JPS5979898A - Method of detecting failed fuel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a method for detecting damaged fuel, in which contamination of the sampling system is reliably removed within the conventional inspection time, and a decrease in the accuracy of detecting damaged fuel due to contamination is prevented. This paper relates to a method for detecting damaged fuel.

[Prior art]

A large number of fuel assemblies are arranged in the core of a boiling water reactor, and if the fuel rods that make up the fuel assemblies break,
The radioactive materials flowing out from the fuel rod breakage end up contaminating the reactor plant equipment and layout, such as the reactor pressure vessel surrounding the reactor core, coolant purification equipment, and steam turbines. In order to prevent contamination caused by such damaged fuel assemblies, the integrity of fuel assemblies is regularly inspected. If a damaged fuel assembly is discovered, immediately
Replaced with a healthy fuel assembly.

FIG. 1 shows the configuration of the damaged fuel detection device, and FIG. 2 shows the operating process. A conventional method for detecting damaged fuel will be explained using FIG. 1, FIG. 2, and FIG. Attaching the zipper cap to the fuel assembly 1 placed in the coolant and cleaning the sample line and sample pump are carried out in parallel. The purpose of this cleaning is to remove radioactive substances that adhered to the sample line and sample pump during the previous sampling of the fuel assembly 1 by supplying pure water. After loading the shisoper camp 63, pressurized air is supplied into the 7-amper camp 63 to isolate it from the surrounding coolant. Air supply continues until sampling is complete. After isolation by air supply, high temperature pure water flows into the fuel assembly 1. If there is a damaged fuel rod in the fuel assembly 1, radioactive materials will be released from the damaged part into the coolant in the fuel assembly 1, so leave it alone for a certain period of time.

This process is called soaking. After waiting for the completion of noking, the sample pump 33 is driven, and the flushing water (cell water) accumulated in the sample pipe 31 is discharged from the discharge port 37 of the sample line. After the cell water has been removed, a sample water receiver 35 is provided at the sample line discharge port 37, and a predetermined amount of the upper coolant of the fuel assembly 1 is collected. Thereafter, the radioactivity level in the sample water receiver 35 is measured, and the health of the fuel assembly 1 is determined by comparing it with the levels of other fuel assemblies. Once the sampling is completed, a seven-tube camp 63 is installed on another fuel assembly, and the operations described above are repeated.

In such conventional damaged fuel detection methods, after sampling the coolant of the damaged fuel detection device, highly radioactive materials are deposited on the sampling system. For this reason,
The radioactivity level of fuel assembly sampling water in subsequent inspections will be affected by this attached radioactive material, and the accuracy of determining the health of the fuel assembly based on the radioactivity level will be significantly reduced. Furthermore, since all of these fuel assemblies must be re-inspected, it takes a long time to detect damage to the fuel assemblies.

[Purpose of the invention]

The present invention is i? It is an object of the present invention to eliminate the drawbacks of the prior art described above, to prevent a decrease in detection accuracy of damaged fuel assemblies, and to shorten the time required for inspection.

[Summary of the Invention] A feature of the present invention is to utilize hot water injected into the fuel assembly and pass the hot water through the sampling water sampling system, thereby promoting the removal effect of residual radioactive materials by highly radioactive sampling water. However, it is possible to prevent a decrease in detection accuracy due to residual radioactive substances and an extension of inspection time due to re-examination.

[Embodiments of the invention]

An embodiment of the present invention will be described based on FIG.

The damaged fuel detection device also includes a shisoper camp 63, an air supply device 46, a sampling device 36, a cleaning water supply device 17, and a hot water injection device 28.

The structure of the non-bar camp is shown in Figures 4 and 5.

The non-permanent camp 63 has an outer camp 64 and an inner cap 65.

Four inner camps 65 are arranged within an outer cap 64 having a square cross section. The four water sampling pipes 68 are connected to the water sampling pipe attachment port 6 provided at the top of the outer cap 64.
6 and inserted into the inner camp 65. An air supply port 69 is provided through the earthen wall of the outer camp 64. Furthermore, a nozzle 70 is attached to the upper surface of the outer cap 64. Plate-shaped guides on the sides and inside of Inner Camp 65” 7
275E is installed. A notch 73 is formed in the lower jaw of the outer camp 14.

The air supply device fjii 46 has air 9 (4 metal tubes 4
5. Air supply source 41, stop valve 42, pressure reducing valve 4
3. A solenoid valve 44 is installed in the air supply pipe 45.

Sampling device 36 includes a water sampling tube 68 attached to outer cap 64. Sanfon 1 long piping 31
is connected to each water sampling pipe 68. A solenoid valve 32, a sample pump 33, a flow rate adjustment valve 34, and a solenoid valve 3B are attached to the sampling pipe 31 from the 7-horn cap 63 side to this l1jl. The discharge port 37 is the sampling pipe 3
It is formed in the first gasp.

The wash water supply pipe 16 of the wash water supply device 17 is connected to the sampling pipe 31 between the solenoid valve 32 and the sample pump 330. A stop valve 12, a pressure reducing valve 13, a solenoid valve 14, and a flow rate adjustment valve 15 are installed in the wash water supply device.

The hot water injection pipe 25 of the hot water injection device 28 is connected to the sampling pipe 31 between the solenoid valve 32 and the water sampling pipe 68. Solenoid valve 21, hot water tank 22, heater 29, brewer 23,
A hot water injection pump 24, a solenoid valve 26, and a flow rate adjustment valve 27 are provided in the hot water injection device 28.

A sample pump hot water flushing auxiliary pipe 81 is installed between the flow rate adjustment valve 34 and the solenoid valve 38 and between the water sampling pipe attachment port 66 and the connection point 3o. A solenoid valve 82 is provided in the sample pump hot water flushing auxiliary piping 81.

The operation of the damaged fuel detection device will be explained based on FIG.

First, a Shisopar cap mounting operation 51 is performed. Grip the handle 7o of the shisoper camp 63 with the grip part 8o of the fuel exchange device installed in the reactor building,
A shisoper cap 6 is placed on the top of the fuel assembly 1 to be inspected.
3 and seat the 7 outer = IF Yap 64 on the upper grid 3.

At this time, the four-legged inner camp 65 is attached to the upper end of each channel box 2 of the four fuel assemblies 1.

Parallel to the seven-member cap loading operation 51, a sample line flanning operation 52 and a sample pump flushing operation 91 are performed. The electromagnetic valves 14, 32, and 38 are opened, and clean wash water is supplied through the wash water supply pipe 16 to wash the inside of the sampling pipe 31 and sample pump 33. After the specified period of time has elapsed, the solenoid valve 14.38
Close and stop the supply of washing water. After completing the sample line infrastructure 7'7'7''r production 52, the thinner cap 63 is seated on the upper grid 3.

・/When the collar cap layering operation 51 is completed, the solenoid valve 44 is opened and pressurized air from the air supply source 41 is supplied to the air supply pipe 45.
into the outer gap 64. When the coolant liquid level in the thinner cap 63 is pushed down from the upper end of the channel box 2 by pressurized air, the flow of the coolant is stopped and the four fuel assemblies 1 are isolated from each other.

Illusion operation 54 (ri sampling operation 58
It can be continued until it is finished.

After confirming that air bubbles are coming out from the notch of the outer cap 64 and confirming that isolation is properly performed, the solenoid valve 26 is opened and the hot water injection pump 24 is driven to pump the hot water in the hot water tank 22. The hot water is injected into the fuel assembly 1 via the hot water injection pipe 25 and the water sampling pipe 68 of the shisoper cap 63. At this time, the solenoid valve 82 is simultaneously opened to supply hot water to the sample pump 33 so that the hot water is sent to the fuel assembly 1 through the sample pump hot water 7 lancing auxiliary pipe 81. After injecting the prescribed hot water, the solenoid valve 26,
82 is closed and the hot water injection pump 24 is stopped.

After the hot water injection operation 55 is completed, the four fuel assemblies 1 are left isolated for a certain period of time to perform soaking. Due to natural convection within the fuel assembly 1 during the soaking operation 56, radioactive material emitted from the breach moves to the upper part of the fuel assembly 1 if a damaged fuel rod is present.

After the noking operation is completed, the sample pump 33 is driven, and the pure hot water accumulated in the sampling pipe 31 is discharged from the discharge port 37. Furthermore, by driving the sample pump 33, the coolant in the fuel assembly 1 is sucked through the water sampling pipe 68. After carrying out this cell water removal operation 57 for a certain period of time and completely releasing the pure hot water in the sampling pipe 31,
A sample water receiver 35 is installed under the discharge port 37, and after collecting a certain amount of sample water to collect the cooling inside the fuel assembly 1 discharged from the discharge port 37, the electromagnetic device 32 and 38 are closed and the sample pump 33 is turned on. Stop ζ. This completes the sampling operation 58. When the sampling operation 58 is completed, the solenoid valve 44 is closed and the isolation operation 54 is completed.

The radioactivity level of the cooling water in the sample water receiver 35 is measured to determine whether a damaged fuel rod exists in the fuel assembly 1. This radioactivity analysis is carried out in 7 Sopa-1 camp installation operations 5.
Since this can be carried out in parallel with the first series of operations, immediately after the sampling operation 58 is completed, the series of operations starting with the cap mounting operation 51 is repeated for the next fuel assembly 1. Note that opening and closing of the line separation valve in a series of operations can be easily performed using push buttons or the like using a control panel3.Furthermore, the series of operations can also be automated by using a timer.

According to this embodiment, the hot water to be injected into the fuel assembly can be injected through a system where radioactive substances tend to remain, thereby promoting the removal effect of radioactive substances remaining in the sampling system, especially the sample pump. can be done. Therefore, the accuracy of the health evaluation of the fuel assembly based on the radioactivity level of the coolant in the fuel assembly 1 can be prevented from being degraded due to radioactive substances adhering to the nangling system. Further, since the re-operation f1r of the fuel assembly 1 associated with this can be avoided, the fuel inspection time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional damaged fuel detection device, FIG. 2 is a work process diagram of a damaged fuel detection method, and FIG. 3 is a system diagram of a damaged fuel detection device that is a preferred embodiment of the present invention. FIG. 4 is a view of the upper lattice seating of the Shisopar cap, and FIG. 5 is a plan view of the Shisopar cap. 1...Fuel assembly, 2...Channel box, 3
...Upper grid, 17...Washing water supply device, 28...
・Hot water injection device K, 33...Sample pump, 36...
・Sampling device, 46...Air supply device, 63・
... Cyrano<-gap, 81...Sample pump hot water flushing auxiliary piping. Figure 4 Figure 5

Claims (1)

[Claims] 1. While cleaning the inside of the sampling tube by supplying a cleaning flow into the sampling tube, attach the 7-horned camp to the top of the fuel assembly installed in the coolant in the reactor, and place it inside the Shiranoku-cap. Pressurized air is introduced to stop the flow of the coolant rising within the fuel assembly, isolating the fuel assembly from surrounding coolant, and discharging pure water, which has a higher temperature than the coolant, into the fuel assembly. In a method for determining the health of the fuel by injecting the coolant into the fuel assembly and then holding it for a certain period of time, the upper coolant in the fuel assembly is sampled through the sampling pipe, and the radioactivity of the sampled water is measured to determine the health of the fuel. This method of detecting damaged fuel is characterized by injecting hot water into the fuel assembly via the system.