Advanced Reusable Mandrel for Ceramic Cladding Fabrication

The use of advanced ceramic materials, such as silicon carbide, for light water reactor fuel cladding is being investigated, in part due to the increased safety margin afforded by this technology over conventional zircaloy metallic claddings. In light of the Fukushima events, safety concerns have come to the forefront of public scrutiny of commercial nuclear generated power and spurred activity in this arena. While the safety benefits of advanced ceramics are attractive in their own right, there are other desirable characteristics that further increase the attractiveness of these materials, including the maintenance of strength and neutron (and thus power generation) efficiency which have their own benevolent cascades. A deterrent, however, is the current cost of production of these materials. In the research quantities these materials are currently produced, they are an order of magnitude higher than the rival metallics on a per-foot basis. As the industry moves towards manufacturing for commercial use, economy of scale alone cannot be expected to narrow this cost differential. Decreasing the cost of production and establishing a uniform process that produces material of consistent quality will make advanced ceramics a more cost-competitive technology for fuel cladding. Each incremental step that addresses a large-scale manufacturing challenge increases the chances that advanced ceramic claddings can be introduced to the market as a viable replacement for conventional metallic clads for nuclear fuels in light water reactors. The reusable mandrel proposed in this project is an enabling technology for the fabrication of a full length 14-foot tube ceramic tube, which has to-date not been demonstrated. That this innovative mandrel can also decrease the costs of production over current methods is a further motivation for the pursuit of this technology. In Phase I, a number of candidate reusable mandrels will be fabricated which will be subsequently used to produce silicon carbide tubing. The method to remove these mandrels from the inner diameter of the tubing formed around them will be demonstrated. Survivability of the mandrel throughout the process, and afterwards, will be demonstrated, highlighting the capability of re-use of these mandrels. Commercial Applications and Other Benefits: If successful in Phase I, a Phase II program will be proposed to demonstrate the fabrication of mandrels capable of producing 14-foot lengths of tubing, a major milestone for the production of advanced ceramic cladding. The technology of this product is not limited to any of the specific designs currently proposed, and is thus applicable for use with any of the expected ceramic fuel clad manufacturers. The current market for cladding is over 150,000 linear feet annually for each light water nuclear reactor, with a fleet of over 450 reactors worldwide. This reusable technology reduces the cost of production, and as such, alone, could be worth a minimum of a $750,000 in cost reduction in the price of fuel assemblies, annually, for each reactor that adopts ceramics for their safety benefits. Over the entire fleet, this is a considerable savings of over $33 million annually.