KR20000005169A - Leak detection device and process - Google Patents

Abstract

PURPOSE: A leak detection device is provided to measure leak detection and location in a nuclear plant, with a manifold(2) permeable to the material to be detected connected to a pump(3) and a sensor(5) for the material. CONSTITUTION: The sensor(5) contains a detector for the radioactivity of the material and can measure leak detection and location by means of radioactivity. A branch pipe(12) is diverged upstream of the sensor(5) and is connected to a radiation detector(7). If radioactive substances reach and enter the manifold(2), a conclusion on the leakage point can be reached from the time taken by the radioactive substances to reach the detector(7).

Description

Leak Detection Apparatus and Method

DE PS 24 31 907 is known a device for leak detection and leak location measurement. The device has a manifold through which the material to be detected can penetrate. The manifold and the pump are connected, and by this pump, for example, a volume of air is transferred through the manifold as a transmission medium. At the end of this manifold, at least one sensor is arranged, which detects material entering the manifold.

In EP 0 175 219 B1 a special structure of such a manifold is known. It has a permeable point at regular intervals, which points may be made of a sintered containing alloy. This pipe does not penetrate between these permeable points.

The invention relates to a device for leak detection and leak location measurement in a nuclear power plant, in particular in the pipeline of a nuclear power plant, in which a substance to be detected can penetrate and which has a manifold connected with a sensor and a pump for the material. .

The present invention relates to a method for leak detection and leak location measurement in a nuclear power plant, in particular in the pipeline of a nuclear power plant.

1 is a variation of a device without a check valve,

2 is a modification with a check valve.

It is an object of the present invention to provide a device for leak detection and leak location measurement to enable a second different leak report. Therefore, reliable leak detection and leak location measurement should be ensured. In addition, a method should be provided.

The object to provide a suitable device is achieved in accordance with a first embodiment of the invention by the sensor comprising or such a detector for detection of the radioactivity of the substance.

Therefore, leak detection and position measurement can be performed through the detection of radioactivity.

The object to provide a suitable device is achieved by branching in front of the sensor in the flow direction according to a second embodiment of the invention, which is also connected with a detector for the detection of radiation.

This detector may be a gamma detector. The maximum activityr as well as the maximum concentration of penetrating material is determined and introduced into leak detection and leak location measurement. Thus, two rich leak location measuring devices are used.

Advantageous configurations of both devices according to the invention are mentioned in the dependent claims.

For example, the openings are arranged at regular intervals in the manifold, and the check valves are located there. The check valve is designed to open and close when it is under the planned pressure.

When this sensor line is closed through the valve at its inlet and the intake valve arranged in front of the detector for radiation is switched on, the check valve opens after the planned pressure falls short. Leak position measurements can also be made at known flow rates in the manifold from the time that flows between the opening of the check valve and the operation of the detector for detection of radioactivity.

Since there are two ways to measure the leak location, reliable results are guaranteed.

The above object to provide a suitable method for leak detection and leak location measurement is achieved by measuring the radioactivity of the material penetrating into the manifold of the power plant according to the invention.

This leak location is detected, for example, from the time passing between the pressure impact at the manifold and the reaction of the detector for detection of radioactivity, even at the conventional flow rate of the manifold. The pressure impact is caused in particular through the opening of at least one check valve.

Embodiments of this apparatus and method for leak detection and leak location measurement according to the present invention can be readily understood in view of the following detailed description with reference to the drawings.

1 shows, for example, a pipeline R which induces a radioactive primary water, whereby a manifold 2 of the device for exposure detection and position measurement (LEOS) is installed. This illustrated manifold 2 comprises a porous sinter containing alloy point 1 through which gas can pass, and otherwise consists of a gas impermeable metal. These porous sintered containing alloy points 1 are arranged in this manifold 2 at an interval of, for example, 0.5 m.

Known devices for leak detection and leak location measurement are provided at the inlet of this manifold 2 to pump 3 for the delivery of delivery gas and to the outlet of this manifold 2 for the substance to be detected. It includes a sensor 5 for. This material can penetrate into the manifold 2. This material may be moisture (water), for example, if the sensor is a humidity meter.

In the device according to the invention the sensor 5 according to the first embodiment is a detector for the detection of radioactivity of the substance, for example a gamma detector. This substance is detected by its radioactivity.

According to the second embodiment a branch pipe 12 branches in front of the sensor 5 in the flow direction and is connected with a detector 7 for the detection of radioactivity.

This detector 7 may for example be a gamma detector. A suction pump 8 is installed in the branch pipe 12 to create a greater low pressure in the manifold 2, and a valve V2 can be arranged before this suction pump. Another valve V1 may be arranged at the beginning of this manifold to close the manifold 2 behind the pump 3 in the flow direction.

A calibration module is arranged at the beginning of the manifold 2 and a test gas is sucked into the manifold 2 by the calibration module for calibration of the sensor 5 and the detector 7. . The regulation module 6 is connected with the manifold 2 to regulate the flow rate in the manifold 2.

A detector 7 for the detection of radioactivity is arranged in the storage container 11, which has a volume between 1 and 10 liters, for example. The branch pipe 12 runs into this storage container 11. A branch line emerges from this reservoir 11 which may comprise a pressure control valve not shown and in some circumstances may contaminate the nuclear power plant by a feedback line.

2 shows a variant of the device for leak detection and leak position measurement according to FIG. 1, which includes all the components of the variant according to FIG. 1 and additionally has a check valve 9, which is equidistant. At intervals, for example, the manifold 2 is provided every 2 m. This check valve 9 is manifold 2 and this manifold 2 by means of suction openings which are opened and controlled when the minimum pressure is not reached, for example by a circular opening having a cross section of 1 mm 2. It is responsible for sufficient connection between the spaces below. The variant according to FIG. 2 has a thermal insulator 10 which encloses the pipeline R and the manifold 2, in which case the check valve 9 protrudes from this insulator 10.

Conventional methods for leak detection and position measurement are complemented according to the invention as follows:

This manifold 2 is closed by the valve V1 in the flow direction at its inlet. Thereafter, the suction pump 8 starts to operate. The air sucked into this suction pump 8 is led to the storage container 11. In this reservoir the activity measurement is carried out by the detector 7. If a leak occurs from the pipeline R, the radioactive liquid, for example the primary water, results in a significant increase in vapor in the space below the pipeline R, in particular under the insulator 10 and thus in the air sucked. This activity means 5.2 * 10 ¹² splits per second due to, for example, the N16-reaction in the reactor core. Considering the 30 second transfer time to the detector 7 and the 10 second measurement time, the activity is reduced according to the half-life of the isotope (eg 1 * 10 ¹¹ Bq for N16); However, what is fully assumed for the detection of leaks is that a sufficient amount of water vapor is drawn together in the measurement air. The conventional sintered containing alloy point 1, which is designed only for the use of the sensor 5, has only one pore size of 0.5 μm. For example, the optimization of the pore size to 1 μ allows for the detection of radioactivity by the detector 7 so that a general detection of material or moisture is not disturbed in the sensor 5. However, for detection by the sensor 5 the flow rate in the manifold 2 should be reduced in some cases, but too low pressure and thus too strong continuous suction flow can be avoided. This flow may violate the leak location.

The problem of too small intake at the manifold 2 can be avoided by using the check valve 9 mentioned above.

For example, the check valve 9 is not switched as long as the leak position measurement is made by the humidity sensor 5 in the low pressure state at the manifold 2 as compared to the atmosphere. This means that the measurement and position discrimination made by the values measured with this sensor 5 are not disturbed.

When the suction pump 8 is operated and the valve V1 is closed, the low pressure in the manifold 2 drops rapidly below the reaction level of the check valve 9. This opens up and thus ensures a sufficiently large air flow to the detector 7, thus enabling activity measurement. Since this leak is locally limited, at this time the entire flow of all valves 9 as an air / vapor mixture is always directed to the detector 7. This air flow is in this case led to a storage container 11 of sufficient size. There the activity of the total volume is detected by the detector 7 as a whole.

A constant delivery time T elapses from the opening point of the check valve 9, which can be detected from the pressure impact in the manifold 2, to the point where the activated vapor reaches the detector 7. Suitable sensors can be used for the detection of this pressure impact. This propagation time, T, on one side is dependent on the distance x between the position adjacent to the leak position on the manifold 2 and on the other side the detector 7. In the corresponding calibration the distance x from time T is determined. This is simply the case when the flow along the manifold 2 is close to constant, but this also applies to the non-uniform linear relationship T (x).

If the manifold 2 has been cleaned by the pump 3 earlier, this measuring procedure can be repeated periodically after successful detection and position measurement.

When the valve 9 is arranged in the manifold 2 with the openings behind it, it changes the size of the openings along this manifold 2, so that a constant flow is introduced every time unit. This is not automatically provided if the opening cross sections are the same, because there is a higher low pressure in the check valve 9 located furthest near this suction pump 9. This means that the suction points near this suction pump 8 should have smaller openings, and the larger openings should be able to select larger and larger openings.

If no check valve 9 is used, in some cases the rate of delivery of steam penetrating into the manifold 2 is accelerated through the short time opening of the valve V1 in the manifold 2, thereby providing the necessary delivery. You can reach time. This results in the following actions: after closing valve V1 in manifold 2 and opening valve V2 in branch pipe 12 the suction pump 8 starts to operate and the manifold 2 The low pressure in) is controlled until the desired final value is obtained. The valve V1 in this manifold 2 is then opened in a short time until a sufficient amount of material reaches the storage container 11, especially in the shortest possible delivery time for the vapor. There, the activity is measured continuously by this detector 7 as a time function, for example, through detection of the number of pulses summed for each time unit.

In the manner described above, a sufficient amount of material is sucked in, for example to report leaks. For example, particularly after 40 seconds elapse between the formation of the N16-isotope and the arrival of its detector 7, there is an activity of 1 * 10 ¹¹ Bq for each first order of m 3. This is at the yield of detector 7 of 0.1 (every tenth cleavage is detected) and at a measurement time of 10 seconds (30-40 seconds after formation of the isotope).

1 * 10 ^-9 m3 = 1mg primary number

It means to represent 100 pulses. This will be an indication of sufficient size.

With nine sintered alloy points 1, a 1.4 cm 3 / sec body size at an average speed of 5 cm / sec at a low pressure of 0.8 bar in the manifold 2 and an inner diameter of the manifold 2 at 0.3 cm Flow is achieved. When two sintered alloy points 1 arranged at intervals of 0.5 m are involved in the occurrence of a leak, a volume flow of 0.3 cm 3 / sec occurs and thus a measurement volume of 3 cm 3 appears at a measurement time of 10 sec. For example, for a leak of 100 kg / h, if the primary circulating vapor with N16 reaches a saturation concentration of 50% below the insulator 10, 1 cm 3 of air will provide nearly 0.5 mg water vapor in the manifold 2. Include. The above-mentioned measuring volume contains more than 1 mg of water vapor, which can be reported.

As the pore size of the sinter containing alloy point 1 increases from 0.5μ to 1μ, the volume flow increases by factor 3. This is usually sufficient, so report a smaller vapor concentration.

If this sensor 5 itself is a detector for the detection of radioactivity, it is arranged in the same way as the detector 7 and operated directly in the manifold 2 instead of in the branch pipe 12.

Claims (9)

In nuclear power plants, in particular in the pipeline R of a nuclear power plant and with a manifold 2 connected to the material to be detected and which has a sensor 5 and a pump 3 for this material, Apparatus for measuring leak location, characterized in that the sensor (5) comprises or is the same as the detector for the detection of radioactivity of the substance. In nuclear power plants, in particular in the pipeline R of a nuclear power plant and with a manifold 2 connected to the material to be detected and which has a sensor 5 and a pump 3 for this material, Apparatus for measuring leak position, characterized in that a branch pipe (12) branches in front of the sensor (5) in the flow direction, which is connected with a detector (7) for the detection of radioactivity. Apparatus according to claim 1 or 2, characterized in that one suction pump (8) is assigned to the detector (7). Apparatus according to any of the preceding claims, characterized in that the detector (7) is arranged in a storage container (11). The device according to claim 1, wherein the valve V1 is arranged in front of the manifold in the flow direction. 6. The valve according to any one of the preceding claims, wherein openings are arranged in the manifold (2) at regular intervals, and a check valve (9) is opened in the openings that open when they do not reach the planned pressure. The device characterized in that. A method for leak detection and leak location measurement in a nuclear power plant, in particular in the pipeline of a nuclear power plant, characterized in that the radioactivity of the material entering the manifold (2) in the reactor is measured. The position of the leak according to the conventional flow rate in the manifold 2 is determined from the time between the pressure impact in the manifold 2 and the reaction of the detectors 5 and 7 for the detection of radioactivity. Method characterized by losing. 9. Method according to claim 8, characterized in that the pressure impact in the manifold (2) is caused through the opening of at least one check valve (9).