JPH0690294B2 - Gamma ray measuring device - Google Patents

Description

The present invention relates to a gamma ray measuring device for measuring the radiation intensity and the like of a fuel assembly used in a nuclear power plant.

[Conventional technology]

FIG. 5 shows a conventional example of this type of apparatus, which includes a collimator 1 for converging gamma rays, a detector 3 for detecting gamma rays, and a dewarwabin 4 for containing a coolant for cooling the detector.
The signal processing system (not shown) includes a storage container 5 for accommodating a detector, a wave height analyzer for analyzing the intensity of gamma rays, a computer for processing data, and the like. Gamma rays emitted from the fuel assembly 20 reach the detector 3 through the collimator 1.
The signal from the detector is subjected to pulse height discrimination by a pulse height analyzer (not shown), and the data is transferred to a computer for measurement.

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

[Problems to be solved by the invention]

As shown in FIGS. 6 and 7, the fuel assembly 20 has the fuel pins arranged in the outer layer and the inner layer, and in order to measure the inner layer fuel pin 22, the inner layer fuel discharged from the gap between the fuel pins is measured. Since it is necessary to capture the gamma ray of pin 22,
A vertical slit narrower than the gap Δl between the fuel pins is required. Therefore, the conventional device has a drawback that the gamma ray of the inner layer fuel pin 22 cannot be measured from the outer peripheral side of the fuel assembly.

The present invention enables gamma ray measurement of the inner layer fuel pin 22 from the outer peripheral side of the fuel assembly and enables visualization of a tomographic image of the fuel assembly to visually verify the distribution state of nuclides in the fuel assembly. An object is to provide a gamma ray measuring device having a function.

[Means for solving problems]

The above-mentioned drawbacks include a horizontal slit used for measuring the burnup and a collimator having a vertical slit having a width narrower than the gap between the fuel pins, and a horizontal slit used when measuring the burnup distribution of the outer layer fuel pin. The problem is solved by providing a slit selection mechanism for selectively using a longitudinal slit used when measuring the inner layer fuel pin, and a mechanism for moving the collimator in a direction perpendicular to the fuel assembly.

In the present invention, the term “longitudinal” refers to a direction that is flat in the longitudinal direction of the fuel assembly, and the term “lateral” refers to the direction orthogonal to this.

[Action]

The gamma ray measuring procedure in the present invention is similar to the conventional apparatus method for the outer layer fuel pin, and the gamma ray emitted from the fuel assembly is made incident from the collimator by using the horizontally long slit, and the signal from the detector is processed. The wave height is discriminated by the wave height analyzer, which is a component of the system, and the data is transferred to the computer to measure the burnup distribution and output distribution of the outer layer fuel pins of the fuel assembly.

In the case of measuring the inner layer fuel pin of the fuel assembly that could not be measured by the conventional device, the slit used by the slit selection mechanism mounted near the collimator is changed from horizontal slit to vertical slit and set, By operating and adjusting the mechanism that grips and rotates the fuel assembly, gamma rays from the inner layer fuel pins, which are emitted from the gaps between the outer layer fuel pins, are incident from the vertically long slits, and the burnup distribution of the inner layer fuel pins
Measure the output distribution.

On the other hand, the longitudinal slit is used, and the diameter direction of the fuel assembly is sequentially measured by the drive mechanism capable of moving the collimator. After the measurement is completed from one end to the other end in the diametrical direction, the fuel assembly is rotated by a certain angle by the mechanism for gripping and rotating the fuel assembly, and the same measurement is performed. The measurement is repeated until the fuel assembly is rotated 360 °. This has the same function as the CT (Computer Tomography) method described below. By connecting the image processing apparatus to the signal processing system in the present invention, a tomographic image of the fuel assembly can be created, and the distribution state of nuclides in the fuel assembly can be visually verified.

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

In the CT method, as shown in FIG. 8, the radiation source 23 using X-rays and gamma rays, the object 24, and the detector 25 are arranged in a straight line, and the radiation source and the detector are translated and rotated to measure the object. When the measurement data is processed by a computer and connected to an image processing device, a tomographic image of the subject can be visualized. A medical CT device using X-rays has been put into practical use, and gamma-ray measurement It is one of the features of the present invention that the apparatus has the function of CT.

FIG. 8 shows a translational motion in scanning by the CT method. X-rays or gamma rays emitted from the radiation source 23 reach the plurality of detectors 25 at an angle θ and the radiation source and the detectors move in parallel. The sampling 24 is repeated to measure the subject 24.

FIG. 9 shows the rotation operation in the scanning of the CT method, and the radiation source 23 and the detector 25 are paired and the rotation and sampling are repeated around the subject 24 to measure the subject 24.

〔Example〕

 An embodiment of the present invention will be described below.

One embodiment of the present invention is shown in FIG. The configuration of the entire device is
A collimator 1 having a plurality of horizontal slits and vertical slits (described later with reference to FIG. 3) for converging gamma rays, a collimator case 2 containing the collimator 1, a detector 3 for detecting gamma rays, and a detector 3 are cooled. A slit selection mechanism for selecting and exchanging the slits provided in the collimator 1 on the lower side of the collimator case 2 and the storage container 5 that stores the coolant 4, the detector 3, the dewar 4 and the like. The collimator support 6 is attached, the base 7 is attached to the lowermost part of the apparatus, which supports the storage container 5 and the like, and is attached with a rotating mechanism for rotating the collimator 1 in an arc shape. The electric signal from the detector 3 is connected to a wave height analyzer and a calculator of a signal processing system (not shown).

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

A swivel seat 8 that serves as a swivel center at the time of a rotating operation of rotating the collimator 1 is installed at the lower part of the storage container 5, and the storage container 5 and the like are 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 paper surface of FIG. 1), the collimator case 2, the collimator support 6, the storage container 5, etc. rotate about the swivel seat 8. When the collimator case 2 is moved to select the slit provided in the collimator 1, the collimator case 2 is moved while being supported by the roller 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 converged by a collimator, a signal is sent from the detector to a wave height analyzer, and the data obtained by discriminating the wave height is transferred to a computer. It The drive mechanism of the device is driven by a command from the sequence controller.

Next, the mechanism for selecting the slit of the collimator will be described. An outline of the slit selection mechanism is shown in FIG. Below the collimator case 2, there is provided a slit selecting mechanism including a roller 10 for moving the collimator case 2, a cylinder 11 serving as a drive 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 and the vertical slit 13 can be selected and replaced. Reference numeral 20 denotes a fuel assembly, which has a rod shape as in the conventional example (FIG. 5), is vertically supported, and can be rotated around a vertical axis.

Next, a rotation mechanism that is an example of a mechanism that moves the collimator will be described. An outline of the rotating mechanism is shown in FIG. Below the collimator support 6, a rotating mechanism including a nut holder 14 for moving the collimator support 6, a ball screw 15, a drive source motor 16 and the like is provided. A nut holder 14 is attached to the collimator support 6, and the nut holder 14 is screwed onto the ball screw 15 and can move on the ball screw 15 in the axial direction. A bracket 17 fixed on the hase 7 supports a ball screw 15, and a gear 18 is attached to the ball screw 15. A motor 16 which is 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. Driven by the motor 16, the gear 19
The ball screw 15 rotates through the nut holder 14, and the collimator support 6 attached to the nut holder 14 and the hot holder 14 screwed with the ball screw 15 is arcuately formed with the collimator case 2 around the swivel seat 8 at the bottom of the storage container 5. Rotate to. By using a pulse motor for 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, and the vertical slit 13 is used to control the fuel assembly. When measuring in the diameter direction, it is possible to measure at an arbitrary pitch and collect data.

When the present invention is carried out, the collimator support 6 (having the collimator 1 mounted) can be rotated and measured with an arbitrary constant pitch as described above, or the measurement can be performed by continuously rotating the collimator support 6 at a constant speed. You can also do it.

As described in detail above, according to the apparatus of the present embodiment, (1) by using the horizontally long slit 12 as in the conventional apparatus, the burnup distribution / output distribution regarding the outer layer fuel pin 21 of the fuel assembly is obtained. In addition to being able to measure
The use of 13 makes it possible to perform measurements on the inner layer fuel pin 22, which cannot be measured by the conventional device.

(2) By using the vertically long slits 3 to rotate the collimator 1 in an arc shape and rotate the fuel assembly 20 around the vertical axis to perform diametrical measurement on the entire circumference of the fuel assembly. Similar to the CT method, a tomographic image of each fuel pin can be created by the principle, and the distribution state of nuclides in the fuel assembly can be confirmed in detail.

(3) From the above results, detailed data of the fuel degree distribution / power distribution regarding the fuel assembly 20 can be collected, and the nuclear fuel of the fuel assembly can be effectively used by utilizing the analysis result of the data. it can.

〔The invention's effect〕

As is clear from the above examples, when the present invention is applied, gamma ray measurement of the inner layer fuel pin can be performed from the outer peripheral side of the fuel assembly, and it is possible to visualize a tomographic image of the fuel assembly. The gamma ray measuring device having a function of visually verifying the distribution state of nuclides in the fuel assembly can be constructed, which is an excellent practical effect.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the gamma ray measuring apparatus 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 in the embodiment of FIG. Fig. 4 is a schematic view of the selection mechanism section, Fig. 4 is a schematic view of the rotation mechanism section in the embodiment of Fig. 1, Fig. 5 is a cross-sectional view of a conventional gamma ray measuring device, and Fig. 6 is a view of a fuel pin in a fuel assembly. Sequence diagram, Fig. 7 is a sequence diagram when the arrangement is different from Fig. 6,
FIG. 8 is a schematic diagram showing a translational motion in scanning of the CT method, and FIG. 9 is a schematic diagram showing a rotary motion associated with FIG. 1 ... Collimator, 2 ... Collimator case, 3 ... Detector, 4 ... Dewabin, 6 ... Collimator, 7 ... Base, 8 ... Swivel seat, 12 ... Horizontal slit, 13 ... Vertical slit, 14 …… Nut holder, 15 …… Ball screw, 16
...... Motor, 20 …… Fuel assembly.

Claims (9)

[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. A gamma ray measuring device provided with means for gripping the fuel assembly and rotating it about an axis that is parallel to the length direction of the fuel assembly, wherein: (a) parallel to the length direction of the fuel assembly; Vertical slits, (b) horizontal slits perpendicular to the vertical slits, (c) drive means for switching the mutual positions so that the vertical and horizontal slits are selectively used, and (d) the slits as a fuel assembly. A gamma ray measuring apparatus comprising means for moving the body in a direction perpendicular to its longitudinal direction. 2. The movement of the slit is to move in an arc shape around the detector along a plane orthogonal to the longitudinal direction of the fuel assembly. The gamma ray measuring device according to item 1. 3. The gamma ray measuring device according to claim 1, wherein the slit is moved intermittently with a constant pitch. 4. The gamma ray measuring apparatus according to claim 1, wherein the slit is moved continuously at a constant speed. 5. The gamma ray measuring apparatus according to claim 5, wherein the rotation of the fuel assembly is intermittently rotated at fixed pitches. 6. The gamma ray measuring device according to claim 5, wherein the fuel assembly is rotated continuously at a constant speed. 7. The gamma ray measuring apparatus according to claim 1, wherein at least one of the vertical slit and the horizontal slit is provided in plural. 8. The gamma ray measuring apparatus according to claim 1, wherein the driving means for alternating the positions of the vertical and horizontal slits has a structure capable of being remotely controlled by an electric signal. 9. The drive means for moving the slit at a right angle to the longitudinal direction of the fuel assembly has a structure which can be remotely controlled by an electric signal.
The gamma ray measuring device according to the item.