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An approach for an extension of the deflagration model in containment code system COCOSYS to separate burned and unburned atmosphere via junctions

  • Johannes Hoffrichter ORCID logo EMAIL logo and Marco K. Koch ORCID logo
Published/Copyright: June 19, 2023
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Kerntechnik
From the journal Kerntechnik Volume 88 Issue 4

Abstract

In case of a postulated severe accident in a water-cooled nuclear power plant significant amounts of hydrogen (H2) and carbon monoxide (CO) can be generated and released into the containment or reactor building where it might form a combustible mixture with air assuming passive autocatalytic recombiners are not available. In case of ignition, pressure peaks might occur, that are relevant for the integrity of safety relevant equipment and the containment or reactor building. It is therefore important for safety analysis to be able to correctly predict combustion phenomena that might occur. The accident analysis code AC2 2021.0 which is developed by Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) includes the Containment Code System (COCOSYS version 3.1) for the simulation of containment phenomena. COCOSYS contains the model FRONT for the simulation of premixed deflagration of H2 and CO. Recent code validation using H2 deflagration tests conducted in the multi-compartment THAI+ test facility shows that the flame propagation stops prematurely in simulations of some tests. This is partly attributed to the missing separation of burned and unburned atmosphere which leads to a reduction in fuel concentration in not yet burning zones connected to a burning zone. Model improvement potential was identified which is addressed in this paper. A model extension to separate burned and unburned atmosphere via a junction model is proposed and implemented into a development version of COCOSYS 3.1. First validation results using the THAI test HD-39 are discussed that show improved prediction capability by the extended model.

Keywords: AC2 2021.0; code validation; deflagration modeling; hydrogen combustion; system codes; THAI test facility
Corresponding author: Johannes Hoffrichter, Plant Simulation and Safety Group, Ruhr-Universität Bochum, Universitätsstraße 150, Bochum 44801, Germany, E-mail:

Acknowledgments

The results were obtained using the GRS software package AC2 2021.0.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: This work was funded by the Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection under grant numbers BMWi 1501568 (VAMOCAAD) and BMUV 1501629 (AVAMO). The responsibility for the content of this publication lies with the authors.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

Nomenclature

Acronyms

AICC

Adiabatic Isochoric Complete Combustion

AMHYCO

Towards an Enhanced Accident Management of the Hydrogen/CO Combustion Risk (Project)

ASTEC

Accident Source Term Evaluation Code

ATLAS

Analysis simulator for interactive plant simulation

ATMOS_JUN

Atmospheric Junction Model

AVAMO

Analyse und externe Validierung der AC2 Modellbasis (Project)

BWR

Boiling Water Reactor

COCOSYS

Containment Code System

DDT

Deflagration to Detonation Transition

EXP

Experiment

FRONT

Flame Front Propagation Model

GRS

Gesellschaft für Anlagen- und Reaktorsicherheit gGmbH

HD

Hydrogen Deflagration

INST

Incompressible Transient Momentum Equation

LOCA

Loss of Coolant Accident

LP

Lumped Parameter

MCCI

Molten Corium Concrete Interaction

NEA

Nuclear Energy Agency

NPP

Nuclear Power Plant

OECD

Organisation for Economic Co-operation and Development

PAD

Parallel Attachable Drum

PSS

Plant Simulation and Safety group

PWR

Pressurized Water Reactor

RALOC

Radiolyse und Lokalkonzentrationsverteilung im Containment

RUB

Ruhr-Universität Bochum

THAI

Thermal-Hydraulics, Hydrogen, Aerosol, and Iodine

THAI+

Thermal-Hydraulics, Hydrogen, Aerosol, and Iodine ± multiple-compartment

TTV

THAI Test Vessel

Latin

A

area [m3]

c p

isobaric heat capacity [J/(kg K)]

c s

speed of sound [m/s]

C

correlation constant [–]

D

diffusion coefficient [m2/s]

d

diameter [m]

g

gravitational acceleration [m/s2]

h

height [m]

H

enthalpy [kJ/kg]

K

flow resistance term [1/(kgm)]

l

length [m]

L T

turbulent integral scale [m]

M

molar mass [kg/mol]

M ‾

average molar mass [kg/mol]

m

mass [kg]

m ˙

mass flow [kg/s]

E

correlation constant [–]

p

pressure [kg/(ms2)]

Q ˙

heat flow [kJ/s]

R

universal gas constant [J/(mol K)]

R F

reduction factor for elementary entities [–]

r

reaction rate [kg/s]

S

flame velocity [m/s]

T

temperature [K]

t

time [s]

U

flow velocity [m/s]

u ′

turbulence intensity [m/s]

V

volume [m3]

V ˙

volume flow [m3/s]

w

weight term [kg/(ms2)]

X

molar fraction [mol/mol]

Y

mass fraction [kg/kg]

Greek

α

coefficient in the Liu–Macfarlane correlation [–]

β

coefficient in the Liu–Macfarlane correlation [–]

δ

flame thickness [m]

∆

difference operator [–]

ε

small value (10−6) [–]

ζ

flow resistant value [–]

η

kinematic viscosity [m2/s]

κ

heat capacity ratio [–]

λ

friction coefficient for laminar flow [–]

ρ

density [kg/m³]

σ

flame surface ratio [m2/m2]

Subscripts

0

unburned atmosphere

1

burned atmosphere

c

constant

F

flame

H 2

hydrogen

H H V

higher heating value

( H 2 O ) v

steam (vapor)

i

component specific

J

junction

L

Laminar

max .

maximum

p

isobaric

r e f .

reference

T

turbulent

T Z

target zone

S Z

source zone

Z

zone

Superscripts

0

unstretched

Non-dimensional parameters

R e

Reynolds number

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Received: 2023-03-29
Published Online: 2023-06-19
Published in Print: 2023-08-28

© 2023 Walter de Gruyter GmbH, Berlin/Boston

Articles in the same Issue

  1. Frontmatter
  2. An approach for an extension of the deflagration model in containment code system COCOSYS to separate burned and unburned atmosphere via junctions
  3. Neutronic analysis of the European sodium cooled fast reactor with Monte Carlo code OpenMC
  4. Identification and tracing of radionuclides in low- and medium-activity liquid radwaste sources of G.A. Siwabessy reactor
  5. Performance evaluation of a currently in-use dry storage cask design for spent accident tolerant fuel loading case under normal operation condition
  6. Optimization of divertor design for Pakistan spherical tokamak
  7. Role of impurity and thermal noise on the radiation sources in ITER using DT fuel
  8. An investigation of multistream plate-fin heat exchanger modelling and design: a review
  9. Ensuring safety of new, advanced small modular reactors for fundamental safety and with an optimal main heat transport systems configuration
  10. Study on calculation model and risk area of radionuclide diffusion in coastal waters under nuclear leakage accidents with different levels
  11. Optimization of 200 MWt HTGR with ThUN-based fuel and zirconium carbide TRISO layer
  12. Experimental study on boiling heat transfer of γ-Fe2O3 nanofluids on a downward heated surface
  13. Evaluating the influence of radial power heterogeneity of fuel rod on its temperature in an accelerator driven subcritical system
  14. Heat transfer enhancement of heat exchanger using rectangular channel with cavities
  15. Calendar of events
https://doi.org/10.1515/kern-2023-0021
Keywords for this article
AC2 2021.0; code validation; deflagration modeling; hydrogen combustion; system codes; THAI test facility

Articles in the same Issue

  1. Frontmatter
  2. An approach for an extension of the deflagration model in containment code system COCOSYS to separate burned and unburned atmosphere via junctions
  3. Neutronic analysis of the European sodium cooled fast reactor with Monte Carlo code OpenMC
  4. Identification and tracing of radionuclides in low- and medium-activity liquid radwaste sources of G.A. Siwabessy reactor
  5. Performance evaluation of a currently in-use dry storage cask design for spent accident tolerant fuel loading case under normal operation condition
  6. Optimization of divertor design for Pakistan spherical tokamak
  7. Role of impurity and thermal noise on the radiation sources in ITER using DT fuel
  8. An investigation of multistream plate-fin heat exchanger modelling and design: a review
  9. Ensuring safety of new, advanced small modular reactors for fundamental safety and with an optimal main heat transport systems configuration
  10. Study on calculation model and risk area of radionuclide diffusion in coastal waters under nuclear leakage accidents with different levels
  11. Optimization of 200 MWt HTGR with ThUN-based fuel and zirconium carbide TRISO layer
  12. Experimental study on boiling heat transfer of γ-Fe2O3 nanofluids on a downward heated surface
  13. Evaluating the influence of radial power heterogeneity of fuel rod on its temperature in an accelerator driven subcritical system
  14. Heat transfer enhancement of heat exchanger using rectangular channel with cavities
  15. Calendar of events
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