Fernald Silos


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). This 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 20 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).

In the 1950s an earthen berm was placed against the silos to reduce the dose rate out of the sides of the silos, and to reduce the stress on the concrete sides of the silos. Currently only the tops of the silos are exposed.

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, which soon dried out and cracked restoring a high radon emanation rate, now presents additional difficulties to the efficient removal and stabilization of the residues.

The initial Record of Decision at Fernald properly called for maximizing the long-term stability of the waste by vitrifying the residues 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. The pilot plant was destroyed during early testing operations. The vit project was quickly canceled. (See IEER article for details.)

Before publicly calling for the cementation fix, DOE floated a 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. Given their large thorium activity, the K-65 materials will remain extremely hazardous for 100s of thousands of years.