JPH052093A - Abnormality diagnosis device for pressurized water reactor - Google Patents

Abstract

PURPOSE:To find abnormality of radioactives leakage due to heat conduction pipe rupture and grasp the evolution and the type of the leakage and fuel failure, etc. CONSTITUTION:In the secondary main steam line 8 and the primary coolant pipe 13, measurement systems for gamma spectrum 22 and dose rate 26 having bypass systems 21 and 25 capable of reducing sufficiently short half-life species are provided. An arithmetic processor 30 capable of comparing the data obtained with these measurement system 22 and 26, judging the existence of sign of abnormality due to leakage and calculating the radioactives density in the main steam at each measurement point using the dose rate and also the leakage radioactives density in the secondary main steam line with time, is provided.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An outline of a conventional PWR and an abnormality diagnosing apparatus thereof will be described with reference to FIG. In the figure, reference numeral 1 is a reactor building, 2 is a reactor containment vessel, and 3 is a reactor vessel. The primary system cooling water heated in the core 4 in the reactor vessel 3 flows through the primary system pipe 5 and flows into the heat transfer pipe 7 in the steam generator 6. The secondary system cooling water in the steam generator 6 exchanges heat with the heat transfer tube 7 to be heated to become high temperature / high pressure steam, flows through the secondary system main steam pipe 8 and flows into the turbine 9. The turbine 9 rotates and drives the generator 10 to generate electricity. The steam that has finished its work in the turbine 9 flows into the condenser 11 and is cooled to be condensed water. This condensate flows through the secondary system water pipe 12 and is supplied to the steam generator 6 as secondary system cooling water. On the other hand, the primary system cooling water flowing through the heat transfer pipe 7 in the steam generator 6 is cooled by exchanging heat with the secondary system cooling water, and is pumped from the primary system cooling water pipe 13.
It is returned to the reactor vessel 3 by 14 and is heated in the core 4.

In the figure, 15 is a control rod, 16 is a pressurizer, and 17 is a spray tube. Further, 18 is an exhaust gas extraction pipe, and 19 is a turbine exhaust gas monitor, which detects radioactive substances in exhaust gas with a radiation detector and measures nuclides and amounts of radioactive substances with an electric circuit for abnormal diagnosis.

By the way, in the steam generator 6, a large number of heat transfer tubes 7 made of inverted U-shaped thin tubes are attached to the tube plate, and all the heat transfer tubes 7 are inspected at the time of periodic inspection. The soundness is confirmed. If the heat transfer pipe 7 is damaged during the reactor operation and leakage of the primary system cooling water occurs, the leaked radioactive material in the primary system cooling water passes through the secondary system main steam pipe 8 and is transferred to the turbine 9. Furthermore, it will return to the water supply system through the condenser 11. In PWR, some steam (gas) is extracted from the condenser 11 through the exhaust gas extraction pipe 18, and when the extracted steam contains radioactive substances above the alarm set value, the turbine exhaust gas system monitor It is configured so that an alarm can be issued by 19.

[0005]

In the prior art, when the primary system cooling water leaks, an alarm is issued at the time when the radioactive material reaches the amount of leakage exceeding the alarm set value of the turbine exhaust gas system monitor 19. become. Therefore, the radionuclide targeted by the turbine exhaust gas system monitor 19 due to the leakage of the primary system cooling water is a rare gas, a corrosion product, a fission product, or the like. However, compared to ¹⁶ N and ¹⁵ C, these radionuclides existing in the primary system cooling water are originally small in amount, and partly leaked into the main steam is extracted and measured. It is difficult to detect the leak. In addition, there is a problem that it is not possible to grasp the state of the leaked radioactive material and the transition of the amount of leakage of the scale of the damaged portion of the heat transfer tube.

The present invention has been made to solve the above problems, and promptly detects a small amount of leakage of primary cooling water from a heat transfer tube in a steam generator of a PWR, and estimates the scale of a damaged portion. Another object of the present invention is to provide a PWR abnormality diagnosis device capable of predicting changes in the amount of leakage.

[0007]

According to the present invention, a gamma ray spectrum and dosimetry system having a bypass system capable of attenuating short half-life nuclides is provided in each of a secondary system main steam pipe and a primary system cooling water pipe of a PWR. The data obtained from the measurement systems are compared to determine whether there are any abnormal signs due to leakage, the radioactivity concentration in the main steam at each measurement point is calculated from the dose rate, and the leakage radioactivity concentration in the secondary system main steam pipe is calculated. It is characterized in that an arithmetic processing system for performing calculation with time is provided.

[0008]

[Function] For example, when the heat transfer tube is damaged, the radioactive material of the primary system cooling water reaches the position of the radiation detector of the turbine exhaust gas system monitor 19 within a few seconds. Since the radioactivity concentration is equal to zero, the output of the detector will change significantly.
^{When 16} N or ¹⁵ C is used as the radiation source, the energy of gamma rays emitted is high (6 MeV, 5 MeV), so even a small amount can be detected even outside the main steam pipe (thickness 2-3 cm). Occurs when fuel is damaged, etc.
^The gamma ray spectrum for nuclides such as ⁸⁸ Kr and ⁸⁷ Kr is ¹⁶
It becomes the background of the gamma ray spectrum due to nuclides such as N and ¹⁵ C, which is difficult to measure. However, in the present invention, since it is possible to compare the data measured on the primary system cooling water side and the secondary system main steam piping side, of the increase in radioactivity concentration on the main steam piping side, it is It is possible to judge whether the cooling water leaks due to breakage, and since the detection target nuclides are narrowed down to ⁸⁸ Kr, ⁸⁷ Kr, etc., judge whether there is a serious abnormality such as fuel damage. You can In addition, since it is possible to calculate the radioactivity concentration between the primary system cooling water side and the secondary system main steam piping side from these measured data, the leakage amount of the primary system cooling water and the degree of abnormality such as fuel damage can be calculated. I can know.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 schematically shows a pressurized water nuclear power plant including an embodiment of the present invention. In the figure, reference numeral 1 is a reactor building,
Reference numeral 2 indicates a reactor containment vessel, and 3 indicates a reactor vessel. The primary system cooling water heated by the core 4 in the reactor vessel 3 flows through the primary system pipe 5 and flows into a large number of heat transfer tubes 7 in the steam generator 6. The secondary system cooling water in the steam generator 6 exchanges heat with the heat transfer tube 7 to be heated to become high temperature / high pressure steam, flows through the secondary system main steam pipe 8 and flows into the turbine 9. The turbine 9 rotates and drives the generator 10 to generate electricity. The steam that has finished its work in the turbine 9 flows into the condenser 11 and is cooled to be condensed water. This condensate flows through the secondary system water supply pipe 12 and is supplied to the steam generator 6 as secondary system cooling water. On the other hand, the primary system cooling water flowing through the heat transfer pipes 7 in the steam generator 6 is cooled by exchanging heat with the secondary system cooling water, and the primary system cooling water pipe 13 pumps a pump (not shown) into the reactor vessel 3. And is heated in the core 4. In the figure, 15 is a control rod, 16 is a pressurizer, 17 is a spray pipe, 18 is an exhaust gas extraction pipe, and 19 is a turbine exhaust gas system monitor.

Here, a first measurement inlet pipe 20 is connected to the secondary system main steam pipe 8, and the first measurement inlet pipe 20 is connected to a first gamma ray via a first bypass system 21. It is connected to the spectrum and dose rate measurement system 22. The outlet side of this measurement system 22 is connected to the downstream side of the secondary system main steam pipe 8 via a first measurement outlet pipe 23. On the other hand, a second measurement inlet pipe 24 is connected to the primary system cooling water pipe 13, and this second measurement inlet pipe 24 measures the second gamma ray spectrum and dose rate via the second bypass system 25. Line 26
It is connected to the. The outlet side of the measurement system 26 is connected to the downstream side of the primary system cooling water pipe 13 via a second measurement outlet pipe 27. The measurement systems 22 and 26 are connected to the arithmetic processing system 30 by signal cables 28 and 29. The first and second
The bypass systems 21 and 25 of the system are capable of sufficiently attenuating short half-life nuclides.

In the figure, a part of the steam collected from the first measurement inlet pipe 20 is sufficiently attenuated by nuclides such as 16N and 15C in the first bypass system 21, and then the first gamma ray spectrum and dose rate are measured. The measurement system 22 measures the spectrum and dose rate. Similarly, a part of the primary system cooling water collected from the second measurement inlet pipe 24 passes through the second bypass system 25,
The spectrum and dose rate are measured by the gamma ray spectrum and dose quality measurement system 26 of. The data measured by these measurement systems is processed by the arithmetic processing system 30. As a result, the fluctuation of the data measured by the first measurement system 22 can be compared with the result of the second measurement system 26, so that the increase in the radioactivity concentration on the main steam side is the primary system cooling. You can judge whether it is due to water leakage.

Here, N ₀₁ and N ₀₂ are connected to the second measurement inlet pipe.
The concentration of ¹⁶ N, ⁸⁸ Kr at 24, λ ₁ , λ ₂ is ¹⁶ N, ⁸⁸
When the decay constant of Kr is used, the time when the concentration of ¹⁶ N becomes Δ of the concentration of ⁸⁸ Kr can be calculated by the following equation (1).

[0013]

[Equation 1]

Here, N ₀₁ = 4.0 × 10 ¹ (μCi / g), N
₀₂ = 2.8 x 10 ^-1 (μCi / g) (ANSI / ANS-18.1.
-1984) and λ ₁ = 7.13sec and λ ₂ = 2.84h, the time when Δ = 0.01 is calculated as 68.2sec from the above formula. ¹⁶ N
In release 69% is gamma rays 6.12MeV, ⁸⁸ Kr is 2.39Me
Since the V gamma ray is emitted at an emission rate of 35%, if the ¹⁶ N is attenuated to Δ = 0.01, the ⁸⁸ Kr emitted gamma ray can be sufficiently measured by the second measurement system 26 and the arithmetic processing system 30. Next, since the dose rate from the pipe is proportional to the radioactivity concentration in the pipe, the dose rate at the measurement point was calculated at an arbitrary concentration by calculation in advance, and the gamma ray spectrum and the dose rate obtained by the dose rate measurement system The ratio (actual value / calculated value) between the measured value and the calculated dose rate calculated by calculation is normalized to the concentration used in the calculation, and the radioactivity concentration for the measured dose rate is calculated. Calculate by

Further, since the flow rate of the primary cooling water and the flow rate of the main steam can be known from each control system, the radioactivity concentration RC (μCi / g) of the primary cooling water and the radioactivity concentration ST of the main steam system can be obtained.
From A (μCi / g) and the flow rate STB (g / s), the leakage amount D (g / s) of the primary system cooling water is calculated by the arithmetic processing system 30 by the following equation (2).

[0016]

[Equation 2]

[0017]

According to the present invention, even if a small amount of primary system cooling water leaks to the secondary system main steam pipe from the heat transfer tube in the steam generator, the dose rate of the measurement system changes. It becomes possible to diagnose the early signs of abnormal phenomenon,
By processing this data as a change over time, it is possible to predict the transition of the abnormality, and since the target is a nuclide peculiar to the fuel damage, it is possible to obtain a diagnosis for grasping the state of the abnormality.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing an embodiment of a pressurized water nuclear reactor abnormality diagnosis apparatus according to the present invention.

FIG. 2 is a block diagram showing a conventional abnormality diagnosing device for a pressurized water reactor.

[Explanation of symbols]

1 ... Reactor building, 2 ... Reactor containment vessel, 3 ... Reactor vessel, 4 ... Core, 5 ... Primary system piping, 6 ... Steam generator, 7 ...
Heat transfer pipe, 8 ... Secondary system main steam pipe, 9 ... Turbine, 10 ... Generator, 11 ... Condenser, 12 ... Secondary system water supply pipe, 13 ... Primary system cooling water pipe, 14 ... Pump, 15 ... Control Rod, 16 ... Pressurizer, 17 ... Spray pipe, 18 ... Exhaust gas extraction pipe, 19 ... Turbine exhaust gas monitor, 20 ... First measurement inlet pipe, 21 ... First bypass system, 22 ... First gamma ray spectrum And dose rate measurement system, 23 ... First measurement outlet pipe, 24 ... Second measurement inlet pipe, 25 ... Second bypass system, 26 ... Second gamma ray spectrum and dose rate measurement system, 27 ... Second Measuring outlet pipe, 2
8, 29 ... Signal cable, 30 ... Arithmetic processing system.

Claims (1)

Claims: 1. A gamma ray spectrum and dosimetry system having a bypass system capable of attenuating short half-life nuclides is provided in each of the secondary system main steam piping and the primary system cooling water piping of a pressurized water reactor. , The data obtained from these measurement systems are compared to determine whether there are any abnormal signs due to leakage, the radioactivity concentration in the main steam at each measurement point is calculated from the dose rate, and the leakage activity in the secondary system main steam piping An abnormality diagnosing device for a pressurized water reactor, comprising an arithmetic processing system for calculating concentration over time.