TORONTO -- The proposed $12.8-billion refurbishment of four nuclear reactors at the Darlington generating station is an ill-advised make-work project that will end up soaking taxpayers, a retired nuclear scientist says.

In a letter to Ontario's energy minister, obtained by The Canadian Press, Frank Greening warns of the formidable technical hazards he says will undermine rosy projections for the project.

"I am quite mystified that you would consider the refurbishment of Darlington to be some sort of solution to Ontario's economic woes, when in fact the premature failures of (nuclear reactors) are a major cause of Ontario's economic problems," writes Greening, a frequent critic of the industry.

"Spending billions of dollars trying to patch up Darlington's four dilapidated reactors will simply continue the bleeding."

Earlier this month, the province's publicly owned generating giant, Ontario Power Generation, announced plans to start refurbishing Darlington -- situated east of Toronto on Lake Ontario -- this fall. The project aims to extend the life of the CANDU reactors, scheduled for permanent shutdown in 2020, by 30 years.

The government projects the rebuild will create up to 11,800 jobs a year at the height of construction and generate $14.9 billion in economic and spinoff benefits.

Greening argues the units are in need of rebuilding prematurely because their pressure tubes and feeder pipes will soon fail fitness tests. He also warns the reactors' massive steam generators, which are not part of the proposed project, have had a less than stellar track record and will more than likely need replacement.

"Replacing these steam generators is fraught with very serious problems, both technical and economic, that could prevent the continued operation of Darlington beyond 2030," says Greening, a senior scientist with OPG until he retired in 2000.

"The decision to proceed with the refurbishment of Darlington could prove to be a disastrous mistake if it is discovered that steam generator replacement is in fact needed in the next 10 to 15 years."

Environmental groups also argue such projects always run massively over budget and have cost taxpayers untold billions in the past and refurbishment is simply not worth the potential radiation risk to public safety.

The Ontario cabinet has so far given the green light to refurbish one of Darlington's reactors. OPG would need separate approvals for each of the other three units. The government said that process would allow it to call off the project at each stage if things are going awry.

Energy Minister Bob Chiarelli, who argues the province needs Darlington's power, referred questions about Greening's criticism to Ontario Power Generation.

OPG spokesman Bill McKinlay said Wednesday the federal nuclear regulator noted Greening's concerns before giving the project its stamp of approval.

"We've been preparing since 2009 and we're ready to deliver the job safely, on time and on budget," McKinlay said. "We expect it will provide 30-plus years of clean, reliable base-load power at a cost lower than other alternatives."

Greening, however, argues the project is an attempt to put a "dying industry on life support" at the taxpayer's expense.

"The inconvenient truth is that, after less than 25 years of operation, Darlington NGS is a mess," he says.

"Its feeder pipes are falling apart and its pressure tubes are ready to crack. Darlington is another failed CANDU station desperately in need of a fix."

The performance of four other refurbished CANDUs in Ontario, he argues, has fallen well short of what a new reactor typically delivers.

"This reveals the uncomfortable truth: A refurbished CANDU reactor is no substitute for a new one."