1. Modern Techniques of Accident Investigation C.Jayasuriya, S.V.Karthikeyan and S.E.Kannan IGCARKalpakkam

2. Modern Techniques of Accident Investigation and Analysis: * Core Analytical Techniques * Core Analytical Techniques * Complex Analytical Techniques * Complex Analytical Techniques * Specific Analytical Techniques * Specific Analytical Techniques Core Analytical Techniques: These are more effective when applied to a basic accident with few system failures. These are more effective when applied to a basic accident with few system failures. - Change Analysis - Change Analysis - Barrier Analysis - Barrier Analysis - Event and Causal Factor Analysis and - Event and Causal Factor Analysis and - Root Cause Analysis - Root Cause Analysis

3. Change Analysis: Generally used for single occurrence and focuses on elements that have changed Looks at a problem by analyzing the deviation(s) between what is expected and what actually happened The investigation should focus on the systematic deficiencies that allowed the accident to happen and not just accept the changes identified as the sole cause of it eg. -Through a platform panel that was modified, while working, a tool fell down on a worker who was standing below the platform on his head - Investigation revealed that when the modified platform was put back in position, there was a gap between the panels which was not closed, through which the tool fell down Deficiency: gap between the panels not kept closed, improper supervision

4. Barrier Analysis: ¤ It is a systematic process that can be used to identify physical, administrative and procedural barriers/controls that should administrative and procedural barriers/controls that should have prevented the accidents have prevented the accidents ¤ Barrier is something that separates an affected component ¤ Barrier is something that separates an affected component from undesirable condition / situation from undesirable condition / situation eg. for the previous example, Barrier Analysis indicated: eg. for the previous example, Barrier Analysis indicated: - absence of a physical barrier that did not close the gap - absence of a physical barrier that did not close the gap between the panels and between the panels and - lack of administrative and procedural barrier/control in - lack of administrative and procedural barrier/control in not checking whether the gap was closed or not not checking whether the gap was closed or not ¤ The basic principle is that there is unwanted flow of energy ¤ The basic principle is that there is unwanted flow of energy associated with all accidents and to prevent accidents the associated with all accidents and to prevent accidents the energy has to be isolated, shielded and controlled from energy has to be isolated, shielded and controlled from people/ valuable objects people/ valuable objects

5. ¤ It clearly portrays the energy flow and failed or unused barriers that led to accidents ¤ The principal advantage of this method is that it identifies safety system elements that failed and the results can be succinctly presented Event and Causal Factor Analysis: ٭ It identifies the time sequence of a series of tasks and/or actions and the surrounding conditions that lead to an event ٭ It is used when there are multiple problems and the event factor chain is long and /or complex. Used in conjunction with other techniques Root Cause Analysis: Used to identify deficiencies, actual root cause, contributing causes and management systems that need to be corrected to prevent recurrence ¤ It clearly portrays the energy flow and failed or unused barriers that led to accidents ¤ The principal advantage of this method is that it identifies safety system elements that failed and the results can be succinctly presented Event and Causal Factor Analysis: ٭ It identifies the time sequence of a series of tasks and/or actions and the surrounding conditions that lead to an event ٭ It is used when there are multiple problems and the event factor chain is long and /or complex. Used in conjunction with other techniques Root Cause Analysis: Used to identify deficiencies, actual root cause, contributing causes and management systems that need to be corrected to prevent recurrence

6. It has an in-depth look at the basic causes that led to the accident A no.of methods are available for performing this analysis; many of them are specialized and apply to specific situations /objectives Complex Analytical Techniques: # These are applied to multiple system failures resulting in complex accident scenario. # Covers Fault Tree Analysis, Management Oversight and Risk Tree and Project Evaluation Tree It has an in-depth look at the basic causes that led to the accident A no.of methods are available for performing this analysis; many of them are specialized and apply to specific situations /objectives Complex Analytical Techniques: # These are applied to multiple system failures resulting in complex accident scenario. # Covers Fault Tree Analysis, Management Oversight and Risk Tree and Project Evaluation Tree

7. Fault Tree Analysis: It is commonly used in safety engineering It is a deductive approach that is very powerful as a qualitative analysis tool.If the probability data of events are known results could be quantified Fault branches down from top event, listing the faults in the system that occurred from general to specific event. Branches of the tree are contd until independent events are reached Faults can be events associated with component hardware failures, software problems, human errors, environmental conditions or any other element It is a very powerful technique requiring complex mathematical calculations

8. Specific Analytical Techniques: These are used in specific investigations depending on the nature and complexity of the event. ° Human Factors Analysis ° Energy Trace Barrier Analysis ° Sneak Circuit Analysis ° Cause Consequence Analysis ° Dispersion Modeling ° Kepner-Tregoe Problem Solving and Decision Making ° Sequential Timing and Events Plotting Human Factors Analysis: Here the focus is on the operability, work environment and management factors. It identifies the factors that influence task performance Specific Analytical Techniques: These are used in specific investigations depending on the nature and complexity of the event. ° Human Factors Analysis ° Energy Trace Barrier Analysis ° Sneak Circuit Analysis ° Cause Consequence Analysis ° Dispersion Modeling ° Kepner-Tregoe Problem Solving and Decision Making ° Sequential Timing and Events Plotting Human Factors Analysis: Here the focus is on the operability, work environment and management factors. It identifies the factors that influence task performance

9. Can be used to analyze most of the occurrences since many conditions and situations leading to an occurrence have ultimately originated from some performance problems Training in ergonomics and human factors is needed to perform adequately in man-machine interface situations Energy Trace Barrier Analysis: Its purpose is to identify hazards ( energy sources that can adversely affect an unprotected or vulnerable target ) by tracing energy flow into, through and out of the system By following the energy path one can determine if adequate controls were in place to prevent undesired energy release It is relatively inexpensive and rapid Can be used to analyze most of the occurrences since many conditions and situations leading to an occurrence have ultimately originated from some performance problems Training in ergonomics and human factors is needed to perform adequately in man-machine interface situations Energy Trace Barrier Analysis: Its purpose is to identify hazards ( energy sources that can adversely affect an unprotected or vulnerable target ) by tracing energy flow into, through and out of the system By following the energy path one can determine if adequate controls were in place to prevent undesired energy release It is relatively inexpensive and rapid

10. Sneak Circuit Analysis: *Here analysis is conducted on every possible combination of paths that a process could take (though used for electrical circuits, could be applied to other process flows ) and identify the sneak paths that are not designed in and but created due to failures (Sneak or latent paths are found in systems that are not operated frequently and hence are not easily identified) *The procedure is to review the system engineering drawings and translate them into a series of topological patterns that describe the entire circuit and trace the sneak paths. *Usually performed with complex computer codes and is expensive. It can be made cost-effective if performed on sub-systems that are safety critical.

11. Cause-consequence Analysis: *It uses symbolic logic trees. *The investigator starts with an accident scenario that adversely impacts the system and then develops a bottom-up analysis. Failure probabilities are calculated and incorporated into each step to quantify the tree. *A fault tree can be used to arrive at the event that challenges the system. From the top event the consequences are identified and severity of each consequence is determined. Dispersion Modeling: It is performed in plants where chemical emission can occur, to assess seriousness of the consequences. Maps and calculations are part of the system so that a total dispersion map for hazard analysis could be generated. eg. For the Monju fast reactor in Japan, when there was a sodium leak incident, this method was used to assess the sodium aerosol concentration at the site boundary to ensure that it was well within the permissible limits

12. Kepner-Tregoe problem Solving and Decision Making: ¤ This method is used when a comprehensive analysis is needed for all phases of investigation process ¤ Its strength lies in providing an efficient and systematic framework for gathering, organizing and evaluating informn ¤ It is a four step process that can be used for more than causal factor analysis ¤ This has a systems approach that prevents overlooking any aspect

13. Sequential Timing and Events Plotting: It is a comprehensive approach to reconstruct an accident and is based on events /causal factors charting It is a comprehensive approach to reconstruct an accident and is based on events /causal factors charting It is based on development of mental motion picture of the accident sequence as reconstructive tool It is based on development of mental motion picture of the accident sequence as reconstructive tool The worksheet illustrates the beginning and end of the accident sequence along column that represents time ; the rows lists the actors, either people or things, which acted to produce the harmful outcome. Each actor performs one action termed as event, that when displayed along timeline shows interactions between among actors and events The worksheet illustrates the beginning and end of the accident sequence along column that represents time ; the rows lists the actors, either people or things, which acted to produce the harmful outcome. Each actor performs one action termed as event, that when displayed along timeline shows interactions between among actors and events eg.The accident involving a reversing heavy eg.The accident involving a reversing heavy vehicle running over a worker at site vehicle running over a worker at site

14.  Time Actors v ehicle Worker DAE Hospital CGL Hospital Adequate tests are performed to make sure that events sequence is accurate and for completeness  Time Actors v ehicle Worker DAE Hospital CGL Hospital Adequate tests are performed to make sure that events sequence is accurate and for completeness