On March 28, 1979, the Three Mile Island Unit 2 (TMI-2) reactor near Harrisburg, PA had a partial fuel meltdown.
A July 17, 1979, article from the Washington Post reported that a study by the Bechtel Corporation estimated it would cost $405 million (with $25 million added for uncertainties) and take 4 years—until June 1983—to clean up after the incident and restart the reactor. This cost estimate corresponds to roughly $1 billion in 2011 dollars.
In fact, it took 11 years and 1 month to clean up the mess and NOT return the reactor to operation. And it cost twice as much not to restart the reactor as Bechtel thought it would cost to restart it.
The cleanup process is chronicled in the 1990 Electric Power Research Institute (EPRI) report The Cleanup of Three Mile Island Unit 2: A Technical History—1979 to 1990. The chronology in this report also shows:
- The TMI-2 reactor initially achieved criticality at 4:37 am on March 28, 1978. It was critical for the very last time at 4:01 am on March 28, 1979—36 minutes shy of its first birthday.
- A robot (named Herman) arrived at TMI two days after the accident. It took much longer for robots to arrive at Fukushima. President Jimmy Carter arrived at TMI two days later to assess the situation.
- Two weeks after the accident, Carter appointed the independent Kemeny Commission to investigate the accident.
- Workers first re-entered the TMI-2 reactor containment on July 23, 1980—nearly a year and a half after the accident.
- The processing of radioactively contaminated water (some 2.5 million liters) was completed on March 12, 1982, nearly 3 years after the accident. The amount of highly contaminated water at Fukushima is believed to be 25 times that amount.
- A video exam inside reactor vessel in October 1983—more than four years post-accident—finally showed the extent of damage to the reactor core.
- On June 28, 1984, workers entered the containment without respirators for the first time since the accident more than 5 years earlier.
- In January 1985 workers found that fuel particles from the damaged reactor core had been transported through the reactor coolant system to other parts of the plant.
- A video inspection on February 20, 1985, revealed that parts of the reactor core had melted and re-solidified in the lower region of the reactor vessel. This was the first confirmation of a partial meltdown.
- Three Mile Island Unit 1 reactor, which had been in a refueling outage at the time of the TMI-2 accident and had been scheduled to restart that same day, finally achieved criticality on October 3, 1985, more than 6 years after the accident.
- Pieces of damaged core from TMI-2 that had been loaded into special fuel canisters were moved from the reactor vessel to the spent fuel pool for the first time on January 12, 1986.
- By September 1987, eight and a half years after the accident, “over half” of the debris was reported to have been removed from the reactor vessel.
- On October 28, 1988, the chairman of the company that owns TMI announced the cleanup would cost $973 million (nearly $2 billion in 2011 dollars).
- TMI-2 was reported to be de-fueled on April 26, 1990, 11 years and one month after the accident.
The amount of time and money required to clean up Fukushima is expected to be much greater than that required for TMI-2.
The TMI accident affected a single reactor. The Fukushima crisis seriously affected 3 reactors and 4 spent fuel pools. The amount of damaged fuel at Fukushima may be greater than the total amount of fuel damaged in all previous nuclear accidents combined.
Since the TMI reactor was operating for the first time, it had not generated spent fuel and therefore had an empty spent fuel pool that could be used for holding post-accident wastes. The 6 spent fuel pools in the reactor buildings at Fukushima contain a total of nearly 800 tons of spent fuel, and a 7th common pool contains over 1,000 additional tons of spent fuel.
The cleanup at TMI included areas outside containment that were contaminated by airborne radioactivity. The cleanup at Fukushima must deal with contamination due to airborne releases and large amounts of highly radioactive water. As noted above, the amount of highly radioactive water at Fukushima is 25 times the amount that was processed at TMI.