New Ultrasonic Optical Sealing Bolts for Dry Storage Containers

Abstract

This paper presents a new seal for dry storage containers with nuclear material. Currently, sealing of dry storage casks containing spent fuel presents various challenges to safeguards inspectors. Continuity of knowledge needs to be reliably maintained over periods of time that can be decades. Seal replacements and verification , require significant Inspector efforts, radiological dose, and is continuing to grow. A decrease in Inspector effort is required and fail-safe redundancy is sought. These needs called for the development of a new compact sealing bolt covering these requirements. The Ultrasonic Optical Sealing Bolt (UOSB) is based on the JRC Candu Sealing System (JCSS), which is approved for safeguards use by IAEA and EURATOM safeguards. The new seal includes the same integrity element with the same identity element In addition, the UOSB integrates the additional element of a Fibre Optical Cable (FOC). This construction is in principal two seals-in-one allowing versatility. After several design iterations, field trials and a positive Vulnerability Assessment, the UOSB design was finalized. The first UOSBs, combined with EOSS and Cobra seals, were installed on dry storage containers at the Ignalina nuclear power plant (Lithuania) in June 2014. IAEA gave a Category A label to the UOSB system later on October 2014.