2. Severe Accident Qualification EPR™ OL3
Dirk C. HOPP
Expert and Senior Advisor / PTCQA
Clearwater Beach to 14

3. Severe Accidents Qualification
Severe Accidents (SA) are considered by Design for EPR™
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4. Severe Accidents Qualification General Qualification Approach (1/2)
Multiple failures in plant Safety Systems could lead to their complete loss. This loss of function leads to
Beyond design basis accidents
Significant core degradation
However, EPR™ handles the SA identical/similar to the Design Basis Events like Loss of Coolant Accidents (LOCA)
Comparison of Environmental Accident Conditions of SA and LOCA
Quite similar P&T profiles
Higher globally irradiation for SA, extremely high at concerned areas
Higher temperatures at concerned areas
Specific requirements are defined for respective EPR™ Projects
Safety Analysis Report
Technical Specifications
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5. Severe Accidents Qualification General Qualification Approach (2/2)
In general, the equipment needed for the mitigation and/or monitoring of an SA can be divided into two groups:
Equipment which is directly subjected to the SA conditions (inside containment)
Equipment which has to tolerate consequences of the SA (outside containment)
Mission times for SA in the EPR™ are defined as follows:
Midterm (MT): Required function up to 100 hours after start of the SA
Long term (LT): Required function up to one year after start of the SA
Individual Mission Times may be defined (e.g. 24 h for Intermediate Excore Neutron Detectors)
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6. Severe Accidents Qualification Parts of the Qualification (1/4)
Design Tests as Part of the Research and Development Process
Validation of required Design
Testing to determine design limits
May be material tests (e.g. long-term endurance test)
Type Tests according to Product Standards
Based on the design data and/or on values required by Product Standards
May be performed on different sets of specimens
Testing according to Product Standards (if applicable)
Testing of the behavior for transportation
Electrical functions and signal stabilities (determination of tolerances)
Mechanical integrity (resistance to pressure, induced vibration loads)
Material tests (endurance test)
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7. Severe Accidents Qualification Parts of the Qualification (2/4)
Type Tests in accordance to Nuclear Standards
Functional tests at postulated conditions
Qualified life tests
SA simulation tests, including simulation of the Post Accident Phase
Qualified Life tests
Have to be performed on the same specimens in a defined sequence representing the consequences of the loads in the life cycle of the equipment
Definition of Design Life is necessary (e.g. 60 / 30 / 15 years)
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8. Severe Accidents Qualification Parts of the Qualification (3/4)
Pre-Conditioning
Loads due to transportation
Thermal ageing
Radiation ageing
Mechanical ageing
Load cycles representing start-up and shut-down
Loads due to pressurization cycles (e.g. containment integrity tests)
Vibration ageing (e.g. location of sensors/valves on high energy pipes)
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9. Severe Accidents Qualification Parts of the Qualification (4/4)
Severe Accident Simulation Test
Accident irradiation 1
(e.g. 800 kGy for SA Midterm 100 h; recommended dose rate is the average for the duration = 8 kGy/h)
SA simulation (P&T profile) test performed in real time (for Midterm 100 h)
Accident irradiation 2
(e.g kGy total SA dose for the rest of the year; recommended dose rate is = 5 kGy/h)
Post-SA test: Accelerated test with a weighted average temperature (based on activation energy value of materials); chemical spray (2500 ppm of boric acid); recommended duration 8-12 weeks (corrosion effects)
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10. Severe Accidents Qualification Summary
Severe Accidents are considered by Design for EPR™
EPR™ handles Severe Accidents identical/similar to Design Basis Events
Qualification Steps depends on the Mission Times
In general Design Tests and Type Tests according to Product Standards are preconditions before starting Nuclear Qualification
Severe Accidents Qualifications consists of almost “usual” LOCA qualification methods
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12. End of presentation Severe Accident Qualification
Dirk C. HOPP
Expert and Senior Advisor / PTCQA
Clearwater Beach to 14