Millstone hits the grindstone

When Dominion Generation bought the Millstone nuclear power station near New London, Connecticut for $1.3 billion in 2001, it had something to prove. The company was starting up a new nuclear division, separate from the Virginia-based stations North Anna and Surry that the company’s predecessor Virginia Electric Power Company developed in the 1970s.

The situation at Millstone had improved slightly since a low point in the mid-1990s, when all three reactors were shut down because of regulatory concerns, and concerns about safety. The then-operator Northeast Utilities recovered the two newer units. Millstone 3, an 1130MWe four-loop Westinghouse PWR from the 1980s was restarted in July 1998. Millstone 2, an 870MWe Combustion Engineering PWR from the 1970s came online in May 1999. Dominion managers worked at Millstone during the restart process. Millstone 1, a 660MWe BWR, was retired in 1998 for cost reasons, explains William Matthews, Dominion’s senior vice president, nuclear operations.

“We took ownership of Millstone from Northeast Utilities on April 1, 2001,” Matthews says. “These were our first units for the nuclear division in Dominion Generation, and we wanted to show that we could make this a profitable venture. We immediately launched into a viability upgrade programme.”

The older unit 2 was the main beneficiary of a $500 million investment programme, with new control rod control system, new digital feedwater level control system and feedwater speed control systems in 2002, new turbines in 2003, a new reactor vessel head in 2005, a new pressurizer (after Alloy 600 cracking problems) in 2006. Unit 3 received a new voltage regulator control system and new turbines in 2004. Both units benefitted from new step-up transformers in 2007.

In 2008, after GE performed a turbine measurement reevaluation, and swapped out new feed pump turbines, Dominion contracted Westinghouse to uprate unit 3 by 77MWe.

Seven years on, the lifetime combined load factor had risen by 168 basis points to 71.8%, according to NEI’s load factor tables (September 2008).

Matthews concludes: “Essentially we now produce more electricity than the three units combined used to do. It has been well worth the investment to make it reliable.”

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