Today marks the 30th anniversary of America’s worst commercial nuclear accident at three mile island. Many people remember the accident simply as the “three mile island incident”. What lessons have we learnt from this accident? Are we having better industrial management systems today than were present at that time? Are we better prepared now to face a similar challenge if it (God forbid it doesn’t) happens again?
For those of you who were not yet born at the time or were too young to remember, here’s a recap of the incident. The Three Mile Island nuclear power generating station, in Dauphin County, Pa was being operated by Metropolitan Edison, a utility company.
On March 28, 1979 the plant experienced a failure in the cooling system of the plant when the main feedwater pumps tripped. Due to overtemperature due to lack of cooling water, the reactor and the turbines tripped subsequently. However the reactor pressure began to increase. A pilot operated relief valve (PORV) opened to reduce the reactor pressure. After some of the pressure was relieved, the relief valve should have shut down again, but it remained stuck open. The plant instrumentation, apparently was not very sophisticated and the operators did not realise that this PORV was still open. More shockingly there was no instrument that showed the level of coolant in the core.
On the other hand a lot of alarms and annunciations flooded the control room and the operators did not realize that the incident happening was due to loss of coolant; they took steps to reduce the coolant flow further and exacerbated the situation. Because of a lack of cooling, the nuclear fuel overheated to the point at which the zirconium cladding ruptured and the fuel pellets began to melt. One-half of the core melted during the early stages of the accident. Thus the plant suffered a severe core meltdown, the most dangerous kind of nuclear power accident, it did not produce the worst-case consequences that could have happened. In a worst-case consequence, the melting of nuclear fuel would lead to a breach of the walls of the containment building and release massive quantities of radiation to the environment. Fortunately nothing of this kind happened, but small amounts of radioactive gases were found by monitoring instruments in the plants vicinity and this concerned the authorities. By March 30 a lot of people deemed “vulnerable” like small children and pregnant women were evacuated from the area.
Have we learnt our safety management lessons from this incident? Are today’s instrumentation and control systems more reliable and sophisticated than those on the three mile island plant? Are todays government personnel, emergency staff and plant operators better trained and more comptent?
This accident marked a decline of the nuclear industry in most parts of the world (except perhaps France). Today when it is seeing a revival due to the crude supply situation and the campaign against fossil fuels, we must ask ourselves these questions.
You are welcome to post your answers and opinions in the comments section.