Within a year of opening in 1954, the Bevatron at Lawrence Berkeley National Laboratory had assumed its place in scientific history with the Nobel Prize winning discovery of the antiproton by Emilio Segre and Owen Chamberlain. By the time its work was complete in 1993, the Bevatron had completed a nearly 40-year-long career as a source of extraordinary discovery through countless feats of technology, engineering and experimental physics, including work yielding an additional three Nobel Prizes.
The Bevatron was a 180-foot-diameter particle accelerator located within Building 51, a 125,000–square-foot steel frame building resembling an enormous shed. The entire facility would be demolished to complete the decommissioning, yielding more than 29,000 tons of material that was then transported to the Nevada National Security Site (NNSS) by Cast Transportation for disposal as Low Level Waste (LLW) and Mixed Low Level Waste (MLLW). This material included over 750 concrete shield blocks, as well as pieces of the Bevatron itself, such as beamline pipes, enormous magnets and other steel components, with low levels of radioactivity induced by exposures to neutron and charged particle radiation during decades of Bevatron operation.
Transport of the decommissioned waste out of the area was of particular concern to project management. Two underlying factors became very important as options were considered for demolition waste handling and transport: the necessity of a pristine shipping record for the duration of the project; and challenges that would be imposed by the San Francisco Bay area’s famously damp weather.
Early in the planning stages, a group of citizens concerned about the risks of radiation exposure caused by transport of demolition materials through the city’s streets, lobbied to have the Bevatron “landmarked” in order to stop the demolition, thereby eliminating any risk of exposure. In the end, the site of the groundbreaking scientific machine was given landmark status, but Building 51 and the Bevatron itself were not. Although the group of citizens did not succeed in their efforts to stop the demolition, it was clear to all involved with the project that there would be zero tolerance in the public eye for any failures to keep the waste material contained during transport.
The Bay Area’s lengthy rainy season provided an additional challenge to overcome for the decommissioning team. Average rainfall for the city of Berkeley from November through March is between three inches and six inches per month. As a result, nearly every piece of metal scrap and concrete rubble packaged during those months had to be packaged wet. A large quantity of an effective absorbent material that would meet all of the NNSS stringent disposal criteria was required.
Waste Packaging Challenges
In order to satisfy waste handling requirements, transport requirements, waste disposal criteria and public concerns, careful consideration had to be given to the chosen waste package. It was necessary for the package to be rugged enough to contain unconsolidated concrete rubble and jagged, pointed sections of steel building material and Bevatron components. The package also needed to be impermeable, eliminating the chance of water soaking into it, as well as preventing any material from leaking out, and finally the package needed to be easy to handle, move and load onto the transport trailers.
After an initial trial period testing soft-sided packages produced by several manufacturers, the 9-cubic-yard Nautilus Bag by Strategic Packaging Systems was chosen for the project. The Nautilus line of bags features three layers of construction that combine to provide the necessary toughness: an 8-ounce woven and coated polypropylene outer layer; a 6.5-ounce woven and coated polypropylene mid-layer; and a 12-ounce non-woven geosynthetic polypropylene inner layer.
Water Absorption Challenges
The Nevada National Security Site’s waste acceptance criteria requires zero free liquids in every package, so an extremely effective absorbent material was required to immobilize any rainwater that had accumulated in the Nautilus bags. Project management required a cost-effective absorbent be used due to the sheer amount of absorbent material that would be required. The five to six month rainy season required absorbent to be added to at least half of all loaded waste packages. Because the project spanned during four rainy seasons, the costs of absorbent materials could climb quickly.
Drawing from previous experience in the oil and gas industry, a member of the project’s management team suggested investigating an absorbent polymer product that he had successfully used previously called EnerSorb.
EnerSorb possesses several important characteristics relevant to the application. It is a non-toxic, non-hazardous anionic copolymer absorbent, meaning there are no regulatory restrictions to overcome for storage or use of the product. It is packaged in dry granular form, which gels as it absorbs water that it comes into contact with; it will not release the water even when compressed. Finally, the cost per amount of EnerSorb material required to absorb water from each ton of waste material was minimal. For the duration of the project, less than 6 percent of the total packaging costs were from EnerSorb.
Before EnerSorb could be accepted for use as an absorbent in waste packages destined for disposition at NNSS, the material was required to be thoroughly tested and subsequently approved by NNSS. NNSS contracted PermaFix Environmental Services to complete the certification program during the first phase of shipping to the disposal site. PermaFix completed all of the certification testing according to NNSS’ stringent requirements, and gained approval for EnerSorb to be used for the duration of the project.
In total, more than 29,600 tons of Bevatron demolition material was dispositioned from Lawrence Berkeley National Laboratory to NNSS in over 1,420 shipments. Each shipments consisting of one or more individual waste packages began its journey on the winding roads of LBNL in the Berkeley Hills, making its way safely through the City of Berkeley, before travelling east across the desert to arrive at its final destination in Nevada.
As of February 1, 2012, approximately 75 percent of the total shipments that required packaging have been completed using the Strategic Packaging Systems’ 9-cubic-yard Nautilus Bag with EnerSorb absorbent. Using this extremely effective combination of a robust waste bag with the non-toxic copolymer absorbent, Clauss Construction and Safety & Ecology / Perma-Fix Environmental Services will have successfully completed the decommissioning of one of the most important scientific instruments in the history of the world, with zero lost time incidents, zero SPS package failures, and zero contamination events. The project also boasts an impressive safety record with over 230,000 hours and over 1,300 days worked without a lost time injury. The project is on track for completion in the first quarter of 2012, thereby freeing up much-needed space for Lawrence Berkeley National Laboratory to continue moving forward with their next generation of ground breaking experimental physics.About the Author:
Kevin Smallwood is project manager/RSO at Perma-Fix/SEC.