By Frank Russo, Project Director for the Hanford Waste Treatment and Immobilization Plant Project
Bechtel National, Inc. is designing, constructing and commissioning the world’s largest radioactive waste treatment plant for the U.S. Department of Energy (DOE). When complete, the Hanford Waste Treatment Plant, also known as the “Vit Plant,” will treat 56 million gallons of highly radioactive waste now stored in aging underground tanks in southeastern Washington state.
The waste is a legacy of national defense efforts that started in early 1943, when residents of Hanford, Wash., were suddenly evacuated, and the top-secret Manhattan Project moved into town. The area was soon transformed into a nuclear weapons production site and became home to the world’s first plutonium reactor. In July 1945, plutonium enriched at the Hanford Site was used in the world’s first atomic blast, the Trinity Test. Weeks later, Hanford’s secret became known following the detonation of the “Fat Man” bomb over Nagasaki, Japan, one of two nuclear weapons credited with ending World War II.
|Four 375,000-gallon waste feed vessels will hold materials in the Pretreatment facility as they await transport. All photos courtesy of Bechtel.|
The Hanford Site also supported Cold War efforts. At its peak, it had nine operating nuclear production reactors and a massive network of chemical processing facilities. The site closed at the end of the Cold War, but tens of millions of gallons of radioactive and chemical waste stored in 177 underground tanks were left behind.
Now, the tanks are well past their intended life spans, and one-third of them are believed to have leaked an estimated one million gallons of radioactive waste. Therefore, it is critical that this dangerous liquid waste is removed from the tanks, treated and stabilized. If left untreated, the waste poses a serious threat to the nearby Columbia River, surrounding communities and millions of residents downstream.
Finishing the Job
The $12.2 billion Vit Plant will stabilize the waste through vitrification, which involves blending the waste with glass-forming materials and heating it to 2,100 F. Once it cools into solid glass, the waste is stable and impervious to the environment. Stable, impervious waste is very important because its radioactivity will dissipate over hundreds to thousands of years. While the vitrification process has been successfully employed at other radioactive waste clean-up sites, it has never been attempted on waste as complex or on quantities as large as those at the Hanford Site.
The Vit Plant covers 65 acres with four major nuclear facilities — the Pretreatment Facility, High-Level Waste Vitrification Facility, Low-Activity Waste Vitrification Facility and the Analytical Laboratory — as well as more than 20 support buildings and underground utilities. It is scheduled to complete construction in 2016, reach commissioning in 2019 and be fully operational in 2022.
The Vit Plant is an unprecedented engineering and construction challenge and the largest clean-up project in DOE’s history. Our scientists and engineers have continually faced new and unique challenges that they have met with rigor and innovation. They have developed extraordinary new technologies and identified new applications for existing technologies — something strongly embedded in Hanford’s history — to address the challenges this project poses.
Advanced 3D Modeling System Provides Clarity and Efficiency
The Pretreatment Facility is the largest and most technically complex of the Vit Plant nuclear facilities. It is 540 feet long and 215 feet wide, the size of nearly four football fields, and it stands 120 feet, or 12 stories, tall. When complete, its total area will be more than 490,000 square feet.
In addition, this one facility contains more than 540,000 linear feet of piping — equal to more than 100 miles. The sheer volume of piping, which will be installed in confined spaces, requires a nest-like design with multiple layers of piping interwoven at every turn.
|Computerized orbital welders produce consistent high-quality welds in hard to reach areas. To test the welds, an Automatic Ultrasonic Testing system was designed for the 30,000 welds that abandoned the old x-ray method of testing welds, eliminating the need to clear worker’s out of the area for testing.|
Team engineers have worked tirelessly to create the safest and most efficient piping design and to identify an installation plan that adheres to strict regulations and nuclear requirements. To overcome this daunting challenge, the team developed a new application for the Bentley Plant Design 3D software that allows our engineers to color code and track thousands of pipe spools, hangers and supports. The software is used to integrate design and procurement data into layers and levels, providing construction crews with up-to-the-minute information on the installation sequence, which spools have been installed and which are ready to install.
Making this information readily available prevents the need to stop construction to go back and fix errors, saving time and money. What previously took several days, now takes only 15 minutes.
The new Bentley application is automatically updated as construction progresses and helps our site supervision, engineers and skilled craft coordinate their work and focus efforts where work is available to ensure the project stays on schedule.
Cutting Edge Automatic Testing Delivers on Safety
In total, 920,000 feet of piping is being installed at the Vit Plant, which requires tens of thousands of welds that must meet exacting nuclear-quality standards. In fact, ensuring the quality of our welds is even more crucial than at commercial nuclear power plants because high radiation levels, once the plant is operational, eliminates our ability to re-examine many of those welds.
Even without radiation issues, inspection of the welds is difficult and was virtually impossible at the onset of the project. The intricate nest-style piping leaves only 3 ½ inches of space between individual pipes, making human inspection impossible in many areas. When the Vit Plant project began, no inspection product or technology existed to address the issue.
In response to the need, engineers developed a unique Automatic Ultrasonic Testing System tailored to the Vit Plant’s needs. This system not only enables us to examine each and every weld, but provides a permanent and auditable record of the examination.
The Automatic Ultrasonic Testing System is a one-of-a-kind system that uses ultrasonic waves, replacing standard radiography testing that requires us to stop work during testing. The system also dramatically speeds up the testing process without sacrificing safety or quality. What previously took three tests, now only takes one—saving more than 60 percent of the time per weld. When applied to the more than 30,000 welds in place, the time and cost savings are incredibly significant.
|The Bentley Navigator Pipe Status Modeling System tracks installation progress to give workers the information they need to determine which modules have been installed, and the order of new installations.|
The Automatic Ultrasonic Testing System also delivers reports with examination results quickly, allowing us to address any issues that may have been identified and ensure strict safety and quality standards are met. Examination results are normally provided on the same day of the inspection, and final reports are delivered within 24 hours. The timeliness of the reports ensures that work can steadily progress and essentially eliminates the need to stop and fix substandard welds in previously completed areas.
The system was developed exclusively for Bechtel and the Vit Plant. It is currently the only successfully implemented automated testing system designed for tight clearances and to meet all regulatory requirements.
Innovative Waste Testing System Maintains Strict Safety Requirements
It is essential that we ensure that the glass produced by the Vit Plant meets all federal and regulatory quality requirements. Therefore, when the Vit Plant is operational, 10,000 waste samples will be taken and analyzed annually using an autosampling system. Developed by our engineers, the system will take samples from all stages of the vitrification process and quickly deliver them, using existing pneumatic transfer technology, to the Analytical Laboratory.
Using remotely operated robotic arms inside shielded boxes, waste samples will be collected in 15-milliliter bottles and encased in tightly sealed carriers. These specially designed carriers will be transported at 25 feet per second to the Analytical Laboratory via a pneumatic transfer system, similar to those used at a bank drive-through. Each sample will be delivered in less than one minute.
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