CS274411B2 - Method of vver-440 type atomic power plants' blocks' hermetic spaces' repeated integral leakage tests with locating tower - Google Patents

Description

(57) During the measurement, the primary circuit of the reactor is filled with water, subjected to a pressure test and cooled by natural circulation. The pressure in the hermetic space is increased to a low value, preferably to 0.12 MPa, then the pressure is reduced. The operation is cyclically performed when a low pressure and a relative humidity of less than 70% is simultaneously reached, the cycle stops and the pressure is stabilized. The amount, temperature, charge air pressure as well as the pressure, temperature and relative humidity in the hermetic space are continuously measured, preferably for 6 to 12 hours.

CS 274 411 B2

The invention relates to a method by which the tightness of the hermetic spaces of VVER 440-type nuclear power plant blocks with a localization tower can be tested.

The state of the VVER 440 type nuclear power plant block with and after the fault location tower is one of the most important parameters of the nuclear power plant reliability. The tightness of the space in which the devices belonging to the primary circuit, or part of the space, are located, represents the last stage of the protection system in case of operational failures. This means that the environment is not disturbed in any operational failure of the technological system.

Due to the different concepts of the known technologies, it is not possible to use the known test methods for a block of this type. It is also not possible to use the testing of the blocks of the developed integral method of leak testing during commissioning with respect to radiation protection regulations and to the conditions in technology during operation.

According to Soviet regulations, these tests should be carried out at an initial pressure of 2.5 bar for 25 hours. The disadvantages of the tests are the high initial pressure and the long duration of the tests. '

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method suitable for repeated integral leak testing of the hermetic space of VVER 440-type nuclear power plant units with a localization tower.

The starting point of the invention is that it is possible to substantially reduce the shutdown time of the block, which is only possible when a larger part of the technological systems is out of operation and the temperature conditions within the hermetic space are favorable. It has been found that these conditions can be maintained even when the primary circuit is filled during natural circulation.

SUMMARY OF THE INVENTION The object of the present invention is accomplished by repeated integral leak tests of the hermetic spaces of VVER 440 type power plant units with a localization tower, which consists in subjecting the primary reactor circuit to pressure testing and filling with natural circulation during operation. the value, preferably up to 0.12 MPa, is then reduced, and the process is carried out cyclically until at a low pressure the humidity drops below 70 ° C, the cycle is interrupted and the pressure is stabilized, whereupon the quantity is continuously measured. the temperature and pressure of the charge air and the temperature, pressure and relative humidity of the air in the hermetic space, preferably for 6 to 12 hours.

The most important advantage of the method according to the invention is the reduction of the shutdown time of the test block.

The method according to the invention is explained by means of the functional dependencies shown in the graphs, in which Fig. 1 shows the leakage characteristic at the value ^P 1, "n ¹ " ^Z >

Fig. 2 shows the leakage characteristic if = 1.5;

Fig. 3 shows the leakage characteristic at - = 1.7;

^The peak in FIG. 4 is the leakage characteristic when atmospheric pressure.

= 2.5 where p ^ is the initial pressure and is

Example

In order to reduce the shutdown time of the block to the shortest possible time, it is advisable to carry out a control measurement at the lowest possible pressure. Consequently, it is necessary to establish a limit value which is applicable to such pressure and whose observance is ensured by the abovementioned criterion.

Oako's starting base is used to integrally measure block tightness values obtained during commissioning. Oak is known to have measured that leaks from the system lie within prescribed limits. Tests were performed at nominal initial pressure values of 0.25;

CS 274 411 B2

0.17; The leakage characteristics of the hermetic system were determined.

When selecting the initial pressure chosen for repeated measurements, it was desirable that the range of parameters did not fluctuate too much, which is also desirable in terms of evaluating the measurement results. Considering other aspects, the initial pressure value is particularly preferred.

ρ _χ = 0.12 MPa.

The leakage limit applicable to this pressure is extrapolated by the characteristic as described below.

The segments of the characteristic determined by the measurement are interlaced by a regression curve whose equation is characterized by terms representing isothermal laminar and isothermal turbulent flow at subsonic velocity. From the point of view of the invention, the nominal pressure curve section of 0.13 MPa is important, since it can calculate the leakage resulting from a pressure of 0.12 MPa, i.e. the value to be referred to as the limit value.

After deduction for the approximation function fd ² LP ^{2 L r} K, 1 1 _L RT

(1) + f

where

G is the leakage in kg / s,?

F is the leak section in m, d is the average hydraulic diameter of the slots in m, is the average slot length in m, p is the hermetic system pressure in N / m,

P _k is the atmospheric pressure, ie the air pressure in N / m,

R is the gas constant at 3 / kgK,

T is the average temperature in the hermetic space in ° K, is the flow friction constant (Nikuradze), is the dynamic air viscosity in kg / ms,

L is the laminar index,

N is a turbulent index (Nikuradze).

can be underlined by measured sections of pike

When using the least squares method, the following functions:

G

* ( ) ² - 1 + N 2 P • - 1 • Pk ^p K

1/2 (1).

The values of the constants L and N are then determined during the regression. The leak recalculation can be performed as follows by using the analytical representation of the individual sections of the characteristic obtained by correlation (2):

^l sh 8.64. 10 ⁶ -f ¹ P2 Pl - P2 where ^L SH Yippee gross value average M Yippee mass air closed 1 Yippee index beginning measurement a 2 Yippee index end of measurement.

% leakage in% / day in hermetic space in kg,

dp including (3) SUZs,

The p ₂ value can be determined by measuring block tightness using a regression correlation, po 3

CS 274 411 B2 describing the pressure drop in space versus time assuming different measurement times. As a result of the calculations, the following relation arises:

^Lsh = K. ^Pl ΔΓ ^{+ K} 2 ^p l ΔΤ ΌMT (O, ^p k Pk Pk ^p K

where

Ρκ is the atmospheric pressure, ie the air pressure in bars is the length of the leak measurement in hours.

even when determining the average value of the default parameters for percent leakage, this relationship differs.

The above generalized relationship allows ratios to vary from ratios when measured

K values ^ρ ι -ΔΤ and K 2 ^p l ^p K p ₂

are given in (1) to (4).

The leakage value defined by formula (4) reflects the state of the hermetic system during integral tests of block I. As already mentioned, this value is more favorable than the allowable value, that is, the leaks are smaller. It is therefore advantageous for the repeated measurements to be carried out under reduced pressure to be set as a limit value. This reasoning is motivated both by the described approach using computational methods, by extrapolation, but also by the changed ratios during repeated tests, when, for example, the localization tower cannot be freed from the water charge, which could lead to an increase in measurement error.

It should also be mentioned that it is possible to approximately estimate the leakage value, which will be at a higher pressure, based on the measured value for 0.2 MPa using Figures 2, 3, 4. The conversion is done as follows:

^(L S ' ^P 1 ^(L SH ⁾ p ₁ (L where ^(L S ⁾ p ₁ value escape ^(l sh ⁾ p ₁ threshold ^(L S ⁾ p ₁ value escape ^(L SH ⁵ Pl value escape

SH = 0.12 ^(L s> _Pl = ° · ¹² (5) is the leakage value at initial pressure ρ _η = 0,12 MPa from correlation (4) at 0,12% / d.

Based on the above, an initial pressure level for retesting of 0.12 kPa is preferred. Since the structural strength requirements do not require this, it is not necessary to perform an integral leak test at the pressure value to which the space is dimensioned every 5 years.

At the proposed pressure level, the test duration, including the preparatory technological work, is 24 hours.

Furthermore, it is necessary to determine when it is advisable to perform repeated leak tests at the time the unit is shut down. During unit shutdown, repeat testing should be performed after the revision.

CS 274 411 B2

It is necessary to determine the time at which the temperature conditions in the hermetic space are favorable, most technological systems are out of order and at which the regulations regarding protection against invisible radiation can be best observed.

The above conditions can be fulfilled during commissioning of the unit after a pressure test at 0.4 MPa when the primary circuit is filled and the refrigerant circulation during operation.

Technological systems need to be reset.

The initial state of technological systems belonging to the primary circuit is as follows.

In the reactor equipment and reactor shaft space, the reactor is assembled, charged and vented. Check the connection between the rods and the drives and the torque of the drive. The upper block service platform and thermal insulation are located at appropriate locations. The actuator position sensors, the temperature sensors inside the pressure vessel and the sensors for measuring the neutron flux or the metering orifice are connected. All pipes in the chambers of the cooling ring are installed. All connectors related to reactor temperature and neutron flux measurement, as well as position indication connectors and power connectors are plugged into the appropriate sockets. The leak test of the primary circuit at a pressure of 0.4 MPa is successfully completed. The passages between the reactor shaft and the surrounding area are closed by hermetic elements and placed in their places. The protective bell is placed on the reactor shaft and sealed. The reactor space and the well number 1 are emptied into operating condition and the system for checking the tightness of the reactor space and the well number 1 is removed.

The primary circuit piping is filled with cooling, vented, two loops participate in natural circulation.

The main circulation pumps are filled with refrigerant, vented and disconnected from the power supply.

Both the primary and secondary side of the steam generators are refrigerated, two of which will participate in natural circulation.

The volume compensators are filled with refrigerant and vented. Volume compensator heaters disconnected.

The primary circuit refrigerant cleaning system is filled with refrigerant and process charge and is vented. The first electric fitting after the aftercooler is closed - first branch, first electric fitting after the filter - first branch, first electric fitting after the resin reservoir - first branch, first electric fitting after the aftercooler - second branch, first electric fitting after filters - second branch and first electric fitting behind the resin reservoir - second, branch.

Pipes located in the hermetic space of the main circulation pump oil management system and contamination reservoir, the intersection oil of the main circulation pump lubrication system are closed.

The chemical treatment system is emptied. In the closed state, there are hermetic piping fittings facing the purge system of the primary circuit and electrical fittings located next to the hermetic fittings and manually closing piping fittings leading to the ventilation recirculation center.

The cooling intermediate circuit for the main circulation pump lubrication system is filled. The electric fitting in the preliminary branch in the wall of the hermetic space and the two electric fitting in the return branch are closed.

The cooling intermediate circuit of the actuators is filled. The hermetic fittings of the system are closed. The cooling system of the warehouse and the intermediate fuel storage are filled. The hermetic fittings of the system are closed.

The high pressure emergency core cooling system is in operating condition with respect to mechanical, electrical and control parts. The hermetic fittings of the system are closed.

The accumulators are filled up to the nominal level and are separated from the primary circuit5

CS 274 411 B2 with electric gate valves.

The low pressure emergency core cooling system is in operational condition in terms of mechanical, electrical and control parts. The hermetic fittings of the system, as well as the electrical fittings of the system on the supply lines to and between the boxes and heat exchangers of the emergency cooling system are closed.

The system for reducing the pressure of the hermetic space is in operation state in terms of mechanical and electrical as well as control parts.

The hermetic space is filled with compressed air through the third system pipe. The hermetic fittings of both operating systems are closed. The hermetic fittings of the third system are open during the compressed air filling, while the first shut-off valves of the piping upstream and downstream of the pump, which are pressurized during the filling, as well as the main line valves transmitting pressure and weight ratio impulses are closed.

The control system for water and boron replenishment is in working order. In the primary circuit, the pressure, preferably 4 to 5 bar, is maintained by means of pumps which evacuate the coolant via the pressure collector of the auxiliary pumps. The corresponding valves must be opened during possible refilling.

The clean condensate system is operating. The hermetic fittings of the system are closed.

Nitrogen management is in working order. The hermetic fittings of the system are closed. Valves located immediately on both sides of the hermetic wall that close the pipeline passing through the hermetic wall, which includes the normal mode fittings instead of the hermetic fittings, are also closed.

The hydrogen combustion and gas purification system is also in operation. The hermetic fittings of the system are closed.

The high pressure sampling system is in working order. The hermetic fittings of the system as well as the electrically operated fittings therein are closed. Sampling, which is prescribed by the relevant regulations, can be taken from the hermetic space during filling or emptying.

The organized leakage system is in operational condition. The hermetic fittings of the system are closed. The special sewer system is in operation and the hermetic fittings of the system are closed. The steam generator blowdown system is in operating condition. The hermetic fittings of the system are closed.

The tanks of the system for locating the accident are filled up to the nominal level with pine water in the prescribed concentration. Tank partitions are open. The hermetic fittings of the system are closed.

The emergency water cooling system is in operation. The heat exchangers, which are located in the hermetic space and which are cooled by the water of the safety system, are located under the pressure exerted by the safety water cooling pumps by closing the outlet fittings, thereby protecting the device against any damage caused by water expansion .

The high-pressure pneumatic system is in the operating state under the nominal pressure and ensures the closed state of the hermetic fittings.

Dosimetric system in operation. The sampling lines are closed by appropriate solenoid valves. In exceptional cases, the integral leak tests may be interrupted and the appropriate automatic dosimetry system valves may be opened to actuate the dosimetry system.

The cooling water system is in working order. Heat exchangers located in the hermetic space must be pressurized by the respective pumps, so that the outlet fittings are

CS 274 411 B2 closed. It is strictly forbidden to enclose water in heat exchangers!

The initial state of the technological systems in the secondary circuit is as follows.

The main steam collectors are according to the operating instructions of the system in a state providing cooling of the reactor by means of two steam generators. The valves are set according to the relevant sections of the operating instructions.

The cooling system is in operation and participates in the reactor cooling. The valves are set according to the relevant operating instructions.

The steam generator power supply system is in a state corresponding to the relevant instructions in the operating instructions and provides cooling of the reactor by means of two steam generators.

The hot water system fittings in the main operating building are closed inside the hermetic space. The status of the heating water system is not determined. The fire extinguishing system is in working order.

The low-pressure pneumatic system is in operation during leak tests, the space is filled with lines designed to fill the hermetic space. The following quality requirements are imposed on the charge air:

The temperature should be 20-25 ° C and the oil content should be less than 5 mg / m ³ .

The default state of ventilation systems and equipment is as follows. The hermetic space recirculation purification system fans are separated as indicated, hermetic closures in front of and behind the filters are open. In the operating pressure system of the hermetic space, the hermetic fittings of the system are closed.

The passages through the hermetic wall of the hermetic space maintenance system are closed by hermetic closures.

Hermetic fittings of hermetic space suction maintenance system are closed ·

The default state of the control devices is as follows.

The computer system for block control is in operational condition except for those measurements that were intentionally turned off before leak measurement. The computational system is in operational condition due to sensing and evaluation of hermetic space tightness measurement results.

High sensitivity pressure gauges should be discarded prior to measurement, as they may be damaged during testing.

The initial state of electrical equipment is as follows.

During the test, the hermetic space recirculation cleaning system ventilators and the hermetic space ventilation system ventilators should be disconnected. Furthermore, the heating elements of the circulation compensator and the main circulation pump are disconnected.

The state of the hermetic bulkhead elements is as follows.

The mounting openings opened during maintenance should be placed in their original positions according to plan and local tightness checks performed.

If other elements that hermetically hermetically seal the room have been repaired or modified during maintenance, they should also be checked for leaks.

In order to set up the measuring system, the results of the measurement of supply air temperature, supply air quantity, supply air pressure, hermetic space pressure, hermetic space temperature at 61 locations using permanently placed instruments and humidity shall be available for repeated integral leak tests. of air in the hermetic space, measured at 10 locations using permanently placed instruments, the measurement results are evaluated by a pre-prepared program.

After the preparatory work described above, the measurement is carried out as follows.

CS 274 411 B2

Claims (1)

The technological equipment and systems are reset. The start of the test must be allowed. The low-pressure compressor station for filling the hermetic space is in operation. With the approval of the head of the leak test, the compressors of the low-pressure system are switched on, filling of the hermetic space is activated and is carried out up to a pressure of 0.12 MPa. The pressure in the hermetic space is measured using a measuring system. After reaching a pressure of 0.12 MPa in the hermetic space, the pressure is reduced back to atmospheric pressure and the process is repeated until the relative air humidity of the hermetic space falls below 70%. If the pressure in the hermetic space is 0.12 MPa and the relative humidity of the air is not higher than 70%, the pressure in the hermetic space is stabilized. The pressure in the hermetic space can only be considered stable if, at 0.12 MPa, the difference between two consecutive measurements is at most 2%. After stabilizing the pressure in the hermetic space, it is necessary to start the leak measurement from the hermetic space. The measurement is performed for 6 to 12 hours. If the measurement results in a positive result, the air is discharged from the hermetic space. If the leakage exceeds the permissible value based on the evaluated measurement results, then the pressure in the hermetic space must be repeatedly increased to 0.12 MPa and the outer hermetic envelope and the elements in the hermetic envelope must be checked for faults. SUMMARY OF THE INVENTION Method of repeated integral leak tests of hermetic spaces of VVER 440 type power plant units with localization tower, characterized in that the primary reactor circuit is subjected to a pressure test and filled with natural circulation during operation, the pressure of the hermetic space is increased to a low value, e.g. The pressure is then reduced and the process is carried out cyclically until, at low pressure, the humidity drops below 70% at the same time, when the cycle is interrupted and the pressure stabilizes, whereupon the quantity, temperature and pressure of the charge air and temperature are continuously measured. the pressure and relative humidity of the air in the hermetic space, for example for 6 to 12 hours. 4 drawings CS 274 411 B2 Giant. 1 CS 274 411 B2 Κ) Giant. 2 CS 274 411 B2