Symposium on International Safeguards: Linking Strategy, Implementation and People Vienna – 20/24 October 2014 Developments in the deployment of Ultrasonic Bolt Seals at the storage ponds of a large reprocessing plant Y. Lahogue & F. Littmann Y. Lahogue, S. Synetos, J. Lupo, V. Piron – DG ENERGY-E (Euratom Safeguards) - Luxembourg F. Littmann, M. Sironi – DG JRC Institute for Transuranium Elements - Nuclear Security Unit - Italy DG ¡ ENER ¡
Content • Introduction (Yves Lahogue) - Safeguards requirements - Consideration of needs • Design of the new sealing system (Francois Littmann) - Ultrasonic seals - La Hague case study • Conclusion 2 DG ¡ ENER ¡
Safeguards requirements • Euratom Safeguards uses different techniques adapted to the Nuclear Material form and situation. All of them are designed to optimize the effort required to carry out verifications. • The number of items from various types requires significant inspection effort to verify the declared inventory within the required period of time. • Un-irradiated MOX fuels or residues are supposed to be verified more frequently. • Classic Cerenkov viewing devices (CVD) such as ICVD or DCVD are not usable to verify un-irradiated MOX material. Gamma/neutron measurement equipment is the alternative choice. Sealing is applied to keep the knowledge and avoid re-measurement. 3 DG ¡ ENER ¡
Safeguards requirements (cont.) • A simple and reliable solution is to prevent any movement of skips containing the NM by using a system that also participates to the locking of the lid, and makes the use of the lifting devices impossible. • The locking mechanism is then blocked by a so called Ultrasonic Bolt Seal that inspectors can verify by means of an underwater reading head connected to a computer. The seal cannot be removed without breaking its integrity. • The reading time is a lot shorter than the measurement time of all the items of a skip and therefore this equipment offers a considerable advantage for the safeguards activities. 4 DG ¡ ENER ¡
Consideration of needs • In 2012, DG ENER requested the assistance of JRC in reading old ultrasonic seals developed and manufactured by JRC more than 20 years ago and installed on several racks located in one of the underwater storage ponds of the La Hague reprocessing plant in France. • In the meantime, a contract was agreed, to supply a new generation of reading heads and related software based on today’s technology plus fifty more seals to cover the needs of the next years. • Significant new developments in this existing technique and the experience gained during the years of operations can now be presented. 5 DG ¡ ENER ¡
Why an ultrasonic seal? • An ultrasonic seal uniquely identifies a container. Special features inside the seal are scanned with an ultrasonic transducer. The pattern detected constitutes a unique signature for each seal. • Each seal includes an integrity. The removal of the seal results in breaking a metal link leaving trace of the opening or attempt of tampering. • IAEA-Euratom use them to seal nuclear underwater spent fuel containers. Can be an optimal solution for transport casks and to seal intermediate and final nuclear dry storage repositories. • Suitable for applications inside reactor and/or in aggressive environment, very robust, resistant to corrosion, pressure, heat and radiation. The fingerprint remains constant for years. 6 DG ¡ ENER ¡
How it works? 7 DG ¡ ENER ¡
Reading the seal 8 DG ¡ ENER ¡
Unbroken / Broken 9 DG ¡ ENER ¡
Sealing system in La Hague • Ultrasonic seals are in use in the underwater storage ponds of the reprocessing plant of Areva in La Hague (France) since 20 years. • Locking mechanisms, closed outside of the pond with an ultrasonic bolt seal and clamped underwater on the crane handles of the racks. • Beginning of 2012, the existing reading system stopped functioning. • DG ENER asked JRC assistance to solve the problem. 10 DG ¡ ENER ¡
The JRC Candu Sealing System • The JCSS is in use throughout the world since 2005 by IAEA & Euratom inspectors, more than 700 JCS seal installed. • Ultrasonic sealing principle is exactly the same, just the shape & dimensions of the seal are different. • The JCSS reading head has been tailored to read the La Hague seals. • The JCSS software has been adapted to read the La Hague seals (different direction and speed of rotation of the motor, different ultrasonic acquisition electronics). 11 DG ¡ ENER ¡
Reading Head • Mechanical design based on the reliable JCSS reading head. • Management of the eccentricity using a double cone shape of the end fitting. • Centering first on the external square shape and later on the conical head of the seal. 12 DG ¡ ENER ¡
On site Commissioning • After several in field missions to understand the problems and the needs of the customer, the final upgraded reading system was commissioned end of 2013. • All seals were correctly read and identified, the oldest were read before (found unbroken & identified), read again after removal (found broken & identified) and replaced with new seals. 13 DG ¡ ENER ¡
New seal design • Within the Administrative Agreement signed between DG ENER and JRC, it is planned to deliver new seals. • In the new seal design, the height will be smaller to integrate the seal in the square carter, external shape will still be compatible with existing interfaces (tools & reading head). 14 DG ¡ ENER ¡
New tools • Sealing operations were tedious because of the use of one single tool with several interchangeable end fittings dedicated to each operation, radio-protection control was required before any change. • A set of four tools was manufactured, dedicated to each end fitting, delivered last month, very positive feedback already received. 15 DG ¡ ENER ¡
Conclusion • The new sealing and reading equipment developed by the JRC and financed by Euratom Safeguards is now fully operational. • Inspection efficiency has gone up: • For such kind of fuel elements, the verification time could be reduced by factor of 10. • Other resources and dose uptake could consequently be reduced considerably. • Very positive results obtained by a close cooperation between the developers from JRC, the operational Euratom inspectors and the plant operators. 16 DG ¡ ENER ¡
Recommend
More recommend
