Within months of the 1986 Chernobyl nuclear disaster, Soviet crews contained the radioactive wreckage inside a temporary shelter, a 21-story-tall “sarcophagus.”
There were many gaps, and most of the sarcophagus wasn’t secured to the underlying structure, leaving the enclosure vulnerable to leaking rainwater, settling, and earthquakes.
In the latter part of the 1990s, the US firm Bechtel which is one of the world’s most respected global engineering, construction, and project management companies designed what is known as the New Safe Confinement (NSC) structure, the heart of a broader, longer-term Shelter Implementation Plan.
The structure will enclose the reactor and associated debris—as well as the sarcophagus surrounding it—providing a confined space within which unstable upper portions of the sarcophagus can be taken apart and the remaining highly radioactive material removed to a long-term storage repository.
The New Safe Confinement (NSC) is the largest moveable land-based structure ever built with a span of 257m, a length of 162m, a height of 108m and a total weight of 36,000 tonnes equipped.
The arches are constructed of tubular steel members and are externally clad with three-layer sandwich panels. These external panels are also used on the end walls of the structure. Internally, polycarbonate panels cover each arch to prevent the accumulation of radioactive particles on the frame members.
Large parts of the arches were shop-fabricated and transported to the assembly site 180 metres west of the remains of reactor 4.
Warm, dry air will be circulated in the gap between inner and outer roof sections to prevent condensation, which will reduce corrosion and prevent water from dripping into the interior.
It will confine the remains of the reactor 4 unit and make the accident site safe. The structure also encloses the sarcophagus or “Shelter object” that was built around the reactor immediately after the disaster.
With a lifetime of 100 years, it will allow for the eventual dismantling of the ageing makeshift shelter from 1986 and the management of the radioactive waste.
The NSC is designed to withstand temperatures ranging from -43°C to +45°C, a class-three tornado, and an earthquake with a magnitude of 6 on the Richter scale.
Because of its vast dimensions, the structure had to be built in two halves which were lifted and successfully joined together in 2015.
The process of sliding the entire arched structure from its assembly point into position over unit 4 was completed on 29 November 2016.
The NSC which is a key part of the Shelter Implementation Plan is being funded by the international community through donations to the European Bank for Reconstruction and Development (EBRD).
It is expected to cost EUR2.1 billion ($2.5 billion) and is funded by contributions, as well as donations from more than 40 countries and organizations.
The EBRD has, to date, provided EUR715 million of its own resources to support Chernobyl projects, including the NSC.
The contract for the design and procurement of this unprecedented construction project was awarded to the Novarka consortium led by the French construction companies BOUYGUES Travaux Publics and VINCI Construction Grands Projets in 2007.
The original EUR432 million contract comprises the design and construction of the NSC and planned to employ 900 people at its peak.
The consortium worked with local sub-contractors and others from across the world.
For instance, the arch was made of structural elements designed and built in Italy. The cranes were manufactured in the US. The arch cladding contractor was from Turkey, and lifting and sliding operations were carried out by a Dutch company.
The construction involves professionals from contracting and sub-contracting organizations from 27 countries.
However, the basic work force is made up of 2,000 Ukrainian workers; more than 1,000 of them are constantly present at the site; 50 people at the site are engaged in radiation protection activities alone.
A Titanic venture
It all started with an incredible amount and scope of preparatory work.
meters of process materials and solid radioactive waste alone were removed from
the future site in order to begin construction work.
When the sarcophagus was erected, large amounts of contaminated materials of all sorts were buried underground on the spot since there was no other place and no especially no time for the evacuation and transportation of those materials.
As a result, the incredible amounts of earth excavated for the preparation of the site were considered not as debris, but as radioactive waste.
A total of 396 steel piles, 376 reinforced concrete piles, and 8,000 tons of reinforced bars were installed.
39 cubic meters of concrete alone was poured in order to prepare the temporary and permanent foundations for the arch.
A unique ventilation system will prevent the steelwork corroding and a specially-designed hermetic membrane will prevent any emission of radioactive dust.
After the NSC is commissioned, the remnants of the destroyed power unit will still present some hazard, despite the new confinement.
The Ukrainian law entitled “On the National Programme of Chernobyl NPP Decommissioning and Shelter Object Transformation into an Environmentally Safe System” provides for the Shelter transformation into an environmentally safe system by implementing a large range of measures.
It is necessary to dismantle unstable Shelter structures, develop Fuel Containing Material (FCM) retrieval process procedures, and remove and dispose of all the raw” materials remaining in the shelter.
However, the work is being carried out under very difficult radiation conditions and the workers can stay in certain areas for no more than 30 minutes per shift.
Dismantling of “unstable” structures is the most burning issue; and this question must be resolved before the end of the established time limit of the shelter’s stability in 2023.
However, these works are beyond the scope of those financed through the Chernobyl Shelter Fund, and the source of their financing has not yet been determined.
The NSC operation costs will become a burden on the state budget of Ukraine, because in the active phase, according to preliminary estimates, they will exceed operating costs of the Shelter object roughly by 5 times and will amount to about $60 million per year.
The project is scheduled for completion on November, 2020.
Decommissioning a nuclear reactor takes a long time, even when the reactor is shut down safely, according to its original life plan.
In 30 or 40 years we might well live in a world where all energy is generated from renewable sources, and where we still have to invest in maintenance for old, partially decommissioned nuclear power plants.
We will one day view these silent, burdensome reactors as our last responsibility in mitigating the damage of nuclear power production — and a reminder that powering the modern world wasn’t always as easy as simply installing panels on our roofs.
NUCLEAR SAFETY ACCOUNT
The Nuclear Safety Account (NSA) financ- es the Interim Storage Facility 2 (ISF-2) and the Liquid Radioactive Waste Treat- ment Plant (LRTP).
The Nuclear Safety Account dates back to 1993 when it was set up at the initiative of the G7 to provide safety assistance to countries operating Soviet-designed nu- clear power plants. In the following years, the EBRD-managed fund successfully completed urgent nuclear safety improve- ments in nuclear power plants in Bulgaria, Lithuania and Russia.
In 1995 the NSA extended its activities to Ukraine. Initially, it funded nuclear safety and security projects at unit 3 of the Cher- nobyl nuclear power plant, the last oper- ating reactor at that time. Since 1998 the fund has been focusing on the construc- tion of two vital infrastructure projects: the Interim Spent Fuel Facility (ISF-2) and the Liquid Radioactive Waste Treatment Plant (LRTP).
The following contributors are members of the NSA: Belgium, Canada, Denmark, European Union, Finland, France, Germa- ny, Italy, Japan, the Netherlands, Norway, Russia, Sweden, Switzerland, the United Kingdom, Ukraine and the United States. Azerbaijan has made a donation.
Overall as of mid-2018 the NSA has re-
ceived some €440 million.
The EBRD provides €235 million of its own resources to support construction of the ISF-2.
One of their biggest projects in Chernobyl is the new Interim Spent Fuel Storage Fa- cility, the largest of its kind in the world. It will process fuel from all Chernobyls re- actors, the last of which was finally closed down in 1999.