ACCOUNTING OF NUCLEAR MATERIAL AT PROLIFERATION SENSITIVE POINTS

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1 Tripartite seminar, Obninsk 2006 ACCOUNTING OF NUCLEAR MATERIAL AT PROLIFERATION SENSITIVE POINTS IN THE KAZAKHSTAN FUEL CYCLE G. Janssens-Maenhout, J. Delbeke, M. Caviglia, W. Janssens Joint Research Centre Ispra, IPSC - NUSAF Via E. Fermi, 1, TP. 421, I ISPRA (Italy) greet.maenhout@jrc.it ABSTRACT Since 1995 with the ratification and enforcement of the Non Proliferation Treaty in the Republic of Kazakhstan, the Kazakhstan Atomic Energy Committee (KAEC) is responsible for the implementation of the State System for Accountancy and Control (SSAC). In the SSAC, data on nuclear material inventories are periodically collected on individual nuclear facilities and stored into the KAEC data base, from which reports are prepared for the IAEA in accordance with the Safeguards Agreement between IAEA and Kazakhstan. Corresponding to the Agreement on Nuclear Safety between Euratom and Kazakhstan a programme on Nuclear Safeguards under TACIS (Technical Assistance for the Commonwealth of Independent States) was launched that should enhance the effectiveness of the present state system. After evaluating the different nuclear facilities in Kazakhstan with KAEC, the following facilities have been identified with a need for enhancing safeguards in methodology and instrumentation: - the Ulba Fuel Fabrication Plant in Ust-Kamenogorsk - the research reactors of the Nuclear National Center at the Alatau and Baikal-1 sites. Mainly, in the first facility, the Ulba plant, a scanning system for accurate, near-real time monitoring of the level and density in multiple tanks have been provided for an enhanced followup of the process and in particular the nuclear material flow. The automatic fusion of the data with analysis and interpretation is addressed in a future subsequent project for near real time accountancy at Ulba. Additionally, at the identified facilities a review camera station enhanced the surveillance and complemented the physical protection of the research reactors. Finally, the TACIS programme provided the beneficiary KAEC via the Nuclear Technology Safety Center with informatics equipment and data architecture for modernising the data collection and analysis of the nuclear material accountancy and control. Moreover with the expanding Kazak nuclear activities in particular the new nuclear power plant under design and construction, and the increasing tasks of KAEC also in the safety field, an automatic system for the analysis can help substantially KAEC in its reporting to IAEA under its future Additional Protocol agreement on all nuclear material and its transfers. 1. INTRODUCTION After the break-up of the Soviet Union in 1991, 4 newly independent states faced a situation with nuclear material and sites used in the military fuel cycle and for which a transformation in a civil nuclear fuel cycle and safeguards control measures were needed. The safety and security of the Commonwealth of Independent States (CIS) were discussed at the G7 Summit (Munich, 1992). The EU received leadership to assist the CIS in implementing international safety and safeguards standards and culture. Kazakhstan signed in 1994 the non proliferation treaty and had a safeguards agreement in place end In this period, the EC adopted a programme for technical assistance to the CIS (TACIS) in which also safeguards was addressed. The Kazakhstan atomic energy committee (KAEC), constituted in 1994 as a nuclear state authority, was also in charge of the follow-up of the safeguards agreement. So, KAEC was the interlocutor for the TACIS programme in Kazakhstan. The Joint Research Center, known as an EC organism that has substantial experience 1/8

2 in delivering to the Euratom inspectorate the necessary support on research and development in nuclear safeguards, was appointed to take care of all safeguards projects. JRC Ispra took the initiative of a fact finding mission to meet KAEC in Almaty and Kazatomprom in Ust Kamenogork to discuss a project with the Ulba fuel fabrication plant. A final report on this first project is given under [1]. This was followed by a project, documented under [2] with a broader scope addressing more nuclear facilities with safeguards relevance in Kazakhstan: 1. the Mangyshalk Fast Breeder in Aktau that is since 1998 under decommissioning 2. The research reactors at the Baikal-1 and Alatau sites, operated by NNC. 3. The Ulba fuel fabrication plant in Ust-Kamenogorsk converting UF6 via solutions in UO 2 After on-site evaluation it was decided, in agreement with KAEC, to minimalise the effort on the Mangyshalk reactor, to provide mainly review stations for surveillance at the reactors and to focus on the Ulba Fuel Fabrication Plant with solution monitoring. This was complementary to the large support, mainly on physical protection for the Mangyshalk reactor by the US, as documented under [3]. In line with the TACIS objective to transfer the Euratom safeguards methodology to CIS, the projects gave direct support to KAEC with an automated data analysis system for reporting on the nuclear material accountancy and control to the IAEA, and indirect support by equipping the research reactor sites and the Ulba plant. Besides the containment/surveillance equipment, major focus was on providing a solution monitoring system, for which level/density measurement stations and calibration devices were delivered. 2. RELEVANCE OF NUCLEAR MATERIAL MONITORING IN KAZAKHSTAN Kazakhstan has to report to the IAEA all transfers of source material and special fissionable material with the technical specifications as required by the Safeguards Agreement INFCIRC/254. This allows the IAEA to verify the compliance of the Kazakhstan s declared nuclear facilities with the three safeguards goals. In addition Kazakhstan signed in 1994 the Additional Protocol, which will request additional safeguards measures, in particular reporting on non-declared nuclear facilities, when it enters into force via the extended safeguards agreements. Anatonov et al. (1997) reports on one of the first Physical Inventory Taking and Verification exercise for U in the Ulba plant [4]. Physical inventory taking and verification Interim verification/ evaluation of declared operations (NMAC) Survey of functional status NM flow check on conformity & completeness NM flow follow-up with coherency check Near Real-time accountancy (NRTA) of the NM all KMP s in all MBA s SSAC Fig. 1: Sketch of the ingredients of the State System for Accountancy and Control

3 A State System for Accountancy and Control is defined and under control of KAEC. As sketched in Fig. 1, this ideally includes a two-fold job, accurate inventory taking and verification at regular periods and near real time follow-up of inventory transfers. Mainly the latter requires acquisition of inventory measurements with a data rate between 1/second to 1/minute. 3. CASE 1: ULBA FUEL FABRICATION PLANT: CONCEPT OF SOLUTION MONITORING To enhance and modernise the Nuclear Material Accountancy and Control (NMAC) at the Ulba Fuel Fabrication Plant, the concept of Near Real Time Accountancy (NRTA) is applied. A defence in depth concept is proposed with the superposition of the following barriers: 1. continuous survey of the functional status, 2. the follow-up of the nuclear material (NM) flow and inventory, 3. Near real time control of declared NM in processed solutions, 4. Periodical Physical Inventory Takings and Verifications. The combination of measurement stations scanning the level and density of the tanks with minimum frequency (0.2 Hz) and an informatics system with appropriate software for automatic data analysis and interpretation enable to follow in near real-time the NM flow and inventory through the plant MASS/VOLUME MEASUREMENTS OF THE TANKS Most of the tanks of the Ulba plant have been equipped with three dip tubes and a PT100. Fixed measurement stations, shown in Fig. 2a and b, are scanning alternating on 15 subsequent tanks the pressure differences for measuring the level and an averaged density accurately. The pressure transducers have a precision of 0.01% FS. An uncertainty lower than 0.1% (1S relative) is routinely achievable under the following conditions: if correction factors for thermal expansion of the tanks and for friction of the gas flow are applied to compensate the systematic errors [5] and if humid clean air is supplied at a constant flow rate (typically from 5 to 30 Nl/h) through the bubbling dip tubes of same size (6mm internal diameter). Fig 2a: Fixed Measurement stations for scanning level and density measurements of 15 tanks: front and rear panel

4 Fig.2b: fixed Measurement station: ingredients and connection To guarantee a conversion from level to total volume and to total mass, accurate tank-specific calibration curves have to be established with careful, gravimetric calibration applying the same equipment and conditions as used during real operation. The IAEA s approach is to setup calibration relationships for all subsequent regions of interest and to verify the calibration curve of accountancy tanks annually. The final uncertainty on the total mass amounts typically up to 1% COLLECTING AND ARCHIVING WITH A DATA HISTORIAN Taking into account the experience over many years at the La Hague Reprocessing Plant it is recommended to apply a real-time database for displaying the time series at any interval with high performance. In order to optimally analyse large amount of time-stamped data, the collected data are compressed by the data historian. For the Ulba plant application it is possible to envisage a commercial data historian 1. Both support the standard OPC (Object Link Embedded for Process Control) HDA (Historian Data Access) and allow a connection with a wide variety of OPC servers and a data supply to OPC clients. The compression methods (e.g. swinging door for signals with constant slope and death band for constant signals) have to be optimally parametrised in order to minimise the influence of the data compression on the final NM flow monitoring [6]. The reported data of the historian with their time and date allocation are converted into the required quantities (density and temperature, tank level, volume transfer) taking into account the standard units, the chemical relationships and the calibration curves. The results of these conversions are stored in the real-time database NEAR-REAL TIME MONITORING WITH DATA ANALYSIS AND INTERPRETATION Solution monitoring includes two activities: firstly, a continuous survey of the health status of the instrumentation and process conditions and, secondly, a comprehensive real-time interpretation of the dynamic process functions. These activities constitute the first two barriers of the defence-indepth concept. As represented with the two columns in Fig. 3, the first activity is typically associated with the safety monitoring of the plant, whereas the second, requiring a thorough understanding of the plants normal functioning and potential diversion paths, brings high value to nuclear safeguards. 1 Either the Matrikon data historian or the Wizcon data historian or the industrial PI system can be selected.

5 Fig. 3: Solution monitoring: two activities A particular aspect of the process control, namely the follow-up of cyclic processes, can be performed by using the DAI kernel developed by JRC for automatic Data Analysis and Interpretation of vast amounts acquired batch data. The specific features of the DAI kernel consist in the analysis by autocorrelation of the signals to check the completeness and by crosscorrelation between different simultaneous signals to check the comprehensiveness [7]. The latter covers also the coherency of the process signals with the safeguards purposes. User starts applications by double-click Application specific Application specific Generic: Data Historian - DAI - Results DB Fig. 4: Solution Monitoring system with CSV file reader, data historian and DAI kernel

6 The DAI concept with a generic syntactic pattern recognition analysis kernel and plant-specific design parameters allows to apply the software to different plants. The plant-specific application is built with two additional modules. First, the acquired measurement data are supplied to the data historian via a JRC module: the CSV (Column Separated Value) reader. Secondly, the plantspecific calculations, such as the conversion of level into volume via the tank calibration curves, are performed in the Calculation Engine, another JRC module that stores the data in the results access database. The monitoring tool with DAI was validated in a major European reprocessing plant, UP2 and UP3 at the site of La Hague as inspection tool, and it was also applied for solution monitoring at the TETRA facility of the Japanese inspectorate NMCC and for the NM flow monitoring at the Tokai Reprocessing plant by the IAEA [8]. The JRC data analysis and interpretation kernel DAI integrated with a commercial data historian is proposed to establish Ulba s plant-specific NM monitoring software tool, which is presented in Fig. 4. The data analysis focuses on a combination of the pressure signals (for level and density) and the temperature signal, determining the total volume and the total mass. For near real-time accountancy of the nuclear material that is flowing in batch mode through the Ulba fuel fabrication plant the solution monitoring tool establishes automatic data collection, analysis and interpretation. It allows to audit the batch process and represents graphically the inventory transfers while indicating the important transfer events in the tank cycle [9]. Each anomaly, either an interrupted tank transfer or a shipper-receiver difference for the transfer between two communicating tanks, is identified by the software and highlighted with an alarm for further investigation by the user. 4. CASE 2: RESEARCH REACTORS AT ALATAU AND BAIKAL-1 Reactors are in general safeguarded by counting and identifying individual fuel assemblies. In the contrary to nuclear power reactors, the fuel of a research reactor is not composed of standard fuel assemblies and is not sealed with e.g. an ultrasonic bolt. Moreover research reactors of open pool type are not even confined in a sealed reactor vessel. Therefore it is of high relevance for the IAEA to have surveillance for guarding against undeclared removal and to monitor the irradiation histories to prevent from undeclared breeding of nuclear material. The Institute for Nuclear Physics of the National Nuclear Center (NNC) were provided with additional set of containment surveillance equipment, containing camera with acquisition stations and accessories, run by a JRC software. The objective was to equip the research reactors at Alatau and at the Baikal-1 site with the necessary containment/surveillance instruments. In addition a Monte Carlo software and a burn-up calculation code were provided to the Institute for Atomic Energy of the NNC, so that IAE can simulate the reactor core evolution and estimate the burnup and isotopic composition of the irradiated fuel. The codes have been tested and are successfully run as demonstrated under [10]. 5. CENTRALISATION AND SUSTAINABILITY OF THE NMAC AND NRTA DATA 5.1. DATA COLLECTION AND ANALYSIS AT KAEC The Republic of Kazakhstan does not have a complete, independent nuclear fuel cycle, but it has several nuclear activities such as mining, conversion and fuel fabrication, it runs some reactors, three research reactors, and plans to construct a new power reactor. It inherited a fast breeder that is decommissioned and some nuclear test sites that need further decontamination. The KAEC is responsible for radiation protection, nuclear safety and nuclear safeguards with supervision of all nuclear activities, licensing and inspections. To facilitate their large job as nuclear authority KAEC welcomes all support, such as from the Nuclear Safety Technology Centre (NSTC) as well as each automation of data collection and analysis. This support is in particular needed for the increasing reporting on nuclear material, activities and technologies to meet international standard measures and for complying with the

7 foreseen additional requirements under the Additional Protocol. In collaboration with the Swedish Support Programme and the European Commission, informatics equipment and software for automatic data collection and analysis were provided to KAEC via NSTC. 5.2 SUSTAINABILITY OF THE NMAC AND NRTA ENHANCEMENT The continued correct use of the safeguards instrumentation is only guaranteed if the operators are trained. Instrument-specific training was provided for the surveillance stations and for the mass/volume instrumentation. For the latter also a tank calibration training room was installed at Ulba, which was inaugurated in October CONCLUSION KAEC faces with Kazak s growing nuclear activities increasing responsibilities in safety and safeguards. The Ulba fuel fabrication plant is amongst the most vulnerable facility from proliferation point of view because in this facility the nuclear material (mainly U) is directly accessible in gas, liquid or powder form. Even though traditional nuclear material Accountancy and Control with periodical inventory difference verifications are performed, the near real time accountancy helps directly in identifying timely and locally problems with nuclear material flows. Solution and process monitoring is the key for a higher automation in process control with enhanced safety and safeguards because it automatically follows the process conditions and the nuclear material flow and inventory. It therefore contributes to the process quality and enhances the accountancy accuracy. REFERENCES 1. Janssens-Maenhout, G., Hunt, B., Landat, D., Caviglia, M., An EC Republic of Kazakhstan TACIS project K : Establishment of Facilities for Mass/Volume, Containment/Surveillance and Training at the Ulba Fuel Fabrication Plant in the Republic of Kazakhstan: Final Report, EUR-Report EN 2. Janssens-Maenhout, G., Dechamp, L., Dzbikowicz, Z., (2006) An EC Republic of Kazakhstan TACIS Project K : Towards an Enhancement of Safeguards at the ULBA Fuel Fabrication Plant, the Mangyshalk Fast Breeder Reactor, the Almaty VVR and the Kurchatov reactors in Kazakhsta : Final Report, foreseen for publication as EUR-Report 3. Restricted IPSC Technical Note (2006), Nuclear Profile of The Republic of Kazakhstan 4. Antonov, N.A., Saifutdinov, S. Yu., Sprinkle, J. K. and Bahram, M. A., (1997), Organisation of MC&A at UMZ Facility. Results of Initial Inventory Taking of Uranium, Proc. Tripartite Seminar on Nuclear Material Accounting and Control at Fuel Fabrication Plant, April 1997, Obninsk 5. Janssens-Maenhout, G., Dechamp, L., Grassi, P., (2004) Monitoring of the interface movement of a bubbling dip tube by the pressure signal, Proc. CHISA Congress, Prague 6. Miller, E. C. and Howell, J. (1999), Tank Measurement Data Compression for Solution Monitoring, Journal of Nucl. Mat. Management, Vol. 37, No. 3, pp Janssens-Maenhout, G., Dechamp, L. (2004), Process Monitoring Appropriate for Near-Real- Time-Accountancy, Journal of Nucl. Mat. Management, Vol. 32, No. 3, p

8 8. Janssens-Maenhout, G., Dechamp, L., Zdzislaw, Z., (2006) Advanced Solution Monitoring: Real-Time Analysis, Proc. CHISA Congress, Prague 9. Janssens-Maenhout, G., Dechamp, L., Thevenon, J.B., Dransart, P. (2004) Auditing of Batch Processes, Proc. CHISA Congress, Prague 10. Polomoshnova, L.V., (2006), Automated Accounting and Control System of Nuclear Materials AACS, scientific report of ASE IAE, awarded with the third price under the 6 th Conference-Competition of Young Scientists and Specialists in Kurchatov