Method to analyze economics of asset management solutions for nuclear steam generators

• US 7,637,653 B2
• Filed: 06/21/2006
• Issued: 12/29/2009
• Est. Priority Date: 06/21/2006
• Status: Active Grant

• Current Assignee: Areva NP Incorporated (AES Corporation)
• Original Assignee: Areva NP Incorporated (AES Corporation)
• Inventors: Pop, Mihai G. M., Colgan, Kent, Griffith, John Carroll
• Primary Examiner(s): Boswell; Beth V
• Assistant Examiner(s): Kardos; Neil R
• Application Number:
  US11/472,651
• Publication Number:
  US 20090292574A1
• Time in Patent Office: 1,287 Days
• Field of Search: 705/8, 374/7, 374/43, 374/44, 374/102, 374/141
• US Class Current: 374/7
• CPC Class Codes: F01K 13/02 Controlling, e.g. stopping or starting
• CPC Class Codes: F22B 37/002 specially adapted for nuclear steam generators, e.g. maintenance, repairing or inspecting equipment not otherwise provided for
• CPC Class Codes: G06Q 10/063 Operations research, analysis or management
• CPC Class Codes: G06Q 10/06375 Prediction of business process outcome or impact based on a proposed change
• CPC Class Codes: G06Q 10/20 Administration of product repair or maintenance
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]
• CPC Class Codes: Y02P 90/80 Management or planning

Abstract

A method to determine corrective actions of a nuclear steam generator, having the steps of modeling of steam generator tube and deposit heat transfer characteristics by analytically deriving specific deposit characteristics and descriptive model parameters, wherein the modeling uses historical thermodynamic data for an operating plant under evaluation, identifying a set of one of preventive and corrective maintenance alternatives to accomplish steam generator deposit objectives, determining through the modeling a power production impact of each of the set of one of preventative and corrective maintenance alternatives to determine an economic cost for each of the set of preventative and corrective maintenance alternatives, and initiating a maintenance alternative with a lowest economic cost as compared to the maintenance evaluation alternatives with higher economic costs.

Claims

1. A method to determine corrective actions of a steam generator of an operating nuclear power plant, comprising:

modeling heat transfer characteristics of deposits over the heating surface of a steam generator tubing by analytically deriving descriptive model parameters, the model parameters comprising the deposit thickness, δ

, the deposit porosity, ε

, the deposit copper content, Cu, the effective fraction, K, of the deposit full thickness conductive heat transfer resistance, which lies between the tubing and deposit steam channel, and the deposit tortuosity, τ

, wherein individual parameters δ

, ε

, Cu, K, and τ

evolve in time as a function of a B parameter as follows;

2. The method according to claim 1, further comprising determining an economic cost for the set of preventative and/or corrective maintenance alternatives for the steam generator based on the power production impact of the set of preventative and/or corrective maintenance alternatives for the steam generator wherein the maintenance alternative initiated on the steam generator has an economic cost less than the economic costs of the other identified maintenance alternatives.

3. The method according to claim 1, wherein the historical thermodynamic data is steam pressure in the steam generator under operating conditions, primary side hot and cold leg temperatures, in-service heat transfer tube surface area, and steam generator thermal power.

4. The method according to claim 1, wherein the empirical deposit measurement data are obtained through removal and testing of deposits from the steam generator tubing.

5. The method according to claim 4, wherein the deposit removal is accomplished through scraping and/or lancing the heating surface of the steam generator tubing.

6. The method according to claim 4, wherein the testing comprises determination of one or more of the deposit thickness δ

, the deposit porosity ε

, the deposit copper content Cu, the effective fraction K of the deposit full thickness conductive heat transfer resistance, which lies between the tubing and deposit steam channel, and the deposit tortuosity τ

.

7. The method according to any claim 4, wherein a chemical analysis of the flakes obtained from the steam generator tubing is accomplished to determine the deposit thermal resistance.

8. The method according to claim 2, wherein the step of determining an economic cost for the set of preventative and/or corrective maintenance alternatives comprises recalculating periodically the modeled deposit thermal resistance to account for planned maintenance activities or unanticipated changes in the plant operating behavior.

9. The method according to claim 1, wherein the maintenance alternatives comprise actions selected from the group consisting of chemical cleaning, upper bundle flush, enhanced upper bundle flush, and sludge lancing.

20. The method according to claim 1, wherein the modeling is performed on a computer.

21. The method according to claim 2, wherein the economic cost determination is based upon one of the net present worth, internal rate of return, and a payback period, and, optionally, is further based upon the cost of replacement power.

10. A method of maintaining a steam generator, the method comprising:

obtaining historic and/or current data for at least one of a steam generator deposit porosity, ε

, steam channel tortuosity, τ

, deposit thermal resistance, K, deposit copper content, Cu, and deposit thickness, δ

, for a steam generator or a steam generator of the same design;

calculating a B-base fouling factor, B, from the historic and/or current data and at least one of;

11. The method according to claim 10, wherein the maintenance alternative performed on the steam generator is selected from the group consisting of operating the steam generator for a time, t, before performing maintenance, operating the steam generator at reduced power, chemical cleaning, upper bundle flush, enhanced upper bundle flush, sludge lancing, and combinations thereof.

12. The method according to claim 10, further comprising predicting future power production levels using the calculated future evolution in time of at least one of the deposit porosity, steam channel tortuosity, deposit thermal resistance, deposit copper content, and deposit thickness.

13. The method according to claim 12, further comprising determining costs for replacement power.

14. The method according to claim 10, wherein the historic data comprises at least one of steam pressure in the nuclear steam generator under operating conditions, primary system hot and cold leg temperatures, in-service heat transfer tube surface area, and steam generator thermal power.

15. The method according to claim 10, further comprising obtaining and testing a deposit.

16. The method according to claim 15, further comprising determining one or more of the deposit thermal resistance, deposit thickness, deposit porosity, and tortuosity of a steam channel in the deposit layer.

17. The method according to claim 15, wherein the deposit is obtained by scraping and/or lancing a heating surface of steam generator tubing.

18. The method according to claim 15, wherein the B-base fouling factor is calculated from measurements taken from the deposit.

19. The method according to claim 10, further comprising determining remaining licensing life of the generator and/or generator changes from maintenance outages/modifications that affect corrosion susceptibility.

22. The method according to claim 10, wherein the calculations are performed on a computer.

23. The method according to claim 10, further comprising determining the maintenance alternative having the least economic cost;

and

performing the maintenance alternative having the least economic cost on the steam generator.

24. The method according to claim 23, wherein determining the economic cost comprises determining at least one of the net present worth, internal rate of return, and a payback period, and, optionally, further comprises determining the cost of replacement power.