JPS6342760B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear fuel erroneous loading/unloading prevention device for preventing erroneous loading or erroneous extraction of nuclear fuel loaded into or extracted from a reactor core by a fuel exchange machine.

In general, in a nuclear reactor, it is necessary to understand the nuclear state inside the reactor, such as the near-critical reactivity, from a safety perspective, such as to prevent incorrect loading of nuclear fuel into the reactor core during fuel exchange. Measurements of neutron flux are being carried out.

However, in liquid metal-cooled nuclear reactors such as sodium-cooled fast reactors, the temperature of the sodium coolant is 500°C or higher during reactor operation, and the reactor vessel must be completely sealed, so neutron It is extremely difficult to install a neutron detector inside the reactor vessel due to the difficulty of taking the detector measurement line outside the reactor vessel and the fact that the sodium coolant is chemically very active. It was hot.

For this reason, in conventional fast breeder reactors, for example, the first
As shown in the figure, a neutron detector 2 is installed outside the reactor vessel 1.
The neutron flux inside the reactor vessel 1 is detected by attaching a

However, in such a conventional method, because the distance between the core 3 and the neutron detector 2 is large, the number of neutrons detected by the neutron detector 2 is very small, and therefore the number of neutrons detected by the neutron detector 2 is very small. Since the number of neutrons counted is small, the reliability of neutron flux detection is low, and even if a plurality of neutron detectors 2 are arranged along the circumferential direction outside the reactor vessel 1, the number of neutrons that are counted in the reactor core 3 is low. The drawback was that changes in neutron flux due to loading or withdrawal from the core 3 could not be detected.

On the other hand, as shown in FIG. 1, a fast breeder reactor generally has a reactor vessel 1 with a hemispherical bottom and a rotating plug 4 that shields the opening of the reactor vessel 1. The drilled through hole is equipped with a fuel exchanger 5 for exchanging the nuclear fuel in the reactor core 3.

When exchanging fuel, the tip of the refueling machine 5 is accurately approached while maintaining a predetermined positional relationship with respect to a predetermined position of the reactor core 3.

In addition, the fuel exchanger 5 is used only when exchanging fuel.
Since the furnace vessel 1 is inserted into the furnace vessel 1, the thermal influence on the insertion portion inside the furnace vessel 1 is relatively small compared to that during operation.

Therefore, it is thought that if a neutron detector is attached to the tip of the fuel exchanger 5, the above-mentioned conventional drawbacks can be solved.

The present invention has been made with attention to this point, and as shown in FIG. an output mechanism 7 for outputting type and other parameter values; a storage device 8 for storing expected output values of the neutron detector corresponding to each parameter value; and a storage device 8 for inputting the output of the output mechanism and corresponding to this input Compare the expected output value of the storage device with the output value from the neutron detector, and also compare the neutron detector response from the start of the work to the relevant work during a series of refueling operations and a series of predicted values therefor. An object of the present invention is to provide a device for preventing erroneous loading of nuclear fuel, which comprises a comparison device 9 that compares the values including the comparison values and outputs a signal when the comparison value exceeds a set range. It is something to do.

In FIG. 3, parts common to those in FIG. 2 are designated by the same reference numerals. The fuel exchange machine shown in the same figure includes a nuclear fuel gripping part 10 that grips nuclear fuel, a connecting part 11 following this nuclear fuel gripping part 10, and this connecting part 11.
The main body consists of a driving part 12 for driving the fuel gripping part 10, which follows the connecting part 1.
1 is equipped with a neutron detector 6 using, for example, a fusion counter.

Then, from this neutron detector 6, for example,
A measuring line 13 consisting of an MI cable is led to the comparator 9 through the connecting part 11 and the driving part 12.

In the fuel exchanger configured in this way, the drive unit 12 is mounted on the through hole formed in the rotary plug 4, and the connecting part 11 following this is inserted into the through hole to operate the fuel exchanger. According to this, the amount of neutrons at the tip of the fuel exchanger is detected, and the detection result is output to the comparator 9 through the measurement line 13.

In FIG. 2, the output mechanism 7 is a keyboard for inputting parameter values that affect the output of the neutron detector 6, such as fuel loading position and fuel type, a position detection device attached to a control mechanism of a fuel exchanger, etc. Among the detection devices, the neutron detector 6 is composed of detection devices that output parameter values that affect the output of the neutron detector 6.

The storage device 8 stores the expected output value of the neutron detector 6 corresponding to each parameter output from the output mechanism 7, and inputs the output of the output mechanism 7 to obtain the expected output value corresponding to this input. Output to comparison device 9.

Further, the comparison device 9 compares the expected output value from the storage device 8 and the output value from the neutron detector 6, and if the difference between the two exceeds a preset error range, an alarm device 14, Fuel exchanger control device 1
5, outputs an alarm signal, a stop signal, etc., respectively.

Note that it is desirable to use a small computer as the storage device 8 and comparison device 9.

In the apparatus of the present invention configured as described above, erroneous loading and unloading of fuel is prevented in the following manner.

In other words, when loading or unloading, if the fuel exchanger attempts to load or pull out fuel at a different position than the specified position, or if it tries to load or pull out fuel of a different type than the specified type. In this case, the neutron detector 6 is
The amount of neutrons corresponding to a position or fuel type different from the designated position or fuel type is detected and the measured value is output to the comparator 9.

On the other hand, the output mechanism 7 outputs the parameter value corresponding to the designated position to the storage device 8, and the storage device 8 outputs the expected output value of the neutron detector 6 corresponding to this parameter value to the comparison device 9. , the comparison device 9 compares the actual output value from the neutron detector 6 with the expected output value output from the storage device 8. Because we are manipulating the fuel.
During a series of operations, it is detected that the trends in the predicted change in the neutron detection finger signal due to the replacement work according to the fuel replacement plan and the output value of the signal change obtained during the actual work do not match. The difference exceeds a predetermined error range, and an alarm signal and a stop signal are output to the alarm device 14 and the control device 15 of the fuel exchanger, respectively.

In the refueling machine configured as described above, the neutron detector is located near the fuel gripping part that grips the nuclear fuel during nuclear fuel exchange, so the neutron detector can be brought very close to the reactor core. As a result, the amount of neutrons detected is much larger than in the past.

Furthermore, compared to other fuels, the neutron detector is placed closest to the fuel being operated by the refueling machine, so the amount of neutrons detected is greatly influenced by parameter values such as the type and location of the fuel. It will be strongly received.

For the above reasons, by comparing the predicted value and the actual value of the detected amount of neutrons, it becomes possible to nuclearly detect erroneous loading or unloading of fuel into the reactor core with high sensitivity.

Therefore, erroneous loading or unloading of fuel into the reactor core, which has been difficult to prevent in the past, can be immediately prevented, and the safety of the nuclear reactor is significantly improved.

[Brief explanation of drawings]

Figure 1 is a schematic vertical cross-sectional view showing a fast breeder reactor;
The figure is a block diagram showing an embodiment of the nuclear reactor fuel erroneous loading/unloading prevention device of the present invention, and FIG. 3 is a schematic diagram showing an embodiment of the fuel exchanger used in the present invention. 1... Reactor vessel, 2, 6... Neutron detector, 3...
... Core, 4 ... Rotating plug, 5 ... Fuel exchange machine,
7... Output mechanism, 8... Storage device, 9... Comparison device, 10... Nuclear fuel gripping section, 11... Connection section, 1
2... Drive unit, 13... Measurement line, 14... Alarm device, 15... Control device.

Claims (1)

[Scope of Claims] 1. A neutron detector installed in a fuel exchanger, an output mechanism that outputs the fuel loading position, fuel type, and other parameter values that affect the output of the neutron detector, and a storage device that stores expected output values of the corresponding neutron detector;
Inputting the output of the output mechanism and comparing the expected output value of the storage device corresponding to this input with the output value from the neutron detector, and if this comparison value exceeds a set range; What is claimed is: 1. A device for preventing erroneous loading and unloading of nuclear reactor fuel, comprising: a comparison device that outputs a signal; 2. The device for preventing erroneous loading and unloading of nuclear reactor fuel according to claim 1, wherein the signal is output to a control device of a fuel exchanger. 3. The device for preventing erroneous loading/unloading of nuclear reactor fuel according to claim 1 or 2, wherein the parameter value of the fuel loading position is output from a control device of a fuel exchanger.