RU2268509C2 - Registration system of leaks of a heat carrier for the first loop of the reactor facilities of the nuclear electric power plants - Google Patents

Abstract

FIELD: atomic power engineering; registration systems of leaks of the heating carrier of the 1-st loops of the reactor facilities of nuclear electric power plants.

SUBSTANCE: the invention is pertaining to the field of atomic power engineering and may be used in at the reactor installations with the water-to-water and water-graphite reactors, in particular, at a decompression of the 1-st loop. The registration system of leaks of the heating carrier of the 1-st loops of the reactor facilities of a nuclear electric power plant contains a block of the controlled rooms with equipment of the 1-st loop of the reactor installation connected through air ducts of exhaust ventilation with a block of the channels intended for measuring of relative humidity of the air in the controlled rooms, that includes a reference channel intended for measuring of relative humidity of outdoor air in the rooms with the measuring channels. Sensor units of measuring channels are connected to a control unit for recording and matching of the parameters of the relative humidity of the air in the controlled rooms and in the room with the measuring channels, each of which is made in the form of an expander, on one butt of which there is a branch pipe with a filtering tool connected with the air duct, and on the other butt there is a flange intended for mounting of a sensor. At that outside of the expander there is a cooling chamber. The invention allows to simplify the process of the control over the indications of the relative humidity of the air in the controlled rooms and to improve reliability of operation of the reactor installation by well-timed detection of a location and intensity of the leakage of the heating carrier.

EFFECT: the invention ensure simplified control over the indications of the relative humidity of the air in the controlled rooms, improved reliability of the reactor installation operation by well-timed detection of a location and intensity of the heating carrier leakage.

6 cl, 9 dwg

Description

This invention can be used in all reactor installations (RU) of nuclear power plants (AS) with water-water and water-graphite reactors.

At present, in the CIS, at all nuclear power plants with water-water and water-graphite switchgear there are no “means and methods for detecting with reasonable accuracy the location and flow rate of the primary coolant leak” required by the normative and technical documentation.

A known system for the rapid detection and determination of the occurrence of leaks of the coolant of the primary circuit of the WWER (SKTT) - website on the Internet http://diaprom.ru/work.htm , 2003.02.10. To measure humidity in the SKTT, a “sensor hose” is used, which is placed inside the insulation in direct contact with the pipeline or the surface of the reactor vessel to ensure moisture diffusion into the sensor tube.

Despite the fact that both systems are based on the same principle - an increase in relative air humidity when coolant leaks occur, both the methods for obtaining data and the design of the systems themselves differ.

The main difference between the two systems is that for measuring humidity in the SKTT, a "sensor hose" is used, which is placed inside the insulation in direct contact with the pipeline or the surface of the reactor vessel, for the same purpose, in the SRT, a system is used, "including a block of controlled rooms with equipment the primary loop of the reactor installation, connected through exhaust ventilation ducts to a block of channels designed to measure relative humidity in controlled rooms. " An example is a box with several pieces of equipment and tens of meters of pipelines. During the operation of SKTT, a leakage signal may come to the computer center from the “sensor hose” of any of the pipeline sections, flange connectors of the equipment, surface sections of the equipment, the number of such sections will be quite large. During CPT operation, a signal about the appearance of a leak will pass only one, that the leak appeared in this box. At the same time, the sensitivity of SKTT will be possible and higher, but at the same time, the costs of implementation, operation and repair of the system will increase many times.

In addition, during the operation of the СРТ, it is envisaged to determine the flow rate of the coolant leak, this is not possible during the operation of the СКТТ, also СРТ is equipped with means for testing, commissioning and routine checks of the measuring channels, which is impossible for the СКТТ due to its design features.

The technical result of the invention is to simplify the process of monitoring the readings of relative humidity in controlled rooms, and to simplify the installation (system), as well as to increase the reliability of the AU by timely detection of both the location and flow rate of the coolant leak with possible depressurization of the 1st circuit RU.

The proposed system (SRT) will allow with sufficient accuracy and speed to determine the appearance, flow rate, location (room) of the leak of the first circuit for nuclear power plants with water-water and water-graphite reactor plants. The basis of the proposed system is a change in the relative humidity in the room when a leak occurs.

The registration system for coolant leaks of the first circuit of the reactor installations of a nuclear power plant includes a block of controlled rooms with equipment of the first circuit of the reactor installation, connected via exhaust ventilation ducts to a block of channels designed to measure the relative humidity of air in the controlled rooms, including a reference channel designed for measuring the relative humidity of the outdoor air in the room with measuring channels, while the sensors of the measuring channels are connected with a control unit for recording and comparing the indicators of relative humidity in controlled rooms and the room with measuring channels.

For water-graphite reactor plants, the system further includes a water-graphite reactor jacket block connected by a forced ventilation bypass line to a measurement channel unit for monitoring the integrity of the equipment inside said jacket, while the measurement channel sensor is connected to the control unit by electrical communication.

The sensors of the measuring channels of the monitored rooms are connected to a computer alarm means, which is triggered by the corresponding difference in the readings of any of the measuring channels with the reference.

Each measuring channel is made in the form of an expander, on one end of which there is a pipe with filtering means connected to the air pipe, and on the other end there is a flange designed for mounting the sensor, and a cooling chamber is placed outside the expander.

The measuring channel for a water-graphite reactor installation, designed to monitor the integrity of the equipment inside the reactor shell, is made in the form of an expander, one end of which is connected to the bypass line of the forced ventilation system, equipped with a throttle at the inlet of the expander, and a flange for mounting the sensor is installed on the other end .

The exhaust ventilation duct is equipped with an adjustable device to limit the air flow from the controlled room, which is sealed.

The system is equipped with tools for testing, commissioning and routine checks of the measuring channels.

The measuring channels of the controlled premises are made with the possibility of connecting to a means of regulation and measuring the vacuum in the exhaust ducts.

The equipment and pipelines of the 1st circuit of the reactor system are located in several sealed rooms (boxes). Each room is equipped with exhaust ventilation. When operating the proposed system, the air flow from the room should be limited. The higher the flow rate, the lower the sensitivity of the CPT, but the higher the leak detection rate. The optimal ventilation rate (the ratio of the fan flow rate (m ³ / h) to the volume of the room (m ³ ) is from 1 to 0.5, while the leak detection rate will be from 1 to 2 hours, respectively, but due to the low flow rate, the sensitivity will increase system.

The basic rules for ensuring the operation of nuclear power plants of the Republic of Estonia ЭО 0348-02 do not regulate ventilation rates for rooms of the 1st circuit, but only require "maintaining vacuum in these rooms within the design values, but not less than 5 kgf / m ² in relation to other more" clean ”regarding the radioactive contamination of the premises (clause 13.5.1.). Therefore, to ensure the operation of the SRT, air ducts with the aim of limiting the air flow should be equipped with control devices (slide gates), and the premises themselves must be sufficiently airtight.

According to the invention, the number of measuring channels should be one unit greater than the number of controlled rooms, and the installation of the sensors of the device should be located in a well-ventilated room in the absence of moisture sources. An additional channel (reference) is designed to control air from this room.

For speakers with water-graphite switchgear, the measuring channel for monitoring the density of equipment inside the sealed reactor shell must be connected to the bypass forced ventilation line.

SRT is based on the eight-channel device IVTM-7 / 8R-MK AOOT Practik-NTs. Eight channels for measuring temperature and relative humidity will allow for the connection of several reactor units to the instrument. The secondary device type IVTM-7 / 8R-MK is installed on the control panel and provides temperature and relative humidity control in all rooms of the 1st circuit. All channels, except the reference one, are equipped with an alarm system when the relative humidity is exceeded by 5% from the initial one.

The registration system for the coolant leaks of the 1st circuit of the reactor installations of nuclear power plants includes the registration of changes in the relative humidity in the room of the 1st circuit of the reactor installation, where the leak appeared.

The air flow through the room of the 1st circuit is limited to a relatively low limit, and to increase the sensitivity of the device, the air sampled for analysis from the duct is subjected to passage through several cooling stages before entering the device’s sensor.

A reference measuring channel is also used to exclude the influence of changes in the relative humidity of the outside air when a leak of the primary coolant is detected.

The invention is illustrated in the drawing, where Fig.1 schematically shows a schematic diagram of a CPT; figure 2 - device channel circuit of figure 1 (in section); figure 3 - flange connection of the sensor; figure 4 is a section along aa in figure 3; figure 5 - nozzle for testing (in section); figure 6 - vessel constant flow; in Fig.7 - the device channel of the CPT circuit for water-graphite switchgear (in the context); in Fig.8 - I-d diagram of moist air, Fig.9 is a block diagram of the system.

Figure 1 shows a schematic diagram of a CPT consisting of 3 measuring channels. Channel 1 is a reference one, its measuring sensor receives air from a room with a relative humidity (φ) equal to the relative humidity of the outside air, adjusted for a change in temperature (T) ° С.

Each measuring channel (pos. 1-3) consists of a sensor of device 4, which is used as an IVTM-7M primary converter, a cooler expander 5, a 2-stage filter 6, and a DNMP-100UZ device indicated by pos. 7, which can be connect to each channel, pipeline 8 with valves in the form of needle 9 and bellows 10 valves for supplying, removing the measured air, cooling water, for cooling the air sampled to control to ambient temperature (T) and the throttle plate 11 to limit the flow rate spirit and facilitate the adjustment of the flow rate.

The sensor of the IVTM-7M device (pos. 4 in Fig. 1) is designed to measure T, φ of air along each channel, fixed in the hole 43 of the flange 12 (Fig. 2).

The cooler expander is made of a pipe 13 with a diameter and a thickness of 57 × 3.5 with a cooling jacket 14 (a pipe with a diameter and a thickness of 76 × 3) and is designed to reduce the air speed, cool it and install a sensor and a filter in it.

A 2-stage filter purifies the air in order to protect the outer surface of the sensor, made with a high degree of purity from damage and aerosol contamination.

The filter is made of a pipe 15 with a diameter and a thickness of 57 × 3.5, a length of 200 mm and a flange connection 16 with a conditional diameter (Du) = 50 mm, with a conditional pressure (Ru) of 10 kgf / cm ² . The pipe is filled with tightly rolled Petryanova fabric 17, and a rubber gasket 18 is inserted into the flange connection with fabric 19 glued to it from 2 sides from a Petal-200 respirator.

A device of the DNMP-100UZ type (pos. 7 of Fig. 1) is used as a rarefaction meter (air ducts of ventilation systems of the 1st circuit premises operate under vacuum) and can be connected to any channel. Serves for: - channel settings (restrictions on air flow through the channel to 0.05-0.1 m ³ / h); - control the pressure drop across the filters during operation.

Pipelines with fittings are made of alloy steel with a diameter and thickness of 14 × 2 mm and 6 × 1.5 mm and are designed for supplying, removing bleed air, cooling water, cooling the air to room temperature, setting up the system, turning channels on and off, including and emergency, to preserve the sensors of devices when a leak appears in the premises. Sensors do not allow condensation of moisture on the surface.

The throttle washer 11 (Fig. 1) with a hole with a diameter of 0.7 mm and a hole 20 (Fig. 2) in the expander 5, with a diameter of 1 mm, at the outlet of the measured air facilitate the adjustment of air through the expander.

For commissioning and operational checks of the SRT, the nozzle shown in Fig. 5 is used, consisting of a funnel 21, a pipe 22 with a diameter and a thickness of 6 × 1.5 mm, a pipe 23 with a diameter and a thickness of 14 × 2 mm, a nozzle with a DN of 10 mm (item 24 ) for connecting a compressed air hose. The nozzle can be cut into the ventilation duct or brought into the room of the 1st circuit. Through a funnel from the vessel 25 of constant flow (SPR) shown in FIG. 6, water with a set flow rate of 2-10 kg / h flows through pipe 22. In the annular gap between the pipe 22 and the pipe 23 passing through the wall of the room or the wall of the duct 42, compressed air with a pressure of 6-8 kgf / cm ² .

For better atomization, the water flow should be towards the air flow in the duct (figure 5).

During testing, the flow rate of the supplied water should be constant. For this, a constant flow vessel 25 is used; consisting of 2 vessels inserted in each other with a capacity of 1.5-2.0 liters. The outer vessel 26 has a connection with the atmosphere, and on its neck a removable lid 27 with an opening at a flow rate of 2-10 l / h. There should be several covers for different expenses. Through a removable lid of the outer vessel, the inner vessel 28 is filled with chemically purified water, after which the lid is twisted and the SPR is turned into the working position, installed above the funnel 21 (Fig. 5). When water flows from the outer vessel, the level in it drops below the neck of the inner vessel, air passes into the inner vessel, thereby maintaining a constant level in the outer vessel, and therefore, a constant flow rate to the nozzle.

With increased sensitivity of CPT (100-400 g / h), it is allowed to use a surgical dropper instead of SPR. During routine inspections of the CPT, instead of using the nozzle, low-grade steam can be supplied to the premises of the 1st circuit and to the ducts through a pipeline with a nominal diameter (DN) of 10 mm, for example, from the deaerator head. With an atmospheric deaerator through a throttle washer with a hole with a diameter of 4 mm, the flow rate is 8 kg / h, with a deaerator with a pressure of 6 kgf / cm ² through a throttle washer with a hole with a diameter of 2 mm, the flow rate is 6 kg / h.

For water-graphite switchgear, an additional channel is installed (Fig. 7) to control the integrity of the equipment in a sealed reactor shell. It works similarly to other channels and differs from them in that, as unnecessary, it lacks a filter and a cooling shirt. At the entrance to the expander 29, a fitting 31 with a plug 32 for testing the channel is cut into the pipe 30. Gas enters the channel from the forced ventilation pressure line through a pipe 30 in which a throttle washer 33 is installed, and enters the ventilation suction line through a pipe 34.

Figure 9 presents a block diagram of the proposed system, consisting of a block 35, for example, two controlled rooms 36 and 37, in which the equipment of the primary circuit of the reactor installation is located; block 38, which is a well-ventilated room without moisture sources, in which several measuring channels are installed: 1 - standard, 2 and 3 - connected through air ducts to controlled rooms 36 and 37, respectively. The sensors of the measuring channels 1-3 are connected by electrical communication with the control unit 39, on the dashboard (panel) which displays the readings of relative humidity and temperature in the controlled rooms 36 and 37 and the readings of relative humidity and temperature in the room of the unit 38, which are the sensor of the standard measuring channel 1 installed in this room will be bent. Audio and / or visual alarm elements can be mounted on the indicated panel, the corresponding signal about exceeding the permissible difference in the readings of any of the channels with the standard, which comes from a computer device connected to the measuring channels ( IVTM-7 / 8R-MK).

For water-graphite reactor plants, an additional unit 40 with a measuring channel is designed, the sensor of which monitors the integrity of the equipment inside the unit 41, where the reactor casing is located. Blocks 40 and 41 are interconnected by a bypass line, and block 40 with an electric communication control unit 39.

A technical find of the proposed system is the use of such a variable climatic component as relative air humidity (φ) to solve the complex problem of timely and accurate detection of coolant leakage in the 1st circuit of the AC and its flow rate. To solve this problem, several methods are used:

1. The method of comparative analysis. As part of the scheme, the number of measuring channels is one more than the number of controlled rooms. The air to the additional (reference) channel comes from a well-ventilated room in which there are no moisture sources, so the φ of this channel will be equal to the φ of the outdoor air, adjusted for temperature increase (T) ° C. All expanders are in one place and are powered from one source of cooling water, therefore, in the absence of a coolant leak, the readings T, φ along all channels, including the reference, will be the same. Alarm setpoint for exceeding φ is set to + 5% of the original. The value of φ varies significantly over the year, therefore, the alarm setpoint changes in the year at least 5-6 times.

When φ increases by 5% on any of the channels (except the reference one), an alarm is triggered, the operator compares the readings φ of the triggered channel with the φ of the reference channel. A synchronous increase in φ indicates an increase in φ of outdoor air, asynchronous increase indicates a coolant leak.

1.1. The flow rate of the coolant leak is determined by the formula:

(г/час),

(g / hour)

where d ₂ is the moisture content (g / kg) corresponding to the readings φ, T of the activated channel, is determined by the Id diagram of moist air (Fig. 8);

d ₁ - moisture content corresponding to the readings φ, T of the reference channel;

σ _in - air flow from the room (kg / h).

Since the computer is included in the IVTM-7 / 8R-MK device kit, its program includes an alarm triggering algorithm when the readings of any of the channels differ from the reference. This difference can be set to 2% and, therefore, the operational sensitivity of the CPT will be equal to 2%.

2. Seasonal differentiation of expander cooling modes. The sensitivity of CPT primarily depends on d outdoor air, the values of which vary from 0.5 to 16 g / kg during the year. The diagram shows that the lower T of the measured air, the higher the sensitivity of the system, but air can be cooled only to that T at which φ = 70-80% in order to have a margin for the system to operate when a leak occurs, therefore, depending on the season of the year A certain air cooling mode is required

2.1. Mode I (1st zone of the diagram), raw water with Т = 6 ± 1 ° С is used as a refrigerant.

The regimen is applied for 8 cold months of the year at Bilibino NPP and 6 months at Kola NPP.

2.2. Mode II (2nd zone of the diagram) - water cooling is not used, but the water in the cooling jacket of the expander remains and plays the role of a thermostabilizer, smoothing out daily fluctuations in ambient temperature. The daily air flow rate per channel is 1.5 kg, the volume of water in the expander is 0.7 kg, but remember that the heat capacity of the air is 4 times lower than the heat capacity of the water, so the remaining water is quite enough to smooth out the daily fluctuations of T. Therefore, the values of T in at any time of the day they will be very close to the average daily T and φ will not change during the day depending on T.

Mode II ¹ (2nd zone of the diagram) - use of process water with Т = 13-18 ° С as a coolant.

Mode II is used for 4 relatively warm months of the year at Bilibino NPP and 3 at Kola (excluding summer). Modes II and II ¹ can be used for 6 cold months for the speakers of the European part of Russia.

2.3. Mode III (3rd zone of the diagram) - lack of water cooling. Like mode II, the water in the expander acts as a thermostabilizer. Mode III differs from mode II of a higher T of the measured air, and the 3rd zone is in the highest part of the diagram. It is used for 6 months for speakers in the European part of Russia and for 3 summer months for Kola speakers. It should be noted that the division into modes, except for the Bilibino NPP, is very arbitrary and requires clarification after the trial operation of CPT at the NPP of Russia.

2.4. An ideal option for operating a CPT replacing the seasonal differentiation of modes and suitable for any speaker could be the option of using a cooling water heater operating in automatic mode. T of water would be maintained in such a way as to prevent the growth of φ above 70%. The controller circuit should be such that for φ = 65, 70 and more than 70% the controller requires “more”, and in all other cases, “less” until it is completely turned off.

3. Determine the sensitivity of CPT when working in different modes. Conventionally, we take the air flow of exhaust ventilation operating on the premises of the 1st circuit equal to 2000 kg / h. In this case, with a room volume of 1000 m ^{3, the} ventilation ratio will be 2, the CPT reaction (leak detection time after its appearance) is 30 minutes, and with a volume of 4000 m ³ , ventilation ratio is 0.5, and the SRT reaction is 2 hours.

The sensitivity of CPT is determined by the formula:

(г/час),

(g / hour)

where d ₂ is the change in moisture content corresponding to φ = 2%;

σ is the air flow from the room (kg / h).

The sensitivity at σ = 2000 kg / h will be: I mode - f = 280 g / h, II mode - 480 g / h, III mode - 800 g / h.

When determining the air flow rate of ventilation, you can use CPT, feeding a calibrated water flow rate to the nozzle and calculate the flow rate according to the formula:

(кг/час),

(kg / hour)

where Y is the calibrated water consumption per nozzle (3.6.10) kg / h;

Δd is the increment of moisture content caused by this flow (g / kg).

Since the instrument measures T and φ, it is easy to calculate d from the diagram.

4. Diagnostic method in the susceptible zone. It consists in determining the density of equipment by a multiple reduction (increase) in fan flow. The change in air flow is made by the gate valves. Consider an example: the volume of the room is 500 m ³ . Fan consumption - 2000 kg / h. Suppose a leak appeared in the equipment at a flow rate in the susceptible zone, for example, in the 1st mode - 140 g / h. Reduce consumption by 4 times to 500 kg / hour. The sensitivity of CPT will increase by the same amount and amount to 280: 4 = 70 g / hour. This means that when the consumption is reduced by 4 times, the device will show a change in relative humidity of 4%. If, with a multiple reduction in consumption (2, 4, 6 times), the device remains at its previous readings, the equipment can be considered dense. Such diagnostics should be carried out before the switchgear goes into repair, after decommissioning, periodically during operation at least 1 time in 3 months.

5. In equipment and pipelines of the 1st circuit, saturated steam, superheated water and steam-water mixture circulate under high overpressure and high T. In case of violation of the density of the equipment, even with leaks of several kilograms, almost all superheated water turns into steam and enters the room, from where through exhaust ventilation and a cleaning system into the ventilation pipe. Through the CPT pipeline with a diameter and thickness of 14 × 2 mm, cut into the duct to the control device, the air enters the expander and, passing through the device’s sensor, goes to the fan inlet. Passing through the pipeline with a nominal diameter (DN) of 10 mm in length from 10 to 40 m with a speed equal to 0.2 m / s, the air cools to T of the environment, and in the expander (air speed - 0.008 m / s) T of air decreases to T cooling water. Velocities of 0.2 and 0.008 m / s are much lower than air velocities during convection heat transfer; therefore, no preliminary gas-dynamic and thermotechnical calculations were performed, especially since the indicated velocities are not limiting, and can be further reduced by 2–3 times.

6. For water-graphite reactors, an additional channel is installed (Fig. 7) for monitoring the integrity of the equipment in a sealed reactor shell. This channel is powered on the bypass of the forced ventilation of the gas circuit, it works without a filter and water cooling. The alarm setpoint for growth is φ + 2%. Before entering the expander into the pipeline with a nominal diameter (DN) of 10 mm, a fitting with a plug (pos. 31, 32) is welded, which serves to check the device. The check is carried out as follows: the channel is turned off, the nozzle plug is removed, and 2-3 drops of water are dripped from the medical (eye) pipette into the pipeline. After that, the plug is put in place, the channel is connected, and the operability of the channel is determined by the response of the device.

7. It can be seen from paragraphs 2, 3 that the Bilibino NPP has an undeniable advantage over other NPPs in terms of the implementation of CPT. The station owes this advantage to the unique climatic conditions of its location. The average annual air T in the region is - 15 ° С. The moisture content (d) for 8 months is below 2 g / kg, and in the remaining 4 months it rises only to 8 g / kg. Externally, this is manifested in the fact that fog in winter (8 months of the year) falls out only at -48-50 ° С, and in summer, despite daily T drops reaching 20 ° С, there is neither dew nor drizzle. Within 8 months, T of raw water is 6 ± 1 ° C, which makes it possible to use it as an ideal refrigerant. Such ideal conditions for CPT allow you to work out a project for implementation at other nuclear power plants in Russia.

Claims (6)

1. The registration system of the coolant leaks of the first circuit of the reactor installations of a nuclear power plant, including a block of controlled rooms with equipment of the first circuit of the reactor installation, connected via exhaust ventilation ducts to a block of channels designed to measure the relative humidity in the controlled rooms, including a reference channel designed to measure the relative humidity of outdoor air in a room with measuring channels, while the sensors of the measuring channels are connected neny with a control unit for recording and comparing indicators of relative humidity in controlled rooms and a room with measuring channels, each of which is made in the form of an expander, on one end of which there is a pipe with filtering means connected to the air duct, and a flange is installed on the other end, designed to mount the sensor, while outside the expander there is a cooling chamber. 2. The system according to claim 1, which for a water-graphite reactor installation additionally includes a unit with a measuring channel located inside the reactor shell and an associated bypass forced ventilation line for monitoring the integrity of the equipment inside the specified shell, while the measuring channel sensor is connected to the control unit through electrical communication. 3. The system according to any one of claims 1 and 2, in which the sensors of the measuring channels of the monitored rooms are connected to a computer alarm means that is triggered by a difference in the readings of any of the measuring channels with the reference. 4. The system according to claim 2, in which the measuring channel, designed to monitor the integrity of the equipment inside the reactor shell, is made in the form of an expander, one end of which is connected to the bypass line of the forced ventilation system, equipped with a throttle at the inlet of the expander, and installed on the other end flange for mounting the sensor. 5. The system according to claim 1, in which the exhaust ventilation duct is equipped with an adjustable device for limiting the flow of air from a controlled room, made airtight. 6. The system according to any one of claims 1 and 2, which is equipped with means for testing, commissioning and routine checks of the measuring channels.

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