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An ASTM standard now in development aims to bridge the critical gap between today’s coating technology and yesterday’s aging nuclear power plant pipes.
The proposed standard, ASTM WK36282: Guide for Selection of Coating for Repair and Rehabilitation of Buried Pipe Coatings for Nuclear Power Plants will provide coating guidance for nuclear plants seeking to repair or replace buried pipe.
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ASTM |
| A buried pipe from a nuclear plant shows damaged coating and pitting corrosion. |
Although coating technology for buried pipe at nuclear plants has evolved over several decades, no written standard currently addresses these advances, according to ASTM. The new standard will address coatings selection, types, functions and more.
Leaking Pipes
The new standard comes at a time of heightened regulatory concern over leaks in buried pipes at nuclear power plants. The leaks have been caused by damaged coatings, according to the Nuclear Regulatory Commission.
The NRC and the nuclear industry have met repeatedly in recent years on buried piping issues and have developed a series of initiatives aimed at buried pipe and tank integrity. In March, the NRC announced a new Aging Management Program for buried piping and a new buried piping initiative by industry.
Both initiatives include stepped-up inspections and excavations that NRC expects to result in increased reports of degraded piping.
Nuclear power plants have extensive above-ground and buried piping systems. Most of the pipes carry cooling water, some of which may contain slightly elevated levels of tritium or other radioactive isotopes. Some buried pipes also carry other materials, mainly diesel fuel. Protective coatings are used on buried pipe to prevent corrosion.
Although the recent leaks posed no safety hazard, according to the NRC, regulators and the industry “are reexamining the issue of buried piping to determine whether any changes are required in the current approach to the design, maintenance, and inspection of buried piping.”
30-Year-Old Coatings
The new standard is being developed by Subcommittee D33.02 on Service and Material Parameters, part of ASTM International Committee D33 on Protective Coating and Lining Work for Power Generation Facilities.
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| A Nuclear Regulatory Commission Fact Sheet issued in March illustrates “minor corrosion incidents” that have caused leaks in buried pipes and related systems “over several years” at “several” U.S. nuclear plants. The NRC has implicated damaged coatings in the leaks. |
“Many of the coatings on U.S. nuclear power plant buried piping were applied at least 30 years ago,” says Jon Cavallo, vice president of UESI Nuclear Services, who heads the ASTM panel that is drafting the standard.
“Since that time, many improvements to and innovations in buried pipe coating technology have been made,” said Cavallo, a former chairman of D33 and current chairman of D33.02. “The proposed standard will assist the user to identify viable options for repair and rehabilitation coatings.”
Key Technical Issues
The proposed standard will provide a method for identifying the existing coating system on a buried pipe and a guide for selecting a repair or rehabilitation coating system to be applied if needed.
Technical issues to be addressed in the standard include:
• Function of buried pipe coatings in nuclear power plants;
• Plant systems that may include buried pipe;
• Generic types of field-applied buried-pipe repair and refurbishment coatings;
• In-situ factors that affect selection of field-applied buried-pipe repair and replacement coatings; and
• ASTM and other standards used to evaluate performance of field-applied buried-pipe repair and refurbishment coatings.
One of the largest international standards development and delivery systems, ASTM welcomes participation in the development of its standards. Contact Cavallo at jcavallo@uesi.com or 603-431-1919.
The next meeting of ASTM Committee D33 will be July 26-27 in Charlotte, NC.
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