Modeling Stress Strain Relationships and Predicting Failure Probabilities for Graphite Core Components, October 1, 2009 Through September 30, 2012.

摘要

Despite current events associated with the light water reactors in Fukishima, Japan, energy producers continue to look at nuclear power as a viable alternative for power generation. There are several new designs that transcend the older light water reactors that failed to perform safely in Japan. Among the designs for the next generation power plant is the very high temperature reactors (VHTR), molten salt reactors, and super critical water cooled reactors. In addition to generating electricity the VHTR will be able to produce hydrogen without consuming fossil fuels or emitting greenhouse gasses which is a distinct benefit. Emerging technologies often depend on new materials or the innovative use of existing material, and graphite is a key material in the design of several of the next generation nuclear power plants. Currently there are two designs for the VHTR. The first design utilizes a prismatic core reactor. The second design is known as a pebble bed reactor. In the prismatic core reactor the nuclear fuel is contained in fuel rods. Hexagonal graphite blocks that hold the fuel rods are used to moderate the nuclear reaction. The cooling gas runs in channels inside the hexagonal prismatic blocks. The reactor is comprised of an array of blocks that accommodate fuel rods, control rods, and cooling channels. Alternatively, in pebble bed reactors the fissile material, the moderator, and a fission product barrier are contained in softball sized pebbles. The pebbles are continuously cycled through reactor channels and are removed from the bottom of the reactor. The pebbles are then tested to determine how much nuclear fuel remains. If sufficient fuel remains the pebble is returned to the reactor. Process cooling gas flows around the pebbles as they are cycled through the reactor.