Muskrat Falls generating unit must be fully dismantled, says report

At least one of the generating units at the Muskrat Falls hydroelectric dam must be fully dismantled to undergo repairs — a "significant undertaking" for which the cost and timeline are unknown, according to a report submitted to the Public Utilities Board in June.

The latest independent monitoring report from Liberty Consulting says repeated "vibration issues" affecting Unit 2 have been reported since 2021, and that annual maintenance earlier this year showed parts of the unit were damaged "due to suspected hydrogen embrittlement," which can lead to cracks in metal under stress.

"Hydro has stated that it cannot identify how hydrogen got introduced in the metal, but noted that it could have come during [the] manufacturing process, site storage, assembly, or operation," the document reads. "The resulting uncertainty has implications for the existence of the phenomenon at the other three generating units, which Hydro considers possible."

Until the problem with Unit 2 is identified, "it remains prudent to consider the potential for material challenges to the short-term operation and long-term accelerated degradation of all the Muskrat Falls units," notes the 13-page report. 

"Planning and scheduling for the permanent solution remain pending," according to Liberty, which adds that Hydro is currently reviewing an investigation of the root causes of the vibration problem. 

Hydro declined an interview request but in a statement, spokesperson Jill Pitcher wrote that the "majority of the costs will be covered through the contractor's construction insurance."

"While there may be some costs to Hydro, these will be determined when the plan and timeline are finalized," added Pitcher, who also said there is currently "no impact on Hydro's ability to supply its customers in the province or outside the province" and that Hydro would "ensure there are no supply issues" once repairs begin.

According to the report, the only Muskrat Falls generating unit not to report problems in the first quarter of the year was Unit 4.

Liberty says Unit 1 was temporarily shut down due to a cracked discharge ring flange, noting "an earlier crack had occurred in the same area."

A temporary fix from manufacturer Andritz allowed the turbine to return to service for 125 hours at a reduced power level of 140 megawatts. The generating units are designed to operate at 206 megawatts. Liberty's report says Hydro was expected to complete permanent repairs "imminently," although similar fixes are also anticipated for Unit 3.

A separate issue caused Unit 3 to trip during routine operations, according to Liberty. Hydro subsequently discovered and repaired damaged cables and resistors in the unit, but has no idea how the damage occurred because monitoring software wasn't functioning.

"The incident led to the discovery that equipment presumably in continuous use to record and trend data had not been operating, thus precluding determination of underlying causes of the damage observed," writes Liberty.

The Liberty report also highlights several other previously reported issues with the Labrador-Island Link (LIL) transmission system, including faulty turnbuckles — metal parts used to regulate the length or tension of cables — in southern Labrador and on Newfoundland's Northern Peninsula. 

When the turnbuckles fail, a problem called "galloping" has occurred, as high winds push on iced-over power lines and cause a jumping motion that affects transmission.