Classification according to DS367 and example

1. Classification according to DS367 and example 2011 6.6 JNES

2. Table of contents • Outline of DS367 methodology 1-1. Main steps in classifying SSCs 1-2. Relationship between type of Safety Function and SafetyCategories for Plant Specific Safety Functions 1-3. Assignment of SSC’s to safety classes 1-4. Reactor Type Safety Function For Light Water Reactors • Classification Example of ABWR LOCA according to DS367 • ABWRLOCA Events

3. 1-1 Main steps in classifying SSCs The approach to safety classification involves categorization of safety functions followed by classification of the SSCs. Review and definition of PIEs Identification of reactor type specific, then plant specific safety functions: · preventive safety functions · mitigatory safety functions Categorization of safety functions Identification of SSCs or groups of SSCs to perform safety functions Assignment of SSCs that perform safety functions to a safety class Identification of engineering design rules for the design, manufacturing, qualification, installation, commissioning and operation for classified SSCs

4. 1-2 RELATIONSHIP BETWEEN TYPE OF SAFETY FUNCTION AND SAFETYCATEGORIES FOR PLANT SPECIFIC SAFETY FUNCTIONS • - 3 Safety Category (according to Risk) supplemented by a fourth category (DEC) • Level A : establish a controlled state following DBA • Level B : maintain a safe shutdown state after a controoled state following DBA

5. 1-3 Assignment of SSC’s to safetyclasses Preliminary assignment of SSCs to Safety Classes Final assignment of SSCs to Safety Classes Plant Specific Safety Function Safety Category 1 (Highest Safety Category) SSCs (SFG – main & supporting SSCs) assigned to Preliminary Safety Class 1 (Highest Safety Class) SSCs assigned to the Safety Class 1 (Highest Safety Class) Plant Specific Safety Function Safety Category 2 SSCs (SFG – main & supporting SSCs) assigned to Preliminary Safety Class 2 SSCs assigned to the Safety Class 2 Plant Specific Safety Function Safety Category 3 SSCs (SFG – main & supporting SSCs) assigned to Preliminary Safety Class 3 SSCs assigned to the Safety Class 3 Plant Specific Safety Function Safety Category 4 SSCs Classed as Not Important to Safety SSCs Classed as Not Important to Safety • Not directly support SF • Already be In operation • Less likely to be used (fulfilled by more than one SSC)

6. 1-4 Reactor Type Safety Function For Light Water Reactors F1: control of reactivity; F2: removal of heat from the core; F3: confinement of radioactive material.

7. 2-1.1 Classification Example of ABWR LOCA according to DS367 (1/3) [1] The plant specific safety function are taken from the list of safety function in Annex I, Table II-I of DS367. [2] Design Requirements are basically same as DS 367, Appendix III, Table 2,3 and 4 for Safety Class 1,2,3 and 4 SSCs.

8. 2-1.2 Classification Example of ABWR LOCA according to DS367 (2/3) [1] The plant specific safety function are taken from the list of safety function in Annex I, Table II-I of DS367. [2] Design Requirements are basically same as DS 367, Appendix III, Table 2,3 and 4 for Safety Class 1,2,3 and 4 SSCs.

9. 2-1.3 Classification Example of ABWR LOCA according to DS367 (3/3) [1] The plant specific safety function are taken from the list of safety function in Annex I, Table II-I of DS367. [2] Design Requirements are basically same as DS 367, Appendix III, Table 2,3 and 4 for Safety Class 1,2,3 and 4 SSCs. 9

10. abbreviation PIE : Postulated initiating event SSC : Structures, Systems and Components in Nuclear Power Plants DEC : Design Extension Condition DBA : Design Basis Accident AOO : Anticipated Operational Occurrences RCIC : Reactor Core Isolation Cooling System HPCF : High Pressure Core Flooder System LPFL : Low Pressure Flooder System ADS : Automatic Depressurization System DiD : Defense in Depth

11. ADS BREAK OUTFLOW ECCS 3.ABWRLOCAの説明図 Maintain core cooling under accident conditions HPCF Line Break event Redundancy : 2 sets of identical system Independent : electric power, division • ポーランドで説明したもの RPV Main Steam Line Feed Water Line LPFL LPFL HPCF HPCF LPFL RCIC RCCV Condensate Storage Pump 11

12. Scenario of large break LOCA of ABWR Double ended guillotine break of HPCF line Two phase critical break flow Pressure decrease, inventory decrease, core flow decrease SCRAM by core flow decrease signal MSIV closure (Level 1.5) RCIC operation (Level 1.5) ADS (Level 1 + 30sec) LPLF operation (Level 1) BT occurs but water level of core is kept to be full Long term core cooing is available by only 1-ECCS February 7-9, 2011, Poland 12

13. Safety Function in Relation to the connection of Defence in Depth (DiD) Challenges/mechanisms affecting the performance of the safety functions Provisions for Level 1 of DiD Objective : Prevention of abnormal operation and failure Level 1 Success Normal Operation Initiating vent Objective : Detection of failure and control of Abnormal operation Level 2 Provisions for Level 2 of DiD Success Observance of the acceptance criteria established for AOO (return to normal operation) DBA Objective : Control of DBA Level 3 Provisions for Level 3 of DiD Success Observance of the acceptance criteria established for DBA DEC Objective : Control of consequences in DECs Level 4 Provisions for Level 4 of DiD Success Limiting core damage and confinement preservation Significant Off-site Radioactive Release Objective : Mitigation of radiological consequenses of significant releases of radioactive material Level 5 Provisions for Level 5 of DiD

14. LOCA : Core inlet flow rate 1.0 0.5 Core inlet flow rate (-) Flow decrease due to RIP coast down 0 0 10 time (s) February 7-9, 2011, Poland 14

15. LOCA : Water level RCIC MSIV close 15 LPFL 10 Top of active fuel Bottom of shroud head ADS open Water level (in-shroud) (m) 5 Bottom of active fuel 0 500 time (s) February 7-9, 2011, Poland 15

16. LOCA : Cladding temperature 1200 PCT is about 550oC Cladding temperature (oC) 600 Boiling transition (BT) occurs and heat-up starts 0 500 time (s) February 7-9, 2011, Poland 16