22
Key Laboratory of Neutronics and Radiation Safety
Institute of Nuclear Energy Safety Technology (INEST)
Chinese Academy of Sciences
Contributed by FDS Team
www.fds.org.cn
Risk-informed Design Optimization for the China
LEAd-based Research Reactor
Presented by Jin Wang
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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.
~2010s ADS Research Facility
Reactor：China Lead-based
Research Reactor CLEAR-I (~10MW)
~2020s ADS Experimental Facility
Reactor：China Lead-based Experimental
Reactor CLEAR-II (~100MW)
~2030s ADS Demonstration Facility
Reactor：China Lead-based Demonstration
Reactor CLEAR-III (~1000MW)
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.
High current ion source
RFQ
Accelerate element
Superconducting cavity
Parameter Values
Core
Thermal power (MW) 10
Activity height (m)
Fuel (enrichment)
0.8
UO2(19.75%)
Cooling
System
Primary coolant
Inlet/Outlet temperature (℃)
Coolant driven type
Heat exchanger
Primary pump
LBE
300/385
Forced circulation
4
2
Material Cladding
Structure
15-15Ti
316L
CLEAR-I Main Design Parameters
Overall View of CLEAR-I Structure
Reactor vessel air
cooling system
Vessel
Core
Structure support
Refueling and control
rod driven system
Core shroudCover
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).
Safety Characteristics and Requirements
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.
RIR combines PSA and DSA methodologies together.
Risk Informed
Regulation
Keep incremental risk under
safety goalMaintain safety margin
Ensure defense in depth
Meet with the requirements of
nuclear regulation authority
Improve plant performance
Risk-informed Regulation
Initiating Events (IE)
Label Name Frequency (/ry)
IE-T General Transient 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
Selection Methods
Master Logic Diagram (MLD)
Initiating events list of other lead-based reactors
Engineering evaluation, e.g. FMECA
Operation experiences
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.
