Bob Mentzer (junior-computer science) remembers the Three Mile Island accident that happened 10 years ago today. Living about seven miles from the plant, Mentzer, then in elementary school, evacuated with his family.

"My grandmother took my sister and me to Altoona," Mentzer said. "We didn't understand what was happening."

At that time, scientists did not understand what was happening inside the TMI Unit 2 reactor either. Today, 10 years later, they are still studying the accident and attempting to clean the plant. Total cleanup costs are expected to reach $973 million, said Doug Bedell.

Bedell, public information manager at TMI, said the nuclear industry had prepared itself for major system problems such as pipes breaking during earthquakes but had not prepared itself for the series of unforeseen, unrelated minor failures that resulted in the TMI accident.

At TMI now, the damaged Unit 2 reactor will never function again. Unit 1, however, is still operable and can supply a city of about one million with electricity.

Various citizens' groups today are still skeptical about the safety of TMI. For example, according to the York Dispatch, members of Concerned Mothers and Women of TMI say they no longer have faith in the government or in General Public Utilities, the owner of the TMI plant.

The accident in Unit 2 began at 4 a.m. on March 28, 1979 when the plant automatically shut down because a pump stopped working, according to information from GPU.

Pressure and temperature inside the plant built up and, acting as designed, a valve opened to relieve the pressure and temperature. Water and steam flowed through the valve, out of the reactor and into the basement of the reactor building.

As temperature and pressure inside the reactor returned to normal, the valve should have closed but did not. Unknown to plant operators, the valve remained open for over two hours, allowing needed coolant water to escape from the reactor core.

Two high-pressure pumps began flooding the system with cool water, but a plant operator, misreading the warning signals, turned off one pump and slowed down the other.

Without the coolant water, the reactor core temperature became higher and higher until the core finally collapsed and the uranium fuel rods partially melted, contaminating the system with radiation.

Threats of a meltdown and an explosive hydrogen bubble in the reactor core caused as many as 200,000 people living within 50 miles of the plant to flee the area. Gov. Dick Thornburgh advised pregnant women and children to evacuate.

The accident was contained and recent studies have shown the public was not subjected to dangerous levels of radiation at any time during the course of the accident.

However, the effects of the accident have continued to reverberate throughout the industry for the past decade.

After 10 years, GPU is now in the final stages of cleanup and expect Unit 2 to be fully decommissioned and in long-term storage by the end of 1990, Bedell said.

"We're in the final phase of removing the fuel and damaged core," Bedell said. "After cleanup, the plant will be as clean or cleaner than a normal plant at the end of its life. Better than 99 percent of the reactor fuel will have been removed. The 1 percent remaining will be fixed in place and safe."

The 1 percent of radioactive fuel that remains will be in the walls of the basement of the containment building which was flooded with contaminated water. A robot has been cleaning the area, but some radiation will remain, Bedell said.

"It was the industry's inevitable accident," Bedell said. "It was an enormously costly experience for the company and industry, but some benefits have come out."

GPU estimates the accident will cost a total $973 million with $921 million having already been spent by January of this year. GPU also lost an additional $14 million per month from the shutdown of Unit 1 from 1979 to 1985, Bedell said.

Leon Lowery, a lobbyist at the Environmental Action Foundation in Washington, D.C., feels the greatest lesson learned by the industry from the TMI accident is one of funding.

"The industry is now extremely reluctant to invest," Lowery said. "There hasn't been a new plant since 1979."

E. E. Kintner, a GPU Nuclear spokesman at a recent conference of the American Nuclear Society, said the accident was "a shock badly needed."

"The accident at TMI-2 resulted in a dramatic rethinking by all parties about how nuclear plants should be designed, built and operated," Kintner said.

Lowery said the safety regulations developed by the Nuclear Regulatory Commission after the accident are still not enough.

"The NRC imposed stricter regulations and then backed away. They shouldn't be considering cost, but they are," Lowery said. "This is an inherently dangerous technology. It's not a question of how much safer but a question of how not so unsafe."

After the TMI accident, the NRC introduced many new safety regulations. Recently, the commission has been reducing the standards, viewing them as unnecessary, said Edward Klevans, University department head and professor of nuclear engineering.

Forrest J. Remick, chairman of the NRC Advisory Committee on Reactor Safeguards, University associate vice president for research and professor of nuclear engineering, said, "Perhaps the most important lesson we learned from TMI is that while this demanding technology can be handled safely, it requires a more disciplined, professional approach and constant diligence."