Chemical process for primary system material passivation during hot functional testing of nuclear power plants

• US 10,453,576 B2
• Filed: 07/29/2015
• Issued: 10/22/2019
• Est. Priority Date: 07/30/2014
• Status: Active Grant

• Current Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Devito, Rachel L., Mazzoccoli, Jason P., Silva, Edward J., Buckley, Deborah J., Jacko, Richard J., Byers, William A.
• Primary Examiner(s): Garner, Lily C
• Application Number:
  US14/812,051
• Publication Number:
  US 20160035442A1
• Time in Patent Office: 1,546 Days
• CPC Class Codes: C23F 11/18 using inorganic inhibitors
• CPC Class Codes: C23F 11/187 Mixtures of inorganic inhibitors
• CPC Class Codes: G21C 17/0225 Chemical surface treatment, e.g. corrosion corrosion prevention in presence of water from scale removal or by modification of the properties of the liquid C02F5/00; inhibiting corrosion by adding corrosion inhibitors C23F11/00
• CPC Class Codes: G21C 21/00 Apparatus or processes specially adapted to the manufacture of reactors or parts thereof in general section B, e.g. B23
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

The present invention relates to a pre-core hot functional testing (HFT) preconditioning process, which includes the introduction of chemical additives, e.g., zinc, into coolant water that circulates through the primary system of a new nuclear power plant, at various temperatures. The chemical additives contact the primary system surfaces, which results in the formation of a protective zinc-containing oxide film on the fresh surfaces to control corrosion release and deposition during subsequent normal operation of the nuclear power plant. The method includes a series of three chemistry phases to optimize the passivation process: 1) an alkaline-reducing phase, 2) an acid-reducing phase and 3) an acid-oxidizing phase.

Claims

1. A method of passivating a metal surface in a primary system of a new nuclear power plant having a nuclear core and coolant water flowing through the primary system, comprising:

heating the primary system to a simulated normal operating temperature prior to an initial loading of fuel in the nuclear core;

initiating an addition of zinc to the coolant water at a temperature greater than or equal to about 350°

F. prior to reaching the simulated normal operating temperature;

achieving a target zinc concentration in the coolant water from greater than 40 to 300 ppb at the simulated normal operating temperature;

conducting hot functional testing in the primary system at the target zinc concentration and the simulated normal operating temperature;

allowing the zinc to contact the metal surface in the primary system; and

forming an initial zinc-containing oxide film on the metal surface.

2. The method of claim 1, wherein the zinc is added in the form of zinc acetate.

3. The method of claim 1, further comprising adding base to the coolant water.

4. The method of claim 3, wherein the base is selected from the group consisting of lithium hydroxide, potassium hydroxide and mixtures thereof.

5. The method of claim 4, wherein the lithium hydroxide has a concentration sufficient for the coolant water to have a pH from 6.9 to 7.4 at the operating temperature or from 9.5 to 10.1 at 25°

C.

6. The method of claim 5, wherein the concentration of lithium in the coolant water is from 0.3 ppm to 2.0 ppm.

7. The method of claim 3, further comprising adding boric acid to the coolant water.

8. The method of claim 7, wherein the boric acid is added in an amount to such that there is a concentration of 100 ppm boron or less.

9. The method of claim 3, further comprising adding hydrogen.

10. The method of claim 9, wherein a concentration of the hydrogen in the coolant water is selected from a value or a range consisting of at least 4 cc/kg, from 4 to 50 cc/kg, from 4 to 15 cc/kg, from 15 to 30 cc/kg, and 4.5 cc/kg.

11. The method of claim 9, wherein the adding of the zinc, the lithium hydroxide and the hydrogen is initiated when the coolant water has a temperature of 350°

F. or higher and less than the simulated normal operating temperature of the coolant water.

12. A method for passivating a metal surface in a primary system of a new nuclear power plant during pre-core hot functional testing, the nuclear power plant having a nuclear core and coolant water flowing through the primary system, comprising:

heating the primary system to a simulated normal operating temperature prior to an initial loading of fuel in the nuclear core;

achieving an alkaline-reducing phase, comprising;

adding hydroxide in an amount sufficient to maintain the coolant water at an alkaline pH;

initiating an addition of zinc to the coolant water at a temperature greater than or equal to about 350°

F. prior to reaching the simulated normal operating temperature;

achieving a target zinc concentration in the coolant water from greater than 40 to 300 ppb at the simulated normal operating temperature;

conducting the pre-core hot functional testing at the target zinc concentration and the simulated normal operating temperature;

allowing the zinc to contact the metal surface in the primary system; and

forming a zinc-containing oxide film on the metal surface;

then initiating an acid-reducing phase, comprising;

borating the coolant water; and

then initiating an acid-oxidizing phase, comprising;

removing hydrogen from the coolant water.

13. The method of claim 12, further comprising adding an oxygen scavenger to the coolant water prior to initiating the alkaline-reducing phase.

14. A method of controlling the addition of zinc into coolant water flowing through a primary system and a nuclear core of a nuclear power plant during a preconditioning prior to an initial fuel load and normal power operation, comprising:

heating the primary system to a simulated normal operating temperature prior to an initial loading of fuel in the nuclear core;

achieving an alkaline-reducing phase, comprising;

initiating an addition of zinc, hydroxide and hydrogen to the coolant water at a temperature greater than or equal to about 350°

F. prior to reaching the simulated normal operating temperature;

achieving a target zinc concentration from greater than 40 to 300 ppb in the coolant water at the simulated normal operating temperature;

establishing a plateau at the simulated normal operating temperature; and

conducting the pre-core hot functional testing at the target zinc concentration during the plateau;

initiating an acid-reducing phase to simulate a plant shutdown chemistry condition, comprising;

adding boric acid to the coolant water; and

initiating an acid-oxidizing phase, comprising;

removing hydrogen from the coolant water.