COVER STORY | HANFORD DFLAW is a system of interdependent projects and


infrastructure improvements, managed and highly integrated as a programme, that must operate together to vitrify, or immobilise within glass, Hanford tank waste. “The waste in the tanks is very complex, and each batch


of waste…must be sampled and analysed to ensure the vitrified end product meets regulatory standards,” said Mat Irwin, DOE Office of River Protection deputy assistant manager for the plant. In December, contractor Bechtel completed construction


of the last of 94 systems that comprise the Low-Activity Waste Facility. At the start of 2021 a third of them had been tested and handed over to plant management for commissioning. The DOE and Bechtel have begun startup testing in the Low-Activity Waste Facility itself. The facility is over 2.5 acres in area and houses two large


V facility (242-Z); fan house/ventilation stack (291-Z) and a plutonium reclamation facility (236-Z). The final activities at PFP include packaging and safe


disposal of rubble from the Plutonium Reclamation Facility (demolished in 2017), core sampling soil beneath the building pads and stabilization of the site with soil cover.


Regreening the site In March 2019 contractor Mission Support Alliance (MSA) revisited 140 acres that had been revegetated but were found in 2017 not to be thriving. Historically, if a location was found to be failing, it


was cleared and planted again. Instead MSA used results from a Hanford Site pollinator study to create a specially formulated seed mix to encourage pollination and species diversity. It implemented supplemental planting (in lieu of full-scale revegetation) to save areas of successful growth. In some areas, it opted for plant flower plugs — small seedlings with a few inches of growth, soil and a root structure — which act as a seed source for the revegetation site.


Top: Aerial view of T Plant where sludge from 105-K West will be stored Photo credit: US DOE


Centre: Aerial view of Hanford vitrification plant Photo credit: Bechtel National, Inc.


Bottom: Startup workers test the LAW Facility’s container handling system Photo credit: Bechtel National, Inc.


Tank management One of the site’s major activities was managing the waste in 177 underground tanks, more than a third of which were thought to be leaking. New technologies to manage these tanks have been developed during the cleanup process, and nine new retrieval technologies had been added to the original technology by 2016. Site managers had begun to address the waste, with 2 million gallons of tank contents transferred to new double-walled tanks. That represents just 4% of the tanks’ total 56 million gallon contents, however, and the Hanford task remains a mammoth one. The tanks had a design life of 40 years and now range in


age from 40 to 70 years. The tanks contain the most complex heterogeneous radioactive waste at any US cleanup site. Waste is in the form of sludge, salts, and liquids. There are 1800 different chemicals in the tank waste and no two tanks have the same combination of waste. Work on the tanks stepped up in 2020 to implement the


Direct-Feed Low-Activity Waste (DFLAW) approach, which will send pretreated waste directly from the tank farms to the Low-Activity Waste Facility at the Waste Treatment and Immobilization Plant for vitrification.


24 | May 2021 | www.neimagazine.com


melters. The melters will vitrify low-activity tank waste after it is pretreated to remove caesium and solids at the tank farms and fed directly to the facility. The Tank-Side Caesium Removal system (TSCR) was delivered in October 2020. The pretreatment system will remove radioactive caesium and solids from tank waste and is critical to DFLAW. In 2021 Bechtel began hiring and training laboratory and


radiological technicians to prepare for cold commissioning of the Waste Treatment and Immobilization Plant. They join chemists hired last year and together will be responsible for analysing approximately 3000 samples of tank waste each year to support direct-feed low activity waste (DFLAW) operations. Fourteen lab spaces will be used to conduct analyses of the elements within the waste, as well as determine the waste’s physical and chemical properties. The results will determine the type and amount of glass-forming materials that will be mixed with batches of tank waste during vitrification. Samples will also be taken throughout the process to confirm the plant is producing high- quality glass. DOE Office of Environmental Management and BNI said the lab is ready for startup. “We expect to have 45 staff working 24/7 shifts in the Analytical Laboratory when DFLAW operations begin,” said Valerie McCain, Bechtel senior vice president and project director. “A second set of 12 lab technicians and 20 radiological technicians will be hired later this spring for commissioning and operations roles.” In November 2020 a $13 million subcontract was awarded


to Fowler General Construction to build a new Hanford Site water treatment facility that will automate water services, and support the tank waste vitrification programme and other risk-reduction cleanup projects across the site. “When we get into 24/7 operations, having an


uninterrupted supply of water and other infrastructure services will be critical, because once we turn the melters on, we won’t be able to turn them off until they are replaced periodically when they wear out,” said Mat Irwin, EM Office of River Protection deputy assistant manager for the Waste Treatment and Immobilization Plant. The new water treatment facility will be able to produce


3.5-5 million gallons of clean water a day. Construction is expected to begin imminently. As for DFLAW as a whole, it will be the most highly


integrated operational programme at Hanford and the Office of Environmental Management says it will require significant upgrades to site infrastructure and coordination and integration among the site contractors. The plan is to begin DFLAW and start making glass in 2023. ■


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