Public to comment on Hanford tunnel work

Tuesday, 14 August 2018

The DOE says grout - a form of concrete - is the best way to guard against a potential collapse of the PUREX 2 tunnel, which contains contaminated equipment from historic plutonium production activities. Opponents of the method are concerned that the grout would become a permanent solution and argue that the waste should be removed, according to the Department of Ecology.

Two tunnels were constructed in the 1950s and 1960s next to the former Plutonium Uranium Extraction Plant (PUREX) at Hanford, in Washington State. The tunnels - constructed of wood and concrete and covered with about 2.5 metres of soil - were built to hold rail cars loaded with contaminated equipment. Tunnel 1, built in 1956, is about 110 metres long and contains eight rail cars. This tunnel leads into the longer tunnel 2, constructed in 1964 and containing 28 rail cars loaded with contaminated equipment. Tunnel 2 is about 515 metres long.

The tunnels were sealed in the mid-1990s and are checked periodically, but in May 2017 tunnel 1 experienced a partial roof collapse. The tunnel was subsequently stabilised with grout during October and November 2017. A structural evaluation of tunnel 2, carried out by the DOE after the collapse of tunnel 1, found that although the tunnel had been correctly constructed, some components are now stressed above design capacity and are also corroding. This means there is a risk of future structural failure.

Filling tunnel 2 with engineered grout has been proposed to mitigate this risk. Grouting would be an interim measure and would not preclude future closure or remedial decisions, according to a factsheet issued by the Department of Ecology.

The Department of Ecology on 13 August said it had denied a request by DOE to begin grouting before the end of the public consultation period, but has allowed it to begin setting up the equipment needed for the grouting process. "We will wait until the public comment period is complete before allowing grout to flow, unless we see compelling evidence that collapse is imminent," the Department of Ecology Tweeted.

The Department of Ecology is the state regulatory responsible for overseeing cleanup at the Hanford site. "We're striking a balance between the public's right to comment on this important cleanup decision and the need to secure the waste in the tunnel," said Alex Smith, manager of the department's Nuclear Waste Programme, said. "Our highest priority always is safety of Hanford workers and the public, and protection of the environment. But we also strongly support the public comment process. Once grout starts flowing, the public would no longer have any meaningful chance to affect the decision," he added.

The comment period, which will include two public hearings, will end on 27 September.