CHEMICAL PROCESS FOR PRIMARY SYSTEM MATERIAL PASSIVATION DURING HOT FUNCTIONAL TESTING OF NUCLEAR POWER PLANTS
First Claim
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.
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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.
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Citations
15 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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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:
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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. - View Dependent Claims (14)
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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:
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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.
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Specification