Performance of ceramic HTR fuel and coating materials under normal and transient conditions

During the last decade intensive development work for coated fuel particle was done. Reference particle systems for the Th/U and U/Pu cycle were designed and in the case of the high enriched variants qualification could be nearly finished. Testing under normal and transient conditions revealed performance limiting effects. Burnup and accumulated fluence of fast neutrons can exceed normal conditions by about fifty percent without causing detrimental failure. Temperatures up to 16000C were considered as transient. Failures caused by chemical interactions could be clearly detected but did not exceed requirements for licensing. (author)