By Linda Thoben Graham, President, Wordsworth Ltd.
Savannah River Nuclear Solutions, LLC (SRNS) in Aiken, S.C., operates with a safety culture that is pervasive and all encompassing– good to know, since the Savannah River Site (SRS) houses one of the world’s most diverse nuclear storage facilities. SRS takes in used, but still radioactive, nuclear fuel from small reactors associated with research, universities, power plants and other sources as part of the nuclear non-proliferation program. When Department of Energy (DOE) Order 420.1B was issued, mandating new single-failure-proof requirements for overhead cranes, SRNS managers faced two challenges. The first challenge was to safely upgrade their 60-year-old Whiting crane in the receiving area to NOG-1 status. And second, get the work done in the shortest possible time frame.
The crane is critical to the operation of the facility.
“Our sole purpose is to operate as an interim storage facility for used nuclear fuel,” said Chuck Kircher, SRNS lead site technical representative for general construction contracts. “That crane is required for us to unload fuel receipts. If the crane isn’t working, we can’t receive fuel from our customers.”
The project scope
Konecranes won the competitive bid to modernize the 85/30 ton crane with a complete replacement of the trolley and all of the hoisting machinery, a project with the potential to earn a one percent contract bonus on the $2.1 million project if the work could be carried out with no safety incidents.
In simple terms, the project involved removing the existing trolley from the crane, taking it out for disposal and putting up a new trolley on the bridge. In practical terms, there was nothing simple about it.
|SRNS operators and RadCon personnel lower a recently received cask filled with used nuclear fuel into large basin filled with water. Once completely emerged, the cask will be opened and the fuel elements removed and stored in the same basin. All photos courtesy of Savannah River Nuclear Solutions, LLC.|
“The designers of this facility never considered that 30 years later, someone might need to come back in and do this work,” said Allan Remund, project manager at Konecranes Nuclear Services, LLC.
Built in the 1950s, the ceilings were too low to bring in a mobile crane, and the access door was only 12 feet wide. In addition, the bay where the crane was located was a contamination area. The trolley that had to be removed weighed 40 tons, was covered in lead paint and was much too large to fit through the door. And, all of the NOG-compliant, modern trolley components had to be engineered to fit in the space of the old machinery.
According to Remund, SRS routinely offers safety incentives for its contractors because safety is their number one priority.
“Given the complexity, duration and difficulty of the project, it was quite an achievement to work six days a week for 11 weeks without any safety issues,” said Remund. “This customer was very focused on safety.”
At every meeting, Remund said, the number one topic was safety and number two was schedule since receiving had to be shut down while the crane was being renovated. Konecranes was required to review its work scope and prepare specific safety plans outlining all of the tasks and procedures for the work. SRNS personnel spent as much time reviewing Konecranes’ safety plan as they did the technical plan for the modernization.
Because safety was such a major component of the project, Konecranes contracted with ATC Associates of Augusta, Ga., (ATC) to ensure that all of the SRS safety documentation and procedural requirements would be met. ATC also provided a safety professional who was required to be onsite at all times monitoring safety and industrial hygiene issues.
|A newly-installed Konecranes crane supports a cask used to transport used fuel from U.S. universities and countries participating in the Atoms for Peace Program.|
The team’s first challenge was to design a protocol to take the old trolley machinery down, in what was still a contamination area. Wearing protective clothing to shield them from residual contamination in the bay and on the crane, Konecranes brought in a mobile trilifter, their best option to lift the 40-ton trolley off the girders from below and rotate it to bring it down in the constrained space. The trolley was lowered in one piece onto a stand inside the building. Then the trolley was cut in half so that it would fit through the door. Once the trolley was outside of the building, Konecranes used a small mobile crane to load the pieces onto a truck for disposal.
According to Cassie Bayer, a former project manager for SRNS, the initial demolition phase was the most challenging in terms of radiation.
“Radiological safety procedures include protective clothing and respirators for certain types of work, including the demolition and removal phase. A crane in a contamination area is subject to lingering radiation on the equipment that is either fixed or transferrable. Wire ropes and old hooks are an issue because of previous contact with radioactive loads and microscopic wear in places where contamination can linger. We conducted radiation checks on everyone and everything coming in and out of the door during this work.”
The trilifter that was brought in to take down the old trolley was also a concern.
“That’s an expensive piece of equipment belonging to someone else, and we had to protect it from transferrable contamination,” said Bayer. “Konecranes and SRS employees covered the floor with plastic ahead of time to protect the wheels from contamination. We also had to protect against dust and flakes of old paint that were potentially contaminated when the trolley was being disassembled. Depending on the particular contaminant, you could have a problem for a couple of hours, or for hundreds of years.”
Bayer, who has since become a project manager for Konecranes, said there are limits and a range that are considered safe and dictate whether workers have to wear only protective clothing or whether a respirator is required.
Beyond the limited space and the potential for radiation contamination, a major industrial hygiene concern was the presence of lead paint on the original trolley. There was a potential for breathing lead fumes as the trolley was cut in half for disposal. ATC’s Matthew Parker, once an SRS employee himself, helped Konecranes evaluate the options to arrive at the best solution.
“There are many different ways to avoid lead fumes– either avoid producing them in the first place or remove the lead paint before cutting–which was not possible since Konecranes had to cut through the trolley to get it out,” said Parker. “Usually you remove the lead, but that’s a very time-consuming process. Because of the expediency of the project and regulatory compliance hurdles, we determined that the best solution in this case was to ventilate during cutting. However, this option required extensive equipment–ventilation controls and spot systems, as well as very sophisticated and expensive respirators.”
Because the old trolley had an 85-ton main hoist with a 30-ton auxiliary, getting it off the crane in one piece was a tricky operation because the load was unbalanced.
“We brought in special rigging experts from Fluor, one of the parent companies of SRNS, to work with rigging experts from Konecranes,” said Kircher. “Because weight on the original trolley wasn’t evenly distributed, it was difficult to calculate where the center of gravity was, so there was a lot of effort that went into making sure the 40-ton load would be brought down safely.”
Konecranes also had to be concerned with fall protection for workers on the girders, planning a pathway where bulky trolley components were taken out of the bay and avoiding slips, trips or falls. Each day, there were literally hundreds of opportunities for a safety incident that had to be anticipated and avoided by Konecranes.
After the old trolley was removed, the entire area was surveyed for radiation and decontaminated, rolling back all transferrable radiation so that the remainder of the trolley modernization could be done in regular work clothing. Since the work was taking place in April and May in the South, eliminating the need for hot and restrictive protective clothing was important for the well-being of the work force.
|– SRNS employees remove a cask from a specially designed truck trailer containing foreign used reactor fuel.|
Working safely was not only the theme of this SRS operation, it was also the reason behind it, as evolving DOE safety regulations were the driver behind the project. New single-failure proof requirements for cranes that handle hazardous loads mandate that if any element of the machinery fails, there is a complete set of redundant machinery that will prevent the load from being lost. In a 100+ page document, NOG-1 specifications define each element that is needed, from the rigging, drives and control systems to the origin, properties and hardness of the steel used in construction. Wire ropes must be organized in a manner to ensure that if one rope breaks, the load remains safely suspended.
The new trolley provided by Konecranes was a full custom design, built and engineered to fit in the space of the old one. Its two space-saving 42.5-ton hoists were designed to provide balanced tandem lifts. The hoists can be operated independently or simultaneously. The crane is radio-controlled, with a pushbutton pendant for backup.
Based on the space available, the dimensional restrictions were in some ways contradictory and very challenging. The trolley had to be compact, but ‘stretched’ at the same time. The hoist hooks needed to be 18 feet apart horizontally, making the hoist units more widely spaced than normal. The hoists themselves had to be very compact to keep the overall length of the trolley as short as possible.
The hoist bottom blocks had to be unusually narrow to fit into an existing structure in the fuel pool, but they also needed to be rotated 90 degrees from what would be considered a normal bottom block orientation. The narrowness requirement mandated a tall bottom block to ensure structural strength, but at the same time the hooks needed to rise extremely high and operate close to the underside of the trolley to accommodate existing building structures. As a result, the hoist machinery had to be elevated to meet the “high hook” dimension, but the overall height of the trolley had to be less than six feet due to the low ceiling in the building.
In addition to the dimensional challenges of the trolley and lifting machinery, the bottom block was designed to include an unusual hook assembly that operates like two fingers that pinch together, allowing the crane to pick up specialized containers with trunnion handles resembling mushroom heads. The bottom block also has a removable custom clevis hook that enables the crane to lift containerized loads in a variety of different sizes and shapes, important for a facility dealing with hazardous loads from many different sources.
As part of the overall design, SRNS asked that Konecranes add platforms, allowing maintenance personnel to walk all the way around the trolley protected by a railing, conforming to current OSHA requirements.
When asked about the most challenging aspect of the operation, Kircher and SRNS Project Manager Susan Bell were in agreement.
“Our challenge was how to get an ASME NOG-1-compliant trolley into an existing operating facility. The project had to be carefully designed and engineered, and Konecranes is the expert in the crane field. They pulled off a tremendous effort here to get something into our facility that would be NOG-compliant,” said Bell.
The Savannah River Site is a DOE Voluntary Protection Program site, and recently DOE conferred its 10th Star Status safety award on SRNS. Kircher explained how an outside contractor like Konecranes successfully interfaced with the safety culture.
“It’s not just a matter of what they are hired to do. It’s a matter of whether they are willing to accept our way of doing business safely,” said Kircher. “We have a mindset of knowing that all accidents are preventable–it’s part of our daily culture. If you are willing to work safely and to the stringent standards that we have, we welcome you here. Nothing else is acceptable.”