Millstone Nuclear Power Plant


The Millstone Nuclear Power Station is a nuclear power plant in Connecticut and the only multi unit nuclear plant in New England. It is located at a former quarry in Waterford.
With a total capacity of over 2 GW, the station produces enough electricity to power about 2 million homes.
The operation of the Millstone Power Station supports more than 3,900 jobs, and generates the equivalent of over half the electricity consumed in Connecticut.
The Millstone site covers about 500 acres.
The power generation complex was built by a consortium of utilities, using Niantic Bay as a source of coolant water.
Millstone Units 2 and 3, both pressurized water reactors, were sold to Dominion Resources by Northeast Utilities in 2000 and continue to operate.
The plant has had numerous safety-related shutdowns and at times been placed on enhanced examination status by the Nuclear Regulatory Commission.
In 1999 Northeast Utilities, the plant's operator at the time, agreed to pay $10 million in fines for 25 counts of lying to federal investigators and for having falsified environmental reports.
Its subsidiary, Northeast Nuclear Energy Company, paid an additional $5 million for having made 19 false statements to federal regulators regarding the promotion of unqualified plant operators between 1992 and 1996.
On November 28, 2005, after a 22-month application and evaluation process, Millstone was granted a 20-year license extension for both units 2 and 3 by the NRC.

Licensing history and milestones

Unit 1

Millstone 1 was a General Electric boiling water reactor, producing 660 MWe, shut down in November 1995 before being permanently closed in July 1998.
Millstone 2 is a Combustion Engineering pressurized water reactor plant built in the 1970s, and has a maximum power output of 2700 thermal megawatts, or MWth. It has 2 steam generators, and 4 reactor cooling pumps. It is undergoing an upgrade to its safe shutdown system which already met NRC standards. During its refueling outage in October 2006, the operator installed a new pressurizer.
Millstone 3 is a Westinghouse plant that started operating in 1986, and has a maximum power output of 3411 MWth. In the summer of 2008, the NRC approved a power uprate for Unit 3 that increased its electrical output 7.006% to 3650 MWth. The increase took effect by the end of 2008.
In December 1977, two hydrogen explosions occurred at the plant.
The second explosion injured one man, who required hospitalization.
In October 1990, operator error during a routine test caused a shutdown of unit 2.
In September 1991, twenty reactor operators failed required licensing examinations. The shortfall of licensed operators necessitated a shutdown of unit 1 until March 1992.
In 1995 the U.S. Nuclear Regulatory Commission began a safety investigation relating to refueling procedures at Millstone unit 1, based on information provided by George Galatis, a senior nuclear engineer.
On February 26, 1996, a leaking valve forced the shutdown of units 1 and 2.
Multiple equipment failures were found.
Time magazine featured the plant on its cover, calling its operator a "rogue utility", and the Nuclear Regulatory Commission singled out Millstone for additional attention.
Also in 1996, the plant released one gallon per hour of hydrazine into Long Island Sound.
The plant's operators were convicted in 1999 for falsifying environmental records related to the hydrazine release.
Following the Time article and the subsequent shutdown of all reactors, unit 2 restarted May 11, 1999 and unit 3 restarted July 1, 1998.
Unit 1 was never restarted as the cost of remedying numerous safety issues was too high.
In 2002 Millstone's operators were fined $288,000 for failing to have properly accounted for two uranium fuel rod components that had been misplaced 30 years earlier in 1972.
On April 17, 2005, Millstone unit 3 safely shut down without incident when a circuit board monitoring a steam pressure line short-circuited, which caused the board to malfunction and indicate an unsafe drop in pressure in the reactor's steam system, when in reality there was no drop in steam pressure. The cause was attributed to tin whiskers on the board. In response to this event, Millstone implemented a procedure to inspect for these whiskers at every refueling outage, or 18 months.
In September, 2009, unit 2 shut down when an electrical storm caused power fluctuations.
When workers tried to restart the unit, they discovered a small leak in the reactor coolant pump.
On December 21, 2009 the Unit 3 reactor tripped and shut down for longer than 72 hours.
On July 27, 2009, the Unit 2 reactor tripped and shut down for longer than 72 hours.
On August 9, 2013, the Unit 3 reactor tripped and shut down due to a malfunction.
In 2016, unit 3 was shut down following a hydrogen gas leak.

Surrounding population

The Nuclear Regulatory Commission defines two emergency planning zones around nuclear power plants: a plume exposure pathway zone with a radius of, concerned primarily with exposure to, and inhalation of, airborne radioactive contamination, and an ingestion pathway zone of about, concerned primarily with ingestion of food and liquid contaminated by radioactivity.
The 2010 U.S. population within of Millstone was 123,482, an increase of 29.5 percent in a decade, according to an analysis of U.S. Census data for msnbc.com. The 2010 U.S. population within was 2,996,756, an increase of 9.5 percent since 2000. Cities within 50 miles include Hartford.

Seismic risk

The Nuclear Regulatory Commission's estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Millstone was Reactor 2: 1 in 90,909; Reactor 3: 1 in 66,667, according to an NRC study published in August 2010.