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Advanced Welding Techniques for Nuclear Power Plant Construction

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Mark Gino Aliperio's picture
Student Graduate KEPCO International Nuclear Graduate School

Nuclear Power Plant Engineer. In my study at KEPCO International Nuclear Graduate School in which I specialized in Project Management in Nuclear Power Plant (NPP) Construction, my team and I...

  • Member since 2020
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  • Jan 24, 2022

by Mark Gino Aliperio, BH Song, SH Jeong, UH Jang, E Akpoguma

Industrial technologies are evolving, and in construction, there is no exception. But the most recent developments extend beyond building equipment alone. In this 21st century, technological advancement is the order of the day. New approaches for construction are seen in the field. Such advancement in construction technologies are driving efficiencies which results to better-quality outcomes. With several nuclear power plants (NPPs) presently under construction worldwide, expectations are rising regarding the quality, cost and schedule associated with the construction of new NPPs. Worldwide experience in large construction projects, including NPP projects, has resulted in significant advancements in construction techniques and methods and this includes some Advanced Welding Techniques.

Conventional Welding Methods

The most common process applied in the construction of an NPP is the joining of material members by welding. The welding processes used in NPP construction include structural welds, used to connect structural members. Quality welding, crucial to the construction of NPPs, is time consuming. The time required is determined to a large extent by the achievable deposition rate of the weld material.

The completed process is examined to verify that the completed weldment is defect free. The welding process is subject to many variables. Various factors contribute to weld problems, and weld defects happen for a host of reasons.

The most common weld defects include: Lack of fusion; Lack of penetration or excess penetration; Excess penetration (burning through); Porosity; Inclusions; Cracking; Undercut; Lamellar tearing,

Goals of Advanced methods

Advanced welding techniques are focused on four goals:


  • Eliminating welds
  • Moving from field to shop
  • Automating the welding process
  • Increasing deposition welding rate and weld quality

Automatic and mechanized welding

The process of welding depends on a number of variables including environment, configuration, welder fatigue and embedded material contamination. The application of automation to the process helps reduce the fatigue and requirement for constant precision imparted by the welder. Advances in control technology have improved machine precision and reliability for automated welding equipment. In addition, the mechanized process enables larger amounts of weld metal to be deposited on an ongoing basis than a welder would typically be able to deliver.

Use of automatic welding equipment is effective in maintaining high quality and in improving the working environment when welding in narrow spaces. This is useful in getting defect free welds, thus avoiding job repetition, and resulting in savings in time and cost.

Field Application

1. Reactor Coolant Piping Automatic Weld, Shin-Kori 1, South Korea

For the reactor coolant loop (RCL) piping welding, a narrow gap automatic welding method has been used at the Shin-Kori 1 and 2 sites in the Republic of Korea. Contributing factors to rising construction costs have been manual welding, with its average defect rate of 3–5% (higher than that of automatic welding), and a limited availability of qualified welders. A narrow gap welding technique enables the welding time to be shortened, as the welding cross-sectional area is reduced, and provides effective control of precision fabrication by preventing physical deformation of the weldment as weld deposit is reduced. It shows a composite view comparing the narrow gap welding technique with the weld preparation configuration of conventional welding.

Application of a narrow gap automated welding process, instead of manual welding, to the RCL piping where precision technique is mandated would not only enhance welding quality with its consistency throughout the welding, but also shorten the construction schedule by 1.5 months. Such automated welding equipment is available in a variety of sizes and weld techniques, and can also be customized to meet specific needs. Precision welding of reactor coolant piping is managed by computerized control as part of the automated welding machine.

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2. Kashiwazaki-Kariwa, Japan

The automatic welding method was applied to Reinforced Concrete Containment Vessel (RCCV) liners, large and small bore piping, instrumental piping, Reactor Pressure Vessel (RPV) nozzles, etc. The automatic welding ratio was achieved to 98% for RCCV liners, 60% for the large bore piping in the Reactor Building and 35% for the large bore piping in the turbine building.

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This work is part of the project report KINGS/PR-PEP02-2018-08 "Advanced Construction Technologies" by the Project Engineer Program II Laboratory of KEPCO International Nuclear Graduate School Class of 2019.

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Bob Meinetz's picture
Bob Meinetz on Jan 24, 2022

Mark, with the capability to build gigawatt-scaled nuclear plants limited to the two or three companies in the U.S. (unnamed here), poor oversight by the Nuclear Regulatory Commission and no incentive to keep costs low have led to dramatic cost overruns - leaving utility shareholders uneasy about buying in. A few startups are developing Small Modular Reactors (SMRs), to reduce cost and perceived risk for investors, by reducing size.

But there can be no doubt that large-capacity nuclear and its corresponding economies of scale are to the benefit of electricity customers. With substantial government support for developing technologies like narrow-gap automated welding, China, Korea, Russia, and France are poised to dominate large-scale nuclear. It will have dramatic implications for geopolitical influence in coming years.

Is anyone in DC paying attention? I don't know, but if U.S. politicians believe large nuclear is too expensive to warrant public investment, it's a bargain compared to the ultimate price we will pay in indifference.

Jim Stack's picture
Jim Stack on Jan 24, 2022

It will take more than improved welding to save the Nuclear industry. It is still the most expensive power ever made. It is the most dangerous . Uranium is a finite elements that no one wants to mine.  

Bob Meinetz's picture
Bob Meinetz on Jan 25, 2022

Jim, repeating these falsehoods ad infinitum will never make them true. Others who have been frightened by nuclear energy often discover they've been harboring misperceptions, sometimes for decades, that simply aren't accurate.
You might want to consider asking questions, rather than retreating into a shell of denial, and learning more about the subject. Knowledge is power.

Richard Nielsen's picture
Richard Nielsen on Feb 4, 2022

Advanced welding techniques offer benefits to many of us and we are very excited to explore them. In my opinion that will not save the nuclear industry, fear, politics, price gouging, and ignorance have hampered it for many years, not to mention the absolute disastrous approach companies have taken towards building new plants. I agree with Bob.

Bob Meinetz's picture
Bob Meinetz on Feb 8, 2022

What is the "absolute disastrous" approach companies have taken towards building new nuclear plants, Richard? Like most major infrastructure projects, they're late and over budget. That's expected.

Vogtle units 3-4 will be online in 2023, ten years after the start of construction, and will deliver over 2.2 billion watts of reliable electricity to customers in the Southeastern U.S. Per unit of energy, that's a faster build than any other power plant in U.S. history. Vogtle will then be the largest nuclear plant in the country, producing more clean energy than all solar and wind east of the Mississippi.

Richard Nielsen's picture
Richard Nielsen on Feb 9, 2022

That's my point. What happens to stability when a unit that large trips? Or has a generator issue and frequency issues? It trips everything else on the system. The amount of money needed to build those very units you mentioned is incredible. I am a huge fan of nuclear technology. The method companies have chosen to go about it and the number of proposed, canceled or started and canceled are very telling.  

Bob Meinetz's picture
Bob Meinetz on Feb 9, 2022

Richard, at last count the NRC had recorded 34 unscheduled trips of U.S. power reactors since 1990. For each reactor, that's an average of one every 94 years (needless to say, some have never experienced unscheduled trips). U.S. nuclear plants, with capacity factors often exceeding 100%, are - by far - the most reliable sources of electricity in the U.S.

At nuclear and other steam generation plants, AC electricity is generated by using turbines to turn wheels, with 12 huge magnets mounted on them, rotating at 15 RPM. Their speed is precisely controlled by electronic means to generate three-phase alternating current at 60 RPM. When there are frequency issues on the grid it is never caused by plants with this configuration - they serve as the bedrock of grid electricity. In the last decade, they have always been caused by the headache of attempting to synchronize millions of independent inverters at solar sources, and thousands of wind turbines spinning uncontrollably. 

Solar and wind are the problem, not the solution. And yes, nuclear plants are expensive, but they're worth every penny. California has been experiencing reliability problems ever since the shutdown of San Onofre in 2013, and they will only get worse if Diablo Canyon is shut down in 2025.

Re: cancellations, you might be surprised to learn that closing nuclear plants is a big business. Why? Compared to alternatives, they're too reliable.

Richard Nielsen's picture
Richard Nielsen on Feb 10, 2022

Bob, I did not need the class on how Generation works, by the way I also know how generator poles work, and have torn more turbine-gen sets apart then I care to remember.  I also understand the kunundrom with wind and solar.  The question is what happens to all the other generators on that section of the grid when 1600 MW's 'wags' its tail.  Its a rhetorical question because I have seen it, it tends to trip every other small generator on that system.  Here is a real question for you, is this new behemoth of Vogtles 'black plant' capable?

Bob Meinetz's picture
Bob Meinetz on Feb 10, 2022

"Its a rhetorical question because I have seen it, it tends to trip every other small generator on that system."

When/where did you see the unscheduled trip of a nuclear power reactor, Richard?

"The question is what happens to all the other generators on that section of the grid when 1600 MW's 'wags' its tail."

The AP 1000s at Vogtle are rated at 1,113 MWe, so the monster wagging its tail you're imagining is 44% larger than life (to the best of my knowledge, no nuclear reactor in the world is capable of generating 1,600 MWe).

"Here is a real question for you, is this new behemoth of Vogtles 'black plant' capable?"

I don't know what color Southern Company is planning to paint their new behemoths, but perhaps you were referring to black start capability. If so, the likelihood of all four units at Vogtle going out at once is next to nil - so a black start at Vogtle would, practically speaking, never be necessary.

If you have any other real questions I'll do my best to answer them.

Richard Nielsen's picture
Richard Nielsen on Feb 14, 2022

For someone as educated as you are, you seem very ignorant of the terminology we use. Black Plant has nothing to do with color, it has to do with whether or not it can start up under its own power. The answer is obviously no.  Any plant larger than all others in its region is a danger to all others when it trips.  I assume you are unaware of how the grid actually works. Black start, black plant, same same.  The likelihood of all four units being down at once is next to nil.... Right... because we have not ever lost entire sections of the grid at one time, for one reason or another.... wow.

Bob Meinetz's picture
Bob Meinetz on Feb 14, 2022

Again, when/where - specifically - did you see the unscheduled trip of a nuclear power reactor, Richard? Because you can't answer that question I have to assume you haven't, in fact, seen one. Maybe you were too busy imagining 1,600 MW monsters wagging their tails.

Or possibly you've forgotten it - like the term "black start". At least you didn't write "black out", or "black swan" - that would have been really embarrassing!

Joe Deely's picture
Joe Deely on Feb 10, 2022

Vogtle will then be the largest nuclear plant in the country, producing more clean energy than all solar and wind east of the Mississippi.

Hilarious... forget about East of the Mississippi and let's forget about wind - let's just focus on solar in the South Atlantic region of EIA reporting. (Delaware, DC, FL, GA, MD, NC,SC, VA and WVA) 


YTD (2021) in this region solar is up by about 9TWh vs. last year.(below is YTD thru Nov)

Solar in this region should end the year 2021 at about 35TWh - almost twice what current two reactors at Vogtle produce.


The 9 TWh of solar generation added in the South Atlantic in 2021 is basically equivalent to generation from one of the new reactors at Vogtle. But instead of taking 10 years this region is adding that much new zero-carbon solar generation every year.


By the way, another 5GW of utility scale solar scheduled to come online before end of 2022 in this region. 


Hell, with just a little effort GA alone could add a "reactors worth" of zero carbon solar generation every 3-4 years. 



Bob Meinetz's picture
Bob Meinetz on Feb 10, 2022

Hate to spoil your hilarity with reality, Joe, but by 2023 there will be four units at Vogtle, not two - and Southern Company is already making plans to build two more.

Units 1 and 2 at Vogtle have been displacing coal in the Southeast since the late 1980s, just a few years after Ron Reagan took Jimmy Carter's solar panels down from the roof of the White House. It seems cleaning up the water they were leaking was using more energy than they were generating. But they were only warming up the water in the White House kitchen a bit, on sunny days. Like other solar, it was all for show.

Since 1989, Units 1 and 2 at Vogtle have generated more than 800 TWh of electricity. When do you expect wind and solar in the U.S. to catch up with nuclear, not in a disingenuous "capacity" comparison, but in total generation? Better be soon, because when Units 3-4 come online solar and wind will be losing ground..and fast!

Joe Deely's picture
Joe Deely on Feb 11, 2022

Here's the reality Bob. You said:

Vogtle will then be the largest nuclear plant in the country, producing more clean energy than all solar and wind east of the Mississippi.

I showed that as usual you are wrong. In fact, a single region east of the Mississippi produces more clean energy with solar than Vogtle produces. 


I'm happy that the two Vogtle reactors will finally come online over the next couple of years and help renewables as they continue to shutdown coal in the SouthEast. 


Perhaps in 2024 Vogtle will generate about 36 TWh for the full year. That will be the equivalent of what solar did in EIAs South Atlantic region in 2021. However, by 2024 that region will have passed 60 TWh of solar generation - far surpassing Vogtle.


Again Bob, time to wake up and see where things are now vs 2010.



Bob Meinetz's picture
Bob Meinetz on Feb 11, 2022

Joe, we've all seen your homemade graphs with solar racing towards the sky, but you'll have to provide a link - one with EIA doing the graph drawing. You've been caught "fudging" data recently, so you have some work to do regaining trust around here (btw, the blue line in your graph will soon be twice as high - you're only showing output from Units 1 & 2). Thanks.

Joe Deely's picture
Joe Deely on Feb 12, 2022

Vogtle will then be the largest nuclear plant in the country, producing more clean energy than all solar and wind east of the Mississippi.

One more for you - to continue to emphasize the idiocy of the above statement. This time I'll give something closer to your hometown and I'll even do the EIA graph for you.  


Below we have wind in East North Central region over the last 10 years - as you say "racing towards the sky". This region is composed of Wisconsin, Illinois, Indiana, Michigan and Ohio.


33.3 TWh of wind in 2020. What about 2021?  YTD(thru Nov) wind is up about 4.5 TWh in this region. That brings us to about 38 TWh of wind in 2021 - or twice the output of Vogtle. Interestingly, the 4.5 TWh single year increase in zero carbon generation is equal to about 1/2 of a new nuclear reactor.  Not bad.

Bob Meinetz's picture
Bob Meinetz on Feb 11, 2022

Joe, for the benefit of readers who sometimes use electricity after the sun goes down,
I came across this graph which I thought would help get the point across. Why would anyone waste their money on electricity that could only be used during the day?

Joe Deely's picture
Joe Deely on Feb 12, 2022


Typical comeback for you.  You're proven wrong  - so you try to change the subject and make some cute remark to divert attention from your mistake.  The readers on this site know your MO.


However, since you are the one saying this - it has to be wrong- so let's do a little digging. Below is your comment and chart.

Why would anyone waste their money on electricity that could only be used during the day?

You've got zero generation for nuclear in South Atlantic from 6pm to 6am over the last 10 years. 

However, if I look at realtime generation info - only for Southern Company -  from EIA for 7pm on 06/10/2020 I see the following. 1,334 MW of solar at 7pm - not zero Bob. Wrong yet again. 

As per usual, this is only where the puck is now. Southern Co and the rest of the SouthEast are investing in battery storage so that plenty more of that solar can "move to" nighttime hours.

Form Energy announces partnership with Georgia Power to test 100-hour iron-air battery

  • Georgia Power will collaborate with Massachusetts-based startup Form Energy to deploy an energy storage project of up to 15 MW/1500 MWh using a novel iron-air-exchange flow battery technology, the companies said Wednesday. 
  • Georgia Power's three-year IRP detailed plans to retire its coal capacity by 2028 and add 2,300 MW of solar generation over the next three years. In all, the utility said it would add up to 6,000 MW of renewable generation by 2035, coupled with a massive increase in energy storage. The company has begun work on the 65 MW/260 MWh Mossy Branch Battery facility with an aim to achieve commercial operation in the fall of 2023 and has also done site development tests to install 265 MW/530 MWh of lithium-ion battery capacity at the McGrau Ford substation north of Atlanta. 

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