IAEA activities and international collaborations

With a well-defined area of focused research and encouraging information exchange, the International Atomic Energy Agency (IAEA) conducts various coordinated research activities (CRA) and brings together various scientists from developing and developed countries. Within this established programme on CRAs, IAEA has been leading efforts on several Coordinated Research Projects on fast neutron systems. The presentation will briefly discuss and summarize various concluded, ongoing and planned CRPs, outlining their objectives and outcomes and showcase some key results. The CRPs are mainly in the field of modelling and simulations, covering neutronics, thermal hydraulics and multi-physics phenomena in fast reactors. Information on participating and contributing to such international collaboration projects, which aim to support not only wide R&D efforts but also various PhD studies in the universities, will also be provided

MONTE CARLO SIMULATION OF NEUTRONICS START-UP TESTS AT CHINA EXPERIMENTAL FAST REACTOR (CEFR)

China Experimental Fast Reactor (CEFR) is a small size sodium-cooled fast reactor (SFR) with a high neutron leakage core fueled by uranium oxide. The CEFR core with 20 MW(e) power reached its first criticality in July 2010, and several start-up tests were conducted from 2010 to 2011. The China Institute of Atomic Energy (CIAE) proposed to release some of the neutronics start-up test data for the IAEA benchmark within the scope of the IAEA’s coordinated research activities through the coordinated research project (CRP) on “Neutronics Benchmark of CEFR Start-Up Tests”, launched in 2018. This benchmark aims to perform validation and verification of the physical models and the neutronics simulation codes by comparing calculation results against collected experimental data. The six physics start-up tests considered for this CRP include evaluation of the criticality, control rod worth, void reactivity, temperature coefficient, swap reactivity, and foil irradiation. Twenty-nine participating research organizations are performing independent blind calculations during the first phase of the project. As a part of this coordinated research, IAEA performed neutronics calculations using Monte Carlo code SERPENT. Two kinds of 3D core models, homogenous and heterogeneous, were calculated using SERPENT, with ENDF/B-VII.0 continuous energy library. Preliminary results with a reasonably good estimation of criticality, as well as theoretically sound results of other five test cases, are available. The paper will discuss the core modelling assumptions, challenges and key findings of modelling a dense SFR core, preliminary results of the first phase of the CRP, heterogeneity impact analysis between homogenous core models and heterogeneous core models and future work to be performed as a part of this four-year project

MONTE CARLO SIMULATION OF NEUTRONICS START-UP TESTS AT CHINA EXPERIMENTAL FAST REACTOR (CEFR)

China Experimental Fast Reactor (CEFR) is a small size sodium-cooled fast reactor (SFR) with a high neutron leakage core fueled by uranium oxide. The CEFR core with 20 MW(e) power reached its first criticality in July 2010, and several start-up tests were conducted from 2010 to 2011. The China Institute of Atomic Energy (CIAE) proposed to release some of the neutronics start-up test data for the IAEA benchmark within the scope of the IAEA’s coordinated research activities through the coordinated research project (CRP) on “Neutronics Benchmark of CEFR Start-Up Tests”, launched in 2018. This benchmark aims to perform validation and verification of the physical models and the neutronics simulation codes by comparing calculation results against collected experimental data. The six physics start-up tests considered for this CRP include evaluation of the criticality, control rod worth, void reactivity, temperature coefficient, swap reactivity, and foil irradiation. Twenty-nine participating research organizations are performing independent blind calculations during the first phase of the project. As a part of this coordinated research, IAEA performed neutronics calculations using Monte Carlo code SERPENT. Two kinds of 3D core models, homogenous and heterogeneous, were calculated using SERPENT, with ENDF/B-VII.0 continuous energy library. Preliminary results with a reasonably good estimation of criticality, as well as theoretically sound results of other five test cases, are available. The paper will discuss the core modelling assumptions, challenges and key findings of modelling a dense SFR core, preliminary results of the first phase of the CRP, heterogeneity impact analysis between homogenous core models and heterogeneous core models and future work to be performed as a part of this four-year project

Neutronic Analysis of Start-Up Tests at China Experimental Fast Reactor

The China Experimental Fast Reactor (CEFR) is a small, sodium-cooled fast reactor with 20 MW(e) of power. Start-up tests of the CEFR were performed from 2010 to 2011. The China Institute of Atomic Energy made some of the neutronics start-up-test data available to the International Atomic Energy Agency (IAEA) as part of an international neutronics benchmarking exercise by distributing the experimental data to interested organizations from the member states of the IAEA. This benchmarking aims to validate and verify the physical models and neutronics simulation codes with the help of the recorded experimental data. The six start-up tests include evaluating criticality, control-rod worth, reactivity effects, and neutron spectral characteristics. As part of this coordinated research, the IAEA performed neutronics calculations using the Monte Carlo codes Serpent 2 and OpenMC, which can minimize modeling assumptions and produce reference solutions for code verification. Both codes model a three-dimensional heterogeneous core with an ENDF/B-VII.1 cross-section library. This study presents the calculation results with a well-estimated criticality and a reasonably good estimation of reactivities. The description and analysis of the core modeling assumptions, challenges in modeling a dense SFR core, results of the first phase of this project, and comparative analysis with measurements are presented

Verification and validation of neutronic codes using the start-up fuel load and criticality tests performed in the China Experimental Fast Reactor

Under the framework of coordinated research activities of the International Atomic Energy Agency (IAEA), the China Institute of Atomic Energy (CIAE) proposed a coordinated research project (CRP) to develop a benchmark based on the start-up tests of the China Experimental Fast Reactor (CEFR). 29 international organizations from 17 countries are participating in this CRP. Among the different physical start-up tests conducted in 2010 in the CEFR, the fuel loading and criticality experimental data is included. Before the start-up of the reactor, the core was preliminarily loaded with mock-up fuel sub-assemblies (SAs) in the active fuel positions. The reactor reached first criticality by replacing these mock-up SAs with real fuel SAs step by step. In a sub-critical extrapolation process, the number of fuel SAs to be loaded is determined by extrapolation of reciprocal of count rate and following safety requirements. As the reactor core approaches to criticality, the subcritical extrapolation ended and the next process is called super-critical extrapolation, which uses the control rods to reach criticality by period method. For the CEFR, the final clean-core criticality state was reached with 72 fuel SAs and the regulating control rod at the position of 70mm with a measured sodium temperature of 245°C. In the paper, the main results of the contributing international organizations for the fuel loading process in the blind and refined phase are summarized and compared with the experimental data. Additionally, code to code comparisons for normalized radial power are also presented. In general, results from all institutions show very good agreement while comparing with the experimental data. The results are divided in deterministic and stochastic codes and in each case, discussion and deep analysis is presented