SAFETY & SECURITY | CHORNOBYL 40 YEARS ON
Requiem to Chornobyl
Forty years ago, an event took place which continues to cast a long shadow over the nuclear industry. Today Chornobyl is a by-word for nuclear disaster, but what is the real legacy of the world’s most infamous power plant?
By Olexiy Kovynyev
contrast RBMK reactors were intended to be the power reactors of the future with no military applications. The RBMK used graphite as a moderator and water as both a coolant and partly a moderator and the first design solutions were tested on the AMB experimental power reactors located at the Beloyarsk NPP. The first unit with an RBMK-1000 reactor was unit 1 at the Leningrad NPP which began operations in 1973. Leningrad 2, Kursk 1 & 2, and Chornobyl 1 & 2 followed using the same design, six units in total. These were the first generation of RBMK plants, which featured separate reactor buildings. The second generation had improved safety systems
and was of a double unit design. This design was used for eight units: Kursk 3 & 4, Chornobyl 3 & 4, Smolensk-1, 2 & 3, and Leningrad 3 & 4. In total, 17 RBMK reactors were commissioned including the RBMK units at Ignalina in Lithuania. Here units 1 & 2 were RBMK-1500 reactors with the core power, and consequently the power of the units, increased by 1.5 times. The reactor’s overall dimensions and design remained unchanged though. However, highly uneven power density led to cracking of the fuel rod cladding and the operating power was reduced to 1300 MWe. In the early 2000s, Ignalina’s RBMKs, which generated over 80% of Lithuania’s electricity, were shut down as part of the country’s accession to the European Union. The core of the RBMK is a cylinder 7 metres high and about
The destruction of unit 4 at Chornobyl had far-reaching consequences that are still being felt today. Source: The Bulletin of the Atomic Scientists
ON 26 APRIL 1986 THE EXPLOSION of unit 4 at the Chornobyl nuclear power plant changed the world. Some 30 people died in the immediate aftermath of the blast, but its aftershocks were felt around the world. Today the events of Chornobyl 40 years ago continue to reverberate and it will remain a monument to nuclear risk for generations. But beyond the headlines, the legacy of Chornobyl is far more complex.
The origins of disaster: Birth of the RBMK The origins of the ‘Reactor of High-Power, Channelled 1000 Megawatt’ or RBMK-1000 units, four of which were eventually built at Chornobyl, was a bulky reactor design having inherited its main features from Soviet military reactors. Development of these reactors began in the mid-1960s. In
34 | April 2026 |
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12 metres in diameter. It is thus almost 30 times larger in volume than the VVER/PWR reactor core of the same power. Channels containing assemblies and water pass through columns constructed from square-section graphite bricks – a total of 1661 channels, with monitoring and controlling of flow rates and thermal parameters in each one. An RBMK reactor operator continuously modifies the power density field in different parts of the enormous reactor, despite (and sometimes due to) the assistance of the local power controller. A fuel reloading in one of channels required additional significant effort from the operator. Nevertheless, the RBMK reactor design remained operational until the end of its planned service life and was even extended in some cases. Due to the common design features of these reactors
the core could be significantly enlarged, so the RBMK-2000 designs, including those with a parallel piped-shaped core, seemed feasible leading to the RBMK-2000, RBMK-3600, RBMKP-2400 and RBMKP-4800 designs.
Advantages and deficiencies From a modern perspective, RBMK reactors seem like the embodiment of technological imperfection, if not devilish
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