Use of electronic seals and remote data transmission to increase the efficiency of safeguards applied in a static Plutonium store

Transcription

1 Use of electronic seals and remote data transmission to increase the efficiency of safeguards applied in a static Plutonium store L. Persson 1, S. Synetos 1, A. Ozols 1, K. Ruuska 1, R. Leslie 2, H. Du Preez 2, C. Martinez 2, K. Payne 3, A. Polkey 3, M. Beaman 4, 1 European Commission, DG ENER, Directorate Nuclear Safeguards (EURATOM Safeguards), Luxembourg 2 Department of Safeguards, IAEA, Vienna 3 Sellafield Ltd, Cumbria, UK 4 Office for Nuclear Regulation, UK Abstract. The Pu timeliness goal of one month has been the deciding factor for determining the frequency of inspections at static Pu stores. The scope of these inspections mainly concerns the verification and replacement of seals and surveillance review. Using electronic seals together with remote data transmission (RDT) can significantly reduce the need for the physical presence of inspectors on site. For a static Pu store in Sellafield, jointly inspected by EURATOM Safeguards and the International Atomic Energy Agency (IAEA), special covers for the channel locks were developed and attached to the channel charge face. Electronic (EOSS) and Cobra group seals were applied that ensure minimal loss of knowledge in the event of any individual seal failures. At present, the EOSS seals are verified at the EURATOM headquarters in Luxembourg once a week with seal status data forwarded to the IAEA. Surveillance data can be used to investigate any potential issues with seals data. If an issue cannot be resolved by performing a video review, a physical inspection in situ will be necessary to perform verification activities as needed. The modified safeguards approach requires the operator to announce all planned visits to the store for maintenance and other planned work well in advance by sending an to a functional mailbox at the EURATOM HQ. This gives the inspectorates the possibility to participate when they are present on site for other activities or if they see a need otherwise. The use of RDT makes it possible for the inspectorates to replace monthly inspections with seal data checks, supplemented by periodic design information verification, at low frequency to ensure the continuing integrity of the system. The modified approach has increased the operational flexibility for the operator and initially reduced the inspection frequency by 50 %. 1. Introduction Plutonium produced at the Sellafield Magnox reprocessing plant is stored in dedicated product stores awaiting potential further use or to be placed in long term storage. EURATOM Safeguards has been safeguarding all civil nuclear material (NM) in the UK since it joined the European Union (EU) in 1973 and in 1990 one of the Magnox stores was designated for the application of safeguards by the International Atomic Energy Agency (IAEA) under the terms of the UK/Euratom/IAEA Voluntary Offer Agreement (INFCIRC/263). It has since been inspected jointly by EURATOM and the IAEA. The store reached its capacity a number of years ago at which time it turned into an essentially static store. The basic principle behind safeguarding NM stores, that is to verify all material upon receipt and place the material under appropriate Containment & Surveillance (C/S), remains. When NM has been placed under two independent C/S techniques and the C/S has been approved as dual, it is basically only necessary to review the C/S as long as the review is satisfactory. However, any discrepancies would result in additional assessment and verification activities. The deciding factors for how often the inspectorates must satisfy themselves that all material is accounted for are mainly the sensitivity and amount of the NM involved. Direct use material, such as Pu, has a timeliness factor of one month which means that all material must be accounted for on a monthly basis. The inspectorates have therefore sent inspectors to the site to perform monthly verification activities. 1

2 In order to optimize activities for the Sellafield Magnox store and to enhance cooperation between the IAEA and the EC, it was agreed to modify the C/S system and connect it to the network to make data available remotely to both inspectorates. This has led to considerable savings in personnel resources for the inspectorates and increased operational flexibility for the operator. 2. Safeguards approach The basic components of the safeguards approach remain unchanged and include the following: Annual verification of inventory based on the annual Physical Inventory Taking (PIT); Verification of Basic Technical Characteristics / Design Information to ensure that there are no changes to the facility which might affect safeguards; At the physical inventory verification (PIV) five randomly selected cans are item identified and verified for partial defects (weighing and neutron/gamma measurements); Application of appropriate C/S measures to maintain the Continuity of Knowledge (CoK) of the NM inventory; Evaluation of C/S data, locally or remotely, to maintain the CoK of the NM. To control access to corridors and the NM a FAST surveillance system with a QDIS installed as backup and as quality control are utilized together with Electro-Optical Seals (EOSS) on the channels containing NM and also the boundaries of the store. 3. Modified C/S Approach Up until recently all channels containing NM were sealed using Copper Brass Common (CBC) seals. In order to be able to draw safeguards conclusions, the approach required a monthly positive review of at least one of the components of the C/S systems which consisted of surveillance review or seal verification (replacement of seals) on channels at random low detection probability. The requirement for the PIV was a verification of seals at random medium detection probability. Due to the high number of seals involved (which equates to the total number of channels +3), an agreement was reached to perform the verification required for PIV over the material balance period e.g. do one twelfth per inspection. These seal verification activities and the requirement to restrict the valid attachment time for seals to three years resulted in verification of a high number of seals each month. In addition, safety and maintenance checks in order to fulfil the Site License Conditions oblige the operator to enter the store at regular intervals. This mode of verification therefore restricted the flexibility of operator access to the store of the operator, while at the same time it required a monthly presence by the two inspectorates. The monthly verification activities consisted of seal verification/replacement, video review and monthly accountancy updates as main components. The new approach relies on a modified multiple C/S system based on keeping the EOSS seals on the perimeters of the store, the existing FAST and QDIS surveillance systems together with one new component: Group sealing with EOSS and COBRA seals applied on channels for redundancy and arranged to reduce the common mode failure as well as lessen the number of channels accessible simultaneously (e.g. when access to one of the channels is needed) see Fig. 1. The surveillance data is recorded locally on both FAST and QDIS systems. The FAST data and all EOSS seals can be remotely accessed by the inspectors. It is also possible to access data from Luxembourg and transmit data further to the IAEA HQ. 2

3 FIG. 1. Drawing depicting the new group sealing arrangements using EOSS and Cobra seals In order to modify the sealing arrangements; specially designed anodised aluminium covers that are able to accommodate individual metal seals as well as group sealing by EOSS and COBRA seals were designed to fit over the shielding plug of each channel. The covers were designed to fit tightly and prevent access to channels and to expedite test fitting for security and usability the IAEA used 3D solid models and 3D rapid prototype printing. The seals are arranged according to one EOSS group seal for two horizontal rows of channels and one COBRA group seal for two vertical columns 1 of channels; see also Fig. 1. The sealing arrangement also reduces the number of seals needed and the subsequent need for seal verification. Installation of the covers, replacement of CBC seals with EOSS and COBRA group seals and the connection of the EOSS seals to the local network required quite some effort both from the operator and the inspectorates. But this investment has already started to pay off with the decrease in inspection frequency. 4. Data transmission EOSS seals data together with FAST surveillance data are transmitted to EURATOM headquarters in Luxembourg [1] and further on to IAEA headquarters in Vienna according to agreement between EURATOM, UK authorities and the IAEA. The cooperation of UK authorities has always been excellent and transmission of data has previously enabled RDT with subsequent savings in inspection resources at other UK installations for several years. The transmission of data takes place via a VPN for which agreed equipment is used. For images to be transmitted the security sensitivity (classification) of the field of view for the camera has to be approved by the operator. The following data recordings have been agreed for transfer to EURATOM headquarters in Luxembourg, either directly or by means of remote access to the on-site office: 1 In case there is a need to unseal one channel (e.g. at PIV to retrieve a can selected for NDA), implementing horizontal group-sealing for EOSS and vertical group-sealing for COBRA will allow to detach EOSS and COBRA seals corresponding to the concerned channel and still keep dual C/S system (EOSS + video surveillance or COBRA + video surveillance) on all channels but three at the most. 3

4 All EOSS seal interrogation data (perimeter and channels); Motion detection data of all cameras; Time-lapse recordings of selected cameras. It has also been agreed that the following data recordings received in Luxembourg are to be forwarded to the IAEA headquarters by EURATOM: All EOSS data; Motion and time-lapse recordings of selected cameras; In case of difficulties with both the above systems, arrangements will be made so that surveillance data for the remaining camera surveillance data are available via remote transmission on a case by case basis. Restrictions on the current bandwidth means that images from Sellafield will only be transmitted upon request in order to resolve issues arising from EOSS seals interrogations. As a temporary measure until data can be transmitted automatically, the EOSS seals data recordings are transferred to IAEA headquarters in Vienna once per week. 5. Requirements on the Operator The reduced presence of inspectors makes it necessary for the operator to adhere to agreed procedures concerning what the operator should do in case he becomes aware of alarms or anomalies such as for example issues with illumination/electrical power/equipment failures. All planned visits to the store for maintenance and other planned work are announced well in advance by sending an to a functional mailbox at the EURATOM headquarters. This makes it possible for the inspectorates to participate when they are present on site for other planned activities or if they see a need otherwise. Each access to the store is then recorded in a log book which is presented to the inspectors at the beginning of each inspection. confirmation of each access recorded in the log book is also provided to the functional mailbox. 6. Remote monitoring/rdt Every other month, when no on-site inspection is taking place, the two safeguards organisations will review signals from all EOSS seals that constitute the boundaries of the store and from the two selected cameras inside the store in their respective headquarters. Where these evaluations confirm the absence of entries in the store by the operator, no further action shall be required. Until data can be transmitted automatically from Luxembourg to Vienna, EURATOM inspectors will review the signals from all EOSS seals data recordings and also transfer the data to IAEA headquarters in Vienna once per week. 7. Inspection Activities Due to the store being static no changes to the accountancy are expected and the book inventory figures remain unchanged. The operator provides the dedicated logbook showing the details of the entries to the store since the previous inspection at the beginning of the inspection. Inspection activities to verify this information will normally consist of verifications of C/S and include the following activities: (1) Evaluation of the recordings of selected surveillance cameras (2) Evaluation of all EOSS constituting the boundaries of the store 4

5 (3) In case evaluations confirm that entry to the store only occurred in the presence of EURATOM inspectors, EURATOM will not perform any additional verification. If not present, the IAEA will receive EURATOM reporting as provided for at Article XXI of the protocol to INFCIRC/263 and be able to independently confirm the information through remote verifications of EOSS group seals on storage channels and through random verifications on the occasion of their next participation in an on-site inspection. (4) If evaluations confirm that entry to the store occurred in the absence of safeguards inspectors, EURATOM inspectors will extend their verifications to the recordings from the remaining cameras controlling the corridors between cells and to the evaluation of EOSS group seals on storage channels with a random low detection probability (20%). EURATOM will transmit Article XXI reporting to the IAEA. (5) Technical review of the other surveillance cameras (if not reviewed under (4) above). QDIS can be randomly reviewed for quality control or in case of FAST failure. In case of C/S failure, additional verification activities will be required. In a first instance the COBRA seals will be verified and if that result is satisfactory no further actions will be needed. Further actions will be needed to establish knowledge of material for which knowledge has been lost if also the verification of COBRA seals is unsatisfactory. At PIV inspections additional activities will be performed in addition to the routine activities. The EOSS group seals on channels or COBRA group seals will be verified with a random medium detection probability (50%), 5 cans randomly selected for NDA measurement for partial defect verification (neutron, gamma and mass), and the design information will be verified including review of C/S on containment. 8. Inspection Frequency With the modified approach EURATOM has initially reduced the frequency of on-site routine inspections from monthly to one inspection every two months, i.e. 5 to 6 routine inspections per year, plus 1 PIV inspection per year. The IAEA has the right to attend any inspection and will on average participate in one routine EURATOM scheduled inspection per year. The IAEA will also participate in all annual PIVs and perform at least one additional Design Information Verification (DIV) per year, in addition to the DIV performed during the PIV. This additional DIV to verify the integrity of the containment and containment systems will be performed during periods when EURATOM is present on the Sellafield site. The IAEA will inform EURATOM, Operator and State at least 72 hours in advance of its participation to a routine inspection or its plan to perform a DIV. 9. State of health data An automatic log file parser is in preparation and will be put into operation in the future. This will allow EURATOM to check state of health (SoH) alarm flags of installed safeguards equipment every working day. In case of alarms, EURATOM will then send a copy of the relevant SoH files to the IAEA and actions agreed upon. This will lead to immediate action in case a failure is discovered. 10. Conclusions The new arrangements rely on group sealing using EOSS and COBRA seals on store channels containing NM and EOSS seals on the perimeters of the store together with a FAST surveillance system using a QDIS as backup. All EOSS seals and the FAST system are remotely accessible from Luxembourg and transmitted further to the IAEA headquarters according to agreed procedures. 5

6 These modifications make it possible to remotely verify that the CoK of NM at a static store in Sellafield is maintained both from the EURATOM and IAEA headquarters. This has made considerable savings in manpower requirements possible and reduced the need for physical presence of inspectors to initially about half. Also for the operator considerable savings have been possible as they no longer have to plan resources in order for the store to be open every month solely for replacement of seals. Also the operational flexibility for the operator has increased as they can now plan safety checks and maintenance outside inspection weeks. REFERENCES [1] M. Beaman, P. Chare, P. Schwalbach, W. Stanley, J. Vigo, Scope for Remote Monitoring in Large Scale Plutonium Facilities, ESARDA, London,