Regional Basic Professional Training Course in Korea

Regional Basic Professional Training Course (BPTC) on Nuclear Safety
Human Reliability data.
9.3.2. Frequency of initiating Events
9.3.2.1. Quantification methods
In so far as possible, priority should be given to experience feedback in quantification.
For events of observable frequency, the values used are specific ones derived from
operating experience (e.g., loss of feedwater plant, loss of off-site electrical power
supplies, spurious safety injections, etc.).
For less frequent events, the values can be derived from worldwide feedback
experience (steam generator tube rupture, small primary breaks). Generic values
can be combined with specific values by using Bayesian methods.
For extremely rare events, the values can be estimated by expert judgment,
allowance being made in particular for the absence of observation anywhere in the
world and the values used in foreign studies (e.g., large primary and secondary
system breaks).
When the initiating event is the loss of a system, quantification is based on a
reliability study (e.g., electrical power blackout and loss of the CCW system). In
this case, quantification is carried out with the tools used for systems analysis (fault
trees, Markov graphs, etc.)
9.3.2.2. Quantification of sub-initiating events
Division between reactor states: A distinction can be made between sub-initiating
events directly associated with the reactor state and sub-initiating events which can
occur in a number of reactor states. In the second case, the division is made on the
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