A sampling of nuclear safety problems
USA Today
December 12, 2007
Since the 1979 Three Mile Island accident, there have been 18 "significant precursors," or equipment failures, at U.S. nuclear plants that sharply raise the chance of a reactor core meltdown, says the Nuclear Regulatory Commission. There have been four since 1990. Since 1988, there have been 337 precursors that increase the risk of a meltdown more modestly.
Significant precursors
Problems that increase the risk of a core meltdown within a year from an average 1 in 17,000 to greater than 1 in 1,000.
- Plant: Davis-Besse
Location: Oak Harbor, Ohio
Date: February 2002
What happened: Leak through cracked nozzles wore away reactor vessel lid. Debris from the corrosion damaged emergency pumps. Loss of water from reactor core through lid could have led to meltdown within months.
- Plant: Catawba
Location: Rock Hill, S.C.
Date: February 1996
What happened: During storm, loss of power needed to run vital core cooling systems. Lines linking emergency generator to cooling systems disabled. Plant used alternative generator. No core damage.
- Plant: Wolf Creek
Location: Burlington, Kan.
Date: Septenber 1994
What happened: Misaligned valve prevented water from flowing into reactor core from storage tank. Core temperature rose 7 degrees. Workers realigned valve. No core damage.
- Plant: Harris
Location: New Hill, N.C.
Date: April 1991
What happened: Emergency system that injects water into reactor core would not have operated properly ebcause of a broken relief valve. Other water supply systems available. No core damage.
Less-serious precursors
Problems that increase the risk of a core meltdown from an average 1 in 17,000 to up to 1 in 1,000.
- Plant: Clinton
Location: Clinton, Ill.
Date: January 2006
What happened: System that notices when emergency tank water gets too low and instead pumps water from another source was set at too low a level. Water would have run out in event of core overheating. Found during test. No core damage.
- Plant: Callaway
Location: Callaway, Fulton Miss.
Date: March 2002
What happened: Debris from water tank's rubber lining floating in water. Could have caused failure of all emergency pumps that cool reactor in case of overheating. Found during test. No core damage.
- Plant: Columbia
Location: Richland, Wash.
Date: April 2002
What happened: Electrical breakers that operate both primary and backup pumps to cool the core in emergency were faulty, so all systems might have failed in crisis. Found during check. No core damage.
- Plant: Kewaunee
Location: Carlton, Wis.
Date: February 2001
What happened: Cables that operate both primary and backup core-cooling systems located in same area and too close to sprinkler systems. In case of fire that activated sprinklers, water likely would have shorted both primary and backup emergency systems needed to cool core. Found during check. No core damage.
Source: Nuclear Regulatory Commission
Fair Use Notice.
