Normal Accidents:Normal Accidents: Living with High-Risk TechnologiesLiving with High-Risk Technologies

Minho JeungMinho Jeung

Trinity TeamTrinity Team

12/06/200512/06/2005

ContentsContents

1.1. IntroductionIntroduction

2.2. Normal Accident Theory Normal Accident Theory

3.3. Three Mile Island Three Mile Island

4.4. Policy RecommendationsPolicy Recommendations

5.5. Conclusion Conclusion

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Modern people manage to get along one wayor others meeting with an accident.

People forget accident immediately and adaptthemselves the dangerous environment

People do not have any solution to addressthe problem

Tightly coupled technology system makes people not avoid an accident

Accidents are neither abnormal nor deviatory.

Accidents are normal events for complex system.

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1. Introduction1. Introduction

The accidents caused by component failures

The accidents are caused by interactive complexity in the presence of tight coupled system.

Modern systems can tolerate the impact of the fault of a single component.

Normal accidents are not caused by the failure of component but the interaction of components.

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2. Normal Accident Theory2. Normal Accident Theory

Figure1: Complex and tight coupling system Figure2: Linear and loose coupling system

This picture is referenced by Introduction Accidents Analysis, Yu-Hsing Huang, CSELAB, University of Linkoping

Tightly coupled interactions: These are represented to those that do not tolerate delay. They have invariant sequences and small slack.

Loosely coupled interactions: These have the opposite characteristics. The interactions are linear or complex. The linear means simple system. The other is complex. Thus, Perrow made the following framework to classify systems according to these definitions.

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2. Normal Accident Theory2. Normal Accident Theory

Interactions

Coupling

tight

linear complex

loose

assembly line

cars

R&Dfirms

DNA

nuclearplant

nuclearweapons

dams Power grids

mining

Systemic elements led to major Systemic elements led to major accidents, not the actions of the accidents, not the actions of the operators themselvesoperators themselves

The combination of interactive The combination of interactive complexity and tight coupling of the complexity and tight coupling of the high risk systemshigh risk systems

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3. Three Mile Island3. Three Mile Island

This picture is referenced by http://www.libraries.psu.edu/tmi/images/tmi.jpg

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3. Three Mile Island3. Three Mile Island

This picture is referenced by http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/tmi-2.gif

Perrow made a set of policy recommendations, which are

targeted at specific systems.

The three policies are: abandon, restrict, tolerate and improve.

Plotted various systems on the chart, and then draws curves

to split them into three categories.

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4. Policy Recommendations4. Policy Recommendations

Cost of alternatives

Catastrophic potential

low

low high

high

chemicals

DNAdams

space

mining

nuclearplant

nuclearweapons

abandon

restrict

tolerate &improve

5. Conclusion5. Conclusion

Tightly coupled system can cause Tightly coupled system can cause

catastrophic accidents.catastrophic accidents.

The system is made loosed or the system The system is made loosed or the system

has some redundancy. has some redundancy.

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► ► Lessons LearnedLessons Learned

► ► How we apply Normal Accident Theory to Studio? How we apply Normal Accident Theory to Studio?

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5. Conclusion5. Conclusion

The VR engine can be used in various fields of industry

It will be tightly coupled with the legacy system

Design the system to have redundancy.

Thank youThank you