When a concrete containment facility is designed and constructed to be leakproof, cracks are an obvious concern -- especially if the structure is to hold low-level radioactive waste.

In 1995, under a contract with the Department of Energy, Lockheed Martin Energy Systems, Oak Ridge, Tenn., was the facility manager responsible for operating three waste-containment sites on the Oak Ridge Reservation, including waste facilities for Oak Ridge National Laboratory. DOE policy requires all tanks, storage and unloading areas to have adequate secondary containment to prevent the release of chemicals or waste into the environment in case of a spill. But surface cracking in the concrete basins and floor slabs with dikes used to store waste on the reservation has raised concerns about the long-term performance of these structures.

In the fall of 1995, Lockheed managed the construction of a one million gallon surge tank for containment of low-level radioactive liquid wastes generated by research and operating activities at ORNL. For the concrete basin used to contain this steel tank, the company significantly reduced shrinkage cracking and the number of joints required by using a concrete made with Type K expansive cement. Because of the unique characteristics of Type K concrete, special procedures were required for concrete placing, finishing and curing. Though a few problems arose during basin construction, the project was a success overall and provided valuable insight into the use of Type K concrete for waste-containment structures.