Dr. Sören Kliem

Reactor Safety
Phone: +49 351 260 2318

Department of Reactor Safety


Neutron physics and reactor dynamics

  • Validation and application to light water reactors and innovative reactor concepts of the Monte Carlo code SERPENT2
  • Application of the deterministic lattice code HELIOS-2
  • Development, verification and application of the in-house reactor dynamics code DYN3D
  • Extension of the DYN3D code to innovative reactor concepts
  • Coupling of DYN3D to the system code ATHLET
  • Coupling of DYN3D to the Computational Fluid Dynamics codes ANSYS CFX and TRIO_U

Plant dynamics and severe accident analysis

  • Accident analysis and analysis of plant dynamics using the ATHLET system code
  • Assessment of the impact of severe accident management measures on the progression of severe accidents in PWRs and VVERs

Monte-Carlo simulations (n- / γ-field calculations)

  • Development of the in house Monte Carlo code TRAMO
  • Fluence calculations of the of the reactor pressure vessel and internals using MCNP and TRAMO

Latest Publication

Analysis of loss of flow without scram test in the FFTF reactor – Part II: System thermal hydraulics with point neutron kinetics

Ponomarev, A.; Nikitin, E.; Fridman, E.

This study presents a benchmark analysis of an unprotected loss of flow transient in a sodium-cooled fast reactor at the Fast Flux Test Facility (FFTF), carried out as part of an IAEA coordinated research project. Three codes, namely Serpent (Monte Carlo), DYN3D (3D nodal diffusion) and ATHLET (system thermal hydraulics), were employed in the benchmark exercise. Two distinct modeling approaches were utilized: 1) stand-alone ATHLET with point kinetics (PK) and system thermal hydraulics (TH); and 2) coupled DYN3D/ATHLET with spatial kinetics (SK) and system TH. Neutronics data essential for both approaches were generated using Serpent. The study is organized into three parts.

Part I presented a summary of the preparation of neutronics data for PK or coupled SK/TH simulations and included the outcomes of the static neutronics stage of the benchmark. The main focus lay on verifying the cross-section generation method for DYN3D by comparing its results against the reference Monte Carlo solutions obtained with Serpent.

Part II provides a detailed description of the ATHLET TH model of the system. This model is thoroughly evaluated by comparing the results with the ANL benchmark solution and experimental data for the transient. Furthermore, a sensitivity analysis is conducted to explore various modeling options and assess their impact on the simulation results.

Part III will showcase the transient calculation results using the two modeling approaches. Additionally, an adaptive decay heat model for nodal codes will be introduced. The performance of both modeling approaches will be assessed by comparing their results to the available experimental data.

Keywords: ATHLET; FFTF; Gas Expansion Module; loss of flow; point kinetics; SFR; unprotected transient

Related publications


Foto: Gruppenbild der Abteilung


NameBld./Office+49 351 260Email
Dr. Sören Kliem250/1082318


NameBld./Office+49 351 260Email
Dr. Silvio Baier250/1113034
Dr. Yurii Bilodid250/2092020
Dr. Emil Fridman250/2092167
Jörg Konheiser250/1092416
Kerstin Kurde250/1073025
Dr. Evgeny Nikitin250/2072906
Dr. Frank Schäfer250/1172069
Pratibha Yadav250/1102537