1. Severe Accident Modeling and 3D Graphic Visualization
Authors: Dr. Vladimir Nosatov, WSC
Dr. Wei Huiming, CNPSC

2. Contents
Company Brief Introduction
Severe accidents’ (SA) phenomena
Integral Codes available for SA simulation
Using MELCOR-2.1 models for SA Real-Time simulation on BARAKAH FSS
Examples of SA model using in FSS
2D and 3D Graphical Visualization of SA results

3. WSC Company Overview Technology Driven Company
Research Oriented – over 20% of gross profit goes into R&D
Employees: ≈ 85; Multidisciplinary team of nuclear, mechanical, electrical, chemical engineers, physicists and computer scientists, 30% with advances degrees.
Headquarters in Frederick, Maryland, USA
Main Business - Power Plant Simulation
Nuclear Power Plant Simulators 40%
Conventional Power Plant Simulators 30%
Simulation Assisted Engineering 20%
Navy and Marine Simulation 5%
Process and Pipelines 5%
ISO 9001:2015 Certified

4. WSC HQ Location

5. WSC Simulation Technology
High Fidelity Simulation for use in:
Development of Replica Training Simulators
Nuclear, Coal, Combined Cycle & Gas Plants, Solar, Process, Pipeline…
Part-Task and Full-Scope Simulators
Classroom Simulators
Web based simulators
Simulation Assisted Engineering (SAE)
System Analysis and Design
Human Factors Engineering
Logic and Control Testing, V&V
Plant Optimization
Plant Test and Operating procedures – e.g. commissioning procedures

6. WSC Simulator Installations6

7. Our Customers

8. Nuclear Full Scope Replica Simulators
China, CNPSC Ningde
Korea and UAE KHNP Shin Kori and Barakah APR1400
Taiwan, TPC Lungmen
Northrop Grumman Ship Building
Bettis / Knolls Atomic Power Laboratory
General Dynamics Electric Boat
USA, APS Palo Verde 8

9. Barakah Three (3) MCR Full Scope Simulators

10. WSC Training and Engineering Simulators
3KEYSOFTWARE

11. Simulation Technology Overview
Software Products Suite for Comprehensive Plant Coverage
3KEYMASTER™ Simulation Platform and Modeling Tools - Flagship for this Suite
Graphical Engineering Station for Simulation Development and Control / Instructor Station
2-Phase Flow network Tool
Electrical Network Tool
Logic & Control and Relay Tools
Component Tool and Library
3KEYRELAP5-RT™ – Adaptation of INEEL’s RELAP-3D©, including NESTLE, to run in real-time with visualization, provides best-estimate engineering grade modeling for Thermal-hydraulics and Neutron Kinetics
3KEYSAA™ – Severe Accident Analysis Models MELCOR / MAAP
3KEYDCS™ – is our solution for Distributed Control Systems that provides accurate emulation for Control and Logic, Man-Machine Interfaces, including trend and alarm displays
3KEYSAFE™/3KEYCATALOG ™ – Configuration Management Solution for managing the simulator configuration to the reference plant design through various stages of plant design evolution
3KEYTOUCH™ – Alternative Training Delivery Platform
3KEYITS/3KEYSTUDENT™ – Web and Classroom based Simulator Lesson delivery

12. MELCOR Tutorial Schematic of Test Problem

13. Physical Phenomena Inherent in Severe Accidents
Thermal-hydraulic response of the primary, secondary and containment;
Thermo-mechanical and chemical processes in the Core: fuel heat-up, cladding oxidation, fuel degradation, and core material melting and relocation;
Heat-up of reactor bottom head, mechanical loading and failure, and transfer of core materials to the reactor cavity;
Core-concrete attack in reactor cavity and ensuing gases and aerosols generation;
In-vessel and ex-vessel hydrogen production, transport, and combustion;
Fission product release (aerosol and vapor), transport, and deposition, including scrubbing in water pools, particle agglomeration and gravitational settling;
Impact of engineered safety features on thermal-hydraulic and radionuclide behavior.

14. Integrated codes available for Severe Accident simulation
MELCOR
MAAP
SCDAP/RELAP5
MELCOR-2.1 code was chosen base on 3 main criteria:
Possibility to get license;
Code ability to simulate severe accidents in real-time;
Code ability to simulate all main phenomena during severe accident.

15. Visualization of Core Components (PWR) in MELCOR Code
Control Rods (NS)
Fuel Assemblies (FU + CL)
Core Baffle or Shroud (SH)
Core Formers (FM)
Core Support Barrel (HS)
Vessel Cylinder (HS)
Particulate in Channel (PD)
Particulate in Bypass (PB)

16. Switching Real-Time Simulation between RELAP and MELCOR
Using MELCOR-2.1 models for SA simulation on BARAKAH FSS
Switching Real-Time Simulation between RELAP and MELCOR
Logical event causing automatic switch to the severe accident model
Transferring data from TH (RELAP) model to SA (MELCOR) model
Switching signals and indications to the SA model

17. RELAP and MELCOR Nodalization of BARAKAH RCS

18. FB and MELCOR Nodalization of BARAKAH Containment

19. BARAKAH Core region nodalization in Relap

20. Transferring data between RELAP and MELCOR

21. Scheme of data Conversion from RELAP to MELCOR
Data base
MELCOR
Data base

22. RELAP - MELCOR Transition Functionality
Seamless transition between RELAP and MELCOR severe accident model is performed “on the fly”. At that point in time the following has to be done:
The physical parameters specific to the current simulation state (such as fuel temperatures, moderator densities etc.) have to be communicated to MELCOR model. This has to be done in such a way that the MELCOR model will start the computation using the actual physical parameters.
The other modeling tool (RELAP) has to stop its modeling because both perform modeling of the same parts of the nuclear power plant.
MELCOR has to start the computation using the physical parameters specific to the current simulation state that have been transferred to the MELCOR model.
RELAP application is halted

23. 3KEYMASTER Settings before and after switchover

24. Examples of SA model using in FSS
MCR personal, Technical Support Engineers, Emergency response Team training for response in conditions of core severe damage;
Drills for Emergency response Team and Accident management participating in severe accident mitigation;
Verification of Emergency Operation Procedure and Severe Accident Management Guidelines

25. Scenarios for SA model verification on BARAKAH FSS
SA initiated by SBO event;
SA initiated by LB LOCA;
SA initiated by SB LOCA;
SA initiated by TLOFW;
SA initiated by TLOCCW

26. Pressure in Secondary Side

27. Pressure in Pressurizer

28. Cladding temperature in Core

29. Hydrogen concentration in Containment

30. 2D Graphical Visualization of SA results

31. 2D Graphical Visualization of SA results

32. 2D Graphical Visualization of SA results

33. 3D Graphical Visualization of SA results

34. Questions

35. WSC invites YOU

36. WSC Contact Information
Thank You!
Dr. Vladimir Nosatov
WSC, Inc.
7196 Crestwood Blvd, Suite 300
Frederick, MD 21703