The Foster Wheeler Environmental Corp., the company that has been contracted to clean up two of the silos at the Fernald site, is about to put a system in place that will remove the silos’ contents without leaking high levels of radon.
The silos contain about 8,900 cubic yards of low-level uranium ore residues that emit radon. Radon is an odorless, colorless radioactive gas that, in high levels, has been linked with lung cancer. It is produced by the decay of naturally occurring uranium and thorium in the soil.
But at the former Fernald uranium-processing plant in Crosby Township, which operated from 1953 until 1988, the radon is from radium in the silos at high concentrated amounts. The Centers for Disease Control and Prevention released a study last year that reported the radon gas leaking from the silos caused the largest health risk to residents surrounding the site.
“The material in the silos is unique, it’s the only material like it in the world,” said Wayne Potter, engineer manager for the company. “The process and technique (for cleanup) has a long history. We are using similar applications of past practices. The material is new to us, but the technique is not.”
The New Jersey-based company received a $50 million, four-year contract from the U.S. Department of Energy (DOE) on Feb. 26 to remove the potentially deadly sludge wastes from two concrete silos at the site. The contract calls for the company to design, build and implement the retrieval system and a transfer system to remove the radium-bearing waste from the two silos and place it into new storage tanks. The company already has a preliminary design in place, Potter said.
“Because the material is unique, there have been a number of samples and tests that have been done on the material so that we will be prepared,” he said.
And the unique material calls for some other preparation, Potter said.
There are two other silos at the Fernald site. One contains about 5,100 cubic yards of cold metal oxides and the other is empty. Potter said that the empty silo will be useful to gain experience in dealing with the silos and the removal procedure.
“There is a significant advantage to having that extra (empty) silo there because it gives us the ability to have a full-scale mockup system,” Potter said. “We can field an exact replica on the fourth silo, and we can verify the operation.”
The first part of the process of removing the waste from the silos, he said, will involve the radon control system. The company will use negative pressure to remove the gas and will remove the radon from the gas through carbon filters.
“It will be a completely sealed air-lock system where there will be two layers of pipes,” Potter said.
The reason for a pipe-within-a-pipe system is to make sure the gas cannot escape, he said.
The retrieval system for the solid waste in the silos will use a hydraulic retrieval process and a slurry pumping system. The waste water generated from this process will be collected and treated before it is discarded.
“These silos are fragile and were not meant to hold this type of material for this long,” Potter said.
Because of this, the company will use only openings that already are in place on the silos. ©
This article appears in Mar 24-30, 1999.