Science and Technology of Nuclear Installations

Research Article

Reliability Assessment for a Safety-Related Digital Reactor Protection System Using Event-Tree/Fault-Tree (ET/FT) Method

Table 5

Importance and sensitivity of the selected BEs on system risk.


Number	Basic event	Probability	FV	RDF	RIF	Sens

1	ACM-1 UU-CCF-ALL	8.04 × 10⁻⁸	8.99 × 10⁻²	1.10	1.12 × 10⁶	1.97
2	ACM-2 UU-CCF-ALL	8.04 × 10⁻⁸	8.99 × 10⁻²	1.10	1.12 × 10⁶	1.97
3	ACM-3 UU-CCF-ALL	8.04 × 10⁻⁸	8.99 × 10⁻²	1.10	1.12 × 10⁶	1.97
4	ACM-1 UU-CCF-123	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
5	ACM-1 UU-CCF-124	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
6	ACM-1 UU-CCF-134	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
7	ACM-1 UU-CCF-234	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
8	ACM-2 UU-CCF-123	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
9	ACM-2 UU-CCF-124	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
10	ACM-2 UU-CCF-134	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
11	ACM-2 UU-CCF-234	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
12	ACM-3 UU-CCF-123	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
13	ACM-3 UU-CCF-124	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
14	ACM-3 UU-CCF-134	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
15	ACM-3 UU-CCF-234	5.44 × 10⁻⁸	6.08 × 10⁻²	1.06	1.12 × 10⁶	1.64
16	1 ACM-1 UU	2.66 × 10⁻⁵	2.27 × 10⁻⁵	1.00	1.85	1.00
17	2 ACM-1 UU	2.66 × 10⁻⁵	2.27 × 10⁻⁵	1.00	1.85	1.00
18	3 ACM-1 UU	2.66 × 10⁻⁵	2.27 × 10⁻⁵	1.00	1.85	1.00
19	4 ACM-1 UU	2.66 × 10⁻⁵	2.27 × 10⁻⁵	1.00	1.85	1.00

Note. ACM-1, 2, 3 represent ACMs for three sensor signals. UU-CCF-ALL represents common cause undetected unsafe failure of four identical modules of all channels. UU-CCF-XYZ (X, Y, Z = 1, 2, 3, 4) represents common cause undetected unsafe failure of four identical modules of X, Y, and Z channels, where 1, 2, 3, and 4 represent IP, IIP, IIIP, and IVP respectively. X (X = 1, 2, 3, 4) represents channels.