The U.S. Army Corps of Engineers team has recently completed a very complex and unique project phase by finishing the decommissioning of the Army’s first and only floating nuclear reactor prototype – the MH-1A aboard the STURGIS.
Led by the Radiological Center of Expertise in the Corps of Engineers’ Baltimore District, and carried out in close coordination with the local Galveston District personnel, plus contractors on site, crews have worked tirelessly for the last three years to access the radioactive components of the nuclear reactor aboard the STURGIS and safely remove, transport and dispose of them from the vessel.
In all, the project team has safely removed more than 1.5 million pounds of radioactive material and recycled more than 600,000 pounds of lead as part of the decommissioning.
“The U.S. Army Corps of Engineers mission is engineering solutions for the nation’s toughest challenges and this team here really delivered on a solution to this unique challenge,” said Headquarters USACE Chief of the Environmental Division Karen Baker during a ceremony aboard the STURGIS to celebrate the milestone.
The entire project was carried out with safety always in the forefront.
“Safety has always been our number one priority in carrying this project out,” said Baltimore District Project Manager Brenda Barber. “We were committed to ensuring the safety of the public and our crews and I’m proud to say we completed our decommissioning work with no evidence of radioactive material, lead or increased radiation exposure from the STURGIS being documented outside of the reactor containment area at any point during the project.”
The STURGIS’ unique story began as a Liberty Ship in World War II. After the war, the vessel was converted into the world’s first floating nuclear power plant in the 1960’s. The STURGIS’ nuclear reactor, MH-1A, was used to generate electricity for military and civilian use in the Panama Canal for several years before being shut down in 1976. The reactor was then de-fueled, decontaminated for long-term storage, and sealed before being towed to the James River Reserve Fleet at Joint Base Langley Eustis, Virginia for long-term storage and monitoring.
Detailed planning for the decommissioning effort formally began in 2012 and after years of preparation and coordination with partnering agencies, government officials and other stakeholders an Environmental Assessment of multiple potential sites for the decommissioning work was completed in 2014. After award of the decommissioning project contract, the STURGIS was ultimately towed 1,750 nautical miles from the James River Reserve Fleet in Virginia to Galveston, Texas in April 2015 for her final decommissioning.
“At first, there was a bit of anxiety among some members of the Galveston community when they heard that a nuclear reactor on a ship was being towed to their area,” Barber said. “That being said though, once we had the opportunity to provide additional information about the STURGIS and explain our processes and safety protocols we’ve found the members of the Galveston community, local leadership and the workforce to be wonderful partners in this process. I’d say the local support has been a big contributor to the success of this project.”
After setting up the project site upon her arrival in April 2015, crews began the painstaking work of systematically taking apart portions of the vessel around the reactor. First, the team constructed two secure access hatches on the STURGIS top deck to allow all of the waste to be removed safely. Then the team began to remove waste from the reactor containment area deck by deck.
“When the Liberty Ship was converted into a floating nuclear reactor back in the 1960’s, they never intended for it to be taken apart,” Barber said. “It was built to house a nuclear reactor with thick elements of steel, lead and concrete barriers which provided protection for the workers and the public during her operations.“
Despite these challenges, the first low-level radiological waste shipment occurred in October 2015 and shipments continued steadily as the project progressed.
Executing the project on the water provided its own challenges as well. The project team coordinated with the Corps’ Marine Design Center to make sure that their work in creating hatches for lifting reactor components off the vessel via dockside crane didn’t create structural issues for the floating vessel.
The team also had to ensure the pier itself was able to handle critical lifts of packaged reactor components weighing from one ton up to 80 tons.
In early 2017, the team finished the painstaking efforts to section and remove pieces of the top of the Reactor Containment Vessel. This allowed for access to the main reactor components. Crews worked to steadily remove components including the steam generator, pressurizer, coolant pumps, refueling shield tank, ductwork, and the reactor head dolly to provide adequate access for the removal of the vessel’s Reactor Pressure Vessel (RPV) – essentially the reactor core.
This major milestone for the team was completed in May 2017 just prior to the 2017 hurricane season.
“The RPV is where the nuclear fuel was held when the MH-1A was active and was the primary source of remaining radioactivity on the STURGIS,” Barber said. “Its removal was a significant milestone for the decommissioning effort and meant we had successfully and safely removed the vast majority of the radioactivity from the STURGIS.”
The removal of the RPV was a complex operation, which involved securing the RPV into a custom-made shielded shipping container while it was still within the containment area of the STURGIS, then lifting the roughly 80-ton RPV and shielded shipping container onto a transport vehicle. The RPV was then successfully transported to the Waste Control Specialists disposal facility, in Andrews County, Texas for disposal.
With the safe removal and transport of the RPV, the team had successfully removed approximately 98 percent of the STURGIS’ radioactivity.
The removal of the remaining 2 percent of low-level radioactivity was the next challenge for the team. The majority of the remaining radioactivity was in the activated metals of the thick steel components of the large Primary Shield Tank that provided shielding for the RPV when the reactor was operational and a portion of the bottom of the Reactor Containment Vessel. The team finished the removal of these items by March of this year.
One of the more arduous tasks that was part of the efforts was working in the vessel’s hull bottom tanks to conduct radiological surveys, remediate any contamination found and then conduct additional surveys confirming the success of the remediation. To access the hull bottom tanks for surveying, radiological control technicians would have to crawl into small, confined tanks through hatches way down anywhere from two to 30 feet into the vessel’s hull bottom via narrow 16 inch by 24 inch hatches. Once down the hatch, personnel then had to navigate through the 22 hull bottom tanks running along the bottom of the vessel, divided into hundreds of cells that are themselves broken into countless smaller compartments all separated by the same sized hatches used to enter the tanks themselves.
“Once you get down into the tanks, every thirty inches, to get from one compartment to another you have to crawl through another ones of these tight hatches just like the one you had to work through just to get into the hull bottom,” said Radiological Health Physicist Hans Honerlah, the program manager for Baltimore District’s Radiological Center of Expertise. “You’re crawling in them, with your tools, it’s hot, you’re wearing a respirator, and our crews have been living that effort for the past year or two of this project. That’s a hard job, but it speaks to the dedication our crews have when it comes to this project.”
With the decommissioning work complete and all necessary radiological surveys showing no more radioactivity remaining on the vessel, all that remains for the STURGIS is the final traditional shipbreaking after being towed to Brownsville, Texas. The remaining vessel and components will be recycled.
USACE personnel executing the Army’s Deactivated Nuclear Power Plant Program are hoping to build upon the success of the STURGIS project as they work through the decommissioning planning phase for the Army’s two last remaining reactors in the program – the SM-1 at Fort Belvoir in Virginia and the SM-1A at Fort Greely in Alaska.
“We’re proud of what we’ve accomplished with the STURGIS and how we were able to complete a complex and unique job and do it safely,” Barber said. “Successfully completing the decommissioning of the STURGIS is something the entire team is really proud of, but we can’t rest on our laurels and now we’re shifting our focus to the next two reactors.”
Christopher Gardner – U.S. Army Corps of Engineers, Baltimore District