The Joys of Inconel 600

Portland General Electric's Trojan nuclear plant got decommissioned because of steam generator tube degradation.   A couple of links:

Trojan Nuclear Plant Implosion - May 21, 2006 - YouTube.com

Watch on YouTube

Oregon's Trojan Horse - High Country News

"Like the release of hostages minutes after Ronald Reagan's inauguration or a tax cut in an election year, the timing was suspicious. Six days after Portland General Electric (PGE) defeated two ballot measures that would have closed its Trojan nuclear power plant, it closed the plant forever.

PGE, Oregon's largest utility, had spent millions to defeat the measures, even promising to close the plant early, in 1996. But last Nov. 9 those plans changed. A cracked steam tube released radioactive gas into the plant, and Trojan was temporarily closed for repairs. Two months later the temporary shutdown was made permanent.

New information had arisen, PGE explained. Trojan's steam tubes were discovered to be more corroded than previously thought. Inexpensive replacement power had become available from California. It would be cheaper to close Trojan immediately, PGE decided."

Nice history included in the complete version of this next one...

Comments Concerning Indian Point Nuclear Generating Unit 2 - Public Citizen

"The rupture of as few as ten steam generator tubes could result in the meltdown of the reactor fuel rods, potentially releasing catastrophic amounts of radiation into the surrounding communities.

Unfortunately, the Nuclear Regulatory Commission (NRC) staff continues to find that cracks in steam generator tubes may go undetected 40 to 60% of the time. In a November 1992 memo, which had been withheld from public disclosure, the NRC's Director of Nuclear Reactor Regulation reported that "steam generator tube rupture events appear to be unavoidable."

According to the NRC, spontaneous tube ruptures have occurred at a rate of approximately one every 2 years for the last 20 years, while tube failures that were incipient and self-identifying through excessive steam generator tube leakage just prior to rupture have occurred at a rate of approximately one per year."

The Achilles' Heel of Nuclear Power - In Brief - E: The Environmental Magazine

"What PGE didn't mention, however, was a discovery that could be the Achilles' heel of nuclear power. A space-age chrome-lead-nickel alloy called Inconel 600, used in Trojan's cooling tubes, had worn out almost 20 years sooner than expected, allowing radioactive gas to escape into the plant.

And tiny, virtually undetectable cracks in the tubes, if present, could lead to a loss of coolant, which could, in turn, cause the worst-case nuclear nightmare--a core melt down. This danger reaches far beyond the lush Oregon forests surrounding Trojan; the same alloy is used in nukes all over the globe, including two-thirds of U.S. plants."

Steam Generator Degradation and Its Impact on Continued Operation of Pressurized Water Reactors in the United States - Electric Power Monthly August 1995

"As of December 31, 1994, 35 steam generators had been replaced in 12 of the 72 operating PWR’s, and 3 units had been shut down prematurely, due primarily (or partially) to degradation of their steam generators: Portland General Electric’s Trojan unit, located in Prescott, Oregon, in 1992; Southern California Edison’s San Onofre 1, located in San Clemente, CA, in 1992; and Sacramento Municipal Utility District’s Rancho Seco unit in 1989.

In the coming years, operators of PWR’s in the United States with degraded steam generators will have to decide whether to make annual repairs (with eventual derating likely), replace the generators, or shut the plants down prematurely."

The Joys of Inconel 600

Portland General Electric's Trojan nuclear plant got decommissioned because of steam generator tube degradation.   A couple of links:

Trojan Nuclear Plant Implosion - May 21, 2006 - YouTube.com

Oregon's Trojan Horse - High Country News

"Like the release of hostages minutes after Ronald Reagan's inauguration or a tax cut in an election year, the timing was suspicious. Six days after Portland General Electric (PGE) defeated two ballot measures that would have closed its Trojan nuclear power plant, it closed the plant forever.

PGE, Oregon's largest utility, had spent millions to defeat the measures, even promising to close the plant early, in 1996. But last Nov. 9 those plans changed. A cracked steam tube released radioactive gas into the plant, and Trojan was temporarily closed for repairs. Two months later the temporary shutdown was made permanent.

New information had arisen, PGE explained. Trojan's steam tubes were discovered to be more corroded than previously thought. Inexpensive replacement power had become available from California. It would be cheaper to close Trojan immediately, PGE decided."

Nice history included in the complete version of this next one...

Comments Concerning Indian Point Nuclear Generating Unit 2 - Public Citizen

"The rupture of as few as ten steam generator tubes could result in the meltdown of the reactor fuel rods, potentially releasing catastrophic amounts of radiation into the surrounding communities.

Unfortunately, the Nuclear Regulatory Commission (NRC) staff continues to find that cracks in steam generator tubes may go undetected 40 to 60% of the time. In a November 1992 memo, which had been withheld from public disclosure, the NRC's Director of Nuclear Reactor Regulation reported that "steam generator tube rupture events appear to be unavoidable."

According to the NRC, spontaneous tube ruptures have occurred at a rate of approximately one every 2 years for the last 20 years, while tube failures that were incipient and self-identifying through excessive steam generator tube leakage just prior to rupture have occurred at a rate of approximately one per year."

The Achilles' Heel of Nuclear Power - In Brief - E: The Environmental Magazine

"What PGE didn't mention, however, was a discovery that could be the Achilles' heel of nuclear power. A space-age chrome-lead-nickel alloy called Inconel 600, used in Trojan's cooling tubes, had worn out almost 20 years sooner than expected, allowing radioactive gas to escape into the plant.

And tiny, virtually undetectable cracks in the tubes, if present, could lead to a loss of coolant, which could, in turn, cause the worst-case nuclear nightmare--a core melt down. This danger reaches far beyond the lush Oregon forests surrounding Trojan; the same alloy is used in nukes all over the globe, including two-thirds of U.S. plants."

Steam Generator Degradation and Its Impact on Continued Operation of Pressurized Water Reactors in the United States - Electric Power Monthly August 1995

"As of December 31, 1994, 35 steam generators had been replaced in 12 of the 72 operating PWR’s, and 3 units had been shut down prematurely, due primarily (or partially) to degradation of their steam generators: Portland General Electric’s Trojan unit, located in Prescott, Oregon, in 1992; Southern California Edison’s San Onofre 1, located in San Clemente, CA, in 1992; and Sacramento Municipal Utility District’s Rancho Seco unit in 1989.

In the coming years, operators of PWR’s in the United States with degraded steam generators will have to decide whether to make annual repairs (with eventual derating likely), replace the generators, or shut the plants down prematurely."