With the 2016 fiscal year in the rearview mirror, Bechtel National is looking ahead to finishing this fall a key gas-treatment system needed to start liquid-waste cleanup at the Energy Department’s Hanford Site as soon as 2022.
Bechtel is designing a system dubbed Direct Feed Low-Activity Waste (DFLAW) to take the less viscous, less radioactive liquid waste from Hanford’s underground tank farms directly into enormous melting pots, where it will be mixed with glass to form a more easily storable solid.
The process creates toxic, radioactive exhaust gas that must be scrubbed before it is vented into the atmosphere: a task accomplished by the the Low-Activity Waste plant’s melter off-gas treatment system.
Two of the off-gas treatment system’s mission-critical components — the thermal catalytic oxidizer and the ammonia dilution skid — were installed this summer. The third and final critical piece, a caustic scrubber, “is expected to arrive in November with installation to be completed in early 2017,” Todd Nelson, spokesman for Waste Treatment Plant (WTP) prime contractor Bechtel National, wrote in a Thursday email.
“By the end of this year, we will have received all of the major pieces of engineered equipment for the [Low-Activity Waste] Facility,” Peggy McCullough, Bechtel’s project director for the Waste Treatment Plant, said in a Tuesday press release announcing the milestones. “It puts us in an excellent position to declare ‘construction complete’ in 2018.”
Par for the course at WTP, where serious safety allegations prompted the department to halt construction of the plant’s High-Level Waste facility in 2012, the Low-Activity Waste plant’s off-gas treatment system has been treated with an abundance of caution and garnered special attention from DOE, including from the agency’s Office of Enterprise Assessments.
In a 2015 report that parsed hundreds of hypothetical disaster scenarios for the off-gas system, the internal DOE infrastructure inspector examined a number of “potentially high consequences from accidents involving these systems,” such as radiological releases or — most dangerous to the off-site public — toxic ammonia spills.
Bechtel National also touted Tuesday completion of the Low-Activity Waste facility’s two massive, 300-ton melter pots. The pots have not yet been delivered to Hanford, though a full-scale test vessel arrived in July and was installed at the site’s Full-Scale Vessel Test Facility. Non-nuclear tests are scheduled to continue there through 2017.
While some basic infrastructure such as buildings and utilities are already in place at WTP, the contractor is still finalizing the overall design for DFLAW itself. That design work, expected to cost just over $40 million, according to the company’s WTP prime contract, should be finished by May 31, 2017, McCullough said in August.
As for construction bottlenecks, the Low-Activity Waste plant’s Effluent Management Facility, which will treat slightly radioactive liquid water left over from the vitrification process, is the big one. Bechtel broke ground on the facility in December 2015 and plans to finish commissioning the facility — verifying that the completed plant is ready to process nuclear-contaminated material — in 2020.
Bechtel National is building WTP under a DOE contract that began in 2000 and is now worth about $11.5 billion. The value of the pact is all but certain to rise, as Bechtel needs a contract modification to build and install DFLAW infrastructure not already in place at Hanford.
The Waste Treatment Plant is designed to turn some 56 million gallons of mostly liquid chemical and radioactive waste left over from Cold War-era plutonium production — both low-activity waste and more viscous, radioactive high-level waste — into glass canisters in a process known as vitrification.
Treating low-activity liquid waste before treating high-activity waste is a departure from DOE’s original plans. The agency is legally under the gun to start high-activity waste treatment by 2036, a federal judge in Washington ruled in March. Vitrified low-activity waste will be disposed of permanently on site, DOE has said. The agency has not yet decided how to dispose of all the glass-immobilized high-level waste WTP eventually will produce.
