Development of Innovative Solutions for High Performance Impact Limiters on Transport Casks

In reference to IAEA safety recommendations, regulations demand that transportation casks resist to acceleration effects occurring in conditions of transports, without the reduction of the closure system efficiency. The integrity of the whole package must be maintained without giving rise to a significant release of radioactivity. One of the tests is 9m drop test of the package onto an unyielding surface. Impact limiters are a key safety component of the casksallowing to meet the integrity requirement. Their function is to absorb drop energy and limit the g-load, in order to ensure structural integrity.Up to now, the wood is the main shock absorber material, equipping the majority of heavy transportation or dual-purpose casks. AREVA TN with its more than 50 years of expertise in cask, design, license, manufacturing and operations has an extensive knowledge of this material. Data base on wood performance is quite significant as many industrials use this material. Wood presents a lot of advantages especially with its very high specific energy absorption, and considering its light weight.The industry is facing challenges to deal with the increasing constraints required by authorities and several solutions could be adequate alternatives without being influenced by environmental parameters such as humidity and temperature. To continue improve the safety performance and also economic performance of the casks, AREVA TN evaluated these different alternatives. Other efficient shock absorber materials are assessed and developed by AREVA TN. As an example, Honeycomb is an efficient technology quite well known in industry. This solution shows low dispersion with temperature when structural components are assembled by welding.Among other solutions, polymer foams show interesting mechanical features, with low dispersion at ambient temperature and influenced by moisture and temperature. Alveolar metallic solutions with high energy absorption capacity is also another alternative which can be “tailor-made” manufactured to integrate the regulatory requirements and the specific needs of our customers without being sensitive to environment effects. Research and development activities of AREVA TN on this critical component are focusing on the development ofefficient solutions for energy absorption.This paper will present a description of the evaluation and performance results performed to improve performance and provide efficient solutions to customers.