The chart below shows the difference in cesium-137 (an extremely hazardous isotope that releases radiation) released by the Chernobyl nuclear accident in 1986, present in Pilgrim’s reactor core, and stored in Pilgrim’s spent fuel pool. As you can see, Pilgrim’s spent fuel pool holds 1,731% more cesium-137 than was released in the Chernobyl accident, and 758% more cesium-137 than is in Pilgrim’s reactor core.

Chart courtesy of Cape Downwinders.


Click to view a larger version.


Pilgrim’s nuclear waste – and the source of the cesium-137 – is currently stored in a pool inside the nuclear reactor building and requires constant vigilance, including water pumping and circulation. This presents an unnecessary risk to public health, safety, the environment, and the economic well-being of surrounding communities.

For example, climate change patterns (rising sea levels, warming sea water and air temperatures, increasing intensity of storms and related storm surges) threaten the facility’s cooling system that is essential to normal operations and prevents a nuclear meltdown. The waste stored in Pilgrim’s spent fuel pool is kept cool using offsite power and pumps that circulate the water in the pool to heat exchangers. Prolonged power loss and flooding both pose a risk to pumps that are crucial to preventing a nuclear accident. Failed pumps due to prolonged power loss or flooding could cause the reactor to overheat or the water in the spent fuel pool to boil and evaporate, exposing the highly radioactive fuel rods to air. Both situations could lead to fire and explosions and radioactive release.

Risks of wet pool storage include economic damage and cancers: a 2006 report to the Massachusetts Attorney General states that a small release (10% release) of cesium-137 due to a pool fire could result in damages up to about $170 billion and 8,000 latent cancers, while a large release (100% release) could result in damages up to $488 billion and 24,000 latent cancers.

Visit the U.S. Environmental Protection Agency’s (EPA) website to learn more about cesium. EPA’s website states:

Like all radionuclides, exposure to radiation from cesium-137 results in increased risk of cancer. Everyone is exposed to very small amounts of cesium-137 in soil and water as a result of atmospheric fallout. Exposure to waste materials, from contaminated sites, or from nuclear accidents can result in cancer risks much higher than typical environmental exposures.

If exposures are very high, serious burns, and even death, can result. Instances of such exposure are very rare. One example of a high-exposure situation would be the mishandling a strong industrial cesium-137 source. The magnitude of the health risk depends on exposure conditions. These include such factors as strength of the source, length of exposure, distance from the source, and whether there was shielding between you and the source (such as metal plating).

Pilgrim’s waste needs to be moved from wet pool storage to dry casks as soon as possible, as dry cask storage poses less risk than the current wet pool storage method. However, dry cask storage facility must be designed, built and operated under the highest of standards – currently not being done. Learn more >>

There are various safety improvements and recommendations that should be implemented with regard to Pilgrim’s dry cask storage. First, the movement of the waste in Pilgrim’s spent fuel pool into dry cask storage needs to be expedited. Entergy should be required to reduce the pool to low density, and only store fuel assemblies five years old or less in the pool (the assemblies need 5 years to cool in the pool before they can be transferred to casks). The storage facility should also be moved to higher ground and further away from Cape Cod Bay. Right now, it is located at about 24 feet above mean sea level and as close as 175 feet from the shoreline. Entergy’s present plan leaves the facility vulnerable to major storm surges, corrosion, and sea level rise. The storage of any waste other than Pilgrim’s should be prohibited, monitoring should be required to measure temperature and radiation of the casks, and Entergy should be required to pay the Town of Plymouth enough compensation so that the town will not be left holding the financial bag.

More information about cesium and the risks of wet pool storage:

Pilgrim Risks: Accidents and Daily Operations, by Mary Lampert, Pilgrim Watch (2014)

Facts about Cesium-137, fact sheet by EPA (2002)

Risks and Risk-Reducing Options Associated with Pool Storage of Spent Nuclear Fuel at the Pilgrim and Vermont Yankee Nuclear Power Plants, Thompson G. (2006)

Report to the MA Attorney General on the potential consequences of a spent-fuel-pool fire at the Pilgrim or Vermont Yankee nuclear plant, Beyea J. (2006)