Methods and Codes for the Safety Analysis of Severe Accidents

Research goals

Improve the simulation capability of integral codes under development by cooperation partners (US NRC, IRSN) by extending the model capabilities to different reactor designs and validate the simulation capability by using key-data of KIT-experimental facilities. Perform analysis of severe accident scenarios of different reactor designs (PWR, BWR, and VVER) to show simulation’s capabilities and the ability to predict radiological source term. Hence, the extension and improvement of integral computer programmes (ASTEC, MELCOR) for the simulation of accident sequences with core degradation, among others, is a necessary precondition to determine the radiological source term and its propagation into the environment (e.g. using the KIT JRODOS code).


Validated severe accident codes are used for safety analysis of nuclear power plants in the frame e.g. of periodic safety assessments, for the development of optimized severe accident emergency management (SAM), to predict the radiological source terms to be provided to consequence analysis codes e.g. JRODOS. Current applications are embedded within the following projects: BMFB project WAME and H2020 MUSA Project.

Computational tools

  • ASTEC applications:
    • Validation of the early-phase of  PWR severe accident using the QUENCH-08 test data

  •  ASTEC Simulation of a MBLOCA Severe Accident Sequence in a PWR:

  •  The MELCOR: It is an integrated computer code for the analysis of the progression of severe accident sequences in Light Water Reactors.  It is under development by the Sandia National Laboratory for the US NRC. ( KIT access to MELCOR is through the CSARP (Cooperative Severe Research Program) of the US NRC.

 MELCOR Applications: Fukshima Unit 2 severe accident

 Validation of severe accident codes: The validation of integral codes is performed using experimental data focus in e.g. early (e.g. CORA, QUENCH, PHEBUS) and late in-vessel (e.g. LIVE, PHEBUS) phenomena, ex-vessel phenomena (e.g. MOCAK), containment phenomena or using the data from the few severe accidents e.g. TMI-2 or FUKUSIMA, which provide data for almost all phases of a severe accident.


  1. Gabrielli, F., Sánchez-Espinoza, V.H., 2018. Uncertainty and Sensitivity Analysis by means of ASTEC/URANIE Platform of the QUENCH-08 Experiment, Proc. Of the 24th Int. QUENCH Workshop, November 13-15, 2018, Karlsruhe, Germany, DOI: 10.5445/IR/1000088229.
  2. Gabrielli, F., Sánchez-Espinoza, V.H., Stuckert, J., Gómez-García-Toraño, I., 2019. VALIDATION OF THE ASTEC INTEGRAL CODE USING THE QUENCH-06 AND QUENCH-08 EXPERIMENTS, Proc. of the 9TH European Review Meeting on Severe Accident Research (ERMSAR2019), Clarion Congress Hotel, Prague, Czech Republic, March 18-20, 2019.
  3. Mercan, A., Sánchez-Espinoza, V. H., Gabrielli, F., 2019. Validation of ASTEC2.1 using QUENCH-12 for VVER-reactors, Proc. Of the 9TH European Review Meeting on Severe Accident Research (ERMSAR2019), Clarion Congress Hotel, Prague, Czech Republic, March 18-20, 2019.
  4. Wang, S.; Muscher, H.; Sanchez-Espinoza, V.H, 2019. Pre-Test Analysis of QUENCH-20 BWR-Bundle with ASTEC, Proc. Of the 25 International QUENCH Workshop, Karlsruhe, Germany, October, 22-24.
  5. Onur Murat, O., Sánchez-Espinoza, V. H., Wang, S., Stuckert, J., 2020. Preliminary Validation of ASTEC V2.2b with the QUENCH-20 BWR Bundle Experiment, to be published on Nuclear Engineering and Design.
  6. Stakhanova, A., Gabrielli, F., Sánchez-Espinoza, V.H., Hoefer, A., Pauli, E., 2020 Uncertainty and sensitivity analysis of the QUENCH-08 experiment using the FSTC tool, Proc of the Best Estimate Plus Uncertainty International Conference (BEPU 2020), Giardini Naxos, Sicily, Italy, October 11-17, 2020.
  7. Ignacio Gómez-García-Toraño, Víctor-Hugo Sánchez-Espinoza, Robert Stieglitz, Cesar Queral; Analysis of primary bleed and feed strategies for selected SBLOCA sequences in a German Konvoi PWR using ASTEC V2.0. Annals of Nuclear Energy. Annals of Nuclear Energy Volume 110 (2017) 818-832.
  8. Ignacio Gómez García-Toraño, Víctor Sánchez Espinoza, Robert Stieglitz; Investigation of SAM measures during selected MBLOCA sequences along with Station Blackout in a generic Konvoi PWR using ASTECV2.0. Annals of Nuclear Energy, Volume 105, July 2017, Pages 226-239
  9. Rafael Bocanegra, Valentino Di Marcello, Victor H. Sánchez-Espinoza, Gonzalo Jiménez; Fukushima Unit 2 Accident Simulation with MELCOR 2.1. Journal of Nuclear Engineering and Radiation Science. doi:10.1115/1.4038062 History: Received September 26, 2016; Revised September 12, 2017
  10. Ignacio Gómez García-Toraño*, Víctor Sánchez Espinoza, Robert Stieglitz, Juri Stuckert, Laurent Laborde, Sebastian Belon; Validation of ASTECV2.1 based on the QUENCH-08 experiment. Nuclear Engineering and Design Volume 314, 1 April 2017, Pages 29-43.
  11. Valentino Di Marcello · Uwe Imke · Victor Sanchez; Validation and application of the system code ATHLET-CD for BWR severe accident analyses. Nuclear Engineering and Design 307 (2016), 284-298.