Method for dismantling a steam generator or heat exchanger, in particular a steam generator or heat exchanger of a nuclear power plant

Patent metadata

Field	Value
Publication number	US-11328828-B2
Application number	US-201716344917-A
Country	US
Kind code	B2
Filing date	Nov 21, 2017
Priority date	Nov 22, 2016
Publication date	May 10, 2022
Grant date	May 10, 2022

Abstract

A method for dismantling a steam generator or heat exchanger, such as found in nuclear power plants, which steam generator or heat exchanger includes a plurality of primary circuit tubes with a contaminated inner surface and wherein one or more tubes are sealed with a plug at both end is provided, the method comprisinga) opening one or both ends of each sealed tube by creating an opening in or removing, the plug (13);b) introducing a viscous polymer to cure inside the tube wherein the polymer fills the tube across the full tube cross-section at least at the tube ends, immobilizing contaminations in the filled portion inside the tube (11);c) curing the polymer, then detaching the tubes with cured polymer the detached tubes being sealed by the polymerd) sorting out the detached tubes with polymer.

First claim

The invention claimed is:

1. A method for dismantling a steam generator or heat exchanger, said steam generator or heat exchanger including a plurality of primary circuit tubes having an interior with a contaminated inner tube surface, wherein one or more of said tubes are sealed with a plug at both tube ends, the method comprising the steps of:
a) opening one or both ends of each sealed tube by creating an opening in the respective plug or by removing the respective plug;
b) introducing a viscous polymer which will cure inside the tube into the initially sealed and now opened tube or tubes, said polymer filling the tube across the full tube cross-section at least in a region of the tube ends and immobilizing contaminations in the filled portion inside the tube;
c) curing the polymer, then detaching the tubes provided with the polymer, the detached tubes being sealed by the cured polymer;
d) sorting out the detached tubes provided with the polymer.

2. The method according to claim 1 , characterized in that the viscous polymer is a cross-linking polymer which performs cross-linking through polyaddition and comprises, a silicone and/or polyurethane and/or epoxy resin.

3. The method according to claim 1 , characterized in that the interior of the tube is filled completely with the polymer, or the interior of the tube is filled with the polymer in a region from each tube end up to 0.5 meters beyond a tube sheet.

4. The method according to claim 1 , characterized in that the polymer is introduced using one or more lines, wherein a line is inserted into the tube through an opened tube end or a respective line is inserted through each respective opened tube end of a tube.

5. The method according to claim 4 , characterized in that the tubes are U-shaped tubes both ends of which end in a tube sheet, wherein a line is inserted through one of the opened tube ends and is then led to the turning point of the U-shaped tube, and wherein the polymer is then injected into the tube through the line, while the line is being retracted from the tube until the interior of the corresponding half of the tube is filled with polymer.

6. The method according to claim 4 , characterized in that the tubes are U-shaped tubes both ends of which end in a tube sheet, wherein a line is inserted into the tube through one of the opened tube ends and is then led into the tube as far as about 0.5 meters beyond the tube sheet, and wherein the polymer is then injected into the tube through the line, while the line is being retracted from the tube until the corresponding portion of the tube is filled with polymer.

7. The method according to claim 5 , characterized in that simultaneously with, or subsequently to, the injection of the polymer into the corresponding half of the U-shaped tube, the second half is filled with polymer through another opened tube end in a like manner.

8. The method according to claim 1 , characterized in that prior to opening the sealed tubes, all tubes which are not provided with plugs are decontaminated, through mechanical or chemical cleaning processes.

9. The method according to claim 1 , characterized in that the openings in the plugs are created by drilling.

10. The method according to claim 1 , characterized in that the detaching of the tubes provided with the polymer also involves detaching the open tubes which are not provided with plugs and subsequently sorting out the tubes provided with polymer.

11. The method according to claim 1 , characterized in that the tubes provided with polymer and/or the open tubes not provided with plugs are detached directly at or near a tube sheet or at the level of a tube sheet, said detaching being performed along a provided separation line (A).

12. The method according to claim 3 , characterized in that the tubes completely filled with polymer are segmented into multiple pieces, said segmenting being performed through cutting and/or sawing and/or thermal separation processes.

13. The method according to claim 1 , characterized in that the detached and sorted tubes provided with the polymer are treated and/or disposed of as radioactive waste, and/or the open tubes not provided with plugs are treated and/or disposed of as less radioactive waste or non-radioactive waste after dismantling.

14. The method according to claim 1 wherein the steam generator or heat exchanger is a steam generator or heat exchanger of a nuclear power plant.

15. The method according to claim 6 , characterized in that simultaneously with, or subsequently to, the injection of the polymer into the corresponding portion of the U-shaped tube, the second portion of the tube is filled with polymer through the second opened tube end in a like manner.

16. The method according to claim 8 characterized in that prior to opening the sealed tubes, all tubes which are not provided with plugs are decontaminated through abrasive processes or through scavenging processes using solvents.

17. The method according to claim 9 , characterized in that the openings in the plugs are created by a two-stage drilling process to avoid loose pieces.

18. The method according to claim 11 , characterized in that the tubes provided with polymer and/or the open tubes not provided with plugs are detached directly at or near a tube sheet or at the level of a tube sheet by sawing.

19. The method according to claim 11 , characterized in that the provided separation line (A) is orthogonal to the vertically extending tubes.

20. The method according to claim 3 , characterized in that the tubes completely filled with polymer are segmented into multiple pieces after detachment.

Assignees

• Framatome Gmbh

Inventors

• Beck Jens
• Kraemer Georg
• Gerner Peter

Classifications

• G21D1/006 Primary

  primary side of steam generators (secondary side of steam generators F22B1/00, F22B35/00 or F22B37/00) · CPC title

• G21F9/307 Primary

  in polymeric matrix, e.g. resins, tars · CPC title

• F28F2265/18

  for removing contaminants, e.g. for degassing · CPC title

• Y02E30/00

  Energy generation of nuclear origin · CPC title

• G21F9/28 Primary

  Treating solids · CPC title