Experimental Modeling of Accelerator - Blanket System
Experimental Study of Fast and Fast-Thermal Accelerator Driven Systems on the Basis of BFS-1 – Microtron Complex
Tech Area / Field
- FIR-EXP/Experiments/Fission Reactors
- FIR-REA/Reactor Concept/Fission Reactors
3 Approved without Funding
ITEF (ITEP), Russia, Moscow
- FEI (IPPE), Russia, Kaluga reg., Obninsk
- European Commission / Joint Research Center / Institute for Reference Materials and Measurements, Belgium, Geel\nAdvanced Energy Systems, Inc, USA, MA, Medford\nKorea Advanced Institute of Science and Technology, Korea, Taejon
Project summaryAccelerator-driven systems (ADS)– sub-critical systems with external sources have been widely discussed in recent years.
The ADS objective could be to treat the spent fuel or WG Pu, destroy the trans-uranics and selected fission products, and prepare the resulting reduced waste for permanent disposition in a geologic repository.
Recently the projects of ADS, based on different approaches, are being developed in a number of countries. ADS with fast neutrons blanket is being designed in the USA, molten lead – bismuth eutectic used as a target and coolant material (F. Venneri et al. “The Los Alamos Accelerator-Driven Transmutation of Nuclear Waste (ATW) Concept Development of the ATW Target/blanket System”. Proceedings of the Second International Conference on Accelerator-Driven Transmutation Technologies, 3-7 June, 1996, Kalmar, Sweden, Stockholm 1997, Vol. 2, p. 758). One of ADS concept in Japan is based on the current technology for sodium-cooled fast breeder reactors and with tungsten used as target material (T. Takizuka et al., “Conceptual Design Study of Accelerator-Driven Systems foe Nuclear Waste Transmutation”, Ibid., Vol. 1, p. 179.). Rubbia's project of ADS having fast neutron blanket with Th based solid fuel cooled by lead is being developed in Europe (C. Rubbia, “CERN-group conceptual design of a fast neutron operated power energy amplifier”. Accelerator driven systems: Energy Generation and Transmutation of Nuclear Waste. Status Report. IAEA-TECDOC-985, November 1997, p. 187).
Within the framework of the Russian-American commission on peaceful uses of weapons plutonium a general concept of ADS was developed in Russia (B.P. Kochurov, O.V. Shvedov, V.N. Konev, A.Yu. Kwaratzheli, “Accelerator Based Conversion Subcritical System with Fast and Thermal One-Directionally Coupled Blanket Regions for WG Pu Utilisation”, Proceedings of the of Second International Conference on Accelerator-Driven Transmutation Technologies, 3-7 June, 1996, Kalmar, Sweden, Vol. 2, Stockholm 1997, pp. 783-789. Chuvilo I.V., Shvedov O.V., Kochurov B.P. Et el., “Weapon Plutonium in Accelerator Driven Power System”. Ibid., Vol. 1, pp. 415-423.). Two blanket regions - internal with a fast spectrum of neutrons (F-blanket) and external - with a thermal spectrum of neutrons (T-blanket) provide a property of one-directional neutron coupling.
Stainless steel wall of F- blanket and inner wall of T-blanket serve as a fast neutron reflector for F- blanket and a structural component (together with an inner heavy water reflector), providing one-directional neutron coupling (See. for example, B.P. Kochurov, A. Yu. Kwaratzheli, V. N. Konev, “The Study of Molten-Salt Target/Blanket Systems with One-Directional Coupling”, Proceedings of the Second International Conference on Accelerator-Driven of Transmutation Technologies, 3-7 June, 1996, Kalmar, Sweden, Vol. 2, pp. 864-870, Stockholm 1997).
Due to the presence of fast multiplier part of blanket, the total system can be operated at a low level of sub-criticality (1-K) (multiplication factor K around 0.99) resulting in a low proton beam current at safety conditions corresponding to much higher sub-criticality of the main - thermal part of blanket (K around 0.95).
An experimental programme dedicated to neutronics behaviour of subcritical systems is underway at MASURCA experimental reactor in Cadarache to validate the physics of systems relevant to ADS (M. Salvatores et al.,”MUSE-1: A First Experiment at MASURCA to Validate the Physics of Sub-Critical Multiplying Systems Relevant to ADS”. Accelerator driven systems: Energy Generation and Transmutation of Nuclear Waste. Status Report. IAEA-TECDOC-985, November 1997, p. 430).
A large range of different configurations will be experimentally investigated under proposed project in the BFS installation, with the external source of neutrons produced by electronic accelerator (Microtron).
The work will provide valuable experimental data for a wide range of fast and fast-thermal critical and sub-critical systems with external neutron source and the comparisons against calculations.
ITEP team, participating in the project, have a good experience of work on the ISTC project # 17 (1994 -1996 years), that was dedicated to feasibility study of ADS in the use of weapons plutonium. This team will be engaged in the development of the concept of experiments, pre-computations on the determination of assemblies configurations and their parameters, in the analysis of experimental results. The nuclear data will be based on the ENDF-B/VI files. For the neutronics analysis of systems under study computer codes MCNP and TRIFON will be used (B.P. Kochurov, A.Yu. Kwaratskhely, A.P.Knyazev, “Methods and Computer Codes for Burn-up and Fast Transients Calculations in Sub-critical Systems with External Sources”, Proceedings of the International Workshop: Nuclear Methods for Transmutation of Nuclear Waste, Dubna, Russia, May 29-31, 1996, World Scientific Publishing Co., Singapore, 1997, pp. 100-109).
General theoretical approach, developed in ITEP, will be used for the analysis of systems with one-directional coupling: Seliverstov V.V. Analysis of Spallation Neutron Importance in Accelerator-Driven Target/Blanket Systems. Proceedings of the Second International Conference on Accelerator-Driven Transmutation Technologies, 3-7 June, 1996, Kalmar, Sweden, Vol. 2, pp. 891-897, Stockholm 1997.
The experiments will be performed by IPPE (Obninsk) team on the BFS installation with the external source of neutrons produced by Microtron. The IPPE team has a wide experience in the realisation of experimental programmes to validate the physics of fast critical systems and to confirm the projects of fast neutron reactors created in Russia.
The experimental approaches routinely used at BFS facilities with necessary modifications for sub-critical mode will be applied to the simulated ADS configurations.
The experiments will be carried out on the following configurations:
— Fast critical assembly with metallic uranium fuel and simulated sodium coolant.
— Fast sub-critical assembly with metallic uranium fuel and simulated sodium coolant.
— Fast critical assembly with plutonium + depleted uranium fuel and simulated lead coolant.
— Fast sub-critical assembly with plutonium + depleted uranium fuel and simulated lead coolant.
— Fast-thermal critical system.
— Fast-thermal sub-critical system.
The measured data will include: sub-criticality level, reaction rates axial and radial distributions, fission cross-section ratios, reactivity worth measurements, coolant voiding worthies for fast blanket.
Detailed experimental programs for each configuration will be defined at the period of working out of the system compositions according to the schedule.
Two criteria of one-directionally coupled fast-thermal system should be checked in the course of the study:
1) Weak dependence of neutron properties of fast blanket on the addition of surrounding layers (t. i. thermal part of blanket).
2) Low response of the total fission rate in thermal blanket to the perturbations of its properties, compared to the system without fast neutron multiplier that have the same or close level of sub-criticality.
Fast-thermal blanket coupling coefficients will be determined.
Preliminary evaluations has shown that a system of height 0.8-1.0 m and of diameter 1-1.5 m with fast part of blanket having a mass of heavy nuclides 0.7-1.0 t (enrichment 20-30%) and a thermal part of blanket having a mass of heavy nuclides about 2 t (enrichment 2-8%) can be used for simulation of 2-sectioned sub-critical systems driven by external sources. Fast and thermal parts of blanket are to be separated by absorbing and moderating layers.
The data can be used as benchmark results for validation of any computer codes systems. The property of one-directional coupling, if proven, will provide the basis for the design of ADS with low power accelerators at good safety conditions meeting the requirements to suppress the undesirable reactivity responses of the system. Thus the expenses for the accelerator part of designed ADS can be sufficiently decreased. ADS with fast and thermal parts of blanket can meet multi-purpose requirements of waste management, including utilisation of Pu, its conversion into 233U in Pu-Th fuel cycle, incineration of the main hazardous fission products (like 99Tc, 129I).
The data obtained in an outcome of project can be used at the next stage of ADS development - creation of a pilot AD installation with a current of the accelerator 1-5 мА and thermal power of blanket 50 - 100 MWt.
The project will provide weapons scientists and engineers the opportunities to redirect their skill to peaceful activities in the field of production of nuclear energy in installations with enhanced safety properties - AD systems operated in a sub-critical mode, with the main purpose to incinerate nuclear wastes, as well as surplus of accumulated nuclear materials. The “weapons” scientists’ effort in the project comes to about 80%.
The project contributes to the solution of national and international technical problems, providing a database in the field of integral experiments on the physics of systems relevant to ADS.
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