The HBO/Sky mini-series Chernobyl is a stark reminder of the immensity of the accident that destroyed unit 4 in 1986. It vividly recalls the pain and suffering of those people, in particular, who tried to address the consequences of the accident in the first few days and weeks. But Chernobyl also clearly highlights how a culture of secrecy and obedience contributed to the accident and hampered efforts to deal with its aftermath.
Soviet authorities knew about precursors to the Chernobyl accident but did not share this vital information with operators, who were ordered to run the fatal test without sufficient knowledge about unstable core conditions. A key reminder, if one was needed, is that an effective nuclear safety culture requires well-informed and empowered operators and transparency as well as competent, independent oversight.
While Soviet authorities eventually managed to get unit 4 into a relatively stable state by using hundreds of thousands of 'liquidators' to cover the reactor with what became known as the 'object shelter', the site remains a radiological and technical challenge to this day. If one good thing came out of the Chernobyl disaster, it was the unprecedented international cooperation and solidarity to tackle the consequences of the accident and the cooperation on nuclear safety issues in general. The international community, including the EBRD, has engaged with Ukraine on the various challenges posed by the Chernobyl site since the mid-1990s.
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One of the first tasks was to finance safety and security upgrades at the sister unit, immediately adjacent to the shelter, which almost unbelievably continued producing electricity until the year 2000. Permanent closure of units 1 to 3 was a clear demand by the international community and, when achieved, it was the first major improvement at the site.
In 1997, the EBRD agreed to set up a Donor Fund to finance the Shelter Implementation Plan - a strategy to transform unit 4 and the shelter into an environmentally safe condition. This task came to be supported by 45 donor governments and the EBRD, even though at the time the exact scope, schedule and cost were tentative. The first phase consisted of studies to determine the radiological situation in various parts of the object, the structural stability of the shelter (which had been built quickly using remote technologies as far as feasible), and the possibility of criticality in the destroyed core. What slowly emerged was the outline for a strategy including the construction of a New Safe Confinement (NSC) to enclose unit 4, including the old shelter.
A possible collapse of the shelter was the biggest risk to the success of the programme and it could have jeopardised finding a sustainable solution for decades. A priority, therefore, was the design and implementation of measures to stabilise the shelter to minimise that risk. Before the sliding of the NSC, the most visible feature in recent years was a gigantic yellow steel structure to stabilise the western wall of the shelter and to take off most of the weight of its roof. That was one of a dozen measures implemented inside and outside of the shelter, and carried out under extremely difficult radiological conditions, which helped extend the lifetime of the old structure.
In parallel, the design for the NSC took shape. One of the requirements was to assemble this structure of more than 100 meters high and 250 meters wide, away from the shelter and to slide it into place once completed. This was necessary to keep radiation exposure to workers to a minimum. A consortium of French companies, Vinci and Bouygues, accomplished this feat. By the end of 2016, the arch-shaped steel structure, complete with a sophisticated crane system, ventilation ducts and cabling for monitoring and control systems, was slid into position over unit 4. The completion of the structure’s sealing and commissioning of all systems was achieved in April 2019.
This successful operational test is a game changer for Chernobyl. Now, with the NSC in place and with a design life of 100 years, the conditions have been created to take the next steps.
The NSC protects the old shelter from the elements, further reducing the collapse risk and stopping water ingress. Thanks to its sophisticated ventilation and filter system, the Confinement also keeps radioactive aerosols and tons of contaminated dust contained. As a consequence, radiation levels on the outside have dropped dramatically. The crane system will allow dismantling of the old shelter - starting with those parts deemed to be particularly unstable - and, ultimately, the removal of materials from the molten core as intended by Ukraine's authorities.
During implementation of the Shelter Implementation Plan, the programme has applied best international practice in radiation protection and has achieved an outstanding health and safety record.
Thanks to this international effort, Chernobyl is now in a much better shape than it has been for the last 33 years. But it remains a challenging place. Used fuel from units 1 to 3 is stored in a Soviet-era wet storage facility that needs to be decommissioned. Transport of fuel assemblies to a new dry interim storage facility, also funded through an EBRD-managed Donor Fund and EBRD’s own resources, is expected to start before the end of this year. Ukraine will have to decommission Chernobyl units 1 to 3, operate the NSC and waste management facilities (most of which have been funded by international donors), develop an integrated waste management strategy and manage the exclusion zone, large parts of which will not be released for general use for decades to come.
Ukraine has made huge progress in its approach to nuclear safety, as also demonstrated by the upgrade programme in its operating nuclear power plants, which is part-financed by EBRD. This progress encompasses not only experience in the management of complex programmes, but also risk-informed regulatory practices and excellent radiation protection standards, which would possibly not have been achieved without international cooperation.
Future work in Chernobyl would greatly benefit from continued international cooperation due to the scale of the task, and including a number of unique challenges. Today, Ukraine would of course no longer be the recipient of technical assistance in dire need of international solidarity that it was when the country emerged from the Soviet Union with the worst nuclear legacy in the history of mankind. Future cooperation will need to be a partnership, the foundation of which has been successfully created by Ukraine and the international community by solving key technical challenges in Chernobyl.
Balthasar Lindauer is Director of the EBRD's Nuclear Safety department.
This article was first published by World Nuclear News.