The Chernobyl accident: is it the RBMK reactor?

The explosion at the Chernobyl nuclear power plant was associated with the use of RBMK – a high-power channel reactor. Due to the fact that in the world nuclear energy the choice was made in favor of other types of reactors, the question arises, why did RBMK get mass distribution in the USSR?

Answering this question, experts first of all emphasize that water-cooled uranium-graphite systems are the simplest and most technological points of view – the most affordable.

The developers nicknamed RBMK “the Soviet national type of reactor” in their narrow circle. It had its advantages and was highly appreciated in the light of the specific aspect of the development of the economy inherent in the USSR, namely, an attempt to achieve great effect at the lowest cost.

The creation and operation of an industrial facility, which includes a nuclear power plant, always takes place in competition between the achievement of the desired effect and the costs of its creation and further operation. Unfortunately, the struggle to achieve the effect with the lowest costs is far from always beneficial in the long run.

The savings on safety features in the design of nuclear power plants with RBMK reactors and research on its safety led to the sad consequences of April 1986.

Where was the manual looking at?

The leadership of the state, like the leaders of the nuclear industry of the late 70s-80s, had no doubts about the safety of the achievements of scientific and technological progress.

That is why, even before the Chernobyl accident, the Ministry of Energy of the USSR raised the question before the Council of Ministers of the Ukrainian SSR about the need for accelerated construction of the second stage of the Chernobyl nuclear power plant at a distance of only 11 km from the existing nuclear power plant.

Of course, even this idea itself was categorically denied after the events at the Chernobyl nuclear power plant. The formal motive for the refusal was that “the Ministry of Energy is designing new nuclear power plants without approving a promising layout of nuclear power plants, which would take into account the whole range of environmental and economic issues related to the development of nuclear energy”.

Archival documents attesting to the facts of the alleged construction of the Chernobyl NPP-2 in the Kiev region provided a whole range of arguments regarding the “inefficiency and harmfulness” of this project. In particular, in the arguments against, it was about the tense water situation that prevailed at that time in the Dnieper river basin.

In addition, the station in this area required the destruction of about 3.5 thousand hectares of forest, and the construction of a cooling pond on an area of about 3 thousand hectares could cause flooding, including reclaimed land.

It was also emphasized that the deployment of the new nuclear power plant was supposed to be exactly where there had already been an excess of generated electricity. Moreover, there were no cases of building more than four power units at one site in the world practice of building nuclear power plants at that time.

It was concluded after a number of scientific and technological arguments from Ukrainian experts that the construction of the Chernobyl NPP-2 was highly undesirable and that such an experiment was unacceptable near Kiev.

This was perceived by some members of the party-bureaucratic elite as evidence of the resistance of Ukrainian specialists to the state course of nuclear energy development, which, as you know, was instilled by force from the central authorities.

The situation at nuclear power plants in Ukraine caused serious concern. The Ministry of Atomic Energy of the Ukrainian SSR has archival correspondence dated to the end of 1986, which allows us to understand the accident’s background, including the sloppy approach to the location, construction and configuration of nuclear power plants:

“The Chernobyl accident, the practical and organizational work to eliminate its consequences require a more careful analysis of the state of affairs at the NPPs currently operating in the republic and those under construction.

The fact that the operation of many existing and the construction of new nuclear power units continues in the presence of a large number of design flaws and miscalculations, a low degree of reliability of parts of domestic equipment and assemblies, the quality of their manufacture, and also with certain omissions during construction, installation and repair work, is a matter of concern”.

It was also noted that the unacceptable vibration of the main steam pipelines and de-aerating feed tanks that were in operation without being even accepted by the Interagency Commission continues in all VVER-1000 type reactors.

By the end of 1986, only 10% of the 120 types of new equipment for nuclear power plants with VVER-1000 reactors had passed interagency tests, and 90% of the equipment was tested only in the course of commissioning during the operation of power plants.

The situation was critically assessed when the Chief Designer, Scientific Director and General Designer of nuclear power plants belonged to different departments, and NPP projects themselves were sometimes created by separate departments that did not specialize in nuclear topics. In addition, the Ministry of Geology of the Ukrainian SSR identified a number of significant shortcomings and omissions in engineering and hydrogeological studies.

Thus, although it was too late, the Soviet society nevertheless worked out the instinct of self-preservation after the terrible tragedy at the Chernobyl nuclear power plant in April 1986, it began to listen not only to the voices of universal approval, but also to alternative thoughts of sensible scientists and production workers.

This is especially indicative of the fact that the entire world community, united in 1957 into the International Atomic Energy Agency in the course of the ten-year development and functioning of atomic energy. In the course of its activities, the Agency has developed standard requirements for all parameters for the development, construction and operation of nuclear power plants and other enterprises of the nuclear industry and, most importantly, for monitoring the safety of their exploitation.

A similar specialized state structure – the State Service for Atomic and Energy Supervision – was created only in 1984 in the former USSR. And that’s what was entrusted with the monitoring of safety in the field of nuclear energy and the creation, together with manufacturers, of normative and technical documentation, rules and norms that could guarantee complete energy security.

But, as it often happened in the Soviet Union, the system of interdepartmental structures and the distribution of functions between them was not clear enough to work highly efficiently.

As for the production life of the Chernobyl NPP staff on the eve of the accident, the personnel of the Chernobyl NPP began the 1986 with great hopes for the future.

Four units of the first and second phases worked at high power, the construction of the third stage – power units № 5 and № 6 with RBMK-1000 reactors – was completed, the construction of the fourth stage – power units № 7 and № 8 with RBMK-1500 reactors – had begun. Soon, the station should become the most powerful in the world.

However, manufacturers were disturbed by power units № 3 and № 4, which lagged behind the first stage in power generation. The task of raising electricity production to the intended level was not succeeded in solving. Obviously, precisely for this reason, the Ministry decided to conduct an experiment at power unit № 4, which was connected specifically with the problem of increasing energy production in the reactor core without changing other parameters of the unit.

It was a physical experiment in the reactor itself, therefore, given the existing norms of the Soviet control system, all data on it belonged to the category of “top secret”. This state of affairs in the nuclear industry of the USSR was absolutely ordinary and normal and did not raise any objections. Due to the fact that it was planned to stop power unit № 4 at the end of April for scheduled repairs, the preparation and conduct of work in the core were tied to this very moment.

On April 1, 1986, preparation for the experiment in the core began, when unit № 4 was operating at a capacity that was within the framework of -104.7% of the design and 102.6% of the nominal. Actual data on fuel overload in the reactor and changes in the parameters of the active zone (AZ) during April 1-23, 1986, allowed technical experts to establish the purpose of the experiment and methods for its implementation.

They believed that the preparation ended on April 23, when the capacity was 102% of the nominal, and the parameters of the AZ corresponded to the experimental program. On the same day, a group of scientists arrived from Moscow to the Chernobyl nuclear power plant to conduct this particular experiment. Given the fact that the test process itself was related to “classified information”, these specialists were incognito at the station, contacting only a limited circle of personnel.

However, a memoir published in 1998 in Moscow by scientists of the Institute named after Kurchatov has information about who exactly and when he arrived at the Chernobyl nuclear power plant, where he lived, what he did when he left. This fact completely refutes the official statement that the Chernobyl personnel did not coordinate their actions with the authors of the reactor. The authors themselves were at the Chernobyl nuclear power plant and would not allow the staff to do anything without their knowledge.

Chernobyl was not ready to stop the fourth power unit, to conduct an experiment and tests on April 25, 1986

Not all participants in the work arrived at the station, not all technical issues were resolved. The director of the station, V.P. Bruchanov, tried to convince the Ministry for two days in a row to transfer the test to the 4th power unit. However, the importance of the experiment outweighed his arguments. On April 24, 1986, he signed the corresponding order, which the clerical service even missed to print on time.

By the way, an analysis of leading experts who inspect the design documentation for the second stage of the Chernobyl nuclear power plant showed that there are serious shortcomings in creating a reliable, highly efficient and highly automated control system for nuclear power units equipped with RBMK reactors.

It is difficult to talk about the high reliability of the overall power unit control system; the volume of automated control processes is extremely low. The NPP general safety provisions define the requirements for the monitoring and control systems of the NPP unit as follows: “A nuclear power plant must be constructed in such a way to provide the most favorable conditions for operational personnel to make the right decisions for its management and to minimize the unforeseen possibility of making incorrect decisions”.

That is, the main management function, decision-making, is transferred to the staff, and the concept of “a minimum of incorrect decisions” is introduced. It is hard to understand what this means. Thus, the developers of the principles of managing the unit and its safety, without even wanting it, have already determined the guilt of the personnel in the event of an emergency.

Given all the above, it is necessary to add the functioning of the totalitarian political system in the USSR, with the absolute power generated by it and the ideological monopoly of the center, to the number of socio-political prerequisites that generated technical problems and, ultimately, led to the most massive technological disaster of the twentieth century.

Ignoring the alternative knowledge, suggestions and thoughts inherent in the totalitarian system formed confidence in the absolute rightness of some and indifference of others, who understood the impossibility of influencing a particular situation. The logical stage in this chain was the formation of negligence and restraint of social attitudes.

The extrapolation of such sentiments, the detached attitude to public life and industrial indifference towards such an important problem that atomic science and technology and, in particular, atomic energy were and remain, caused constructive and technological flaws in the design and construction of RBMKs.

This, in turn, led to shortcomings in the development of regulatory documentation and certain omissions in the training of operating personnel, which, for its part, caused an accident at the fourth power unit of the Chernobyl nuclear power plant on April 26, 1986.