JPS6147590A - Detector for damaged 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] [Technical field of invention] The present invention relates to a 1!1 fuel detection device.

[Technical direction 51 of the invention and its problems] Conventionally, in order to detect fuel damage, a method has been used in which rare gas is continuously measured by gross measurement using an off-gas monitor disposed at the outlet of an air extractor.

However, since this method involves cross measurement of rare gases, there is a problem in that fuel damage cannot be reliably detected due to interference from nitrogen 13 and the like.

Another method is to manually analyze iodine in water and detect fuel damage, but this method increases the amount of work and radiation exposure for workers due to the manual analysis.
Furthermore, during reactor operation, the water concentration in reactor water does not change as quickly as in rare gases, so there is a problem in that it is very difficult to determine the presence or absence of a nuclear reactor from changes in the reactor water concentration.

Furthermore, in-core shipping is carried out to investigate the location of damaged fuel, but since this in-core shipping targets all the fuel assemblies arranged in the reactor core, the number of samples reaches several hundred. As a result, there are situations where workers have to work all night for more than a week, and there is a problem in that the amount of work and the radiation exposure ω of the workers increases significantly.

Therefore, there has been a demand for a damaged fuel detection device that can not only detect damage to a fuel tank at an early stage but also be able to estimate the location of the damaged fuel.

[Object of the invention] The present invention has been made in response to such conventional circumstances,
It is an object of the present invention to provide a damaged burnout detection device that can detect fuel damage at an early stage and estimate the position of the damaged fuel.

[Summary of the Invention] The present invention provides an off-gas monitor device that measures the amount of rare gas nuclides contained in the off-gas upstream of the rare gas hold-up device, and an off-gas monitor device that measures the amount of rare gas nuclides contained in the off-gas that has passed through the rare gas hold-up device. inputting a hold-up outlet monitor that measures the amount of krypton-85 that is produced, m of rare gas nuclides measured by the off-gas monitoring device, and the amount of krypton-850 measured by the hold-up outlet monitor;
This damaged fuel detection device is characterized by comprising a burnup calculation device that calculates the burnup of the damaged fuel from the relationship between these quantities.

[Embodiment of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 shows an embodiment of the damaged fuel detection device of the present invention. In the figure, reference numeral 11 indicates a rare gas contained in the off-gas upstream of the rare gas hold-up equipment @ 12 located at the nuclear power plant. It shows an off-gas monitor device that measures the ridge line. A hold-up outlet monitor 13 is disposed downstream of the rare gas hold-up device 12 to measure the amount of krypton 85 contained in the off-gas that has passed through the rare gas hold-up device 12.

In the figure, reference numeral 14 inputs the rare gas nuclide QJ5 measured by the off-gas monitor 11 and the krypton 85 measured by the hold-up exit monitor 13, and calculates the burnup of the damaged fuel from the relationship between these values. The figure shows a burnup calculation device.

In the above-described configuration, the off-gas monitoring device 11 may be used, for example, as described in Japanese Patent Application No.
The off-gas monitoring device disclosed in No. 033606 is used.

However, this off-gas monitoring device is not shown in Figure 2.
In the figure, sample air is introduced from a sampling conduit 1 connected to the off-gas main piping.The sampling tank is connected to the downstream side of a valve 2a installed in this sampling conduit 1 via a valve 2b. 3 is connected, and a dilution tank 4 is also connected through a valve 2C.A detection section 5 equipped with a Ge detector is connected through valves 2d and 2c.

These 1 numbering tank 3, dilution tank 4, and detection unit 5 are provided with piping 6a, 6b for exhausting the inside thereof.
6C is connected. In the figure, the symbols 2r, 2
G, 2h, and 2i are valves installed in each pipe. The pipes 6a, 6b, and 6C are connected to a vacuum pump 7, and the opening and closing operations of the various valves described above evacuate the pulling tank 3, the detection cell 5, the inside of the detection section J3, and the inside of the pipes connected thereto.

A Na I detector 8 is arranged in the sampling tank 3 to detect the rare gas level. When the rare gas level in the sample air is high, the sample air in the sampling tank 3 is transferred to the dilution tank 4. is introduced and diluted. Valves 2f and 2g on the downstream side of sampling tank 3
A dilution gas supply pipe 9 is connected to the pipe between the sampling tank 3 and the dilution tank 4 through a valve 2j. dilute the sample air.

In the figure, a sampling tank 3' and a dilution tank 4' are similarly connected to the sampling conduit 1 via valves 2b'2c', and are designated by reference numeral 6a'.
, 5b' are pipes connected to the sampling tank 3' and dilution tank 4', respectively; 2r', 2g' and 2n' are valves connected to these pipes; and 9' is the valve connected to these pipes.
indicates a dilution gas supply pipe connected via valve 2j'.

Next, the operation of the apparatus having the above configuration will be explained.

First, valves 2d, 2e, 2f, 2f', 2g, 29',
Listen to 2h, 2h', 21, turn all remaining valves 111, and open sampling tank 3.3' and dilution tank 4.4'.
The inside of the detector 5 is evacuated by the vacuum pump 7. Mumbling tank 3.3', dilution tank 4.4'J3
J: After the inside of the detection unit 5 is in a vacuum state, the valves 2d and 2e
, 2f, 2f', 2g, 2g', 2h, 2h', 21
Close the valves 2a, 2b, 2b' and pump air from the off-gas main pipe into the ψsibling tank 3.
．． 1. Close the sampling valve and measure the rare gas level of the sample air in the sampling tank 3 using the Na I detector 8. If the rare gas level is below the specified value, Sample air is introduced into the detection section 5 by opening and closing the valves 2b, 2d, and 2C, and radioactive rare gas nuclides are measured and detected by the Ge detector. Then, measure again after 10 minutes.

This Ge detector is connected to a pulse height analyzer J3 (not shown) and a computer, which analyze the data detected by the G13 detector to identify and quantify radioactive noble gas nuclides and analyze the release model. This computer also controls the opening and closing operations of various valves, and can automatically perform everything from collecting the sample air mentioned above to analyzing the rare gas release model. After the measurement, the valves 2d, 2e, and 21 are opened and the inside of the detection unit 5 is evacuated by the vacuum pump 7, and then these valves are closed again.

One hour after measuring the sample air in the sampling tank 3, the valves 2b', 2d, and 20 are opened to introduce the sample air in the sampling tank 3' into the detection part 5. To measure radioactive noble gases in the long-lived group of orders. After the measurement, the valve is opened and closed in the same way, and the inside of the detection part 5 is evacuated by the vacuum pump 7.
Valves 2f, 2f', 2g, and 2g' are also used to exhaust the inside of the sampling tank 3.3'.

If the Na I detector 8 confirms that the nuclear fuel cladding tube has been damaged and the rare gas level in the off-gas has exceeded a predetermined value, the sample air in the sampling tank 3 automatically collected as described above is introduced into the dilution tank 4 by opening valve 2b12c, and then by opening valve 21'
, 2j are opened and dilution gas is introduced from the dilution gas supply pipe 9 until the inside of the dilution tank 4 reaches normal pressure, thereby diluting the sample air to a measurable level.

Next, the above-mentioned valves are closed, and the sample air in the dilution tank 4 is introduced into the detection section 5 by opening and closing operations of the valves 2c, 2d, and 2e, and the radioactive rare gas is measured, and the measurement is performed again 10 minutes later. After the measurement, the detection section 5 is evacuated by the vacuum pump 7, and the sample air in the sampling tank 3' is also introduced into the dilution tank 4' and diluted with dilution gas.

One hour after measuring the sample air in the dilution tank 4, the diluted sample air in the dilution tank 4' is introduced into the detection section 5 by opening and closing the valves 2c', 2d, and 2e.
Measure radioactive noble gases in the long-lived group. After measurement,
Valves of each pipe 2f, 2f', 2g, 20', 2h
, 2h', 2i and valve 2d.

Sampling tank 3 by vacuum pump 7 after listening to 2C
．． 3', the sample air in the tank 4.4' and the detection unit 5 is exhausted.

According to the off-gas monitoring device 11 configured in this way, even when the nuclear fuel cladding tube is damaged ('+6) and the rare gas level rises, it is diluted to an appropriate level and automatically analyzes the rare gas nuclide in the off-gas. It is also possible to analyze the radiation model and the release model, thereby saving labor for management and reducing the radiation exposure dose of workers.

This J:Una off-gas monitoring device 11 makes it possible to detect fuel damage at an early stage.

On the other hand, the hold-up outlet monitor 13 (in X, the off-gas that passed through the rare gas hold-up device 12 is
It has been determined that the amount of krypton 85 contained in
It is output to 4.

The burnup calculation device 14 calculates the residence time of krypton 85 from the time when the damage is detected by the off-gas monitor device 11 to the outlet of the rare gas 71ζ-led up device 12,
This: Calculate the quantitative value of the peak amount of 1 knob ton 85 detected by the 7 tall up output monitor 13 within the full opening time, and determine the fixed value of the rare gas nuclide when combustion occurs. The burnup is calculated by dividing by the above-mentioned constant value of the peak of krypton 85.

In other words, generally, several types of fuel assemblies with different fuel cycles are arranged in the core of a boiling water reactor.
Old fuel rods have a large amount of krypton-85 accumulated in these fuel assemblies. When the fuel is damaged, the krypton-85 accumulated in the fuel rods will leak out at once, but the value of the amount of rare gas nuclides divided by the amount of krypton-85 will be smaller as the older fuel rods are damaged. This will show the following.

Therefore, based on this value, it is possible to accurately know what cycle the damaged fuel rod is in. As a result, even if, for example, in-core shipping is to be carried out, the number of fuel assemblies to be subjected to this can be reduced to a fraction of that of the conventional method.

[Effects of the Invention] As described above, according to the damaged fuel detection device of the present invention,
Since the burnup of the damaged fuel can be known, the number of fuel assemblies to be shipped within the reactor can be significantly limited compared to the past. As a result, the amount of work and radiation exposure for in-furnace shipping workers can be significantly reduced compared to conventional methods.

[Brief explanation of drawings]

FIG. 1 is a block diagram, not showing an embodiment of the damaged fuel detection device of the present invention, and FIG. 2 is a piping system diagram, not shown in FIG. 1, showing details of the off-gas monitoring device.

Claims (1)

[Claims] (1) An off-gas monitor device that measures the amount of rare gas nuclides contained in the off-gas upstream of the rare gas hold-up device, and a hold that measures the amount of krypton-85 contained in the off-gas that has passed through the rare gas hold-up device. Input the amount of rare gas nuclides measured by the up-exit monitor, the off-gas monitoring device, and the amount of krypton-85 measured by the hold-up exit monitor, and calculate the burnup of the damaged fuel from the relationship between these amounts. A damaged fuel detection device comprising a burnup calculation device.