Obninsk: number one13 July 2004
On 26 June 2004, it will be 50 years since the start-up of the world’s first nuclear power plant. What was it like to be there at the time? By Lev Kotchetkov
The world’s first nuclear power plant was built on the site of V Laboratory – Nuclear Center, established in 1946 (now State Scientific Center AJ Leipunsky Institute for Physics and Power Engineering), 100km from Moscow. This small nuclear plant has become a symbol of the peaceful use of atomic energy, and the date of its start-up has been universally recognised as the birthday of nuclear power.
The suggestion to use nuclear power for electricity generation was made repeatedly by academicians V I Vernadsky, S I Vavilov and P L Kapitsa before and during World War II, however, its implementation became possible only after successful tests of nuclear weapons in the Soviet Union in 1949 prompted a government decision in May 1950. General scientific supervision of the project was fulfilled by I V Kurchatov, who at that time was responsible for uranium management in the USSR. L P Beriya, the head of the Special Committee, was the general manager of the project and B L Vannikov, the head of the Primary General Department of the Council of Ministers of the USSR was responsible for flexible and efficient decision making. Professor N A Dollezhal, director of Niikhimmash Design Institute (now NIKIET) was appointed general designer of the plant and A I Gutov, director of the Leningrad Project Institute was appointed general architect of the project. From March 1951, general scientific supervision of the whole work programme on creation of the first nuclear power plant was fulfilled by D I Blokhintsev, the director of V Laboratory.
According to the design proposal developed under the guidance of I V Kurchatov, it was planned to construct a ‘trinity’ – a nuclear power plant with three reactors producing steam for one turbine, at V Laboratory. It was proposed first to construct the AM reactor (Atom Mirny – peaceful atom). The primary task was to choose the general concept and the main characteristics of the plant, which took six months of intensive work. The concept of a channel-type reactor with a graphite moderator and reflector was chosen. The reactor’s thermal power was 30MWt and the electric power of the turbine generator equal to 5MWe. Water was chosen as reactor coolant. Average water temperatures at the inlet and outlet of the reactor were respectively 190˚C and 280˚C, its pressure being 10MPa. The chosen parameters of the reactor coolant determined the use of stainless steel as the structural material of the core. In order to decrease the amount of stainless steel, which is a neutron absorber, it was decided to use a fuel element design with water flowing in the central thin walled, low diameter tube and uranium metal placed in the annular gap between the central tube and the external tube of stainless steel. Uranium metal cylinders were supposed to fit snugly on the central tube. On the outer surface of the central tube, special high thermal conductivity backing was provided. Four fuel elements and water supply downcomer were arranged in one fuel channel.
Four organisations were involved in the development of the fuel elements. Various materials were tested as deposited backing on the inner tube: nickel, copper and aluminum. However, these tests were unsuccessful. After that, lead-bismuth, sodium-potassium alloys, sodium, magnesium and calcium were studied as candidates for heat conduction matrix. Finally, a fuel element design was chosen employing two coaxial tubes (Ø 14x0.2mm and Ø 9x0.4mm) the annular gap being filled with uranium-molybdenum alloy grits and a magnesium heat conduction matrix. The fuel channel was designed as a long cylinder (6.775m) assembled of graphite elements surrounding four fuel elements and one tube for coolant supply to the bottom of the fuel elements. Coolant plenums were provided at the bottom and the top of each fuel channel. In the reactor core (h=1.7m, d=1.5m), there were 128 fuel channels and 23 channels containing reactivity control rods. Uranium enrichment of 5% was chosen, assuring 100-days reactor core lifetime.
Development of reliable fuel element design turned out to be the most serious problem. Final decision on the choice of fuel element design for fabrication was made only seven months before first criticality. Another problem was caused by the necessity to justify the reactor core’s neutronics and safety characteristics.
A number of factors caused permanent uncertainty and stress:
• The abundance of options in the core characteristics analyses caused by the large number of design approaches on the fuel channels.
• Absence of effective calculation equipment.
• Poor experimental data on the constants of the main nuclear reactions.
• Lack of verification by experimental studies of techniques of calculating resonance neutron absorption as applied to specific heterogeneous core structures, fast-fission factor etc.
The most difficult problem was the evaluation of the worth of water in the fuel and control rod channels, as well as water penetrating to the graphite work in case of channel failure. Analysis of such accidents was made upon formal completion of the plant design stage. The results of analysis showed that because of low grid spacing (120mm), which was not optimised in terms of moderator, in the case of five litres of water penetrating graphite work and its homogeneous distribution in the core, nuclear runaway would occur. So it was necessary to urgently create an experimental facility to study leaks of water and steam from failed tubes in fuel channels, as well as critical assembly for studies on reactor neutronics. Experimental studies did not confirm the worst hypothesis on the prompt homogeneous filling of the graphite work with water in case of fuel element tube failure. Detailed measurements of reactor neutronics parameters were made upon the loading of standard fuel channels to the AM reactor core and the reaching of first criticality on 9 May 1954. The reactor gained critical mass with 60 fuel channels containing water (as compared to 59 channels predicted by the analysis). Actual and predicted numbers of channels without water required for reactor criticality were respectively equal to 101 and 99. To designers’ satisfaction, experimental data on reactor neutronics were in good agreement with calculated values. On June 26, 1954, steam generated from nuclear fission energy was delivered to the turbine and the electric generator was connected to the Mosenergo grid. The world’s first nuclear power plant became a reality.
The Obninsk power plant was created in less than four years. This was possible due to the experience gained in the creation of the country’s first reactor plants, used for production of weapons plutonium, great support by the high level administration, involvement of the first-rate scientists and engineers of the country in solving related problems and engagement of experienced operating personnel.
The next thing on the agenda was mastering the reactor plant, assuring its reliability and safety, estimating economical parameters and using it as experimental base for future nuclear power development. These were hard days for the young operating staff.
A lot of design errors and defects in the components were revealed. The main problem was caused by the numerous water leaks through the cracks appearing in the tubes of the fuel channels as a result of chlorine corrosion of metal under stress. It was necessary to shut down the reactor for debugging. Upon completion of repair work and necessary modification, personnel managed to stabilise reactor operation, and reactor rated power level was reached on 25 October 1954.
Since the beginning of 1957, AM reactor operation was devoted to fulfilling research programmes on justification of the future nuclear power plant designs. Although utilisation of generated heat was going on, and production of isotopes was even enhanced, the main task was to carry out experimental studies on 17 test loops installed in the reactor. For the first time in our country, the following experience was gained on the AM reactor with test loops:
• Partial reactor refuelling was used, resulting in the increase of the fuel burnup by a factor of two.
• As applied to the first stage reactors of the Beloyarsk plant, conditions of hydrodynamic stability and reliable heat removal from the fuel elements in case of water coolant boiling were determined and verified, as well as conditions of safe transition from water heat removal to superheated steam heat removal mode. Also for these reactors, numerous tests of about 200 fuel elements of evaporator and superheater channels were conducted in order to assure generation of high pressure (10MPa) steam superheated in the reactor up to 510°C.
• Comprehensive studies on reactor transients under conditions of natural water flow were carried out as applied to the channel reactor design of the Bilibino cogeneration plant.
• Tests of about 100 thermionic fuel elements for BOUK and TOPAZ space nuclear systems were performed.
The plant was was accessible for numerous delegations from our country and abroad from the very beginning of operation. Training of operating personnel of many nuclear power plants (such as Beloyarsk, Novovoronezh, TES-3 transportable nuclear plant, the reactors of the Lenin icebreaker and two submarines), as well as specialists from China, Czechoslovakia, East Germany and Romania) were arranged at Obninsk.
The plant was in operation for 48 years, and no significant incidents resulting in personnel overdose or mortality occurred during this period. Nor were there any radioactive releases to the environment exceeding permissible limits. Operation of the reactor was terminated on 29 April 2002, and preparation work on its decommissioning is now underway.
L.A. Kotchetkov, State Scientific Center A J Leipunsky Institute for Physics and Power Engineering, 1 Bondarenko sq, Kaluga region, 249020, Russia
|In the name of humanism, welfare and justice|
One summer day, in 1951, half of the student group of the Department of Physics and Power Engineering at Moscow Power Engineering Institute left the local train at Obninskoe station to undertake our second practical training course. We followed a wheel track and footpath deep into the forest, and in 15 or 20 minutes we reached the place we had longed to be during our previous four years' study - and where many of us would have the luck to stay for over 50 years. It was in that year that the construction of the world's first nuclear power plant was started on the site of the Institute for Physics and Power Engineering (IPPE). The work on the project was initiated several years before by I Kurchatov, who was the scientific supervisor of the project. Also in 1951, the function of scientific supervisor of the project was relegated to the newly established team of the IPPE scientists and engineers. So in 1952 we students got our tasks for our diploma projects and in early 1953 we started our work as young specialists.
At that time we had only a dim idea of our future work. Moreover it seems to me, so too did our teachers. Certainly, we already knew that reactors include the core with nuclear fuel, reflector, moderator, biological shielding preventing ionising radiation impact, and absorber rods provided for reactor control. When we were in the fifth year of our course, Professor Feinberg delivered a sound course of lectures on the neutron physics, however, there were no practical techniques.
I was appointed as a member of the group headed by M Minashin dealing with analytical studies on the neutronics of the future reactor. It was a busy season, because only slightly over one year was left before the reactor start-up. Analytical and experimental studies, as well as design work were carried out in parallel. In the process of work, a lot of options arose. The work of our group was controlled almost every day by D Blokhintsev, scientific supervisor of the project and A Krasin, his deputy.
Not only we, but to a greater extent, institute management expressed their concern about there being almost no experimental support of analytical studies on reactor characteristics. The Obninsk test critical assembly simulating the core of the future reactor of the world's first nuclear power plant was constructed just during the reactor pre-startup period. It was located on the ground floor of the institute building below the office of the institute director.
Another division of the institute was involved in the design of the fuel element - the basis of reliable operation of the reactor. In order to check the quality of the fuel elements it was necessary to create a special test facility capable of simulating thermal and hydraulic parameters of the reactor core. This work was also original: the institute's high-pressure water test facility was created using fuel element simulators and electric heaters.
As early as 1952, the team of operators was established, and finalised formation in 1953. Among others, I was recruited into this group, and we worked hard, with enthusiasm. We studied the documents, controlled supplies and participated in the analytical studies required for revising parameters of the operating modes and in the construction work (for instance, in the graphite brick-laying) and worked out operating instructions.
I think even our generation would never understand how it was possible for the builders and riggers to carry out all this work during three and a half years. Certainly, we were all keen on the design approaches. Of course, we felt great responsibility to the senior managers and support and attention by the government authorities. Our reactor came to life for the first time on 9 May 1954 and, on 26 June, steam generated by the new energy type, nuclear energy, headed for very old Mosenergo grid turbines. How glad Kurchatov was with this event! When the reactor that came to life for the first time was put under automatic control and it was reported by the chief engineer for reactor control, Kurchatov threw up his cloth cap and exclaimed: "Hurrah, comrades!"
After that we had very hard working days, primarily because of our inexperience. I remember my distrust of the numerous switches and buttons. We needed automatism in actions, but we had to recall with torment the required switch, ways of control and interconnections. The multiple signals were annoying. Besides, because of the inexperience it was difficult to promptly identify the key information and make optimum decisions. Some uncertainties still existed in the interactions between the shift teams that had been just formed, and formal words of instructions on the rights and obligations had not yet become a reality. The reactor plant was in a fever, and we could not assure its stable operation. The visit of the government representatives was approaching, however we could not assure stable operation of the reactor in a specified mode for a day. Some were disappointed and others were just unbelievers. However, hard work gave its results: operating personnel worked with all their might. Qualification of the personnel increased. Specialists of the whole institute were involved in the solution of some problems. As a result, it became possible, first, to identify the causes of component failures and unstable operation of the plant and, second, to find the ways to its stabilisation.
At that time we were keen on the new interesting work, however most of the workers only later understood its importance. The first impressions were from publications expressing astonishment and disbelief from abroad, followed by a stream of delegations, the reaction of the First International Conference on the Peaceful Use of Atomic Energy, some impetuous enthusiasm of scientists from many countries and the appearance of national nuclear power programmes. Unforeseen political resonance was clearly revealed: a country ruined by a devastating war and intimidated with the nuclear weapons had completed an heroic deed. In a short time, this country concentrated its strength, means and scientific potential to solve, unaided, the most complicated scientific and technological problem and create its own nuclear shield, showing at the same time that our way was the peaceful use of the achievements of science.
The capacity of the world's first nuclear power plant is rather low, but the experience gained in its design, construction and operation, as well as results of studies cannot be overestimated. It should be emphasised that during 50 years of its operation there has not been any nuclear incident hazardous for personnel and inhabitants.
The years will pass and the remote light of the small reactor in Obninsk will shine brighter for the people as a symbol of our achievements and a triumph of our principles of humanism, welfare and justice.