Stephen Galsworthy, Andrew Hutin and Leonard Radford were fatally injured in a massive explosion the Corus works on 8 November 2001.
 
At Swansea Crown Court, the company pleaded guilty to two charges of failing to ensure the safety of their employees under the Health and Safety at Work Act 1974.
 
In a statement at the conclusion of the case, HSE Director for Wales, Terry Rose said: "Having met with the families of Mr Galsworthy, Mr Hutin and Mr Radford over the last five years I want to pay tribute to them. I have seen their grief and frustration, and we should all recognise that whatever has happened today cannot bring back their loved ones. Fines are insignificant alongside that."
 
He added: "This was systematic corporate management failure at the Port Talbot works. Proper management attention may have broken the chain of events which led to the explosion."
 
The explosion was caused by water in the furnace coming into sudden contact with hot material. As water turned into steam it expanded rapidly, creating pressure, which blew a confined vessel apart.
 
Rose said: "As far as we can establish an explosion of this magnitude is unprecedented in any blast furnace anywhere in the world.
 
"The proper design, maintenance and operation of the water cooling system is vital to the safe operation of the furnace and the ability to detect, and stop, water leaking into the furnace in quantity is very important. Corus failed to do this in relation to Blast Furnace 5. Those failings were spread over many years, with many different people involved. That is why HSE prosecuted the company, rather than any individuals.