"Reactorsaurus" to Dismantle U.K. Nuclear Plant

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Researched by Industrial Info Resources (Sugar Land, Texas)--The redundant Dounreay nuclear power complex, built in the 1950s to further the United Kingdom's efforts in nuclear power development, is getting ready to begin decommissioning operations. The project and maintenance team have designed a 75-ton device named "Reactorsaurus," with large arms and moving photographic eyes to dismantle the plant and associated infrastructure. The arms of Reactorsaurus consist of two remotely operating manipulators, which can reach depths of 16 meters into the reactor vessel. The arms can do a wide range of activities including oxy/propane and plasma cutting, managing tools such as diamond disks and wires, hydraulic shearing and size reduction. Six built-in radiation-proof cameras will relay sound and images to the control room.

The project team plans to carry out trial operations at an offsite test facility using a life-size prototype to avoid environmental impact. This activity will not only assist in identifying challenges, but also will enable development of procedures and techniques for smooth execution of operations onsite. The process will also help in evolving size-reduction methodology and the training of operations staff.

The contract for the mock-up construction of the device is expected to be awarded this year. The actual construction is estimated to take around two years for completion, and the device is expected to be ready by early 2013. Dismantling operations will be in line with the site-restoration plan prepared by the Nuclear Decommissioning Authority (Cumbria, United Kingdom).

The redundant Dounreay nuclear reactor site, located in the Scottish Highlands, consists of two fast breeder reactors and one thermal test reactor. The complex also houses chemical plants that were used to recycle fuel from the reactors using the process of chemical separation. Recycled plutonium and uranium from the process were used as new fuel. Nuclear fuel input for the chemical plants was procured from Dounreay as well as other reactors in the U.K. and other countries. On April 1, 2005, the Nuclear Decommissioning Authority took over the Dounreay nuclear site with plans to decommission the plant and bring it to a condition of surveillance and interim care, making it a brownfield site by 2036. The entire operation is expected to cost around $4.37 billion.

Gas, thermal and nuclear power plants are designed with a finite work life, after which they become economically unviable to continue operations. However, the dismantling of nuclear power plants poses several environmental hazards, such as radiation and contamination. Older nuclear plants were built to last 30-40 years, while the new ones can operate for 40-60 years. Decommissioning is an essential part of the post-operative phase of the nuclear power plant. The process makes the site permanently safe, allowing it to be reused later. The International Atomic Energy Agency (Vienna, Austria) has identified three options: immediate dismantling, safe enclosure and entombment, in order to carryout the stripping process. The disassembly of the reactor is one of most critical activities. The sodium coolant and residue is taken out, followed by removal of rotating shield components, neutron shield, rotor and reactor jackets, core lower support structure, peripheral components and core upper structures of the primary vessel and removal of the reactor roof.

According to a report published in 2007 by the World Nuclear Association (London), more than 90 reactors, 100 mines and 250 research facilities have been decommissioned. In a recent publication, the organization indicated that about 60 reactors globally are static, dismantled or in various phases of decommissioning. These include 19 sites in Eastern Europe, 13 sites in the U.S. and Canada, six in Western Asia and 22 locations in Western Europe.

At present, there are about 436 nuclear reactors operating commercially in 30 countries, which contribute about 15% to the global energy needs. As the technology gains popularity and new nuclear power plants are being constructed worldwide, the stripping down of old power plants will become inevitable. It will also become imperative for countries to formulate and follow guidelines set by regulatory bodies to avoid environmental hazards.

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