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Collapsed Nuclear Site Tunnel Stabilized

Friday, November 17, 2017

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The U.S. Department of Energy announced this week that the waste storage tunnel that collapsed at its Hanford Nuclear Site in May has been stabilized.

Workers filled the partially collapsed tunnel with engineered grout, the DOE said, finishing the job Nov. 11. The job was carried out by CH2M HILL Plateau Remediation Company, a longtime contractor at the site.

Hanford Site
Tobin Fricke, CC BY-SA 3.0, via Wikimedia Commons

The collapse of a storage tunnel at Hanford Nuclear Site, in Washington, resulted in a Site Area Emergency in May.

The collapse took place near where two tunnels used to store contaminated equipment meet. According to a report prepared by CH2M for the DOE, Tunnel 1 was constructed in 1956 and is 358 feet long, with space for up to eight railcars. It was built of creosote-pressure-treated Douglas fir timbers, with part of one wall constructed with reinforced concrete. The tunnel was filled with railcars by 1965.

Tunnel 2 is larger—nearly 1,700 feet long, with space for up to 40 railcars. It was built with a structural steel material after initial construction resulted in structural failures. It was finished in 1964, and holds 28 railcars, the final of which was placed in 1996. Waste in the railcars stored in the tunnels includes mercury, cadmium, silver, barium and lead, according to CH2M.

Both tunnels are covered in about eight feet of soil.

The exact cause of the collapse, which took place in Tunnel 1, couldn’t be determined, according to the report, but it likely was related to the deterioration of the timbers under rainfall.

Hanford site tunnel collapse
Images: Department of Energy unless noted

The collapse occurred in Tunnel 1 near where it meets the longer, more recently constructed Tunnel 2.

The collapsed area in Tunnel 1 was shored up with the grout fill; an analysis found that Tunnel 2 does not fit current standards for structural integrity, so that tunnel will be stabilized as well.

The stabilization of Tunnel 1 was carried out ahead of schedule and without injuries, CH2M noted.

The Incident

The collapse was first discovered May 9 during a routine inspection on the nuclear site, which operated for more than 40 years and has been undergoing cleanup since 1989. Workers at the nearby Plutonium Uranium Extraction Facility, known as PUREX, were told to shelter in place when the problem was uncovered, because it was unclear whether radioactive waste might escape from the collapsed tunnel.

The incident triggered a Site Area Emergency, officials said, which indicates that an event could affect personnel beyond the immediate facility where it has occurred, but not beyond the boundaries of the 586-square-mile Hanford Site.

Hanford tunnels construction

Tunnel 1 was finished in 1956 and was filled with waste-contaminated railcars by 1965; Tunnel 2 was finished in 1964.

Monitoring was carried out over a half-mile radius around the spot of the collapse.

About the Site

Constructed in 1943 and 1944, the Hanford site, on the Columbia River in eastern Washington, was the world’s first plutonium production site. It was where the first nuclear bomb ever tested was built. The last reactor on the site closed in 1987, according to the DOE, and in 1989, the government began a large-scale cleanup effort.

The site has been subject to considerable controversy in recent years, related to both environmental concerns and alleged improprieties committed by contractors.

At least six of the 177 tanks storing radioactive waste on the site are leaking, an issue that officials say does not currently pose a threat to human health. Over the years, at least 67 of the tanks have leaked a total of at least 1 million gallons of waste, according to the Washington Department of Ecology.

Last year, two contractors, Bechtel National Inc. and AECOM Technology Corp. (which bought Hanford contractor URS Corp. in 2014) settled with the Department of Justice to the tune of $125 million over charges that Bechtel and URS did subpar work over more than a decade at the site, charging the DOE for higher-quality materials than they actually used.


Tagged categories: Accidents; Grout; NA; North America; Nuclear Power Plants; Program/Project Management

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