MOVING THE IMPOSSIBLE
Designed in the late 1940s as the third in a line of reactor projects pursued by Argonne National Laboratories in collaboration with the Oak Ridge National Laboratory, and on behalf of the Atomic Energy Commission, the Materials Testing Reactor (MTR) was the first large-scale test reactor in the world. The MTR was located at the Idaho National Engineering Laboratory (INL), formerly known as the National Reactor Testing Station. The 40 Megawatt reactor first went critical in 1952, testing materials for reactors of the future by bombarding them with high levels of neutron radiation.
Construction of building TRA-632 was completed in 1952 as well, its sole purpose to support the efforts of the MTR. The building contained three ‘Hot Cells,’ shielded rooms where: assembly and disassembly of MTR components could be performed; preparation and processing of materials could be executed using the lathes, power saws, grinders and welders contained within them; and materials exposed to neutron bombardment within the reactor could be examined by methods such as gamma scanning, photography and optical mettallography.
Of particular note was Hot Cell #1. Hot Cell #1 was designed for examination and processing of very high dose rate materials, and like the other two cells, was designed with shielding in mind. The walls were made of high density concrete of 4-foot nominal thickness, lined on the interior with ¼-inch carbon steel plate. The floor was constructed of 3-foot-thick normal density concrete and the structure was covered by a 2 ½-foot-thick high density concrete roof. Work was performed by operation of five master-slave manipulators, and viewing and observation was made available through zinc bromide filled or leaded glass windows, with the assistance of two periscopes for magnified viewing when necessary. Hot Cell #1 weighed over 600 tons (1.2M lbs.) after it was prepared for transport to its final resting place.
Due to the high dose rates remaining within Hot Cell #1, the original decommissioning plan called for it to be filled with grout, sliced into cubes of approximately 50 tons each, and then transported to the Idaho CERCLA Disposal Facility (ICDF) after the building formerly housing it and its two sister cells had been demolished around it. Instead, it would be filled with a 4-foot-deep layer of grout and cut from its foundations. The massive 600-ton piece, with an appropriately shielded hotspot of over 72 R/hr on its exterior, was loaded onto one of the largest transporters in the world and moved 2 ½ miles down the road (partially on a semi-improved gravel road built specifically for debris and material disposal purposes), to its final resting place in the ICDF, where the remaining internal void spaces were grouted and left to be buried.
Clauss Construction, of Lakeside, California, U.S., provided management for the operation, with field execution engineering performed by Ruby and Associates of Farmington Hills, Michigan, U.S., and lifting and transport performed by Southwest Industrial Rigging of Phoenix, Arizona, U.S.
The rigging, lifting, final transport and disposal were the last of the building TRA-632 decommissioning project. CH2M-WG Idaho (CWI), which manages the Idaho Cleanup Project for the Department of Energy, had been working on the decommissioning phase since 2009. The building was emptied of material, and all three cells were emptied of contaminated items through a combination of manipulator work and personnel entries. Over time, the building structure, along with Hot Cells 2 and 3, were actually demolished around Hot Cell #1, leaving Hot Cell #1 as the sole fixture on what had previously been the foundation of building TRA-632.
CWI completed the initial engineering design prior to award, which provided Clauss Construction and SWIR initial direction on the project. This allowed the two firms to provide execution direction and final engineering plans to support the massive undertaking. After completion of these calculations, a massive set of lifting fixtures were designed and fabricated by Premier Technology of Blackfoot, Idaho, U.S.
Once delivered, the lifting fixtures were installed by CWI personnel. In order to provide the maximum amount of safety during the lift, the rig was drilled and epoxy bolted to the cell by 128 Hilti bolts, each driven 2 feet into opposing walls of the cell at the top and bottom, linked by steel connecting rods from top to bottom. This was done to spread the massive load across the sides and floor of the Hot Cell, and to ensure that a pre-existing cold joint remained intact where one concrete pour stopped and another began during original construction. The fixtures and hardware alone weighed approximately 40,000 pounds.
Due to the highly contaminated nature of the surfaces inside the hot cell and the requirements of the final disposal cell, an appropriate fixative for contamination control had to be identified. Warren Environmental, of Carver, Massachusetts, U.S. was contacted and asked if they could demonstrate the effectiveness of their product, Warren Environmental ThermaFlex 301-20, a 100 percent solids solvent-free epoxy. Over the course of four days, Warren Environmental staff constructed a rough plywood model of Hot Cell #1, designed and fabricated a bespoke application device, and demonstrated the effectiveness of both the product and the applicator to experienced CWI management in their Carver facility.
In order to apply the fixative, an applicator was designed to fit through a 4-foot-long, 4-inch diameter hole core-drilled through the roof of the Hot Cell; it was able to coat all surfaces inside the cell, including any remaining greasy or oily equipment that had been left in the cell. Warren Environmental proved the capabilities of their method and were contracted to provide the fixative. Once the fixative was applied and the Hot Cell was filled with grout to a depth of 4 feet, preparation of the hot cell interior was complete.
After the grout and fixative were set, CWI took on the task of separating the Hot Cell from its foundations by scoring the wall and floor slab interface with a 40-inch circular concrete saw. They completed the effort with no spread of contamination outside of the cell.
To mitigate an exterior dose rate of 72R/hr, CWI also designed, fabricated and installed a steel frame to support the 100 lead bricks required to bring down the dose rates to manageable levels.
Several innovative techniques were employed in all aspects of the execution of this project, including the training, the management and the implementation. As early as two months prior to the initiation of the project, Clauss Construction began holding weekly pre-planning meetings with CWI and Stoller, which manages the disposal facility. This ensured that all interested parties were constantly and consistently up-to-date with the latest progress reports and project developments, and were able to identify issues well in advance of any problems arising.
Southwest Industrial Rigging was able to realize a significant cost savings by taking a non-standard approach to training their crew. Based over 900 miles from the site in Phoenix, Arizona, SWIR gained approval from CWI to send personnel to a local Phoenix-based OSHA 40 Hour HAZWOPER training center. This reduced onsite training requirements for the temporary personnel, overall training time from 2 ½ weeks to one week, and significantly reduced costs associated with training by removing the need for personnel to travel and stay in accommodations near the site during the training period.
CWI also allowed SWIR to realize additional cost savings by granting them the flexibility to source materials that had not been foreseen during planning as the needs arose, rather than requiring the company to schedule and use CWI contracted vendors. Since SWIR had mobilized some of its own flatbed trucks for delivery of equipment to the site using their own CDL drivers, the additional materials were able to be sourced from vendors in Salt Lake City, Utah, U.S. and then picked up and delivered in a very short period of time by the SWIR drivers. This saved the additional costs of overnight shipping of the materials
Perhaps the most important decision made by Clauss Construction and SWIR was their choice to use SWIR’s portable 850-ton capacity, four-legged gantry crane system to pick up, load and unload the Hot Cell, rather than using a conventional crane. There were several reasons that the gantry system was chosen, including stability during the lift and the relatively short time required to assemble, pick up, disassemble, move and reassemble the system at the receiving end. A conventional crane with a capability of lifting the 600-ton Hot Cell would have taken at least 15 days to assemble and would have been more unstable under load, increasing the risk of error and reducing the likelihood of precisely placing the Hot Cell onto its target. A conventional crane would have also been affected by the high winds, commonly experienced onsite, therefore impacting the schedule in a negative manner. The four-legged gantry has a much shorter profile, smaller surface area, and can be operated in winds that would normally curtail conventional crane operations. Since the gantry system was able to be erected and dismantled in less than two days, the schedule to complete the project was much shorter. By using the four-legged gantry crane system at both ends of the transport a significant cost was saved.
Verification of Contamination Levels
Due to concern that the grouted drain lines would hold significant levels of contamination high dose rates, once Hot Cell #1 was lifted to a height of approximately 36 inches, under-slab drain lines were checked with long-handled radiological measurement devices, as well as visually checked to verify they had separated from the cell. This verification provided a hold point to ensure that dose levels were controlled and contamination would not be spread when the cell travelled to the contamination control pan, and subsequently onto the Goldhofer transport. After confirming dose rates and contamination levels were well below the hold point requirements for stop work, the 600-ton cell travelled approximately 30 feet on its track set to the absorbent sand-filled contamination control pan.
Capturing Debris with Absorbent Sand
The contamination control pan was designed by CWI and fabricated onsite at the INTEC facility. It was constructed to capture any debris that might fall from the bottom of the Hot Cell, as original area radiological surveys showed some hot spots of soil adjacent to the cell were in the 30 R/hr range. The absorbent sand would also provide shielding if high dose rates were encountered. The sand’s even distribution across the uneven direct-pour surface of the hot cell floor allowed for the weight to be distributed across the entire contamination reduction pan.
Transferring the Hot Cell
Once the Hot Cell was placed into the pan, heavy 3/4-inch, grade-100 securement chains were attached, allowing the Hot Cell and pan/sand assembly (with a combined weight of over 600 tons), to be rigged, lifted and placed onto the specialized Goldhofer transport trailer provided by SWIR.
The Goldhofer transport trailer consists of two sections approximately 10 feet wide and 70 feet long, each weighing 110,000 pounds. When in use, the two sections are bolted together with spacers to work as a 22-foot-wide single trailer assembly. The modular trailer was designed so that once the trailer sections are mated together, all hydraulic systems and air braking systems work in unison. The trailer consists of 14 lines of axles, with a total of 224 tires; each set of dual tires is on a turntable allowing the trailer to crab-walk or circle-steer around objects or through turns during its route to the ICDF. The trailer has twin diesel power packs allowing the operator to control hydraulics independent from the Prime Mover (Tow Vehicle), and make leveling adjustments, as well as steering adjustments and inputs. This mode was used several times while negotiating tight turns and on uneven surfaces. The Prime Mover for the trailer is a 12-foot-wide, planetary drive Kenworth tractor equipped with full locking rear axles and 75,000 pounds of counterweights for traction.
After the height of the Goldhofer trailer was properly adjusted, the trailer was backed into position under the previously lifted Hot Cell and pan assembly. The load was placed on the trailer in a pre-calculated location to ensure that trailer loading and weight distribution met all manufacturers’ requirements and engineering calculations. Once placed onto the Goldhofer transport, the operator verified (via four hydraulic pressure gauges) that the load was at its true center on the transport (the gauges show hydraulic fluid pressure levels for the front, right and left sides of the transport). Under the power of the Prime Mover, the loaded trailer was slowly moved from beneath the gantry system and staged on the haul road constructed by CWI inside the ATR complex. The gantry was then disassembled and moved in pieces to Hot Cell #1’s predetermined final location within the ICDF, where it was reassembled in preparation to remove the cell from the transport.
At 2½ miles overall, Hot Cell #1’s journey was a challenging one. The 22-foot-wide transporter traveled down a undulating one-mile stretch of 28-foot-wide gravel road, (commonly used by articulating dump trucks and other heavy equipment hauling debris), to a two lane paved highway, and finally to the entrance of the ICDF at a maximum transport speed of five miles per hour.
After a Caterpillar D9T bulldozer was used to ensure adequate traction on the gravel ICDF entry ramp, and all personnel involved in the project were briefed, the transporter began its ascent. It climbed a short 5-percent grade into the disposal area, over the cell’s anchor trench berm, and down into the ICDF cell where the gantry system had been reassembled to unload the transporter.
Once Hot Cell #1 was lifted off the transport trailer and the trailer left the scene, the hot cell was lowered the last 30 inches to its final resting place within the ICDF. Crews disassembled and removed the gantry crane over the following few days, and the Hot Cell was completely filled with grout in place.
This project was successful on many fronts and for many reasons. CWI provided enough guidance at the onset that allowed industry experts to provide approaches that saved the client time and money. An innovative approach was used for the lift, required training was obtained in a manner that alleviated excessive travel, and those involved came equipped to respond to a changing work environment.
The Stoller management team at the ICDF was instrumental in involving stakeholders at critical moments during the planning phase so that tight schedules could be met. One concern was adequate load spread over the existing anchor trenches at the ICDF. Stoller mitigated this concern by closely examining the engineered load calculations and by preemptively placing an additional 3 feet of protective gravel over this area. Both CWI and Stoller understood how important it was for the subcontractors to be allowed to work uninhibited while executing a job of this magnitude, therefore they limited the number of necessary personnel at the active work sites. This was accomplished through careful coordination with all support groups, active barriers controlled by an entry person, training and communication at morning meetings. All parties involved deserve credit— if any single aspect (engineering, safety, RadCon, QA, IH, packing and trucking, and security) had been missed it could have resulted in lost time, personnel injury or contamination.
About the Author:
Patrick Burke, VP of BD at Clauss Construction, has been performing complex D&D, demolition and remediation projects within the DOE and DoD for 15 years. He began his career while enrolled at Bowling Green State University, and completed his BA in Environmental Policy and Analysis with a minor in In-Situ solidification through a paid internship at the River Raisin Superfund site located in Monroe, Michigan, U.S. His assignments have led him to work at the Rocky Mountain Arsenal DoD site, Rocky Flats, Hanford Reservation, Nevada Test Site and the INL as a subcontractor during technically challenging projects, including decontamination, demolition and explosive demolition. Burke takes a hands-on approach to ensure that projects are bid, planned and executed to his clients’ standards without losing sight of fiscal responsibility.
Tags: Argonne National Lab, best practices, D&D, decontamination, Department of Energy, hot cell, Idaho Cleanup Project, innovation, nuclear decommissioning, safety, Transport, Warren Environmental, waste management