New Safe Confinement

The New Safe Confinement (NSC) is an immense steel arch designed to cover the damaged nuclear reactor and prevent further radioactive material leaking into the environment whilst the reactor structure is made safe. It is the worlds largest mobile metal structure.

Objectives of the NSC:
 

• Make the destroyed ChNPP Unit 4 environmentally safe (i.e. contain the radioactive materials at the site to prevent any further risk to the public, site personnel and the environment).

 

• Reduce corrosion and weathering of the existing shelter and the Unit 4 reactor building.

 

• Mitigate the consequences of a potential collapse of either the existing shelter or the Unit 4 reactor building, particularly in terms of containing the radioactive dust that would be produced by such a collapse.

 

• Enable safe deconstruction of unstable structures (such as the roof of the existing shelter) by providing remotely operated equipment for their deconstruction.

The word “confinement” is used rather than “containment” to emphasise the difference between the “containment” of radioactive gases that is the primary purpose of most reactor containment buildings, and the “confinement” of solid radioactive waste that is the primary purpose of the NSC.
 

International competition

In 1992, the Ukraine Government held an international competition for proposals to replace the existing sarcophagus. Of the 394 entries 19 entries were examined in detail, with only the British submission proposing a sliding arch approach. There was no overall winner with the French submission coming 2nd and the UK and German proposals joint 3rd.

Subsequently, a pan-European study (the TACIS programme) re-examined the proposals of the top three finalists and the study selected the sliding arch proposal as the best solution.

The contract for the design and construction project was awarded to the Novarka consortium led by the French construction companies Bouygues and Vinci in 2007.

The consortium worked with both local and international contractors. 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.

Why a sliding arch?

The advantages of a sliding arch include:

1. Off-site construction keeps radiation exposure for construction workers to a minimum.
2. An arch fits snugly over the damaged reactor (minus its chimney).
3. An arch is easier to slide than a square box.

The NSC was constructed 300 metres west of unit four before being slid into place. Weighing more than the Eiffel Tower the arch-shaped steel structure has an internal height of 92.5 metres, enough to house the Statue of Liberty, and an internal span of 245 metres.

The dimensions of the arch were determined by the need to operate equipment inside to decommission the original sarcophagus covering the reactor. The ends of the structure will be sealed by vertical walls assembled around, but not supported by, the existing structures of the reactor building.

Its frame is a huge lattice construction of tubular steel members, supported by two longitudinal concrete beams.

The NSC’s sophisticated ventilation system aims to ensure the longevity of the arch. The air between the inner and outer walls, over 1M.m³, has been dried and subjected to mild pressure to minimise the risk of corrosion.

Its foundations contain over 20,000m3 of concrete, equivalent to over 3200 truck load and the arch is covered in 86,000 m2 of exterior cladding, an area the size of 12 football pitches.

Another impressive feature are the two giant cranes that will be attached to the underside of the shelter roof.

Known as bridge cranes, after the 96m long moving bridges that straddle six parallel tracks mounted to the ceiling, these enormous machines will be remotely operated and capable of lifting 50 tonnes.

The cranes will have three different carriages available to them: a so-called classic carriage which features a hook on a cable that can be raised or lowered by a single drum; a secure carriage, which uses two drums, and will be used to move people around the shelter inside a shielded box; and a custom-made tensile truss system known as the mobile tool platform.

The mobile tool platform will be capable of moving precisely in any direction within the shelter and into areas off-limits to people. It will host a range of robotic devices such as grippers, drills, crushers, and saws.

To date the Chernobyl Shelter Fund, set up in 1997 to assist Ukraine in making the site of the current shelter over Chernobyl’s destroyed reactor 4 stable and environmentally safe, has received more than € 1.5 billion from 45 donors.

 

 

 

 

Site safety

An integrated monitoring system is in place which tracks radiation levels but also seismic activity and the structure of the old shelter.

During peak construction periods over 1,200 workers, of 27 nationalities, were on site. To ensure that workers are safe from excessive exposure to radiation strict dose limits are in operation. Workers carry two dosimeters, one showing real-time exposure and the second recording information for the worker’s dose log.

Dose rates in the main arch construction area are 0.0075 mSv/hr. For comparison an average dental x-ray is 0.014 mSv.

 

Timeline

The NSC was originally intended to be completed in 2005, but the project has experienced several delays. In 2009 progress was made with stabilisation of the existing sarcophagus, which was then considered stable enough for another 15 years. In February 2010 the completion date of the NSC was pushed back to 2013, then subsequently summer 2015. The estimated completion date is now autumn 2017.
 

• 1992 – International competition
  The Ukraine Government holds an international competition for proposals to replace the existing sarcophagus.

 

• 1997 November – Project begins 
  The Chernobyl shelter fund is set up. The financing managed by the European Bank for Reconstruction and Development (EBRD).

 

• 2004 March – Conceptual Design passes expert examination
  The Conceptual Design is discussed at public hearings held in Slavutych, as well as within Ukrainian scientific circles, and it passes a comprehensive state expert examination. Following the results of these discussions the Cabinet of Ministers of Ukraine approve the concept as a basis for further design work by its Order №443-r dated July 5, 2004.

 

• 2007 – Contract for design and construction awarded
  The contract for the design and construction project was awarded to the Novarka consortium led by the French construction companies Bouygues and Vinci.

 

• 2008 to 2011 – Site prepared
  The construction area, situated 300m away to minimise exposure to radiation, is cleaned and cleared. This involves removing soil with significant radioactive contamination. During the first stage, temporary facilities were commissioned: 3 concrete plants, new high-voltage line for concrete plants, construction laboratory, offices, repair shops, warehouses, medical units and canteens were installed.

 

• 2010 April – Construction begins
  Work starts on excavating and laying the concrete beams used to slide the structure into position.

 

• 2012, February 13 – Arch assembly officially begins
  Arch assembly starts when the first batches of basic metal structures are delivered to site.

 

• 2012, November 24 – The first lift of the east side arch is carried out
  The east side Arch, weighing 5,300 tonnes, is successfully jacked up and is now 53 metres tall. A second lift took place on June 13, 2013 with the structure now weighing 9,100 tonnes.

 

• 2013, October 11 – The weight of the arch transferred to its foundations.

 

• 2014, April 26 – The first lift of the west side of the Arch is carried out.

 

• 2015, July 24 – The west and east sides of the Arch are brought together.

 



The western and eastern sections of the arch are joined (Image: ChNPP)

• 2015, October 4 – The east and west sides of the Arch are now joined with all the bolts in place.

 

• 2015, December 7 – The weight of the first crane transferred to the west bridge of the crane beams.

 

• 2015, December – Drone footage of the New Safe Confinement released

 

 

• November 2016 – The New Safe Confinement is moved into place.

The arch was moved 327m using a skidding system consisting of 224 hydraulic jacks that pushed the arch 60cm with each stroke. The operation lasted around 40 hours, spread over a period of five days.

 

 
2017 – Work continues

Work to install air tight seals between the arch and the sarcophagus and test the equipment that will be used for dismantlement will take place in 2017.

Final phase

The final phase of construction of the NSC involves the deconstruction of the unstable structures associated with the original Object Shelter or sarcophagus.

The following sections of the Object Shelter will be removed or made safe:
 

 

• A Live feed from the New Safe Confinement (NSC) construction site is available on the Chernobyl NPP website.