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.

 

Author: Moderator

Public Affairs Officer for the U.S. Nuclear Regulatory Commission

23 thoughts on “An Outage Twist: Degraded bolts at New York Nuclear Plant Warrant Attention”

  1. 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.

  2. 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

  3. 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!

  4. ***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.
    .

  5. 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

  6. 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?

  7. 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

  8. You know you hit the right tone when you cold call the NY Department of Public Service to make a complaint…they call you back in the same day. Within hours. In the discussion are three people including a lawyer named Brandon Goodrich. I was shocked with the state’s interest. At least they listened to my pitch and took me seriously.

    http://steamshovel2002.blogspot.com/2016/05/indian-point-its-core-components-highly.html
    “Indian Point: Its Core Components Highly Irradiated Differential Of Expansion, Stupid”

    Basically I am asking for the whole Baffle Reformer to be replaced. NY admitted they have issues with not just the bolts, but also the Baffle-Reformer. The group agreed that the Baffle Reformer needs to be replaced.

    The NRC is seriously defective in that they aren’t required to release all inspection results and documentation before Indian Point 2 start-up. Europe releases all regulatory inspection results before plant start-up in this grossly unexspected problem? We think not releasing all documents before start-up is a scam to not replace the dangerous Baffle Reformer this outage. The best result from you guys will go post start-up something like this; we scheduled the Baffle- Reformer job two outages from now.

    Honestly. I throught were the most open… the best… democracy in the western world.

    ***“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

    Response of PWR Baffle-Former Bolt Loading to Swelling, Irradiation Creep and Bolt Replacement as Revealed Using Finite Element Modeling

    Abstract
    Baffle-former bolts in pressurized water reactors (PWRs) tend to degrade with aging, partially due to radiation-induced hardening and also due to the often complex stress history of the bolt in response to time-dependent and spatial gradients in temperature and neutron flux-spectra that can alter the stress distribution of the bolts. The time-integrated stresses must play some role in bolt cracking, however, and therefore it is of interest to study the time dependence of bolt stresses even for idealized cases. These stresses have been quantified in the present analysis using newly developed material constitutive equations for swelling and creep at light-water reactor (LWR)-relevant temperatures and dose rates. ABAQUS finite element calculations demonstrate that irradiation creep in the absence of void swelling tends to relax bolt tension before 10 dpa. Subsequent differential swelling leads to an increase in bolt tension, but only to stresses below the yield strength and usually below the initial bolt loading. Various assumed bolt replacement scenarios are considered.

    Conclusions

    An FEA and constitutive equation approach quantified bolt stresses in a PWR baffle-former assembly. Spatial variation intemperature and dose affect the calculated stresses. Maximum stress occurs at the corner of the bolt head and bolt shank and is at the same location for occurrence of IASCC. Irradiation creep relaxes bolt shank stresses, whereas irradiation-induced swelling promotes bolt loading. Differential swelling rates between 304SSplates and 316SS bolts cause increase in bolt tension. The bolt remains in tension throughout life and reaches a minimum at 10 y of irradiation. Calculations of bolt replacement options indicate that end-of-life stress is greater for bolt replacement when compared to no bolt replacement.

    Response of PWR Baffle-Former Bolt Loading to Swelling, Irradiation Creep and Bolt Replacement as Revealed Using Finite Element Modeling (PDF Download Available). Available from: https://www.researchgate.net/publication/258883539_Response_of_PWR_Baffle-Former_Bolt_Loading_to_Swelling_Irradiation_Creep_and_Bolt_Replacement_as_Revealed_Using_Finite_Element_Modeling [accessed May 1, 2016].

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

    Mike Mulligan
    Hinsdale, NH

  9. It is too soon to say whether the missing boltheads will be recovered. It would be preferable if they can be located and removed. If not, Entergy will have to do a loose parts analysis regarding whether the boltheads, which came loose from a pair of 2-inch-long bolts, would be expected to have any impact on reactor operations. There is currently no data base that compiles data on missing boltheads.

    Our inspectors will be following up to check whether the plant’s loose parts monitoring system picked up any indications of the boltheads. We do not know the answer to that at this point.

    Neil Sheehan

  10. So how likely is it that bolt heads go missing? How many other reactors have had a similar thing occur and how long did it take to discover the problem and then repair it?

    Should they have triggered the Dings and Dents alarms?

    San Onofre’s operators ignored their alarm signals and now it is being decommissioned to coverup SCE’s engineering and operational debacle which will cost ratepayers many billions!

  11. Baffle jetting really refers to baffle plate creep. Radiation causes the plate to swell, shrink or bend leading to the excess space between the plates more than core design…the gap to increase. It is a serious core design defect not knowing how the plate will respond to heavy duty radiation. A gap in knowledge. Neil only told a selective part of the story. What is the function of the baffle plant gap? I believe it facilities core reflood during a LOCA. The term “baffle jetting” refers to serious core damage and the preventable release of massive amounts of radiation/contamination in the core, throughout the plant and some escaping the plant. The so called solution to baffle jetting is reversing the flow (upflow job)….but this only facilitates the problem. Baffle jetting, core damage and baffle creep is a old well known phenomena. The good guys don’t have these problems.

    Baffle jetting refers to the excess flow through the baffle plate edge space beyond design impinging on the nearest fuel pins. It causes the pins to spin around in the fuel assemble grid wearing through the cladding. The pins begin leaking, there begins a nasty corrosive process called secondary degradation. This will eat away tremendous amounts cladding leading to the pellets falling out of the pins. The cladding now has fast acting irreversible cancer. The pellets and pins corrosion leaves core debris circulating in the coolant…they find this debris at the bottom of the core.

    Outsiders don’t realized this Indian Point baffle plate bolt problem and the “water jetting” core damage at North Anna in 2014 are closely related. North Anna had notorious multiple water jetting events in the distance past. Believe me, the Indian Point baffle bolt problem could get a lot worst if the NRC discloses there was some not declared water jetting damage to the fuel pins (fuel leak). North Anna in the 2012 thought they had a fuel pin leak caused by some unknown debris circulating in the coolant. This is how spotty these normal core inspection are. Next outage they discovered the eye popping core damage. That first leak occurred around the unknown baffle jetting or they intentionally ignored it to the next outage. Dominion was negligent with not preventing this very costly core damage. No wonder why these guys can’t make money.

    ThrowBack Friday: Why did North Anna unit 2 in 2014 have water jetting core damage while unit 1 showed no such damage? Unit 1 got the upflow job years ago because of serous core fuel damage, while unit 2 did not? Generically the pins that failed in water jetting have gone through the core three times. Sometimes when plants have fuel damage through water jetting, the utility removes the damages pins and replace them with dummy pins (no uranium in them ).

    I got a few more articles on North Anna too.

    http://steamshovel2002.blogspot.com/2014/10/north-anna-has-15-million-fuel-pellets.html
    ‘North Anna Has 15 Million Fuel Pellets update’

    https://adamswebsearch2.nrc.gov/webSearch2/view?AccessionNumber=ML14325A692
    ‘LER 2014-002-00’

    http://steamshovel2002.blogspot.com/2014/12/dominions-intentionally-running-their.html
    ‘(North Anna) Dominion’s Intentionally Running Their Nuclear Reactor to Failure Philosophy’

  12. Baffle “jetting” refers to the flow of reactor coolant through gaps between adjacent baffle plates. If a large enough number of baffle bolts were to fail, this condition could occur and it could result in damage to adjoining fuel in the reactor core. Degraded baffle-former bolts have been identified at Indian Point 2 and are being replaced. In this case, that degradation can take the form of an indication of cracking. No failed bolts have been identified, though two boltheads are missing. There has been no damage to fuel observed in the reactor. We do not have immediate information on whether there is any damaged fuel from past operations at the plant.

    Neil Sheehan

  13. Baffle-former Assembly – Baffle-former Bolts (4-9 and 4-10)
    The baffle-former bolts attach the baffle plates to the baffle formers. Documented observations of IASCC cracking of these components exists in multiple designs in the PWR fleet worldwide. These highly irradiated bolts perform a critical safety and operational function in the plant. Loss of a single bolt or isolated multiple failures of the baffle-former bolts are considered to be manageable, but a catastrophic or clustered loss of multiple bolts at adjacent locations could cause a lack of structural stability and potentially raise safety and operational concerns.
    http://www.nrc.gov/docs/ML1522/ML15222A836.pdf

    4/28/16 “The number of degraded baffle-former bolts was the largest seen to date at a U.S. reactor,” the NRC said on Wednesday.
    http://www.capitalnewyork.com/article/albany/2016/04/8597822/regulator-says-faulty-bolts-indian-point-most-ever-seen

    Can missing bolts contribute to baffle jetting?
    Has there been an increase in damaged fuel?
    How many damaged fuel rods are being stored at Indian Point.

  14. Thank you Neil for your work. As a Westchester County resident I look forward to many more years of safe clean energy from the IPEC reactors.

  15. The NRC will perform independent analyses and on-site inspections to verify that Entergy has properly completed the replacement of all degraded bolts to ensure the Indian Point Unit 2 baffle-former structure will continue to function as designed. If any parts cannot be accounted for, our inspectors will ensure Entergy completes comprehensive technical analyses to ensure safety will be maintained. Our inspectors will also critically inspect Entergy’s evaluations, as they become available, regarding the condition of the removed bolts, the results of any subsequent examinations and metallurgical tests, and Entergy’s conclusions as to the causes of the problems. The NRC will assess the adequacy of Entergy’s planned and completed corrective actions. The NRC will further review Entergy’s evaluations regarding the applicability of this information to Indian Point Unit 3.

    NRC inspector lines of questioning will focus on safety, namely the capability of the baffle-former assembly to structurally respond to conditions ranging from normal operation to accident scenarios. The scope of NRC inspections and conclusions will be documented in reports that will be made publicly available.

    Neil Sheehan

  16. Here you can see the folly of the NRC. In all of our government in general though crooked political campaign contributions. You think doing the national interest (altruism) is dragging your feet into following all the voluntary codes and rules or NRC rules? We will voluntarily rule it to death so we justify not doing anything and spending money. Following the endless codes and rules is the ends of life independent of results, not preventing core bolt failure independent any rules, codes or outside force. We are not too far from the rules preventing the detection of broken bolts in the core. Using rules and laws to protect the law breakers instead of our good people. We once used codes and laws to make the bad guys meet the ends of society and bring about a orderly society. Now we are using regulations and laws extensively into blinding the on scene federal inspectors. Next we will removing the guns from all our police and military in the name of faux altruism. We are using rules, laws and government itself to blind the NRC resident inspectors instead of controlling the bad guys.

    I guess we live in the times where “black hole” organizations up and down the chain use triumphalism when things go wrong. We are always the heroes in our eyes independent of a orderly society, instead of charging them with gross negligence, incompetence…

    I thought the NRC and Entergy in relicensing by River Keeper, among others, forced Indian Point into doing the inspection. One only wonders when this would have been discovered if it wasn’t a relicensing contention. It wasn’t a voluntary inspection and the voluntary code boys didn’t force anyone hands. It was just rule and voluntary codes churning leading to infinity.

    I keep thinking about my Palisades 2.206 where the primary coolant pump impeller blades were getting flung off by vibrations. They ignoring the requirements and a big blade getting stuck in the core. It is still there, it is stuck in the core. It took impeller blade debris discovered in the core during a inspection before they cared to worry about it multiple times. For decades. And the Salem multiple primary coolant pump missing bolts, indeed multiple plants, and more errant foreign debris found in the core. What a waste of money? A fool would know all this is unsafe in many aspects. What should worry you most, these plants were running totally out of control and without complete knowledge and complete situational awareness for many years and decades. Laws, Rules and codes all clearly facilitated these behaviors and the building incomplete knowledge.

    Who does organizations and governments really serve…does policies, laws, rules and codes really serve a orderly society?

    Mike Mulligan
    Hinsdale, NH

  17. What were the circumstances of the “over 8700” bolts Areva has replaced? How many other bolts have been replaced? What were the circumstances?

  18. Yet another “safety first” at the Indian Point site in the backyard of NYC! It has to be another one of Murphy’s infamous laws that a nuke site with one of the world’s worst safety records has to be located in the backyard of one of the world’s largest cities! It is incomprehensible to think that the NRC is seriously considering renewing the license of these units.

  19. This is a well-written summary. However, I anticipate that nuclear power plant opponents will exaggerate risks. Here is a short 2:33 video from Areva that outlines the baffle bolt inspection and replacement process. https://youtu.be/fR-lVJUcbtY

  20. How would the reactor have responded to any and all design basis events, including loss of coolant accidents (LOCAs) and Steam Line Breaks (SLBs), if one had occurred just before the plant shutdown for the core former inspection?

    How will the NRC develop lines of inquiry?

    How will Entergy develop lines of inquiry?

    What are the failure modes? Did all of the failed bolts fail the same way?

    What are the results of the metallographic examinations and tests? Were they all the same?

    What is the time distribution of the failures?

    What are the conditions, behaviors, actions, and inactions that resulted in the failures not being manifested before 2016?

    Were there any alarms from the Metal Impact Monitoring System (MIMS)?

    Were there any abnormal conditions that could be seen on any instrumentation and/or recordings?

    What are the results of a careful inventory accounting of all of the bolts, bolt pieces, bolt fragments, fasteners, etc to nail down exactly what foreign material is going to be still inside the reactor coolant system?

    (Even temporarily trapped material can be freed by mechanical, hydraulic, or other perturbations/ shocks to the system, in which case the foreign material can damage important equipment including steam generator tubes and fuel cladding.)

    Did the Metal Impact Monitoring System (MIMS) detect any of the pieces from broken bolts?
    If so, how did workers evaluate the quite valuable advice it provided?
    If not, should it have detected the impacts from the metal pieces?

    What are the other U.S. reactors that have bolts and similar fasteners inside the reactor coolant pressure boundary?

    What are the other questions and lines of inquiry?

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