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A snail’s pace — by design

Entergy offers look at ‘slow, deliberate’ move of spent nuclear fuel at Vermont Yankee site

VERNON—Despite a late start, administrators say Vermont Yankee’s $143 million fuel storage project is on schedule to finish by the fall of 2018.

That’s not to imply, however, that anything related to the movement of radioactive spent fuel is happening quickly at the idled Vernon nuclear plant.

In fact, as Vermont Yankee Construction Manager Ken Swanger watched a massive cask transporter roll along at 0.25 mph on a recent afternoon, he seemed to relish the snail’s pace of the project.

It is by design “a very slow, deliberate process,” he said, resulting in just one finished fuel storage cask per week.

“Everything’s choreographed, written out, step-by-step,” Swanger said.

Though Vermont Yankee has been dormant since the end of 2014, most of the plant’s 3,880 spent fuel assemblies are still kept underwater inside the reactor building.

The goal of Entergy’s current fuel move campaign, performed under a contract with cask manufacturer Holtec International, is to get all of those assemblies inside sealed casks by next year.

For the fuel move to be finished on schedule, it will be necessary to place some of Vermont Yankee’s spent fuel in casks before the standard five-year cooling period elapses. That would require a special ruling from the federal Nuclear Regulatory Commission, which is still reviewing the matter.

There are safety reasons for the fuel move: The so-called “dry casks” are considered more stable and more secure than the plant’s cooling pool.

But there are also corporate and financial motivations driving the project.

Prerequisite to sale

Finishing fuel storage is a prerequisite for Entergy’s proposed sale of Vermont Yankee to NorthStar Group Services by the end of 2018. Also, Entergy wants to shrink the size of the plant’s protected area when the move is finished, a modification the company says could save $1.2 million per month.

Though much is riding on the fuel move’s completion, Entergy got a later-than-expected start this year as work began in June rather than April.

But Vermont Yankee Decommissioning Director Jack Boyle says the project is on track for completion in the third quarter of 2018 “in spite of the loss of a couple months.”

“We’ve got an adjusted target,” Boyle said in an interview at the plant. “We originally targeted doing 27 [casks] by the end of this calendar year. Because we got started about two months late, we’re now targeting 19 this calendar year.”

That would leave an additional 26 casks to be loaded in 2018. With the exception of extreme weather and a break for the holidays, Swanger said crews can work through the winter in order to meet that goal.

The only requirement is that “you’ve got to be above 10 degrees outside, and then [clean off] the ice and snow,” Swanger said.

Boyle also noted that, although the schedule generally calls for loading one cask per week, work could be accelerated to five or six casks per month if needed.

At the same time, the process of loading and transporting a cask to a concrete storage pad is methodical and drawn-out.

While some residents have raised concerns about moving radioactive fuel with Vernon Elementary School nearby, Vermont Yankee administrators have argued that specialized equipment and training, multiple layers of oversight. and experience from prior projects should assuage such concerns.

Plant officials offered a glimpse of the process on Aug. 4, as crews moved Vermont Yankee’s 19th loaded cask — the sixth of the current campaign.

Prior to the move, that cask had been a work in progress for the better part of a week.

Workers first load 12-foot-long spent fuel assemblies into a tall, stainless steel inner cask. That happens underwater inside the spent fuel pool, and then the cask is dried and placed inside Holtec’s massive steel-and-concrete “overpack” container.

That container, weighing about 200 tons when loaded, is pulled through an airlock and into the attached containment access building. That’s where workers wearing white hard hats spent an extended period of time securing the cask to “Cletus,” a tracked transporter weighing approximately 80 tons.

After making a painfully slow turn to exit the building, the machine moved at a leisurely pace toward the storage pad, with the cask suspended about 9 inches off the ground.

Along the way, Swanger pointed out batches of sand spread on the haul path to protect the pavement from Cletus’ weight and steel tracks.

Taking about 20 minutes to cover roughly 150 yards, Cletus turned and rolled up a ramp to the storage pad where 18 loaded casks already were stashed. Then crews began the slow process of lowering the cask to the pad and unbolting it from Cletus.

On the property for decades to come

Vermont Yankee loaded a total of 13 casks in 2008, 2011, and 2012. Those, plus the 45 to be loaded in the current campaign, will bring the total to 58 and necessitated the construction of a second storage pad adjacent to the first.

Due to the federal government’s failure to find a centralized disposal site for high-level nuclear waste, Vermont Yankee’s fuel will remain on the property for decades and possibly longer. It will fall to Entergy — or, if the plant sale is approved, to NorthStar — to secure and maintain that fuel.

Storing spent nuclear fuel is a costly proposition, and nuclear licensees routinely sue the federal government to recover some of those costs. But Swanger said the casks themselves are relatively low-maintenance.

“There are no moving parts. There’s no energy source,” he said. “What it is, is a giant chimney.”

He was referring to the fact that the spent fuel gives off heat via a vent in each cask. That’s why the temperature at the top of a cask at Vermont Yankee is 60 degrees warmer than the air at the bottom.

“We have a temperature monitoring system that monitors inlet/outlet temperatures on all of these casks individually,” Boyle said.

The sealed casks also emit radiation, though plant administrators say it’s a small amount. Swanger said the dose at each cask is currently about 30 microrem.

“We measure doses in millirem,” he said. “A microrem is one-thousandth of that.”

To put those numbers into perspective, the NRC says an average American is exposed to about 620 millirems of radiation annually.

The dose is even lower at Vermont Yankee’s fence line. But Swanger said administrators will be taking additional steps to further shield the plant’s western fence — the side facing Governor Hunt Road and the elementary school.

“We’re going to put the oldest, coldest cask here to the west, since we’re protecting that [boundary],” he said. “And the hottest casks will go to the east. They self-shield.”

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Originally published in The Commons issue #421 (Wednesday, August 16, 2017). This story appeared on page C1.

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