A power plant explosion described as a "catastrophic missile event" could have been avoided, a long-awaited report has found.
Forensic engineer Sean Brady's draft independent report on the 2021 Callide Power Station's C4 unit incident in central Queensland that left almost half a million customers without power was released on Tuesday.
The damning findings into the explosion near Biloela prompted the government to appoint advisors to the board of the Callide C plant's state-owned operators CS Energy.
A review of Queensland’s publicly owned energy businesses will also be conducted in the fallout over the draft report.
Three years after the incident, the draft report finally details what led to the "catastrophic failure".
It found while engineers were connecting a new battery system, there was a loss of power in the unit and no back-up system was in place following damage from an earlier incident.
The loss of power happened within two seconds, leaving the unit unable to operate normally, shut down safely or disconnect from the grid.
It ensured the turbine motor kept spinning, leading to a "catastrophic" failure of the plant.
Pieces of metal, weighing nearly half a tonne, blasted out of the turbine in what was labelled a "missile event".
Dr Brady found CS Energy's oversight in understanding and addressing the risks of not completing the upgrade to the redundancy battery chargers exacerbated the incident.
"If it had been operable ... the turbine missile event would likely have been avoided, but the unit would still have sustained significant damage," the report said.
CS Energy's failure to comprehensively understand the issues with its systems led to it being unable to anticipate or prevent the incident.
"The failure to understand and assess risk, and to not effectively apply sound management of change processes in relation to the engineering factors that led to the catastrophic failure, suggests these were not isolated incidents, but rather a symptom of an organisation’s failure to value and implement effective process safety practices," the report said.
There was no evidence that mechanical or metallurgical factors contributed to the explosion.
Premier Steven Miles has appointed special advisors to CS Energy's board, among a number of measures that coincided with the report's release.
"It's timely now that we have this draft report to consider what further actions the government should take to ensure that nothing like this ever happens again," he told reporters on Tuesday.
The review of publicly-owned energy businesses would be carried out before next year's budget.
Mr Miles said the government would take public ownership of 100 per cent of the Callide C station from a private joint venture partner.
The government said further action may be taken when the final report was handed down.
Opposition Leader David Crisafulli described the Callide incident as one of Queensland's greatest scandals.
"What has happened at Callide was avoidable. It's completely and utterly disgraceful and it's unforgivable," he said.
The station's Callide C3 generator has been back online since April.
The remaining turbine - Callide C4 - will make a staged return to service on June 30 before returning to full capacity on July 31.
