Several definitions exist for the concept of a major accident. We apply the following:
A major accident is defined as an acute incident, such as a major discharge/emission or a fire/explosion, which immediately or subsequently causes several serious injuries and/or loss of human life, serious harm to the environment and/or loss of substantial material assets.
Both the design of facilities and plants, the choice of technical solutions with good inherent safety characteristics and the choice of effective barriers are included in the measures to prevent undesirable incidents.
The catastrophe when Alexander L. Kielland capsized in 1980 and the explosion and fire on Piper Alpha on the British continental shelf in 1988 show the dramatic consequences major accidents in the petroleum activities can have.
In recent years, incidents on the Norwegian shelf and at the land facilities have also had the potential to become major accidents.
The last major accident in the petroleum activities on the Norwegian shelf was the helicopter accident off Turøy in 2016, where 13 people died.
Both the design of facilities and plants, the choice of technical solutions with good inherent safety characteristics and the choice of effective barriers are included in the measures to prevent a major accident from occurring
Mapping of major accident risk:
The authorities base their description of the risk development on a number of aspects. Experiences from audits, reporting of accidents and near misses, investigation of major incidents and R&D activities are important sources.
As regards the development of major accident risk, the results from the "Trends in risk level" are crucial. Specific areas where the probability of major accidents is the greatest have been identified through this mapping:
There is a multitude of technical, operational and organisational factors within these areas, and each factor can, alone or in combination, cause accident incidents or affect a possible course of events.
During the period 1996 – 2004, these areas contributed more than 80 per cent of the total major accident risk on the Norwegian shelf.
Helicopter transport also has a major accident potential, but does not form part of the major accident indicator used in "Trends in risk level".
Major accident risk at land facilities
The results from the land facilities were first included in the RNNP report for 2006.
The largest risk contribution to major accidents at the land facilities would be hydrocarbon leaks followed by fire or explosion.
The land facilities often have production processes which carry large flows of hydrocarbons and they also have large storage capacity.
It may therefore be expected that a large hydrocarbon leak at a land facility will be larger than a large leak from an offshore facility. In addition, the processes are often more complex, with high temperatures and high pressure.
As a result, the consequences of a fire or explosion may be very significant.
However, the risk of personal injury in the event of a fire or explosion at a land facility is smaller than for a corresponding incident at an offshore facility.
This is due to the fact that the opportunity to escape is better at the land facilities, as well as the fact that the number of people near the processing areas will not be as high during normal operations.
During modification processes and simultaneous operations, this picture may change and more persons may become exposed. Experience from foreign facilities indicates that major maintenance work represents a clear increase of risk.
A major accident will, in addition to the human aspects, also have substantial consequences for society at large and the reduction of major accident risk is therefore a crucial reason for the formulation of existing health, safety and environment regulations.
For those affected by an accident, the loss will be far greater than what appears in the socio-economic evaluation – the value of a life cannot be expressed in money.