2007 Cooling for the plant's steam condenser was provided by circulating water through it, drawn from the adjacent Connecticut river. This water did not come in contact with the nuclear reactor and was not radioactive. The cooling towers were used to cool water returning from the condenser before it was discharged back into the river at times when it was too warm to comply with the environmental discharge permit. In 2007 the fourth cell of the west cooling tower collapsed, spilling some of the non-radioactive, cooling water. The collapse was an "industrial safety event," which did not threaten the integrity of the reactor or release any radiation into the environment. The NRC stated that the remaining cooling tower had enough capacity to allow the plant to operate at full output, however, until September 16, 2007, the reactor was kept at 50% power. The cause of the collapse was found to be corrosion in steel bolts and rotting of lumber. Entergy asserted that future inspections would be much more stringent in order to prevent further problems.
2008 The cooling tower collapse caused Vermont's then governor,
Jim Douglas, to question the reliability of the power station: In March 2008, a State Senate committee recommended that the Legislature appoint a panel to oversee an independent review of the plant's reliability. The panel gave Vermont Yankee a generally positive review. "What this report suggests to me is there is not a cause or reason to seek the closure of the plant because of operational or safety concerns," said Public Service Commissioner, David O'Brien. The
Nuclear Regulatory Commission performed a tri-annual inspection July–August 2008. It found three "minor faults." An Associated Press report said that it had won "high marks."
2009 In May 2009, the vice-president of operations at Vermont Yankee told the PSB during the reliability review that he did not believe there was any radioactively contaminated underground piping at the plant, but that he would check and respond to the panel. On June 4, 2010, VPR reported that, because they had provided misleading information, Entergy Nuclear would be liable for legal expenses incurred by certain parties.
2010 In January 2010, the Vermont Department of Health reported that
tritium, a radioactive isotope of hydrogen, had been discovered in a sample of ground water taken from a monitoring well the previous November. The level of the isotope was initially below the acceptable limit for drinking water set by the
Environmental Protection Agency. By mid-January, however, the level had risen to 20,000
picocuries per liter (pCi/L), the federal limit for drinking water. The head of the Nuclear Regulatory Commission told Vermont's congressional delegation that the agency would devote more resources to addressing concerns about Vermont Yankee, and that he expected the source of the tritium leak would be located within the next several weeks. On February 4, 2010, Vermont Yankee reported that ground water samples from a newly dug monitoring well at the reactor site were found to contain about 775,000 pCi of tritium per liter (more than 37 times the federal limit). On February 5, 2010, samples from an underground vault were found to contain 2.7 million pCi/L. On February 14, 2010, the source of the leak was found to be a pair of steam pipes inside the Advanced Off-Gas (AOG) pipe tunnel. The pipes were repaired, stopping the leak. The New Hampshire Department of Health and Human Services made a similar statement after several tests of the river. During the search for the source of the tritium leak, other radionuclides were found in the soil at the site. Levels of
cesium-137 were found to be three to ten times higher than background levels. Silt in a pipe tunnel contained 2,600 picocuries/kg, but contamination outside the pipe tunnel was limited to a small volume, about of soil. According to the Vermont State Department of Health, there was no health risk from the cesium, as the quantities were small and it had not migrated. On May 20, 2010, the NRC released a report on Vermont Yankee: In early November 2010, a water leak caused by a faulty weld caused a "conservative" four-day shutdown while the pipe involved was repaired. A company spokesman said that "if plant managers had known on Sunday night what they knew on Monday, they might have tried to fix the leak while the plant kept running." In 2010, Vermont Electric Power Company constructed a new substation, designated as the Vernon Substation, on the Vermont Yankee site to serve as the site's new main transmission facility and to connect a new 345 kV transmission line to Central Vermont as part of its Southern Loop project. The aging Entergy-owned Vermont Yankee substation could not handle the additional line or any additional transformers and VELCO desired to have a utility owned and controlled substation for what is probably the state's most important interconnection point. Additionally, the local 115 kV system was relying exclusively on Entergy's single 345 kV to 115 kV transformer. The construction of the Vernon substation included a second 345 kV to 115 kV transformer to supplement the existing Entergy owned transformer. The additional transformer also provided redundancy for Vermont Yankee's source of offsite power. The four transmission lines that formerly connected directly to the Vermont Yankee substation now connect to the Vernon substation, and three tie-lines, one at 115 kV and two at 345 kV, connect the Vermont Yankee substation to the Vernon substation. Each 345 kV tie line is capable of carrying the full power output of the plant.
2011 During the week of January 17, 2011, tritium was detected at a level of 9,200
picocuries per liter (below the federally required reporting level) in an area 150–200 feet north of the location where it was detected a year earlier. According to the State's radiological health chief at the
Vermont Health Department, Bill Irwin, and Vermont Yankee spokesman, Larry Smith, the source of the leak was not yet known. Irwin and Governor
Peter Shumlin expressed concern about the discovery.
2012 On January 19, 2012, Judge J. Garvan Murtha of United States District Court in Brattleboro ruled that the state of Vermont could not force Vermont Yankee to close down, as the legislation that attempted to do so was based on radiological safety arguments that are the exclusive concern of the NRC. The judge also held that the state cannot force the plant's owner, Entergy, to sell electricity from the reactor to in-state utilities at reduced rates as a condition of continued operation.
2013 On June 7, 2013, Vermont's Public Service Board issued Entergy a Certificate of Public Good to install an outdoor diesel generator to replace a tie line from the nearby hydroelectric station as its station blackout power source. The outdoor generator would only operate if the plant's main emergency diesel generators located inside the turbine building were to fail. The outdoor generator is a self-contained unit that does not require cooling water from the plant's cooling water systems. The new generator would power instrumentation in the control room and would be capable of providing emergency AC power to one train of each of the plant's emergency cooling systems. On August 27, 2013, Entergy announced in a press release that it would close Vermont Yankee by the end of 2014. Among the reasons cited for the closure were ongoing low energy prices resulting from increased shale gas production, and the high operating costs of the plant. ==Protests and politics==