Dismantling an early nuclear reactor: a first
| Richland, Wash.
The US Department of Energy (DOE) is preparing to dismantle one of the original nuclear reactors at the Hanford Reservation near Richland. It will be the first time that a full-sized, production reactor has been decommissioned, although several small, experimental reactors have been torn down, says Wally Ruff, project manager for UNC Nuclear Industries, a major DOE contractor here.
The experience gained from this project could help demonstrate that the technology exists for tearing down the 71 commercial nuclear reactors now operating in the United States as each reaches the end of its 40-year span of usefulness.
Accused for years of dragging its feet on decommissioning, the DOE has formulated a program that will eventually result in the removal of 400 federal nuclear facilities, including about 50 "significant" projects like the old Hanford reactors.
Some years ago the Energy Department decided that the F reactor, the one closest to Richland, would be dismantled first. Built in 1944 to produce plutonium for the first atomic bombs, the reactor was retired in 1965.
In the last 1960s all the salvageable, nonradioactive equipment, such as pipes, valves, and controls, were stripped from the plant and sold as scrap. Later the noncontaminated auxiliary buildings were torn down.
All that is left is the reactor building itself, surrounded by a chain-link fence and sagebrush, in a remote corner of the 570-square-mile nuclear reservation.
The first significant appropriation to buy the needed equipment and hire people to begin work is expected this year. Actual dismantling of the reactor core will begin in January 1982 and be completed in 1984, according to the current schedule. The total cost: about $32 million.
The highly radioactive fuel was removed from the core long ago, but there remain traces of long-lived elements like plutonium, which takes more than 200, 000 years to decay, from previous fuel element ruptures.
But most of the radioactivity is contained in the tons of graphite and iron that make up the core and shielding, materials subjected to 20 years of constant radiation bombardment.
Many of the shorter-lived elements already have decayed. But radiation from others, like Carbon 14, which requires some 50,000 years to decay, won't decrease by appreciable amounts in the next few years.
"There's no real reason to wait any longer," Mr. Ruff says. The Hanford reactors are no longer useful, they cost money to take care of, and "ultimately we have to do this anyway," he adds.
UNC engineers are considering two ways of dismantling the reactor, which is as big as a four-story building. In one method, operators would sit on top of th reactor in a shielded shed, using cranes to remove the radioactive materials.
In another plan, technicians would plug all the holes and then flood the core with water, removing the contents from the top. Engineers are leaning toward this method because water provides an effective shield to protect workers and prevents the spread of contaminated particles.
The F reactor core is made up of chunks of graphite laid on top of each other , log-cabin fashion. Engineers would remove them one at a time, package them, and ship them to another location on the Hanford reservation for burial as low-level waste.
More than 4,000 cubic feet of graphite, plus large chunks of radioactive iron , will have to be disposed of in this manner, officials say. Very likely, the wastes will be buried in a way that they can later be recovered and permanently buried in a deep underground repository such as one of the government is proposing to build in New Mexico, Mr. Ruff says.
The program is designed to return the land F reactor now stands on to its natural state, allowing for other uses. One is possible construction of a new Columbia River dam, a project that has been sytmied in part because of concern that it might flood several of the old reactors.
The Hanford reactors are not designed like modern commercial reactors, but some of the decommissioning techniques developed during the F reactor project should be directly applicable, Mr. Ruff explains.
Scientists at Battelle Northwest Laboratories, a research institution here, are working on a special underwater saw to cut through radioactive metal. The saw could be used on civilian reactors.
Moreover, the DOE also is preparing to decommission the prototype light water reactor at Shippingport, Pa., and that experiences should be directly applicable to civilian reactors, Mr. Ruff says.
Nobody knows for sure how much it would cost to tear down a full-sized nuclear power plant, such as the ones on Three Mile Island in Pennsylvania. Some have speculated that up to 20 percent or more of the original cost of building the plant would be required.