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Sub-critical Assembly Conversion


Analytical and experimental evaluating the possibility of creation of universal volume source of neutrons in the sub-critical booster assembly with low enrichment uranium fuel driven by a neutron generator

Tech Area / Field

  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors

8 Project completed

Registration date

Completion date

Senior Project Manager
Tocheny L V

Leading Institute
Joint Institute of Energy and Nuclear Research - Sosny, Belarus, Minsk, Sosny


  • Royal Institute of Technology, Sweden, Stockholm\nArgonne National Laboratory, USA, IL, Argonne\nForschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft/Institute fur Reaktorsicherheit, Germany, Eggenstein-Leopoldshafen\nMinisterio de Ciencia Y Tecnologia, Spain, Madrid

Project summary

The policy of minimization and elimination the use of highly enriched uranium (HEU) in commerce has been an important part of international non-proliferation activities for many years. Significant progress has been accomplished in converting research reactor fuel from HEU to low enriched uranium (LEU) fuel. About forty research reactors have been already converted to LEU fuel all over the world.

Belarus and U. S. experts will jointly work to evaluate the possibility of converting the high enriched fuel zones (36 and 90% enrichment) of Belarus subcritical assembly to use low enriched uranium (equal/less 21% enrichment) without penalizing its functionality.

The main objective of the Project is to study the possibility of converting the high-enriched fuel zones (90 and 36% enrichment) of booster (cascade) sub-critical assembly “YALINA-B” for use of low enriched uranium without penalizing its functionality. The second one is theoretical and experimental investigations of neutronics of accelerator driven systems (ADS) at sub-critical facility “YALINA-B”, at different sub-criticality levels, in wide range of core configurations and compositions of the assembly constituent elements (HEU and LEU nuclear fuel, structure materials, thermal neutrons absorbers, reflectors, shielding etc.).

The basic aspects of the accelerator driven systems with application of high energy proton beams for spallation neutrons production due to the interaction of high-energy particles with heavy nuclei targets (W, Pb, Bi, Th and U) are recently widely discussed in scientific publications all over the world. This approach is used for the development of Accelerator Driven Transmutation Technology (ADTT) proposed by Los-Alamos National Laboratory. Typical ADS consists of high-energy proton accelerator, neutron producing target and blanket (sub-critical assembly for neutron and energy production).

However, the experimental research in this field is rather scarce because the experiments with application of up-to-date high-energy accelerators (LAMPF, AGS, ISR, JINR…) are time consuming, difficult and expensive. The experiments with application of accelerators with high beam currents are planned only for the future. In this connection the ADS experiments with application of low energy accelerators, in particular, D-D - or D-T – mode neutron generators of high intensity may be of great importance. Such experiments can give valuable information about the transmutation reaction rates of minor actinides (MA) and long-lived fission products (LLFP) in different neutron spectra, the cross sections for different reactions, kinetics parameters of coupled systems etc.

The program of experimental research at the “YALINA-B” facility will cover the investigation of fast and thermal neutron fields behavior in different zones, kinetic parameters of the system, the effect of one-directional neutron coupling between the fast and thermal zones, spatial distribution of neutron flux density, time dependence of neutron flux density by different neutron pulse durations, transmutation reaction rates on minor actinides and long lived fission products nuclei etc.

Validation of the existing experimental methods and techniques will be performed along with its’ further development for the use in ADS experiments. The results will improve the ADS design capabilities and reduce its cost.

The computer simulation of the “YALINA-B” neutronics will be performed with application of Monte-Carlo method. Validation of computational methods and nuclear data libraries will be performed. Detailed analysis of the experimentally measured and calculated results as well as intercomparison will be performed.


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