JPH05134081A - Diagnosing apparatus of abnormality of reactor - Google Patents

Abstract

PURPOSE:To enable early specifying of a cooling system wherein breakdown of a heat transfer pipe occurs, by measuring a change in a dose rate by providing a radiation detector at a position whereat a secondary system main steam piping of each system is made to have a shielding effect. CONSTITUTION:The title apparatus comprises a dose rate measuring system 17 having radiation detectors 16 provided at positions which are located in the vicinity of secondary system main steam pipings 6 connecting steam generators 4 of a plurality of systems with a turbine 7, respectively, and whereat the pipings have a shielding effect for a radiation from pipings other than ones in the vicinity thereof, and an arithmetic device 18 which calculates a change in a dose rate by comparison with a normal state on the basis of data obtained from the measuring system 17 and can judge and specify the system wherein a leakage occurs, from the change in the dose detected by each radiation detector 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a pressurized water reactor (hereinafter referred to as
(Referred to as PWR), the present invention relates to a reactor abnormality diagnosis device for diagnosing leakage of a primary coolant from a heat transfer tube in a steam generator.

[0002]

2. Description of the Related Art An outline of a conventional pressurized water nuclear power plant will be described with reference to FIG. In the figure, reference numeral 1 is a reactor containment vessel, 2
Indicate the reactor vessels, respectively. The primary-system coolant heated in the reactor vessel 2 flows through the primary-system main cooling pipe 3 and flows into the heat transfer pipe 5 in the steam generator 4. The secondary system coolant in the steam generator 4 is heated by exchanging heat with the heat transfer tube 5, becomes high temperature steam, flows through the secondary system main steam pipe 6, and flows into the turbine 7.

The turbine 7 rotates and drives a generator 8 to generate electricity. The steam that has finished its work in the turbine 7 flows into the condenser 9 and is cooled to be condensed water. This condensate is a secondary water supply pipe
The water flows through 10 and is supplied to the steam generator 4 as a secondary coolant.

On the other hand, the primary coolant flowing through the heat transfer tube 5 in the steam generator 4 is cooled by exchanging heat with the secondary coolant, and is supplied into the reactor vessel 2 from the primary system main cooling pipe 11 by the pump 12. Is heated.

In the above primary and secondary cooling systems, the primary system main cooling pipe 3, the steam generator 4 and the primary system main cooling pipe 11 are usually installed in four systems, and the four system steam generators 4 come out. The secondary system main steam piping 6 joins before flowing into the turbine 7, and the steam in the piping is mixed. In addition, 13 in the figure
Indicates a pressurizer. Also, 14 is an exhaust gas extraction pipe, 15
Is a turbine exhaust gas system monitor that measures radioactive substances in exhaust gas.

By the way, a large number of heat transfer tubes 5 made of inverted U-shaped thin tubes are attached to the tube plate in the steam generator 4, and all the heat transfer tubes 5 are inspected at the time of a periodic inspection to ensure soundness. If the heat transfer pipe 5 is damaged and the primary coolant leaks during the operation of the reactor, the leaked radioactive material passes through the secondary main steam pipe 6 and moves to the turbine 7. Furthermore, it will return to the water supply system through the condenser 9.

In the PWR, a part of the steam (gas) is extracted from the condenser 9 through the exhaust gas system extraction pipe 14, and when the extracted steam contains radioactive substances above the alarm set value, the exhaust gas is discharged. The monitor 15 is configured to give an alarm.

[0008]

In the conventional PWR, when the primary coolant leaks, radioactive substances are detected in the exhaust gas monitor 15.
The alarm will be issued when the amount of leakage exceeds the alarm set value of. However, as shown in FIG. 1, the exhaust gas monitor 15 is located in the exhaust gas extraction pipe 14 derived from the condenser 9 in which the steam from all the systems is mixed at the end of the secondary system. There is. In this way, since the exhaust gas monitor is located at the end of the secondary system, it is not possible to identify in which steam generator of the secondary cooling system having a plurality of systems the leak has occurred.

On the other hand, in order to identify a system having an abnormality, a detector may be installed on the upstream side of the secondary system main steam pipe 6 in which the pipes of each system are independent, but one radiation detector However, it is not possible to detect radiation from all system piping and identify the system in which an abnormality has occurred.

When a radiation detector is installed in each system, not only the radiation from the system piping concerned but also the radiation from other system piping are sensed, and when the leakage is minute, the background dose It may not be possible to identify the piping of the system where the leakage has occurred due to the effect. Therefore, in order to detect only the radiation from the piping of the system of interest, it is usually necessary to install a collimator, but the installation of the collimator causes problems of weight and space.

The present invention has been made to solve the above problems, and it is possible to identify a system in which leakage of a primary system coolant from a heat transfer tube in a steam generator of a pressurized water reactor is identified. SUMMARY OF THE INVENTION It is an object of the present invention to provide an abnormality diagnosis device and a diagnosis method thereof.

[0012]

According to the present invention, at least two or more pressurizers and steam generators are connected to a pressurized water reactor vessel via a primary system pipe, and secondary system outlets of these steam generators are connected. From each of the secondary system main steam pipes connected from the turbine to the turbine, a radiation detector is provided at a position where the secondary system main steam pipe has a shielding effect, and each dose rate change detected by these measurement systems It is characterized in that the magnitudes of are compared by an arithmetic device and the system having an abnormality is specified.

[0013]

In the abnormality diagnosing device according to the present invention, by devising the arrangement of the radiation detectors installed in each of the secondary system main steam pipes of a plurality of systems, the pipes themselves have a shielding effect so that the system other than the system of interest can be used. By comparing and calculating the dose rate changes of the radiation detectors of each system measured so as to attenuate the radiation, the system in which the abnormality has occurred is identified without the need for installing a collimator.

That is, when leakage to the secondary system occurs due to breakage of the heat transfer tube in the steam generator in any system, the dose of the radiation detector closest to the system piping and not shielded by piping etc. The rate change is large, and the dose rate change of other radiation detectors shielded by one or more pipes is small. Therefore, even when there is a small amount of leakage, it is possible to reduce the contribution from pipes other than the system of interest, and it becomes easy to identify the system in which an abnormality has occurred.

[0015]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a pressurized water nuclear power plant including an embodiment of the present invention. In the figure, reference numeral 1 indicates a reactor containment vessel, and 2 indicates a reactor vessel. The primary-system coolant heated in the reactor vessel 2 flows through the primary-system main cooling pipe 3 and flows into the heat transfer pipe 5 in the steam generator 4. The secondary system coolant in the steam generator 4 exchanges heat with the heat transfer tube 5 and is heated to become high temperature steam, which flows through the secondary system main steam pipe 6 and flows into the turbine 7.

The turbine 7 rotates and drives a generator 8 to generate electricity. The steam that has finished working in the turbine 7 flows into the condenser 9 and is cooled to be condensed water. This condensate is a secondary water supply pipe
The water flows through 10 and is supplied to the steam generator 4 as a secondary coolant.

On the other hand, the primary coolant flowing through the heat transfer tube 5 in the steam generator 4 is cooled by exchanging heat with the secondary coolant, and is supplied into the reactor vessel 2 from the primary system main cooling pipe 11 by the pump 12. Is heated. In the above primary and secondary cooling systems, the primary system main cooling pipe 3, the steam generator 4 and the primary system main cooling pipe 11 are usually installed in four systems, and the secondary system that comes out from the four system steam generators 4 is installed. The main steam pipes 6 join together before flowing into the turbine 7, and the steams in the pipes are mixed.

In this embodiment, in order to measure the radioactivity in the steam in the secondary system main steam pipe 6 of each system, the pipes A and B are provided on the upstream side before the secondary system main steam pipe 6 joins. , C, D are provided with a radiation detector 16 (E, F, G, H). As shown in FIG. 2, the radiation detectors E, F, G, and H are installed so that they are located outside the piping example.

With such an arrangement, the radiation detector E has the shielding effect on the piping A and the piping B, C against the leakage of the system of the piping B, C, D. Regarding the radiation detector F, the pipe B and the pipe C have a shielding effect against the leakage of the system of the pipes C and D. Similarly, for the radiation detector G, the pipe C is used against leakage of the system of pipes A and B.
And the pipe B have a shielding effect, and the radiation detector H has a pipe D, a pipe B, and
C has a shielding effect.

The dose rate is obtained in the measuring system 17 from the signals obtained from the respective radiation detectors. These dose rates are compared with the normal dose rates by the arithmetic unit 18, and changes in the dose rates are obtained when leakage occurs. Further, the arithmetic unit 18 identifies the system in which the leakage has occurred based on the amount of change in the dose rate of the radiation detectors E, F, G, H using the shielding effect of the above-mentioned pipes according to the judgment conditions shown in Table 1. To do.

[0022]

[Table 1]

That is, the leakage systems are B and C when the dose rate change of only the radiation detector F or G is large. Also, if there is no single radiation detector with a large dose rate change, the leak system is A or D. Of these, the leak system with a large dose rate change of E and F is the dose of A, H, and G. It can be seen that the leakage system is D when the rate change is large.

FIG. 3 shows only the essential parts of the second embodiment of the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals and the description of the overlapping parts will be omitted. In the second embodiment, three radiation detectors E, F and G are provided between the secondary system main steam pipes A, B, C and D of the four systems. With this arrangement, the radiation detector E has the shielding effect on the pipes B and C against the leakage of the system of the pipes C and D. Further, regarding the radiation detector F, the piping B,
The pipe C has a shielding effect. Regarding the radiation detector G, the pipe C and the pipe B have a shielding effect against the leakage of the system of the pipes A and B.

Measurement system from the signals of the respective radiation detectors
The dose rate obtained in 17 is compared with the dose rate in the normal state by the arithmetic unit 18, and the change in the dose rate in the event of leakage is obtained. Further, the arithmetic unit 18 identifies the system in which the leakage has occurred by the judgment condition shown in Table 2 by utilizing the shielding effect of the pipe, based on the magnitude of the variation of the dose rate of the radiation detectors E, F, G.

[0026]

[Table 2]

That is, the leak systems are A and D when the dose rate change of only the radiation detector E or G is large. The leakage system is B or C when there is no large radiation dose change of the single radiation detector, and the leakage system is B or C when the radiation dose change of E and F is large.
It can be seen that the leakage system is C when the dose rate changes of F and G are large.

[0028]

According to the present invention, when the primary coolant leaks into the secondary coolant from the heat transfer tube in the steam generator, the dose rate of each radiation detector changes, and the change occurs. By calculating the amount, it is possible to immediately identify the cooling system in which the leak has occurred, and take measures against the leak.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a cooling system of a pressurized water nuclear power plant including an embodiment of the present invention.

FIG. 2 is a system diagram showing a main part in the first embodiment of the present invention.

FIG. 3 is a system diagram showing a main part of a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor containment vessel, 2 ... Reactor vessel, 3 ... Primary main cooling piping, 4 ... Steam generator, 5 ... Heat transfer tube, 6 ... Secondary system main steam piping, 7 ... Turbine, 8 ... Generator, 9 … Condenser, 10… Secondary system water supply pipe, 11… Primary system main cooling pipe, 12… Pump, 13…
Pressurizer, 14 ... Exhaust gas extraction pipe, 15 ... Turbine exhaust system monitor, 16 ... Radiation detector, 17 ... Measurement system, 18 ... Arithmetic unit, A to D ... Secondary system main steam pipe, E to H ... Radiation detection vessel.

Claims (1)

[Claims] 1. A pressurized water reactor vessel is connected to at least two systems of pressurizers and steam generators via a primary system pipe, and is connected from a secondary system outlet of these steam generators to a turbine. Provide a radiation detector on each of the secondary system main steam pipes at a position where the secondary system main steam pipe has a shielding effect, and compare the magnitudes of the respective dose rate changes detected by these radiation detectors. An abnormality diagnosis device for a nuclear reactor, which identifies a system having an abnormality by means of.