By Chris GardnerJune 28, 2017
After years of planning and overcoming significant implementation challenges, the STURGIS project team has successfully removed the Reactor Pressure Vessel -- a major component of the U.S. Army's MH-1A reactor aboard the Nuclear Barge STURGIS.
The Reactor Pressure Vessel, which previously held the nuclear fuel during operations, was secured in a shielded shipping container within the containment area of the STURGIS. Once the Reactor Pressure Vessel was secure in the shielded shipping container, it was lifted from the STURGIS onto a transport vehicle. The transporter successfully delivered the Reactor Pressure Vessel to the Waste Control Specialists disposal facility, in Andrews County, Texas for disposal.
"The Reactor Pressure Vessel was the primary source of the radioactivity remaining on the STURGIS," said Baltimore District Project Manager Brenda Barber. "The safe removal of the Reactor Pressure Vessel and its safe transport to the disposal facility is a huge milestone for our team. It means we have now removed approximately 98 percent of the radioactivity from the STURGIS and a total of 850,000 pounds of radioactive waste."
A unique history and a lot of dedication and hard work have lead up to this significant milestone.
The STURGIS started out as a World War II Liberty Ship, but in the 1960's it was converted into a floating nuclear power plant, home to the MH-1A reactor. It was used to provide power generation in remote locations for the U.S. Army, spending most of its time in service in Gatun Lake providing power to the Panama Canal Zone from 1968 to 1976.
Deactivated in 1977, the STURGIS was defueled, decontaminated for long-term storage, sealed and except for periodic maintenance was stored until recent years. In 2012, its formal decommissioning effort began as part of a broader effort to decommission the Army's retired nuclear reactors through the Army Deactivated Nuclear Power Plant Program.
After years of planning 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 where she had been stored in the James River Reserve Fleet in Virginia to Galveston, Texas in April 2015 for her final decommissioning.
Baltimore District, home to the Corps of Engineers' Environmental and Munitions Design Center (EMDC) and North Atlantic Division Radiological Health Physics Regional Center of Expertise (RCX), manages the project overall, but the execution is carried out in close coordination and partnership with the Corps' local Galveston District.
"This decommissioning effort for the STURGIS is a complex project and we could not have done it without our partners in the Galveston District," said Baltimore District Commander Col. Ed Chamberlayne. "It's also been done in close partnership with the U.S. Army Corps of Engineers Headquarters and the Army Reactor Office."
Since her arrival in Galveston, crews have been carrying out the complex work of dismantling portions of the vessel to gain access to the reactor components to allow for their safe removal.
"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. These well engineered elements have been taken apart by our team section by section over the past two years in Galveston."
After setting up the project site upon her arrival in April 2015, crews began the painstaking work of systematically taking the vessel apart. 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 floor by floor. The first low-level radiological waste shipment occurred in October 2015 and has been ongoing since that time.
While the work took longer than anticipated due to the unique complexities of the project, crews continued working to remove each of the elements of the reactor. All items are properly packaged and shipped to the disposal facility. By June 2016, the team was able to remove another major component -- the 35-ton former spent fuel storage tank.
"The work on the STURGIS has been difficult, but the crews working down here in Galveston have done a tremendous job communicating the risks associated with each task and worked together as a team to mitigate each of these risks," said RCX Program Manager Hans Honerlah of Baltimore District, who has provided on-site radiological oversight for most of the effort.
The next big challenge was how to gain access to the Reactor Containment Vessel.
"The Reactor Containment Vessel is what we often refer to as 'the egg,'" Barber said. "It's a thick, 350-ton steel spheroid that contains all the main reactor components, including the Reactor Pressure Vessel. The major reactor components were the items where the team had to be prepared to handle a majority of the radioactivity remaining on the STURGIS."
In August 2016, crews were able to remove the first of several sections of the canopy on top of the Reactor Containment Vessel. By January 2017, the crews had removed the canopy and began to cut the Reactor Containment Vessel to gain access to the reactor components. During the process of dismantling portions of the STURGIS to gain access to and remove radioactive components, the team has been able to safely recycle approximately 600,000 pounds of lead.
By March 2017, the team had begun the process of removing the large components from the Reactor Containment Vessel, including the Steam Generator, Pressurizer, Coolant Pumps, Refueling Shield Tank, Ductwork, and Reactor Head Dolly. The removal of these large components from the Reactor Containment Vessel provided access for the team to remove the Reactor Pressure Vessel, the reactor component that historically had the highest amount of residual radioactivity remaining on board the vessel.
Reactor Pressure Vessels are thick steel containers that hold nuclear fuel when the reactors operate. The vessels provide one of several barriers that keep radioactive fuel contained and out of the environment. During the reactor operation, it generates subatomic particles called neutrons. Some of these neutrons hit atoms in the steel as they leave the core and when these are captured by the steel they can make the steel radioactive. All nuclear fuel was removed from the vessel when it was shut down in the late 1970's and the residual radioactivity remaining was within the stainless steel of the Reactor Pressure Vessel.
While the bulk of the radioactivity has been safely removed from the STURGIS, there is still a great deal of work required to complete the decommissioning portion of the project. Over the next several months, the team will remove the remaining contaminated items, package and transport them to the disposal facility. After all of the radioactive materials have been removed, the team will access the very small spaces within the hull bottom tanks to complete the required surveys to allow the vessel to be released for shipbreaking. The team anticipates some challenges with the hull bottom tanks to include very unique confined space entries, heat stress, lead-based paint issues, and the approach to cleaning the metal surfaces. These are risks the team is actively managing for this upcoming work.