Indian Point Bolt Replacement, Refueling Done: Unit 3 Reactor Back In Service

CORTLANDT, NY – Entergy’s Indian Point Unit 3 nuclear power plant returned to service Thursday following its scheduled $100 million refueling, maintenance and inspection outage. Control room operators returned Unit 3 to operation this morning, sending electricity to the grid after a planned shutdown that began March 13.

“We will continue to provide reliable, safe and clean electricity to millions of New Yorkers for the next four years, in accordance with our settlement agreement with New York State,” said Tony Vitale, site vice president and Entergy’s top official at Indian Point, in an announcement. “Entergy continues to make the investments needed to ensure continued safe operation through 2021, as evidenced by the $100 million invested in the last two months on Unit 3 alone.”

Among the items inspected were bolts on a removable liner inside the reactor. Specialists replaced 270 of these bolts and confirmed that the plates secured by these bolts remained structurally sound and functional.

Though about the same number of the infamous baffle-former bolts were replaced in Unit 3 during the shutdown than had been replaced in Unit 2 when it was discovered that many bolts had deteriorated due to radiation-related stress, the Nuclear Regulatory Commission said "direct observations during the Indian Point Unit 3 outage indicated the condition of the Unit 3 bolts was better than at Unit 2."

SEE: Problem Inside Indian Point 2 Reactor: Bad Bolts

This was the second-to-last refueling outage at Unit 3 before its permanent shut down by April 30, 2021, under the settlement with New York State.

“Nearly 2,000 professionals, including 1,000 specialist contractors, performed hundreds of work tasks and activities that can only occur while the plant is shut down,” added Vitale.“Hundreds of thousands of person-hours of work were performed over the last two months to prepare Indian Point for safe, continuous operation for the next four years.”

Unit 2, which remains in service at full power and has been online for more than 300 continuous days, will undergo its final refueling and maintenance outage next spring before it permanently shuts down by April 30, 2020.

Unit 3 had remained online 96 percent of the time since its prior refueling and maintenance outage in 2015, generating more than 16.9 million megawatt hours of clean power, thereby preventing more than 7.6 million metric tons of carbon dioxide emissions.

Entergy officials pointed out that since the company purchased Indian Point more than 15 years ago, Entergy has safely delivered hundreds of millions of megawatt hours of virtually emissions-free power to the Hudson Valley and New York City, while investing more than $1.3 billion in safety and reliability improvements. Under Entergy’s ownership, Indian Point has established an excellent safety record and ranks among the most reliable power plants in the state. Inspectors at the U.S. Nuclear Regulatory Commission placed the plant in the agency’s top regulatory column for safety following more than 6,000 hours of inspections in 2016.

On January 9, as part of the settlement with New York State, Entergy announced its plan for the early and orderly shutdown of the two units at Indian Point.

The NRC issued a statement about the bolts.

During the spring 2016 refueling and maintenance outage for the Indian Point Unit 2 nuclear power plant, Entergy completed examinations of baffle-former bolts in the reactor vessel.

(Measuring about 2 inches in length and 5/8ths of an inch in diameter, the bolts hold in place a series of vertical metal plates. Known as baffle plates, they help direct water up through the nuclear fuel assemblies, where it is heated and subsequently used for power production. The baffle plates are attached to eight levels of horizontal plates called baffle-former plates, which are in turn connected to the reactor core barrel.

As far back as the late 1980s, cracking was identified in baffle-former bolts – the bolts securing the baffle plates to the baffle-former plates — in pressurized-water reactors (PWRs) in France. Both Indian Point Units 2 and 3 are PWRs. The degradation is caused by what is known as irradiation-assisted stress corrosion cracking.)

The examinations at Indian Point Unit 2 identified more baffle-former bolt problems than expected based on previous industry operating experience. The checks involved visual and ultrasonic testing (UT) and led to the determination that 227 of 832 were degraded or in locations inaccessible for testing. Entergy replaced all 227 bolts plus an additional 51 bolts to provide further margin for potential future bolt failures.

During the refueling and maintenance outage just completed for Indian Point 3, the same kinds of examinations were performed. There are 256 bolts found to have indications (potential flaws and therefore are considered degraded) and three that could not be tested. Entergy replaced all 259 bolts with potential degradation and an additional 11 bolts to provide further margin against potential future bolt failures, for a total of 270 bolts replaced.

There was an expectation that Indian Point Unit 3 would have fewer degraded baffle-former bolts than Indian Point Unit 2 because it was subjected to fewer operating cycles (Unit 2 came online in August 1974 and Unit 3 in August 1976) and lower neutron fluence. The exact cause for the number of potentially degraded bolts at Unit 3 is not yet known; as was the case at Unit 2, some of the removed bolts will be sent to a lab for analysis.

However, direct observations during the Indian Point Unit 3 outage indicated the condition of the Unit 3 bolts was better than at Unit 2. This is based on the fact that visual examinations completed by Entergy staff did not find any missing bolt heads or broken lockbars (a welded tab that helps hold the bolt in place; Entergy installed new bolts with a different design that does not include a lockbar) at Unit 3. In comparison, there were 31 baffle bolts identified as visual failures at Unit 2 (2 with missing bolt heads and 29 with broken lockbars). Also, one indication of bolt load-carrying capability is whether a bolt is removed intact during the extraction process, which can generate large amounts of torque and stress on a bolt. A significantly greater number of baffle bolts replaced at Unit 3 remained intact after the removal process than those removed during the Unit 2 outage.

The NRC inspectors will continue to monitor baffle-former bolt analysis results for Indian Point Unit 3 to ensure NRC requirements are met and to gain further insights.

SEE ALSO: Plan for Indian Point Closing, Aftermath