Decommissioning
After the explosion at reactor four, the remaining three reactors at the power plant continued to operate. In 1991, reactor two suffered a major fire, and was subsequently decommissioned. In November 1996, reactor one was shut down, followed by reactor three on December 15, 2000, making good on a promise by Ukrainian president Leonid Kuchma that the entire plant would be closed.
Even after the last reactor shutdown, people continue to work at the Chernobyl plant until reactor units 1, 2, and 3 are totally decommissioned, which is expected to take years. The first stage of decommissioning is the removal of the highly radioactive spent nuclear fuel, which is placed in deep water cooling ponds. However, storage facilities for this are not suitable for long term containment, and those on site do not have the capacity for all the spent fuel from units 1, 2 and 3. A second facility is planned for construction that will use dry storage technology suitable for long term storage and have the required capacity.
Removal of uncontaminated equipment has begun at unit 1 and this work could be complete by 2020–2022.
The remains of reactor unit 4 will remain radioactive for some time. The isotope responsible for the majority of the external gamma radiation dose at the site is Caesium-137 which has a half-life of about 30 years. It is likely that with no further decontamination work the gamma ray dosage at the site will return to background levels in about 300 years. However, as most of the alpha emitters are longer lived, the soil and many surfaces in and around the plant are likely to be contaminated with transuranic metals such as plutonium and americium, which have much longer half-lives. It is planned that the reactor buildings will be disassembled as soon as it is radiologically safe to do so.
Read more about this topic: Chernobyl Nuclear Power Plant