NASA Accident Precursor Analysis Handbook, Version 1.0

Catastrophic accidents are usually preceded by precursory events that, although observable, are not recognized as harbingers of a tragedy until after the fact. In the nuclear industry, the Three Mile Island accident was preceded by at least two events portending the potential for severe consequences from an underappreciated causal mechanism. Anomalies whose failure mechanisms were integral to the losses of Space Transportation Systems (STS) Challenger and Columbia had been occurring within the STS fleet prior to those accidents. Both the Rogers Commission Report and the Columbia Accident Investigation Board report found that processes in place at the time did not respond to the prior anomalies in a way that shed light on their true risk implications. This includes the concern that, in the words of the NASA Aerospace Safety Advisory Panel (ASAP), "no process addresses the need to update a hazard analysis when anomalies occur" At a broader level, the ASAP noted in 2007 that NASA "could better gauge the likelihood of losses by developing leading indicators, rather than continue to depend on lagging indicators". These observations suggest a need to revalidate prior assumptions and conclusions of existing safety (and reliability) analyses, as well as to consider the potential for previously unrecognized accident scenarios, when unexpected or otherwise undesired behaviors of the system are observed. This need is also discussed in NASA's system safety handbook, which advocates a view of safety assurance as driving a program to take steps that are necessary to establish and maintain a valid and credible argument for the safety of its missions. It is the premise of this handbook that making cases for safety more experience-based allows NASA to be better informed about the safety performance of its systems, and will ultimately help it to manage safety in a more effective manner. The APA process described in this handbook provides a systematic means of analyzing candidate accident precursors by evaluating anomaly occurrences for their system safety implications and, through both analytical and deliberative methods used to project to other circumstances, identifying those that portend more serious consequences to come if effective corrective action is not taken. APA builds upon existing safety analysis processes currently in practice within NASA, leveraging their results to provide an improved understanding of overall system risk. As such, APA represents an important dimension of safety evaluation; as operational experience is acquired, precursor information is generated such that it can be fed back into system safety analyses to risk-inform safety improvements. Importantly, APA utilizes anomaly data to predict risk whereas standard reliability and PRA approaches utilize failure data which often is limited and rare

Integrated environmental risk assessment of major accidents in the transport of hazardous substances

At present, the environmental risk assessment of major accidents is mainly carried out for stationary risk sources. Only marginal attention is paid to mobile risk sources, while the currently available methodologies require a relevant expertise and time for their application, which is only partially possible in most scenarios. In the present study, an integrated approach to environmental risk assessment in the transport of hazardous substances (iTRANSRISK) was developed. The approach proposed is based on the principle of index-based assessment of leakage scenarios involving toxic and flammable substances during transport, in the context of indexing environmental vulnerability. The key point of the method is the conversion of local-specific data concerning the risk potential of the transported substance, the consequences and the probability of a major accident, and environmental vulnerability assessment into a single entity. The created integral approach is proposed for the needs of carriers of the hazardous substances and the state administration bodies. The proposed approach is determined for the screening risk assessment at the beginning of the process of the planning a suitable transport routes and the results are for information only. An example of the application of the iTRANSRISK integrated approach is demonstrated considering an explosion scenario following a propane tanker leak (18 t) in a forested area, with moderately susceptible soils and no surface water or groundwater affected

Risk-Based Marine Inspection Performance Measures

The objective of this project was to standardize the way risk reduction is measured during marine vessel inspections, based on the deficiencies found on each vessel by the Coast Guard. Over the course of the project, we researched past performance measure models, in addition to working closely with the MISLE database and Coast Guard personnel to determine which factors should be included in our analysis. We then created a prototype model, based on the vessel data from the past decade, for automatically assigning risk-reduction values to various deficiencies