Chernobyl 1-3 enter decommissioning phase

The Chernobyl nuclear power plant in Ukraine has officially entered the decommissioning phase, following approval by the country's nuclear regulator. The first phase of decommissioning is the so-called final shutdown and preservation stage (FS&P), which is expected to take ten years.

On 26 April 1986, the Chernobyl plant suffered the worst nuclear accident in history when a power runaway event wrecked reactor 4. The three remaining reactor units, however, were vital to Ukraine's electricity needs and continued to operate for some years. Unit 2 shut down in 1991, unit 1 in 1996 and unit 3 in 2000. The decommissioning of units 1-3 is being carried out separately from that of the destroyed unit 4, which is expected to take many years longer to complete.

The move into the decommissioning phase for the first three units follows an order issued by the State Inspectorate for Nuclear Regulation of Ukraine (SNRC) that was announced on 9 April. SNRC said work will start on gradually bringing the three units into a 'conserved' state, beginning with FS&P. That permission follows issuance of a licence for decommissioning work at the site that SSE ChNPP, the state company tasked with managing the plant, obtained in March 2010. Public hearings on FS&P were held in 2013.

FS&P will be of "great positive significance" for areas of the Kiev region adjacent to the Chernobyl exclusion zone and for the northern city of Slavutych, in assisting their social and economic development, SSE ChNPP said in a statement on 9 April.

Work to bring the three units into a conserved state will be carried out in six stages between now and 2028. The first stage is to refurbish the water supply system for the plant's fire protection system. The second stage will involve the dismantling of the pressure tubes and control and protection channels of units 1 to 3. The reactors of units 1 and 2 will then be put into a state of care and maintenance in which they will lie undisturbed, allowing the remaining radioactivity to decay naturally. In the fourth stage, the roofs of the reactor halls of units 1 and 2 will be refurbished while the fuel handling machines of those units will be dismantled. The plant's third unit will then be put into care and maintenance, while in the final stage the unit's reactor hall roof will be refurbished and its fuel handling machinery dismantled.

SSE ChNPP said that the ultimate aim of the project is to bring units 1, 2 and 3 "to a condition that ensures safe, controlled storage of radioactive substances and sources of ionizing radiation within them." It said that the project will cost more than UAH385 million ($43 million).

For the period between 2028 and 2046, the most contaminated equipment will be removed from the units, while the reactors themselves will be dismantled between 2046 and 2064.

The European Bank for Reconstruction and Development said in March that construction of the Chernobyl New Safe Confinement for unit 4 was entering its final stage. The giant structure has been erected over the past four years in a secure area near the damaged reactor in two pieces which are about to be joined together. Meanwhile, a sophisticated ventilation system which will keep the structure corrosion-free during its lifespan is being installed.

The New Safe Confinement will make the old Chernobyl shelter and remnants of the damaged reactor safe and environmentally secure. Completion of the project is scheduled for the end of 2017. The total cost of the Shelter Implementation Plan, of which the New Safe Confinement is the most prominent element, is estimated to be around €2.15 billion ($3.09 billion). The New Safe Confinement alone accounts for €1.5 billion.

For the decommissioning of units 1, 2 and 3, the international community is financing, through the Nuclear Safety Account, the Interim Storage Facility 2 (ISF2) at a cost in excess of €300 million and the Liquid Waste Treatment Facility (LRTP). The ISF2 facility is currently in the final phase of construction and will process, dry and cut more than 20,000 fuel assemblies and place them in metal casks, which will be enclosed in concrete modules on site. The used fuel will then be stored safely and securely for a minimum period of 100 years. The LRTP received an operating licence at the end of 2014.

Researched and written
by World Nuclear News