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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.

 

23 responses to “An Outage Twist: Degraded bolts at New York Nuclear Plant Warrant Attention

  1. auditmanagementblog May 5, 2016 at 11:49 am

    thanks for sharing

  2. steamshovel2002 May 4, 2016 at 6:19 pm

    https://adamswebsearch2.nrc.gov/webSearch2/main.jsp?AccessionNumber=ML15223A435

    How are these guys at IP? I know IP has intensive relicensing contention core inspections. See attachment. It’s the 2010 Cook root cause on the degradation. I hope the DPS is going to pry the RCA on the baffle bolt issue from IP. Cook has had extensive baffle plate bolt problems across both plant and in the same 2010 inspection found serious degradation in the below components.The degradations seem related to me. Will the below degradations show up this outage at IP?

    Clevis Insert Bolts
    ” Clevis Dowel Pins
    * LRSS Lug Weld
    * BMI Nozzles and Welds

    Can you even imagine the plant vulnerability with the worst case degradation on the above components and the worst case degradation of the baffle plates bolts? I’d like to see the risk perspective numbers on that baby? How does anyone even know the true worth of these components?

    It is an accident never conceived by anyone before except me. Sound familiar? You are sabotaging the licensed operators. Thank you UCS!

  3. steamshovel2002 May 4, 2016 at 5:14 pm

    ***My licensed operator experience: is there accurate licensed operator simulator training on a blown out baffle plate accident at IP or all the rest of the plants? Does the NRC know how a blown out BRP will developed and trip the plant? How are the operator supposed to deal with the problem.
    .

    • Moderator May 5, 2016 at 4:15 pm

      We would expect plant control room operators to follow procedures and their training to address the effects of any problems resulting from equipment problems, including baffle plates.

      Neil Sheehan

      • steamshovel2002 May 6, 2016 at 12:56 pm

        So you want me to guess? I think a large void would form in the highest power region of the core. Reactor power would mysteriously drastically decline while rods out. The pressurizer level would quickly spike. I doubt you can ever establish water level two thirds core height.

  4. steamshovel2002 May 3, 2016 at 4:47 pm

    Dr. Bill,

    Click on the link in my post before this.

    Actually I think facts have very little use by themselves. It is emersion…it is whatever it takes to get addictively immerse in a worldly problem. It’s the human heart’s ability to stay on task to the bitter end. I value intelligence magnitudes over facts. Facts don’t move a human heart, move the human spirit; it only superficially simulates the brain. It’s only the truth that slowly changes our hearts.

    There is nothing out there today except the old gunslinger professional class, the establishment and money grubbing PhDs. I call a rare PhD with a moral heart a miracle. It’s god’s precious gift to humanity.

    So I am trying to gain control of a spinning out of control Vermont Yankee in about 1992. I am trying to collude with the other side…the local Stone Age anti nukes. We had some success with manipulating a sitting Vermont Governor. The only life on the line is me and my family. I didn’t give my family a choice. The antis are coaching me I have to steal documents in order to be believed. I say, you don’t believe me, you don’t trust me? I had explained, just wing it out there what I say, and see how the system responds. None of them had a federal license to operate a nuclear power plant. But now I am seething mad at them now. I spitting yell out to them, YOU IDIOTs! They never liked me. My children use to call it spit yelling at them. Dad, you going to spit yell at me again? My little girl was such a smart firecracker. Everyone adapts to the environment eventually. My Irish mother use to spit yell at me, look at how I turned out? I spit yell at the antis, there is a particular ugly face that goes along with this; “I am the guy who forces my bosses and the NRC to write the documents you seek”. You want me to steal the documents I created by forcing my boss’s hands? I revamped the VY employee concern problem over this and it had implication all over the industry. Spit yelling don’t work except sometimes for little children. I have no idea how I survived my children’s youths.

    You get it, the system only documents what they want you to see. Not describe the magnificent truth. Who said, “Only the truth will set your free”.

    Mike Mulligan
    Hinsdale, NH

  5. steamshovel2002 May 3, 2016 at 10:05 am

    Talking Points to NY’s DPS:

    ***“Unfortunately the internals of most Western PWRS and WWERs were constructed with two of the most the swelling–prone steels that are commercially available.”

    between 304SS plates and 316SS bolts

    There are at least three things going on here.

    1) The startling lack of knowledge with the attributes of core components being highly irradiated and under stress: high temperature and bolt stress (tensile). Under high prolonged radiation, core components change their dimensional measurement such as in swell, creep, void formation and ductility, amount others.

    2) The baffle plates swell and creates a beyond design tensile stress on the bolt shank and head. This is the area where the IASCC cracking occurs. The swelling of the baffles tries to pull out the bolt leading to dangerous tensile stress. It is much like the damage of frozen pipe (the tremendous forces).

    3) The differential expansion…swelling…between the between 304SS plates and 316SS bolts. This can de-torque the bolt and later create beyond design tensile stress on the bolt.

    ***Selectively replacing bolts can create a dangerous counter-intuitive condition within deferential expansion between the new bolt and old baffle beyond the bolt design tensile stress at plant end of life. In other words, bolt tensile stress could be much more severe for an “old baffle plate and a replacement new bolt” than an “old bolt and old baffle plate” both at end of plant life.

    The reason the industry chose 316ss for bolt is the high tensile stress this alloy can withstand. The reason why 304ss was used for the baffle plate is because this was much more inexpensive. We wouldn’t have the cracks in the bolts if the baffle plate was made from the same alloy as the bolt.

    This is why Entergy wants to keep information about the bolt problem close to the vest before startup. They are hoping to restart the plant before the inspection comes out. This way they won’t have to replace the baffle plates this outage. It’s the old regulator-corporation Washington two step.

    I wouldn’t at all allow the plant to restart without all new baffle plates and all new bolts. I’d have identical stainless alloy for both the bolt and the baffle plate.

    The NRC and Entergy should release all inspections reports on this event and Entergy should release all their investigative reports concerning the baffle-reformer before allowed to start-up. All documentations should be open for public inspection before plant start-up.

    I hate the idea of bureaucrats making secrets behind closed door.

    Mike Mulligan
    Hinsdale, NH

    • drbillcorcoran May 3, 2016 at 11:42 am

      Mike,

      Thanks.

      The NRC (and INPO) continue to exclude competence, integrity, compliance, and transparency from their lists of safety culture traits. The industry continues to perform in such a way as to demonstrate shortfalls in competence, integrity, compliance, and transparency and thereby erode public trust and confidence, not only in the industry and its overseers, but also in the technology.

      Can you provide links to the sources of the facts in your posting?

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