The lead liquid waste contractor at the Savannah River Site near Aiken, S.C., on July 18 finished building the Saltstone Disposal Unit- (SDU) 6: the first of seven planned 30-million-plus-gallon tanks that will store radioactive salt waste left over from processing some 35 million gallons of Cold War liquid waste, the Department of Energy said last week.
SDU-6 is supposed to be operational by February 2018, according to DOE’s 2016 Savannah River Site (SRS) liquid waste management plan: the latest iteration of the annual plan available at deadline for Weapons Complex Monitor. The Department of Energy estimates it will take until October 2021 to fill up the tank. DOE and Savannah River Site prime liquid waste management contractor Savannah River Remediation started building SDU-6 in 2013, according to the latest liquid waste system plan.
In a July 21 press release, DOE said SDU-6 was completed at a cost of about $118 million, roughly $25 million less than what the agency thought the unit would cost when construction began in 2013.
SDU-6 is about 10 times larger than the previous six saltstone disposal units at the Savannah River Site, according to DOE’s press release.
SDU-6 hit a few hiccups along the way to construction completion. DOE thought it might finish building the unit last year, but that hope was dashed when, in May 2016, the agency and its contractor discovered a leak during a planned leak test. After multiple fixes, SDU-6 turned a corner in December, when the department reported the massive vessel appeared leak-free.
Meanwhile, DOE has already started construction on SDU-7, which the agency expects to cost between $110 million and $170 million to build, and take until late 2021 — the first fiscal quarter of the government’s 2022 budget year — to finish. That is according to DOE’s 2018 budget request.
SDU-6 eventually will be a permanent disposal unit for low-radioactive salt waste found in the SRS storage tanks. This waste will be separated from liquid nuclear waste now stored in the underground tanks. Salt waste constitutes about 90 percent of the total waste, which is left over from production of fissile material for Cold War-era nuclear weapons.
The Salt Waste Processing Facility that will treat SRS liquid waste is scheduled to begin operations in December 2018. Parsons Government Services is building the facility under a $2.1-billion contract awarded in 2002 and set to expire in 2020.
The process of isolating salt waste from the tanks, plus mixing it with cement-like grout, substantially increases the volume the waste takes up, a DOE spokesperson said Thursday. Treatment will create some 120 million gallons of salt solution, each gallon of which turns into 1.76 gallons of grout-plus-salt-waste before it is poured into a Saltstone Disposal Unit, the spokesperson said.
Savannah River Remediation’s cleanup contract was awarded in 2009 and, following a six-month extension announced in April, is now worth almost $4.5 billion through through Dec. 31. DOE announced the extension around the time the agency was expected to award a follow-on contract valued at an estimated $6 billion over 10 years, including options.
