Like a parade of snorkelers, plastic tubes vent gases from the submerged metal canisters that house the remains of the melted Three Mile Island reactor core.

The 14-foot-long canisters are submerged in a pool of water inside Building 607 at Test Area North of the Idaho National Engineering Laboratory. The vents prevent a buildup of possibly explosive gases.The remnants of the reactor core that underwent a partial meltdown in a commercial power plant accident outside Harrisburg, Pa., in 1979 are helping scientists determine what would happen in a more serious accident.

"They have concluded that the China Syndrome may not be likely," said Douglas Akers, a nuclear chemist at the INEL.

The China Syndrome - a name borrowed from a 1979 movie about a fictional accident at a California nuclear power plant - is a theory that once a reactor core begins to melt down, the nuclear reaction within it will concentrate and increase in intensity, eventually burning through the floor of the reactor building and into the ground below.

But the $189 million studies of the partially melted Three Mile Island core show that only about 60 percent of the core was damaged and only about half of it melted, Akers said.

"Three Mile Island has provided the only full-scale severe accident research," he said.

The research has provided information against which other theories and research results can be cross-checked for validity. That has resulted in a number of safety modifications in commercial reactors.

"The impact Three Mile Island had on the industry was a very positive, significant impact," said Neil Burrell, the U.S. Department of Energy's Three Mile Island program manager.

Scientists involved in the Three Mile Island research think that rather than melting its way to China, a molten core would tend to contain itself within a partially melted crust of debris that would retain many of the highly radioactive by-products of the nuclear reaction.

The material was moved to the INEL from Pennsylvania in a heavily shielded railroad transport cask that weighs 80 tons when empty.

The final shipment arrived at the INEL April 19, bringing the total to 133,000 kilograms, or 60,455 pounds. The material now is in special canisters in a storage pool at the Test Area North.

The long-range plan for the destroyed reactor core is to move the debris to a federal high-level waste repository when one opens. But for now, the ruined core is stored in a building that has been labeled inappropriate for high-level radioactive waste storage by a government environmental assessment.

The 50-foot wide, 300-foot long room is equipped with remote cranes and manipulation tools to handle highly radioactive material. The facility also is researching dry storage casks to expand the spent fuel storage capacity in reactors at commercial power plants.