NSC TIMELINE – Concept, Design, Construction and Commissioning of the Chernobyl New Safe Confinement Project in Ukraine.

By Anthony James Addington-Barker – Nuclear Safety Project Specialist – Monitoring Consultant to EBRD and the G7 for the Chernobyl Projects.


The Chernobyl New Safe Confinement (NSC Arch), was a design and build project unprecedented in the history of engineering. Never before had such a huge structure been assembled on such a heavily contaminated site, or indeed moved a distance over land.

Overcoming the risks and difficulties inherent in the project required years of groundwork and preparation, as was laid down in EBRD’s Shelter Implementation Plan (SIP).

The primary purpose of the New Safe Confinement is to contain and prevent any further release of radioactive contaminated material such as activated particulate and protect the Object Shelter (legacy structure) from external impacts such as extreme weather. The secondary purpose, and phase two of the project, is to provide a safe environment to remotely decommission and make safe the Object Shelter containing the destroyed reactor 4 and associated contaminated materials.

Timeline – summary of key events:

1992 – The concept for the Chernobyl New Safe Confinement
September 2007 – Contract signed (Novarka formed)
October 2007 – Design and preparation work commenced 
April 2010 – Work on the assembly area and foundation piling commenced
March 2012 – Assembly of the first frame sections and cladding commenced
November 2016 – NSC Arch structure moved into its final position
July 2019 – NSC Arch Project was completed and handed over to ChNPP


1986 to 1992 

Context – The Chernobyl Disaster

During a safety test at Chernobyl Nuclear Power Plant in Ukraine in the early hours of 26 April 1986, an uncontrolled nuclear chain reaction occurred in the RBMK reactor 4 core, resulting in the vaporisation of super-heated cooling water, releasing a large amount of steam energy.

The resulting explosion, was immediately followed by an open-air reactor core fire, lasting for approximately 9 days, with the event releasing considerable quantities of radioactive contamination into the atmosphere, particularly in Russia and Western Europe.[1]

The Chernobyl Disaster 1986 ChNPP Supplied
Fig. 1. The Chernobyl Disaster 26 April 1986 – Survey photograph taken from Soviet helicopter, morning of 26 April – Photo: ChNPP Supplied.

Soon after the accident, between June and late November 1986, the reactor building was hastily encased by a concrete and steel sarcophagus constructed atop the ruins of the reactor building in a notable feat, that was undertaken under severe radiological conditions.

Object Shelter construction showing Beam B1, Mammoth and Octopus Beams- Chernobyl
Fig. 2. Construction of the Object Shelter showing initial load-bearing supports – No.1. Pipe roof section. No.2. Beam B1. No.3. Mammoth Beam. No.4. Octopus Beam. No.5. Turbine Hall roof – Photo: ChNPP Supplied.

This structure became known as the Object Shelter (OS) and is sometimes referred to as the Sarcophagus or phase 1 legacy structure.

Two years after the Object Shelter was completed, on 22 December 1988, Soviet scientists publicly announced the results of a study estimating the Object Shelter would reach end-of-life following a period of 20 to 30 years. Furthermore, extensive restorative work would be required to structurally enhance the Object Shelter containing the damaged reactor 4, and radioactive materials within.

Completed phase 1 Object Shelter containing the damaged reactor 4 at Chernobyl
Fig. 3. The completed Object Shelter, sometimes referred to as the Sarcophagus or (phase 1) legacy structure containing the damaged reactor 4 at Chernobyl – Photo: ChNPP Supplied.

1992 to 2007

Preparations for the Chernobyl Arch Project & The NSC Arch concept

Less than a year after the fall of the USSR on 26 December 1991 – the newly independent Ukrainian government held a competition for proposals to replace the hastily constructed Object Shelter. However, from total of 394 entries which had been submitted by the end of 1992, no real preferred design option was favoured for first place, although a French submission was voted second, a British and German submission voted joint third.[2]

That said, one of the most intriguing entries was the British submission from a company called Design Group Partnership, in association with the UK Atomic Energy Authority (AEA). This group was the only submission that proposed a sliding approach, building a containment system away from the damaged reactor, resulting in reduced levels of radiation exposure to workers, during the main construction phase.[3]

The Finance

Whilst noting something had to be done to make safe the site at Chernobyl and prevent any further release of radioactivity – in August 1993, the European Commission agreed to finance a study based on the 1992 French, German and British submissions, under its programme of Technical Assistance to the Commonwealth of Independent States, (TACIS).

In March 1995, the results of the first phase of the study which were led by Campenon Bernard (France), and included, AEA Technology (UK), Bouygues (France), SGN (France), Walter Bau (Germany) and Taywood Engineering (UK), were presented to a panel of Ukrainian and International experts in Kyiv.[4]  A project funding mechanism was then established in December 1995, when Ukraine signed a memorandum of understanding with the G8 (later to become G7) and European Commission, inviting the European Bank for Reconstruction and Development (EBRD) to set up a Nuclear Safety Account (NSA). Part of this agreement included shutdown of the remaining reactors – two of which (at the time) were still operating.

The agreement also created the basis for the Chernobyl Shelter Fund (CSF), which was established in 1997, and financed the Shelter Implementation Plan (SIP) through the financial support (at the time), of more than 20 nations.

On 15 December 2000, Unit 3, the last remaining working reactor at Chernobyl was shutdown (Units 1 and 2 had been shutdown in 1996 and 1991 respectively),[5] with the scope of the shelter stabilisation receiving regulatory approval by July 2001, which included the concept stage of the Chernobyl New Safe Confinement (NSC Arch). In February 2003, the IAEA established the Chernobyl Forum, in cooperation with seven other UN organisations as well as the authorities of Belarus, the Russian Federation, and Ukraine.

Site Preparations

As the site infrastructure at Chernobyl was inadequate to meet even the minimum safety standards, an improvement plan was implemented which took until 2004 to complete.

The programme of work included construction of all necessary support facilities, the provision of equipment and the implementation of health, safety, and radiation protection procedures, including a state-of-the-art biomedical protection and screening programme.

Further to this, an offsite training facility was also constructed in the town of Slavutych, including the provision of a number of training programmes for local support staff. This training was essential to create and promote the nuclear safety culture which would be required for major construction activities, with particular emphasis on control procedures and radiological protection methodologies, applied in an area of heavy contamination.

By July 2004, the concept designs for the NSC Arch had received formal approval from the government of Ukraine and an international tender for the design, construction and commissioning was announced.

  • In April 2006, Gorbachev writes that the Chernobyl disaster, “even more than my launch of perestroika, was perhaps the real cause of the collapse of the Soviet Union.”

A further programme of work was undertaken on the Object Shelter (Sarcophagus), with the installation of an additional system called the Designed Stabilisation Steel Structure (DSSS). This was erected close to the old reactor building West wall, in order to transfer part (approximately 50%) of the vertical loading from the “light” roof section over the top of the reactor, away from the old structure, and was completed by December 2006, preparing the way for the next phase of work.

Designed Stabilisation Steel Structure (DSSS) at Chernobyl
Fig. 4. Designed Stabilisation Steel Structure (DSSS) (phase 1) legacy structure at Chernobyl – Photo: ChNPP Supplied.


The Consortium (Novarka)

By August 2007, Vinci Construction Grands Projets and Bouygues Travaux Publics announced that they won the contract to design and build the New Safe Confinement, (sliding Arch design), as 50/50[6] partnership of the French consortium Novarka.

Chernobyl New Safe Confinement contract signature and official start of the NSC Arch project – Monday 17 September 2007.

On 17 September 2007, the contract was finally signed in Kyiv with Chernobyl Nuclear Power Plant (ChNPP) – almost ten years after the agreement on SIP, between the G8, EC and Ukraine was originally signed.

With the signing of the contract, and with all available information at the time, the initial project schedule of work (herein referred to as the Programme), had a completion date of 30 March 2012.

Following the signing of the contract in September 2007, the first planning and design teams for the Chernobyl New Safe Confinement (NSC Arch) were formed, mobilised and commenced work on Monday 29 October 2007.[7]

The first task undertaken was to commence a complex procurement procedure, which included independent technical and legal assessments and a thorough analysis against the design basis for the concept.

The primary requirement for the New Safe Confinement as set, was to confine the Object Shelter containing all radioactive materials and structure within, preventing further environmental contamination and ultimately, in the phase 2 work, enable safe stabilisation and decommissioning of the Object Shelter structure and materials within. Furthermore, it also had to meet a set of demanding Design Basis (DB) safety criteria.

November 2007 saw the first Chernobyl Technical Working Groups (ChTWG) convene and the commencement of a series of in-depth Design Basis and Beyond Design Basis (BDB) limits and conditions (cut-off analysis), to establish the safety criteria for the proposed New Safe Confinement.


By Summer 2008, the main elements for the Design Basis safety criteria for the New Safe Confinement had been agreed. Whilst final elements of the design basis were still being established, there was enough information to facilitate the design for the main NSC Arch structure.

Preliminary information for the design included the NSC Arch structure’s ability to withstand seismic events up to a magnitude 6 earthquake, with a Peak (horizontal) Ground Acceleration (PGA) of 0.18g, and vertical Acceleration of 0.15g. Furthermore, the NSC Arch structure had to withstand a class 3 tornado and a 1 in a 1000-year snow and ice loading event, while containing the environment within at a constant negative pressure through specially designed filter systems.

All this represented a considerable design challenge, not only for the main NSC Arch structure and cladding, but also for the whole New Safe Confinement facility, its structural interfaces and all engineering systems and supporting services.


New Safe Confinement (NSC Arch), design and initial project challenges

By July 2009, the Design Basis safety criteria, functional specification, and the contractor’s proposed concept design were issued. This allowed for commencement of the second phase of the planning and design work which included a more detailed planning and design study of internal and support systems, and investigation of potential suppliers and subcontractors.

The Arch shaped structure that was agreed upon, was to have a span of 257 metres, a length of 162 metres, and a height of 108 metres. The cladding was to be double thickness with an Annular space in between of 10 meters. The total weight of the NSC Arch would be in the region of 36,000 tonnes.

In order to limit radiation exposure to workers during construction, the concept was to assemble the NSC Arch approximately 300 (actual moved distance 327) meters away, to the West of the Object Shelter. The NSC Arch would be assembled in two sections (East and West), would be joined together, the Main Crane System would be installed within the canopy section of the Arch, and then the assembled structure slid over the Object Shelter and reactor 4 building.

Whilst adopting this methodology, there would still be a number of significant one-of-a-kind technical challenges to overcome, particularly in interfacing the NSC Arch and existing structure together in a demanding and hazardous radiological environment.

Initial challenges identified with the design methodology included:

  • Moving the 36,000-tonne structure without deformation of the NSC Arch structure or subsidence of the ground, and/or any deformation/collapse of the Object Shelter
  • Removal of the old vent stack on Block-V (Deaerator stack structure) between Units 3 and 4 which was in the way of the NSC Arch sliding, and installation of a new vent stack on the same roof, a few meters further to the East
  • Overcoming obstructions that couldn’t be moved on the Object Shelter whilst sliding, and
  • Sealing the old structure with two End Walls (East and West) within the existing building to form containment walls under the NSC Arch End Walls. This work would prove particularly challenging, not only for the high levels of radiation, but also because a considerable amount of this work would be undertaken in confined spaces with possible risk of collapse of the old structures – damaged in the initial explosion in April 1986.

New Safe Confinement (NSC Arch), assembly area ground works

Fig. 5. Ground works in the future Arch assembly area. Monitoring and areas of high radiation being marked ready for special excavation – Photo: EBRD/Novarka.

Preparation work for the assembly area. to the west of the reactor 4 building, commenced early in 2009, with geotechnical investigations and mapping of radioactive debris which continued throughout the year.

In addition, 55,000m3 of soil containing medium and high-level radioactive waste was removed from the construction area, including some items used during the 1986 cleanup operation and assembly of the Object Shelter, such as, two mobile cranes, one tractor and one excavator.


By April 2010, earthworks for the assembly area base and concrete beams on which the arch would be assembled and slid had commenced, this also included some temporary laydown areas. Further milestones achieved in May 2010, included contract awards for the manufacture of the NSC Arch elements to Cimolai in Italy, and Main Crane System (MCS) to PaR Systems in the USA, which when assembled would be the world’s largest remotely operated robotic crane.

By August 2010, work on the foundations for the lifting towers and piles for the longitudinal beams in the assembly area had commenced. Concrete pouring in the assembly area (erection zone) was also underway, this also provided a barrier for the workers against any surface contamination.

Following some further adjustments to the Programme of work at the end of 2010, the estimated project completion date moved from 30 March 2012 to 2 October 2015.

Fig. 6. Ground works being undertaken in the Arch assembly area and sliding foundations. DSSS / Object Shelter background centre, Turbine Hall background right – 18 November 2010 – Photo: EBRD/Novarka.


By October 2011, work on the assembly area (erection zone), including foundations for the lifting towers and piles had been completed. On 29 November 2011, the new Ventilation (Vent) Stack, measuring 50 meters in height and 6 meters in diameter had been installed a few meters to the East of the old unit, atop of the Block V Building.

To note: In RBMK power plants, the Ventilation Stack is used for discharge and dilution of gaseous radioactive wastes. These include dilute sources (such as activation products and small amounts of volatile fission products in occupied spaces like the central hall) and more concentrated sources, such as exhaust from the condensers and deaerators, waste from the reactor graphite cover gas, and waste from the control rod cooling system.

At Chernobyl, the main Vent Stack emission during the plant’s operating history was Argon (Ar-41). Most of this came from neutron activation of natural argon (Ar-40) dissolved in the water of the control rod cooling circuit. At the Chernobyl plant, in common with some (but not all other) RBMKs, atmospheric air was sparged (gas flushing) through the control rod cooling water to drive out corrosive and combustible radiolytic gases. This air contact was responsible for large amounts of dissolved Argon in the water and for introduction of Ar-41 into the ventilation system.


Assembly of the New Safe Confinement, NSC Arch frame and cladding

During the months of February and March 2012, the first shipments of the NSC Arch frame elements arrived by train from the port in Odessa, having been shipped from Cimolai in Italy – work on the Arch frame assembly, commenced late April 2012.

Fig. 7. NSC Arch – Early stages of the assembly process, 7 May 2012 – Photo: Don Kelly.

However, due to complications with contract negotiations in the early stages of the assembly process, installation of the NSC Arch cladding panels did not commence until 2 October 2012. The result of which, impacted the Programme critical path on all related interdependent structural activities for cladding installation – reflecting the first major delay to the project.

Fig. 8. Arch frame waiting for arrival of Cladding, 1 September 2012 – Photo: Viktor Andreev.


Fig. 9. Arch Cladding installation progress, 31 October 2012 – Photo: Viktor Andreev.

On 27 November 2012, a major construction milestone was achieved, in the first of three lifting (jacking) operations for the East Arch section – the lift also allowed the assembly teams to commence internal cladding installations, as the underside of the structure now became accessible.

Fig. 10. Completion of the first of three lifting (jacking) operations for the East Arch section, 28 November 2012 – Photo: Viktor Andreev.

In December 2012, an updated Programme was issued realigning the project completion date from 2 October 2015 to 30 September 2016.


As the project continued into January and February 2013, a number of developing challenges had been identified that had the possibility of impacting the project completion date, these included:

  • Achieving final, detailed design of the main NSC Arch structure and interfacing, this also had implications for licencing and the Safety Analysis Report (SAR)
  • Challenges in early procurement of some packages, such as Lightning Protection Ducting, and Ventilation
  • Backfitting ice and snow loading calculations within the design for the cladding
  • Challenges defining the foundation design the south trench and service zone, including higher levels of radiation than anticipated during excavation, of between 150 µSv/h; and 220 µSv/h
  • Changes in the Ukrainian norms and standards following the acceptance of the Concept Design Safety Document (CDSD)

Furthermore, another challenge was to define and finalise overlapping, underlapping and interfacing issues with all stakeholders, which at the time were yet to be fully defined – generally relating to assumptions and qualifications. As a result, the contractor undertook an option study (herein called the Action Plan) to determine a suitable way forward.

While the Object Shelter, associated structures and its many connections remained unprotected from the elements – as time progressed, the probability that sections of the old structure would become unstable and collapse increased. The extreme weather-cycling in Ukraine, and excessive unchecked corrosion of the old structure increased concerns that a collapse may have the potential of releasing activated dust particles into the atmosphere.

At 02:03 on the morning of 12 February 2013 – following a medium to heavy snow fall, accelerometers (sensors) that had been installed in and around the Object Shelter at Chernobyl recorded an event. It was discovered, following an early morning inspection, that a part of the Unit 4 Turbine Hall (TH) roof had collapsed between axes 50 and 52, close to the Object Shelter.

The event occurred when weakened connections of one of the transverse roof trusses failed, probably a result of the small additional loading. This intern initiated a collapse from the side elevation of the Turbine Hall towards the concrete Deaerator Stack Building between Units 3 and 4. Although the automated radiation monitoring system recorded no increase or exceedance of reference levels, a detailed radiation survey was undertaken at first light which confirmed that alpha and beta contaminants remained below reference levels.

Following collapse of the roof, a comprehensive radiation monitoring programme was initiated and performed in the Turbine Hall and localised area on a regular basis, to complement the continual radiation monitoring with the installed automated system. IAEA also undertook a survey, and issued a report to log the event – In general, this incident was a reminder of the urgency and understanding of the need for the NSC Arch at Chernobyl, and indicated the urgency of finishing the project as soon as physically possible.

Work continued well into 2013, April saw the approval of systems design for ventilation, auxiliary building, high voltage power supplies, and radiation monitoring & control systems for the Arch, including associated procurement.

April 2013 saw an update to the Programme, adjusting the project completion date from 30 September to 24 October 2016.

However, although the Programme completion date further increased, there remained a large number of uncertainties within the scope of work which required further detailed analysis and implementation. It was also understood that some important elements within the work streams remained underdeveloped. Document control activities for licencing required further defining, pre-commissioning and commissioning activities were largely absent and some activities were difficult to determine due to level of potential difficulty, such as working environment, and unknown work packages which could require additional resources, over and above those already accounted for within Programme float.

The Action Plan remained in progress, and by this time involved all stakeholders and included the introduction of a number of new team members within project controls for the Project Management Unit, (PMU).

14 June 2013 saw completion of the second lifting (jacking) operation for the East Arch section
Fig. 11. Second lifting (jacking) operation for the East Arch section underway, 14 June 2013 – Photo: Don Kelly.

The 14 June 2013 saw completion of the second lifting (jacking) operation for the East Arch section. In August 2013, prior to the commencement of the foundations of the Technological Building (TEC Building), a temporary biological shield was erected between the Object Shelter and construction zone to protect workers from the high levels of gamma radiation, known as gamma shine, coming from the Object Shelter and destroyed reactor 4. Levels directly behind the shielding wall were in the region of 200µSv/h, and in front reduced to around 20µSv/h.

The 16 September 2013 saw the third and final lifting operation for the East Arch section. This was then transferred to the skidding system by 11 October 2013, with the foundations taking the weight of the Arch for the first time. This activity was closely followed by erection of scaffolding to install brackets for the stainless-steel ventilation ducting, although delivery of ducting had by this time also slipped into delay.

With the first, East Arch section now at full height, the second West Arch section could begin to be assembled underneath the first Arch section. Work commenced on the West Arch, weekend of 20 October 2013. Two days later on 22 October 2013, the new vent stack which was installed on the roof of the Deaerator Building in November 2011 was finally commissioned in put into operation. This work was required to be completed before removal of the old vent stack between units 3 and 4, in order to make way for the NSC Arch structure during the sliding process.

Fig. 12. Removal of the old 75.5-meter-tall Vent Stack, 1 November 2013 – Photo: ChNPP.

On 31 October 2013, work commenced on the removal of the old 75.5-meter-tall Vent Stack. Totalling 330,000 kg (330 tonnes), it comprised of seven sections, each weighing between 25 and 60 tonnes. Removal work was undertaken by subcontractor (Ukrtransbud of Ukraine). Work dismantling the old ventilation stack was completed by 25 November 2013, with each of the sections placed in a specially prepared area to the North of the turbine hall for temporary storage before decommissioning to a prepared area on site.

Although the physical work removing the Vent Stack was generally undertaken well, a number of procedural issues were noted resulting a safety evaluation assessment of the work undertaken – radiation levels on the Block V roof removing the Vent Stack varied between 150 to 260 µSv/h.

Then, on 21 November 2013, a major project risk began to develop as result of the Euromaidan crisis within Ukraine. Following the Maidan protests in Kyiv, political destabilisation in the country followed and subsequently the invasion and annexation of parts of Ukraine by Russia followed.

Fig. 13. NSC East Arch section with jacking towers partly removed, 21 November 2013 –  Photo: Anthony James Addington-Barker.


As a direct result of the unfolding crisis in Ukraine, all work on Chernobyl site projects began to slow through January 2014, with some projects beginning closing down by early February due to the worsening situation. Some staff were evacuated home by their respective companies, and those remaining had evacuation and escape plans in place should the situation further worsen.

By the second week in February 2014, shootings and conflict continued to escalate in Kyiv and around the country, with curfews being implemented in most Ukrainian cities. Although most of the staff on the NSC Arch project remained on and around site, they began to take steps to minimize any possible impact. Areas were made safe and secured in the event of a total site evacuation, and remaining teams were placed on standby.

The situation further escalated by 20 February 2014, mass shootings took place in Kyiv, and President Viktor Yanukovych, escaped by Helicopter to Russia in the early hours of the morning, just as Russia began to invade parts of Eastern Ukraine and the Crimean Peninsula where the Russian Black Sea Fleet were stationed.

Almost all site work stopped the afternoon of the 20, and all day on 21 of February 2014, whilst the situation was being evaluated on a minute-by-minute basis.

However, although the crisis in Ukraine remained critical, by Monday 22 February 2014, a decision was made to remain on site and continue working on the New Safe Confinement project, although other major Chernobyl projects such as construction of the Interim (Spent Nuclear Fuel) Storage Facility 2 (ISF2), remained closed with staff repatriated into March and April 2014.

Fig. 14. NSC East Arch section sliding, 1 April 2014 – Photo: EBRD/Novarka.

Following the first stage of the Action Plan review, March 2014 saw an updated Programme of work, moving the project completion date from 24 October 2016 to a new completion date of 22 November 2017.

Discussions on the Action Plan remained ongoing between stakeholders, in addition, the early involvement of a commissioning control manager was identified to better control the teams for systems integration and specifically, to assist in the development of the pre-commissioning and commissioning (the back-end) elements of work.

The 1 – 3 April 2014, saw another major milestone event in the sliding of the East (first) half of the Arch (96 meters) towards the holding area, and 26 April8 the first lifting operation for West (second) half of the Arch. April also saw commencement of work on the foundations for the Technological and Auxiliary Buildings, and by the end of April 2014, the Contractor had achieved 2,000,000 Man Hours without a Lost Time Incident (LTI) for Total Project activities, and 194 days on site without a Lost Time Incident.

As piling work on the permanent arch foundations (to the South of reactor 4 building) continued into 2014, it was found they required considerable redesign due to unforeseen ground conditions. In addition, further discoveries of high-level waste, were made, including a wide array of contaminated objects which had been buried in the excavation area. This along with difficult conditions, as result to the proximity to the damaged reactor 4 and related gamma shine, required both additional mobile and fixed shielding to be erected, and further extended unplanned work durations.

Fig. 15. Preparation for final Arch jacking, 13 October 2014 – Photo: EBRD/Novarka.

The 4 August and 24 October of 20149 respectively, saw the second and third (final) lifting operation undertaken for the West (second) half of the NSC Arch. This was then lowered onto support points connected to the Mammoet tractor units which would later move the Arch into position over the Object Shelter.

Fig. 16. View looking through East and West Arch, 30 October 2014 – Photo: EBRD/Novarka.

In October 2014, teams were mobilised to perform the first phase of one of the most physically challenging aspects of the Project – the End Walls.

Fig. 17. Workers clearing debris within the legacy structures at Chernobyl as part of the End Wall Project – Photo: ChNPP.

In order to fully seal in the Object Shelter structure to the NSC Arch structure, two partition walls would need to be constructed within the existing buildings underneath the final resting positions of the East and West end panels of the NSC Arch. This scope of work included the reinforcement and sealing between units 3 and 4, forming new dividing walls within the Turbine Hall, Deaerator Stack Building, Block V and Auxiliary Reactor Systems Void. This would then form an interface for the installation and attachment of a series of anchor points around the building to enable installation of a double-walled flexible sealing membrane between the original historical structures and the Arch structure.

On the 26 November 2014, the West and East Arch section were finally brought together so they could be joined, in doing so, forming the full main structure of the New Safe Confinement for the first time.

In order to clear obstructions on existing structures such as the Object Shelter, Turbine Hall and Deaerator building when the Arch was slid over the Object Shelter, immense hinging doors were to be fitted to the East Arch section. In December 2014, the first of these doors, (tilting panel number 1), was hoisted into position and successfully connected to the East Arch section.

Fig. 18. NSC Arch East End wall showing installation of four (4) Tilting Panels – Photo: EBRD/Novarka.

Following mobilisation for the End Walls project, work commenced late December 2014. This work was undertaken by a small number of Ukrainian subcontractors (UkrEnergoMontazh, JSC Kievmetrostroy, Ukrainian State Building Corporation “Ukrbud” and OOO SK Ukrstroymontazh).

However, before work could commence on strengthening and erecting new dividing walls, all legacy equipment and metal structures in the vicinity of the working areas had to be dismantled and stripped-out, as well as removal of hundreds of cubic meters of reinforced concrete. All this material had then to be carefully transported out of the immediate area to a temporary medium/high level waste storage area within the basement of the original structure, often working in severely confined spaces with some areas having dose rates as high as 350 to 400 µSv/h and above.


Installation of the cladding and specialist ventilation system ducting continued into the spring of 2015. In May 2015, one of the main pieces of equipment, the Main Crane System (MCS) was shipped from PaR Systems, Shoreview, Minnesota in the US, arriving in the port of Odessa, Ukraine on 14 June 2015.

The Main Crane System would the largest (remotely operated) robotic nuclear crane in the world. Comprising of five major components – two 96 meter (East & West) bridge sections weighting 800.000kg (800 tonnes) each, one classic carriage hoist, one secure carriage hoist, and one Mobile Tool Platform (MTP) utilising a special Tensile Truss® technology.

In addition, all Main Crane System major electrical components required extensive engineering and reliability analysis to ensure the crane could operate in the radioactive environment whilst dismantling the structures around the destroyed reactor 4 at Chernobyl.

The Main Crane System would be suspended from the inner ceiling section of the NSC Arch, on tracks running the full length of the facility. A special maintenance garage would also be constructed at the far West end of the facility within the ceiling section of the Arch, to provide a shielded maintenance area. The crane when completed would be controlled from a remote location (control room) within the TEC Building – which at this time, remained under construction.

By June 2015, there was enough of the NSC Arch system installed to commence with some of the electrical system installations such as High Voltage (HV) caballing, and some of the ventilation power systems.

Fig. 19. Main Crane System (MCS) west bridge inspection, NSC Arch, Chernobyl, 26 & 27 August 2015 – Photo: Anthony James Addington-Barker.

The 28 July 2015 saw the last of the external cladding being installed on the NSC Arch, and October 2015 saw the start of training for operating personnel, which was integrated into the installation and contractor testing.

Installation of the tilting panel jacks commenced in November 2015, and 27 to 28 November, the first of the two overhead Main Crane System (West) bridge section was lifted into position to a height of 82 meters inside the NSC Arch.

Fig. 20. The first of the two overhead Main Crane System (West) bridge section was lifted into position to a height of 82 meters inside the NSC Arch, 27 November 2015 – photo: ChNPP.

By the end of year in December 2015, work had commenced on installation of the special doors around the facility. These doors afforded protection to major hazards such as fire, and included installation of special armoured, anti-tornado doors which were fitted with airtight seals and had seismic withstand to the established safety criteria of 0.18g.


In the first quarter of 2016, a significant change in project strategy and logic was adopted, bringing the sliding date of the Chernobyl NSC Arch forward and moving large elements of work from the pre-sliding phase to the post-sliding phase.

Fig. 21. Part of the Main Crane System (MCS), East Bridge during assembly. View looking down from the Annular Space, Arch roof, 2 February 2016 – Photo: Anthony James Addington-Barker.

This early sliding strategy resulted in a number of new challenges due to a change in the working environment, which would be closer to the damaged reactor 4, and required, in many cases, the installation of additional mobile and fixed shielding. Furthermore, as a consequence of early sliding, the End Walls project (works) which were being undertaken within the legacy structures, were required to be accelerated to complete before November 2016.

By 18 February 2016, the Mobile Tool Platform had been attached to the Main Crane System (East) Bridge, and on 31 March 2016 they were lifted the 83 meters into position and attached rest of the system.

Fig. 22. Mobile Tool Platform attached to the Main Crane System (East) Bridge being listed into position, 31 March 2016 – Photo: EBRD.

March 2016 also saw installation of the last major cladding panel to the West elevation although a small number of panels were not installed until after sliding for the purpose of access and egress to the Annular Space (AS).

June 2016, saw completion of civil engineering works on the TEC building containing the control room for the MCS, and by 14 July 2016, all tilting panel jacks had been installed, tested and the tilting panels parked in the open position ready for sliding.

Installation of the external Vent Stack designed specifically for the NSC Arch ventilation system was installed on 3 September 2016. The Vent Stack was lifted in one section to the West wall of the NSC Arch – the unit itself measuring 80 metres in length, 3.5 metres in diameter, and a total weight of 80,000kg (80t).

Fig. 23. New Safe Confinement (NSC), New Vent Stack, Chernobyl, 10 March 2017 – Photo: Anthony James Addington-Barker.

September 2016 also saw the start of the anchor installation, connections on the Arch and along the End Wall structures to attach a double wall flexible membrane that would seal the NSC Arch to the Object Shelter and legacy structure. This system had to be designed in such a way as to allow the connections between the structures to move in the event of a seismic event, plus, minus half a meter, (+/- 0.5m).

By October 2016, main construction works on the phase 1, End Wall project had been completed in accordance to the accelerated sliding schedule. This also allowed for early dismantling of crane runways for the heavy lift crane[10], which was used during construction of the End Walls project and had to be removed prior to sliding – this work was achieved by 28 October 2016.

Arch Sliding

By the beginning of November 2016, the NSC Arch remained standing in the assembly area waiting to be slid over the Object Shelter. This task had to be successfully achieved by the 29 November 2016 for the sliding ceremony to take place, involving presidents, dignitaries and distinguished guests from many organisations and government bodies from around the world, including the world’s press.

The total Arch structure, now weighing over 36,000 tonnes, would have to be moved over 300 meters on its ceramic sliding plates – this would render the NSC Arch, the heaviest land-based structure ever moved. 

It was estimated the sliding of the NSC Arch would take approximately four days in total, and although the process was known, having been tested, at least in part, nothing like this had ever been attempted before.

Due to a number of technical issues relating to synchronisation of the Mammoet tractor units, the first movements of the Arch did not commence until Monday 14 November 2016, just fifteen days before the Arch ceremony.

The operation commenced in the early hours of day one, however, after just four meters, the system tripped due to variations in the ram pressure. On the second and third day, engineers reset the system, and on the fourth day the Arch moved forward another eight meters before the system again tripped.

Fig. 24. Transfer system, during the sliding process, 17 November 2016 – Photo: Anthony James Addington-Barker.

Another four days passed while all the systems were recalibrated, then on the 21 November 2016, eight days before the ceremony, the Arch moved over 80 meters. The NSC Arch then continued to move varying amounts each day, until on the 27 November 2016, two days before the sliding ceremony, the NSC Arch reached its final position, travelling 327 meters from its assembly point to its final resting place over the Object Shelter and the reactor 4 building.

Even though foundations had been piled in both the Arch assembly area and final resting place over the Object Shelter and reactor 4, between these two points, a distance of over 100 meters was a raft foundation system. As the NSC Arch was of considerable mass, and being moved over land on soft ground mainly comprised of sand with a high water-table, there was concern of the possibility of ground displacement caused by the mass movement of the Arch. Notwithstanding the calculations that had been undertaken, there was real concern of the possibly of a collapse of the some part of the old legacy structure, due to possible excessive displacements caused by variations of the mass of the Arch during transfer. Therefore, as part of the mitigation for this issue, a number of additional accelerometers were placed in and around the Object Shelter and included a number of laser alignment monitors placed on the ground and legacy structures.

Although this particular concern was unfounded, as following the sliding of the Arch, a maximum of 1.6mm of displacement was recorded following settlement.

On 29 November 2016, the NSC Arch sliding ceremony took place at the Chernobyl Nuclear Power Plant outside the New Safe Confinement to mark the successful completion of the sliding operation. This was a key milestone before the finalisation of the international programme to transform Chernobyl into an environmentally safe and secure state. The ceremony was attended by the then President of Ukraine, Petro Poroshenko, President of EBRD, Sir Suma Chakrabarti, , Director General ChNPP, Igor Gramotkin, Hans Blix, and many other distinguished guests and donors from around the world.

Fig. 25. The ceremony in Chernobyl on 29th November 2016 marked the successful conclusion of the sliding operation -Photo EBRD/Novarka.


By January 2017, following the successfully sliding and installation of the NSC Arch over the Object Shelter at Chernobyl – sealing the NSC Arch to the legacy structure commenced.

Development of the main working document (Final) Safety Analysis Report, FSAR, was progressing, which was reconfigured to adopt a stage-by-stage approach based on the integration of the Object Shelter and NSC Arch safety analyses. The document for the New Safe Confinement was split into two packages; those being the Arch structure including Main Crane System (Part 1), and Buildings and their respective systems and interfaces (Part 2).

In February 2017, following further testing of the Main Crane System, it became apparent that at some point during the sliding and transfer of the NSC Arch over the Object Shelter, some slight movement of the upper Arch structure had occurred. This resulted in a fractional misalignment of the crane rails in the longitudinal direction. However, although the crane rails were realigned, two new issues were observed in the form of contact of the underside of the rails by the seismic restraints whilst traversing, and a none-uniform torque from the drive motors causing the crane main beam to skew when in motion.

Whilst commissioning work on the Main Crane System continued throughout 2017, an effort to resolve and close out the newly developed issues continued – new shims were installed on the seismic restraints to the required clearance and all drive motors were configured with new control algorithms which compensated for the none-uniform torque.

Fig. 26. Under the NSC Arch, looking toward the Object Shelter with the yellow supports of the DSSS, showing two concrete personnel radiation shielding boxes, foreground, Chernobyl, 10 March 2017 – Photo Anthony James Addington-Barker.

The 30 June 2017 saw the issue of a new Programme of work, adjusting the project completion date to 14 December 2017, although the new date also remained challenging due to the pre-commissioning work load and the number of unforeseen technical issues that had to be resolved to meet the New Safe Confinement design criteria.

The final phase 1 End Wall roof works were completed by July 2017, although the End Wall contractor remained on site until 25 October 2017 to complete remaining phase 2 work and support the final air pressurisation (air leak tightness) tests.

However, work on the NSC Arch during summer 2017 saw a number of new issues. In July 2017, it was discovered the Type 1 anchors for attaching the Arch Sealing Membrane would require redesigning and additional rework on already completed works would also need to be undertaken due to enhancements in safety criteria. High levels of radiation were also discovered in certain areas during coring works to install beams and membrane flashing anchors on Block V roof. Workers using mobile shielding were recording readings of 325 µSv/h and above, resulting in difficult working conditions (each worker limited to under 5 minutes exposure each per day). Furthermore, following removal of sections of the lightweight, roof several structural issues were uncovered, including some issues with the ‘octopus beam’ on the legacy structure.

16 August 2017 saw commencement of the phase 2 End Walls, which included installation of internal dividing walls between Block V and the Deaerator Stack, placement of remaining concrete walls (approximately 1,500 m3), installation of new and relocation of existing technological and electrical networks, and construction of a new roof section for the Turbine Hall at the interface with the NSC Arch (East and West end of the Turbine Hall).

On 31 August 2017, a new Programme of work was issued, adjusting the project completion date, from 14 December 2017 to 26 May 2018. However, a significant amount of work still had to be completed, particularly in final installation, testing and commissioning, compounded by design issues and difficulties in the working environment, relating to high radiological conditions.


By the beginning of 2018, pre-commissioning was progressing on all major systems, although there were complications as some systems and interfaces remained incomplete. In March, it was becoming apparent that the pressure differential of some 20 Pascals between the Annular Space (AS) and Main Volume (MV), as had been stated in the original safety criteria may be a challenge to achieve in certain emergency modes.

By July of 2018, three out of six stages of the Main Volume and Annular Space ventilation test had been performed, although at the time, no formal results were issued by the Contractor and the full scope of the MV and AS test was postponed to the middle of November 2018 while further modifications and adjustments were made.

Throughout August and September of 2018, high radiation levels continued impacting works on Block V roof, further modifications to the HVAC design within the TEC Building were required, some services required design changes and general issues associated with pre-commissioning and staged handover strategy continued to challenge the project.

Fig. 27. Inside the roof section, NSC Arch. MCS top right, and OS bottom left. Chernobyl Ukraine, 14 December 2018 – Photo: Anthony James Addington-Barker.

With these additional challenges, 31 December 2018 saw the issue of a new updated Programme of work, realigning the project completion date to 31 July 2019.

Although the new completion date was now considered achievable by all stakeholders, a number of challenges still remained, including some licencing elements such as the Main Crane System technical specification, some delays in software programming, electrical design finalisation for systems interfacing, and issues with the Foam Fire Fighting System (FFFS) foam guns, both in seismic qualification and the delivery of foam pressure at roof level.

During the pre-commissioning phase, testing of abnormal operations such as accident and recovery modes were undertaken on an individual systems basis. However, in order to prove and qualify the New Safe Confinement before handover to Chernobyl Nuclear Power Plant (ChNPP), It was agreed the facility would undergo a 72-hour Trial Operation (Cold Test) in normal operational mode. Although it was also agreed that other elements of safety critical work would be deferred until after the 72-hour Trial Operation but completed and signed-off before handover – an example of such was the Foam Fire Fighting System.

One late identification to work, was the design of and construction of access ways for general maintenance and sealing membrane inspection. However, although this work extended past the possible handover date, an agreement was reached to install temporary scaffolding systems until the work would be completed at a later date.


By January 2019, pre-commissioning was progressing into the final stages, the Main Volume and Annular Space ventilation test had been successfully achieved, through mechanical upgrade and procedural change, although a number of clarifications and modifications on punch-list items still required addressing and closing out.

Fig. 28. New Safe Confinement approaching completion 2019 – Photo: ChNPP.

The Instrument and Control System (ICS), Radiation Monitoring Systems (RMS), Integrated Shelter Data Base (ISDB) and Integrated Automated Monitoring System (IAMS) were all in the final stages of testing but required a number of safety category items to be finalised. The technical specification for the Main Crane System which was required for completion of the (Final) Safety Analysis Report, remained outstanding but was also in the final stages of being concluded, and some modification on the electrical and connection interfaces required completing and signing off.

On the 26 April 2019, exactly 33 years to the day of the Chernobyl accident, the successful completion of the 72-hour Trial Operation Test was achieved.

22 April 2019 – Transfer New Safe Confinement to Trial Operation Mode
23 April 2019 – NSC Trial Operation Test 30% complete
24 April 2019 – NSC Trial Operation Test 63% complete
25 April 2019 – NSC Trial Operation Test 96% complete
26 April 2019 – NSC Trial Operation Test 100% complete

Following the successful Trial Operation Test – work on site continued well in order to close out remaining safety critical elements and conclude work that was considered non-essential to completing the 72-hour Trial Operation. 

One outstanding safety critical element at this time was the Foam Fire Fighting System (FFFS), and although the Foam Fire Fighting Guns which formed part of the system now met the required seismic criteria, the foam pressure delivery remained problematic.

On the 19 May 2019 the Foam Fire Fighting System (FFFS) was tested in the presence of the Fire Regulator. However, the system again failed to meet the required criteria for pressure, and distance of the fire suppression foam material. However, after further modifications, one of the last systems was successfully commissioned on 14 June 2019.

Work continued through June 2019 completing remaining pre-commissioning elements, energisation and testing, consecutively demobilising some none essential teams and clearing work areas. Some minor works relating to installation of the various roofs of the Object Shelter remained when the End Walls contractor demobilised, and could only be completed once the scaffolds were removed.

Fig. 29. New Safe Confinement (NSC Arch) and Chernobyl Nuclear Power Plant , August 2019 – Photo: Arkadiusz Podniesinski.
On the 30 June 2019, The Final Safety Analysis Report (FSAR rev.01) was issued, although a number of minor licensing documents remained outstanding and were delivered at various intervals throughout 2019.
By the first week in July 2019, all remaining works had been completed, construction, support equipment and scaffolding removed and final systems handover was underway. However, although over ninety percent of the workforce had by this time been demobilised, a small number remained on site to continue snagging and close-out of the remainder of none safety critical equipment.    

On 10 July 2019 – VINCI Construction Grands Projets and Bouygues Travaux Publics, partners in the NOVARKA consortium, symbolically handed over the key to the Chernobyl New Safe Confinement to the Ukrainian authorities at a ceremony that was held on site on Wednesday 10 July 2019, in the presence of the Ukrainian President, Volodymyr Zelensky.

The Chernobyl New Safe Confinement (NSC Arch) project was completed, and keys for the facility handed over to the Ukrainian authorities on Wednesday 10 July 2019. The total project duration from contract signature on Monday 17 September 2007, was 11 years, 9 months, 3 weeks, 4 days, or 4,314 days.

“Chernobyl New Safe Confinement (NSC Arch) project, was an unprecedented, one-of-a-kind, extraordinary endeavour, without equal anywhere in the world. Managed by EBRD and funded by more than forty countries, the project was undertaken in one of the most challenging radiological environments ever attempted for such a project. But to say this was just a project is an understatement – this was nothing more that an adventure into the unknown.”

Anthony James Addington-Barker.

Chernobyl fund was managed by EBRD and received close to $2.1 billion from more than 40 countries, including members of the fund

Austria, Belgium, Canada, China, the Czech Republic, Denmark, the European Community, Finland, France, Germany, Greece, Ireland, Italy, Japan, Kazakhstan, Kuwait, Luxembourg, the Netherlands, Norway, Poland, Russia, Spain, Saudi Arabia, Sweden, Switzerland, Ukraine, the United Kingdom, and the United States.

New Safe Confinement – NSC Arch related work programmes

NSC Arch frame and cladding – Main Arch Structure
TEC & EEB Buildings
MCS Main Crane System
ICS Instrument & Control Systems including Radiation Monitoring
Ventilation System
End Wall Project, Sealing the old and new structures together

Chernobyl New Safe Confinement (NSC Arch) – Managements Teams

EBRD (The Bank)
Balthasar Lindauer – EBRD Director Nuclear Safety (Previously Vince Novak)
Simon Evans – Associate Director and Head of Chernobyl Shelter Fund
MC (Monitoring Consultant) Chernobyl Projects (T&A)
Colin Ross – Associate Director – QS, Risk and Finance, Chernobyl Projects
Anthony James Addington-Barker – Associate Director Nuclear Safety Project Specialist, Chernobyl Projects
Constantine Grechishkin – Programme Manager, Chernobyl Projects
George Leini – Quality Assurance Manager, Chernobyl Projects
Irina Smirnova – Controls Manager, Chernobyl Projects
Novarka (VINCI Construction and Bouygues Construction) Consortium
Nicolas Caille – Novarka Project Director (Bouygues)
David Coulet – Construction Director (Bouygues)
Baptiste Briois – Lead Engineer
Nicolas Guilcher – Radiological Engineer
Jean-Phillipe Gardeur – Deputy Construction Manager
David Driscoll – Health and Safety Manager
Don Kelly – Health and Safety Engineer
Irina Velichko – Health and Safety Supervisor
Ian Carling – Cladding Site Engineer
Rob Owen – MCS Crane System Manager
PMU Bechtel (Project Monitoring Unit)
Oscar “Mac” McNeil – PMU (Bechtel) Project Director (Lauren Dodd, Ron Hink)
Mike Bunner – Project Manager
Richard Hale – Contracts Manager
Rob Scott – Projects Control
Ron Lilley – Environmental Health & Safety Manager
Bernard Banat – Commissioning Manager
Sergey Deriuga – Technical Manager (amended)
Andrey Glukhov – Licencing Support Manager (amended)
Igor Gramotkin – Director of Chernobyl Nuclear Power Plant

Chernobyl New Safe Confinement, (NSC Arch) – Acronyms, Abbreviations & Terms

AF Axillary Facilities (Technological Building)
ALARP/A As Low As Reasonably Possible/Achievable
AS Annular Space
ASM Arch Sealing Membrane
ASRU Axillary Systems Reactor Unit
CDSD Concept Design Safety Document
ChNPP Chernobyl Nuclear Power Plant
ChTWG Chernobyl Technical Working Groups
CRAM Continuous Particulate Air Monitors
CRM Contractor Review Meeting
CSF Chernobyl Shelter Fund
DBE Design Base Earthquake
DCP Design Change Proposal
DS Deaerator Stack
EBRD European Bank of Reconstruction and Development
EC European Commission
EEB Electrical Equipment Building
FAT Factory Acceptance Test
FCM Fuel Containing Materials
FFFS Foam Fire Fighting System (FFFS)
FSA Fire Safety Assessment
FSAL Fire Subdivision (Safety) Access Lock
HVAC Heating Ventilation Air-Conditioning
IAEA International Atomic Energy Agency
IAG International Advisory Group
IAMS Integrated Automated Monitoring System
ICS Instrument and Control System
INSAG International Nuclear Safety Group
ISDB Integrated Shelter Data Base
ITR Individual Technical Review
Legacy structure Any of the original buildings present prior to the start of the NSCC Arch project
MTP Mobile Tool Platform
NSC New Safe Confinement; used as a term for the facility and includes NSC Arch, Main Crane System, Tech Buildings and all associated systems and structures
NSC Arch Used as a term for the Arch structure and cladding
OS Object Shelter, is sometimes referred to as the Sarcophagus or phase 1 legacy structure
PVT Performance Verification Test
RBMK Реактор Большой Мощности Канальный (Graphite-Moderated Nuclear Power Reactor)
RMS Radiation Monitoring Systems
TEC Building Technological Building 
TH Turbine Hall
TOC Taking Over Certificate


1. Chernobyl Accident: Updating of INSAG-1″ (PDF). IAEA. 1992. Archived (PDF) from the original on 20 October 2018. Retrieved 8 November 2018. Realised to atmosphere: Iodine-131, Caesium-137, strontium-90, Plutonium-241 (decays to Am-241.
2. International Competition, 1992 – Ukraine Government.
3. Smith, Stuart; Lacombe, Herve (February 1997). “A second shelter for Chernobyl: Its necessity and feasibility”. Proceedings of the Institution of Civil Engineers. 120 (1): 2–14. doi:10.1680/icien.1997.29157.
4. TACIS-Feasibility Study for the safe enclosure of unit 4 of Chernobyl Nuclear Power Plant.
5. NEA OECD – Chapter VIII Shutdown of the Chernobyl plant
6. Vinci and Bouygues sign contract to build Containment Shelter for the Chernobyl Sarcophagus” (PDF). Archived from the original (PDF).
7. ChNPP: Contract was signed on 10 August 2007, on 29 October 2007 works commenced.
8. MRT-078-00-Novarka April 2014-EN / СТР24 OF/ ИЗ24.
9. NSC-S15407-Novarka October 2014-EN.
10. Heavy lift crane (Potain MD 1100).



2. Reddit/Chernobyl
3.  EBRD
4. ChNPP Chernobyl Nuclear Power Plant

Certain elements within this article have been omitted for the purpose of confidentiality. All information herein is freely available to the general public, through EBRD, NOVARKA, ChNPP and General online media.

Nuclear Safety Projects & Radiation Science | Particle Physics | Fluid & Thermodynamics | Climate Variability & Environmental Science | Other areas of research: British (Royal) Etiquette | Social & Behavioural Psychology.