Operators trying to control the Three Mile Island nuclear power plant accident repeatedly drew the wrong conclusions from a flood of conflicting information and were hampered at every turn by equipment glitches and seemingly malicious fate, the Nuclear Regulatory Commission was told yesterday.
The NRC's special task force on the March 28 incident in Pennsylvania, releasing its first interim chronology of the near-disaster, reported that:
An operator inadvertently blocked with his body the view of indicators that would have told him two crucial feedwater pump valves were closed. NRC sources explained after the meeting that the operator was "a big man with a large belly that hung over the instrument panel."
Listening through an amplifier system to gurgles and thumps within a steam generator, operates decided the noises meant there was water inside, when in fact the generator was boiling dry.
The computer printout of event during the crisis, similar to an airline flight recorder, jammed for nearly 90 minutes at the height of events. It was running two hours behind and eventually much of its data was lost altogether.
After operators were ordered to don respirators and face masks to guard against radiation, they were unable to talk to each other.
Ordered to evacuate the control room of Unit 2 for the adjacent control room of Unit 1, only a few operators did so, and those who went left the door open.
In the midle of crisis, when fuel damage was occuring for lack of cooling water, operators kept the pumps off from fear that vibrations would damage the pumps. "There was a general feeling that there must be something wrong with the (temperature gauges), that the temperature couldn't possibly be that high," reported chief investigator Robert Martin.
The NRC's regional headquarters did not learn of the accident until 36 minutes after Three Mile Island officials called, because the headquarters director was stuck in a traffic jam and could not respond to the answering service beeper..
The General Accounting Office, meanwhile, said in a report issued yesterday that human error in nuclear plant control rooms is a problem not limited to Three Mile Island.
Noting that mistakes by operators are common causes of technical problems at nuclear plants around the nation, the GAO criticized the Nuclear Regulatory Commission's rules governing the training and licensing of operating personnel.
The report said that about 90 percent of the applicants for licenses to be control room operators pass the qualifying examination on the first try, prompting the GAO to question whether NRC's test is too easy. The GAO also noted that the commission does not require utilities to report names of operators who commit technical errors. Thus the government cannot monitor the competence of the operators it has licensed.
At Three Mile Island, yesterday's chronology revealed, more than 8,000 gallons of radioactive water leaking through a pressurizer valve that was stuck open went directly to the unprotected auxiliary building. It did not, as was once thought, have to overflow the tank in the reactor building that was meant to catch it-since the tank valve inexplicably was open.
Further, a valve in the auxiliary building tank also was open, having been broken before the accident began, so radioactive water ran out onto the floor. Vents from this building were the major source of radioactivity in the area around Three Mile Island.
The chronology showed that two crucial feedwater valves that permit emergency cooling water to flow to the reactor routinely had been closed three times a month for the preceding year. Shutting both valves at once violates NRC rules. Martin said, for the very reason that occurred at Three Mile Island: They were wrongly left shut and water was not available for fully eight minutes when the emergency occurred.
"We consider the test procedure to be deficient," Martin said, adding that his office is checking to make certain that no other nuclear plant has such a procedure.