Checkability of the digital components in safety-critical systems: Problems and solutions

Particularities of on-line testing for digital components in safety-critical Instrumentation and Control systems (I&CS) are analyzed. A problem of on-line testing associated with insufficient checkability of the digital components in safety-critical I&CS (reactor trip system) is considered. A method of checkability estimation is offered. An example of comparator checkability assessment is shown. An approach to increase checkability of the digital components is proposed.