As the eyes and ears of the NRC, resident inspectors never know when they might have to respond to an emergency at the plants they monitor. Fred Sanchez, Arkansas Nuclear One Senior Resident Inspector, was preparing to attend Easter services with his family when he got a call shortly before 8 a.m. Sunday informing him that a 600-ton component was dropped from a crane while being moved out of the turbine building at Unit 1.
He drove to the plant to survey the damage and phoned reports back to Region IV staff all day.
The industrial accident resulted in eight injuries and one fatality. Of the injured workers, six were treated and released from a local hospital; two remain hospitalized.
At the time of the event, Unit 1 was in a refueling outage with all of the fuel still in the reactor vessel, safely cooled. The accident damaged some electrical equipment that supplies off-site power to the plant. The plant’s emergency diesel generators started and power was quickly restored to the decay heat removal systems.
Unit 2, which was operating at full power, automatically shut down when power was lost to a reactor coolant pump due to electrical equipment that was damaged when the component fell. At 9:22 a.m. offsite power to one electrical bus was lost because water from a fire main broken by the falling component caused a short circuit. An emergency diesel generator started up and is supplying power to key safety systems. Unit 2 is cooling down using natural circulation.
Both plants are in stable shutdown condition. There was no radiological release or danger to the public.
Entergy Operations, Inc., which operates the plant, declared a Notice of Unusual Event, the lowest of four NRC emergency classifications, at 10:44 a.m. because the accident damaged some electrical equipment. The Unusual Event was terminated at 6:21 p.m. after the licensee took corrective actions to stabilize the plant’s power supplies.
Two additional inspectors have been dispatched to ANO to assist the resident inspectors and conduct follow-up reviews of the licensee’s response to the event. NRC’s Region IV also plans to conduct an inspection to review the circumstances contributing to the event.
61 thoughts on “Easter Sunday and Arkansas Nuclear One”
This job was critical path for the outage, so it was going to happen when everything in the schedule lined up.
why the stator dropped??
It is just terrible when disasters like this happen, especially so close to the holidays. I don’t think its good to harp on whose fault it was, but rather we should focus on how to avoid an event like this in the future. I work for a restoration company and if something goes wrong we try and focus on how we could change it rather than whose fault it was in the first place.
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Thanks, Victor – that makes sense. I understand why one should avoid using jargon, but reporters seem to have been fond of tossing SCRAM somewhere in their articles. The ones that still have jobs today are probably too young to have any idea what it means.
For what it’s worth, I wasn’t nitpicking on the inconsistent SCRAM code to imply that you or Entergy should do something about the event report – I was honestly confused. There really isn’t any point in Entergy fixing it now. There’s only (apparently) about six or seven of us that actually read them and no Entergy employees. Maybe they have the NRC web site blocked in their firewall?
Thanks for you reply, David. I heard this many times, but think I’ll stick with Tom Wellock’s version:
It’s not that I believe one hazy recollection over the other. I just find the first story’s premise – that Fermi would make up an acronym like this to shout – very hard to believe. Grad students clowning around? Yep – I’ll stick with that.
I suggest that SCRAM be reserved to Manually intiated human responses to WTFs going on. And only that. Automatic shutdown Rabot (international-sic) responses try Robotic instead sound much better and are fair/balanced reporting VS sensational none Seismic events.
Thanks for your Careful moderation. That could be a Boron joke but lets kNote go there. April fools was 04/01/13 in English or 01.04.2013 in Y2K Deutsch. I speak all three and sometime get MY acro_nyms or even dat(ah)s or DtC (NiST=DateCodes) mixed up. Sorry for too much info when or if Silence is the best option currently available. My FuSimy comnts are at WP=GLsword
FYI inforMation, more than likely the mini-seizmic event busted breaker mounts on switch gear at Elevtion 372 (none safety) and either that (loss of 4160/6900 3oAC) to the RCPs OR the main turbine vibration sensor probably intiated a full blown WTF response. Once the main “Christmas Tree” lights come on who cares whether A,B,C or Z#101 actually caused the trip. We are talking Milli and uMicroSeconds not even Minutes
I prefer “plunk go the rods”
We try to avoid use of the term SCRAM because it is jargon. Instead we usually say a reactor shut down automatically in a controlled fashion designed to protect equipment and public health and safety. Regarding Event Report 48869, you are correct and there is an error when it shows that Unit 2, which was critical and operating at full power, did not SCRAM as a result of the breaker malfunction. It did and the box should indicate a “Y” rather than an “N.” We’re notifying Entergy so they can fix the error. The box correctly shows a “Y” for RX CRIT indicating the reactor was critical at the time of the event.
The term SCRAM dates back to the beginnings of nuclear reactors and meant Shutdown Control Rod Ax Man because a man was literally stationed with an ax to cut the rope holding the control rod. The term carried over but the Ax Man didn’t. Several other terms are now also used such as Reactor Trip,and Automatic Shutdown, they mean the same thing. I’m not sure why we don’t use a standard term but it would be nice if we did to avoid confusion.
Victor – I noticed that the word ‘SCRAM’ was almost completely absent from media reports on the ANO accident. Media reports of ANO-2 automatically ‘shutting down’ from a breaker explosion without mentioning a SCRAM implies – to me – some kind of uncontrolled shutdown. I know that wasn’t the case and Unit 2 is now in Mode 3 – Hot Standby. I thought SCRAM had a pretty distinct meaning and was expecting to see it somewhere in media reports. The Event Report (48869) confuses me more when it states “…On Unit 2, all rods inserted during the trip…” but the SCRAM code is ‘N’ and RX CRIT is ‘Y’. If Unit 2 tripped, doesn’t that mean it has been SCRAMed and is no longer critical?
Has there been any change in the way NRC responds to media inquiries to avoid that term, or am I just confused about *what* it means?
Anonymous, excellent show of courage. You explained my point exactly. “The schedule” takes priority over everything. The culture of nuclear power has changed dramatically over my nuclear career. Scheduled outages have been reduced from 100 days to less than 30 days. Many of those changes I agree with. However, the disregard of a power greater than ourselves and the manipulation of people to accomplish these schedules is horrible to me. I am not saying that is what happened here. I truly do not know what happened here. I know a stator was dropped and people were hurt. One person was killed. I also know night-shift thought the lift was unsafe. Day-shift came in and tried the lift, the rest is history. Lets just say replacement power is 1 million dollars a day. How many days will this set the outage back? What will the lawsuit cost? How much is a life worth? I know my management and the management in other plants wants everyone to go home the way they came in. Would it hurt anything to acknowledge God and observe the holiday? At least put off enormous evolutions until all were thru the holiday. I have seen that done before. We even schedule planned outages around big holidays. It is better for our people and better for the plant.
R S — It was the old stator. It was only a week into the outage and things would have still been coming apart at this time. This was the critical path job for the outage, which WAS scheduled for just over a month’s duration.
Some references for class 1E power systems (vital power systems) in nuclear power plants: IEEE 384, separation criteria for class 1E power systems in nuclear power facilities. IEEE 308, standard for class 1E power systems in nuclear power facilities. IEEE 379, standard for application of single failure criteria to class 1E power systems.
As nuclear plants were designed to these standards, they may provide the insight you are looking for. Additionally, note that these are only for the class 1E power system. The non 1E power system (non-vital busses) don’t behave in this way.
Ultimate heat sink for PWRs can be the atmosphere. Natural circulation cooldown + auxiliary feed water implies that the atmosphere was being utilized as UHS. I know you don’t like hearing my knowledge, but I can say I’ve read nothing that suggests they lost UHS, and that based on what I’ve seen, they did cool the reactor down to mode 4 pretty quickly (which you wouldn’t opt to do w/out UHS)
If you would just read the local newspaper(s) and ask honest question instead of spouting non-sense, we would all be better informed. The “ultimate heat sink” either the emergency cooling pond or Lake Dardanelle are there and as long as there is diesel fuel NOTHING has been lost except the normal offsite shutdown power supply(ies).
Or more precisely -read the actual incident report as it was written and shown on this dot.gov portal- The connections between a triple redundant power grid outside the Unit and the fully functional and redundant safety supplies inside is broken. However EACH safety bus is being powered by its own diesel powered generator with enough fuel on site for at least a few month of shutdown cooling and safety related operations.
Now IF you have some information that contradicts THAT propoganda then lets hear it here. I do no longer work for Entergy or toe the NRC line. Obviously they allowed you to challenge their version of the facts. So go ahead challenge or better yet correct mine. All the information I have comes from public sources. If I was still a Licensed Reactor Operator (try Unit 2 back in the 1980s), I would probably be there doing my job.
Instead I am “following” this and keeping myself, neighbors and friends (who ask me questions) informed as best as I can. If for one second I thought there was a clear and present danger Id be packing my bags. But to the best of my knowledge all there is is a bunch of mangled garbage and it will take a week or so to get -the electric- traffic going again. In the mean time, you just sit tight, turn up the radio and let Entergy/NRC/OSHA do their jobs.
There is no loss to the “ultimate heat sink.” The service water pumps, on Unit 1, automatically restarted on restoration of power to the vital buses after the diesel generators automatically tied on to the buses. The service water system is cooling plant systems, including the decay heat removal systems and the spent fuel cooling system. At least, that’s the way it is designed to work and I’ve seen nothing that makes me think otherwise. (I don’t work for anyone, so have nothing vested in this, other than knowledge.)
The loss of power was to the non-vital electrical systems. The stator fell in the train bay, which is between the non-vital bus areas on both units, providing physical separation between the non-vital electrical buses. There are no interconnections between the electrical buses of the two units. Provisions are available to potentially supply one unit from the other under very unusual emergency conditions, but it takes specific operator actions to make that happen.
I’m reading this from the outside, just like everyone else. I haven’t been inside the plant for several years, but I’ve walked the areas this occurred in many,many times.
The plant is designed with separate electrical power systems to minimize the possibility that an accident at one plant would affect another. On Sunday, it was the physical impact of the 600-ton component that affected both units, not electrical interconnections. When the component fell on the turbine deck it damaged part of the electrical distribution system for Unit 1, causing a loss of offsite power for Unit 1. The crash of the stator was sensed by a reactor coolant pump for Unit 2, which protectively responded by shutting down, causing the reactor, which was operating at full power, to shut down.
In answer to your questions: Unit 1 is still using an emergency diesel generator; Unit 2 is not. Offsite power has been fully restored to Unit 2.
NRC resident inspectors, assisted by two additional inspectors sent to the site, are currently reviewing the event. Their findings will be documented in a quarterly inspection report. All NRC inspection reports are posted to the NRC web site at: http://www.nrc.gov/NRR/OVERSIGHT/ASSESS/listofrpts_body.html#wc
The Arkansas Tech Univ library is a federally funded repository for most microfiche/paper copies and reports. This blog site and/or the NRC Web site will likely have or link to online versions. The local papers (Russellville-Courier and Little Rock-Arkansas Democrat) usually provide adequate coverage so most people can find the stuff.
However, just like NTSB (National Transportation Safety Board) crash reports it may take years of research and pain staking reconstruction before We The People and our appointed officials can fully understand what went wrong.
Nice risk PR song and dance. You used the playbook line by line.
This really is sort of two problems. One being the industrial accident with the lift crane. The other being that the plant still has a loss of offsite power and apparently still a loss to the ultimate heat sink. Neither the NRC or Entergy are being up front or clear about the status of either of these situations. This is a problem and the public deserves clear answers.
These comments about Easter are perplexing. Outage work is done to a schedule, and the schedule is modified as the work progresses. So if the stator lift comes up on Easter sunday morning, that’s when the crew doing the lift will be there to do their work. It may be hard for regular 9 to 5’ers to understand, but some parts of our world (like making electricity) go on 24 – 7 and the people who work in these industries just do it.
I am a former worker at this place but not necessarily a blind nuclear advocate. Accidents of all types happen. Honest, hard working people drop torpedos on their own submarines and those weigh much less than 12 hundred-thousand pounds. Reading the open and reasonably fair press coverage of this incident, I am impressed by the plant operators (Entergy’s) response and willingness to be forth coming. The NRC is doing even better.
It is my assessment from all public accounts that there are some tough questions that must be asked … but there was and IS less danger to the public from this “Industrial Accident” than most 18 wheeler (only 80 thousand pounds mind you) accidents that happen along Interstate 40 from Memphis TN to Fort Smith AR.
Lets give these folks some room to breath, debrief and recover BEFORE drawing conclusions. If the radiation sirens go off, that is the time to duck and cover. And Fear or Panic should not in your minds even then. BTW: when was the last time you checked the batteries in your emergency weather radio?
“The NRC and the Occupational Safety & Health Administration will conduct inspections on this failure, which will be documented in inspection reports that will be made public in the future.”
Mr. Dricks, when these reports become available where can the public find them?
This job was critical path for the outage, so it was going to happen when everything in the schedule lined up.
Restoration of decay heat in 3 minutes and 50 seconds is a good thing. They had two different procedures that they had to implement at the same time to accomplish this: Loss of Decay Heat and Degraded Power. These guys had 1.2 MILLION pounds drop 40 feet to the train bay floor, and then all the lights in the control room except for emergency lighting went out until the diesel generators started and tied onto their respective buses. The last loss of offsite power at ANO was April and June of 1980. Both of those events involved both units and were caused by events away from the site. The sound of this event was heard by residents outside the exclusion area. I suspect it was extremely loud in the control room and that the operators felt the resultant shock.
That 1.2 million pounds, along with large pieces fell in a bay. From the pictures, I can see that there is structural damage just above that area.
I am a retired, previously licensed SRO on ANO Unit 1
Note: Some sensitive site-specific information deleted.
In looking at the various reports beyond the limited information the NRC has provided it seems that the electrical system for unit 2’s intakes was wired over on the #1 side, causing the loss of power on the #2 side and loss of the intake pumps. It a multi unit plant shouldn’t the power systems for each side of the turbine building be wired independently and ON that side of the building rather than passing both through one side of the turbine building? This mirrored and separate systems makes sense from a design and safety standpoint and appears to not have been the case, causing an additional problem on top of the accident.
Has power been restored to unit 2’s intakes yet? Yes or no?
When will offsite power be restored to both units? The public deserves some clear answers on these two issues. These seem to be the only outstanding safety related issues.
As others have mentioned this could have been worse. Someone asked me if the rail pit the stator fell into is on concrete slab? If this equipment had failed elsewhere it could have gone through multiple floors. I hope there are some follow up reports on this as more is found out about the extent of building damage etc.
The whole incident is very unfortunate and I am sure is very hard on those working at the plant but the failure seems to maybe just be one of those freak things that can happen.
My heart and prayers go out to the family members and the injured in this tragedy. It has been all long time since nuclear power plants regarded Easter and Christmas as sacred holidays. Maybe it is time. Greed is a poor reason to disregard them.
The classification was correct and the NRC will agree. I understand you thinking that in your “personal view” it is an elevated threat, but the risk analysis just doesn’t support it. The terminology used in the business…emergency power…natural circulation…lead the inexperienced to draw skewed pictures of the situation. The NRC is not required to oversee this type of activity, nor will they have any issue with it being classified as an UE. I have been a licensed Senior Reactor Operator on a similar plant, and assure you that this tragedy is an industrial accident. The damage to the electrical equipment did raise the risk of radiological issues but it was a very minimal change. The fact that it was on Easter Sunday is actually a good thing…fewer people were at the plant and this probably reduced the human loss. On a non-holiday, it is likely that more people would have been working near the stator’s path after the lifting equipment failed. As for the safety procedures and culture, that will be up to OSHA to investigate. This type of lift is a huge evolution. No doubt that many hours of planning went into it and that the right people were there. Many plants actually have an engineer on staff that specializes in heavy lifts.
I saw the same lift executed at another plant. the same type equipment was used (including the brand name on the lift equipment). sometimes, in the process of making these big equipment changes to a plant, a small decision can lead to catastrophic events. It’s quite sad that a loss of life has occurred. However, this event was on the BOP side of the house, not in the Reactor side. To say the plant was distressingly close to a meltdown is not well informed and making harsh assumptions, including sensationalism. The plant operators reacted in accordance with procedures and shut the running unit down. The diesel generators are a normal backup to off-site power, and while the risk was raised by reducing the redundant systems in operating the diesels, they performed as designed. I am sure the thorough investigation will reveal errors and industry will react to ensure it doesn’t happen again. It is a tragic loss and prayers go to the families of the victims. And hopefully the anti-nuke people will feel the same way.
Is there any update available? Some actual information would be useful. Does unit 2 have access to the ultimate heat sink? Has either unit been put back on grid power or are both all or partially being powered by the diesels?
Heavy lifts are scheduled to minimize the amount of people who could be travelling through/under (via other floors) the lift area and be affected. It is not done to bypass or prevent inspectors from being there. Could it be possible that this was scheduled when a hired contractor was available to move the equipment? It will be determined what happened by the regulators/ANO/contractor what happened/how it happened/ why it happened. Speculation is too far away from truth at this time.
I was there when it happened and there were so many things that could of prevented the accident.The previous shift started to do the lift and they didnt feel the load was safe to lift so day shift came in and evidently someone felt that it was ok to do it and you see what happened.I hope the people that was in charge of it pays for it cause the families are gonna suffer for the rest of their lives and this happened because of the almighty dollar.
As a bystander in all this, I hate to interrupt this highly technical person over this… cause he/she is quite humorious. But I need a technical question answered.
Question is: Was this a New stator being put in place or was it the old stator being removed that dropped. PS. My condolences go out to the families and all of those who work at ANO.
There are four levels of emergency event, each with their own criteria. The plant declared an Unusual Event because they believed an explosion had occurred in an electrical breaker supplying offsite power to plant safety systems at Unit 2, although this was later determined not to be the case. An explosion, however, is one of the criteria for an Unusual Event, thus the declaration.
The NRC and the Occupational Safety & Health Administration will conduct inspections on this failure, which will be documented in inspection reports that will be made public in the future.
It’s important to know the cooldown mode for a PWR. BWRs are fully capable of removing heat from the fuel without forced flow, but in PWRs a loss of forced flow can present many challenges. Even worse is a condition where natural circulation cannot be maintained and PORV cooling or some other varient is requried to ensure critical safety functions.
I agree saying “natural circulation” can be misleading to some people, but it is important technical information to know how heat is being transferred from the fuel to the ultimate heat sink.
event classifications are based on industry standards and regulations. The cause of the unusual event emergency classification was the degradation and loss of offsite power sources for greater than 15 minutes. A reactor scram on its own is not an emergency classification, neither is an industrial accident. These are industry standards.
Alex — You may well be right about application of the official NRC event classifications, but whenever you have two nuclear units relying on backup diesel power for cooling AND damaged fire protection and electrical system buses, you have an elevated threat to radiological safety. At least that is my personal view. Also, dropping a 600 ton stator suggests that all is not well with safety procedures at this plant, which suggests there may be broader plant safety culture issues that could contribute to elevated radiological risks given certain precursor events, like a fire, earthquake, or flood There are obviously a lot of unanswered questions. Moving a 600 ton stator on Easter Sunday, when the resident inspector and probably a lot of other key plant employees were attending services or taking the day off?? What was that about? Was the full complement of personnel, including plant safety personnel, prudently required for such an operation on duty at the plant on Easter Sunday? Why did the company choose to do it then? When it has all the facts, the NRC will presumably review whether the company’s minimal event declaration was the correct one.
This is going to sound like nonsense to you, but the “unusual event” classification is done through a process at every nuke plant, and not just this one. There is a prescribed series of questions and answers about plant status, and to the untrained eye this looks to be more serious than an “unusual event” but I ran the same details through the process at my nuke plant and got the same result. It is not about industrial safety that they make these classifications, but about radiological safety, which in this case was never really in jeopardy.
You must work for the power plant……dude
Who was the genius, scheduling the lift of the heaviest equipment on Easter Sunday? Who designed this operation? Was OSHA involved?
I am very interested to learn the root cause of this lift failure. We work so hard – checking, researching, questioning, and double checking – to prevent things like this from occurring. This might become something that college students learn about in the textbooks.
I just hope the families and people affected find some relief for the grief they must be feeling. What an unfortunate and sad event.
Let’s go over this one more time: a 600 ton-stator is dropped from a crane, leaving one worker dead, two hospitalized with injuries, and four “treated and released,” and in so doing it severs a fire main, shorting electrical electrical equipment and causing a loss of off-site power to both units, one of which was operating, and Entergy merely deems this an “Unusual Event,” the lowest of NRC’s four emergency classifications??? Come on, Entergy, get real! While the emergency diesels may have kicked in as designed, this was clearly a serious event and I suspect the NRC will find as much in its follow-up root-cause inspection. What if the fire suppression system had experienced wider damage and malfunctions, shorting the electrical system that distributes emergency diesel power? What then?
It is somewhat misleading to say that the unit 2 is cooling down using natural circulation. Actually the reactor coolant decay heat is being removed via the steam generators steam dumps to atmosphere which require the emergency feedwater pumps to provide water to the steam generators.
@ Phil Nasadowski
This is not a little event. This is a major event that will cost the utility $ millions to repair and provide replacement power generation. Unit 1 was not defueled – it was still in the reactor as the article says. The fuel still needs cooling when it is in the reactor vessel.
Starting diesel generators because of loss of offsite power (LOOP) puts the reactors in a vulnerable mode of operation.
“loss of decay heat removal on ANO Unit 1… was restored in 3 minutes and 50 seconds.”
That’s right Ace, another 10 seconds and Russellville would have been a smoking, permanently uninhabitable crater.
@Phil – agreed, except article says Unit 1 was not defueled, but still had fuel in vessel.
Do you understand how natural circulation works? Do you even care to find out?
The reactor is on natural circulation, but decay heat removal still requires injection via the aux feed system and heat removal via the atmospheric steam dumps.
Natural circulation simply refers to the ability of the reactor core to move heat to the steam generators without the reactor coolant pumps.
The loss of reactor coolant pumps implies the non-safety 6900V or 13kV bus was lost (and indirectly implies that the startup transformer for the unit locked out)
Nuclear power plants are designed to be single failure proof. Electrical systems are separated physically from other systems, and as such, the damage caused by a broken fire main is not capable of affecting multiple safety divisions of the class 1E power system.
As an aside from that, the safety related power busses are not located in the turbine building (where the water main broke). Turbine buildings are generally not built as seismic class 1E, and as such safety related power busses are not present in turbine building areas, and if they are it is within a separate sealed off section of the turbine building. It was most likely a non-safety divisional power bus that was damaged, causing a loss of normal power feed to a safety/class 1E divisional power bus and an automatic transfer to the emergency source. Many plants are designed with vertical bus arrangements like this where the non safety bus normally feeds power to the safety bus, and if the non-safety bus is damaged then the safety bus automatically disconnects and starts its respective diesel generator (which is what happened in the case of ANO).
Do you have any information on why the stator dropped?
My thoughts and prayers are with the coworkers and families of those involved. it is a sober reminder that radiation is not the only danger when working in the nuclear power industry and though we strive to do everything safely, things can still go wrong.
The 600-ton component (we’ve corrected the weight in the post) is a stator. It surrounds the spinning rotor within the main generator.
get over yourself dude, the first paragraph was just meant to contrast business as usual to these horrific events,
it was the stator
Distressingly close to a meltdown? You got to be kidding me… Please educate yourself before you make such ridiculous claims, But this is the type of comments you get from people who get their info from Greenpeace.
“Actually, we all know: Fukushima USA could have happened”
I know it’s fun for the anti-nukes that read this blog to pretend that every little thing that happens at a nuclear plant is the end of the world, but the reality is there was no danger: Unit 2 shut down as designed, the emergency generators both came on as designed, and the plant is cooling on convection (i.e. no pumps!), again, as designed. Unit 1 was defueled for an outage. There is, and was, no danger to the public.
The way this is written, the first two paragraphs are narcissistic and we are led to believe the worst part of this tragedy is that the NRC inspector missed Easter services. In fact this was a true cascade of terrifying events which came distressingly close to causing a meltdown. With a fire main broken and equipment short-circuiting, who knows what might have happened if things had gone just a little differently? Actually, we all know: Fukushima USA could have happened. One death is bad enough. Losing Arkansas was not far off.
500 t? Which equipment could that be?!
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