At this time last year, the Omaha Public Power District’s Fort Calhoun nuclear plant was still running with a nearly full head of steam, and OPPD officials figured it would be five years before the last of its radioactive fuel would be removed from the plant’s on-site cooling pool.
On Tuesday, OPPD’s head of decommissioning told the electric utility’s board of directors that the 215,000-gallon spent fuel pool could be devoid of nearly 950 fuel assemblies in three years instead of five.
Compared with preliminary plans, the faster timeline means that about 100 more Fort Calhoun employees get to stay at the plant — where they’ll be cleaning up and tearing down radioactive components, among other tasks — instead of being cut loose and replaced with outsourced workers 20 to 30 years down the road.
(The method OPPD chose to decommission the plant has a maximum time frame of 60 years, but the utility plans on doing as much work as possible upfront, with workers who already work at the plant.)
“It will keep more employees on-site doing that work ... and we’re able to keep those folks doing the work we have to do anyway,” said OPPD President and Chief Executive Tim Burke.
The faster time frame for transferring the last of the plant’s nuclear fuel out of the pool is a product of technological improvements over recent years, regulatory procedures and careful attention to how fuel assemblies are loaded into what are called dry storage casks.
Spent nuclear fuel typically cools off for at least five years in steel-lined pools filled with 40 feet of specially treated water before it’s transferred into steel and concrete casks. The “industry norm” is 10 years, according to the federal Nuclear Regulatory Commission, the federal body charged with oversight and enforcement of the nuclear power industry.
“Five years is customary, but as more plants are decommissioning, some licensees are moving for faster decontamination and decommissioning, rather than waiting years,” said David McIntyre, public affairs officer at the NRC. “They want to get the fuel transferred to casks so they can dismantle the pool and the structures around it.”
The plan for Calhoun involves surrounding “hotter” assemblies — that is, those that have been in the spent fuel pool for a shorter time — with “cooler” assemblies once they’re placed in storage casks.
“It’s kind of like a big puzzle,” said Kailen Shores, senior nuclear design engineer at Fort Calhoun. “You want to minimize the dose (of radiation) so you insulate cooler bundles on the outside.”
It also helps that the majority of the plant’s spent fuel has been cooling for much longer than what was removed when the plant shut down last year.
Such casks are designed to eventually be shipped off to a permanent nuclear waste facility. Political wrangling has stalled the completion of such a facility in the U.S., however, which means on-site storage of spent fuel at facilities including Fort Calhoun is the norm.
Later this month, OPPD expects to get responses to a request for proposals for 30 new storage units at the plant site, from which it will select a vendor to build them. The NRC must then approve a request from that vendor to be sure its casks can safely contain the proposed configurations of spent fuel assemblies.
The sooner fuel is out of the pool — which depends on massive pumping systems that are subject to mechanical failure — and in sealed casks, the safer it will be, Shores said.
That also means costs to power the systems running and supporting the pool’s pumps will decline significantly.
In a typical month when the plant was generating electricity, it consumed about 25 megawatts of electricity; that consumption today is closer to 2 megawatts.
Then there are the employees.
There are 397 employees at Fort Calhoun today, slightly fewer than in recent months and about 100 fewer than were on-site six months ago.
“Our plan is to be down to about 350 by April of next year,” said Mary Fisher, senior director of decommissioning at the plant. “I think by the end of the year we will be down to a range of 380 to 390, so we’ll be fairly close to 350 by April and may even get there through attrition.”
In February, OPPD issued layoff notices to 33 employees, but Fisher told the board in March that enough employees were leaving the plant on their own that the utility was confident that it could avoid more layoffs for the rest of the year.
Fisher estimated that there would be about 300 employees at the plant by year-end 2020. About 700 people worked at the plant at its peak.