The Department of Energy plans to try a new way to "cocoon" its next defunct Hanford reactor, putting up a steel building around it.
DOE already has made significant progress toward putting eight of Hanford's plutonium production reactors into temporary storage to let radiation decay to more manageable levels over 75 years. The ninth reactor, B Reactor, will be saved as a museum.
To cocoon the C, D, DR, F and H reactors, DOE tore down reactor structures to the radioactive shield walls around radioactive cores, sealed any openings and reroofed them before welding shut the doors. Work on a similar cocoon almost is complete at N Reactor.
But now DOE is planning to try building an enclosure around the K East Reactor, the next reactor scheduled to be cocooned.
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Worker safety is the main reason to switch to the new plan, said Tom Teynor, DOE project director.
The K East Reactor is larger than some of the earlier reactors that were built along the Columbia River as part of the nation's nuclear weapons program.
Piping and other penetrations are 80 to 100 feet off the ground, a high elevation for workers who would have had to put in concrete forms and pour grout to seal them. The openings still will be sealed off, but with steel plates.
Reroofing the reactor, as has been done at previous reactors, might have required extensive wall and ceiling bracing from inside the reactor, where workers would face potential radiation exposure.
Because the roof of the enclosure will not be attached to the reactor, no structural changes to the building will be required.
Work still will be done inside the reactor to remove lead, oils and other hazardous substances. Ancillary structures, including the reactor basin, already have been torn down.
The planned enclosure will be constructed of steel sheeting and have a roof designed at an angle to direct rain water runoff away from adjacent waste sites, according to DOE.
Cocooned reactors now are gray concrete with shiny metal roofs, but DOE has discussed making the enclosures earth toned to better blend into the surrounding desert landscape. The tribes have raised issues about the appearance of Hanford buildings, DOE said.
The cocooned reactors now can be seen by boaters along the Columbia River and from parts of the Hanford Reach National Monument. DOE is planning to have most environmental cleanup along the Columbia River completed in 2015 and most land will be left as natural shrub steppe habitat.
Building an enclosure also could save money. DOE estimates enclosing the K East Reactor in a steel shell would cost about $3.6 million less than estimated cost of about $20 million for the traditional method of cocooning. Much of the cost savings comes from not having to do engineering and construction for structural bracing.
Work to cocoon the K East Reactor is scheduled to begin in 2013, although some work is starting now to seal off below-grade piping. Hanford contractor CH2M Hill Plateau Remediation Co. is expected to ask for bids for construction soon, Teynor said.
Work should be completed in May 2014, about nine months sooner than under the old method, he said.
After K East and N reactors are in storage, that only will leave work at the K West Reactor, which cannot be cocooned while radioactive sludge still is being held in underwater containers in its basin.
None of Hanford's plutonium production reactors has operated since 1987.