The Savannah River Site’s main waste processing facility will be offline for much of the year to allow for replacement of a key component.
The Energy Department said on Feb. 3 that site liquid waste contractor Savannah River Remediation (SRR) is preparing to replace a melter in the Defense Waste Processing Facility (DWPF), which converts highly radioactive waste stored at the South Carolina facility into a solid glass form for storage. The facility is designed to process over 30 million gallons of sludge and salt waste stored in more than 40 waste storage tanks, a byproduct of Cold War nuclear weapons operations at SRS. To date, DWPF has solidified approximately 61 million curies of radioactivity and poured over 16 million pounds of glass. It is expected to remain in use for another 20 years.
Melter 2 is a 65-ton refractory-lined melting vessel that receives the high-level waste, then combines with a mixture known as borosilicate frit to remove contamination. When heated in the melter, these elements form a molten glass, which is then poured into stainless-steel canisters for safe storage.
Melter 2’s heater stopped functioning on Feb. 1 and cannot be repaired, according to a DOE press release. SRR is expected to need six months to install the replacement system, Melter 3. The job is expected to cost about $3 million, a DOE spokesperson said.
“DWPF will not be operational again until Melter 3 begins its work,” the spokesperson said by email. “There is a short-term impact to sludge and salt production since DWPF is involved in both processes but poses no additional risks. However, in terms of the lifecycle of liquid waste work, this outage will have little, if any, impact. These outages are factored into the Liquid Waste System Plan.”
DOE in 2015 pushed back the anticipated completion of liquid waste cleanup at Savannah River from 2042 to 2065, with the cost surging to $25 billion more than the original estimate. The new cost projection reported in 2015 was between $91 billion and $109 billion.
As the name indicates, Melter 2 was the second melter used at the DWPF. It functioned for close to 14 years, 12 years longer than designed, thanks to a combination of science and engineering efforts. The extended life cycle of Melter 2 resulted in an estimated cost savings of more than $40 million, according to the DOE spokesperson. “The cost savings are calculated based on DWPF needing fewer melters to perform its mission,” the official explained. “At current costs, the total to procure, prepare, and install a replacement melter is estimated at $40-$50 million. If a melter’s expected life is 2-4 years, then Melter 2’s 14-year run means at least 1-2 melters may never have to be funded.”
Melter 1 provided roughly six years of radioactive operations during the DWPF’s two decades of operations to date, preceded by two years of “non-radioactive simulant processing,” the press release says.
“Melter 2 has poured 2,819 canisters during its life, more than double what Melter 1 produced in its life span, which was 1,339 canisters,” DOE said in the release. “Melter 1 was placed into radioactive operation in March 1996, following approximately two years of non-radioactive simulant operations. Melter 2 began operating in 2003. Together, Melters 1 and 2 have poured 4,158 canisters through January 31, 2017. The predicted number of canisters needed to dispose of SRS’ high-level tank waste is 8,170.”
Removing a melter involves disconnecting it from all associated auxiliary equipment, placing it into a steel box, and loading the box onto a specially designed railcar. The box is then moved about 300 hundred yards from the facility and placed into a concrete-lined underground burial area for interim storage. “This interim storage area has a concrete top that keeps workers safe from any residual radiation, and the area is monitored,” the spokesperson stated. “There are no risks to the public, workers, or the environment during melter replacement or interim storage.”
After removing Melter 2 from the facility, auxiliary and other equipment will be replaced, and the new melter will then be placed into the facility, reconnected, and tested before operations begin.
Melter 3 is on site and has been ready for years. SRR always keeps one melter on hand in the event that the operational melter ceases functioning. Melter 4 is stored in a secure mock-up facility on-site and is undergoing final preparations to be placed on standby, the spokesperson said.
ndergoing final preparations to be placed on standby, the spokesperson said.
