Device for controlling flow of water coolant in the first circuit channel of a nuclear reactor

 

The invention relates to channel nuclear reactors, in particular to a device for controlling flow of water coolant in the first circuit channel of a nuclear reactor RBMK series. The device controlling the flow of water coolant in the first circuit channel of a nuclear reactor that does not require contact with the fluid, based on registration spaced along the technological channel (TC) detectors changes the gamma activity of the isotope16N in the water-coolant due to radioactive decay of the isotope during the movement of water in TC between the spaced detectors. Control activity16N will be along the lines of gamma radiation with quantum energy for 7.12 MeV and 6.13 MeV, which will stand out from background radiation detector based on detection of coincidence of the pulses of the two counters of electrons separated by a sink for electrons with an energy of about 6 MeV. The structure of the device includes the electronic unit associated with the detectors of electric lines, allocating and recording the signals of the detectors, proportional to the activity16N in the coolant, and is able to calculate the flow of water in TC. The technical result is to increase the reliability of monitoring the safe operation. 1 Il.

The technical field to which the invention relates, channel nuclear reactors, in particular the reactors RBMK series.

Known technical solution, in which the first coolant circuit channel nuclear reactors RBMK is equipped with a system of control of water consumption in the technological channels (TC) on the basis of the ball flowmeters, each of which has a movable element (ball), built-in technological channel and washed with brine [1]. The reliability of the ball flowmeters insufficient due to losses during operation of the freedom of movement of the balls inside the TC. Replacement bulb in the flow channel of a nuclear reactor is connected with the need to break and re-restore the integrity of the LC - operation is a very important and difficult radioactivity of precipitation accumulated in the TC.

You know the invention [2] "Device for controlling the coolant flow in a nuclear reactor, in which the proposed system radiation monitoring fluid containing positional-driven gamma-ray sensors. A disadvantage of this device is the lack of decision on the selectivity of the gamma ray sensors to gamma radiation emanating from the LC and associated with what erom the loop reactor", on the basis of which you can create a device for controlling the coolant flow; in the invention it is proposed to use the detecting unit of gamma radiation of the heat carrier in the form of the ionization chamber, located along the TC. The invention [3] is similar, closest to the proposed invention, and is selected as a prototype. The disadvantage of the prototype [3] is an uncontrolled dependence of meter readings on the value of background gamma radiation, inevitably present in the room where the TC with the coolant of a nuclear reactor; this shortcoming is a consequence of the use of the prototype as a gamma radiation detector of the ionization chamber, a signal which is proportional to the total dose rate of gamma radiation in the place of its location, i.e. the signal of the ionization chamber cannot be divided into informative and background parts.

The technical result obtained by the proposed technical solution is to increase the reliability of the control flow of water coolant in the first coolant circuit channel of a nuclear reactor and the improvement of conditions of safe operation by eliminating the need of depressurization is asany technical result is achieved due to the fact, the device for controlling the flow of water coolant in the first circuit channel of a nuclear reactor contains two identical gamma radiation detector isotope16N placed near the technological channel of constant cross-section S, through which flows the water-carrier, activated in a nuclear reactor isotope16N, with the distance L from each other corresponding to the time of passage of water between the channel is not less than 1, and an electronic unit associated with the detectors of electric lines, allocating and recording the signals of the detectors, proportional to the activity16N in the coolant, and is able to calculate the water flow rate Q by the formula Q=0,693 SL(ln1/K2)-1, where Q is the water flow rate; S is the cross section of process channel; L - distance between the detectors;=7,1 with a half - life of the isotope16N; K1- signal detector closer to the reactor core; K2the signal detector is more remote from the active zone of the reactor; and each of the two identical detectors of gamma radiation isotope16N is formed by a pair (or several pairs) of the counters of electrons, between which is located the absorber electr, beryllium, carbon, aluminum), and R1<d,
where d is the thickness of the absorber of electrons;
R1run in the sink for electrons with energy E1greater energy quanta of gamma radiation at least most of the radioactive impurities in the coolant and radioactive fallout on the surface of the technological channel (for example, E1=5 MeV);
R2run in the sink for electrons with energy E2close , but at a lower energy quanta of gamma radiation isotope16N (for example, E2=5,5 MeV);
and an electronic controller associated with the detectors of electric lines, selects and registers the coincidence of the signals of the counters of each detector and the number of matches per unit of time taken for the signals To a1and K2detectors, proportional to the activity16N in the coolant.

The mentioned set of features necessary and sufficient for achieving technical results obtained during the implementation of the device.

The device in statics is shown on the drawing. It includes two gamma radiation detector 1, each of which consists of a pair (or several pairs) of counters 2 electrons, separated by a scavenger of electrons 3, and elektronniy from each other, the appropriate time for the passage of water between the channel is not less than 1 (technological channel 6 the structure of the device is not included). The electronic unit 4 is connected by a line of digital signals 7 workstation 8 operator device (highway 7 and station 8 the structure of the device are not included).

The operation of the device is as follows.

In water, flow rate which controls the device, while passing through the reactor core formed of radioactive gamma-emitting impurities. In particular, the interaction with neutrons in reactions15N(n)16N and16O(np)16N are formed in the water isotope16N with a half-life of=7.1 seconds and quantum energy1=7,12 MeV (7.0 per cent of the number of decays) and2=6.13 MeV (75% of the number of decays). This isotope is always present in TC when working nuclear reactor in the energy range power.

During the movement of water in TC between the spaced detectors activity of this isotope is changed according to the law of radioactive decay, which allows to calculate the water velocity and volume flow in the technological channel with constant cross-section between demaw and 6.13 MeV, which stand out from the background radiation detectors based on detection of coincidence of the pulses of a pair of counts of electrons separated by a sink for electrons with an energy of about 6 MeV.

Each of two identical detectors of gamma radiation isotope16N is formed by a pair (or several pairs) of the counters of electrons, between which is an absorber of electrons thickness d, and
R1<d,
where d is the thickness of the absorber of electrons;
R1run in the sink for electrons with energy E1greater energy quanta of gamma radiation at least most of the radioactive impurities in the coolant and radioactive fallout on the surface of the technological channel (for example, E1=5 MeV);
R2run in the sink for electrons with energy E2close , but at a lower energy quanta of gamma radiation isotope16N (for example, E2=5,5 MeV).

To reduce background load counters electron absorber of electrons between the counters is made from elements with low serial number on the periodic table (for example, beryllium, carbon, aluminum).

The electronic unit associated with the detectors of electric lines, highlights and belts are the signals K1and K2detectors, proportional to the activity16N in the coolant in the locations of the detectors.

The calculation of the volumetric flow rate of water electronic unit conducts by the formula
Q=0,693 SL(lnK1/K2)-1,
where Q is the volumetric flow rate of water;
S - section of technological channel;
L is the distance between the detectors;
=7,1 with a half - life of the isotope16N;
K1- signal detector closer to the reactor core;
K2the signal detector is more remote from the active zone of the reactor.

The electronic unit generates digital output signals and the backbone of the digital signal passes them to the workstation operator (highway digital signals and the workstation is part of a device not included).

The maximum value of the controlled volumetric flow rate Qmax(when water movement in TC between the spaced detectors for time 1) is the appropriate value To1/K2= 0,1; the minimum value of the controlled volumetric flow rate Qminreceived by the appropriate value of K1/K2=10. The ratio of these values of Qmax/Qmin=ln10/ln1,124.

For ustroystva, satisfying the conditions in the premises of the channel of a nuclear reactor and providing the ability to control water flow in a wide range.

The temperature in the room where TC RBMK reactor, can reach 300oWith; the exposure dose rate of background gamma radiation in this area may be of the order of 10 R/h Counters electrons, working in these conditions, are produced [4] (for example, types 13 GMS, GMS 14, SI BG). The same can be said of electric wires and cables (for example, types RC-2-41 TU 16. C-167-2000 or RC-2-71 TU 16-C.149-98), which can be used as communication lines between the detectors and the electronic unit of the device. The possibility of making electronic unit, allocating and registering the coincidence of the signals of the counters of each detector and the number of matches per unit of time, no doubt, because such devices are well known [5].

Sources of information
1. The Kremlin PP Flow meters and counters. M.: Mashinostroenie, 1987.

2. Rusyns C. F., Borisov, C. F. "a Device for controlling the coolant flow in a nuclear reactor". Patent 2100855, Appl. 03.11.95.

3. Ostapenko centuries "Meter speed tibary and systems. Management, monitoring, diagnostics. 2, 2000..

5. Aglintsev K. K. Dosimetry of ionizing radiation. M: State. ed. technical-theoretical literature, 1957.


Claims

Device for controlling flow of water coolant in the first circuit channel of a nuclear reactor, characterized in that it comprises two identical gamma radiation detector isotope16N placed near the technological channel of constant cross-section S, through which flows the water-carrier, activated in a nuclear reactor isotope16N, with the distance L from each other corresponding to the time of passage of water between the channel is not less than 1, and an electronic unit associated with the detectors of electric lines, allocating and recording the signals of the detectors, proportional to the activity16N in the coolant, and is able to calculate the water flow rate Q by the formula

Q=0,693 SL(lnK1/K2)-1,

where Q is the flow rate of water;

S - section of technological channel;

L is the distance between the detectors;

=7,1 with a half - life of the isotope16N;

K1- signal detector closer to the reactor core;

It is electoral gamma radiation isotope16N is formed by a pair (or several pairs) of the counters of electrons, between which is an absorber of electrons thickness d, which consists of elements with a low serial number on the periodic table (for example, beryllium, carbon, aluminum), and

R1< d < R2,

where d is the thickness of the absorber of electrons;

R1run in the sink for electrons with energy E1greater energy quanta of gamma radiation at least most of the radioactive impurities in the coolant and radioactive fallout on the surface of the technological channel (for example, E1=5 MeV);

R2run in the sink for electrons with energy E2,similar, but smaller energy quanta of gamma radiation isotope16N (for example, E2=5,5 MeV),

and an electronic controller associated with the detectors of electric lines, selects and registers the coincidence of the signals of the counters of each detector and the number of matches per unit of time taken for the signals K1and K2detectors, proportional to the activity16N in the coolant.

 

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