Assessing the Impact of Common Cause Failures on Site Risk within Level 1 Multi-Unit PSA

Table 7

Summary of the most significant scenarios in the multi-unit LOOP followed by SBO event.

No.	Value	Event	Description
1	0.00014	49.43%
	1.00E − 02	%IE_LOOP2	Unit 1 LOOP initiating event
	1.40E − 02	2-EPDGS-AAC	No power from AACDG by AACDG failure
	1.00E + 00	#1UNIT	Tag event for core damage in 1 unit
	1.00E + 00	#LOOP_UNIT_2-5!	Unit 2 LOOP sequence 5
2	0.00014	49.43%
	1.00E − 02	%IE_LOOP1	Unit 1 LOOP initiating event
	1.40E − 02	EPDGS-AAC	No power from AACDG by AACDG failure
	1.00E + 00	#2UNITS	Tag event for core damage in 2 units
	1.00E + 00	#LOOP_UNIT_1-5!	Unit 1 LOOP sequence 5
3	1.96E − 06	0.69%
	1.00E − 02	%IE_LOOP1	Unit 2 LOOP initiating event
	1.40E − 02	EPDGS-DGA	DG A fails to start and load
	1.40E − 02	2-EPDGS-DGB	DG B fails to start and load
	1.00E + 00	#2UNITS	Tag event for core damage in 2 Units
	1.00E + 00	#LOOP_UNIT_1-5!	Unit 1 LOOP sequence 5
4	3.69E − 07	0.13%
	1.00E − 02	%IE_LOOP2	LOOP initiating event
	2.63E − 03	2-EPDGM-DGC	DG C unavailable due to maintenance
	1.40E − 02	2-EPDGS-DGD	DG D fails to start and load
	1.00E + 00	#1UNIT	Tag event for core damage in 1 unit
	1.00E + 00	#LOOP_UNIT_2-5!	Unit 2 LOOP sequence 5
5	3.69E − 07	0.13%
	1.00E − 02	%IE_LOOP2	Unit 1 LOOP initiating event
	1.40E − 02	2-EPDGS-DGC	DG C fails to start and load
	2.63E − 03	2-EPDGM-DGD	DG D unavailable due to maintenance
	1.00E + 00	#2UNITS	Tag event for core damage in 2 units
	1.00E + 00	#LOOP_UNIT_2-5!	Unit 2 LOOP sequence 5
6	9.21E − 08	0.03%
	1.00E − 02	%IE_LOOP2	Unit 2 LOOP initiating event
	1.40E − 02	2-EPDGS-DGC	DGs A and B fail to start and load due to CCF
	6.58E − 04	2-EPDGW-DGCD	DGs C and D fail to start and load due to CCF
	1.00E + 00	#1UNITS	Tag event for core damage in 1 unit
	1.00E + 00	#LOOP_UNIT_2-5!	Unit 1 LOOP sequence 5
7	9.21E − 08	0.03%
	1.00E − 02	%IE_LOOPD	Unit 1 LOOP initiating event
	6.58E − 04	EPDGW-DGAB	DGs C and D fail to start and load due to CCF
	1.40E − 02	EPDGS-DGD	DG D fails to start and load
	1.00E + 00	#1UNIT	Tag event for core damage in 1 unit
	1.00E + 00	#LOOP_UNIT_1-5!	Unit 1 LOOP sequence 5
8	6.93E − 08	0.02%
	1.00E − 02	%IE_LOOP2	Unit 2 LOOP initiating event
	2.63E − 03	2-EPDGM-DGD	DG D unavailable due to maintenance
	2.63E − 03	2-EPDGM-DGC	DG D unavailable due to maintenance
	1.00E + 00	#2UNITS	Tag event for core damage in 2 units
9	3.87E − 08	0.01%
	1.00E − 02	%IE_LOOP1	Unit 2 LOOP initiating event
	3.87E − 06	EPDGW-CCF-DG-AB-AAC	All DGs (A and B) fail to start due to inter-unit CCF
	1.00E + 00	#1UNIT	Tag event for core damage in 1 unit
	1.00E + 00	#LOOP_UNIT_1-5!	Unit 1 LOOP sequence 5
10	3.87E − 08	0.01%
	1.00E − 02	%IE_LOOP2	Unit 2 LOOP initiating event
	3.87E − 06	2-EPDGW-CCF-DG-CD-AAC	All DGs (C and D) fail to start due to inter-unit CCF
	1.00E + 00	#1UNIT	Tag event for core damage in 1 unit
	1.00E + 00	#LOOP_UNIT_2-5!	Unit 2 LOOP sequence 5