Transformer Troubles Again at Indian Point
March 5, 2012 § 1 Comment
TransformerTroubles again at Indian Point
By Abby Luby
Buchanan – – To avert a transformer explosion atIndian Point, like the two previous explosions over a year ago, Entergy decidedto take the Unit 3 reactor off the grid last week because of transformerproblems. The plant was back on line after a 36 hour, unplanned shut down. Entergy, the owner ofIndian Point, announced that there was no release of radioactivity and nothreat to workers or the public.
Officialshere at the nuclear power plant had detected an increase in combustible gases such as carbon dioxide and nitrogen, which are needed to run thetransformer, and which, if ignored, could have ignited a fire. Transformerstake electricity generated by the plant – some 22,500 volts – and step up that voltage to a level needed to feedthe electrical grid (typically 215,000 to 500,000 volts). Highly flammable oil,used to cool the transformers, has to be carefully monitored because mixing theoil with high voltage can cause the transformer to blow up. An option to usingoil is the more expensive nitroglycerine.
Transformer problems at Indian Point is nothing new. A transformer explodedat Indian Point Unit 2 in November 2010, prompting Entergy to shut down thereactor for 17 days. A month later the 30 year old transformer at Unit 3exploded, closing that reactor for almost a month. In 2007 a transformer firecaused an automatic shut down for Unit 3.
“Plantworkers monitor the condition of the oil, such as the temperature, salinity,contamination,” said David Lochbaum of the Union of Concerned Scientists. “When problems are detected, one can either remove the transformer from service andfix the problem before it gets worse, or wait until the transformer blows up.”
When Entergy took Unit 3 off line last week, NRCspokesman Neil Sheehan said the transformer would be swapped out for anotherauxiliary transformer. “Our Senior Resident Inspector assigned to IndianPoint 3 was at the plant overnight to monitor the downpower and the company’sapproach to dealing with the auxiliary transformer issue. The inspector did notidentify any immediate safety concerns. We will continue to follow thesituation and assess repair activities associated with the transformer.”
Unplanned shutdowns lower a plant’s safety rating if there are more than three unplannedshutdowns within a year. Because the reactor was not taken off line, this would not count as a shutdown. It will, however, count as a hitagainst the plant’s Performance Indicator for Unplanned Power Changes per 7,000Critical Hours. Unit 3 had been online generating electricity for327 continuous days prior to yesterday. Unit 2 is at full power and has beenonline for 44 continuous days.
The two working reactors are capable of pumping outabout 2000 megawatts of electricity. Accordingto records from Con Edison, the utility company who sells electricity to New York andWestchester County, the region uses 9000 to 13,000megawatts of electricity daily, depending on the weather. The 2000 megawattsproduced by Indian Point is about 15% to 22% of the daily region demands.Entergy has claimed that Indian Point provides up to 40% of the region’selectricity needs, which it does when the demand falls to 5000 megawatts. Usage usually drops on Sunday mornings in the spring and fall between 3a.m. and5 a.m. when the city is asleep, offices are shut down, air conditioners areoff. Those off-peak times of less usage happens about 12 times a year.
Entergy has applied to renew their operatinglicense to run Indian Point for another 20 years. One license expires nextyear, the other in 2015.