The new system, dubbed High Thermal Performance Fuel, incorporates an improved grid design that would decrease the likelihood of fuel rods rubbing against their metal place holders inside the reactor.
Experts agree that the fuel change is less of a safety issue and more of a way for TMI Unit 1 to reduce costs and have the plant run more efficiently.
Bundled fuel rods, the primary energy source of a nuclear-powered plant, sit inside a grid-like reactor that resembles utensil holders found in some dishwashers.
When in operation, the reactor is flooded with rapidly moving coolant, which forces some rods to come in contact with the grid, said Neil Sheehan, spokesman for the U.S. Nuclear Regulatory Commission.
The metal-against-metal action can cause small, pinhole defects in the rods, resulting in the release of radioactive gas into the plant's reactor system, Ralph
DeSantis, a TMI Unit 1 spokesman, said.The release of those gases can increase radiation levels inside some rooms and other areas of the plant, he said. The increased radiation levels as a result of those rare leaks have not endangered plant workers, DeSantis said.
"We have had instances where we have had fuel defects," he said.
Regardless of the leaks, radioactive gases have not escaped the plant, so there hasn't been any danger to public safety, he said.
The estimated number of fuel defects inside pressurized-water reactors - the powerhouse used to run TMI Unit 1 - is 6.7 failed rods for every one million manufactured, Sheehan said.
Still, the leaks are costly to plants like TMI that need to spend additional time and money to decontaminate certain work areas, he said.
"It's a situation where it becomes a challenging work environment for workers at the plant," Sheehan said.
Rosa Yang, the director of the material and chemistry department at the Electric Power Research Institute in Palo Alto, Calif., said TMI's plans to install the improved rods is more of an economic than a safety issue.
A fuel assembly, which consists of about 200 fuel rods, costs roughly $1 million.
Sometimes, a plant might opt to replace an entire fuel assembly that might C1 have been damaged by grid-to-rod fretting, or metal-to-metal contact, she said.
On the surface, the improved fuel assemblies that AmerGen Energy plans to install at TMI Unit 1 look much like the bundles already installed within the reactor, DeSantis said.
The minor changes with spacing and design associated with the new system promises to reduce the occurrence of metal-against-metal leaks.
So far, the NRC has signed off to allow three other nuclear-powered plants, Davis-Besse in Ohio, Crystal River in Florida and Oconee in South Carolina, to run their reactors with High Thermal Performance Fuel.
The NRC must approve any significant change a plant plans to make to its operating license, Sheehan said. A change of a fuel type that includes plans to realign a reactor core ranks as notable modification to a plant's operation, he said. In all cases, the new fuel type has not increased the power output of the plants, but rather worked to reduce the wear and tear of reactor rods.
In March, AmerGen Energy filed a license amendment with the commission requesting the fuel change.
The NRC will review the request, run a technical review and host a public meeting before the commission will issue a decision, Sheehan said.
That process could last six months.
TMI Unit 1 official hope to install some of the new fuel during it refueling outage this fall.
"At TMI, we continue to look for the latest technology to further improve the plant," DeSantis said.
Reach Sean Adkins at 771-2047 or sadkins@ydr.com.
The U.S. Nuclear Regulatory Commission will host a public meeting at 10:30 a.m. April 30 at its headquarters in Rockville, Md.
The meeting will focus on Three Mile Island Unit 1's plan to install improved fuel within its reactor.
For details, call (301) 415-2481.