Nine Mile Point Nuclear Power Plant is a two-unit nuclear power plant located in the Town of Scriba, approximately five miles northeast of Oswego, New York on the shore of Lake Ontario. The 900 acre (3.6 km²) site is also occupied by the Fitzpatrick Nuclear Generating Station.

Nine Mile Point Nuclear Power Plant is operated by Constellation Energy Group. Constellation is also the sole owner of Unit 1, and owns 82% of Unit 2 (Long Island Power Authority owns the remaining 18%).

Nine Mile Point Units 1 and 2

Both units are General Electric boiling water reactors. Unit 1, a BWR-2, went online in 1969 and has a rated capacity of 609 MW. It is one of the two oldest nuclear reactors still in service in the United States; New Jersey's Oyster Creek Nuclear Generating Station is the other. Unit 2, a BWR-5, has been in operation since 1988 and has a rated capacity of 1,148 MW. Construction of both units, along with neighboring Fitzpatrick, was commissioned by Niagara Mohawk Power Corporation. Fitzpatrick was sold immediately upon completion, while Niagara Mohawk retained its share of the Nine Mile Point units until 2001, when it sold them to Constellation.

On October 31, 2006, Constellation announced that the NRC had granted 20-year license extensions to both units. Unit 1 is now licensed to operate until 2029 and Unit 2 is licensed until 2046.

The Nine Mile Point cooling tower is visible from Chimney Bluffs in Sodus, New York nearly 30 miles away.

Nine Mile Point Unit 3

On February 12, 2008, Unistar Nuclear, a joint venture between Constellation Energy and Électricité de France (EdF) announced it had notified the U.S. Nuclear Regulatory Commission (NRC) of its plan to submit a combined construction and operating licence (COL) application in late 2008 for an advanced-design U.S. Evolutionary Power Reactor (U.S. EPR) at Constellation Energy's Nine Mile Point site. The design is a Generation III+, four-loop pressurized water reactor. The U.S. EPR will be rated at 4,590 MW thermal/1,710 MW electrical gross. Plant loads will be approximately 110 MWe, thus the net generation is 1600 MWe net. Plant thermal efficiency will be approximately 36% (ratio of 1,710 MWe to 4,590 MWth).

The COLA was filed on October 1, 2008; the review process is expected to take between 36 and 42 months. Unistar noted that it has yet to make a final decision to build the plant.

1991 site area emergency

On August 13, 1991 a "site area emergency" was declared at the plant. According to Time magazine, this was the third occasion an SAE had been declared at a US nuclear plant.

The emergency was due to an electrical fault which caused a momentary loss of electrical power to the reactor and control room. The operators shut down the reactor in accordance with the emergency plan requirements. There were no injuries or release of radiation as a result of the incident. The reactor came back online 13 hours after the incident.

From NRC Information Notice 91-64, Supplement 1:

The facility was operating at full power when a phase-to-ground electrical fault occurred on phase B of the Unit 2 main power transformer. This resulted in a trip of the main generator, main turbine, and reactor. The fault also caused the voltage on electrical distribution phase B buses to drop to about half of its nominal value for approximately 200 milliseconds, after which it returned to normal.

This momentary voltage drop resulted in the simultaneous loss of power output from each of the five Non-Class 1E uninterruptible power supplies. Exide's UPS units have internal continuously charged back-up batteries to prevent a loss of control logic power. Exide's UPS control logic circuitry receives, processes, generates, and sends electrical signals essential for proper UPS operation. However, in this incident the back-up power battery packs were apparently past their useful life and were completely discharged.

The loss of power from the UPS units caused a loss of all the following: the control room annunciators, the safety parameter display system computer, control rod position indication, the plant process computer, the core thermal limits computer, the feedwater control system, some of the lighting for the plant, the plant radio and paging systems, some instrumentation for balance-of-plant systems, and some instrument recorders.

The loss of control room annunciators concurrent with the plant transient resulting from automatic tripping of the main generator, main turbine, and reactor caused the licensee (Niagara Mohawk) to declare a site area emergency in accordance with the site emergency plan. The loss of control rod position indicators and other equipment losses burdened the operators in implementing the emergency procedures. However, the operators shut down the plant in accordance with emergency procedures. About 13 hours after the plant trip, the reactor was placed in a cold shutdown condition; and approximately 1 hour later, the licensee ended the site area emergency.