FERNALD K-65 SILOS - BACKGROUND
The Fernald Feed Materials Production Center (FMPC) refined enormous quantities of uranium ores, producing over 500 million pounds of high-purity uranium metal during its Cold War years of operation, 1951 to 1989. The 1050 acre facility is located 18 miles northwest of Cincinnati, Ohio and sits above the Great Miami sole source aquifer, a major regional drinking water source.
Fernald site - looking north
Fernald's silos 1 and 2 contain approximately 6,100 cubic meters of high activity K-65 residues which contain approximately 4,700 Ci of Ra-226 (about 2.5 times the radium present at the NFSS), as well as 600 Ci Th-230, and 1900 Ci Pb-210, plus large quantities of leachable metals, primarily lead. The huge activity of Ra-226 is decaying to radon gas which is present in the airspace below the roofs of the silos at concentrations of 10 to 30 million pCi/L. (Note: the EPA indoor air action level is 4 pCi/L.) The current inventory of radon in the headspace is ~10 Ci in Silo 1 and ~13 Ci in Silo 2. Currently the radon release from Silo 1 is ~38 Ci/yr and from Silo 2 is 50 Ci/yr. Due to the high energy gamma emissions from the radon progeny, up to 1.7 MeV, the dose rate on the surface of the silo domes is very high, in the 50 to 100 millirems per hour range, i.e. ~10,000 times normal background radiation exposure, or a lifetime's normal background in 100 hours.
The contents of Silo 3, often identified by DOE as "cold metal oxides", are actually a mixture of the same high activity K-65 residues with various low activity ore tailings. The high radium and thorium concentrations of the K-65 residues are reported to have been diluted by the addition of the other materials (Operable Unit 4 Plan, DOE/EIS-0195D).
In the 1960s an earthen berm was placed around Silos 1 and 2 to reduce the radiation dose rate out the sides of the silos, and to counter the outward stresses on the concrete sides of the silos. The berm was enlarged in the 1980s. These actions left only the tops of these silos exposed. (Silo 3 is in the center of the photo with unused Silo 4 to its left; white-topped Silos 1 and 2 are at right-background.)
During the early 1990s, bentonite clay was pumped into the silos on top of the K-65 material in an attempt to reduce radon emanation out of the waste into the headspace and ultimately out of the silos. The bentonite soon dried out and cracked thereby restoring a high radon emanation rate. It then presented additional difficulties to the efficient removal and stabilization of the residues.
The 1994 ROD for the Silos unit was the first of several Records of Decision at Fernald. It properly called for maximizing the long-term stability of the waste by vitrifying the residues from all three silos prior to their disposal at the Nevada Test Site (NTS). However, the design chosen for the pilot vitrification facility was an unproven, inexpensive pipe dream rather than the proven method employed at West Valley, NY and Savannah River, GA (See IEER article for details.). The pilot plant was damaged during early testing operations. The $60 million vitrification project was quickly canceled and the pilot vit plant remains were torn down :
Before publicly calling for the inadequate fly-ash cementation fix, DOE floated a very dubious Health Physics Society-backed "medical uses" proposal involving radium extraction. This move added to skeptics doubts that DOE was committed from the outset to providing the best available long-term environmental isolation of the most dangerous of Fernald's waste materials, but went through these motions to gain time to secure DOE-preferred RODs for the other operable units, especially the contaminated soils onsite tumulus. Given their large thorium activity, the K-65 materials will remain extremely hazardous for 100s of thousands of years.