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The ancient Greeks discovered that everything was made of simple particles which they called atoms, but until the 20th century scientists didn’t realise that it could be split. The world’s scientists realised the technological significance of the fission of uranium-235, where the neutrons were put in evidence.
Unfortunately, the history of the early nuclear reactors was closely related to military technology. Though we cannot say that this is something special, the world’s first reactor and computer were developed in order to produce the first atomic bomb. Nowadays atomic energy has peaceful uses like low-cost electricity generation and it assists in the development of health care techniques.
The paper deals with a short nuclear timeline and the history of two nuclear power plants from East European countries.
At the beginning, researches on nuclear processes were performed in order to develop new applications.
1905 – All of us heard about the German physicist Albert Einstein (1879-1955) and his relativity theory. The most important result is the formula E=mc2 where energy is equal to mass multiplied with the square of speed of light. This also demonstrates that mass can be converted into energy.
1932 – John Cockcroft (1897-1967) and Ernest Walton (1903-1995), British physicists, work on splitting the atom with highly accelerated protons. Later on, in 1951, they win Nobel Prize.
1939 – Uranium atom is split with process named fission. Einstein’s theory is proven because some of the atoms mass convert into energy.
1939–1944 - Manhattan Project, the U.S. Army’s secret atomic energy program: with the direction of Robert Oppenheimer (1904-1967), scientists develop the first transportable atomic bomb in Los Alamos, and other teams produce the plutonium and uranium 235 which is necessary for nuclear fission.
1942 – Enrico Fermi (1901-1954) achieves the first self-sustaining nuclear chain reaction. Thereby the release of nuclear energy can be controlled.
1946 – The U.S. Army's Oak Ridge facility in Tennessee ships the first nuclear-reactor-produced radioisotopes for peacetime civilian use to Brainerd Cancer Hospital in St. Louis.
1948 – Announcing the plans of using nuclear energy to produce electricity for consumer use.
1951 – At the Idaho National Engineering and Environmental Laboratory (INEEL) the world’s first usable amount of electricity from nuclear energy is produced by an Experimental Breeder Reactor. Now the reactor is not operating and it is open for the public to visit.
1953 - The first experimental Boiling Reactor BORAX-I is built at INEEL. It is designed to test the theory that the formation of steam bubbles in the reactor core does not cause an instability problem. It proves that the formation of steam is, in fact, a rapid, reliable, and effective mechanism for limiting power. Thus it protects a well designed reactor against any uncontrolled event.
1954 – Atomic Energy Commission decides to give private companies the right to build nuclear power plants and to deal with nuclear materials.
1955 – BORAX-III supplies the town of Arco, Idaho (population 1,200) for more than an hour. It becomes the first nuclear power plant in the world to provide an entire town with all of its electricity.
1957 – Initially, the International Atomic Energy Agency consists of 18 member countries, now it has 130. Its goal is to promote peaceful uses of nuclear energy. Also, in this year, the first U.S. large-scale nuclear power plant begins operation in Shippingport, Pennsylvania.
In 2011, there are 432 nuclear power plant units in 30 countries of the Terra, operating with an installed electric capacity of 366 GW. Other 65 plants in 16 countries are under construction with an installed capacity of 65 GW.
The idea of constructing a nuclear power plant in Hungary was born in the 1960’s. To choose the perfect location for the power plant, technical and security issues were taken into account: the need of large amounts of water and the possibility of further development. Therefore, Hungarian state decided to build it near the Danube, Europe’s second longest river (Fig. 1).
It took a long time to finish this project:
- 1966 – The decision to build an atomic power plant.
- 1968 – Beginning of the works.
- 1975 – The final decision provides the construction with four reactors, each of 440MW.
- 1983 – 1987 – Starting of the four reactors.
- 1997 – Finishing the radioactive waste deposit.
- 1998 – Increasing the power of the reactor blocs to 470MW, by changing the condensers.
- 1999 - 2002 – Replacing the security system of the reactor with a modern digital one.
- 2005 - 2009 – Increasing the power of the blocs to 500MW
- Four pressurized water reactors, initially of 440 MW, now of 500MW.
- The total power of the power plant is 2000MW.
- The thermal power of each reactor is 1485MW; hence the efficiency is ~34%.
- The fuel used is uranium dioxide - UO2
- Nuclear energy covers ~40% from the electric energy necessity of Hungary.
- Price of energy: 0.05 €/kWh.
- Annual record: 15 427GWh.
- Fuel resource: Russia
- Increasing the lifetime of each reactor with 20 years, and further security measures.
- Plan to realize the fifth reactor
The components are (Fig.2):
1. Nuclear reactor
2. Steam generator
3. Circulation pumps
4. Nuclear fuel
5. Control rods
6. Volume compensator
7. Hydraulic accumulator
8. Hermetically sealed shield
9. Steam turbine
10. Water separator
12. Condense pump
13. Pre-heating system
14. Supply pump
15. Supply tank
16. Cooling water pump
18. Cooling water outlet
20. Electric transformers
21. Electric network.
|Nuclear power plant||Thermo-electric power plant|
|To produce an average of 5300 MWh annually, the first unit from Cernavoda uses 990 kg of UO2.||To produce the same amount of energy, a thermal plant consumes approximately 6 million tons of indigenous lignite.|
|The nuclear fission emits radiation and nuclear waste, which remains radioactive for longer than the life expectancy of governments and social institutions.||By burning the lignite, about 1.5 million tons of ash get into the environment, of which 20.000 tonnes of fly ash, 4 million tons of CO2 and significant amounts of SO2 and NOx.|
In the 1970´s, in Romania, the government decided to build a nuclear power plant. They decided to construct a power plant of CANDU type, in order to use the existent nuclear fuel, and the water from the Danube (Fig. 3).
It was a long procedure to finalize the nuclear power plant:
- 1979 – Signing the contract between ROMENERGO and Atomic Energy of Canada Ltd to design and produce the necessary equipment for constructing the first unit of the nuclear power plant.
- 1982 – Beginning the works on the first reactor, 1983 on the second, 1984 on the third and in 1985 on the fourth
- In 1996, the first unit was connected to the National Energetic System
- In 1999, the Full Scope Simulator was put in function for the first unit
- 2006 was the tenth anniversary of the exploitation of the first reactor
- 2007 the second unit was connected to the National Energetic System and the first unit is working continuously 300 days without any defects.
- Horizontal reactor with 380 pressure tubes
- It works with UO2 fuel cells grouped in 37 elements
- The fuel quantity is 93t of UO2
- Primary circuit:
- Input/output temperature in the reactor is 266 oC /310 oC
- Input/output pressure of the reactor is 11,13 MPa/9.89 MPa
With an installed power of 706 MW/reactor, the next two units are estimated to be finalised until 2015. The heavy water, used as moderator is produced by ROMAG from Drobeta-Turnu Severin, România. The fuel is produced at the Nuclear Fuel Factory from Piteşti, România. A comparison can be made between the impacts on the nature of a nuclear power plant and a thermo-electric power plant (Table 1).
To reduce environmental impact, at the Cernavodă nuclear power plant, several barriers are designed to protect and ensure operation in safety (Fig. 4).
In 2010, the first and second unit covers approximately 18% of the electric energy consumption of România.
The advantages of nuclear energy are given by the fact that the fuel is not as expensive as in the case of fossil fuels like coal and gases. Nevertheless it is cheaper to deal with nuclear fuel with approximately 10%.
The technical solutions must be developed in order to prevent any possible nuclear catastrophe. In all nuclear power plants, solid and liquid radioactive waste is produced necessarily during their operation. The minimization, management, processing, and final disposal of this waste are among the most important tasks of the atomic energy industry of the world.