RU1836491C - Crevice corrosion protection method for steam generators of atomic power stations - Google Patents

Abstract

The invention relates to the field of nuclear energy, in particular, to "solving the reliability problem in the operation of steam generators of nuclear power plants with water power reactors. The purpose of the invention is to prevent deposits on the heating elements of the steam generator. The method includes introducing into the working medium an aqueous solution of a calcium compound selected from the group of calcium sulfate and calcium hydroxide and maintaining its relative concentration in the ratio C / Cn 0.1-0.25, where C is the true concentration of the compound in the working medium, Cn is the saturation concentration this compound in a working environment. In order to accelerate the crystallization of the calcium compound in the slots, during the start-up of the steam generator, calcium compounds with a concentration of 0.3-0.35 C / Cn are introduced and maintained until the steam generator starts to decrease in productivity, and then the concentration of the compound is reduced to 0.1-0 , 25. 1 s.p. crystals, 1 tab. (L C

Description

The invention relates to the field of nuclear energy, in particular, to solving the reliability problem in the operation of steam generators of nuclear power plants (NPPs) with water power reactors (WW ER).

The aim of the invention is to prevent deposits on heating elements of steam generators of nuclear power plants with water-cooled power reactors while eliminating crevice corrosion by filling the gaps with calcium compounds.

By appropriate selection of the relative concentration in the working medium of the steam generator of the calcium compound, conditions can be achieved under which

the calcium compound is deposited only in slots, and on heat exchanging pipes, even taking into account the presence of corrosion products on them, the soluble calcium compound will not crystallize.

The absence of gaps in the places of passage of heat transfer pipes through the walls of the collectors and / or spacer grids from the side of the second circuit of the steam generators of nuclear power plants with water-cooled power reactors as a result of their complete elimination by sealing calcium compounds during operation will stop the concentration of aggressive impurities in the marked locations to eliminate corrosion conditions and prevent the formation of

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cracks and thus to prevent emergencies at nuclear power plants. At the same time, the economic effect of underproduction of electricity due to simply a power unit and the protection of steam generators that fail, will amount to several tens of millions of rubles.

The essence of the product is that, in a method for protecting crevice generators of nuclear power plants from crevice corrosion, including introducing an aqueous solution of a calcium compound into the working medium, a calcium compound selected from the group of calcium sulfate and calcium hydroxide is introduced into the working medium and the relative concentration is maintained calcium compounds in a C / Cn ratio of 0.1-0.25, where c is the true concentration of the compound in the working medium, and Cn is the saturation concentration of the compound in the working medium. In addition, in order to accelerate the crystallization of the calcium compound in the slots, during the start-up of the steam generator, calcium compounds with a concentration of 0.3-0.35 C / Cn are introduced into the working medium and the indicated concentration is maintained until the beginning of the decrease in the productivity of the steam generator, and then the concentration is reduced compounds in the working medium up to 0.1-0.25,

The method is carried out as follows.

1.During operation:

1.1. An aqueous solution of a calcium sulfate or calcium hydroxide compound is introduced into the working medium of the steam generator and its concentration in the working medium of the steam generator is adjusted to C / C 0.10-0.25;

1.2. Maintain a relative concentration of C / Sn 0.10-0.25 over the entire period of operation,

2. When starting the steam generator:

2.1. An aqueous solution of a compound of calcium sulfate or calcium hydroxide is introduced and its concentration in the working medium of the steam generator is adjusted to C / CH 0.30-0.35;

2.2. Maintain this concentration until the start of a decrease in the productivity of the steam generator;

2.3. Reduce the relative concentration of the calcium compound in the form of a second circuit of the steam generator to C / Cu 0.10-0.25

and maintain this concentration throughout the entire period of operation.

Physical conditions arising in the places of passage of pipes and heating elements

the steam generator, depending on the concentration of the calcium compound in the working medium at various heat fluxes and different depths of the gaps, is described in the table.

An analysis of the data presented in the table shows that, with an average heat load of 50 kW / m and a relative concentration of calcium compounds in the working medium of less than 0.05, only slits longer than 30 mm are blocked (30 mm is usually the maximum gap length). At a relative concentration of 0.10 to 0.25, all slots are blocked in the real range of thermal loads from 20 to 80 kW / m2, there are no deposits on the pipes, the steam generator is able to work in all modes. A relative concentration of 0.30 can be considered threshold, since deposits can occur at this concentration. At a relative concentration of the chemical compound in water of 0.35, deposits appear on the heat exchanger tubes, all slots are completely blocked. At a relative concentration of more than 0.35, deposits appear that do not allow the steam generator to develop full power, the gaps are completely blocked.

Claims (2)

1. A method of protection against crevice corrosion of steam generators of nuclear power plants, comprising introducing an aqueous solution of a calcium compound into the working medium, characterized in that, in order to prevent deposits on the heating elements of the steam generator, a calcium compound selected from the group of calcium sulfate and hydroxide is introduced into the working medium , and maintain the relative concentration of the calcium compound in the ratio C / C 0.1-0.25, where C is the true concentration of the compound in the working medium, Cn is the saturation concentration of this compound in the working medium e. 2. The method according to p. 1, characterized in that, in order to accelerate the crystallization of the calcium compound in the slots, during the start-up of the steam generator, a calcium compound with a concentration C / C of 0.3-0.35 is introduced and the indicated concentration is maintained until the performance decreases steam generator, and then reduce the concentration of the compound in the working medium to 0.1-0.25. The saturation concentration of CaSCM in water at a pressure of 68 bar was taken at 26 mg / kg Sn; Saturation concentration of Ca (OH) a in water at a pressure of 68 bar was taken Sn 150 mg / kg