A1256655346EiTmw

1
The Vision of the European Sustainable Nuclear
Energy Technology Platform Strategic Research
Agenda on the Safety RD for GEN-IV Reactors
G.B. Bruna, IRSN
2
Strategic Research Agenda Cross-cutting
Activity Safety

• Context 1/2
• ? The main objectives, structure and organization
  of both SNE-TP and SRA are to be presented by M.
  Hugon,
• ? It is only worth mentioning here that Safety
  is included in the Cross-cutting Items

3
Strategic Research Agenda Cross-cutting
Activity Safety

• Context 2/2
• Very effective collaboration among Contributors
  (32 from 8 countries and 20 organizations),
• Many Contributors have participated in some
  selected parts only,
• In general, Contributors for Current and Advanced
  and Innovative Fission Reactors are different.

4
Country Company Name EMAIL adress
Belgium TRACTEBEL Christophe Schneidesch Christophe.Schneidesch_at_tractebel.com
France CEA EDF IRSN Frank Carré Michel Labatut PatriK Raymond Claude Renault Gérard Labadie Olivier Marchand Tatiana Ivanova Véronique Rouyer Thierry Albiol Giovanni B. Bruna Alain Chabod Jean Couturier Martial Jorel Jean-Claude Micaelli frank.carre_at_cea.fr michel.labatut_at_cea.fr patrik.raymond_at_cea.fr claude.renault_at_cea.fr gerard.labadie_at_edf.fr olivier.marchand_at_edf.fr tatiana.ivanova_at_irsn.fr veronique.rouyer_at_irsn.fr thierry.albiol_at_irsn.fr giovanni.bruna_at_irsn.fr alain.chabod_at_irsn.fr jean.couturier_at_irsn.fr martial.jorel_at_isn.fr jean-claude.micaelli_at_irsn.fr
Finland VTT Seppo Vuori Seppo.Vuori_at_vtt.fi
Germany FZK EON-Energie GRS IBM Werner Maschek Tromm, Walter Berlepsch von Thilo Victor Teschendorff Burkhard Steinmacher-Burow Werner.Maschek_at_iket.fzk.de Walter.Tromm_at_nuklear.fzk.de Thilo.Berlepsch_at_eon-energie.com victor.teschendorff_at_grs.de STEINMAC_at_de.ibm.com
Italy DelFungogieraEnergia ENEA POLIMI University of Rome / SRS University of Rome Luciano Cinotti Stefano Monti Marco Ricotti Antonio Naviglio Augusto Gandini luciano.cinotti_at_delfungogieraenergia.com stefano.monti_at_bologna.enea.it marco.ricotti_at_polimi.it an.naviglio_at_srs.it augusto.gandini_at_uniroma.it
Spain CIEMAT CNS Tecnatom UPM Luis Enrique Herranz Puebla Javier Hortal Villadoniga Tallaon José Ignacio Eduardo Gallego luisen.herranz_at_ciemat.es fjhr_at_csn.es villadoniga_at_tecnatom.es eduardo.gallego_at_upm.es
Switzerland PSI Salih Güntay salih.guentay_at_psi.ch
United Kingdom Nexia Andrew Worrall andrew.worrall_at_nexiasolutions.com
5
Strategic Research Agenda Cross-cutting
Activity Safety
Summary of the SRA Safety Chapter ? Forewords
? Uncertainty analysis and safety
margins two cross-cutting topics for safety
research ? Current Reactors ? Advanced and
Innovative Fission Reactors
6
Strategic Research Agenda Cross-cutting
Activity Safety

• The connection between safety research and
  regulation is mandatory in the nuclear
  technology.
• Information supplied by the research should be
  affordable, useful and helpful for the
  regulators, providing them with clear technical
  statements, despite the assumptions and
  uncertainties that sometimes cannot be easily
  quantified,
• Safety research has to accompany nuclear
  installations throughout all phases of their
  life, from concept definition, through design,
  licensing, construction and operation, up to
  decommissioning,
• Even if the excellent performance record of
  existing installations might suggest that a high
  safety level can be achieved without new huge
  research efforts, consciousness of research needs
  should be maintained, focussing on new trends,
  supporting public information and training.

7
Strategic Research Agenda Cross-cutting
Activity Safety

• Anticipatory research should look ahead to safety
  questions that may arise in the future, due to
  changes in the design and operating-mode, and the
  appearance of new concepts,
• The role of the future research should foster in
  an improved international cooperation to promote
  achieving common understanding of the safety and
  its standards, mainly when dealing with the
  advanced and innovative concepts which are
  intended to
• intrinsically eliminating severe accidents from
  occurring,
• reducing either their probability or the level
  of their expected consequences.
• This is done by design, not necessarily by
  addition of safety systems, which requires
  integrating since the beginning of the conceptual
  phase, the deterministic and the probabilistic
  approaches.

8
Strategic Research Agenda Cross-cutting
Activity Safety
?The ultimate goal of nuclear safety is to
prevent unacceptable radiological releases to the
public and/or to the environment. Protective and
safety systems or features are intended to
Preserve the integrity of the different physical
barriers, Mitigate the effects of their
failures and should provide the necessary level
of margins The regulatory acceptance of the
limiting values of variables is set
sufficiently high as to assure conservatism with
respect to the onset of damage Safety
Margins are enforced on safety variables.
9
Strategic Research Agenda Cross-cutting
Activity Safety
?A nuclear plant safety analysis is
traditionally performed adopting either a
deterministic or a probabilistic approach, or
both in combination ?The deterministic
approach accounts for a number of limiting
transients (Design Basis Accidents - DBA -) to
which conservative rules are enforced on
parameter values and system availability ?The
probabilistic approach treats occurrence events
in a probabilistic domain. It privileges the
completeness of the scenario set and adopts the
best-estimate methods.
10
Strategic Research Agenda Cross-cutting
Activity Safety
An extension of the concept of Safety Margins
has been recently proposed. ? The set of the
Design Basis Accidents was extended to the almost
complete set of all credible scenarios, including
out of design situations, which generates a risk
space ? The use of realistic dynamic models
is encouraged and the end state of a sequence is
no longer based on the use of success criteria
for safety functions ? Uncertainties of several
types can be explicitly taken into account in the
calculation of the conditional damage
probabilities.
11
Strategic Research Agenda Cross-cutting
Activity Safety
Safety variable distribution (Barrier or System
integrity)
Likelihood of Barrier failure or System loss
Safety Margins
12
Strategic Research Agenda Cross-cutting
Activity Safety (Current Reactors)

• Priority topics for action (short-term within the
  FP7)
• issues to be either implemented or reinforced
  
• Current Reactors 1/3
• Reactor Physics and Dynamics
• Thermal-Hydraulics
• Criticality
• Nuclear Fuel
• - Human and Organisational Factors
• - IC and Electrical Systems

13
Strategic Research Agenda Cross-cutting
Activity Safety (Current Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Current Reactors 2/3 -
Aggression and Hazards In recent years, new
threats are coming up forcing to focus not only
on internal hazards, but also on the destructive
action of external agents including the time.
When assessing the safe behavior of a system, a
component or an equipment, its robustness and
resistance to the aging-related phenomena and to
all kind of external aggressions is to be
demonstrated, including ? Flooding, ?
Extreme whether condition, ? Seism, ? Fire
14
Strategic Research Agenda Cross-cutting
Activity Safety (Current Reactors)

• Priority topics for action (short-term within the
  FP7)
• issues to be either implemented or reinforced
  
• Current Reactors 3/3
• Plant Simulation
• Severe Accidents
• Emergency Management .

15
Strategic Roadmap Agenda Cross-cutting Activity
Safety (Current Reactors)

• Priority topics for action
• (short-term within the FP7, Current Reactors)
• - Extension of the SARNET network of excellence
  (Under advanced discussion),
• Harmonisation of the PSA practices (Project
  underway).
• Continuation of work under the EURANOS
  project within the area of nuclear emergency
  management and long term rehabilitation.

16
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Advanced and Innovative Reactors Advanced and
innovative reactors encompass a variety of
different designs and operating modes. They
span a very large set of configurations,
including small and large size cores,
fast-neutron and moderated spectra, gas, water
and liquid metal cooling, each one matching more
or less completely and comprehensively the
objectives of the GEN-IV roadmap.
17
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Advanced and Innovative Reactors Natural
resource optimization and waste minimization are
goals more likely affordable for systems with
fast neutron flux, such as SFR - Sodium Fast
Reactor -, GFR - Gas Fast Reactor - and LFR -
Lead Fast Reactor -. Graphite moderated, gas
cooled high temperature reactors such as the Very
High Temperature Reactor (V/HTR) are more likely
to be inherently safe they also have the best
potential for a diversified energy production
(electricity, but also industrial heat and
hydrogen).
18
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Advanced and Innovative Reactors Operating
experience can contribute to identify crucial
needs for Advanced and Innovative system
research, All the modifications adopted for
Current reactors and the associated safety
assessments should entail research, including
code development and experimental activity.
Experiments contribute to the knowledge because
they participate in the validation of the code
physical models and, may provide unexpected
results which allow disclosing hidden phenomena
and ignored variables.
19
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Advanced and Innovative Reactors Nuclear actors
are presently facing a very open landscape as
regards the industrial maturity of concepts.
The risk exists that the research effort
outcomes will show-up either quite poor or
straightforward or false. That is very
challenging from the safety point of view,
because the safety assessment is strictly tied to
design features, the details of which are hardly
disclosed and remain widely unknown for the most
concepts at the present stage of development.
20
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
French SFR Prototype Design Schedule
21
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
SFR 1/2 ? Sodium technology risk, could be
minimized through substituting conventional steam
turbine energy conversion systems with gas
turbine and Brayton cycle conversion, ? The
merit of innovations in the reactor design to
enhance safety is to be assessed through normal
and accidental operating transient analyses in
terms of robustness of the safety approach and
effectiveness of arrangements made to prevent
hypothetical core damage and minimise its
consequences.
22
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
SFR 2/3 ? Special RD efforts are to be devoted
to design features enabling to practically
preclude significant energy release in case of
Severe Accident, ? That should be searched for
through adoption of optimised core design
features such as the geometry of the fuel
subassembly, the relative volume fraction of core
materials, the density of heavy metal within the
fuel and the possible use of light materials to
moderate neutrons and increase the Doppler
Coefficient.
23
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
SFR 3/3 ? Other core desirable features for
enhanced safety include reducing reactivity swing
and increasing temperature margins, ? The
mechanical behaviour of the core and specific
design options are to be carefully investigated
so as to minimise the risk of core compaction,
? Innovation in core instrumentation and
surveillance should allow for early detection of
abnormal situations.
24
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
GFR 1/2 ? Different safety approaches (such as
those adopted for HTRs, -High Temperature
Reactors- and LWRs -Light Water Reactors-) should
be compared to define suitable procedures for the
safety assessment, ? The exclusion approach
should be fully discussed and validated and the
Risk Informed methodology applied all along the
pre-conceptual design phase, ? A list of Design
Basis Accidents DBA list- should be established
for safety and margin assessment.
25
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
GFR 2/2 ? Several safety systems, relying on
intrinsic properties of materials and system
arrangements as well as on active devices, have
been already studied during the exploratory
phase, such as the core cooling function in tight
relationship with the LPA -Loss of Pressure
Accident, ? The other safety functions should be
analyzed in accordance to the DBA list, ? To
cope with any potential danger situation,
suitable passive or active systems should be
implemented.
26
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
V/HTR 1/3 ? Industrial heat generation
process requirements would be quite different
from electricity generation ones, and much more
versatile, which will demand a high flexibility
of the nuclear heat source however
competitiveness of nuclear energy is usually
achieved via standardisation, ? Competitiveness
and flexibility requirements will have to be
reconciled through a conceptual design phase, ?
The feasibility demonstration is to performed of
a very robust nuclear heat source that can
accommodate different operational requirements
and loads, a flexible coupling system matching
the nuclear and industrial applications.
27
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
V/HTR 2/3 ? Safety challenges are raised by the
coupling with conventional energy-production
facilities, which may propagate instability and
perturbations to the reactor, through
intermediate heat exchangers. ? The
demonstration of the feasibility of the coupling
of the reactor with process heat applications and
cogeneration is actually the main challenge for
the short term for reactor-systems such as the
V/HTR.
28
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
V/HTR 3/3 ? Several safety systems, relying on
intrinsic properties of materials and system
arrangements as well as on active devices, have
been already studied during the exploratory
phase, such as the core cooling function in tight
relationship with the LPA - Loss of Pressure
Accident- the other safety functions should be
analyzed in accordance to the DBA list, ? To
cope with any potential danger situation,
suitable passive or active systems should be
implemented.
29
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
? Major Safety concerns for GEN-IV Minimizing
the risks attached to the coolant (sodium lead,
), Practically precluding large energy
release in case of severe accident (even
hypothetical), Minimizing the system
vulnerability to external events and
aggressions, Assessing the impact of MA -Minor
Actinides- bearing fuels, Diversifying the
safety systems (e.g., decay heat
removal), Developing an improved
instrumentation for early detection of abnormal
situations, Developing an improved
instrumentation and techniques for in service
inspection and repair.
30
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
? The relevant RD activity can be grouped in
several main fields of endeavour Core
Physics and Simulation, Residual Heat
Removal, Fuel Integrity, Fission
Product Release, Reduction of Major Risk
of a Broad and Severe Damage of the Core,
In Service Inspection and Repair.
31
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
1/8 ? Core Physics and Simulation An
increased heterogeneity in space and energy and
the mutual interactions between the neutron and
temperature fields should claim new and enlarged
3D computation capabilities and an extended need
for probabilistic techniques and coupling,
Consistency and robustness of neutronics design
of systems should be searched for,
Capabilities for uncertainty and sensitivity
analysis, a relevant issue for the assessment of
any new and advanced design, should be provided.
32
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
2/8 ? Residual Heat Removal Fuel cooling
by liquid natural convection, Fuel cooling by
gas natural convection and heat radiation,
Heat removal by active safety systems.
Existing tools, such as the CFD - and the
thermal-hydraulics codes should be sufficient,
Adequate experiments should be carried-out to
contribute to the enlargement of data-bases for
the qualification of the codes, Emphasis
should be put on passive systems, such as the
natural convection in the loops.
33
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
3/8 ? Fuel Integrity 1/2 The integrity of
reactor fuel will be a major issue for the safety
assessment of GEN-IV concepts. To demonstrate
robustness of the fuel and its resistance to the
operation and accidental transients, improvements
and adjustments should be made in computation
tools and devoted experimental programs be
developed for physical assessment and
qualification. According to the fuel features
and design, it is straightforward that up-dating
and experiment should be reactor
concept-oriented.
34
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
4/8 ? Fuel Integrity 2/2 The larger effort
is foreseeable for HTR/VHTR concepts, which,
despite their proven design, have accumulated a
quite limited operation-experience and, far more,
for GFR, However, the simulation strategy
should be significantly the same as for current
NPPs simplified models should be derived for
industrial and assessed simulation tools, the
development of such models should be backed by a
multi-scale approach, It could be recommended
to set-up a global comprehensive strategy to
define the experiments against which the
elementary and global assessment of models will
be made.
35
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
5/8 ? Fission Product Release According to a
reduce risk for S.A., it does not appear as
strictly necessary increasing the present
accuracy in predicting the potential consequences
of severe accidents, but new actions should be
initiated to adapt and assess the current
computation tools to GEN IV fuels, materials and
designs. That will require development of new
experimental programmes including both analytical
and integral tests to guarantee that all major
phenomena have been accounted for. As for
current NPPs, it should be recommended to take
advantage from the impending RD activity and,
whenever possible, back-up the simplified models
with more detailed ones.
36
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
6/8 ? Reduction of Major Risk of a Broad and
Severe Damage of the Core 1/2 Some
concepts, such as the HTR/VHTR, are more
inherently safe than others, such as the GFR, due
either to a slower kinetics, a larger thermal
inertia or both, and an enhanced capability to
evacuate passively residual power, Relevant
issues should include ways to Preventing a
local core melt-down from degenerating into a
whole-core melt-down, Preventing
recriticalities through early fuel relocation,
Understanding the mechanism of propagation of
melting, Appreciating the consequences on
containment integrity of a whole-core melt-down.
37
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
7/8 ? Reduction of Major Risk of a Broad and
Severe Damage of the Core 2/2 Codes are in
current use for NPPs. Appropriate experimental
programmes have been initiated in the 80s to
assess these models, It is likely that these
codes could be used for the preliminary
assessment, provided that some complementary
development works will be carried out, The
adaptation of LWR codes to HTR/VHTR and GFR
concepts seems possible nevertheless all should
be revised and reassessed against a new and
appropriate experimental data.
38
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Priority topics for action (short-term within the
FP7) issues to be either implemented or
reinforced Advanced and Innovative Reactors
8/8 ? In Service Inspection In Service
Inspection will be relevant to the Defence in
Depth of all Innovative concepts, The issue
should be mainly addressed for Liquid Metal
Reactors , due to the opacity of the metal, its
temperature and high heat transfer coefficient,
as well as the need to minimize the "drainings"
of the circuits and components, to avoid oxide
production. Should designers favour concepts
allowing easier accessibility for control, repair
or equipment removal, an important RD effort
would be necessary on innovative and more
efficient non destructive inspection and control
devices.
39
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Concluding Remarks 1/2 The need for new
experimental and simulation tool, aimed at
sustaining safety analyses, should be focussed
for GEN-IV in a definitively new perspective,
The general public has generally been accustomed
to get limited access to the results of nuclear
safety research and has experienced difficulties
in understanding the actual meaning of research
results. Today, the awareness on safety needs
is completely different the public acceptance
plays a key role and may strongly affect the
profitability of an investment in the nuclear
field, the cost of experimental activities calls
for participation of partners at the
international level.
40
Strategic Research Agenda Cross-cutting Activity
Safety (Advanced and Innovative Reactors)
Concluding Remarks 2/2 The simulation tools
should be conceived and the experimental results
of the Rd should be presented in such a way as
? to be really user friendly, ? to support
their adoption and, as a consequence, the real
dissemination of a nuclear knowledge and
confidence, and of the capability of assessing
the behaviour of NPPs under normal and abnormal
conditions, ? to get a confidence on phenomena
and a capability to manage nuclear technologies.