JPS63142286A - Gamma ray measuring instrument - Google Patents

Abstract

PURPOSE:To enable the gamma rays of an inner layer fuel pin to be measured by providing a slit selecting mechanism for selectively using a collimator provided with longitudinal and transverse slits and moving the collimator in a direction perpendicular to a fuel aggregate. CONSTITUTION:A collimator 1 is provided with a transverse slit for converging gamma rays and a longitudinal slit. A slit selecting mechanism composed of a roller 10 for moving a collimator casing 2, a cylinder 11 as a driving source and the like is provided bellow the collimator casing 2. The cylinder 11 is fixed to the side surface of the cylinder casing 2 at one end and mounted to a collimator support 6 at the other end. The collimator casing 2 moves on the collimator support 6 according to the expansion or shrinkage of the cylinder 11 while being supported by the roller 10 and the transverse and longitudinal slits can be selected or exchanged. A rotating mechanism composed of a moving motor 16 for moving the collimator support 6 and the like is provided bellow the collimator support 6. Burnup distributions and the like with regard to the outer layer fuel pin and the inner layer fuel pin both of a fuel aggregate can be measured by the transverse and longitudinal slits, respectively, of above- described structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gamma ray measuring device for measuring the radiation intensity, etc. of a fuel assembly used in a nuclear power plant.

[Conventional technology]

FIG. 5 shows a conventional example of this type of device, including a collimator 1 for converging gamma rays and a detector 3 for detecting gamma rays.
4. A dewax bin containing a coolant to cool the detector. It consists of a containment vessel 5 that houses a detector, a signal processing system (not shown) that includes a pulse height analyzer that analyzes the intensity of gamma rays, a computer that processes data, and the like. The gamma rays emitted from the fuel assembly 2o pass through the collimator 1 and reach the detector 3. The signal from the detector is subjected to pulse height discrimination by a wave height analyzer (not shown), and the data is transferred to a computer for measurement. is accomplished.

The fuel assembly 20 is supported by gripping and driving means (not shown) and rotated about a vertical axis at a constant speed or intermittently at a constant pitch.

[Problem that the invention seeks to solve]

As shown in FIGS. 6 and 7, the fuel assembly 20 has fuel pins arranged in an outer layer and an inner layer, and in order to measure the inner layer fuel pins 22, the inner layer fuel discharged from the gap between the fuel pins must be measured. Since it is necessary to take in the gamma rays of the pin 22, a vertical slit narrower in width than the gap ΔQ between the fuel pins is required. For this reason, the conventional device has the disadvantage that gamma rays of the inner layer fuel pin 22 cannot be measured from the outer peripheral side of the fuel assembly.

In the invention, the inner layer fuel pin 22 is inserted from the outer peripheral side of the fuel assembly.
If it is possible to measure gamma rays in - and to visualize tomographic images of fuel assemblies, it is possible to visually verify the distribution of nuclides in fuel assemblies + and -.
ll'l device 6 [Means for solving the problem] The disadvantage of item h is that the width is narrower than the gap between the horizontal slit used for burnup measurement and the fuel pin. A collimator with a vertical slit is used to measure the burnup distribution of the outer fuel pin, and the horizontal slit and the inner fuel pin are attached at θ1.
This problem is solved by providing a slit selection mechanism for selectively using a vertical slit with a fixed special number, and a mechanism for shifting the collimator to a perpendicular force to the fuel assembly.

In the present invention, "vertical" refers to a direction parallel to the longitudinal direction of the fuel assembly, and "horizontal" refers to a direction perpendicular to this direction.

[Effect]

The method for measuring gamma rays in the present invention is to use a horizontal slit to inject gamma rays emitted from the fuel assembly through a collimator, and process the signal from the detector in the same manner as in the conventional device for the outer layer fuel pin. By distinguishing the wave height using a wave height analyzer, which is a component of the system, and transmitting the data to a computer, the burnup distribution and power distribution of the outer layer fuel pins of the fuel assembly are measured.

In the case of a total of 81g of fuel pins in the inner layer of a fuel assembly, which could not be measured with conventional equipment, the slit selection mechanism installed near the collimator can be used to switch and set the slits used from horizontally elongated slits to vertically elongated slits. By operating and adjusting the mechanism that grips and rotates the assembly, gamma rays from the inner fuel pins emitted from the gap between the outer fuel pins are incident through the vertical slit, and the burnup distribution and output distribution of the inner fuel pins are measured.

On the other hand, by using a drive mechanism that can move a collimator using a vertical slit, measurements are sequentially made in the diametrical direction of the fuel assembly. After measuring from one end to the other in the diametrical direction, rotate the fuel assembly by a certain angle using a mechanism that grips and rotates the fuel assembly, and measure in the same way. Repeat measurements until the fuel assembly has been rotated 360 degrees. This is a function similar to the CT (computer tomography) method described below.By connecting an image processing device to the signal processing system of the present invention, it is possible to create a tomographic image of the fuel assembly, It becomes possible to visually verify the distribution state of nuclides in the body.

When carrying out the present invention, the fuel assembly may be rotated intermittently at a constant pitch, or may be rotated continuously at a constant speed.

As shown in Fig. 8, in the CT method, a radiation source 23 using X-rays or gamma rays, a subject 24, and a detector 25 are arranged in a straight line, and the radiation source and detector are translated and rotated to measure the subject. When the measurement data is processed by a computer and connected to an image processing device, it becomes possible to visualize the tomographic image of the subject. Medical CT devices that use X-rays have been put into practical use, and gamma ray measurement One of the features of the present invention is that the device has a CT function.

Figure 8 shows the translational movement in scanning with the CT method.
X-rays or gamma rays emitted from the radiation source 23 form an angle θ and reach the plurality of detectors 25, and the radiation source and the detector repeat parallel movement and sampling to measure the subject 24.

Figure 9 shows the rotational movement in scanning with the CT method.
The radiation source 23 and the detector 25 form a pair and repeat rotation and sampling around the subject 24 to measure the subject 24.

〔Example〕

An embodiment of the present invention will be described below.

An embodiment of the present invention is shown in FIG. The overall configuration of the device is
A collimator 1 is provided with a plurality of horizontally long slits and vertically long slits (described later with reference to FIG. 3) for converging gamma rays, a collimator case 2 that houses the collimator 1, a detector 3 that detects gamma rays, and the detector 3 is cooled. A dewarbin 4 for storing a coolant, a storage container 5 for storing a detector 3, a dewarbin 4, etc., and a slit selection mechanism for selecting and replacing slits provided in the collimator 1 on the lower side of the collimator case 2. It is composed of a collimator case 6, which is a mounting part, and a base 7°, which is a mounting part, and a rotation mechanism that supports the storage container 5 and the like and rotates the collimator 1 in an arc shape, which is located at the lowest side of the device. The electrical signal from the detector 3 is connected to a pulse height analyzer and computer of a signal processing system (not shown).

The drive mechanism of the entire device is operated by a sequence controller in the signal processing system (see FIG. 2).

A pivot seat 8 is installed at the bottom of the containment vessel 5, and serves as a center of rotation during the rotation operation of rotating the collimator 1. The containment vessel 5, etc. is supported by rollers 9 to reduce resistance during rotation. There is.

When the collimator 1 is rotated in an arc shape (in a horizontal plane perpendicular to the plane of the paper in FIG. 1), the collimator case 2, collimator support 6, containment container 5, etc. rotate around the pivot seat 8. When the collimator case 2 is moved to select a slit provided in the collimator 1, the collimator case 2 is moved while being supported by the rollers 10 by the operation of the cylinder 11 of the drive source.

A schematic block diagram of the signal system of the device is shown in FIG.

When measuring the burnup distribution of a fuel assembly, the gamma rays are focused using a collimator, a signal is sent from a detector to a wave height analyzer, and the data that discriminates the wave height is transferred to a computer. Ru. The drive mechanisms of the device are each driven by commands from the sequence controller.

Next, the collimator slit selection mechanism will be explained. The slit selection mechanism is schematically shown in FIG. 3. A slit selection mechanism is provided below the collimator case 2 and includes a roller 10 for moving the collimator case 2, a cylinder 111 serving as a driving source, and the like. One end (cylinder bottom side) of the cylinder 11 is fixed to the side surface of the collimator case 2, and the other end is attached to the collimator support 6.

As a result, as the cylinder 11 expands and contracts, the collimator case 2 moves on the collimator support 6 while being supported by the rollers 10, and the horizontal slit 12. Vertical slits 13 can be selected and replaced. Reference numeral 20 denotes a fuel assembly, which has a rod shape similar to the conventional example (FIG. 5), is supported vertically, and can be rotated around a vertical axis.

Next, a rotation mechanism, which is an example of a mechanism for moving a collimator, will be explained. FIG. 4 shows an outline of a one-rotation mechanism. A rotation mechanism comprising a nut holder 14, a ball screw 15, a motor 161 as a driving source, etc. for moving the collimator support 6 is provided below the collimator support 6. A nut holder 14 is attached to the collimator support 6, and the nut holder 14 is screwed onto a ball screw 15 and can move on the ball screw 15 in the axial direction. A bracket 17 fixed on the base 7 supports a ball screw 15, and a gear 18 is attached to the ball screw 15. A motor 16 as a drive source for rotating the ball screw 15 is installed on the base 7, and the ball screw 15 can be rotated via a gear 19. The ball screw 15 is rotated by the drive of the motor 16 via the gear 19, and the nut holder 14 is screwed together with the ball screw 15.
The collimator support 6 attached to the nut holder 14 rotates in an arc together with the collimator case 2 around the pivot seat 8 at the bottom of the containment vessel 5.

By using a pulse motor as the drive motor 16, the amount of rotation of the ball screw 15, that is, the amount of rotational movement of the nut holder 14 and the collimator support 6, can be freely adjusted. When measuring, it is possible to measure and collect data at any pitch.

When carrying out the present invention, it is also possible to rotate the collimator support 6 (on which the collimator 1 is mounted) at an arbitrary fixed pitch as described above, and to perform measurements.

It is also possible to measure by rotating it continuously at a constant speed.

As detailed above, according to the apparatus of this embodiment, (1)
By using the horizontally long slit 12 as in the conventional device, in addition to being able to measure the burnup distribution and power distribution regarding the outer layer fuel pin 21 of the fuel assembly, the vertically long slit 1
3, it is possible to measure the inner layer fuel pin 22, which could not be measured with conventional devices.

(2) By using the vertical slit 13 to rotate the fuel assembly 20 around the vertical axis while rotating the collimator 1 in an arc shape, measuring the entire circumference of the fuel assembly in the diametrical direction. , it is possible to create a tomographic image of each fuel pin using the same principle as the CT method, and the distribution state of nuclides in the fuel assembly can be confirmed in detail.

(3) From the above results, detailed data on the burnup distribution and power distribution regarding the fuel assembly 20 can be collected, and by utilizing the data analysis results, the nuclear fuel in the fuel assembly can be used effectively.

〔Effect of the invention〕

As clarified by the above embodiments, when the present invention is applied, it is possible to measure gamma rays of the inner layer fuel pins from the outer circumferential side of the fuel assembly, and to visualize the tomographic image of the fuel assembly. This has an excellent practical effect in that it is possible to construct a gamma ray measuring device that has a function of visually verifying the distribution state of nuclides in the body.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the gamma ray measuring device according to the present invention, FIG. 2 is a block diagram of a signal processing system in the embodiment of FIG. 1, and FIG. 3 is a slit diagram in the embodiment of FIG. 1. 4 is a schematic diagram of the rotation mechanism in the embodiment shown in FIG. 1, FIG. 5 is a sectional view of the conventional gamma ray measurement device, and FIG. 6 is a diagram of the fuel pin in the fuel assembly. Arrangement diagram, Figure 7 is an arrangement diagram where the arrangement is different from Figure 6,
FIG. 8 is a schematic diagram showing the translational movement in scanning of the CT method;
FIG. 9 is a schematic diagram illustrating a rotation operation related to FIG. 8. 1... Collimator, 2... Collimator case, 3...
...Detector, 4...Duwabin, 6...Collimator, 7...Base, 8...Swivel seat, 12...Horizontal slit, 13...Vertical slit, 14...Nut holder, 15...Ball screw, 16...Motor, 2o
...Fuel assembly.

Claims (1)

[Claims] 1. A collimator provided with a slit for measuring gamma rays emitted from a rod-shaped fuel assembly, a collimator case to which the collimator is attached, and a gamma ray detector opposed to the collimator case. In a gamma ray measuring device, the gamma ray measuring device is provided with a means for gripping the fuel assembly and rotating it around an axis parallel to the longitudinal direction of the fuel assembly, wherein: (a) the length of the fuel assembly; a vertical slit parallel to the direction; (b) a horizontal slit perpendicular to the vertical slit; (c) a driving means for alternating the positions of the vertical and horizontal slits so as to selectively use them; and (d) the slit. What is claimed is: 1. A gamma ray measuring device comprising means for moving a fuel assembly in a direction perpendicular to its longitudinal direction. 2. The slit is moved in an arc shape centered around the detector along a plane perpendicular to the longitudinal direction of the fuel assembly. The gamma ray measurement device described. 3. Claim 1, wherein the slit moves intermittently at a constant pitch.
The gamma ray measurement device described in section. 4. The gamma ray measuring device according to claim 1, wherein the slit moves continuously at a constant speed. 5. The gamma ray measuring device according to claim 5, wherein the fuel assembly is rotated intermittently at a constant pitch. 6. Claim 5, wherein the fuel assembly is rotated continuously at a constant speed.
The gamma ray measurement device described in section. 7. The gamma ray measuring device according to claim 1, wherein a plurality of at least one of the vertical slits and the horizontal slits are provided. 8. The gamma ray measuring device according to claim 1, wherein the driving means for changing the positions of the vertical and horizontal slits has a structure that can be remotely controlled by electric signals. 9. The gamma ray measuring device according to claim 1, wherein the driving means for moving the slit perpendicularly to the longitudinal direction of the fuel assembly has a structure that can be remotely controlled by an electric signal.