Investigating the implementation of the safety-diagnosability principle to support defence-in-depth in the nuclear industry: A Fukushima Daiichi accident case study

•The safety-diagnosability principle (SDP) is already applied for oil and gas applications.•The SDP is an attractive principle placing focus on information on barrier performance.•We investigate the principle for use also in nuclear applications.•The 2011 Fukushima Daiichi nuclear accident is used as basis for the discussions.•For nuclear applications, it should add value in combination with the defence-in depth principle.