A continuation of the top 10 major accidents over the last century that have had a major influence on our regulatory regimes and industry standards on risk management. Click here to see Part 1: Major Accidents in the World.
Disaster # 4 - Chernobyl Disaster
The Chernobyl disaster was a catastrophic nuclear accident that occurred on 26 April 1986, at the Chernobyl Nuclear Power Plant in Ukraine, near the town of Pripyat (then part of the Soviet Union). It is considered the worst nuclear power plant accident in history and is the only level 7 event on the International Nuclear Event Scale.
The event occurred during an unauthorized systems test. A sudden power output surge took place during the test, and when an attempt was made at an emergency shutdown, a more extreme spike in power output occurred which led to the rupture of a reactor vessel as well as a series of explosions. This event exposed the graphite moderator components of the reactor to air and they in turn ignited; the resulting radioactive fire sent a plume of radioactive fallout into the atmosphere and over an extensive area, including Pripyat. The plume drifted over large parts of the western Soviet Union, and much of Europe. As of December 2000, 350,400 people had been evacuated and resettled from the most severely contaminated areas of Belarus, Russia, and Ukraine. According to official post-Soviet data, up to 70% of the fallout landed in Belarus. Fifty immediate deaths, all among the reactor staff and emergency workers, are directly attributed to the accident. However, it is estimated that there may ultimately be 4,000 deaths or more attributable to the accident, due to the effects of radiation exposure and resulting cancer.
Since the accident occurred in the former Soviet Union, there was little information provided to neighbouring cities and countries. The levels of radiation exposure were not made public and it took nine days before a full scale evacuation of a 30 km radious was ordered for 135,000 people. The disaster resulted in major reviews of the design and operation of nuclear power stations around the world. The lessons learned from Chernobyl were related to the poor safety culture and poor management systems in place but also were related to the poor design of the plant and poor operations an planning processes for normal and abnormal operations.
The United States had a similar incident at Three Mile Island in 1979, however in that case, there was never a complete loss of containment and the incident was minor compared to Chernobyl. However, both events have had a major impact on nuclear safety and regulations around the world. These events probably set the nuclear industry back decades as far as the number of reactors built but have also allowed much safer design and operation. As discussed in my Jan 17 blog post on the recent BP Spill Report, the US nuclear industry instigated a self policing agency called the Institute of Nuclear Power Operations (INPO) who's mission was " to promote the highest level of safety and reliability". This has had a dramatic impact on US and world nuclear safety and was cited by the Spill Report team as an example of what can be done for the offshore E&P industry.
Disaster # 3 - Challenger Shuttle Explosion
The Space Shuttle Challenger disaster occurred 25 years ago today, on Tuesday, January 28, 1986, when the space orbitor broke apart after only 73 seconds into its flight, leading to the deaths of all seven crew members. It was also the 25th space shuttle mission, which included in it's crew a teacher who was selected to be the first educator in space. It was a watershed event for the American Space Program. The space ship was completely destroyed due to an explosion caused by a simple technical issue which was entirely preventable. An O-ring seal in the right solid rocket booster (SRB) failed at liftoff. The O-ring failure caused a breach in the SRB joint it sealed, allowing pressurized hot gas from within the solid rocket engine to reach the outside and impinge upon the adjacent SRB attachment hardware and external liquid hydrogen fuel tank. This led to separation of the right-hand SRB's aft attachment, structural failure of the external hydrogen fuel tank and ignition of the hydrogen fuel. The explosion and aerodynamic forces promptly broke up the orbiter which was travelling at over 2200 feet per second by that time.
NASA managers had known that contractor Morton Thiokol's design of the SRBs contained a potentially catastrophic flaw in the O-rings since 1977, but they failed to address it properly. They also disregarded warnings from engineers about the dangers of launching posed by the low air temperatures of that morning and had failed to adequately report these technical concerns to their superiors.
NASA, in the followup to the the disaster, requested a lessons learned report be completed by their Safety Division. The report was issued in February 1988 but was suppressed by NASA brass for years, as they were not pleased with the details within and were not able to come to terms with the findings. This only made the points within the report more obvious, as the overriding finding was related to NASA management and work force. The following extract from section 2.1 of the report states the overriding issue quite well (Ref. Lessons Learned from Challenger
Headquarters National Aeronautics and Space Administration Safety Division, Office of Safety, Reliability, Maintainability and Quality Assurance. Washington, DC 20546, February 1988):
A single underlying and pervasive problem, and as a result some inescapable conclusions, emerge from discussion items in this analysis and from investigations and testimonies reviewed in the reference documents. While some critical voids in the overall management system existed at the time of the 51-L accident, the basic problem was not so much lack of management system definition as it was lack of management system control. Some requirements in the system were ignored by both management and the work force; a breakdown in communications existed from top-level management to workers on the floor; there was a willing abandonment of some critical management controls. Managers were pressuring the work force to break management rules in an attempt to maintain flight schedules. To put this condition in proper perspective, it should be noted that the United States space program was built on innovation and willingness to circumvent or waive the rules to make productive things happen. It is impossible to conceive of a tight management system that would offer complete control over unforeseen problems and contingencies. There will be times when rules have to be circumvented or waived to accommodate urgent demands of the moment. Conversely, it should be recognized that this philosophy can promote ill-conceived judgements and human errors if uncontrolled or taken to extremes. The Space Station Program should have a policy that management rules and requirements must be followed, unless to do so would cause greater problems and risks. If the rules must be broken, it must be accomplished in a manner which ensures that all people and organizations having critical inputs and oversight management responsibilities know about the deviations in time to make deliberate and prudent decisions. When rules are circumvented or waived, especially in a repetitive manner, assessments of the existing management system must be made to determine if changes to the system are required to eliminate the need for those deviations in the future. Also, it should be remembered that communication with the work force is crucial to the entire process. For in the end, it is people-down to those who are engaged in the most fundamental tasks - who ultimately control the success or failure of any complex endeavor.
These words from 1988 still apply today and should be remembered every time we make decisions that are risk sensitive. We have the advantage today of better technology yet major accident events still occur. We need to heed the words of lessons learned reports such as these and take action on risk to avoid repeating them in the future.
The Accident was broadcast to the world live on CNN:
Stay Tuned for the final post of this five part series where we explore the two top disasters that have influenced world regulations and standards.