1. VICTOR HUGO SANCHEZ ESPINOZA and I. GÓMEZ-GARCÍA-TORAÑO
IAEA Conference on Topical Issues in Nuclear Installation Safety: Safety Demonstration of Advanced Water Cooled Nuclear Power Plants, 6-9. June 2017
IAEA-CN-251
Analysis of PWR Severe Accident Sequences including Mitigative Measures to Prevent or Delay the Failure of Safety Barriers with the Severe Accident Code ASTEC
VICTOR HUGO SANCHEZ ESPINOZA and I. GÓMEZ-GARCÍA-TORAÑO

2. Content Motivation The European SA Reference Code ASTEC
Selected Severe Accident sequences (with/without SAM)
Conclusions and Outlook
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

3. Motivation Fukushima accidents showed necessity for review
Re-evaluation of accident analysis methodologies
Assessment of NPP safety status
Review of SAMG
Improvement of numerical simulation tools used for SAM e.g. ASTEC, MELCOR, etc.
German activities in SA embedded in national (WASA-BOSS) and international projects (CESAM, FASNET, etc.)
KIT participation of SAM-optimization for BWR within WASA-BOSS project
KIT participation n SAM-optimization for PWR within EU CESAM project
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

4. The ASTEC Severe Accident Code
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

5. The European SA Reference Code ASTEC
CPA
Main Modules ICARE, CESAR, and CPA used in the PWR plant simulations
ICARE
CESAR
Aim of code
Explain the picture
Modules that are important to us
Features
KIT contributed to the validation of Version 2.o and 2.1 using KIT facilities e.g. QUENCH, CORA
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

6. The ASTEC2.0 Simulation of PWR SA Sequences with and without SAMG
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

7. KIT Approach for PWR SA Simulations (1/3)
Steps:
Integral plant model
Predict stationary plant conditions
Extend model depending of scenarios
Activate physical models for in-vessel phenomena
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

8. KIT Approach for PWR SA Simulations (2/3)
Model Extension
Reactor Protection System
AM procedures
Mobile equipment
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

9. KIT Approach for PWR SA Simulations (3/3)
Physical phenomena:
Chemical interactions
Corium oxidation
Material interactions (Ag-Fe-Ni-Zry)
Movement of materials
Stratification lower plenum
Mechanical behaviour
Vessel failure
Core Ring 1
Core Ring 2
Core Ring 3
Core Ring 4
Core Ring 5
Core Ring 6

10. Investigated SA Scenarios with ASTEC2.0
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

11. ASTEC V2.0 Simulations: Selected scenarios
Medium Break LOCA (testing purposes)
Small Break LOCA (risk core damage)
Station Blackout (risk containment damage)
Put the screen in white and do the bridge by word
Hypotheses:
No surge line failure
No 100 K/h cooldown
Passive seals MCPs
No temp-induced SGTR
I. Gómez García-Toraño, et. al (2017). Investigation of SAM measures during selected MBLOCA sequences along with Station Blackout in a generic Konvoi PWR using ASTECV2.0. Annals of Nuclear Energy, 105, 226–39.
I. Gómez García-Toraño, et. al (2017). Analysis of primary bleed and feed procedures during selected SBLOCA sequences along with Station Blackout in a generic Konvoi PWR using ASTECV2.0. Annals of Nuclear Energy. Submitted.
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

12. Total Station Blackout Reference Sequence
6.14 RPV-failure at high P!
0.33 h: LL_SGA/B < 4 m
2.61 h: oxidation starts
3.4 h: Clad melting
3.84 h: first corium slump into LP
4.18 h: total core uncover
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

13. Total Station Blackout Potential Accident Management Measures (1/2)
SAMGs
SAMGs
I. Gómez García-Toraño at. Al (2017) Assessment of selected SAM measures during a Station Blackout in a generic Konvoi PWR using ASTECV2.0. Annals of Nuclear Energy. Submitted.
~ 120 simulations performed
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

14. Total Station Blackout Potential Accident Management Measures (2/2)
Reflooding with mobile equipment
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

15. Total Station Blackout Core Reflooding (after PSD)
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

16. Total Station Blackout Core Reflooding (after PSD)✓ ✓
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

17. Total Station Blackout Core reflooding (after PSD)✓ ✓
Deployment order of mobile pumps within 1 h after SBO to prevent melting!
IAEA Conference on Topical Issues in Nuclear Installation Safety, 6-9. June 2017

18. Conclusions Contribution to further development of SAMGs in Konvoi PWR
Demonstration of ASTEC V2.0 capabilities to perform severe accident analysis in PWR
Robustness, numerical stability (Version 2.1 is even better), etc.
Contribution to further development of SAMGs in Konvoi PWR
PBF should be initiated at CET=400 °C or with a 20 min delay by means of all pressurizer valves to delay vessel failure
Reflooding
should be started when CET=650 °C is reached with injection rates > 20 kg/s to prevent RPV-failure
must occur min before 20 ton of corium has been relocated into the LP to prevent RPV failure regardless of injected mass flow rate
Outlook:
Repeat plant simulations with latest ASTEC V2.1 using converted models (2.0 to 2.1)
Strong cooperation with code developers and other R&D institutions needed
KIT provide experimental data (QUENCH BWR, LIVE) for code validation