The preconditions of the accident at the 4-th Chernobyl power unit
The preconditions of the accident at the 4-th Chernobyl power unit

It is necessary to at least briefly examine the events and processes that took place in nuclear science at the initial stage of the emergence of nuclear energy in the USSR in order to understand the prerequisites of such an epoch-making event as the accident at the Chernobyl nuclear power plant on April 26, 1986.

A lot of memoirs and scientific works were published, as well as problems, concerning, including the Chernobyl disaster – about the creation of atomic weapons in the USSR, the construction of the firstborn of the nuclear industry, the Mayak chemical plant and the Ural Atomgrad Chelyabinsk-40, as well as about the people who were implementing the Soviet atomic project.

When a radiation accident occurred in the South Urals in Chelyabinsk-40 in 1957, which set a whole series of completely new tasks for science, there had already been approaches to radioecology – the science of the interaction of nature and atomic energy.

Extensive experimental studies began in the country to study the patterns of radionuclide migration in natural environments and the effects of ionizing radiation on plants and animals back in the early 50-s of the last century. Radioecology developed at the initial stage in two directions: research in the field of radiation genetics and biology, which was conducted by Timofeev-Resovsky and research carried out by the Biophysical Laboratory of the Moscow Agricultural Academy named after Timiryazev – the first agricultural laboratory of the radiological direction in the country.

Similar studies were also conducted by institutions of the Ministry of Health, the Academy of Sciences, and the General Directorate for Hydrometeorology. An experimental research station was established to study the consequences of the accident and to develop scientifically sound recommendations after the accident in 1957, in May 1958, in Chelyabinsk-40.

Considering 25 years of experience in studying the consequences of the 1957 accident, in particular, the migration of radioactive substances on the territory of the East Ural radioactive trail, a report was prepared and published by the station team that was of great scientific and practical importance. It could be a necessary tool for the organizers of the liquidation of the consequences of the Chernobyl accident.

But, the document, issued by an extremely limited number of copies, has never become an effective tool for them. As noted in 1988 at the All-Union Scientific Conference on the Radiation Problems of the Chernobyl Accident, the lack of information about the Ural accident did not prevent incorrect research, which led to the low efficiency of the methods of decontamination and radiation protection of the population. Head of the Experimental Research Station G.N. Romanov told:

“Scientific research was actively conducted by the station team long before the Chernobyl accident. Almost all Soviet radio ecologists completed their practice at this station. First of all, the behavior of radionuclides in the environment, strontium-90, cesium, tritium, carbon-14, etc. was studied. The station employees performed a large cycle of scientific work to determine the sustainability of agriculture in a nuclear war.

Station employees did a lot to study and eliminate the Chernobyl accident. A complex radioecological expedition was created on the basis of the Experimental Station, which began its work in July 1986 in the territories of Ukraine and Belarus exposed to radioactive contamination.

And it had prepared a number of practical recommendations by the end of 1986. In particular, more than 85 documents were prepared to assess the radiation and radioecological situation in the 30-km zone, test methods and means of decontamination, and reduce the impact of the accident on the national economy and the environment”.

A significant place is occupied by issues related to nuclear reactors in the study of nuclear energy problems – their theory, design, calculation methods, technologies, the reliability of their protection systems, the development and operation of various types of reactors.

So, the RBMK reactor was the object of attention of scientists from the beginning of the 70-s. Various aspects of its operation were developed, in particular, a system for controlling the distribution and regulation of electricity, increasing the efficiency of uranium use, the features and experience of operating nuclear power plants with RBMK-1000 reactors, and prospects for expanding its use in nuclear energy were analyzed.

Moreover, the shortcomings of individual RBMK systems were known long before the Chernobyl accident. Particularly, the computational studies of RBMK control dynamics performed at the design stage, as well as the results of many years of operation of reactors of this series, led to the beginning of 1986 to conclude that the traditional automatic controller did not provide the necessary level of automation of the control process of modern power reactors with characteristic instability energy release. But this conclusion did not have time to affect the situation with RBMK at the Chernobyl nuclear power plant, while abroad, such arguments were taken more carefully.

International practice and safety culture

Most countries operating nuclear power plants significantly improved the culture of handling nuclear reactors in 1979, after the accident at the American Three Mile Island nuclear power plant. Some of their functional features were optimized, which increased safety not only in the nuclear industry, but also in many other hazardous industries.

At the end of 1986, academician Valery Legasov drew the attention of the country’s leadership to the creation in the United States of the American Nuclear Society “the Institute for the Operation of Nuclear Power Plants” with a permanent staff of 50-60 people. These were mainly highly qualified and experienced personnel, former engineer-operators, who, if necessary, were involved in solving problems of improving the operation of nuclear power plants, along with professors and engineers from the American Nuclear Society.

The authority of the Institute was very high due to its independence, high personnel competence, specific recommendations and, most importantly, the availability of complete information on operational defects of all western nuclear power plants and measures to eliminate them. However, such an independent structure had never been created in the USSR.

Security problems were the focus of attention of most international organizations in the pre-accident years, including they were also displayed in IAEA materials. The national academies of sciences of the Union republics of the USSR worked on this problem. A lot of scientific and design work was aimed at anticipating and preventing accidents at nuclear power plants long before the Chernobyl accident.

At the same time, situations arose when opposition to decisions on the deployment of nuclear energy facilities in certain territories was carried out. In particular, the scientists of Ukraine were not an obedient instrument of the political system. Moreover, the intensive planting of nuclear power stations in Ukraine had caused concern for the whole society.

These plans led to a scientific and reasoned protest at the Academy of Sciences. In the summer of 1980-s, a letter from the President of the Academy of Sciences of the Ukrainian Academy of Sciences, Academician B.E. Paton, on the inadvisability of the construction of the Chernobyl NPP-2 was handed over to the Council of Ministers of the Ukrainian SSR, and a year later his report “On the possible environmental and economic consequences of accommodation, construction and operation nuclear power facilities in the Ukrainian SSR” was heard at a meeting of the Presidium of the Council of Ministers of the Ukrainian SSR.

The efforts of scientists were not in vain, despite the negative reaction of the allied power structures to the memorandum filed by the Academy of Sciences of the Ukrainian SSR. Their practical result was the cessation of construction of the Odessa APEC, and subsequently of the Crimean NPP.

The result of the efforts of the Academy of Sciences of the Ukrainian SSR was a refusal to approve a plan for the placement of sites for the construction of the Kharkov APEC and nuclear power plant in the Donetsk region, on the coast of the Sea of Azov, and a number of other planned nuclear facilities in Ukraine. The efforts of Academician B.E. Paton and his colleagues stopped the increase in the number of power units at the Khmelnitsky, Rivne and South Ukrainian nuclear power stations.

The causes of the accident at the 4-th Chernobyl power unit

Interestingly, the Chernobyl nuclear power plant itself, the construction of which began in 1970, did not attract the attention of scientists before the accident. A new surge of attention to the Chernobyl NPP was observed only in 1984, when a number of publications appeared on the organization of concrete work on its construction, the scheme of mechanization of work during the construction of the main building of the second stage, the organization and conduct of installation works at the fourth power unit, as well as the use of prefabricated structures during the construction of the second phase of the Chernobyl nuclear power plant.

A phased summing up of certain results of the Chernobyl operation has begun since 1985. Experts knew the fact that the Chernobyl was operated with certain shortcomings. Ideas for improving nuclear power reactors were expressed not only in the theoretical works of scientists, but were also confirmed in practice.

So, the need to create a reliable, sustainable and mobile gas purification system for nuclear power plants, which was required by environmental protection, was directly expressed by the Chernobyl engineers. A number of significant shortcomings of the initial project were identified and eliminated thanks to their efforts in the construction of the second phase of the Chernobyl nuclear power plant.

All kinds of expert statements were made about the possible consequences of the nuclear boom in connection with the rapid development of nuclear energy as a branch of the country’s economic complex. Military doctors began to give special attention to the consequences of radiation exposures n connection with the proliferation of nuclear weapons and their possible use. The IAEA also worked in this direction. Researchers also continued to draw attention to the problems of the behavior of radioactive products in wildlife and their impact on it.

The development of nuclear energy has stimulated, in particular, the intensification of work in the field of radioactive pollution control in the areas where nuclear power plants are located. Since by the beginning of the 80-s it was assumed that the share of nuclear energy in the overall energy balance should increase sharply in the coming years, then, as a result, the capacities of individual nuclear power plants should increase, and their placement is close to large populated areas.

This increased the importance of any information on pollution levels. Specialists working in nuclear energy understood the complexity of the industry and were aware of the responsibility for its safety. It is not surprising that even such interpretations were given in the normative “Rules for the Technical Operation of NPPs” of those years:

“… Nuclear power is developing very quickly, faster than it has time to systematize and generalize fully the experience in operating equipment and systems of reactor plants. Emergencies are possible that are not provided by either the project, or the technological regulations, or local instructions. There are no predetermined and verified options for the sequence of actions and operations ensuring the safety of power units for such cases.

The most reasonable solution, possibly related to some economic losses, is to transfer the reactor to a deep precritical state, i.e. shutdown, in such situations. After that, you can safely, with the assistance of the necessary specialists, analyze the emergency, identify its causes and develop actions to prevent a similar situation in the future, while making the appropriate changes to the instructions…”

  • However, it was impossible to foresee by any instructions the situation that developed at the Chernobyl nuclear power plant, especially since problems of a socio-political nature were superimposed on technical problems.

The post-war period of the country’s social development was characterized by processes of both positive and negative nature. The rapid development of nuclear physics, the achievements of which were used both for military and for peaceful purposes, in particular in the development of nuclear energy, both in the former USSR and around the world, was one of those areas that received far from a mixed assessment.

Of course, recently the attitude to this industry of scientific and technological progress and the results of its implementation in economic life has undergone dramatic changes and has become extremely negative. But there was a period in the history of the Soviet state when its propaganda machine among the general population was instilled with a feeling of confidence in the absolute exclusivity of those achievements.

The pride, in particular, was the commissioning of the Obninsk nuclear power plant in 1954, which was the first experimental nuclear power plant in the world with a capacity of 5 thousand kW. The first nuclear power plant in the UK was commissioned only two years later, in 1956, and another year later, in the United States.

The RBMK reactor was used – a large-capacity channel reactor – during the construction of the Chernobyl nuclear power plant, begun in 1970. The developers of this reactor praised the positive aspects of their offspring. They, inter alia, noted that channel reactors have significant advantages over vessel reactors (VVER). At the same time, RBMK authors noted that uranium-graphite reactors have certain disadvantages, in particular, they are material-intensive and time-consuming during construction and installation.

They need a larger volume of the main building. But at the same time, issues of their reliability and level of security are not even mentioned among the shortcomings. In general, the attitude towards safety issues of RBMK-1000 was noted at that time with frank frivolity: “the reactors do not explode”, “the RBMK reactor is a samovar”, “NPPs with RBMK can be installed in the center of any city” – these are not the most daring estimates of the energy giant.

And this is despite the fact that there were other professional points of view regarding the functioning of this reactor. The Soviet physicist Ivan Zhezherun, a former employee of the Kurchatov Institute of Atomic Energy, warned of the possibility of an accident at RBMK due to design flaws, and therefore at the reactor of the 4-th Chernobyl power unit. Alas, he was simply squeezed out of the collective for such a vision of the “achievements of Soviet science”, declaring himself a mentally inadequate person.

Nevertheless, there was still a professional understanding of the safety problems of using a peaceful atom among experts in the nuclear industry, sometimes behind the scenes, notwithstanding the narrow departmental approach, the lack of criticism and a certain indifference to it by state structures.

But only a few experts sent their well-reasoned arguments, in particular regarding the insecurity of using RBMKs, to the higher authorities of the nuclear industry. An Inspector of the State Atomic Energy Supervision A. Yadrikhinsky is one of the few who was able to collect the whole complex of supporting facts and compose reasoned work on the dangerous moments that may arise during the operation of RBMK-1000 due to their design and technological features.

The main thesis of his document is “… there is no sufficiently clear practical substantiation of the nuclear safety state of RBMK reactors in the design documents and official reports of the RBMK Scientific Supervisor and Chief Designer”. However, attention to this document was paid only after the accident at the Chernobyl nuclear power plant.