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Risk-informed Design Optimization for the China
LEAd-based Research Reactor
Presented by Jin Wang
Contributed by FDS Team
Key Laboratory of Neutronics and Radiation Safety
Institute of Nuclear Energy Safety Technology (INEST)
Chinese Academy of Sciences
www.fds.org.cn
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NURIS · Vienna ·April 2015
Contents
China LEAd-based Research Reactor
Risk-informed Design Optimization
Conclusion
NPPs in China
 Total 14 operating NPPs in Chinese mainland, about 27 NPPs
under construction.
 Development of nuclear energy influenced by Fukushima
Daiichi Accident but maybe not stopped.
 14 operating NPPs include various reactor types, for example,
PWR, PHWR, VVER, etc.
Strategy and Research
 Government has set up the developing strategy
PWR (Pressurized Water Reactor) → FBR (Fast Breeder
Reactor) → FR (Fusion Reactor)
 Advanced hybrid nuclear energy system are now
studied, including Fusion Driven Sub-critical System and
Accelerator Driven Sub-critical System.
ADS Program Since 2011 in China
 CAS has launched the ADS Engineering Project in 2011, and plan to construct the demo
ADS transmutation system ~ 2030s through 3 stages.
 China LEAd-based Reactor (CLEAR) is selected as the reference reactor for ADS
project and for Lead cooled Fast Reactor (LFR) technology development.
~2020s ADS Experimental Facility
Reactor：China Lead-based Experimental
Reactor CLEAR-II (~100MW)
~2010s ADS Research Facility
Reactor：China Lead-based
Research Reactor CLEAR-I (~10MW)
~2030s ADS Demonstration Facility
Reactor：China Lead-based Demonstration
Reactor CLEAR-III (~1000MW)
RFQ
Accelerate element
High current ion source
Superconducting cavity
CLEAR-I Main Design Parameters
Parameter
Thermal power (MW)
Core
Cooling
System
Material
Activity height (m)
Fuel (enrichment)
Primary coolant
Inlet/Outlet temperature (℃)
Coolant driven type
Heat exchanger
Primary pump
Cladding
Structure
Values
10
0.8
UO2(19.75%)
LBE
300/385
Forced circulation
4
2
15-15Ti
316L
Overall View of CLEAR-I Structure
Reactor vessel air
cooling system
Refueling and control
rod driven system
Vessel
Structure support
Cover
Core
Core shroud
Safety Characteristics and Requirements
 Inherent Safety
 Lead-based coolant safety advantages: Chemical inertial, low
operation pressure, high boiling temperature, etc.
 Large thermal inertia: Large coolant inventory to power ratio (~700t /
10MW)
 Passive safety: Passive decay heat removal by Reactor Vessel Air
Cooling System (RVACS)
 Negative reactivity feedback
 Safety Goals
 Core Damage Frequency: 1.0E-6/ry for internal events
 Radioactive Material Release Limit: Whole body dose < 0.25 Sv for
2 hours at Exclusion Area Boundary (EAB).
Contents
China LEAd-based Research Reactor
Risk-informed Design Optimization
Conclusion
PSA in China
 PSA is mandatory by Chinese regulatory authority,
National Nuclear Safety Administration, during the
application procedure for a license.
 Now all the operating NPPs have finished their level-1
PSA (full power mode and internal hazards included).
 Level-1shutdown and low power, Level-2 and seismic
PSA are undergoing.
 Some applications of PSA have also been carried out by
NPPs, for example, Risk Monitors, RCM (Reliability
Centered Maintenance), optimization of Technical
Specification.
Risk-informed Regulation
Meet with the requirements of
nuclear regulation authority
Ensure defense in depth
Improve plant performance
Risk Informed
Regulation
Maintain safety margin
Keep incremental risk under
safety goal
RIR combines PSA and DSA methodologies together.
Initiating Events (IE)
 Selection Methods
 Master Logic Diagram (MLD)
 Initiating events list of other lead-based reactors
 Engineering evaluation, e.g. FMECA
 Operation experiences
Label
IE-T
Name
General Transient
Frequency (/ry)
1.10E+00
IE-L1
Loss of Coolant in Primary Cooling System
3.35E-04
IE-MHTR
Tube Rupture of Main Heat Exchanger
1.00E-03
IE-L2
Loss of Coolant in Secondary Cooling System 1.00E-02
IE-ST
Transient in Secondary Loop
5.26E-02
IE-LOOP
Loss of Offsite Power
4.60E-02
IE-CF
Cooling Fault of Core Assembly
4.00E-08
Event Trees and Fault Trees
 Analysis Method
 Standard small event tree/ large fault tree
 Fault Tree Analysis Scope
 Reactor Shutdown System
 Primary and Secondary Cooling System
 Reactor Vessel Air Cooling System
 Other Safety Related Systems
 Summary of Fault Tree Size
 Reactor Shutdown System: ~500 gates and basic events
 Secondary Cooling System: ~150 gates and basic events
 RVACS: ~200 gates and basic events
Reliability Data of CLEAR-I
 General Data Sources
 IAEA-TECDOC-478
 NUREG/CR-6928
 Other fast reactors
 Engineering judgment
 Specific Data Collection
 Experimental facilities
 Equipment reliability test
 Bayesian analysis
Reliability and Probabilistic Safety Assessment Program (RiskA)
Risk Monitor for Nuclear Power Plant (RiskAngel/TQRM)
 Qinshan nuclear power plant Risk Monitor
 First safety analysis software applied in nuclear power plants with fully intellectual
property right in China
Summary of Preliminary Quantification Analysis
 Reliability of Accident Mitigation System
 Probability of shutdown system failure: 1.4E-10
 Secondary cooling system failure: 1.2E-04
 RVACS failure including passive function fault: 6.0E-05
 Distribution of Core Damage Frequency (CDF) for IE
CDF for internal events: 2.08E-07/ry
Technical Insights
 The risk of operation of CLEAR-I is very low, it satisfy the
safety target: the order of 10E-06/ry.
 General transient play important role in core damage.
 CDF of general transient: 7.39E-08/ry (35.5%)
 Simultaneity failure of normal heat transfer system and
RVACS contribute most CDF ratio.
 The failure of passive function of RVACS plays very
important role in overall risk reduction worth.
 CDF will increase 60 times if passive function fault
occurred in one of the four alignments of RVACS.
Risk-informed Design Cases
 One important application of PSA in CLEAR-I design is
the identification of some situation that could increase
the core damage risk or system unavailability, and
providing correction or optimization actions.
 Two alternative conceptual design of CLEAR-I for risk
reduction purpose have been evaluated by PSA.
 If the heat removal function of pressurizer in secondary
cooling was taken into account in Emergency Operation
Procedure (EOP). It will reduce 18% of total CDF.
 If another safety class pump was installed in secondary
circulation, it will reduce 10% of total CDF.
Contents
China LEAd-based Research Reactor
Risk-informed Design Optimization
Conclusion
Conclusion
 Conceptual design of CLEAR-I has been finished, it has
inherent safety characteristics and rigorous safety goals.
 Preliminary PSA was performed, standard small event
tree/ large fault tree method was used in PSA model
development.
 Quantitative analysis was performed using RiskA
software, and the result indicates that the overall risk of
CLEAR-I is considerably low.
 Risk-informed design method has been applied in design
process of CLEAR-I since the beginning of conceptual
design.
Website: www.fds.org.cn
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