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Overview and Status
Giacomo Grasso – FSN-SICNUC-PSSN
LFR Safety Design Criteria
TM on “Challenges in the Application of the Design Safety Requirements
for Nuclear Power Plants to Small and Medium Sized Reactors”
IAEA HQ, Vienna, Austria, 4-8 September 2017
Titolo della presentazione - Luogo e data
The Lead-cooled Fast Reactor
LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
The Lead-cooled Fast Reactor in GIF
GIF context
3 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Signatories Observers
The Lead-cooled Fast Reactor in GIF
4 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• EURATOM
• Japan
• Republic of Korea
• Russian Federation
• People's Republic of China
• United States of America
GIF LFR provisional System Steering Committee
Titolo della presentazione - Luogo e data
SSTAR
(USA)
Small-sized, battery type reactor with long core life
BREST-OD-300
(Russia)
Medium-sized, «pools-in-loop» type reactor + associated fuel cycle
The Lead-cooled Fast Reactor in GIF
5 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
(Europe)
Large-sized, integral type reactor closing the fuel cycle
ELFR
CLOSURE HEAD
CO2 INLET NOZZLE
(1 OF 4)
CO2 OUTLET NOZZLE
(1 OF 8)
Pb-TO-CO2 HEAT
EXCHANGER (1 OF 4)
ACTIVE CORE AND
FISSION GAS PLENUM
RADIAL REFLECTOR
FLOW DISTRIBUTOR
HEAD
FLOW SHROUDGUARD
VESSEL
REACTOR
VESSEL
CONTROL
ROD
DRIVES
CONTROL
ROD GUIDE
TUBES AND
DRIVELINES
THERMAL
BAFFLE
Reference systems for the GIF LFR pSSC
Titolo della presentazione - Luogo e data
GIF Roadmap as of 2002 GIF Roadmap 2014 update
The LFR potential
6 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Technological readiness
+10 y
+7 y
+5 y
+10 y
≈
+10 y
Titolo della presentazione - Luogo e data
The LFR potential
Acknowledged features
• Fast spectrum
For full management of natural resources
and waste through closure of the fuel
cycle
• High temperatures
For multiple applications along with
electricity production, e.g., hydrogen
production, co-generation, etc.
• Flexible design
For deployment into many and different
market segments, e.g., micro-batteries,
SMRs, large plants
7 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
The LFR potential
A growing interest
• BREST-OD-300 by ROSATOM-NIKIET (Russian Federation)
• SEALER by LEADCOLD (Sweden)
• CLFR by Westinghouse (USA)
• LFR-AS-200 by Hydromine Inc. (USA)
8 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
European situation
Framework objective
9 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
European situation
Framework objective
10 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Energy Union
Sustainability
Competitiveness
Security of Supply
Titolo della presentazione - Luogo e data
European situation
Framework objective
11 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
European situation
Context
12 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
European situation
Context
13 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
European situation
Context
14 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Commercialization
Commercialization
Commercialization
…
Titolo della presentazione - Luogo e data
European situation
EU LFR roadmap
15 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
ELFR
Commercial deployment
ALFRED
Demonstrator
Prototype
FoaK
Titolo della presentazione - Luogo e data
Main strength Main weakness
European situation
16 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
EU LFR roadmap
Extremely robust (prudent?) approach
to commercial maturity
• no excessive jumps between sizes
of reactors in successive steps
• progressive shift from proven (off-
the-shelf) to innovative (advanced)
solutions
• progressive increase of system
temperatures (for corrosion)
• progressive increase of system
performances
Perspective for market deployment
not earlier than 2050
• scarce attractiveness for industry
due to the seen time-to-pay
• very limited will to get involved in a
lengthy development, even for
specific innovative solutions
• issues in securing funds only from
public investment
• weakening of governmental
commitments following the poor
involvement of industry
Titolo della presentazione - Luogo e data
(few applications)
(few remote areas)
(high temperature
applications)
(proven technology
is better)
A Lead-cooled SMFR
Potential of SMFR in Europe
17 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Complement to
intermittent
energy sources
Replacement of
fossil PP
Non-electrical
applications
Military
applications
Power remote
areas
New nuclear
countries
Match
incremental
demand
(renewables target:
20% in 2020)
(proper power
range)
(no rapid growth)
Power required
Market potential
in Europe
Most interesting
opportunities for
SMFRs in Europe
Credits:
EU FP7 project
Grant # 605172
Titolo della presentazione - Luogo e data
A Lead-cooled SMFR
Perspective features
18 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• Simplification of design
significant reduction of capital cost thanks to elimination of unnecessary
components (e.g., intermediate loop)
System «Worthy» steel [kg/kW(e)]
GCR 20
Large SFR 5÷10
Gen-III/+ passive LWR 3
Gen-III/+ LWR SMR >3 (4÷5)
LFR 2
Mass of
concrete also
follows
proportionally
Titolo della presentazione - Luogo e data
A Lead-cooled SMFR
Perspective features
19 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• Simplification of design
significant reduction of capital cost thanks to elimination of unnecessary
components (e.g., intermediate loop)
reduction of O&M costs
• Extreme flexibility
excellent neutronics to easily target different missions (from battery to
iso-breeder)
• Enhanced safety
no safety implications from one unit to any other on the same site
• Potential for high-temperature operation
net efficiency from 38% to upper 40s (always >> than LWR SMRs)
opening to different applications and multiple market segments
Titolo della presentazione - Luogo e data
European situation
EU LFR roadmap
20 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
ELFR
Commercial deployment
ALFRED
Demonstrator
Prototype
FoaK
Titolo della presentazione - Luogo e data
A Lead-cooled SMFR
EU LFR roadmap
21 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Demonstrator
Prototype
FoaK ELFR
Commercial deployment
ALFRED Prototype
SMFR FoaK Anticipated
commercial deployment
Titolo della presentazione - Luogo e data
A Lead-cooled SMFR
An evolving deployment
• Materials for lower temperature
operation exist today
a first off-the-shelf design can be sold
to market in a very short term
(time for demonstration)
opportunity to match the retirement of
the reactors of the fleet presently
operating
• Advanced materials are being
developed and qualified
an improved design can be
developed with minor modifications
even higher performances can be
sought for a mid-term deployment
22 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Short-term SMFR
Medium-term upgraded
SMFR
Titolo della presentazione - Luogo e data
LFR Safety Design Criteria
LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
The information presented in the following slides
is based on material produced by the
GIF LFR pSSC.
Acknowledgement
24 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
References and position
Hierarchy of standards
25 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
References and position
Reference documents
26 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
References and position
Reference documents
27 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Development process
Objective
To present a set of reference criteria for
the design of systems, structures, and
components of LFR systems with the
aim of achieving the safety goals of the
Generation-IV reactor system
28 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Development process
Rationale
To demonstrate that IAEA safety
requirements for design (SSR-2/1) are
essentially applicable to LFRs, and
require only minor modification
29 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Development process
Approach
To minimize differences between the
LFR SDC and the IAEA safety
requirements (SSR 2/1) to the extent
necessary
30 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Development process
Methodology
• Present draft of LFR SDC has been developed by GIF LFR pSSC in
2014-2015
• The work has been based on the SDC for the Sodium-cooled Fast
Reactor (SFR), since the GIF LFR and SFR systems share a
number of design solutions and some safety-related phenomenology
• It was also found useful to use the same structure and methodology
of the already existing SFR SDC
31 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Development process
Methodology
• Specific technical features of LFRs are considered
• Latest knowledge is incorporated, incl. R&D results & lessons
learned from the accident at the TEPCO Fukushima Daiichi NPP
32 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Development process
Criteria†
• Applicable as is
• Applicable with interpretation
No modification is required, but the rationale for the application of the
requirement to the design is different than that of the standard light water
reactor
• Application with modification
Modification is required to be applicable to the design
• New criteria
• Not applicable
33 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
†The primary focus is on heavy liquid metals, more specifically lead, as reactor coolant, but
other lead-based coolant options (especially lead bismuth eutectic, LBE) are also considered.
Where considerations for LBE coolant differ from those of lead, additional commentary is
included as footnote in the LFR SDC.
Titolo della presentazione - Luogo e data
LFR safety aspects
GIF safety goals
• Generation-IV systems shall excel in safety and reliability:
• will have a very low likelihood and degree of reactor core
damage
• will eliminate the need for off-site emergency response
34 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
LFR safety aspects
GIF safety approach
Based on a combination of the following
principles:
• Defence in Depth and its further
improvements (as a fundamental principle)
• Risk informed approach
• Simulation, prototyping and demonstration
• Utilization of passive safety features
• Prevention of cliff edge effects (in severe
accidents)
• Provision against internal & external
hazards
• Considerations of non-radiological and
chemical risks
35 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Core and Fuel Characteristics
36 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• Fuel assemblies are operated in a fast neutron spectrum under the
conditions of high power density, high burnup, and high temperature
of lead.
• The reactor core is not in the most reactive configuration under
normal operating conditions and it is possible to have a positive void
reactivity in the central area of the reactor core the reactor core
should be designed to prevent excessive reactivity insertion.
• The high boiling point of the lead coolant (1749ºC) makes coolant
boiling highly unlikely, but gas/void might appear in the core or its
vicinity, for example as a consequence of a fission gas release from
ruptured fuel pins or due to steam generator tube leakages or
ruptures.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Physical and Chemical Properties of Lead Coolant
37 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• The low partial vapor pressure (correlated to the available margin to
boiling) allows operating the system close to atmospheric pressure.
• The high density generates buoyancy forces which have to be
considered in design of in-vessel structures; challenges to the main
vessel and reactor components in terms of seismic response need
to be specifically addressed.
• The freezing temperature of lead is 327ºC coolant solidification
needs to be considered and prevented.
• The high volumetric heat capacity (ca. 1.54 J/cm3/K for lead),
combined with the inventory of the coolant present in the primary
circuit, provides high thermal inertia.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Physical and Chemical Properties of Lead Coolant
38 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• The large volumetric expansion coefficient (1.2∙10-4 1/K for lead) and
the possibility to operate in a large range of temperatures, without
boiling or excessive material corrosion/erosion, enhance the
possibility of core cooling by natural convection.
• Due to opacity, in an LFR it is preferable that each component inside
the reactor vessel is designed as removable ensuring adequate in-
service inspection (ISI) and maintenance.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Induced radioactivity, coolant activity, retention of volatile products
39 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• Pure lead is not exempt from the polonium formation, however, the
rate of polonium production is very small and the volatility of
polonium is lowered, typically by several orders of magnitude with
respect to LBE, through strong chemical reaction with the lead
coolant (e.g., via the formation of lead-polonide).
• Only a very small fraction of polonium, depending on lead
temperature, is expected to be vaporized into the cover gas system.
• Lead provides a relatively good capacity for retention of important
fission products as well as activation products. E.g., volatilized
fractions for 137Cs, 90Sr, and 131I at 700ºC are 1.1∙10-6, 5.1∙10-14 and
3.7∙10-6, respectively.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Chemical interactions
40 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• The relative chemical inertness of lead with water or air provides
conditions for the elimination of the intermediate circuit in LFRs.
• However, in case of steam generator tube rupture (SGTR) event,
water interaction with lead needs to be considered and adequately
prevented and/or mitigated.
• Specifically, over-pressurization of the primary circuit, sloshing and
steam/water entrainment, which might result in a positive reactivity
insertion as well as formation of solid PbO possibly causing flow
blockages, need to be considered.
• Fuel-coolant interactions have shown to exhibit low energetics,
favouring safety. Further investigations are however ongoing to
better assess the phenomenology.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Structural material compatibility with coolant/environment
41 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• Flowing heavy liquid metals are corrosive and can induce or
accelerate a material failure under a static loading (brittle fracture) or
under a time-dependent loading (fatigue and creep).
• LFRs are consequently designed to operate at a low temperature
range (400-520ºC to maintain the fuel cladding temperature below
ca. 570ºC) maintaining a controlled concentration of dissolved
oxygen in the primary coolant.
• The concentration of dissolved oxygen has to be high enough to
support the formation of protective layers on surfaces of structures,
while at the same time low enough to prevent the formation of large
amounts of PbO precipitation.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Structural material compatibility with coolant/environment
42 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• For traditional materials at temperatures above 500ºC, the corrosion
protection through the oxide barrier seems to fail and the application
of corrosion surface coatings (for example Al2O3, SiO2 or aluminum
alloy) or the use of innovative steels with addition of silicon or
aluminum is therefore considered.
• Fuel cladding, upper core regions and primary coolant inlet regions
to the heat exchanger are particularly sensitive to corrosion, because
temperatures are the highest.
• The integrity of the protective layer needs to be ensured during all
plant operating conditions, including long-term transients, in order to
ensure the integrity of the components.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Structural material compatibility with coolant/environment
43 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• As an LFR operates at a relatively high temperature compared to an
LWR and in high fast neutron fluence conditions, due consideration
of creep and radiation effects on fuel and structural materials is also
necessary.
• Because of the good thermal conductivity of lead and the relatively
large temperature differences between inlet and outlet of the reactor
core, thermal striping needs to be considered and must be
accounted for in the design to prevent structural damage.
Titolo della presentazione - Luogo e data
LFR safety-relevant characteristics considered
Operation under low pressure condition
44 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• As an LFR is operated in low pressure conditions, close to
atmospheric pressure and temperatures well below the boiling point
(1749ºC), coolant leakage or pipe break does not lead to the type of
loss of coolant accident experienced in an LWR with
depressurization, coolant boiling and the loss of cooling capability:
• an emergency core cooling systems for coolant injection
under high and low pressure conditions, as used in the LWR,
is therefore not necessary in an LFR;
• the only requirements for LFR core cooling are the
maintenance of the lead coolant level above the inlet of the
Steam Generator (SG) or Decay Heat Removal (DHR) heat
exchangers, to provide a heat removal flow path.
Titolo della presentazione - Luogo e data
Lessons learned from Fukushima Daiichi accident
LFR advantages
The LFR is particularly suited, thanks to
the inherent characteristics of the
coolant and the extended use of
passive safety features, to face
Fukushima like events
45 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Lessons learned from Fukushima Daiichi accident
Additional provisions to improve plant response to extreme events
46 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Extreme earthquake
LFR concepts are designed to withstand the Design Basis Earthquake,
with margins. Due to the high density of lead, the response of a plant to
extreme earthquakes needs to be however carefully considered, incl.
sloshing effects and need for their damping. 2D seismic isolators under
the primary building (to reduce loads caused by horizontal oscillations),
or design features of the reactor vessel, can address this issue.
Titolo della presentazione - Luogo e data
Lessons learned from Fukushima Daiichi accident
Additional provisions to improve plant response to extreme events
47 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Extreme flooding
LFR concepts, notably the DHR systems, shall be protected from the
consequences of a flooding. This is both from a mechanical point of
view, to prevent the component damage, and from a functional point of
view since their actuation is to be accomplished by protected energy
devices. However, the relative chemical inertness of lead in contact
with water permits an extensive use of water cooling.
Titolo della presentazione - Luogo e data
Lessons learned from Fukushima Daiichi accident
Additional provisions to improve plant response to extreme events
48 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Total loss of an electric power supply and/or heat sink(s)
Intrinsic characteristics of lead cooled reactors provide an increased
robustness of the plant in response to the total loss of electric power
supply and/or heat sink(s) because:
• the liquid lead can maintain an adequate degree of natural
convection to accomplish decay heat removal function completely
passively;
• the heat sink is usually diverse: water or air.
In case of loss of a normal heat sink, fully passive DHR systems are
able to fulfil the safety function.
Titolo della presentazione - Luogo e data
Lessons learned from Fukushima Daiichi accident
Additional provisions to improve plant response to extreme events
49 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Total loss of an electric power supply and/or heat sink(s)
In the very unlikely event of a Fukushima-like scenario leading to the
loss of all heat sinks (both secondary and dedicated DHR systems),
heat can be possibly extracted by injecting water into the reactor cavity
between the reactor and safety vessels (based on the specific design
features) and/or the decay heat can be removed by a dedicated heat
removal system that cools the concrete of reactor cavity walls.
Lead provides a relatively good capacity for retention of important
volatile fission products as well as activation products, e.g., Cs and I.
Titolo della presentazione - Luogo e data
The GIF LFR SDC
outlook
50 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
• First draft elaborated by GIF LFR pSSC in 2014-2015
• Eighty-four (84) reference design criteria identified for
GIF LFRs
• Draft submitted to GIF-RSWG for review in December
2015
• Comments received by GIF-RSWG and by IRSN and
partners of the Euratom collaborative project “ARCADIA”
• Presently under review for final issue
• Further steps include the development of detailed Safety
Design Guidelines for selected topics
Titolo della presentazione - Luogo e data
The GIF LFR SDC
Applicability Number
As is 70
With interpretation 6
With modification 6
New requirement 2
Not applicable 0
51 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Summary of development process
Titolo della presentazione - Luogo e data
LFR safety issues
addressed:
Criterion 42bis: Plant system performance
The overall plant system shall be designed considering the specific characteristics of the reactor coolant and, in general, of the fast reactor system. This includes coolant inherent characteristics, such as its freezing and boiling point, volumetric heat capacity, degree of opacity, chemical reactivity in contact with air and water, as well as corrosion and erosion effects, and the reactor neutronic characteristics, such as its susceptibility to reactivity variations due to coolant heat-up and voiding as well as due to the loss of core geometry. Coolant-specific requirements, including the impurity and toxicity limits, need to be considered in the design as well.
• Corrosion/erosion, opacity
and high coolant freezing
point of lead (327ºC)
• Ruptures of steam
generator tubes might lead
to over-pressurization of the
primary side, sloshing and
steam/water entrainment
resulting in a positive
reactivity insertion
• Loss of core geometry (core
compaction) might lead to a
positive reactivity insertion
and power increase
52 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
LFR safety issues
addressed:
Criterion 47: Design of reactor coolant systems
6.15bis: The components of the reactor coolant systems shall be designed with due account taken of creep properties, thermal fatigue, fast neutron fluence, coolant-induced environmental effects, and other ageing effects, as well as its compatibility with lead, and with thermal stress and dynamic load on structures used under low pressure and high temperature conditions.
• Operation at relatively high
temperatures compared to
an LWR and in high fast
neutron fluence conditions
• Molten lead is corrosive and
oxidizes without oxygen
concentration control
• Metallic impurities produced
by corrosion can be
transported in the primary
system and form blockages
• Molten lead might erode
structural materials
• Large quantities of primary
coolant in pool LFRs may
lead to complex flow
patterns and interactions
with structures
53 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
LFR safety issues
addressed:
Criterion 76bis: Coolant Heating Systems
Heating systems shall be provided for primary coolant as necessary to prevent loss of primary coolant circulation by coolant freezing. These heating systems and their controls shall be appropriately designed to assure that the temperature distribution and rate of change of temperature are maintained within the limits.
• High freezing point (327ºC)
with a potential for coolant
solidification
• Mechanical stresses might
be exerted on structures
during unfreezing if a
proper melting sequence is
not applied
54 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
LFR safety issues
addressed:
Criterion 20: Design extension conditions
5.31. The design shall be such that design extension conditions that could lead to significant radioactive releases are practically eliminated. Since a fast reactor core is not in its most reactive configuration under normal operating conditions, the following design features for prevention and mitigation of severe accidents in postulated design extension conditions shall be considered:
a) Additional reactor shutdown measures against failure of active reactor shutdown systems,
b) Mitigation provision to avoid re-criticality leading to large energy release during a core degradation progression,
c) Means for decay heat removal of a degraded core, and
d) Containment function capability to withstand the thermal and mechanical loads generated by severe accident conditions.
• LFR reactor core is not in
the most reactive
configuration; it is possible
to have a positive void
reactivity in the central area
of the reactor core
• Corrosive properties of
molten lead could challenge
confinement barriers
55 LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
Titolo della presentazione - Luogo e data
Giacomo Grasso
giacomo.grasso@enea.it
LFR Safety Design Criteria: Overview and status – IAEA HQ, Vienna, Sept. 4-8, 2017
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