An Outage Twist: Degraded bolts at New York Nuclear Plant Warrant Attention

Neil Sheehan
Public Affairs Officer
Region I

When the Indian Point Unit 2 nuclear power plant entered a refueling and maintenance outage in early March, the to-do list included a task born of industry operating experience, both in the United States and overseas.

BaffleBoltsGraphic1_cleanbigfontSpecialists were geared up to check on the condition of bolts employed in the reactor vessel at the Buchanan, N.Y., facility. These are the kind of bolts you likely wouldn’t find at your local hardware store. Rather, they are made of a stainless-steel alloy capable of withstanding decades’ worth of neutron bombardment, as well as extraordinarily high temperatures and pressure.

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.

In response, the U.S nuclear industry began checking on these bolts in a small number of domestic PWRs on a sample basis.

The NRC staff also made use of a communications tool called an Information Notice to advise U.S. plant owners of what had been observed in Europe. A March 1998 notice let U.S. plant owners know that the baffle-former bolt cracking reported in foreign PWRs had occurred at the juncture of the bolt head and the shank, a location not accessible for visual examination.

Several U.S. plants subsequently evaluated their baffle-former bolts and in some cases replaced a sizable number.

Jumping ahead, the Electric Power Research Institute developed a standard industry program for the aging management of PWR reactor vessel internals and submitted it to the NRC in January 2009. The NRC staff approved the approach in an agency safety evaluation issued in December 2011 and then published in January 2012 as MRP-227-A. (MRP is short for Materials Reliability Program.)

Under this new standard, U.S. PWRs were to conduct an initial ultrasonic examination of all of their baffle-former bolts when the plant had between 25 and 35 effective full power years of service.

This is exactly what was being done at Indian Point Unit 2 during the current outage. It was adhering to the standards of MRP-227-A. In the course of this review, it was determined that 227 of 832 baffle-former bolts at the plant were degraded, which means any indication of cracking. What’s more, two bolt heads were missing.

The number of degraded baffle-former bolts was the largest seen to date at a U.S. reactor.

Entergy, Indian Point’s owner, is in the process of analyzing the condition and replacing the degraded bolts. It will also assess any implications for Indian Point Unit 3, though that reactor is believed to be less susceptible to the condition for several reasons, including fewer operational cycles.

As for the NRC, we will independently review the company’s analysis and bolt-replacement plans to ensure safety. The results of those reviews will be documented in an upcoming inspection report for the plant.

We have already had a metallurgical specialist on-site reviewing the company’s evaluations of the bolts and have agency experts reviewing the matter.

More information will be forthcoming on the issue. However, it’s important to note that the NRC staff will ensure the condition is fully understood and addressed prior to the plant returning to service. The NRC staff will also consider all available information in evaluating if changes are needed to the current inspection programs for these bolts across the industry.

 

Indian Point 3 Timely Renewal

Diane Screnci
Sr. Public Affairs Officer
Region I

It’s been more than eight years since Entergy filed an application requesting that the NRC renew the operating licenses for Indian Point Units 2 and 3. And, a final decision is still a ways off.

indianpointUnder NRC regulations, if a company submits a sufficient application for a renewed license at least five years before the expiration of the current license, then the request is considered “timely” and the facility is allowed to continue operating under its current license until the NRC issues a decision on the license renewal request.

On December 13th, Indian Point 3 will enter the period of “timely renewal.”  Entergy submitted a license renewal application for both Indian Point Units in April 2007, meeting the timeliness provision. The Unit 3 license would have expired December 12, 2015. This doesn’t mean the unit will be operating without a license. Rather Unit 3, like Unit 2 (which entered timely renewal in September 2013), will continue to operate under its existing license.

The Atomic Energy Act specifies that operating licenses can be issued for up to 40 years and allows license renewals in 20 year increments. Thus far, the NRC has issued renewed licenses to 81 reactors. Typically, it takes about 22 months for the staff to reach a decision on whether to renew a license – longer if there’s a hearing. In the case of Indian Point, though, the process has taken longer than projected, due in part to the large number of contentions the parties have raised in the hearing.

Although a final decision on the application hasn’t been reached, the NRC staff has measures in place to provide assurance the facility will continue to operate safely during this time period.  We’ll continue to carry out our extensive regulatory and oversight activities. NRC inspectors, including the three on-site Resident Inspectors and specialist inspectors from the Regional office, will continue their duties during this period, providing independent oversight of the facility on a continual basis.

In a September 28 letter to the NRC, Entergy confirmed that the Unit 3 license renewal commitments required to be in place prior to entry into the period of extended operation were complete. In October, Entergy certified that the Indian Point 3 Updated Final Safety analysis report had been updated to incorporate aging management programs for the unit. In response, that same month, we completed an inspection to review the activities Entergy has taken to prepare for operating in timely renewal and found that the processes and commitments had been properly implemented.

While it might be some time before the Commission reaches a final decision on license renewal at Indian Point, our independent oversight of the facility will continue uninterrupted while in “timely renewal.”