RU37571U1 - SYSTEM OF REGISTRATION OF LEAKS OF THE HEAT CARRIER OF THE 1st CIRCUIT OF REACTOR INSTALLATIONS OF NUCLEAR POWER PLANTS (СРТ) - Google Patents

Description

Heat carrier leak detection system

1st circuit of reactor installations of nuclear power plants (CPT)

This utility model can be used at all reactor facilities (RU) of nuclear power plants (NPP) 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 required for detecting with reasonable accuracy the location and flow rate of the primary coolant leak.

The proposed utility model has no analogues.

The objective of the utility model is to ensure the reliability of the nuclear power plant by timely detection of both the location and flow rate of the coolant leak with a possible depressurization of the first reactor circuit.

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 a room with measuring channels, with sensors

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measuring channels are connected to the unit for registration and comparison of 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 the 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 ratio (the ratio of the fan flow rate () to the volume of the room (m) 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 of the system will increase.

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 in relation to other cleaner" regarding radioactive contamination of 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 tight.

According to the proposed utility model, the number of measuring channels should be one unit larger 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.

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The CPT is based on the eight-channel PffiTM-7 / 8P-MK AOOT Practik-SC. 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 first circuit of the reactor installations of nuclear power plants includes registration of changes in the relative humidity in the room of the first 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 coolant of the 1st circuit is detected.

The utility model is illustrated by the drawing, where Fig. 1 schematically shows a schematic diagram of a CPT; in FIG. 2 - device channel circuit of figure 1 (in section); in Fig.Z - connection flange of the sensor; figure 4 is a section along aa in figure 3; in Fig.Z - 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.

the sensor receives air from a room with a relative humidity (f) equal to the relative humidity of the outdoor air, adjusted for a change in temperature (T) C.

Each measuring channel (pos. 1-3) consists of a sensor of device 4, which is used as an IVTM7M primary converter, a cooler expander 5, a 2-stage filter 6, and a DNMP-YuOUZ device, indicated by pos. 7, which can be connected to each channel, pipe 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 device PIBTM-7M (item 4 in figure 1) is designed to measure T, f air on each channel, is fixed in the hole 43 of the flange 12 (figure 2).

The cooler expander is made of a pipe 13 with a diameter and a thickness of 57x3.5 with a cooling jacket 14 (a pipe with a diameter and a thickness of 76x3) 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 nozzle 15 with a diameter and a thickness of 57x3.5, a length of 200 mm and a flange connection 16 with a nominal diameter (DN) of 50 mm, with a nominal pressure (Ru) of 10 kgf / cm. The pipe is filled with tightly rolled up Petryanova 17 fabric, 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 figL) 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); - control the pressure drop across the filters during operation.

Pipelines with fittings are made of alloy steel with a diameter and thickness of 14x2mm and 6x1.5mm and are designed for supplying, removing bleed air, cooling water, cooling air to room temperature, setting up the system, turning channels on and off, including emergency, to save sensors appliances when leakage occurs 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 CPT, the one shown in FIG. 5 nozzle, consisting of a funnel 21, a pipe 22 with a diameter and thickness of 5 mm, a pipe 23 with a diameter and thickness of 14x2 mm, a fitting with DuYmm (pos.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. 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.

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

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 cleaned 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, thus 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, a flow rate of 8 kg / h, with a deaerator with a pressure of 6 kgf / cm through a throttle washer with a hole with a diameter of 4 mm, a flow rate of 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 31c is inserted into the pipe 30 with a plug 32 for testing the channel. 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 humidity (f) to solve the complex problem of timely and accurate detection of coolant leakage on the 1st circuit of the AC and its flow rate. To solve this problem, several methods are used:

f 5 /

premises. The air to the additional (reference) channel comes from a well-ventilated room in which there are no sources of moisture, so the f of this channel will be equal to the f of the outdoor air, adjusted for an increase in temperature (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, f across all channels, including the reference, will be the same. The alarm setpoint for exceeding f is set to + 5% of the original. The value of f varies significantly over the course of the year, and therefore the alarm setpoint changes in the year at least 5-6 times.

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

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

From | di - dil X GB (g / h), where:

d2 - moisture content (g / kg), corresponding to the readings f, T of the activated channel, is determined by the I-d diagram of moist air (Fig. 8);

d is the moisture content corresponding to the readings f, T of the reference channel;

GB - 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%.

the values of which vary from 0.5 to 16 g / kg during the year. It can be seen from the diagram that the lower T of the measured air, the higher the sensitivity of the system, but air can only be cooled to T at which Φ 7080%, 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 mode is required air cooling.

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

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 thermostabilizer, smoothing out the daily fluctuations in the temperature of the surrounding air. The daily air flow rate per channel is 1.5 kg, the volume of water in the expander is 0.7 kg, but it should be remembered that the heat capacity of air is 4 times lower than the heat capacity of water, therefore, there is still enough water to smooth out the daily fluctuations of T. Therefore, the values T at any time of the day will be very close to the average daily T and av, depending on T, will not change during the day.

Mode II (2nd zone of the diagram) - the use of process water with a temperature of 13-18 ° C 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 can be used for 6 cold months for 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

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diagrams. 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 water would be maintained so as to prevent the growth of f above 70%. The regulator circuit should be such that with f 65, 70 and more than 70%, the regulator 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, when the volume of the room is 1000 m, the ventilation ratio will be 2, the CPT reaction (leak detection time after it appears) - ZOminut, and with the volume of 4000 m, the ventilation ratio - 0.5, the SRT reaction - 2 hours.

The sensitivity of CPT is determined by the formula:

f d2 X a (g / h), where:

d2 - change in moisture content corresponding to f - 2%;

a - air flow from the room (kg / h). The sensitivity at a 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:

(T - (kg / h), d

Y - calibrated water consumption per nozzle (3.6.10) kg / h;

Ad is the increment in moisture content caused by this flow (g / kg).

Since the instrument measures T and f, it is not difficult 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; The fan flow rate is 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 / h. 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 14x2 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 from 10 to 40 m long with a speed of 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

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reduced 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) to control 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 f + 2%. Before entering the expander into the pipeline with a nominal diameter (DN) of 10 mm, a fitting with a plug is welded in (pos. 31, 32) that serves to test 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.From paragraphs 2, 3 it is clear 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 T of air in the area is -. 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. For 8 months, T of raw water is equal, which allows you 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.

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Claims (7)

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 They are equipped with a control unit for recording and comparing indicators of relative humidity in controlled rooms and a room with measuring channels. 2. The system according to claim 1, characterized in that it further includes a casing of a water-graphite reactor connected by a forced ventilation bypass line to a measuring channel unit for monitoring the integrity of the equipment inside said casing, while the measuring channel sensor is connected to the control unit by electrical communication . 3. The system according to any one of claims 1 or 2, characterized in that in it the sensors of the measuring channels of the monitored rooms are connected to a computer alarm means that is triggered by the corresponding difference in the readings of any of the measuring channels with the reference. 4. The system according to claim 1, characterized in that 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, This cooling chamber is located outside the expander. 5. The system according to claim 2, characterized in that therein a measuring channel for a water-graphite reactor installation, designed to control 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 forced ventilation pipe provided at the inlet the expander with a throttle, and on the other end there is a flange designed for mounting the sensor. 6. The system according to claim 1, characterized in that the exhaust ventilation duct is provided with an adjustable device for limiting the air flow from the controlled room, which is sealed. 7. The system according to any one of claims 1 or 2, characterized in that it is equipped with means for testing, commissioning and routine checks of the measuring channels.