New research on water circulation in Cape Cod Bay shows that if radioactive wastewater were discharged from the Pilgrim Nuclear Power Station, it would likely remain in the bay for at least a month.
The researchers used a high-resolution model of ocean circulation developed by the National Oceanic and Atmospheric Administration.
They found that the probability of wastewater particles leaving the bay within three weeks is only 12 percent in spring and summer, and even lower in fall and winter.
“Even in spring and summer, the bulk of the wastewater is much more likely to stay in the bay,” said one of the study authors, physical oceanographer Irina Rypina of Woods Hole Oceanographic Institution.
"It is unlikely that the wastewater would leave the bay over those timescales," she said.
The study seeks, in part, to address public concerns about the fate of radioactive material in reactor-system water at Pilgrim. Pilgrim owner Holtec International has proposed discharging the water into Cape Cod Bay as part of the plant decommissioning.
The Pilgrim reactor was shut down in 2019. The water that remains — more than 900,000 gallons — would be treated and diluted, but treatment does not remove all contamination, including some of the radioactive isotopes.
As the water moves through the bay, the particles it transports would very likely move close to the coastline, including in Dennis, Wellfleet, and Provincetown, Rypina said. And particles that leave the bay would be pushed by currents around the tip of the Cape.
“Even if it gets out, it will flow along the Outer — close to the Outer Cape and Provincetown,” she said.
Seasonal winds and the exact location of a water release would affect where the water goes.
The study, in the Journal of Physical Oceanography, focuses on currents near the surface.
Rypina said future research could look at what would happen if the Pilgrim water were released deeper in the bay.
