|Fig. 1: Chernobyl site before shield. (Source: Wikimedia Commons)|
On April 26th, 1986, an unauthorized experiment was conducted at the Chernobyl nuclear power plant in Ukraine. This caused an explosion on the fourth reactor, which is pictured in Fig. 1.  At least five percent of the reactor core was released into the atmosphere. Acute Radiation Syndrome (ARS) from the nuclear fallout affected 134 on-site clean up personnel. In total, the Chernobyl reaction explosion killed thirty people.  Two people died on the night of the incident because of the blast, and twenty-eight died within two weeks from ARS. Many more individuals were affected by the incident due to exposure to radioactive Iodine (I-131). The National Cancer Institute (NCI) uncovered a dose-response relationship between I-131 and thyroid cancer. This means higher absorption of I-131 increases risk for thyroid cancer. 
Increased rates of thyroid cancer and leukemia were a major concern after the Chernobyl incident. In 2003, the International Atomic Energy Agency (IAEA) established the Chernobyl Forum. The Chernobyl Forum's expert group on health was run by the World Health Organization (WHO). In 2005 they reported that aside from an increase in thyroid cancer incidence, there is no major evidence of a public health impact attributable to radiation exposure fourteen years after the incident. There is no scientific evidence of increase in overall cancer incidence or mortality or in non-malignant disorders that could be related to radiation exposure.  Yet, workers who were exposed to high levels of radiation, still have increased risks of cancer in the long term.
|Fig. 2: Chernobyl site with New Safe Confinement shield. (Source: Wikimedia Commons)|
Immediately following the incident, a concrete structure was built to enclose reactor four, so that other reactors could continue operating. Presently, about 200 tons of radioactive debris is improperly contained. Long-term clean-up efforts for Chernobyl in the 1990s focused on improving the remaining reactors. Over $400 million USD was spent in this project. Reactor three continued to be operated due to energy shortages, and reactor one and two were shut down after turbine hall fires in 1997 and 1991 respectively. In 1995 it was announced that all Chernobyl reactors would be decommissioned by 2000. 
In the end of November, 2016, a New Safe Confinement (NSC) building was completed, and this is pictured in Fig. 2. This large structure is a steel arch. It spans 275 meters in length and is 108 meters high. It will cover the remains of reactor four and the 1986 concrete structure. In total, the structure weighs 36,000 tons and is a ground-breaking engineering feat. The NSC is the largest land-based moveable structure ever built. Also, since the NSC is mobile, it will allow engineers to remove radioactive materials from the reactor. The European Bank for Reconstruction and Development states the total project cost is 1.5 billion euros. 
© Alison Jahansouz. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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