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Japan Nuclear Corrosion Spurs Inspections

Tuesday, January 17, 2017

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Inspections of pipes at nuclear sites in Japan have been conducted for decades without removing insulation, and now more thorough check-ups are reportedly revealing considerable corrosion.

The Japan Times reported Sunday (Jan. 15) that a thorough inspection of ventilation pipes at the currently idle Shimane 2 nuclear reactor revealed extensive corrosion and holes, including one that measured 30 centimeters by 100 centimeters, or about 3 square feet.

Shimane nuclear plant
Qurren, CC BY-SA 3.0, via Wikimedia Commons

A thorough inspection of ventilation pipes at the currently idle Shimane 2 nuclear reactor reportedly revealed extensive corrosion and holes, including one that measured 30 centimeters by 100 centimeters.

The revelation was reported by Chugoku Electric Company to Japan’s Nuclear Regulation Authority, the newspaper says, and it comes at a time when Japan is readying more reactors to be restarted after a mass shutdown five years ago. The recent inspection was reportedly the first time the insulation had been removed from the pipes since the reactor opened—in 1989.

Inspections Planned

Citing unnamed sources, the Times says the NRA plans thorough inspections of all of Japan’s 42 viable commercial reactors in light of the problems uncovered at the Shimane plant. The newspaper reports that NRA officials have said the corrosion may violate nuclear standards.

NRC officials at Fukushima
U.S. Nuclear Regulatory Commission, CC BY 2.0, via Wikimedia Commons

Japan shut down its commercial nuclear reactors after the tsunami-triggered nuclear disaster at the Fukushima Daiichi plant in 2011.

Shimane is located on the coast, leading to speculation that salty air may have played a role in pipeline corrosion.

Nuclear Restart

Japan shut down its commercial nuclear reactors after the tsunami-triggered nuclear disaster at the Fukushima Daiichi plant in 2011. In 2015, the country began to restart some of them; so far, the Sendai 1 and 2 reactors and Ikata 3 have returned to service. (Two reactors, Takahama 3 and 4, were returned to service, but then idled again due to lawsuits.)

According to the Times, two of the reactors that are currently in operation—Sendai 1 and Ikata 3—have not undergone thorough check-ups in which pipe insulation is removed since they returned to service.

Past Corrosion Problems

Corrosion has played a part in safety lapses at nuclear facilities in Japan before. At Fukushima, the same site where the 2011 tsunami led to meltdowns and radioactive releases, an incident took place in 1991 in which corrosion in pipes conveying seawater for cooling purposes led to a flood in the turbine building.

   

Tagged categories: Asia Pacific; Corrosion; Insulation; Nuclear Power Plants; Pipes; Quality Control; Salt exposure

Comment from David Grove, (1/17/2017, 7:27 AM)

Corrosion under insulation is a problem that many refuse to face during construction and/or maintenance. The insulation maintains a wet/damp condition, regardless of being hot or cold. And most pipes are painted with IOZ or epoxies that are not geared for full or extended immersion. Some types of Fireproofing products create the same problem. Inspections must require some insulation removal to ensure that corrosion does not become severe. The logic is that you evaluate the actual exposures and design. Are there sections that will be exposed to rain or moisture? Was the design difficult to install or insulate and was the pipe surface or coating possibly damaged during the difficult installation? I believe these locations are the first targets you should focus on for the inspections.


Comment from James Baglier, (1/17/2017, 8:46 AM)

What is the ID of these pipes? What temps do they usually operate at? Can the corrosion possibly be addressed by an internal lining of the pipe (SIPP) as a safety alternative?


Comment from Peter Bock, (1/18/2017, 10:47 AM)

David Grove is correct. Although IOZ has not been used under insulation in the US for nearly two decades, the story overseas is different. But both here and there, maintenance efforts frequently skimp on removing jacketing and insulation to determine the state of the pipe or vessel steel underneath. Out of sight, out of mind, and corrosion grows unchecked -- there are jacketing systems which will prevent water ingress and damp insulation, but they are rarely used, so CUI is -- in effect -- an intermittent immersion situation at best and a full immersion situation in most cases. With the cost of removing and replacing jacketing and insulation, the corrosion is often not found until it is extensive.


Comment from Tony Rangus, (1/18/2017, 11:09 AM)

This is HVAC, not process piping handling radioactive materials. From the Japan Times article "...had detailed checkups performed on the air conditioning and ventilation systems of their central control rooms...". The old "THE SKY IS FALLING" knee-jerk reaction for anything nuclear. Reminds me of the 1980's when an intervener at San Onofre claimed bad welding & pointed out the bad welds. Funny thing was, the welds being pointed were on the stairways in an office building. OH MY OH MY the reactor plant is ready to fall down!!


Comment from peter gibson, (1/18/2017, 3:56 PM)

An aside.Japan shut down the reactors after the incident. All big mouth at the time with no energy options. Now,want to restart. Feel good stuff made way for practical. Humans have short memories.Lets see what happens next time. Will they shut them down.


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