CHEMICAL PROCESS FOR PRIMARY SYSTEM MATERIAL PASSIVATION DURING HOT FUNCTIONAL TESTING OF NUCLEAR POWER PLANTS

• US 20160035442A1
• Filed: 07/29/2015
• Published: 02/04/2016
• 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.
• Granted Patent: US 10,453,576 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 nuclear power plant having a nuclear core and coolant water flowing through the primary system, comprising:

adding zinc to the coolant water during hot functional testing conducted prior to an initial loading of fuel in the nuclear core in an amount such that zinc concentration in the coolant water is from about 5 to about 300 ppb;

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 an alkaline pH from about 6.9 to about 7.4 at the operating temperature or from about 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 about 0.3 ppm to about 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 about 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 range consisting of at least about 4 cc/kg, from about 4 to about 50 cc/kg, from about 4 to about 15 cc/kg, from about 15 to about 30 cc/kg, and about 4.5 cc/kg.

11. The method of claim 1, wherein the adding of the zinc is initiated when the coolant water has a temperature of about 350°

F. or higher.

12. 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 about 350°

F. or higher.

13. 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:

initiating an alkaline-reducing phase, comprising;

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

adding zinc to the coolant water;

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;

adding an oxidizing agent to the coolant water.

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

15. 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:

initiating an alkaline-reducing phase, comprising;

adding to the coolant water zinc in an amount sufficient to provide a concentration from about 5 to about 300 ppb in the coolant water and at least one compound selected from the group consisting of hydroxide and hydrogen; and

increasing the coolant temperature to initiate a normal operating temperature plateau;

then initiating an acid-reducing phase, comprising;

adding boric acid to the coolant water at or near end of the operating temperature plateau; and

then initiating an acid-oxidizing phase, comprising;

adding an oxidizing agent to the coolant water.