From Three Mile Island to Fukushima Daiichi, a look back at what we’ve learned

Three Mile Island. Chernobyl. Fukushima Daiichi. These three sites have been the setting for the most major reactor accidents in world history and have become synonymous with some of our worst fears involving nuclear power gone wrong. To humans, the greatest health risk posed by nuclear energy generation is the possibility that radioactive subatomic particles could enter the body and cause cancer or genetic diseases in a person’s offspring. There have also been more nuclear reactor accidents then the three aforementioned events; the U.S. has been the site of four nuclear reactor accidents, one of which, SL-1 at Idaho Falls, ID, in January 1961, actually resulted in the immediate fatalities of nuclear power plant workers.

Any reader, however, who might see any of the above as proof that the nuclear power beast is too risky to tangle with should note that those accidents, and the relatively few fatalities which they’ve caused, are the lone blemishes on an otherwise perfect record for nuclear power. In all, the world’s nuclear power plants have accrued a total of 16,000 cumulative reactor-years of commercial operation and yet there have only been 12 total nuclear power reactor accidents around the entire globe, far fewer than the total number of coal or gas mining explosions the world has experienced over the years. In our ongoing series looking at nuclear power’s potential, prompted by Japan’s short return to nuclear power after its 2011 disaster, we’re taking a quick look back at three major nuclear reactor events to see what the actual fallout has been from those accidents and if we’ve learned our lessons adequately enough to charge forward with making nuclear power a great part of America’s clean energy portfolio.

Three Mile Island: A Dog With A Lot of Bark, But No True Bite

On March 28th, 1979, a chain of events began in reactor #2 on Three Mile Island, a nuclear power station located near Harrisburg, PA, which led to the world’s first major nuclear reactor radiation threat. Often people can bemoan Murphy’s Law a little too liberally with a man-made disaster but this accident really did involve just about everything that could have gone wrong with a nuclear meltdown scenario.

At 4 AM on the day in question, a minor malfunction in a cooling circuit caused an automatic shutdown of reactor #2 and the opening of a coolant relief valve to ensure that pressure levels within the reactor stabilized, as it was designed to do. However, the valve remained opened instead of closing after 10 seconds, allowing coolant to continue bleeding. Power plant crews were unaware because there was no sensor to indicate that the valve was still open; sensors did indicate that coolant pressure levels were within the proper range so it was assumed that the reactor would operate just fine.

When warning alarms started to alert the Three Mile Island crews, they saw that water pressure levels were rising, which their training told them was an indication that there was too much coolant. Of course, the opposite was actually true, so when the amount of emergency cooling water being pumped into the reactor’s primary system, which only made matters much, much worse. A buildup of steam caused power plant crew members to turn off water pumping equipment, further exacerbating the reactor core eating problem. Unlike Chernobyl and Fukushima, Three Mile Island is the only nuclear reactor event which involved severe meltdown of the nuclear reactor’s core, which could lead to nuclear meltdown releasing incredibly large amounts of radiation to the outside world. Half of reactor #2’s core had melted in the early stages of this event.

The high-pressure injection of water into the reactor cooling system didn’t start happening until late afternoon on the nuclear event’s first day. The partial meltdown, along with miscommunication between public agencies, created a politically tense situation that led to fears of a massive evacuation of the area. This never occurred, of course, and it’s also interesting to note that Three Mile Island is the only major nuclear event where the containment building remained intact and contained nearly all of the radiation created by the event, save for small amounts that leaked when pressure was vented from the reactor. Despite the political backlash against nuclear energy created by this event, any adverse health effects have been deemed negligible by many organizations, including the Environmental Protection Agency, the Department of Energy as well as many state and independent groups.

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Chernobyl: A Prime Example of Soviet Mismanagement

The only human fatalities caused by radiation leaking from a nuclear power plant after a reactor disaster were a result of an explosion at the Soviet Union’s nuclear power plant in Chernobyl, now in Ukraine, on April 26th, 1986. In what is perhaps the largest Communist blunder ever, poor reactor design and misguided crew decisions to violate safety protocols led to the world’s next major nuclear power plant disaster.

Part of the Chernobyl reactor explosions can be chalked up to a power plant relying on some fairly risky design features. The Chernobyl plant had an unusual design known as reaktor bolshoy moshchnosty kanalny, or RBMK, which was developed by the Soviet Union. enables fuel bundles to be refilled without requiring reactor shutdown. However, unlike Western nuclear reactors which use steam to control neutron activity and reduce power, the RBMK configuration created extra free neutrons which increased the reactivity of the entire system, especially when the plant operated at low energy levels.

So of course, given these facts, it would seem to make no sense whatsoever to operate the RMBK nuclear reactor at low power with most of the safety shutdown mechanisms disabled. But that’s exactly what happened in late April 1986 when plant operators began testing the amount of time that turbines would continue to supply power to main water circulating pumps if the main electrical supply was cut. In violation of technical protocols for plant operation, crew members removed many of the reactor’s safety mechanisms prior to this test. A dramatic power surge led to a sudden increase in temperature damaged fuel channels and control rods and, ultimately, caused a steam explosion that killed two workers. A second explosion caused by ruptured pressure tubes exposed the reactor core directly to the surrounding environment.

First responders to the nuclear power plant emergency received an incredible amount of radiation, as much as 20,000 millisieverts (mSv) on the first day alone; around the world, people experience daily background radiation which typically only ranges between 1.5 mSv and 3 mSv per year. By the end of July, there were a total of 28 deaths at Chernobyl caused by radiation, six of them firefighters sent in to combat early blazes which lasted up to 10 days after the explosion.

A concrete containment structure was installed to quarantine the Chernobyl reactor core from its surrounding environment and a total of 116,000 people were evacuated from the region. A new structure  Again, it appears that the worst long term health effects were the mental traumas suffered by those living with a new fear of nuclear power. A 2000 report released by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) on the health of those affected by Chernobyl radiation found no discernible increase in radiation-related diseases, including cancers. In 2011, Ukraine reopened the containment zone around Chernobyl as a tourist attraction which receives about 10,000 visitors each year according to estimates from the company operating the site.

Fukushima Daiichi: Sustaining the Quake but Lost in the Waves

On Friday, March 11th, 2011, about 45 miles off of the eastern coast of Japan at 2:46 PM local time, a magnitude-9.0 earthquake triggered a catastrophe that would lead to the immediate deaths of about 19,000 people as well as this generation’s nuclear disaster: Fukushima Daiichi. This is one of the largest quakes in recorded history, causing two tectonic plates to slip an incredible distance of 50 meters (164 feet) past each other. The massive tsunami that it spawned, left nuclear power plant crews reeling as they tried to handle a natural disaster for which it was poorly prepared.

Fukushima Daiichi was built during the 1960s at a time when conventional scientific knowledge, based largely upon the results of the 1960 Valdivia quake, a monster magnitude-9.5 earthquake that hit Chile and still holds the record for largest recorded magnitude during an earthquake. To stabilize nuclear power plant structures, all Japanese plants are built on rock, and Fukushima Daiichi had its reactors 10 meters above sea level and its seawater pumps 4 meters above sea level to provide some protection against a tsunami caused by a quake. However, Japan had been visited by multiple tsunamis measuring over 10 meters in the century leading up to the nuclear power plant disaster. Although power plant countermeasures had been suggested, no serious remediation projects were underway by the time of the 2011 tremor.

Despite Fukushima Daiichi and its sister plant, nearby Fukushima Daini, experiencing quake forces which were greater than they were rated to withstand, all reactor buildings held firm. It was the resulting tsunami hitting less than one hour after the tremor that would cause the most major problems. At 3:42 PM local time, and then again at 3:50 PM, the Daiichi plant was hit with with tidal waves which damaged pumps for the residual heat removal (RHR) cooling system and put the facility into an electrical blackout. An evacuation order was issued the day of the event for all people living within two kilometers (1.25 miles); the evacuation zone would be increased to 20 km (12.5 miles) by Saturday evening and about 135,000 people left their homes. Over the course of less than a week, a series of three hydrogen explosions caused major damage to the plant and leaked radiation to the environment.

Although the 2011 earthquake caused a major loss of life and spawned a great amount of nuclear fear, it appears as if the current health effects of leaked radiation are just about nil. A report issued one year after the disaster by the American Nuclear Society found that only six workers out of nearly 15,000 monitored employees received doses of radiation in excess of the maximum legal emergency dosing level of 250 mSv. Currently, the highest reported radiation level from any monitoring post located within the Daiichi plant is less than 3.5 microsieverts (µSv) per hour, according to the Tokyo Electric Power Company (TEPCO) which operated the plant. To this point, more deaths have been caused by the mental and physical burden of evacuation than any effects from radiation. By February 2014, more Fukushima residents had died from displacement-related stress, lack of hospital care and suicide than the original earthquake and tsunami.

Conclusions: Could It Happen Again?

In our third and final piece in our nuclear power series, we’ll take a closer look at contemporary nuclear power plant designs and what the current risks are for nuclear power generation. But is there reason to believe that we can tame the nuclear beast, or are we doomed to repeat these events and spoil more of Earth’s precious land resources?

There are only 11 RBMK reactors operating in the world, all of them located in Russia, and major modifications were made to all Soviet RBMK reactors after Chernobyl. Rest assured, new nuclear plants will not adopt the old RBMK design; coupled with proper emergency training for nuclear plant employees, only areas of the former Soviet Union would be at any risk of that particular event repeating. Three Mile Island almost became a nuclear meltdown and yet no significant radiation was released; local residents received a radiation dose about one-sixth the amount of a typical chest x-ray scan. The fact that no one was evacuated from Harrisburg or the surrounding areas may have actually saved lives to judge by the evacuation-related deaths at Fukushima and related health issues at Chernobyl. Except for Pacific Rim fault lines running along the western coast of North America, there are few places in the mainland U.S. which pose a significant earthquake and tsunami threat to nuclear power reactors.

It’s also pretty telling that even with these disasters, nuclear power plants have killed far fewer humans than other electricity generation systems. In 1975, failure of the Shimantan/Banqiao dam released 15.738 billion tons of water into China’s Henan province, killing 171,000 people. Decades earlier, China was also the setting of the world’s worst coal mining disaster when an explosion in an underground mine killed 1,549 people in Liaoning province. And for all the fears of radiation leading to disease and early mortality, there are many more deaths attributable every year to fine particle pollution from coal-powered energy plants.

In future articles on this topic we will take a look at the evolution of nuclear technologies, as well as the safety features of newly proposed nuclear power plants and how those projects can help reduce America’s dependence on both fossil fuels and foreign energy resources.