Technology helps develop first-of-its-kind equipment for clean-up work on the famed Hanford Site.
When thousands of workers from across the country descend upon the Hanford and White Plains area of Washington State in 1943 responding to a work request from the government, few, if any, were certain what type of work they were signing up to do. Just like the residents of these two farming and agricultural towns who were told to evacuate their homes and abandon their farms, the workers were told simply the land was to become an area for “important war work.”
At the time, the country was more than a year into its involvement in World War II and this 586-square-mile patch of land was earmarked by the government to become the site on which nine plutonium nuclear reactors would eventually reside. With the threat of nuclear war very much a reality, the United States was preparing for full-scale production of weaponry that would change the course of modern warfare.
Up until that time a full-scale, production-size nuclear reactor had never been built. But in just 13 months the 51,000-person construction crews constructed, among other facilities, the world’s first facility to extract plutonium from irradiated fuel rods, named the B Reactor as well as T Plant. These two facilities would eventually be used to develop the Fat Man Bomb, famously known for being detonated over Nagasaki, Japan in 1945.
Throughout the next 40 years, the area that became known as the Hanford Site would play a role in producing plutonium for America’s defense program through the Cold War, and up until the final reactor was shut down in 1988. From that time, all that remained were memories of a time gone by. That, and the millions of tons of solid waste and the hundreds of billions of gallons of liquid waste that is the result of producing plutonium for years.
But in 2001, perhaps the most important mission commissioned at the Hanford Site commenced when Bechtel National Inc., www.bechtel.com, Frederick, Md., working for the U.S. Dept. of Energy, www.energy.gov, Washington, D.C., began constructing the world’s largest radioactive waste treatment plant. Known as the Hanford Tank Waste Treatment and Immobilization Plant (WTP), this project, expected to complete construction in 2016 and to achieve full operations by 2022, will process and stabilize 56 million gallons of radioactive and chemical waste that currently resides in 177 aging underground tanks—tanks that some fear are in danger of spilling out into the nearby Columbia River.
Such a large amount of waste is not uncommon with petroleum production. The process is notoriously inefficient—yielding just a small amount of product while leaving behind mass amounts of liquid and solid waste. To handle such a waste-treatment process, the WTP plant will use a method called vitrification technology that involves blending the waste with glass-forming materials and heating it to 2,100 degrees Fahrenheit, a mixture that is then poured into stainless-steel canisters to cool and solidify. This allows the waste, which at that point would be impervious to the environment, to stabilize and its radioactivity will dissolve throughout the course of hundreds to thousands of years.
This has earned WTP the nickname the “Vit Plant,” where some 920,000 feet of piping is to be constructed to carry out such a process. It’s within that piping construction where the real innovation begins to take shape for Bechtel.
Automate the Inspection
When Richard Campbell, corporate fellow, Bechtel, says the specs of WTP had the tightest requirements of nearly any project, he means it literally. Looking at the big picture, WTP, which is designed to operate for more than 40 years, constructs to ASME (American Society of Mechanical Engineers), www.asme.org, New York, N.Y., B31.3 Normal Fluid Service plus imposes additional requirements of no incomplete penetration or incomplete fusion. In other words, the myriad of intricate piping being installed at WTP is held up to some pretty stiff inspection requirements. Because of the fact this piping will be transporting radioactive tank waste, it is of utmost importance that every weld—30,000 to be exact—joining two sections of pipe be precise and without defect.
“Many of the welds are in black cells, which are rooms that will be sealed and will never have human access once they are completed,” he says. “So the welds we are looking at require 100% visual inspection and 100% volumetric examination by the codes in our tight requirements.”
Volumetric inspection is typically done using one of two methods: radiographic testing or ultrasonic testing. Radiographic testing presents a problem right from the onset. Like your typical x-ray, radiographic testing requires radiation in order to expose the film. This means that for every weld created, the crew would then be required to create exclusion zones of at least 100 feet in a three-dimensional radius where work would be halted so the workforce would not be exposed to radiation. That means not only right at the spot of the weld, but also one floor above or below. While that might not seem like a big deal, multiplied out for more than 30,000 welds, halting construction for that long would most certainly be detrimental to maintaining the tight project schedule.
As for ultrasonic testing, this requires a person manually scanning the pipe with a transducer, moving the tool around the diameter of the pipe. This form of testing is typical in other industries, but would not adhere to the tight requirements for WTP. Another factor playing against this form of testing is the intricate nest-style in which these pipes are being arranged. Left with only 3.5 inches of space between individual pipes, it was physically impossible to manually scan the welds.
The team at Bechtel was left with one more viable option: AUT (automated ultrasonic testing). The technology has become a preferred method of testing in such industries as aerospace and oil or power pipeline inspections, which in essence automates the ultrasonic testing process. But AUT had never been done on small bore, thin wall piping, which was being installed at WTP.
“When we went out to get a contractor to do this, none had experience using it on pipe smaller than about 6 inches in diameter,” says Campbell. “The majority of our work (with pipe) is about 2 inches schedule 40. The technology was available, but no one was developing the equipment and the techniques for such a thin wall.”
However, one great thing about being the largest engineering, construction, and project-management company in the world, as Bechtel is, is the phrase “it’s never been done before” doesn’t stand in the way of progress. This mentality has made projects like the Hoover Dam and the Channel Tunnel, among Bechtel’s signature projects, possible, when others deemed them to be too complex.
It also helps to have access to partners that are willing to innovate. Such was the case with AIT (Advanced Inspection Technologies), www.aitechnologies.biz, Melbourne, Fla. The remote visual-inspection technology company developed a computerized system that would not only examine the welds, but also provide a permanent and auditable record of the examination. The company took some of Bechtel’s existing orbital welding heads and modified them to do this work.
“They actually clamp these heads onto the piping system and when they start the machine it begins to scan around the pipe without the need for a person to hold the transducer and move it around the pipe,” says Campbell.
Simply applying field-automation technology to the process isn’t the answer. Performing AUT on piping so small presents challenges in both technique and procedural development, meaning the new automated orbital scanners needed to uphold to such standards. If such technology were to be used, the team needed to establish the process for which all examinations will be performed.
Some considerations in creating an examination procedure include the principles in ultrasonic and its limitations for each pipe weld configuration. The mechanical equipment needs to be portable and mobile so it can be easily transported to the area where the examinations are performed. The equipment must be efficient enough to maintain proper positioning as it is maneuvered around the pipe and still maintain its proper acoustic coupling.
In addition, WTP specs required the weld inspection process be both repeatable and accurate. Yet, as Campbell states, how do you know you have covered the full range of the weld and that it is repeatable, with consistent data when done by hand? This is where automation takes over.
Given the technique developed, this process now becomes automated without the need for human intervention. The procedure used for collecting and interpreting the data now ensures repeatable results that allow AIT and Bechtel to view the data and ensure that 360 degrees of the circumference and the full width of the weld in all directions have been covered each time.
“Manual (ultrasonic testing) used to require an eye to examine the welds and interpret the results at that point with no recorded data,” says Nick Labella, senior field engineer, welding, Bechtel National Inc. “With AUT and the electronic systems it is a mechanized system that carries the probe around the pipe, keeping the X and Y coordinates as it goes and (then) digitizes the data so that it can be retrieved later and reviewed on the computer for analysis. So it is always a permanent record of that weld.”
Labella’s latter point regarding the data is an important one. WTP engineering specs require ultrasonic testing to be done with an automated system that outputs the data into a computer system, which is then used for building a series of 2D images of the weld profile circumferentially around the pipe, along with any defects. The mechanical X and Y position scanners are controlled from a motor controller that allows the recorded data to have axial and circumferential positioning of the data points. The scanner is the transport system for the transducer, the transducer is what acquires the data and through the transducer cable the data is sent to the software on the PC, and the data is digitized for interpretation. From there, the data is transferred back to the Bechtel IT systems via the company Intranet or portable media. Once received, the data is stored within Bechtel’s internal system for archiving.
“Similar to a radiograph when you get an x-ray where you can go out and review it and see the contents of the film,” adds Labella, “(it’s) the same thing with the (AUT) digitized data; you can go back and review it, and then perform analysis on it.”
Of course, such a process was not inexpensive. But the long-term savings, in both time and cost, were too great to allow for sticker shock. Using this method, the number of ultrasonic examinations needed to ensure quality and safety are reduced by a measure of three to one, which represents a savings in time of more than 60% per weld.
Now add in the time-savings aspect. Adds Campbell, “We are now able to get (the welds) inspected literally within one or two days of when the weld was made. Whereas with radiography, it would often take five-to-seven days before they could get inspected, due to the exclusion zones. So this means that we get feedback sooner and it allows them to repair the welds before we have welded too much and they are no longer accessible.”
The reporting and analysis data helps speed the overall inspection and approval process. To help ensure all welds meet safety and quality requirements, reports can be generated when necessary, helping to provide data that supports the fact standards have been properly met. This means pipe weld examinations are conducted, evaluated, and reported all within the same day, with final examination reports delivered within 24 hours of inspection. This is critical as workers no longer need to worry about going back to fix a pipe weld once a particular section has been completed. Overall, confirming weld integrity in black cell piping is critical because there will be no ability to monitor piping during operations as the radiation levels will be so high.
“The biggest thing is that we have been able to use this in lieu of using radiographic testing, an age-old method used for testing,” he adds. “By using AUT we are reducing radiation exposure with no need for exclusion zones, while dramatically improving efficiency and productivity.”
Setting the Standard
As of December 2011, the WTP project was well on its way to meeting the 20-year deadline established by its owners: Standing at 88% complete in design, 74% complete in procurement, and 39% complete in construction. There is little doubt as to the role AUT and the accompanying technology played in the process.
The fact of the matter is AUT is performed around the world, but the methods, equipment, and associated technology used on the WTP project is unique and, according to Bechtel, had never before been successfully executed. But now the method is finding its way onto other Bechtel projects.
Back at WTP, perhaps the biggest test still lies ahead. Moving forward, pipe welds scheduled to be made will be in areas of great congestion where access becomes more limited. Each weld needs to last the lifetime of the facility, but just as important to the process is the documentation that will become the reference point should a failure occur.
As we prepare to tell the next chapter in the story of the Hanford Site, you can bet it will involve the role of AUT. Mixing the right blend of innovation with applied technology has created a very effective tool that, unlike the petroleum-producing efforts that made this site famous, produce little, if any, waste.
Color by Pipe
As with any large industrial plant, work on the WTP project involved the process of tracking spools (the preassembled, prefabricated section of a piping system that includes pipe fittings and flanges) to determine which pipe spools would go into which planning areas.
In the beginning, with the limited amounts of piping involved, this was a fairly straightforward process. But as piping for the black cell began to be modeled, as Bill Kieffer, senior integrated project team construction representative, pretreatment, puts it, “We realized we had a different animal on our hands.”
As he explains it, the average length of the spools used is about 10 feet, which means roughly 56,000 spools needed to be tracked into the plant, and each needed to get through engineering and procurement and out to field in a satisfactory order based on the construction sequence. Early troubles with this process were typical of any large-scale project: engineering, procurement, fabrication, and construction all had their own tools for tracking details.
“Every meeting we had, everyone would bring their list of spools from their own software, their own databases, all packaged up in way that made sense to them, to present why they needed these parts and pieces,” says Kieffer. “The whole meeting would end up being a comparison of data sets. We recognized that beyond just talking about data, we needed to do something to communicate up the chain to management on the status of piping: how much has been fully modeled, how much has made it to issued isometric standpoint, how much was in procurement, and how much construction has its hands on.”
Technical issues, like piping either being changed or added, only complicated the process further.” You think you are done with an area, but here comes another 5,000 feet of pipe, (so) to be able to show management and everyone in procurement, engineering, and construction the overall amount of pipe being delivered, what has changed or been put on hold or is being revised, and where it (all) goes (in the plant) is critical,” says Kieffer.
As he describes it, given the nature of a design/build job, the design is coming out a few months before you need the pipe, and as a result you are condensing your procurement timelines and picking and choosing critical components that you need and forcing those through the system. Inevitably this means you are working through things that will be late, meaning you will need to go back into the same areas you were working previously.
“What we have done on this job is to try and speak early to the engineering group about our construction sequence, as well as let management know why it is so important to be working 12 to 18 months ahead on certain systems, and what are those pipes … and why they are important,” he says.
The solution was two-fold. One, a database was created so all the parameters of a given pipe spool are in one spot. This helps with producing reports being generated for all different groups. Next a colorized 3D model that provides a visual representation of pipe sequencing was developed.
With the colors, green is good, meaning engineering was done with it and that procurement had bought the pipe, fabricated it, and delivered it, and it was sitting in yard ready to install. If piping was hung up in a procurement process, for example, it appears yellow. Finally, any pipe that had not yet been issued or gone back on hold is red.
The model is based off of 3D plant-design software from Bentley Systems, www.bentley.com, Exton, Pa., with a navigator tool for visualizing the 3D model and querying data.
This model became an important part of the scheduling process on this job, helping the team make decisions in a very graphical environment and allowing them to visualize changes as they came on board.
“If you add some piping in a planning area, it does not have much of an impact if you add it in the right spot,” adds Kieffer. “But if you start lacing it through the rest of the thousands of feet of pipe and wind it through like a snake, it needs to go through in a particular sequence.
“So early on in the game, as we are watching this in our (weekly) meetings, you can see the new pipe, (and) the pipe that is on hold, and you can impress on the procurement and engineering teams that if you really do need to route it at that point, then this is a priority spool and we need it soon because we need it in before the rest of this pipe. Because, let’s say, it is up against a wall, high against the ceiling; it will become an inaccessible area if we continue our work package installation sequence as planned.”