Pilgrim Shutdown Causes Increase in Hydrogen Gas Release


PLYMOUTH – The shutdown of the Pilgrim Nuclear Power Station last week has caused an increased release of hydrogen gas.

The plant reported 22 pounds of the gas release during a 24-hour period on Tuesday which is higher than the regulated allowance of 10 pounds per day.

Plant spokesmen Patrick O’Brien said the increase was expected.

Nuclear Regulatory Commission spokesman Niel Sheehan said no risk was posed to the plant staff or the public because the hydrogen quickly dissipates throughout the turbine building room and is vented to the outside atmosphere.

“Hydrogen release rates are elevated while the plant is shut down because the hydrogen seal on the generator cooling system cools down from its at‑power temperature and contracts,” Sheehan said in a statement. “Once the plant starts back up and things warm up again, the hydrogen seals will expand and any leakage will be halted.”

The hydrogen release rates from this shutdown are comparable to rates from previous shutdowns, according to Sheehan.

The shutdown was caused by a leak in the main steam line.

The reactor was powered down Thursday and staff discovered the small leak during routine testing.

O’Brien said the value repair has been completed but other maintenance work is ongoing that cannot be done when the plant is at full power. It is not known when the plant will re-connect to the grid, according to O’Brien.

Pilgrim is under increased federal oversight after a series of safety violations and unplanned shutdowns. Inspectors wrapped up the first two weeks of a review of the station earlier this month and will return to the station in January to wrap up a federally-mandated inspection of Pilgrim.

An internal Nuclear Regulatory Commission e-mail made public earlier this month detailed concerns about the plant’s safety culture, with the lead inspector saying staff seemed “overwhelmed” by running the plant.

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