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30 July 2021

Chernobyl Nuclear Power Plant Decommissioning Project

On 26 April 1986, the Chernobyl nuclear power plant's number four reactor exploded, sending a radioactive cloud across much of Europe.
ISF-2 was completed in 2019 and commissioned in 2020. Credit: Holtec International.
From November 2020, Holtec started loading the double walled canisters at ISF-2. Credit: Holtec International.
ISF-2 was built at a cost of €400m. Credit: Holtec International.

The Chernobyl nuclear power plant’s number four reactor exploded on 26 April 1986, sending a radioactive cloud across much of Europe. Following the explosion, radioactivity with an intensity equivalent to 500 of the bombs that destroyed Hiroshima at the end of World War II was measured in the atmosphere.

In 2005, the International Atomic Energy Agency (IAEA) and World Health Organisation (WHO) reported that 56 people died directly from the incident, mainly accident workers. They estimated another 4,000 deaths among workers and local residents.

However, according to unofficial statistics, at least 15,000 people died as a direct result of the explosion.

The power station is still seen by critics as a time bomb, and work has been carried out ever since the explosion to try and make the site safe. The Ukrainian Government initiated a long-term plan to protect the Chernobyl shelter from radiation.

Chernobyl closure and construction

The work carried out at the site was considered unsatisfactory by the West. Chernobyl was operational for some time afterwards, as there was not enough generating capacity in Ukraine for its closure, and several more minor incidents occurred after 1986.

In 1991, following a fire, Reactor 2 was taken offline and decommissioned. The last reactor, Reactor 3, was switched off in 2000 to close the plant, after which the decommissioning of the three reactor units began. A shelter implementation plan (SIP) was chalked out to develop a programme for making the site of the nuclear accident safe. It is expected to cost €2.1bn, funded by contributions from more than 40 countries and organisations.

The European Bank for Reconstruction and Development (EBRD) set up the Chernobyl Shelter Fund in 1997 to support Ukraine in developing a temporary shelter over the destroyed Reactor 4 to make it safe and stable. The fund received more than €1.6bn from 45 donors and was closed in late 2020. It helped to support the decommissioning work at the site.

Some decommissioning infrastructure projects have been funded through bilateral aid, while two critical Chernobyl facilities, the Interim Storage Facility 2 (ISF-2) and Liquid Radioactive Waste Treatment Plant (LRTP), were funded by the Nuclear Safety Account (NSA).

Project decommissioning

Following the 1986 accident, the number four reactor at Chernobyl was encased in a giant concrete ‘sarcophagus’ to prevent further leakage of radioactive material. Hundreds of thousands of mobilised soldiers and civilian experts constructed the sarcophagus above the destroyed reactor, and the plant was re-opened in late 1986. A huge fire in the second reactor led to its closure in 1991, and in 1996, the number one reactor was shut down as it had reached the end of its lifespan.

The sarcophagus built in 1986 was considered unstable and needed further repair work. In December 2000, the US promised to contribute the largest G7 amount to repair the sarcophagus. Construction of a waste management facility began in 2001 for the treatment of fuel and other wastes from the decommissioned units one to three. A stabilising steel structure was extended in December 2006 to spread some of the load on the walls damaged by the explosion.

The fuel mass at the reactor has also been enclosed in EKOR, a radiation-resistant material developed by UK company Eurotech. The material was applied during March 2000 and is maintaining an isolation coating and seal of the pile, preventing further dusting and leaching of contamination into the environment.

After two months, EKOR exceeded the longevity of all previously applied materials, which degraded rapidly in the severe-radiation environment and lost isolation effectiveness.

The EKOR-encapsulated fuel pile has radiation readings in the range of 1,000 rads on contact, although EKOR has been laboratory tested to an accumulated dose of 10 gigarads without loss of physical properties.

In June 1999, Chernobyl Nuclear Power Plant (ChNPP) and a consortium led by Framatone signed a contract to build a facility to store spent fuel. In August 1999, ChNPP signed an agreement with a consortium led by Belgatom for a Liquid Radwaste Treatment Plant (LRTP). French firm Novarka built a giant new safe confinement around Reactor 4 under the SIP at an estimated cost of €1.5bn.

New safety confinement details

Collaborating with French construction companies Bouygues and Vinci, Novarka built a large, movable, land-based arch-shaped structure spanning 257m, to make the accident site safe for a lifetime of 100 years. With a total weight of 36,000t, the structure measures 162m in length and 108m in height.

The frame is a huge lattice structure of tubular steel members, supported by two longitudinal concrete beams. Its sophisticated ventilation system eliminates the risk of corrosion and can withstand a tornado. It covers the existing containment structure above the reactor and radioactive fuel. The structure was moved into place in November 2016, and the site was transformed into an environmentally safe and secure state by November 2017.

State law programme to decommission Chernobyl nuclear power plant

On 7 January 2010, the Ukrainian Government passed a state law to transform the Chernobyl shelter facility into an environmentally safe system in order to protect the surroundings from radiation. The programme is being executed in four stages.

In the first stage, nuclear fuel was moved to a storage facility in 2013. In the second stage, which will be completed by 2025, all the reactors will be deactivated. The third stage involves maintaining the reactors until radiation drops to an acceptable level and is envisaged to be completed by 2045. The fourth and final stage involves dismantling the reactors and clearing the site, which is expected to be completed by 2065.

The state law programme is being financed by the EBRD and other international donors.

In addition, a seminar was conducted by IAEA to discuss the decommissioning of the cooling pond, which was highly contaminated after the explosion.

In 1999, Framatome was selected by ChNPP for the construction of ISF-2, which was planned for completion in 2003. Due to design flaws and non-compliance to agreement terms, the contract was terminated.

In 2007, the US firm Holtec was selected to build the ISF-2 for storing the nuclear waste produced by the Chernobyl nuclear plant.

Holtec completed the first phase of the project, which involved the preparation of safety and environmental qualification documents that comply with Ukrainian standards, and in November 2010, Ukrainian authorities issued a positive safety conclusion on Holtec’s design.

The company was permitted to begin the final phase of the project in March 2011. The phase involved the supply of 231 double wall canisters (DWCs) manufactured at Holtec’s facility in Pittsburgh, Pennsylvania, US.

The facility’s construction and comprehensive pre-commissioning programme (cold tests) were completed in August 2019. In September 2020, the State Nuclear Regulatory Inspectorate of Ukraine (SNRIU) issued the License Permit to ChNPP to begin the commissioning of ISF-2.

In November 2020, Holtec’s technicians placed the first fully loaded DWC at ISF-2, while the second DWC was loaded at the facility in December.

In April 2021, SNRIU gave an operating licence to SSE ChNPP to retrieve undamaged used nuclear fuel from the ISF-1 interim used fuel wet storage facility.

The spent nuclear fuels will be disassembled, packaged in DWCs and moved to the new ISF-2 dry storage facility which is an intermediate storage facility. The ISF-1 facility has a limited-service life as it was not designed for long-term storage of the fuel.

ISF-2 was built at a cost of €400m through the cooperation of the international community, including the European Union, Belgium, Denmark, France, Germany, Italy, Finland, the Netherlands, Norway, Sweden, Switzerland, Japan, Russia, the UK and the US as well as the European Bank for Reconstruction and Development (EBRD).

ISF-2 and LRTP details

The ISF-2 will process, dry and cut more than 21,000 fuel assemblies from reactors one to three, which will be placed in DWC to store in concrete modules on site.  The company used DWC, the largest forced gas dehydration system and hot cell to dismember the conjugated RMBK fuel assembly.

The spent fuel will be securely stored for a minimum of 100 years. The existing fuel storage facilities can be decommissioned after the transfer of all used fuel to the ISF-2 facility.

The operational LRTP retrieves highly active liquids from their current storage tanks, processes them into a solid state and moves them into containers for long-term storage.

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