10 Aug The World’s Largest Movable Structure You’ve Probably Never Heard About
“It is the mark of a truly intelligent person to be moved by statistics,” George Bernard Shaw
So let’s start with the numbers:
Weight: 40,000 tons. Roughly the weight of 3 Eiffel Towers, 107 fully loaded 747s or the USS Missouri battleship.
Height: 590 feet tall. Roughly the height of the Seattle Space Needle or the Washington Monument.
Length: 530 feet long. Roughly one and a half football fields.
Design Life: 100 years. Roughly how long my wife thinks it will take for me to pay attention when she’s talking.
Environment: Designed to withstand temps between -45F and 113F and winds up to a class 3 tornado, 206 MPH – calculated at a once-in-a-million-year event. And a 5.4 magnitude earthquake, a one-in-ten-thousand-year-event.
Cost: $2.3 billion contributed from more than 40 nations.
It’s called The New Safe Confinement (NSC) and picture a massive, movable hanger-like dome designed to cover the highly radioactive disaster which is Chernobyl, in Ukraine.
Going back to the numbers, Chernobyl remains the single worst disaster in history. On April 26th, 1986 plant operators were conducting a test on an emergency water cooling system. At around 1:30 in the morning, pressure in the reactor built up and exploded, lifting and destroying the 1,000-ton concrete lid covering the reactor and spreading radioactive dust, well, everywhere.
Dozens of people died within the first few days and depending on who you read, it’s estimated that between 10,000 and 100,000 have died over the years from exposure and another 70,000 have varying degrees of disabilities. It released more than 100 times more radioactivity than both atomic bombs dropped on Nagasaki and Hiroshima.
Let’s just say April 26th 1986 was a very, very bad day for those working at, and living around, the facility.
The Soviet Union (back in the day) hastily built a concrete and steel containment structure called the Object Shelter to try and stem the continuous release of radioactivity. The shelter, however, continues to succumb to the environment and our collective nemesis, corrosion, and there is considerable concern that it might fail or collapse completely.
Hench the development of the NSC.
So, how does this fit in with a blog about corrosion fundamentals? Well, I’m a self-confirmed corrosion nerd, and when I first heard about the NSC being built around 2011, I was fascinated.
How do you build something so big, designed to last for 100 years, and corrosion protect it? This is what I do every day for our clients. I try to figure out creative, technically sound, vendor-neutral systems and practices for corrosion mitigation.
Anyone trying to corrosion protect anything gets pulled by vendors who firmly believe that their systems and ideas are best. If you talk to a paint company, they’ll tell you to paint it. Talk to a metallizing company, and TSA is the way to go. Talk to cathodic protection company, and that’s the ticket. And so on.
However, while coatings are the most prominent solution to most corrosion issues, they are never our first choice. Why? Because the second you install a coating system, you’ve created a maintenance issue. Now, we’ve designed coating systems with an estimated service life in excess of 100 years. However, at some point, virtually all painted or coated surfaces and assets will require maintenance.
Just yesterday I was consulting with a large oil company in Europe about a 1.2 million gallon, concrete waste water tank. The tank was built about 15 years ago, and started to leak. This was anticipated, and the plan was to keep crack-injecting it (chasing the cracks) until it stopped leaking. And, after several years, the tank is now watertight.
They contacted our firm because they were going inside to inspect it for the first time, and were considering lining the interior. They wanted me to review the coating options presented to them by a variety of vendors and coating companies.
The coating options were mediocre, and some were unsuitable, but my first question was why are you going to do anything to the interior?
The liquid stored inside the tank was not erosive to the concrete. There was no indication that rebar was being attacked. There was no evidence of any issues with the vapor-space. And the tank was no longer leaking.
While coatings are one of the tools in our toolbox, I saw no technical justification to do anything on the tank interior, unless there was a technical reason to do so once tank entry was made.
And I was interested to see what solutions engineers would come up with for the NSC.
And the technical solutions did not disappoint.
First, let’s understand how the dome works. It was built in two sections roughly 200 yards away from the Object Shelter (due to the radiation at the site itself) and then slid roughly 330 yards into place. This was done twice, once for each half. An added fascinating fact (for fellow nerdlings) is that the jacks used to raise and move the dome are the same ones that were used to raise the Russian submarine Kursk from the bottom of the Barents Sea (354 feet below the waves) in 2001. For those that don’t recall, the Kursk was an ill-fated nuclear Russian sub which sank, killing the entire crew of 118.
The dome has a 13-yard annular space, as is often the case with large domed-structures. I’ve walked inside the annular spaces of both the Duomo in Florence, Italy and at the Vatican, St. Peter’s Basilica’s Dome. It’s a common means of making structures like this, and allows for interior maintenance.
However, the NSC is designed to contain a nuclear waste pile which is still actively giving off radioactive contamination, and will do so for decades.
The entire goal of the NSC is to contain radioactivity emanating mostly in the form of dust particles.
From a corrosion perspective, there are three surfaces and environments which require consideration:
- The primary containment surface, which, you would see if you were looking up at the dome from ground-level.
- Interior of the annular space (and associated supporting structures).
- The exterior shell, which is exposed to the elements.
A. PRIMARY CONTAINMENT SURFACE:
This surface is designed to resist corrosion for 100 years, and, further, also has to hold the framework for two interior construction cranes, each able to lift and move more than 50 tons.
To solve the problem, the interior containment was made of 95,000 square yards of type 304 stainless steel, which is the most common form of stainless steel used worldwide. The 20-mil thick plates are tightly fitted to a galvanized deck with no ribbing or other modifications to the surface, to minimize the likelihood of radioactive dust clinging to the surface. The annealed stainless steel panels were sealed with tape and radioactive-resistant silicone to maintain an airtight space within the dome.
Sadly, I was not able to find application details, which would be interesting, as would the QC that went into the erection.
B. INTERIOR OF THE ANNULAR SPACE
The massive 33’ annular space is a complex web of carbon steel supports, beams and structures, all painted to reduce corrosion. However, the long-term solution to corrosion prevention is simple and brilliant.
The entire space will be maintained at a slight, positive pressure to ensure no radioactive particles migrate up and into the space (conversely, the containment area will maintain a slight negative pressure). And for corrosion protection, the lightly pressurized air will receive desiccant dehumidification to maintain the RH at below 40. As we all know, for corrosion to take place, we need ACME:
The first three (anode, cathode and metallic pathway) simply live within all steel surfaces. The only thing corrosion professionals can modify (other than with CP, metallic coatings, etc.) is removing the electrolyte. That’s all barrier coating systems do. However, with humidity maintained at below 40 RH, there is not sufficient humidity (electrolyte) for corrosion to take place, or, to take place at such a low rate as to be irrelevant.
We’ve consulted on, and lined, many sulfuric acid tanks. And our first question to our clients is if they are able to control the humidity and moisture inside the vessel. 66 Baume sulfuric acid (roughly 93%) is not corrosive at all to carbon steel, if you can keep out moisture. The problems start if water or humidity gets into the mix.
C. THE EXTERIOR SHELL
The exterior shell was made of 105,000 square yards of Type 316L stainless steel (same as my Apple watch!) with 2% molybdenum for enhanced corrosion resistance.
All in all, I thought the corrosion mitigation design was simple, and technically sound. That being said, I am well out of my area of expertise when it comes to the effects of radioactivity on polymers, metallics, and all of the other materials involved in the project.
I’m anticipating some questions pertaining to chlorides. That is, stainless steel can be susceptible to corrosion if exposed to chlorides, and I could not find any documentation relating to the presence of chlorides within the effected, or surrounding, areas.
My concern would be that even if there are very, very small amounts of chlorides, somewhere, there may be a long-term risk if they are able to build up and become concentrated over time.
Of course, the long-term success of this venture remains to be seen. How well with the air pressure systems and desiccant humidification be maintained? Are there any unanticipated consequences (a subject of a future blog) in building something so large and unique for such a unique environment? What will happen when the deteriorating Object Shelter continues to deteriorate and, ultimately collapses?
As in all things, time will tell.