KR100650325B1 - Real time neutron/gamma probe system for spent fuel verification in pond area - Google Patents

Abstract

A system for detecting high level neutron/gamma is provided to prevent damage due to a radioactive ray by separate an electronic circuit section such as a PM tube from a radioactive section. A system for detecting high level neutron/gamma includes a drive section, a detection section, and a signal processing section. The drive section includes an underwater storage bridge, a support, a motor, a motor controller, a rack gear, and a clip unit. The detection section includes a gamma optical fiber shillerization body(5-1), an optical cable, a weight, and a multi-optical tube(6-1). The signal processing section shows an ammeter and real time information for measuring current signals generated from the multi-optical tube and includes a program for controlling the system.

Description

Real time neutron / gamma probe system for spent fuel verification in pond area}

1 is a block diagram of a neutron / gamma verification system of the present invention

Figure 2 is a detailed view of the neutron / gamma detection unit and the signal processor of the present invention

Figure 3 is a picture of the detector of the present invention

4 is a diagram of the optical cable current signal according to the dose rate

5 is a diagram of the current signal of OFS according to the gamma dose rate

6 is a diagram of current signal of OFS according to neutron flux change in neutron / gamma mixed field

<Description of the symbols in the drawing>

Gamma optical fiber scintillator (5-1), neutron optical fiber scintillator (5-2), SUS tube (5-3), weight (5-4), motor controller and signal processor (6), multiple optical tube (6) -1), underwater storage tanks (9), BUNDLE (10),

The present invention relates to equipment for verifying spent fuel in an underwater reservoir and neutron / gamma measurement in a high-level radiation area that is difficult to access. The system configuration is a spent fuel verification of an underwater reservoir consisting of a motor driver, a detector and a signal processor. A neutron / gamma detection system for real time.

In general, when measuring high-level radiation, such as spent fuel verification in an underwater pool, the use of internal radiation equipment is essential, especially with high temperature and humidity.

There are various types of radiation detectors currently used for verifying spent fuel, such as gas and semiconductor types, but since the detector and the electronics are connected, a thick shield for protecting the relatively weak parts of electronics is required. It could not be used for nuclear fuel verification after using a very narrow space, and had a disadvantage that it was difficult for a user to operate due to its heavy weight. In addition, when the gamma / neutron is to be measured at the same time, two types of detectors must be used, which is bulky and expensive.

In order to solve the above problems, the present invention comprises an integrated verification equipment that can measure neutron and gamma rays simultaneously by connecting an optical fiber scintillator (OFS) and an optical cable (Passive fiber cable), about 1.5cm It provides a neutron / gamma detection system that can verify the authenticity of spent fuel from the uppermost layer to the lowest layer in the underwater reservoir by inserting a detector between the spent fuel bundles of the gaps, and also the noise signal of the optical cable generated in the high-level radiation zone. It is a technical task of the present invention to provide a system that improves the reliability of radiometric measurement at a specific point by eliminating.

In order to achieve the above object, the present invention is composed of a motor drive unit, a detection unit and a signal processing unit, the motor drive unit is a device for approaching the spent fuel to the spent fuel is mounted on the bridge of the motor and the motor controller, The radiation detector consists of an optical fiber scintillator (hereinafter referred to as "OFS"), an optical cable (hereinafter referred to as "PFC") that is responsible for the transmission of light, and a multiple that converts light into an electrical signal. It consists of an optical tube ('Photo Multiplier tube', hereinafter referred to as PMT '), and the signal processor displays a graph of ammeter and real-time gamma / neutron information for measuring the current signal generated from PMT 1, 2, and 3 The present invention relates to a neutron / gamma detection system for the verification of spent fuel consisting of a program for controlling nuclear fuel.

The present invention has constructed equipment for spent nuclear fuel validation and neutron / gamma measurements in inaccessible, high-level radiation zones. The present invention devised a device capable of verifying the authenticity of spent fuel from the uppermost layer to the lowest layer in the underwater reservoir by inserting a detection unit between spent fuel bundles of about 1.5 cm gap. In addition, unlike the existing verification equipment, the neutron / gamma detection unit is manufactured in one piece to enable easy and quick verification, and the driving unit is designed to move the detection unit safely up, down, left and right.

1 is a block diagram of a neutron / gamma verification system of the present invention. This system consists of a driver, a detector, and a signal processor.

The drive unit is a device for approaching the spent fuel to the spent fuel and consists of a support, a stepping motor and a rack gear mounted in the underwater reservoir bridge. The rack gear allows the vertical motion of the detector to be moved up and down by the stepping motor, and the support is attached to the roller to facilitate the left and right movement of the bridge.

2 is a configuration diagram of a neutron / gamma detection unit and a signal processing unit. The radiation detector consists of an optical fiber scintillator (OFS), an optical fiber (PFC) that is responsible for the transmission of light, and a PMT that converts light into an electrical signal. The signal processor consists of PMT1, 2, It consists of ammeter for measuring current signal generated from 3 and program for controlling system and showing real time information in graph.

The present invention can provide the radiation information for the point difficult to measure with the existing equipment due to the flexibility and small size of the equipment, and also the information on each radiation in the neutron / gamma mixture field using the neutron and gamma OFS It was configured to obtain.

In the case of a high-level radiation field, a signal is also generated in the PFC, which acts as a noise when trying to know the radiation intensity at a specific point, which reduces the measurement reliability. Therefore, PFC3 is horizontally connected as shown in FIG. 2 to remove a signal generated from the PFC.

By removing PMT3 from the current values of PMT1 and PMT2, the noise signal generated from PFC was removed, and only the signals generated from the gamma OFS and the neutron OFS could be selected to improve the measurement reliability.

For use in extreme environments such as spent fuel verification, neutrons with diameters of 1 mm and several mm in length and OFS for gamma are used. PFC uses flexible radiation cables with diameters of 1 mm and 15 m in length. For detection of neutrons and gamma rays, the same size OFS containing Li-7 and Li-6, respectively, is used.

In order to minimize the loss of light at the OFS and PFC contacts, optical grease is used by smoothing the cross section. In order to shield the light from the outside, OFS and PFC parts are put into black shrink tube and processed. Since some load is required to insert the detection part from the bottom to the bottom of the water, a weight weight was made using lead, and a flexible S-use tube with a diameter of 10 mm was used to prevent contamination of the detection part and to protect it from external impact. The detection part was inserted in the (SUS tube).

The outside of the SUS tube was treated with a black waterproof shrink tube to prevent contamination. 3 is a photograph of a state of the completed detection unit.

Hereinafter, the present invention will be described in detail with reference to the following Examples.

Example

The support 2 installed on the upper portion of the underwater reservoir bridge 1 located on the upper side of the underwater reservoir 8 is fixed to a position to be detected, and then the motor 4 installed on the upper side of the support is operated to operate the motor. The rack gear 8 connected to the shaft of (4) is lowered, and the detection unit composed of the optical cable and lead connected to the rack gear 8 is positioned between the spent fuel bundles stored in the underwater reservoir 9,

When gamma rays are detected by gamma optical fiber scintillator 5-1 and neutrons are detected by neutron optical fiber scintillator 5-2, two of the three multiple optical tubes 6-1 are gamma optical fiber scintillator 5-1. ) And the signals generated by being connected to the neutron fiber scintillator 5-2 are converted into electrical signals and transferred to the signal processor,

The signal processor measures current signals transferred from multiple optical tubes (PMT1, 2, 3) (6-1) with an ammeter using a program, and displays the analyzed real-time information in a graph or on a monitor and stored in the underwater storage. The neutron / gamma of the post-fuel was detected in real time.

Experimental Example 1

Figure 4 shows the results of measuring the PFC signal characteristics of 5m length according to the dose. The current signals generated in the three PFCs were matched according to the dose rate. Therefore, it was confirmed that only signals generated in the OFS can be detected by subtracting the PFC signals by subtraction.

5 and 6 show the results of experiments in the gamma captain and the neutron / gamma mixed captain.

4 is a current signal of the neutron OFS and the gamma OFS exposed to the gamma ray. It can be seen that the current values of the neutron OFS and the gamma OFS increase with the gamma dose.

Figure 5 shows the current signal according to the neutron flux change in the neutron / gamma mixture field. The neutron OFS showed a linear change with the neutron flux, while the gamma OFS remained constant. Therefore, in the neutron / gamma mixed field, information on neutrons and gamma can be obtained using the subtraction method.

Experimental results show that the OFS generates only the current signal by gamma rays and the neutron OFS generates signals by neutrons and gamma rays. Therefore, the signal by gamma rays in the neutron / gamma mixed field is the value obtained by subtracting PMT3 from PMT1, and the signal by subtracting PMT1 from PMT2 may be referred to as a current by neutrons.

The circuit was configured to supply the voltages needed for the three PMTs and to adjust the gain of the PMTs conveniently. A program using a graphical program tool was developed for signal input / output control and result processing.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1, 2, and 3, the neutron / gamma detection system of the present invention includes a driver, a detector connected to the driver and moved up and down to be detected, and installed on one side of the driver. A signal processing unit connected to the detection unit and processing a signal detected by the detection unit,

The driving unit is an underwater reservoir bridge (1) installed on the upper side of the underwater reservoir (9), a support (2) located on the upper portion of the underwater reservoir bridge (1) and provided with a moving roller (3), and the support A motor 4 installed on one side of the upper side, a rack gear 8 connected to the shaft of the motor 4 to operate up and down, and a clip device for fixing the detector to the upper portion of the rack gear 8 (not shown). Mounted on the upper rack)

1 to 3, the detection unit is fixed to the rack gear 8 of the drive unit is moved up and down by the vertical movement of the rack gear 8,

The optical fiber scintillator 5-1 for detecting gamma rays, the optical fiber scintillator 5-2 for detecting the neutrons are provided in the SUS tube 5-3, and a passive fiber cable (PFC); A weight (5-4) installed at the end of a passive fiber cable (PFC),

It is composed of a multiple optical tube (6-1) connected to the upper portion of the optical cable and the signal processing unit and converts light into an electrical signal,

The signal processing unit of the neutron / gamma detection system consisting of a program for controlling the system and displaying a current meter and real-time information for measuring the current signal generated from the multiple light tube (PMT1, 2, 3) (6-1) It is a structure.

As described above, the present invention enables non-destructive verification and real-time dosimetry of nuclear materials in places where human access is difficult and complicated in structure. Therefore, it can be usefully used for safety measures such as nuclear material verification and radiation mapping in nuclear reactor. In addition, since the electronic circuit part such as PM tube is far from the radiation area, there is no damage caused by radiation, and since only the sensor part needs to be replaced, it is cheaper and economical.

Claims (2)

In a real-time neutron / gamma detection system for verifying spent fuel of an underwater reservoir, A driving unit, a detection unit connected to the driving unit to move up and down to detect the detection unit, and a signal processing unit installed at one side of the driving unit and connected to the detection unit to process a signal detected by the detection unit, The driving unit is an underwater reservoir bridge (1) installed on the upper side of the underwater reservoir (9), a support (2) located on the upper portion of the underwater reservoir bridge (1) and provided with a moving roller (3), and the support A motor 4 and a motor controller 7 installed on one side of the upper side, a rack gear 8 connected to the shaft of the motor 4 and operated up and down, and a clip for fixing the detection unit on the top of the rack gear 8. It is a structure made of a device (mounted on the upper leggear not shown), The detection unit is fixed to the rack gear 8 of the drive unit is moved up and down by the vertical movement of the rack gear 8, The optical fiber scintillator 5-1 for detecting gamma rays, the optical fiber scintillator 5-2 for detecting the neutrons are provided in the SUS tube 5-3, and a passive fiber cable (PFC); A weight (5-4) installed at the end of a passive fiber cable (PFC), It is composed of a multiple optical tube (6-1) connected to the upper portion of the optical cable and the signal processing unit and converts light into an electrical signal, The signal processing unit is configured to include a program for controlling the system and displaying a current meter and a real-time information for measuring the current signal generated from the multiple optical tube (PMT1, 2, 3) (6-1) Neutron / gamma detection system. A real-time neutron / gamma detection method for verifying spent fuel of an underwater reservoir, The support 2 installed on the upper portion of the underwater reservoir bridge 1 located on the upper side of the underwater reservoir 9 is fixed at a position to be detected, and then the motor 4 installed on the upper side of the support is operated to operate the motor. Lowering the rack gear (8) connected to the shaft of (4), the detection unit consisting of the optical cable and lead connected to the lower end of the rack gear (8) is located between the spent fuel bundles stored in the underwater reservoir (9), When gamma rays are detected by gamma optical fiber scintillator 5-1 and neutrons are detected by neutron optical fiber scintillator 5-2, two of the three multiple optical tubes 6-1 are gamma optical fiber scintillator 5-1. ) And the signals generated by being connected to the neutron fiber scintillator 5-2 are converted into electrical signals and transferred to the signal processor, The signal processing unit measures the current signal transferred from the multiple optical tube (PMT1, 2, 3) (6-1) by using an ammeter using a program, and detects the analyzed real-time information by displaying it on a graph or on a monitor. Neutron / gamma detection method.

Images