RU32629U1 - Channel cooling circuit for a control and protection system for a nuclear uranium-graphite reactor - Google Patents

Description

CHANNEL COOLING CIRCUIT

NUCLEAR MANAGEMENT AND PROTECTION SYSTEMS

URANIUM-GRAPHITE REACTOR

The proposed utility model relates to the field of nuclear energy, in particular, to cooling the channels of the active zone of nuclear uranium-graphite reactors, and can be used to increase the safety level of RBMK reactors.

To ensure a given temperature mode of the channels of the control and protection system (CPS), fission chambers, sensors for controlling energy release, a reflector and high-speed emergency protection (BAS) for a nuclear uranium-graphite reactor, they are cooled with water, and the BAZ channels are cooled in film mode. To remove radiolytic gases (hydrogen, oxygen), BAZ channels are purged with nitrogen. The operating experience of power units with RBMK NPPs showed that purging the BAZ channels with nitrogen leads to the formation of nitric and nitrous acids and, as a result, to exceed the normalized pH values of cooling water and increase the corrosion of structural materials 1.

The closest analogue of the claimed utility model is the cooling circuit of the channels of the reactor control and protection system, including circulation pumps, heat exchangers, a nitrogen supply unit to the channels of high-speed emergency protection 2. The circuit is a forced-circulation circulating system.

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- the formation in the BAS channels of a significant amount of radiolytic acids (nitric and nitrous) and, as a result, the possibility of increasing the normalized pH values. Nitric and nitrous acids are formed due to radiation-chemical reactions of nitrogen dissolved in the water of BAZ channels with the products of water radiolysis: OH- radicals, hydrogen peroxide, oxygen (the concentration of H2O2 in the circuit reaches 8 mg / l, O2-10mg / l):

bon + N2 2HNO3 + 2H2 (1)

5 Н2О2 + N2 2HNO3 + 4Н2О (2)

5O2 + 2N2 + 2H2O 4NCO3 (3)

3O2 + 2N2 + 2H2O 4HNO2 (4)

-increase in corrosion of structural materials as a result of the formation of radiolytic acids;

-the need to reduce reactor power at pH below acceptable values;

-reduction of the filter cycle of the anion exchange filter due to sorption of nitrate and nitrite ions;

The problem solved by the utility model is to reduce the corrosive effects of the products of the radiolysis of the aqueous medium of the cooling circuit of the control system and are protected on structural materials.

The essence of the claimed technical solution lies in the fact that in the cooling circuit of the channels of the cooling system and the nuclear uranium-graphite reactor, which includes circulation pumps, heat exchangers, a nitrogen supply unit to the high-speed emergency protection channels, it is proposed that the cooling circuit be equipped with an input unit for the inhibitor of the formation of radiolytic acids in the coolant at

than it is proposed to use nitrogen compounds with a negative oxidation state, for example, hydroxylamine or hydrazine hydrate, or a mixture thereof, as an inhibitor.

The main essential distinguishing feature of the proposed utility model is the presence of an inhibitor of the process of formation of radiolytic acids in the input node circuit. In order to justify the conformity of the claimed feature with the criteria of novelty, the inventive step is as follows: The proposed utility model provides for the possibility of introducing an inhibitor (for example, hydroxylamine or hydrazine hydrate or a mixture thereof) into the coolant, which reduces the rate of formation of nitric and nitrous acids formed by reactions 1 - 4, and also neutralizes HNOs, HNO2. So, hydroxylamine (degree of nitrogen oxidation: -1), being a strong reducing agent, interacts with OH radicals, hydrogen peroxide, and oxygen according to the reactions:

2OH + 2NH2 OH N2 + 4H2O (5)

Н2О2 + 2NH2 ОН N2 + 6Н2О (6)

O2 + 4NH2-OH 2N2 + 3H2O (7)

Similarly, with OH radicals, hydrogen peroxide, oxygen interacts with hydrazine hydrate (nitrogen oxidation state: -2):

4OH + N2H4 Н2О N2 + 5Н2О (8) 2Н2О2 + N2H4 Н2О N2 + 5Н2О (9)

О2 + N2H4 Н2О N2 + ЗН2О (10)

Since the reaction rate (5-10) is much higher than the reaction rate (1-4), OH radicals, Н2О2, О2 are spent mainly on interaction with hydroxylamine or hydrazine hydrate, which avoids the formation of nitric and nitrous acids and significantly reduce stationary concentrations of hydrogen peroxide and oxygen in the circuit water. In the absence of oxygen and hydrogen peroxide, nitrogen dissolved in water reacts with hydrogen formed as a result of radiolysis of water by the reaction:

N2 + (11)

In addition, hydroxylamine, hydrazium hydrate, and ammonia neutralize the nitric acid formed in small amounts by reactions of 1–3.

NCO3 + N2H4 H2O N2H5 N3O3 + H2O (12) HNOs + NH2OH NH2- NO3 + Н2О (13) HNO3 + КЩОН NH4-NO3 + Н2О (14)

Due to the hydrolysis of nitric acid salts formed in reactions 1214, the pH in the loop is maintained at a level of 5-6.

The proposed technical solution is illustrated in graphic material. In FIG. 1 is a schematic diagram of the cooling circuit of the channels of the reactor control and protection system, consisting of pre-filled perlite filters 1, cation exchange filters 2, anion exchange filters 3, ion exchange traps 4, pumps 5, circulation tank 6, emergency tank 7, heat exchangers 8, pressure header 9, channel CPS 10, fishing 11, tank 12 with an inhibitor, for example

measures, hydroxylamine or hydrazine hydrite or a mixture thereof, metering pump 13, channels BAZ 14, node 15 supply of nitrogen.

The cooling of the channels is as follows. From the circulation tank 6, water is piped through the pump 5 to heat exchangers 8, where the industrial circuit is cooled by water. From the heat exchangers 8, water is supplied to the pressure header 9, from where it is distributed through channels 10, 14 and then enters the circulation tank 6. Bypass cleaning is provided to maintain the water quality standards of the circuit. Water is taken for purification through a pipeline cut into the water supply pipe from heat exchangers to the pressure header. The water of the circuit sequentially enters the perlite inlet filter 1, where oil and insoluble corrosion products of structural materials are cleaned, then cation exchange filters 2, anion exchange filters 3 are discharged into the circulation tank 6. Nitrogen enters the BAZ channels from the nitrogen supply unit 15. For supply a tank 12 is provided in the BAZ channels, for example, hydroxylamine or hydrazine hydrate or a mixture thereof, with an inhibitor dosed into the coolant of the circuit using pumps 13. The inhibitor is supplied at a water pH of 4.8 - 5.0, measuring The pH is carried out before the alluvial filters 1. When RP 6, the dosage of the inhibitor is stopped.

Thus, the use of the proposed technical solution can significantly reduce the formation of radiolytic acids in the cooling circuit of the CPS channels, maintain the pH at an acceptable level (4.5 - 6.5), increase the corrosion resistance of the structural materials of the circuit, increase the bypass filter, and avoid the need to reduce power the reactor.

List of used literature:

1.B. V. Gerasimov, A.I. Kasperovich, O.I. Martynova “Water regime of nuclear power plants, Moscow, Atomizdat, 1976

2.L.A. Belyanin, V.I. Lebedev, L.V., L.V. Shmakov, Yu.G. Skok “Safety of nuclear power plants in inventions, Moscow, Energoatomizdat, 1998

Claims (3)

1. The cooling circuit of the channels of the control and protection system of a nuclear uranium-graphite reactor, including circulation pumps, heat exchangers, a nitrogen supply unit to the high-speed emergency protection channels, characterized in that the cooling circuit contains an input unit for inhibiting the formation of radiolytic acids into the coolant. 2. The circuit according to claim 1, characterized in that nitrogen compounds with a negative oxidation state are used as an inhibitor. 3. The circuit according to claim 1 or 2, characterized in that as the nitrogen compounds with a negative oxidation state, gyroxylamine or hydrazine hydrate or a mixture thereof is used.