NRC Says Nuclear Accident Caused Reactor Core Damage

HARRISBURG, Pa.--New tests show that the core of the nuclear reactor at the Three Mile Island power plant which failed last month suffered grave damage in the early stages of the crisis, federal officials announced yesterday.

The Nuclear Regulatory Commission (NRC) said in its daily status report that in the first 15 hours of the March 28 accident, referred to as a "transient" period, large portions of the core were exposed when coolant water boiled into steam.

Although apparently none of the 100 tons of uranium fuel melted, the zirconium alloy cladding that surrounds the uranium rods was heavily damaged, the NRC said.

"It was during these periods of deficient cooling that extensive damage to the fuel elements occurred.... The highest fuel temperature during the transient is estimated... to be well below the 5100 degrees Fahrenheit fuel melting point," the report said.

Slow Cool

Technicians yesterday continued to cool the reactor core slowly as they prepared for an eventual cold shutdown. The main coolant water temperatures had fallen to 249 degrees by afternoon, a drop of one degree since Saturday.

The technicians were trying to lower the temperature to 230 degrees, but the cooling process is taking longer than anticipated.