LICENSED and PERMITTED THERMAL POLLUTION of Cape Cod Bay by Pilgrim Nuclear Power Station (PNPS)

How efficient is Pilgrim? Not very, according to this new efficiency review. Only 34% of Pilgrim’s thermal energy is converted to electricity, meaning two-thirds (66%) of the thermal energy is discharged into Cape Cod Bay! We REALLY need a closed-loop cooling system installed at Pilgrim to stop this massive amount of thermal pollution!

Thermal pollution can negatively affect metabolic rates, feeding behavior, reproduction, and distribution of marine organisms. It also encourages parasites and invasive species. Learn more →

Read our “What is Thermal Pollution?” Fact Sheet →

Facts to Consider:


  • PNPS is licensed by the U.S Nuclear Regulatory Commission (NRC) to produce up to 2028 MWt (million watts thermal) of heat with its GE Mark 1 Boiling Water Reactor and use that power to generate up to 690 MWe (million watts electric) of electricity.[1]
  • 34% of the thermal energy produced is converted to marketable electricity (690/2028).
  • 66% of the thermal energy is discharged into Cape Cod Bay. PNPS is permitted by the U.S. Environmental Protection Agency (EPA) to use a once through cooling system.[2]

Thermal Pollution Quantities:

  • PNPS is licensed to pump up to 447 million gal/day (more than 163 billion gal/yr) from Cape Cod Bay for cooling and return it up to 32 degrees Fahrenheit hotter.[3]
  • This is equivalent to about 116.5 billion BTUs/day (42.5 trillion BTUs/yr) of heat energy (thermal pollution).[4]

What does 163 billion gal/yr of water look like? (163 Billion)

  • More than enough to run one shower (typical shower head delivers 2.5 gal/min)[5] every day, all day long, all year long in every household on Cape Cod and the Islands (138,440,412,000 gal/yr; in 105,358 households; by a population of 242,595).[6]
  • 100 times more than the Town of Plymouth’s Water Department pumps to meet the entire town’s municipal and domestic water requirements (1,567,343,161 gal/yr).[7]

What does 42,500,000,000,000 BTUs/yr of heat energy look like? (42.5 Trillion)

  • The average American home using fuel oil for heating consumes about 700 gallons of fuel per year[8] (97,090,000 BTUs/yr).[9]
  • Every year PNPS discharges enough thermal energy into Cape Cod Bay to heat 437,800 homes every year with fuel oil.
  • That’s more than 4 times the number of resident households on the Cape and Islands and similarly 2.4 times the number of resident households in Plymouth County.[10]


  • Two thirds of the energy produced by PNPS is discharged as heat into Cape Cod Bay.
  • Any way you slice it, this is thermal pollution on a disturbing scale.
  • Employing a once-through cooling system as acceptable practice is analogous to and based in the technology and sensibilities (dilution is the solution) dating back to the 1960s when landfills and open burning at landfills were also acceptable practices.
  • A closed-loop cooling systems is a simple technology and has been the preferred contemporary best practice for decades. Remediation is 20 years overdue.

View the PNPS efficiency chart (MS excel file) with calculations.

[1] Entergy reports the “Maximum Dependable Output as 688 MW” ; The NRC License Renewal Application documents 690 MW as licensed output
[2] U.S. Environmental Protection Agency, NPDES Permit #MA0003557
[3] U.S. Environmental Protection Agency, Pilgrim Nuclear Power Station “Discharge Monitoring Reports” for 2014. 447 MGD is the licensed upper limit averaged over the course of a month. On any single day if extreme conditions require it, PNPS is licensed to use 510 MGD. Also see Endnote 2.
[4] 1 BTU (British Thermal Unit) equals the thermal energy required to raise 1 pound of water 1 degree Fahrenheit.
[5] US Environmental Protection Agency
[6] U.S. Census Cape Cod (Barnstable County) has a population of 215,888 in 95,398 households; Martha’s Vineyard and the Elizabeth Islands (Dukes County) have a population of 16,536 in 5,891 households; Nantucket Island (Nantucket County) has a population of 10,172 in 4,069 households.
[7] 2013 Pymouth Annual Report
[8] U.S. Energy Information Administration
[9] Home heating fuel oil produces 138,700 BTUs/gallon.
[10] U.S. Census Bureau (105,358 households) See Endnote 7