Granted Patent B2

US 9,334,579 · App. 14/065,728 · Granted May 10, 2016

Abstract

Claims (22)

1. A method for at least partially disrupting or removing deposits formed on a surface of a heat exchanger component in a nuclear steam supply system, comprising:

adding an effective amount of an elemental metal in solid form and water to a surface of the deposit;

applying an anodic or cathodic current locally to the surface of the deposit; and

following the adding and the applying steps, applying mechanical stress to the surface of the deposit,

wherein, the method is conducted at ambient temperature.

2. The method of claim 1 , wherein the deposits comprise one or more materials selected from the group consisting of oxide scale and corrosion products.

3. The method of claim 1 , wherein the elemental metal can be selected from the group consisting of metals with standard electrochemical potentials anodic to low alloy steel.

4. The method of claim 3 , wherein the electrochemical potential of the elemental metal can be more active than the potential of low alloy steel in the galvanic series of metals and alloys.

5. The method of claim 1 , wherein the elemental metal can be selected from the group consisting of zinc, aluminum, magnesium, beryllium, lithium, iron and mixtures thereof.

6. The method of claim 1 , wherein the elemental metal is zinc.

7. The method of claim 1 , wherein the elemental metal can be in a form selected from the group consisting of slab, granular, powder, colloidal, and combinations thereof.

8. The method of claim 7 , wherein the colloidal form can contain particles selected from the group consisting of micron-sized particles, nano-sized particles and combinations thereof.

9. The method of claim 1 , wherein the adding step further comprises a complexing agent selected from the group consisting of sequestering agent, chelating agent, dispersant, oxidizing agent, reducing agent and mixtures thereof.

10. The method of claim 1 , wherein the reductive current is supplied by a working electrode.

11. The method of claim 1 , wherein the mechanical stress comprises a hydro-mechanical flow.

12. The method of claim 1 , further comprising disassociating metal ions from the deposit, precipitating the metal ions and removing the precipitate by employing a process selected from the group consisting of filtration and ion exchange.

13. The method of claim 12 , further comprising one of purifying the disrupted deposit, transferring said deposit to a containment sump, adding said deposit to a radioactive or nonradioactive waste system and transporting said deposits to a location remote from the nuclear water reactor.

14. The method of claim 1 , wherein the elemental metal is present in a molar equivalent of from about 0.01 M to about 2.0 M.

15. The method of claim 9 , wherein the sequestering agent is selected from the group consisting of acids and salts of orthophosphates, polyphosphates, 1-hydroxyethylidene-1,1-diphosphonic acid, and mixtures thereof.

16. The method of claim 9 , wherein the chelating agent is selected from the group consisting of ethylenediamine tetraacetic acid, hydroxyethyl ethylenediamine triacetic acid, lauryl substituted ethylenediamine tetraacetic acid, polyaspartic acid, oxalic acid, glutamic acid diacetic acid, ethylenediamine-N,N′-disuccinic acid, gluconic acid, glucoheptonic acid, N,N′-ethylenebis-[2-(o-hydroxyphenyl)]-glycine, pyridine dicarboxcylic acid, nitrilotriacetic acid, acids and salts thereof, and mixtures.

17. The method of claim 1 , wherein the heat exchanger component is a steam generator in a pressurized water reactor.

18. The method of claim 1 , wherein the elemental metal is embedded in the deposits and in situ formation of gas mechanically disrupts the deposits.

Assignments (10)