Method for cleaning and conditioning the water-steam circuit of a power plant, especially of a nuclear power plant
A method for cleaning and conditioning the water-steam circuit of a power plant, especially of a nuclear power plant, uses an amine as a film-forming agent. The amine is metered into the working medium circulating in the water-steam circuit. The film-forming agent forms a hydrophobic film on the surfaces of the circuit. During the process, the concentration of at least one impurity contained in the water and the concentration of the film-forming agent in at least in the feed water of the steam generator are measured and monitored. The concentration of the film-forming agent is varied, as needed, subject to the concentration of the impurity.
1. A method of cleaning and conditioning a water/steam circuit of a power plant, the method comprising:
adding an amine as film-forming agent to a work medium circulating in the water/steam circuit during power operation, to cause the film-forming agent to form a hydrophobic film on the surfaces of the water/steam circuit;
monitoring a concentration of at least one impurity contained in the work medium by directly measuring the at least one impurity during a duration of the method and monitoring a concentration of the film-forming agent in a steam generator feed water by directly measuring the concentration of the film-forming agent during a duration of the method;
modifying the concentration of the film-forming agent depending on the directly measured concentration of the at least one impurity; and
decreasing a metering rate of the film-forming agent in the case of an increase in the directly measured concentration of the at least one impurity.
2. The method according to claim 1 , which comprises measuring the concentration of the film-forming agent and the concentration of the at least one impurity at a plurality of measurement points distributed over the water/steam circuit.
3. The method according to claim 1 , which comprises interrupting a metering-in of the film-forming agent if the concentration of the at least one impurity approaches a threshold value.
4. The method according to claim 1 , wherein at least one measurement point is disposed in a dual-phase region of the water/steam circuit and at least one measurement point is disposed in a one-phase region of the water/steam circuit.
5. The method according to claim 1 , which comprises carrying out the method in a nuclear power plant.
6. The method according to claim 1 , which further comprises purging the water/steam circuit.
7. The method according to claim 6 , which comprises purging the water/steam circuit directly following an interruption of a metering-in of the film-forming agent.
8. The method according to claim 1 , which comprises using a monoamine with a hydrocarbyl comprising 8 to 22 carbon atoms as the film-forming agent.
9. The method according to claim 8 , wherein the film-forming agent is octadecylamine.
10. The method according to claim 1 , which comprises metering-in the film-forming agent with such a rate that the concentration of the film-forming agent in a liquid phase of the work medium does not exceed a concentration of 2 ppm.
11. The method according to claim 10 , wherein a maximum concentration of the film-forming agent of at most 1.5 ppm.
12. The method according to claim 10 , which comprises terminating the metering-in of the film-forming agent when the concentration of the film-form ing agent has reached a value of 1 ppm to 2 ppm.
13. The method according to claim 10 , which comprises terminating the metering-in of the film-forming agent when the concentration of the film-forming agent has reached a value of 1 ppm to 1.5 ppm.
14. The method according to claim 10 , which comprises terminating the metering-in of the film-forming agent when the concentration of the film-forming agent at a constant metering rate remains constant, averaged over time, at a plurality of measurement points in the water/steam circuit.
15. The method according to claim 14 , wherein an unchanging concentration of film-forming agent is measured at a plurality of points distributed over the water/steam circuit.