The Challenge of Decommissioning a One-of-a-Kind Reactor

The spent fuel cask will be moved from the dome-shaped reactor building using a heavy-duty overhead crane. A special “crawler” vehicle (not pictured) will move the fuel cask to a secure storage pad.

Correction: Allis-Chalmers build three reactors – Elk River (operated 1964-68), PathFinder (never achieved full power) and La Crosse (operated 1967-1987). They were all designed as commercial nuclear plants but La Crosse was the only one that operated for a significant amount of time.

Early nuclear power plants in the United States were custom designs, but the LaCrosse Boiling Water Reactor in Wisconsin was truly unique in both its design and construction. That uniqueness has carried over into the work to decommission and dismantle the plant.

Owned by the Dairyland Power Cooperative, the facility on the Mississippi River near Genoa, Wisconsin, is very small — producing just 50 megawatts of electricity — compared to 1,000 or more megawatts from later reactor designs. It was one of several demonstration reactors funded, in part, by the Atomic Energy Commission, the predecessor to the NRC. The plant was completed in 1967 and operated until April 1987. It was the only reactor built by Allis Chalmers, a company best known until the mid-1980s for its tractors and farm equipment.

In the 25 years since the plant was shut down, the NRC has monitored and inspected activities at the plant to assure continued protection of public safety and the environment. NRC requirements have also remained in place to maintain security at the facility.

Since shutdown, the plant has been maintained in a safe and secure condition until the plant can be fully decommissioned. In 2007 the 310-ton reactor vessel was removed from the plant and shipped to South Carolina for permanent disposal.

Spent fuel from the reactor’s 20 years of operation has been safely housed in the plant’s spent fuel storage pool. The Dairyland Power Cooperative has been developing plans over the past several years to transfer that fuel into five concrete and steel storage casks for interim storage on a specially constructed concrete pad at the site. Similar dry cask storage systems are in use at about 65 sites across the country.

Moving that fuel, however, has posed special challenges for this unique facility. The pool holding the spent fuel is too small to accommodate the cask used to load and transfer the spent fuel. Faced with the lack of space in the spent fuel pool itself, LaCrosse engineers devised a unique solution of converting the structure that formerly housed the reactor into a cask loading pool. The former reactor structure, which adjoins the spent fuel storage pool, will be filled with water for the cask loading. Once the cask is loaded, the loading pool will be drained and a gateway opened. A heavy-load overhead crane will move the cask outside the loading area.

Throughout the process, NRC engineers and inspectors have evaluated each step, including review of the construction of the storage pad and modifications to form the cask loading pool. All activities are assessed to assure that the unique concepts can be safely implemented for workers, the public, and the environment.

Before actually loading and moving the spent fuel, plant personnel are performing “dry runs” without actually loading the fuel assemblies to assure that the cask loading and transport equipment and procedures are ready for safe movement of the fuel. NRC inspectors have been on site to inspect these “dry run” activities.

The actual fuel movements will begin later this summer and NRC inspectors will be on hand to inspect the loading and movement of at least the first of the five casks.

Christine Lipa, Chief
Materials Control, ISFSI and Decommissioning Branch
Region III