COVER STORY | HANFORD


Big changes at Hanford


The last couple of years have seen the skyline change at the US Hanford site. The next are likely to see changes underground, as a complex new low-activity waste management system gears up to tackle waste-filled storage tanks


AT THE HANFORD SITE IN Washington state, USA, more than 20 million pieces of fuel were fabricated for nine nuclear reactors along the Columbia River. Five reprocessing plants in the centre of the site processed 110,000 tons of fuel from the reactors, discharging an estimated 450 billion gallons of liquids to soil disposal sites and 56 million gallons of radioactive waste to 177 large underground tanks. Plutonium production ended in the late 1980s and


cleanup began in 1989, when a landmark agreement was reached between DOE, EPA, and Washington State. The Tri- Party Agreement established 161 milestones for completing cleanup. The Comprehensive Environmental Response, Compensation, and Liability Act of 1980 set in place a regular 5-year review of remedial actions at the site. Each 5-year review evaluates a remedy’s implementation and performance to determine whether the remedy is or will be protective of human health and the environment. Thirty cleanup projects, primarily focused on remediating


contaminated soil and groundwater, are currently subject to these statutory reviews. More will be included as remedies are selected and documented in formal records of decision. By the 2016 review the site had already made significant


progress. Since 1989, when cleanup began, the active footprint had been reduced from 586 to 82 square miles. Spent nuclear fuel totalling 2300 tons had been moved to dry storage and 20 tons of plutonium removed from the Plutonium Finishing Plant and shipped offsite. Of the nine production reactors, six had been ‘cocooned’ and one preserved.


The next Cercla review, covering the five years from 2016


to 2021, is due this year. Some major pieces of work have been under way in the period, latterly despite restrictions due to COVID-19.


Stabilising underground materials In October and November 2018 crews worked mostly at night to place 4434 cubic yards of engineered grout into a tunnel near the Plutonium Uranium Extraction (PUREX) facility. The tunnel had partially collapsed in May, requiring an emergency response and shutting down work at the site for two days. The grout was flowed the length of the tunnel and


around contaminated equipment inside. It was injected in several layers, and each was allowed to set before the next began. A foot of space was left between the topmost layer and the ceiling of the tunnel In April 2019 contractor CH2M HILL Plateau Remediation


Company (CHPRC) completed grouting a second tunnel next to PUREX. Tunnel 2 contains 28 railcars with contaminated processing equipment and materials generated during Hanford’s weapons production era. Grouting was determined to be the best choice for stabilising the tunnel after an engineering evaluation of Tunnel 2 showed it was at high risk of collapse, as had happened at Tunnel 1. Approximately 40,000 cubic yards of grout were placed in the tunnel. As with the first tunnel, the grout was injected in several layers, and each lift was allowed to set before the next began. This significantly reduced the risk of a collapse and possible release of radioactive materials. “Even though the tunnel is full of grout, this does not


preclude future remedial actions or limit final closure decisions,” said Joe Franco, DOE deputy manager for the Richland Operations Office. “It just means the risk to people and the environment is significantly reduced while those decisions are made.” In April 2020 CHPRC awarded a $3.9 million subcontract to


White Shield, of Pasco, Washington to design, engineer, and install a system to stabilise three underground structures at the Hanford Site’s Central Plateau by filling the structures with engineered grout. The three underground structures are the 216-Z-2 Crib,


216-Z-9 Crib and 241-Z-361 Settling Tank, and are located near the former Plutonium Finishing Plant (PFP). The structures received liquid waste during Hanford’s plutonium production operations and contain residual radioactive and chemical contamination. Initial work was conducted via email or conference call.


Above: Grouting PUREX tunnel 1 Photo credit: US DOE 22 | May 2021 | www.neimagazine.com


After some post-demolition activities at the PFP, trucks will deliver engineered grout to be pumped into the structures


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