Post on 15-Mar-2020
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Enhancing nuclear safety
ASTEC status and perspectives
CHAILAN Lionel - ASTEC project leader
On behalf of the ASTEC development team
Severe Accident Department
IRSN Nuclear Safety Division
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Outlines
▌Recent safety applications with ASTEC V2.1 at IRSN
▌ASCOM project
▌Under development ASTEC V2.2 version
▌ASTEC+ trajectory and perspectives
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 2/24
Outlines
▌Recent safety applications with ASTEC V2.1 at IRSN
▌ASCOM project
▌Under development ASTEC V2.2 version
▌ASTEC+ trajectory and perspectives
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 3/24
Safety analyses: expertise of EDF proposals for Operating Fleet Lifetime Extension
▌Safety study: expertise of EDF proposals for Plant Lifetime Extension in the frame of the post Fukushima CSE
In the frame of the Plant Life Extension program for Gen II PWRs operation beyond 40
years, the French regulator supported by IRSN requested improvements to increase the
safety levels towards those of the Gen III EPR safety level. For SA, limited in space and
time population protection measures are targeted.
First set of modifications to avoid reactor concrete basemat melt-through by the
molten core after vessel failure : dry spreading in an area larger than the reactor
vessel pit rapidly followed by a passive top cooling of the corium.
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 4/24
Second set of modifications to remove the decay heat from the containment
without opening the EFCVS (U5 line including metal pre-filter and sand bed filter)
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Safety analyses: expertise of EDF proposals for Operating Fleet Lifetime Extension
Ultimate heat sink has to be
lined by the EDF nuclear rapid
response force (FARN)
Delay time for ultimate heat
sink implementation is
evaluated by EDF to 24 hours
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 5/24
CSARP Technical Review Meeting, Washington,
June 5-7, 2018
▌ PWR 900 MWe ASTEC reference datasets have been updated to include these
proposed modifications, including the corresponding severe accident
management actions and taking into account the various basemat concrete
composition of the fleet that significantly impacts the concrete top cooling.
▌ Corium top cooling during MCCI models have been updated specifically for these
safety analyses.
water
injection concrete
bubbling
corium
pool
quenched
upper crust
dry upper
crust
water
ingression
erupted melt
debris
Safety analyses: expertise of EDF proposals for Operating Fleet Lifetime Extension
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
Heat exchange at corium/water
interface: Nukiyama curve
Ingression : Lister
Eruption: Fontaine / Ricou & Spalding
Assessment on SSWICS and CCI
experiments (including the recent
ANL/EDF program)
6/24
EDF Rescue team activation (24 h)
Safety study: expertise of EDF proposals for Plant Life Extension
Containment over-pressurization
Depending on the concrete composition, two
main hazards are challenging the
containment integrity:
• Silicious concrete implies strong basemat
melt-through risk
• Limestone concrete enhances fast
containment pressurisation
In any case, the delay for the activation of
EDF nuclear rapid response force is crucial
Basemat melt-through
▌ ASTEC V2.1 results regarding MCCI phase
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 7/24
Safety study: Spent Fuel Pool Accident Mitigation
CPA nodalization of SFP building Thermal-hydraulic validation of CPA model
by comparison with FLUENT computation
Total, Aerosol and gas releases
Main releases are in aerosol form: I2O5, CsI,
Cs2I2
Main gaseous released species are: CH3I, I2
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 8/24
SFP – evaluation of mitigation strategies
▌Several mitigation strategies were evaluated
External spray outside the SFP building
Spray in a small room disposed between SFP building and environment
Internal SFP building spray
Safety study: Spent Fuel Pool Accident Mitigation
External spray Small spray located in an
exit lock
Internal spray
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
SFP building
9/24
Safety study: Spent Fuel Pool Accident Mitigation
▌Preliminary Observations
Without mitigation strategy applied:
Non-negligible retention of SFP building itself
No H2 explosion risk
Main gaseous release carried by organic iodine
With mitigation:
Negligible effect of sprays when located outside the SFP building
Efficient effect of spray located inside the SFP building
Work to be continued in particular in the frame of H2020 MUSA project
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 10/24
Outlines
▌Recent safety applications with ASTEC V2.1 at IRSN
▌ASCOM project
▌Under development ASTEC V2.2 version
▌ASTEC+ trajectory and perspectives
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 11/24
12/13
▌ASCOM Project conduct
4-year long in-kind R&D project (Oct. 2018 - Sept. 2022) coordinated by IRSN in the
frame of the NUGENIA/TA-2 (SARNET)
▌ASCOM Project objectives
ASCOM main objective is to help amplify and accelerate the on-going process of
making ASTEC a fully reliable tool for SA analyses and accident management in a
wide range of nuclear safety applications by strengthening the various R&D
activities of the ASTEC COMmunity in a consistent way
▌ASCOM Project partnership
Today, ASCOM gathers 25 partners (TSO, research, universities, industry) :
IRSN, EDF R&D (France), KIT, HZDR, RUB-PSS (Germany), ENEA, Univ.Pisa (Italy), CIEMAT (Spain), NUBIKI (Hungary), IVS (Slovakia), UJV (Czech Rep.), INRNE (Bulgaria), RATEN ICN (Romania), LEI (Lithuania), VTT (Finland), IJS (Slovenia), FER (Croatia), JRC (EC), Tractebel-ENGIE (Belgium)
SEC NRS, NRC-KI (Russia), Energorisk (Ukraine)
NSC (China), NUS (Singapore)
Univ. Utah (U.S.A)
ASCOM : General introduction to the project
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 12/24
13/13
▌ASCOM project structure
ASCOM is spread over 6 Work-Packages, whose major ones cover:
Continuous validation of ASTEC V2 series
ASTEC applications at plant scale, along with cross-walk activities with other
reference SA analysis codes (MELCOR, MAAP, …) for Gen.II LWRs
Development of few new “generic” reference open input decks to extend
the ASTEC V2 applicability to some other kinds of nuclear installations:
– Gen.III & III+ PWRs with IVMR strategy (e.g. AP1000)
– Gen.III & III+ VVERs (e.g. VVER-1200)
– SMRs
– SFPs
▌Yearly workshops
Next workshop to be hosted by KIT in September 2019
▌A crucial community for best-estimate calculations
SA codes necessitate experienced users
Sharing experience and best practice is essential for reliable calculations
ASCOM : General organization of the project
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 13/24
Outlines
▌Recent safety applications with ASTEC V2.1 at IRSN
▌ASCOM project
▌Under development ASTEC V2.2 version
▌ASTEC+ trajectory and perspectives
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 14/24
ASTEC V2.2
▌DEBRIS modelling: a new generation of degradation models in ASTEC
MAGMA
Melting and eutectic
formation
Relocation for
liquid fraction>0
DEBRIS
Granular flow,
interaction with
MAGMA
Creation on
several criteria
Melting temperature
of oxide lowered,
based on PHEBUS
experiment
Criteria of creation
currently investigated
on several scenarios
Fuel melting and relocation of the liquid fraction to magma was the unique
degradation mechanism assumed in ASTEC
Core degradation through creation of solid particles (so-called “debris”) is intended
to provide ASTEC with a complementary way to describe the degradation course
when solid debris can be generated under their melting temperature
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 15/24
ASTEC V2.2
▌DEBRIS modelling: models are operational, now ongoing validation
tasks are being conducted
Kingery/Vortmeyer*2
(best results with ASTEC V2.1)
Heat transfers models in porous media:
best fit of thermal conductivity in porous
media
Re-assessment against FPT4 experiment
(PHEBUS FP experiment characterized by an
initial debris bed), showed a good agreement
Thermal-hydraulic in porous media:
sensitity w.r.t wetting angle
PEARL experiments have been intensively
used to set up and validate the two-phase
thermal-hydraulic models in porous media
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 16/24
ASTEC V2.2
▌Current validation tasks aim re-assessing integral experiments and
accident with respect to the gain of debris models
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic
PHEBUS-FP FPT1 and FPT3 experiments
These experiments showed essentially melting
phenomena without clear evidence of debris creation:
how considering the debris in such situation?
PBF SFD-1.4 experiment
This experiment is considered being more representative
of TMI-2 accident and should be well adapted for
assessing the debris creation criteria
TMI 2 accident
The Three Mile Island accident revealed a large amount
of debris creation, likely related to strong thermal
gradient during reflooding
17/24
ASTEC V2.2
▌Thermal hydraulic models for high incondensable gases rates
Conditions frequently arising in the reactor cooling circuit components in
various situations:
Shutdown states scenarios calculations,
During reflooding after a large H2 production in the core,
SFP accidents and air-ingress scenarios
Models are required to operate in a large range of conditions, i.e. from pure
steam flow to pure incondensable gases flow
Implementation of adequate models is finished, re-assessment of improved
thermal hydraulic module CESAR is underway
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 18/24
ASTEC V2.2
▌ Several modelling improvements have been implemented to better
address the IVR strategy issues
Over-filling of the lower plenum: will be delivered with next V2.1 patch
planned in April 2019
• This situation will be handled by ASTEC V2.2
• Radiation through cavity has also been extended in this case, allowing
lower plenum pool to exchange by radiation with upper part of the core
and the vessel wall
ASTEC V2.2
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 19/24
Outlines
▌Safety applications with ASTEC V2.1 at IRSN
▌ASCOM project
▌Under development ASTEC V2.2 version
▌ASTEC+ trajectory and perspectives
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 20/24
▌ASTEC+: a new pathway for ASTEC development
Where most of the codes we are using have been developed for years
(or decades), we need to address their sustainability : ASTEC+ is an
evolutionary trajectory of the development of the future versions of
ASTEC targeting their modernisation.
New trajectory based on standardized software programming
approaches using the C++ scientific software programming platform
PELICANS (Open Source, developed by IRSN)
Where significant knowledge, methods and tools have been developed
for power reactors, there is a need to globally consider the radiological
risks : extension of the scope of ASTEC to address with a risk-rated level
of accuracy - spent fuel pool, fuel reprocessing facilities, MTR, SMR,
naval…
Development of a set of tools and methodologies allowing coupling
with dedicated codes (internal/external)
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 21/24
▌ASTEC+: a new pathway for ASTEC development (ctd)
Where budget constraints apply to most of our organizations, there is a
need to streamline severe accident prognosis/diagnosis capabilities :
deterministic plus uncertainties, PSA, EP&R, desktop simulator.
Capitalization of knowledge and methods in SA framework,
progressive integration of modern algorithmics including surrogate
modelling
Where budget constraints apply and where the spectrum of potential
simulation objects is widening, this new trajectory also target at short
term a facilitated potential external co-development.
ASTEC+ project started in 2019 using so-called agile « user oriented » approach
In coherence with the global IRSN approach for the digital shift IRSN
2030
In close coordination with similar approaches implemented in the US
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 22/24
Chaining ASTEC and
aero-dispersion code pX
ASTEC V3.0 : new applications for ASTEC
Generalisation of
Surrogate models and
Bayesian Networks
Red oils accidents in
reprocessing facilities Coupling ASTEC and CFD code for SFP
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 23/24
That’s all, folks!
Thank you for your attention!
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 24/24
PEARL Experimental facility
▌ IRSN, Cadarache, France
▌Coolability of large heated debris beds
▌Steel particles heated by induction
▌Effect of pressure (1-10 bar), velocity, initial temperature (400°C-1000°C) on reflooding behaviour
▌Bypass around the debris deb simulates less degraded zone
Subcooled
water
Steam ↑↑↑ Overview
PEARL Experimental facility
Initial conditions
▌ Temperatures
▌ Liquid level
Boundary conditions
▌ Flow inlet
▌ Pressure outlet
▌ Electrical power
Experiment ASTEC
Modelling in ASTEC V2.1
IRSN CONTRIBUTION TO FASTNET PROJECT
▌FASTNET : an European H2020 project dedicated to emergency preparedness and response.
Use of Bayesian Networks and ASTEC code to help diagnosis in a SA
Three prototypic tools have been developed
A situation selector in a calculation grid
An iodine source term predictor (prognosis)
A diagnosis tool for plant state assessment at a given time of the accident
Scenario specification
ASTEC Simulations
DataBase
Data Learning
Validation
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 27/24
▌WP1: a calculation grid composed of 57 best estimate ASTEC calculations, simulating a PWR 1300 MWe
All ASTEC modules implied, various kinds of situation (LOCA of different sizes, SBO,
LFSG), various failure times of safety systems
▌WP2 phase 1 : Source term prediction ~30 000 SOPHAEROS calculations (~6 hours on 25 computing nodes)
Various kinds of ambient situations: dose rate/temperature in gas/liquid phase,
degradation, pH, various hypothesis about iodine behavior, Iodine related kinetics
reactions uncertainties as underlying variables
▌WP2 phase 2 : Vessel state prediction ~30 000 ASTEC calculations simulating a simplified PWR 900 MWe (~2 months on 25 computing nodes)
All ASTEC modules implied, LOCA with SI or not, CSS available or not, break size
between 1 inch to 12 inches, break located in hot or cold leg, containment overall
leak rate between 0.01 to 100 of “normal” leak rate
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IRSN CONTRIBUTION TO FASTNET PROJECT
9th Conference on Severe Accident Research, ERMSAR 2019,
March 18 - 20, 2019 - Prague, Czech Republic 28/24