Failure Mode and Effect Analysis for a Programmable Logic Controller-Based Control Unit for a Miniature Neutron Source Reactor Pneumatic Transfer System

Table 2

Likelihood of occurrence.

Likelihood of occurrence	Definition guidance	Criteria: possible failure rate (%)	Rating
Certain	Absolute certainty	100	10
High	Very likely to occur	65–99	9
			8
Medium	Likely/possible	35–65	7
			6
Low	Unlikely to occur	5–35	5
			4
Remote	Very unlikely to occur	1–5	3
			2
None	Will not occur	0	1