As Pilgrim shuts down, danger still lurks

Spent fuel pool fire worse than meltdown, can reach the Vineyard from Plymouth or hundreds of miles away.


Pilgrim Nuclear Power Station will shut down its reactor on May 31 after 47 years of operation. Built in 1972 for Boston Edison, it’s the only operational nuclear power plant in Massachusetts, and has been since Yankee-Rowe ceased operation in 1992.

Louisiana-based Entergy bought Pilgrim from Boston Edison in 1999. By 2014, the station languished as one of the poorest performers on the Nuclear Regulatory Commission rating system, the last straw before the federal government enforces a mandatory shutdown in the interests of public safety. In March this year, citing better inspection findings, the NRC boosted Pilgrim to a top-notch performer, a status that requires the least federal oversight. The switch flummoxed local watchdog groups. In 2017, Pilgrim made a business decision to permanently shut down.

While the potential dangers posed by Pilgrim in the event of a calamity have long haunted Cape Cod and Plymouth County, the six towns of Martha’s Vineyard are roughly 33 to 43 miles away from the station, well outside the Pilgrim 10-mile Emergency Planning Zone where people would be expected to evacuate in the event of a radioactive plume. However, independent modeling based on NRC data shows the spread of fallout from at least one type of station disaster could reach the Vineyard not just from Pilgrim, but from a similar station hundreds of miles away.

Speaking for the Vineyard’s emergency managers, Edgartown Fire Chief Alex Schaeffer said Island planners and first responders look to the Massachusetts Emergency Management Agency (MEMA) and the Massachusetts Department of Public Health for assistance and direction in the event of a radiological incident. MEMA declined to answer specific questions posed by The Times, and declined make its director available for an interview.

Steamship Authority spokesman Sean Driscoll told The Times he knows of no written plan for the evacuation of Martha’s Vineyard via the SSA fleet in the event of a Pilgrim incident. He said he expects the SSA would partner with state and federal agencies, and absent a shelter-in-place order, could ferry passengers to Woods Hole or the SSA facility in Fairhaven, if need be. Logistically, he said, such an evacuation seemed at best a long process, especially in the summer months when the Island harbors more than 100,000 people.

On Tuesday, a team of nuclear technicians demonstrated a controlled shutdown of Pilgrim’s reactor at the Entergy’s Chiltonville Training Center, nearby the station itself. The demonstration was executed in a simulator constructed as an exact replica of the reactor control room. The methodical process involved annunciation of every step, often followed by verification from a peer or supervisor. When the SCRAM buttons were finally depressed, lights winked across panels, alarms whined, and imaginary control rods began to stymie fission. The real control rods, lengths of boron with graphite and hafnium worked into them, will do the real thing two days later. Then, sometime in June, the fuel rods will be permanently removed from the reactor vessel, and with them any danger of a reactor meltdown.

However, in the station’s spent fuel pool, conditions capable of producing an incident more dangerous than a meltdown will persist for at least three years after shutdown. In the pool, over 2,000 fuel assemblies are being cooled until they can be safely transferred to dry casks. So long as these assemblies remain under cold water, they are stable. But should an industrial accident, natural disaster, or act of terrorism either damage the pool and drain water, or damage the cooling system and permit water to heat to a boil, the assemblies could become exposed to air and grow hot, reports from the Nuclear Regulatory Commission and the Union of Concerned Scientists indicate. Under such circumstances, assemblies can ignite and spew radioactive smoke.

Pilgrim’s spent fuel pool is considered densely packed. The practice of dense-packing spent fuel pools — filling them with more assemblies than they are designed to handle — has worried some nuclear experts, notably Frank N. Von Hippel of Princeton University. Von Hippel, along with former Princeton researcher Michael Schoeppner, showcased the threat in “Reducing the Danger of Fires in Spent Fuel Pools.”

Densely packed fuel pools, Von Hippel and Schoeppner wrote, run the risk of “releasing huge quantities of cesium-137 into the atmosphere.”

“Exposure to Cs-137 can increase the risk for cancer because of the presence of high-energy gamma radiation,” according to the Environmental Protection Agency. “Internal exposure to Cs-137 through ingestion or inhalation allows the radioactive material to be distributed in the soft tissues, especially muscle tissue, which increases cancer risk.”

“Cesium-137 is the main radioactive contaminant that has forced the long-term relocation of populations from large areas around the Chernobyl and Fukushima Daiichi nuclear power plants,” Von Hippel and Schoeppner wrote.

Robert Alvarez wrote in the Bulletin of the Atomic Scientists that a pool fire can “release catastrophic amounts of long-lived radioactivity — far more than a reactor meltdown.”

The NRC studied the hypothetical ramifications of a water-loss disaster in the wake of Fukushima, where in addition to three reactor meltdowns following an earthquake and tsunami, a spent fuel pool almost lost its water — a situation former Japanese Prime Minister Naoto Kan told PBS’s “Frontline” would have necessitated the evacuation of Tokyo. The NRC chose Pennsylvania’s Peach Bottom Nuclear Power Plant for its study, and considered pool water loss from an earthquake.

Von Hippel and Schoeppner found numerous faults with the economic, health, and land area impacts the NRC arrived at, among other aspects, and opted to remodel and recalculate the study. Despite emanating from over 400 miles away, Von Hippel and Schoeppner showed that in weather patterns in three out of four months modeled, cesium-137 from a Peach Bottom pool fire would contaminate Martha’s Vineyard as part of a Northeast dispersal, and in one model, carry all the way to Canada.

At Chiltonville, Entergy senior government affairs manager for decommissioning Joe Lynch said, “It’s in everyone’s best interests” to get the assemblies out of the pool and into dry casks. This is a fundamental safety argument made by Alvarez, Von Hippel, and Schoeppner for all assemblies in densely packed pools in the nation’s nuclear power plants.

Lynch said Entergy aims to complete the task in three years.  

Once filled, the casks, huge stainless steel cylinders nested inside even larger concrete cylinders, are hauled to an independent spent fuel storage installation (ISFSI) pad on the station’s grounds. Many assemblies are already in casks onsite, indefinitely mothballed pending the creation of a national depository where they can be sent. Those casks sit on a concrete pad some 23 feet above mean water level.

“The existing ISFSI pad was constructed with a capacity of 40 dry storage casks, which is administratively limited to a capacity of 38 casks to allow for cask movement and access,” Nuclear Regulatory spokesman Neil Sheenan wrote in an email to The Times. “Pilgrim will need 61 casks total to hold all the spent fuel currently in the reactor and the spent fuel pool; therefore, the company needs to construct a larger independent spent fuel storage installation (ISFSI) pad. Entergy plans to build an ISFSI pad at the Upper Pad location.”  

Sheenan wrote construction on the new pad is expected to start midway into 2019. The pad will have a 70-cask capacity, will be 75 feet above mean sea level, and roughly 700 feet from the shoreline.

“The company plans to complete the fuel transfer process from the spent fuel pool to the ISFSI in 2020–2021,” he wrote. “There are 1,156 fuel assemblies stored in 17 dry storage casks on the ISFSI. There are 580 fuel assemblies in the reactor as part of the current operating cycle, and 2,378 spent fuel assemblies stored in the spent fuel pool. This is a total of 4,114 fuel assemblies onsite at Pilgrim at the time of shutdown.”

“Once it’s loaded and the lid is welded on,” Lynch said of the inner steel cask, “they take all the water out of it — it’s done underwater — they essentially vacuum all the water out … to a very, very low dryness, then they backfill it with helium and then reseal it.”

The casks are sturdy, as evidenced at Fukushima.

“Despite major damage to the rest of the power plant — including the meltdown of three reactor cores — nine dry casks holding 408 spent nuclear fuel assemblies went unscathed,” Alvarez wrote.



  1. Ok good. What’s a viable alternative? Giant Wind Turbines 20-30 stories tall above the oceans surface and littering the beauty of Nantucket sound?

    • Seacoast– Giant wind turbines seem to be at least one part of an alternative. Conservation could go a long way– like banning incandescent light bulbs. For some reason however, republican legislators blocked that one back in 2014. And really, do people need to leave their 200 watt floodlights on all night ? I spent months a few years ago harassing the postmaster in V.H to somehow turn the lights off in the parking lot during the day. Does anyone really need a house over 20,000 square ft ? We waste power at a staggering level– If you have to look at some wind turbines, too bad.
      And, by the way, I would be fine with nuclear pebble bed reactors.

  2. The danger is a shortage of power. I like burning garbage for power. They seem to have it down to where nothing is released into the air and the only problem is the toxic ash. They want to be able to break down the minerals in the ash. I have plenty of garbage.

    • Red sox– trash to power is a great concept– years ago , I took a tour of a Whelabrator plant in new Jersey– i was quite impressed. I am sure the technology has improved since my 1986 tour.
      But here is what I see– the process can be improved by educating the public and improving the waste stream process– the concept of putting all recyclables into one bin is crazy– the public can be educated– for instance, glass bottles and metal cans only slow down the process of producing electricity from trash. reducing the moisture content of municipal solid waste (msw) should be easy, but
      the towns seem to have no interest in addressing that issue.
      Paper should not be mixed with glass — one produces heat, one absorbs heat–
      Sometimes, we disagree, but you seem to have some practical common sense, and for that, I respect you .

  3. It’s truly a sad day. Forty seven years of clean, safe, affordable energy will be missed. The alternatives are far more expensive hurting the most disadvantaged in our society.

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