A government scientist overseeing the cleanup of the crippled Three Mile Island nuclear reactor estimated Tuesday that as much as 70% of the material in the core turned to liquid during the March, 1979, accident.
That material included fuel, parts of the core structure and the tubes in which the fuel is contained, said Donald McPherson of the Department of Energy. He said between 5% and 10% of the fuel itself melted, after reaching 5,100 degrees. Much more--perhaps 60%--began to liquefy after reaching 3,050 degrees, he said.
McPherson's estimates came 13 months after the first public disclosure that uranium fuel had melted during the accident. Previous studies indicated only that some metal parts in the core had melted. Industry critics and nuclear energy opponents said the 1985 finding meant the accident was more severe than had been believed.
General Public Utilities Nuclear Corp., which operates the Pennsylvania plant, has refused to estimate how much fuel or core matter melted.
McPherson testified at an NRC hearing on the cleanup.