From Camping to Glamping: Three Mile island

September 27, 2016

At the time of the nuclear accident a friend of mine had family in the area and I remember the fear of the unknown effects on their future health. I want to inform those of you who are too young to remember, that this happened and was a real scare.

Three Mile Island Nuclear Plant.

In March 1979, a series of mechanical and human errors at the Three Mile Island nuclear generating plant near Harrisburg, Pennsylvania, resulted in an accident that profoundly affected the utility industry. A combination of stuck valves, misread gauges and poor decisions led to a partial meltdown of the reactor core and the release of radioactive gases into the atmosphere. Although the health effects were not serious, the accident heightened public fears and led to the immediate shutdown of several plants. In addition, a moratorium on the licensing of all new reactors was temporarily imposed, significantly slowing the industry for several years.
Excerpted from http://www.history.com/topics/three-mile-island

Here's the technical explanation.

What went wrong? The accident began at 4:00 a.m. on March 28, 1979. For an unknown reason, the feed pump (in the turbine water loop; see the schematic below) stopped operating. Without this pump, the turbine water could not remove heat from the steam generator. When this happened, the control rods automatically dropped into the reactor stopping the fission process. However, the radioactive fission products still produce heat so the temperature and pressure started to rise. To reduce the pressure, the valve on the pressurizer, called the pilot-operated relief valve (PORV), opened. Up to this time, everything operated as designed. Drawing from Metropolitan Edison Co. “A Report to the Met-Ed Community” May 30, 1979 When the pressure in the pressurizer dropped to a prescribed value, the PORV was suppose to close; it did not. The accident was now underway. The control panel had an indicator that showed the valve to be closed, (i.e., power was going to the valve to close it) but there was no way to determine that the valve was actually closed. With the valve open, steam and water escaped the pressurizer; this water flowed into a drain tank (not shown in the schematic). When the feed pump failed, the emergency feed pump should have turned on to keep the turbine water flowing. That pump was tested 42 hours prior and was functional. However, to perform the test, workers must close a valve, perform the test, then open that valve. Apparently the workers forgot to open the valve so the emergency water did not flow. Now the reactor was losing water and getting hotter. With the loss of water (and no air or steam in the pressurizer) the pressure dropped. When the pressure dropped, some of the water in the reactor turned to steam. This had two major consequences; first it forced water into the pressurizer and filling that completely, and second, steam rather than water surrounded some of the reactor fuel. Steam does not conduct heat as well as water, so the fuel pellets heated up. In case of an accident, a nuclear power plant has tanks of water with pumps that can quickly introduce water to cool the reactor. One of these automatically started. This was noted by the operators, but then they looked at the indicators for the pressurizer, these indicators were telling them that the pressurizer was full of water (which it was because of the steam in the reactor core area). A full pressurizer means that the operators cannot control the pressure, so they tuned off the entering water. Now the situation went from bad to worse. About 100 minutes after the accident started, steam bubbles appeared in the coolant pumps, causing them to vibrate. Fearing a compete failure of these pumps, the operators turned them off. With no water flowing into the reactor and water and steam escaping the reactor, large portions of the reactor core became uncovered. With no water to remove the heat, the fuel pellets started to melt, resulting in a partial meltdown. Finally, one operator surveyed the data and concluded that the PORV was open, so at 6:18 a.m., they closed the valve and then introduced water into the reactor, thus ending the immediate emergency. However, between the time that the operators shut off the pumps and when the valve was closed, the core was uncovered, enough to cause some fuel to melt. In fact, at the time of the accident, nobody thought that a major portion of the fuel melted. When the reactor was opened months later, they were surprised to find that about 60% of the core actually melted. While the reactor core melting, the hot zirconium (that held the fuel) was reacting with the water. This chemical reaction produced hydrogen gas, which is combustible. Some of the hydrogen gas escaped from the reactor and into the containment building. The operators were unaware of the presence of hydrogen until something ignited the hydrogen about 2:00 p.m. The burn lasted for six to eight seconds, but did no damage to any systems in the building. However, the reactor vessel still contained hydrogen, but nobody seemed to address this problem in light of other, more serious, problems. When somebody gave it some thought two days later, the great fear was that the hydrogen might explode causing a breach of the reactor vessel and maybe of the containment building. Once the presence of hydrogen was verified, the hydrogen was sent though neutralizers and by the fourth day most of the hydrogen was gone. Actually the fear of an explosion was unfounded. To burn, hydrogen must combine with oxygen, but no oxygen was present in the reactor vessel. However, the fear of an explosion caused many of the public to evacuate the area around TMI. During these first few hours of the accident, all the action occurred in the reactor building. However, the water that escaped through the pressurizer valve had filled the drain tank and overflowed onto the floor in the Auxiliary Building. Because the core had been uncovered resulting in some core melt, radioactivity had escaped to the reactor water and some of that water was now in the Auxiliary Building. Some of the radioactivity was xenon and krypton (noble gases) and iodine. The gasses could not be contained so they soon leaked into the atmosphere, thus exposing the public to radiation from the radioactivity in the air. Although the release stacks on the Auxiliary building contained radiation monitors, they were designed for much smaller releases. Therefore the actual radioactivity that was released was never measured, but from later calculations, the scientific community estimated that about 17 million Curies* escaped the reactor and transported to the Auxiliary building. The Auxiliary building served as something like a holding tank which allowed some of the radioactivity to decay before entering the atmosphere. As a result, a little more than half, 9 million Curies, made it to the environment. As a result of these noble gas releases, the public received some radiation dose. The actual dose received by any one person will never be known, but experts, according to testimony in the TMI Litigation, gave limits in the 25 to 50 mrem range. (TMI Litigation Consolidated Proceedings, Civil Action No. 1:CV-88-1452; Judge Sylvia Rambo) Normal background radiation, excluding radon (cosmic rays, radioactivity in the body, and terrestrial radiation), is about 100 mrem per year in the central Pennsylvania area. (For further discussion on radiation dose and health effects, see Chapters 2 and 3 in “The 3 R’s; Radiation, Risk, and Reason”) In addition, researchers did not find any radioactive iodine from the accident in food and milk samples. The final result of the investigations into the doses indicate that population dose did give the public an increased risk of cancer, but at most, maybe one person may get a fatal cancer. For a more in-depth description of the accident, see the “Rogovin Report”. This is summarized at: http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html Excerpted from http://www.threemileisland.org/science/what_went_wrong/

For more information
http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html

Here's what the New York Times had to say at the time.

Radiation Is Released in Accident at Nuclear Plant in Pennsylvania

By Donald Janson

Special to The New York Times

By last night, officials of the Nuclear Regulatory Commission had still not determined the full extent of the radiation danger, but they said the amount of radiation that escaped was no threat to people in the area. Major amounts were released into the building housing the reactor, but workers were not believed to have been endangered.Middletown, Pa., Thursday, March 29 -- An accident at a three-month-old nuclear power plant released above-normal levels of radiation into the central Pennsylvania countryside early yesterday.

Still, the accident at the Three Mile Island Nuclear Power Plant, on an island in the Susquehanna River about 11 miles south of Harrisburg, was described as the worst ever at an American nuclear generating plant.

The precise cause of the accident was not determined. A Federal nuclear expert suggested last night that it stemmed from problems with filters in the plant.

Officials of the Nuclear Regulatory Commission said radiation outside the plant was far less than that produced by diagnostic X-rays.

Come of the 60 employees on duty were contaminated, a plant spokesman said, but they did not require hospitalization. And the 15,000 people living within a mile of the plant were not evacuated, although a 'general emergency' was declared.

The commission said that "low levels of radiation" had been measured up to a mile from the plant and that traces had been found in the air up to 16 miles away. The amount in the immediate area were described as above normal for the plant site but below what is considered dangerous to health.

Details Remain Unclear

William Dornsife, a nuclear engineer with the State Bureau of Radiation Protection, confirmed that the radiation was not expected to pose a serious health threat, but there was some concern that radioactive iodine, one of the isotopes detected by the monitors, could show up in cow's milk in a week or two.

Details of the accident were in dispute almost immediately. Commission spokesmen first said it appeared to involve not just radioactive steam from the cooling system, but "direct radiation coming from radioactive material within the reactor containment." Last night, however, one commission investigator said the radiation was being emitted from nuclear-charged water.

Jack G. Herbein, a vice president of the Metropolitan Edison Company of Reading, one of a number of utilities that operate the power plant, said the accident began with the failure of a valve in a pump in the cooling system.

But officials of the company that manufactured the pump, Bingham-Willamette Company of Portland, Ore., said that that could not have been the cause since "we have no valve in our pump."

And late last night an engineer with N.R.C. suggested that malfunctioning "polishers," which he said were "filters," were at fault, not a pipe or valve. He did say, however, that that was still "supposition."

Whatever the initial cause, a cutoff of the flow of water in the primary cooling system appears to have resulted in uranium pellets in the fuel rods melting or cracking, releasing radiation before control rods could be inserted to stop the nuclear reaction.

In Washington, Senator Gary Hart, chairman of the subcommittee on nuclear regulation, said that "some human error seems to have been involved in responding to the emergency situation." The commission informed him, he said, that "the emergency core cooling system was turned off prematurely, resulting in a partial blockage of water needed to cool the nuclear core and keep it under control."

The plant's backup system worked perfectly, Mr. Herbein said, but the overheating caused a rupture in a drain tank releasing radioactive steam. Because of the dangerous pressure buildup plant officials released some of the steam through the ventilation system.

Lieut. Gov. William Scranton 3d said the release of steam relieved "potentially dangerous pressure in the reactor chamber" but, because of a leak in the primary cooling system, "radioactive material was discharged into the air along with the steam." And late last night Federal officials said steam was still being vented to relieve the pressure.

Mr. Scranton also said the Department of Environmental Resources was not notified until after the discharges were halted at 1:30 P.M. He said the accident occurred at 4 A.M. and the releases began at 11 A.M.

When Mr. Herbein was asked about the delay in reporting the accident to the state and Federal authorities, he said that no escaping radioactivity was detected at first.

Part of the confusion over the exact chain of events was due to the inability of the monitoring team to inspect the reactor because of the high levels of radiation within the reactor dome. Based on readings taken outside, some N.R.C. officials said that levels inside the buildings were between 5,000 and 6,000 roentgens -- more than 10 times the lethal level.

However, company officials said those figures were too high.

Radiation Estimates Increased

Estimates of the amount of radiation escaping from the building were increased during the day, at one time reaching seven millirems. The rem is a standard radiation measurement that relates the strength of radiation (in roentgens) to the duration of exposure.

In a 5 P.M. statement, however, the commission said its maximum confirmed measurement, at a site a third of a mile from the plant, was three millirems, or thousandths of a rem.

The exposure from a standard diagnostic X-ray has been put at 72 millirems.

Scientists have held that exposure to manmade radiation should not exceed 170 millirems annually. At a news conference this afternoon Mr. Herbein reported a level of seven millirems at the plant, which would mean exposure to 168 millirems in 24 hours.

As company, state and Federal officials converged on the site, there were expressions of concern about the long-range effects of the radiation release.

Lieutenant Governor Scranton, who monitors energy matters for the state of Pennsylvania, said, "We are concerned most about radioactive iodine, which can accumulate in the thyroid, either through breathing or through drinking milk. Fortunately, we don't believe the risk is significant because dairy cows are on stored feed at this time of year."

He said radioactivity had been detected in small amounts in York, Cumberland, Dauphin and Lancaster Counties after the accident.

There was no radiation found in the river, Mr. Herbein said.

Company officials took pains to reassure the public.

"This is not a 'China Syndrome' type situation," said Blaine Fabian, a plant spokesman, referring to the possibility of a massive meltdown- with an uncooled nuclear reactor core burning hundreds of feet into the earth. The title of a current movie is derived from this slang expression used by scientists.

The nuclear generator, which was operating at its full capacity of 959 megawatts, is one of two at the site and was put in operation only on Dec. 30. The other, which had been shut down for refueling, was installed in 1974.

Our campground was not far from Three Mile Island and I felt compelled to go there and take some photos.