1 Laser-based Monitoring of UF6 cylinders IAEA-CN-184/213 S. Poirier, M. Moeslinger, C. Liguori, D. Langlands, M. Burmester Department of Safeguards, International Atomic Energy Agency, Vienna V. Sequeira, G. Bostroem Institute for the Protection and the Security of the Citizen, European Commission, Joint Research Centre, Ispra, Italy s.poirier@iaea.org Development efforts are in progress to enhance safeguards implementation at uranium enrichment facilities. One component of the enhanced approach is the systematic tracking of UF6 cylinders between process and storage areas as well as between different process areas. The main challenges are the means of tracking the cylinders reliably with a minimum of operator involvement, and finding the optimum location to install a monitoring system which is capable of recognising all types of cylinders as well detecting non-standard containers. The Laser Item Identification System (L2IS) has been developed successfully that is capable of monitoring all transfers of UF6 cylinders between process areas. L2IS uniquely identifies each cylinder through exploring the unique microstructure of each cylinder s surface. It has been demonstrated that every cylinder has a unique fingerprint which remains intact even under extreme environmental conditions. The L2IS system is composed of a portable unit, operated in attended mode, and a fixed installed unit, operated without inspector presence. The portable unit acquires the fingerprints of a given set of feed cylinders intended to be used over the coming months and the fixed system monitors the flow of previously identified cylinders in a transfer corridor. This system is coupled with standard video surveillance that can remotely transmit state of health information to IAEA Headquarters. The video surveillance can be interfaced with electronic seals applied to the cylinders to record and display seals data (e.g. status, time/date of application). The integration of data from the L2IS with data from weighing and NDA stations is planned to monitor and verify all transfers. This will provide a high deterrence of diversion or substitution, and an increased probability of detection thereof. The paper will describe the successful results of the L2IS after a year of field testing, the intended use of the L2IS during inspection, and the possible additional integration of other monitoring capabilities.
1. Introduction The IAEA closely monitors nuclear activities and material particularly when fuel cycle activities could yield material readily available for weaponization such as highly enriched uranium (HEU). Therefore, the application of robust safeguards measures at nuclear facilities enriching/depleting and processing uranium is of vital importance to the IAEA. The large size, complexity and increasing automation within the process areas of enrichment plants has resulted in intensive efforts to identify measures to enhance safeguards approaches. The IAEA is studying alternatives to optimize its use of inspection resources while at the same time maintaining credible safeguards implementation. The potential of an unattended approach to effectively safeguard quantities of depleted, natural and enriched uranium during the interim period between inventory takings has been considered as a consequence of affordable verification solutions to perform the monitoring of cascade areas not yet having been identified. Resources will be used more effectively and efficiently by verifying items at entrance and exit points, which minimizes the use of expensive instrumentation within process areas and reduces the possibility of failure or incomplete coverage. Clearly, a hands off approach is also favoured by the operator, as it provides for less intrusion into the process environment. This inspired the development of a novel instrument capable of identifying positively and monitoring items both entering and leaving the process areas of bulk handling facilities. 2. System Requirements Unique identification of items as part of a verification system is essential in providing real-time information on the location of such extremely sensitive and valuable material as UF6. To fulfil its safeguards purpose, the system must also handle the complete range of standardized transportable containers, including internationally transported UF6 cylinders (e.g. natural uranium (NU) feed in type 48Ys, NU heels in type 48Ys, or low enriched uranium (LEU) in type 30Bs) as well as national and facility-specific cylinders. Attempts to use non-standardized containers should also be detected and recorded. 2.1 Laser Item Identification System Configuration The verification of the unique identity by the L2IS is achieved by comparing reference items, which are recorded in a database, with the actual items. The system is therefore composed of two subsystems: A portable referencing unit (Unit 1) which acquires the fingerprint (reference scanning), and An installed (resident) verification unit to authenticate the fingerprint (verification scanning) of cylinders passing by (called Unit 2). The verification unit must be located in a well defined key position in order to monitor the cylinder movements.
Figure 1:: L2IS Unit 1 concept for fingerprint acquisition The system is coupled with standard surveillance to ensure that no cylinders or other containers could pass by unseen. The cylinders are transported from one side of the hall to the other side on rails the location of the system benefits from this unique transit path between the process and storage area. Both systems (surveillance and laser based scanner) are synchronized the data is reviewed in a unique review interface, and the latest General Advanced Review Software (GARS) is used to jointly review both video and cylinder identity data. No additional training is required for the data review. The L2IS project uses reliable, mainly standardized and commercially available, components and is implemented in a standard IAEA cabinet, offering to the inspectors IAEA standard data retrieval media and procedures, which minimizes the need for additional training, supplies and maintenance. Figure 2: L2IS unit 2 concept for unattended identification coupled with surveillance (SDIS)
2.2 Technical Description The function of the 3D-LSM is based on laser triangulation (illustrated in Figure 4 below). A sheet of light is projected onto the interrogated object using a laser diode and a cylindrical lens. Where this sheet of light intersects with the object surface, it creates a laser line which is viewed by a digital camera from a different angle. The camera is equipped with a bandpass filter adapted to the laser wavelength so as to minimize the influence of ambient light. The shape of the laser line seen by the camera depends upon the shape of the object. Assuming that the system is properly calibrated, each point of the laser line recorded by the camera yields the coordinates of one point in the laser plane. Each camera image therefore yields a profile which is the intersection between the laser plane and the object surface. By moving the object or the scanner in a controlled manner, a sequence of profiles can be acquired, producing a dense cloud of 3D points on the object surface. Figure 3: Triangulation principle (figure courtesy of Micro-Epsilon) 2.3 Project Testing and Technology Evaluation The first part of the evaluation of the technique aimed at selecting the range and model of laser scanner requirements for the foreseen operating conditions. This was achieved during a first field test, where a wide variety of static cylinders were scanned using laser scanners with different energy levels at BNFL Springfields. (December 2006). Once the system requirements and needs were established for the unit in charge of the reference acquisition, it was tested on a second set of cylinders in a different facility, under a support task from the French Support Programme. A test in Pierrelatte (AREVA) had two further objectives: Determining the requirements for scanning cylinders during transport (cylinders in motion), and Conducting an aging study of cylinders in order to determine if the standard cylinder process handling and maintenance cycle would affect the surface structure. The first scans were acquired in July 2007 and the second campaign took place in May 2008. The results of these tests identified the need for further development of the verification unit to be capable of scanning cylinders during transport. The speed factor is indeed a major influencing parameter but the occlusion/shadow created by the structure of the cylinder skirt and the bars on the trolley in regard to the triangulation scanning device was also a significant challenge to overcome. These were important points since the scanning system is not symmetric and the use of the system was intended to be able to scan a transported cylinder in both directions (from right to left and left to right).
In September 2007, the first trial L2IS system was installed under actual conditions, aiming to monitor a single cylinder (30B type) (one geometry) while being transported between areas in a facility (see Figure 2). Figure 4: L2IS unit 1 prototype ( EC/ JRC Ispra/ISPC) The system was used when the cylinder was in a static condition: The operator stopped the transport trolley for a few seconds in front of the verification scanner (UNIT 2 / Figure 2); The laser scanner was mounted on a rotation axe, performing a semi-circular swipe and permitting the laser beam to sweep across the cylinder surface. The acquired scan was then processed and compared with the reference database. The reference database was populated with scans obtained by use of the reference acquisition unit (UNIT 1 / see Figure 4), operated by an IAEA inspector. The Operator had to provide access, for reference acquisition, to all cylinders that were expected to be used over a material balance period. Figure 5: L2IS Unit 2 Version 2 as installed in March 2009
In 2009 an upgraded version of L2IS was installed on a trial basis and upgraded in March 2010 ( see Figure 5). This latest version of the system is operated in unattended mode. The system has been integrated with the SDIS surveillance system in a unique cabinet, aiming at providing a unique and standard servicing interface and procedure. To be able to identify the three types of cylinders existing in the facility in question, a wide scanning campaign was organized with the operator in March 2009 and 2010, which permitted the scanning of all 30B, 48Y and intermediate product cylinders intended for use in the coming months. The database of the installed L2IS Unit 2 Version 2 was then populated with this data and considered ready to verify all cylinders that would be presented as part of the theoretical Operator declaration. The second prototype of the L2IS Unit 2 was developed with the aim of achieving: a) A fully automated identification system (i.e. no intervention from the plant operator required), and b) The capability to identify the three type of cylinders used in the enrichment facility in question (different types imply different diameters and associated scanning configurations). Figure 6: L2IS Unit 2 Version 2 for Field Testing (March 2009) The upgraded system (L2IS Unit 2 Version 2- See Figure 6 & 7) is able to recognize automatically the type of the approaching cylinders and scan the surface using the appropriate scanner. Both recognition and scanning operations will take place while the cylinders are being transported on trolleys. The L2IS Unit 2 Version 2 system comprises three sub-systems: 1. The UF6 cylinder recognizer, capable of detecting the approach of a trolley, and recognizing the transported type of cylinders. 2. The trolley supervisor, to measure the speed of the trolley and monitor its movement, 3. The UF6 cylinder range data collector, featuring three line scanners responsible for the range data acquisition for each type of cylinder.
Items 1 and 2 are off the shelf components while item 3 comprise off the shelf components assembled and calibrated by the JRC Ispra/ IPSC. Figure 7: L2IS Unit 2 Version 2 for Scanning Three Cylinder Types 2.4 Future Expansion of L2IS Within the toolbox of technical measures applicable for safeguards implementation at enrichment facilities, the capabilities of the L2IS could potentially be further expanded to enable the characterization and quantification of nuclear material contained in the monitored cylinders. Such a combined, comprehensive system could employ laser identification, weighing, and determination of Uranium mass and enrichment while under surveillance. Furthermore an advanced L2IS system could act as a barrier on the transit route between process and external storage areas, being located at the entrance/exit point(s). A transfer trolley in the process area could be stopped and the cylinder lifted onto a modular scale/scanner/nda unit, before its onward transfer to the storage area. Additionally, all NU feed cylinders could be scanned in advance at point of origin (when filled at the UF6 manufacturers), as could the empty 30B containers (at the cylinder manufacturers). The data generated could then be transferred electronically to the IAEA, allowing for the automatic identification of the cylinders at any location where a laser tracking device had been installed.
3. Conclusion The challenge to uniquely identify the flow of various types of UF6 cylinders has been successfully addressed through the joint development and testing efforts of the IAEA and JRC. A new instrument has been developed, which is capable of uniquely identifying UF6 cylinders both entering and leaving the process and storage areas. Successful verification depends on the completeness of the reference database and the system reliability. The success of the trial described herein was heavily dependent from the cooperation and support of both the operator and the State system of accounting for and control of nuclear material (SSAC). The L2IS system is about to provide the IAEA safeguard inspectors with an automated system to uniquely identify (and thus monitor) the complete flow of UF6 cylinders in enrichment plants in an effective and efficient manner. The system is relatively non-intrusive and to a large extent automated. In its present form, L2IS presents a building block to the comprehensive application of safeguards measures to nuclear material bulk handling facilities and, in particular, to enrichment plants. Pursuant to the equipment toolbox approach towards providing suitable and adequate equipment for safeguarding enrichment facilities it is foreseen that the L2IS system will be complemented with additional systems capable of monitoring and quantifying the nuclear material contained within UF6 cylinders. As a key component of modern safeguards implementation at enrichment plants, L2IS is expected to reduce in-field IAEA inspection resources while at the same time maintaining credible safeguards implementation. L2IS lends itself readily to the concept of remote safeguards inspections, whereby safeguards data are acquired from the field without the physical presence of an inspector. [1] Laser Based Applications: Existing and Future Solutions. S. Poirier. JAEA-IAEA Workshop on Advanced Safeguards Technology for the Future Nuclear Fuel Cycle, 13 16 November 2007, Tokai, Japan. [2] A. Busboom, V. Sequeira, D. Langland, B. Wishard, S. Poirier: Laser Item Identification System Development for a Laser Based Identification of UF6 Cylinders, Proceedings of the 29th ESARDA Symposium. Aix en Provence, France, May, 2007. [3] S. Poirier, D. Langlands, M. Zendel, M. Moeslinger: Laser-based Monitoring of UF6 cylinders, Proc. 31st ESARDA Annual Meeting, 26-28 May, 2009, Vilnius, Lithuania. [4] Patent: Method for safely identifying moving objects