June 17, 2016
Indian Point Unit 2 was returned to service generating electricity following replacement of all degraded bolts on the reactor vessel insert liner. Engineers replaced 278 bolts. Inspections confirmed that the plates secured by these bolts were not damaged and remained structurally sound and capable of performing their safety function while Unit 2 was in operation. Both the inspection and replacement of bolts were successful, and the U.S. Nuclear Regulatory Commission has noted there are no safety concerns. Entergy will conduct a separate bolt inspection program at Unit 3 early next year.
Indian Point Unit 2 Returns to Service after $120 Million Refueling, Comprehensive Bolt Replacement, Hundreds of Inspections, Upgrades and Maintenance to Continue Providing Clean Power Safely and Reliably
- June 17, 2016
May 6, 2016
Entergy identified issues with the reactor vessel insert liner bolts as a result of a specialized, robust inspection of the Unit 2 reactor vessel internals implemented in accordance with the plant’s license renewal programs, going well beyond normal inspections performed during prior refueling outages. The issues identified with the reactor vessel insert liner bolts did not have an impact public health or safety.
This comprehensive inspection of the reactor vessel and internal components was scheduled to be conducted during the current refueling outage at Unit 2 in accordance with our long- standing license renewal commitments to the NRC. Contrary to some statements you may have seen in the press, we did not conduct these inspections due to intervention or criticisms expressed in our ongoing NRC proceeding. All other inspections are complete and show critical components at Unit 2 continue to perform safely.
Of those more than 2000 bolts that were inspected, 227 of those bolts were found to have issues that require further analysis. Bolt heads were missing on two of those 227 bolts, with the stem remaining in place. Ultrasonic testing found signs of degradation or other issues, such as missing lock-bars.
We performed visual inspections of 1,232 bolts, and both visual and ultrasonic inspections of more than 832 bolts located on the reactor vessel’s removable insert liner – called a baffle core – for a total of 2,064 bolts inspected. Each bolt, about two inches long and made of stainless steel, secures vertical plates to horizontal plates to form the perimeter of the liner. The bolts with identified issues were found only on the face of the removable liner, while bolts along the edges showed no issues. The plates give the fuel assemblies their geometry layout within the reactor.
Of the total 227 bolts with identified issues, we visually identified 31 as slightly protruding. Another 14 couldn’t be inspected with the ultrasonic testing device because we were unable to get the device to connect onto the bolts due to a configuration issue interface with our equipment. The remaining 182 bolts (of the 227) were identified as ultrasonic testing (UT) failures.
Each UT test consists of ten passes of the UT. If any of the UT passes indicated a spike – even if it was just one of the ten passes – we called that a UT failure. If a bolt had 10 of 10 passes, indicating all ten failed, it was also a UT failure.
We are sending out for further analysis some of the bolts with different test failures to get us more information. An analysis will be conducted by Westinghouse and a qualified independent engineering firm. The bolt issues will be corrected prior to returning Indian Point Unit 2 to operation. We are also analyzing potential impacts on Unit 3. In addition to being three operating cycles younger than Unit 2, Unit 3 also underwent a modification years ago that resulted in fewer high energy neutrons affecting bolts than Unit 2. As a result, bolt wear at Unit 3 would be expected to be less than at Unit 2, but our detailed review is ongoing.
This work is expected to add several weeks to the refueling and maintenance outage that began March 7. The schedule and work plan are still under development. Due to federal regulations and business-sensitive information, we are restricted in the level of detail we can provide about when we expected to return the plant to service.
The bottom line is we will not operate the plants if we couldn’t do so safely.
Engineers identified issues with bolts on a removable internal insert liner inside the reactor vessel. These bolts secure vertical plates to horizontal plates to form the perimeter of the liner.
Inspections of more than 2,000 bolts in the reactor’s removable insert liner revealed issues with approximately 11 percent that require further analysis.
The issues identified with the reactor vessel insert liner bolts did not impact public health or safety and will be corrected prior to returning Indian Point Unit 2 to operation.
The issues were discovered in March during a planned 10-year “In Service Inspection” of the reactor vessel. This consists of more 350 individual inspections, including 200 inspections of the reactor core, reactor vessel head and penetrations, and reactor vessel internals.
Indian Point Unit 2’s Aging Management Program, implemented in connection with license renewal, calls for an in-depth inspection of the reactor vessel every ten years. The first such inspection took place during a scheduled refueling and maintenance outage that began March 7, and used visual and where possible, ultrasonic inspections.
Engineers were able to identify the bolt issues as a result of a specialized, robust inspection of the unit 2 reactor vessel implemented in accordance with the plant’s license renewal application, going beyond normal inspections performed during each refueling outage. This program worked as intended to identify potential issues.
Engineers identified two missing bolts, and bars meant to hold them in place, and other degradation requiring replacement of bolts. Each bolt, about two inches long and made of stainless steel, holds plate inserts together inside the reactor.
An analysis of the bolts will be conducted by a qualified independent engineering firm to determine their condition and narrow potential causes for the issues identified. The bolt issues will be corrected prior to returning Indian Point Unit 2 to operation.
With comprehensive inspections on the entire reactor vessel finished, once a full engineering assessment of the issue is also completed and corrective actions taken, the unit can safely operate going forward.
This work is expected to add cost and several weeks’ duration to the refueling and maintenance outage.
Indian Point is a safe facility, and we will continue to safely operate the plant under the strict oversight of our federal regulator, the U.S. Nuclear Regulatory Commission. The issues identified with the reactor vessel insert liner bolts did not impact public health or safety and will be corrected prior to returning Indian Point Unit 2 to operation.
Both Indian Point units are equipped with multiple backup safety systems designed to detect and alert operators of any changes in conditions that would prevent the units’ safe continued operation. Operators can also shut the plant down in a matter of seconds if needed, and the plant is designed to automatically shut down as an added protection.
We have not yet performed this special-in-depth inspection of Unit 3’s reactor. A 10-year special in-depth inspection was scheduled to be performed on Indian Point Unit 3 during a refueling outage in the spring of 2019. However, our current plan is to conduct a similar analysis of bolts at Unit 3 sooner during the spring 2017 scheduled refueling outage.
Incidences in some earlier design European Pressurized Water Reactors (PWR) indicate that the reactor vessel internal bolting may be susceptible to age-related issues.
The industry determined that repairs, inspections, and evaluations of these components show the projected degradation is not a safety concern for a PWR plant through the end of its current license period.
The issues of degradation of PWR bolts make this time- and irradiation-dependent, requiring programs to manage the degradation for the license renewal period, which is why the more in-depth inspections of the reactor vessel internals have been incorporated into aging management programs, as was done at Indian Point.
For more information please read the following:
Indian Point Bolt Maintenance