Treatment of Radioactive Waste
Since the dawn of the nuclear age, solidification/stabilization
has been used to manage radioactive waste. Cement-based S/S treatment
has been used to treat wastes from the production of the first atomic
bomb to the remediation of contaminated Department of Energy sites
today. Here are three examples of the use of cement-based S/S in
the management of radioactive waste.
Fernald Site, OH
The Feed Material Production Center (Fernald Site) is located 18
miles northwest of Cincinnati, Ohio. From 1951 to 1989, the Fernald
site was a uranium processing facility. Its primary mission was
to produce high-purity uranium metal products in the form of ingots,
derbies, billets, and fuel cores for other sites within the nuclear
weapons complex. Other Department of Energy facilities used Fernald
products as fuel for nuclear reactors to produce plutonium.
When operations closed, some of the production wastes remained
at Fernald. In the spring of 2005, cement-based S/S will treat radioactive
waste stored in Silos 1 and 2 for safe disposal. This material was
generated from 1951 to 1960 as a waste by-product from the processing
of high-grade uranium ores. Known as K-65, this material contains
radium and thorium radionuclide. 8,900 cubic yards of high-activity,
low-level waste material will be removed from the two silos, treated
with cement, and shipped off-site for disposal.
Once the waste is removed from the silos, cement and other supplemental
cementitious materials will be blended to create a grout. The mix
design calls for a 20 percent loading of waste (80 percent cement/cementitious
material). This very cement-rich mix design will not only produce
a monolithic waste form but also to provide shielding from radioactivity.
The waste grout mixture will be loaded into 1/2-inch-thick, steel-walled
containers and sealed for shipment off-site. 3,500 trucks will be
required to ship up to 7,000 containers of waste.
|Fernald Site; lower left: Silos 1 and 2, center:
waste solidification building
||Fernald Site: Silo surrounded by berm
||Removing Monolith from Storage Cask, Oak Ridge
Low-Level Waste Shipment to Nevada Test Site
West Valley Demonstration Project, NY
West Valley Demonstration Project is a radioactive waste-cleanup
project located approximately 35 miles south of Buffalo, N.Y. The
site is the location of the only commercial nuclear fuel reprocessing
facility to ever have operated in the United States. Low-level radioactive
waste (LLW) was treated with cement and cast into specially made
drums for storage and disposal. Nearly 20,000 71-gallon square drums
were filled with cement-treated LLW. Temporarily stored at West
Valley, the waste filled drums will eventually be shipped to a permanent
|The low-level salt solution removed from the
high-level waste was remotely blended with cement and placed
in 71-gallon square steel drums to form a durable, solid waste
||Placement of drummed cement-treated LLW in
Weldon Springs, St. Charles County, MO
During the 1950s and 1960s, the facilities at Weldon Spring were
used by the Atomic Energy Commission to process uranium metal. One
by-product of this processing is known as raffinate sludge. This
sludge was stored on-site in four basins known as raffinate pits.
On-site chemical stabilization/solidification (CSS) was identified
as the most effective technology for treatment of the contaminated
sludge. In this process, fly ash and portland cement were mixed
with the sludge to produce a grout.
The full-scale CSS plant began operations in mid-1998. The plant
resembled a concrete batch plant engineered to efficiently handle
sludge and binder to produce grout while controlling particulate
and radon emissions. The sludge contained Uranium-238, Thorium-232,
and associated decay products. The sludge was screened for oversized
materials and then thickened with a polymer before it was blended
with binder materials and transferred to the disposal cell. Approximately
186,000 cubic yards of grout was produced and placed into the engineered
disposal cell. Raffinate sludge cleanup activities were completed
in late June 1999.
|CSS Production Facility at the Weldon Spring
||S/S-treated raffinate sludge pumped into engineered
Photos courtesy of the U.S. Department of Energy.