[en] The measurements performed at the input of the reprocessing plant to determine the nuclear material flow into the process are complex in nature and require many techniques and instruments. The European Nuclear Energy Agency and the Joint Research Center-Ispra have begun to study the uncertainties affecting the measurement of input solution volume. The study includes experiments on a small-scale input accountancy tank, MITA (Mepis Input Tank Analysis), and analysis of the measurements and error propagation by the Monte Carlo Simulation Program for Reprocessing Input Tank (SPRIT). The SPRIT program has been developed for simulating the complete cycle of measurements performed by the operator at the input of the reprocessing plant to determine the nuclear material flow into the process. For a given plant, a given measurement procedure, and a given fuel solution, SPRIT calculates the volume of liquid and the amounts of uranium and plutonium in the solution, as perceived by the measurement system. The differences between these values and the actual values are attributable to the measurement errors, which are simulated by the use of appropriate stochastic functions associated with each error source. By repeating the calculation, a frequency distribution of the measurements can be built, form which the precision and accuracy of the measurement can be determined

[en] Hold-up of Special Nuclear Material in processing facilities is an insidious problem both for safety and safeguards point of view. Large inventory differences (IDs) are often proven to be caused by wrong estimates of hold-up, consequently, for a more efficient SNM accounting system, a new awareness about the problem of hold-up estimation has been created. In order to simulate the dynamic behaviour of mixer-settlers in an extraction solvent process, ENEA, in cooperation with the University of Rome, developed a Purex Extraction Process SImulation Code (PEPSICODE). PEPSICODE, due to a peculiar hydrodynamic modelling, describes time evolution of U, Pu and fission products concentrations both for transient and steady-state conditions. Simulation of an extraction campaign of EUREX plant will be reported

[en] The measurement of the Nuclear Material content in the spent fuels dissolution product is of a great importance both for the Safeguards Authorities and the Plant Management. This measurement is carried out in special vessels, currently called Input Accountability Vessels. In the present report the procedures applied and the instrumentation used both during the calibration and in the operational stages are described; moreover, the method and the statistical techniques currently used for the calibration data treatment and evaluation are reported and discussed. A critical analysis of all the possible sources of error in the Volume determination is also included. The goal of the present work, taking into account the Ritex experience results, was to demonstrate the needs of selecting the methodologies, the procedures and the instrumentation able to guarantee, besides a better precision, highly reliable Volume measurements for Accountability and Safeguards controls in the input section of a Reprocessing Plant

[en] Capacity building for staff of nuclear regulators is a key achievement to set up an effective nuclear infrastructure in countries operating or developing a nuclear program and also in countries without nuclear energy . Nuclear Regulatory Authorities (NRA) and their Technical Support Organization (TSO) need to develop a wide range of professional capacities including: legal-regulatory framework for nuclear and radiation safety; roles & responsibilities; safety objectives, principles and requirements; management of licensing process; technological aspects of nuclear facilities; analytical tools for independent assessment, regulatory inspection; physical protection; emergency preparedness; public communication. Training and tutoring (T&T) on these topics need to be specifically planned and implemented by professionals having senior experience as regulators and TSO. The training activity shall be carried out with the view and perspective of the regulatory role keeping in mind the regulatory functions and responsibilities and preserving their authority and credibility. The tutoring activity needs to be carried out at NRA or TSO headquarter with progressive involvement in concrete activity to effectively transfer approach and working methods. The above mentioned basic elements have been adopted and implemented while carrying out the activities of the ‘’INSC Project MC3.01/13: Training and Tutoring for experts of the NRAs and their TSOs for developing or strengthening their regulatory and technical capabilities ’’ financed by the European Commission (duration 01/ 2015 – 03/2019). The countries benefitting of this project are the Partner Countries (PCs) invited to T&T activity in EU and the Regional Countries (RCs) invited to the regional training courses (RTC). The PCs are currently 21. Fifty-two training courses (twenty-eight dedicated EU, sixteen dedicated regional, eight existing) on nuclear and radiation safety topics have been implemented since 2015. All of them (excluding the existing) specifically developed as ‘’dedicated ’’ courses, with participation of 722 trainees from NRA/TSO of 58 countries outside the EU (PCs and RCs). Eighteen tutoring courses for a total of 62 tutee-months tutoring activity have been carried out at NRAs/ TSOs headquarters in EU (Italy, Slovenia, Germany, Hungary, Bulgaria, Netherlands ) for 34 staff (tutees) coming from NRA of Armenia, Belarus, Brazil, Indonesia, Iran, Jordan, Malaysia, Mexico, Mongolia, Nigeria, Philippines, South Africa, Thailand, Vietnam, Ukraine. About 175 Contractor’s senior experts have contributed as trainers or tutors plus 28 local trainers involved in RTC. (author)

[en] Counting neutrons emitted by spontaneously fissioning plutonium isotopes is a means for determining Plutonium content in samples. Correlations techniques have been developed for separating such neutrons from a background of nonfission neutrons due to (α, n) reactions. Further procedures are then used to correct the effect of neutron-induced fission. In order to perform such a correction the sample's chemical composition (including the presence of moisture) must be a well known parameter. The present paper reports a theoretical formulation of a new approach (add-a-source technique), which could allow to correct the measurement indipendently by the knowledge of the sample's chemical composition

[en] A simulation model of PUREX process extraction phase for a contactors (mixer-settlers) battery has been developed. This model has been implemented in a FORTRAN code tailored both for mainframe and PC. The main goal of the code is to determine Uranium and Plutonium hold-ups vs.time within contactors in order to implement a NRTA project for a reprocessing plant. These results are extremely important for a complete analysis of NRTA system perfomance particularly to overcome the difficulty of executing physical inventory within liquid-liquid contactors of extraction lines. The chemical process simulation has been carried out conventional theoretical models with the exeption of hydrodynamic simulation which has been developed utilizing a model based on experimental results

[en] In the frame of the problems arising from the fissile materials safeguards into the facilities of the nuclear fuel cycle, the International Safeguards devoted, in the recent years, R and D efforts on a new Dynamic Accountability procedures (Near Real Time Material Accountancy) appealing to the needs of timeliness in detecting diversion. This paper deals with a feasibility study of a NRTMA system to be applied to a nuclear fuel fabbrication plant for light water reactor. Such a feasibility study was performed by developing a dynamic model and a computer program, written in FORTRAN 77, in order to simulate all the processes and measurement procedures involved in the nuclear material accountancy

[en] EC AidCo through the Instruments for Nuclear Safety Cooperation (INSC), since the beginning of 1990’s is cooperating with Regulators and TSOs of countries outside EU to strengthen their technical capacity for regulatory and licensing functions in the field of nuclear & radiation safety. A specific project has been defined and carried out in two years 2016-2017 in Armenia to enhance the capacity of the Nuclear Regulator (ANRA), and of its TSO (NRSC), to regulate and perform licensing review for improvements in RW management activity at the Armenian NPP. The project activity has been implemented by a consortium of EU organizations led by ITER-Consult providing technical support with the aim to: - assess the need to improve the safety of RWM onsite including log term storage; - identify and compare safety issue for alternative options; - discuss the technological and safety aspects linked with needed improvement measures; - develop and review regulatory requirements for pre-disposal and disposal RWM activities; - strengthen the ANRA and NRSC capacity in the evaluation of proposed upgrading measures for conditioning and storage of LILW accumulated onsite; - define regulatory requirements and conditions to be adopted also in view of future disposal; - transfer knowledge and provide training for regulatory safety review. The cooperation between the Contractor’s and the Armenian beneficiaries (ANRA and NRSC) has allowed the achievement of above objectives by working together, discussing issues, finalizing review work and providing training sessions. The capacity of ANRA and NRSC for incoming licensing have been improved in terms of knowledge of safety issues linked with RW management and the needs to have effective/complete and auditable safety analysis for review in the licensing process The activity has highlighted aspects of significant importance as related to the TSO challenges in supporting the regulator in the elaboration of regulatory requirements, in defining the conditions for safety analysis to be performed by the Licensee and in clarifying the completeness and auditability requirements of the safety analysis report (SAR) to be submitted for licensing purpose of RWM improvements at Armenian NPP. (author)

[en] Comments of the importance of accountancy operations for the safeguards of fissile materials precede the examination of some difficulties involved in the transfer of measurement methods from laboratory conditions to the operating framework. The need to identity as many as possible error sources affecting measurements of extreme importance for safeguards is pointed out. As an example of the whole question the case of input measurements of processing plants for uranium and plutonium determination is considered

[en] Nuclear Material Accountability, supported by Containment and Surveillance measures, is a foundamental means for an effective International Safeguard implemention in nuclear plants. Accountability is based on the verification that difference between a material quantity entering a given material balance and the quantity leaving that area in a given period of time, correspond and the amount of material actually present at the moment of the inspection. In the recent years International Safeguards appealing to the needs of timeliness in detecting diversion and concealing activities, devoted ReD efforts on a new Dynamic Accountability procedures (NRTMA) with particular concern with reprocessing plants. The present paper, which is the result of a research activity carried out in the frame of the Italian Support Programme to IAEA for Safeguards implementation, deals with a feasibility study of a NRTMA system to be applied to the EUREX pilot reprocessing plant. Such a feasibility study was performed by developing a computer program based on simulated plant generated data