinal sectional view schematically showing the inspection system of the present invention, FIG. 3 is a sectional view of a transducer, and FIG. 4 is a longitudinal sectional view schematically showing a conventional inspection system. A diagram showing the ultrasonic transmission/reception relationship between the user and the furnace vessel, and FIG. 5 is a diagram showing an example of image display by the image display device according to the present invention. DESCRIPTION OF SYMBOLS 1... Transducer, 3... Nuclear fuel assembly, 5... Drive mechanism, 6... Control unit, 7... Transmission/reception control unit, 9... Image processing device, 11... Reactor vessel, 12... Rotating plug, 13...Furnace upper mechanism,
14...Fuel exchange machine, 17...Signal selection device, 1
8...Signal processing device.

Claims (1)

[Claims] 1 An ultrasonic transducer installed in a nuclear reactor, a drive mechanism that drives this transducer, and a system that controls this drive mechanism and receives signals from this drive mechanism to generate ultrasonic waves from the transducer. a control unit that sends a signal indicating a reception direction to the image processing device; a transmission/reception control unit that sends an ultrasound transmission signal to the transducer and receives an ultrasound reception signal sent from the transducer; A signal selection device that receives an ultrasonic reception signal from a control unit and performs addition processing on the received signal, and a signal processing device that receives a signal after addition processing from the signal selection device and converts it into a signal indicating the presence or absence of an obstruction in the reactor. An in-reactor inspection system comprising: this signal processing device; and an image processing device that receives signals from the control section and processes the signals.