Temelín Nuclear Power Plant Information Centre


Information Centre

A mediaeval knight would be surprised?

Located in the immediate vicinity of the Temelín Nuclear Power Plant, the renaissance manor of Vysoký Hrádek will not reveal what you would usually expect to see in a manor, yet even so, it has become a tourist attraction of the South Bohemia Region. The reason behind this is that the manor is now home to the Temelín Nuclear Power Plant Information Centre.

Do you know how to control a nuclear reactor? Do you know what yellow cake is or what can be observed in the cloud chamber? Just come to see us and have a look! We present an attractive journey to electricity from the atomic core in the midst of historic interiors.

There is a state-of-the-art moving-picture theatre in the Manor’s attic floor. The excursion to the Information Centre will start with the Travel to the Sun film. We will not reveal what is hidden behind the title in advance. The guide shall make your acquaintance, by way of computer presentations and animations, with the nuclear power plant function, its main facilities, and therefore with the basics of reactor physics and safety.

ETE - virtual tourStroll through the Nuclear power plant Temelín!

The programme includes a stereoscopic projection of the Mysterious Power movie, where you will look into the most interesting areas of the nuclear power plant, which undoubtedly includes the fresh fuel storage, reactor hall, and production unit machine room. The movie is watched through polarising specs which enable spacial vision. Among other interesting exhibits is a cloud chamber. You will have an opportunity to see through your own eyes how the environment in which we live is virtually interlaced with particles of natural ionising radiation (for detailed information please see the Cloud Chamber chapter).

And what else can you expect?

A large exhibition is also available interested visitors on the manor’s first floor. In the northern extension of the building you can take the opportunity to learn how nuclear power engineering issues are linked with the related and associated fields, such as the concepts of energy, various alternatives of acquiring its suitable forms, as well as both historical and physical contexts. More attention is then devoted to the energy hidden within mass (nuclear energy) and the principles of its release, and finally to the entire fuel cycle.

The second part of the exhibition in the southern extension of the building is devoted to the Temelín Nuclear Power Plant, its vicinity, functional layout, the most important facilities, and some issues related to the power plant operation. On 3D models you can see the building plan layout of the operating objects in the power plant area, the main production unit with its cross-section showing the most important equipment, the nuclear reactor representing the main part of the primary circuit, as well as the nuclear fuel for the fission process taking place in the reactor. You can further test your knowledge in an entertaining quiz game. There are trained personnel available to provide guidance throughout the exposition and some information leaflets and brochures are available for collection at the end of the visit.

Topical art and photography exhibitions are regularly organised for presentation to visitors, and we are currently preparing another exhibition for you.

We invite anybody interested in learning about the Temelín Nuclear Power Plant and its operation to the Information Centre.

The most frequent visitors are schools as the excursion is suitable as a supplement and variation of their physics or chemistry syllabus topics. All meetings are prepared adequately to the age and interests of a particular group of visitors. We may therefore recommend visits from the first grades of primary school. For secondary and further education schools, companies, and technically orientated members of the public, we additionally prepare specifically designed excursions that may include, if conditions allow, visits to the nuclear power plant premises themselves.

Excursions to the Information Centre should be arranged in advance by e-mail (infocentrum.ete {zavináč} cez {tečka} cz) or by phone (381 102 639). Groups may include between 5 and 50 persons.

For those who are interested in a free organised tour and for individual visitors, the Information Centre is opened daily (Saturdays and Sundays included) between 9 a.m. and 4 p.m., and between 9 a.m. and 5:30 p.m. during July and August. For individual visitors we offer the opportunity to see the exposition and the movie programme (the movie theatre is only accessible if there is no prior group arranged visit. Please contact us in advance if you want to ensure that the movie theatre is available at a particular time on a particular day). Typical start times for the program in the auditorium are: 9:30 a.m.,11 a.m.,12:30 a.m.,2.00 p.m., in July and August additionally at 3:30 p.m. Typical start times for the program in the auditorium are: 9:30a.m.,11 a.m.,12:30 a.m.,2.00 p.m., in July and August additionally at 3:30 p.m.

A visit to the Temelín Nuclear Power Plant Information Centre is free of charge for all visitors.

Please do not hesitate to contact us in case of any further query by e-mail, fax, or phone:

Information Centre

Temelín Nuclear Power Plant
373 05 Temelín - Power Plant

E-mail: infocentrum.ete {zavináč} cez {tečka} cz
Fax: +420 381104900

Phone: +420 381102639


Vysoký Hrádek Castle

The Castle Vysoký HrádekAccording to history books the courtyard, and later the fortress, were built by the Lords of Březí, who came from the court of Knín and Býšov. The first records we have are of Albert of Březí, who died in 1367. The fortress was inherited by his son, Svatomír, and then by another two sons of Albert, Smil and Bušek..

In the post-Hussite period after the line of the Lords of Březí had died out, the fortress, called Hrádek, passed into the hands of the related Lords of Býšov. In 1440, the name Oldřich of Býšov appears, followed by Jindřich of Býšov, elsewhere known as Jindřich of Březí, in 1507 and 1517.

In about 1520, Hrádek and the surrounding villages were acquired by the brothers Jan and Mikuláš Rendl of Úšava, who then sold the property in 1526 to a certain Jan Nebřehovský of Nebřehovice for 60,000 Bohemian groschen. The estate remained in the Nebřehovský family until 1556, when Ondřej Nebřehovský of Nebřehovice and of Pyšely (probably Jan’s son) sold Hrádek for almost 170,000 Prague groschen to the knight Zikmund Malovec.

Zikmund was the first in a line which owned Hrádek until the 19th century. The Malovecs were originally a yeoman family from the Netolice area who split into several branches in the pre-Hussite period. Zikmund came from the Libějovice branch, and inherited the fortress at Chvalešovice, along with Újezd and other small estates. He was a good husbandman and although he quickly sold Újezd, he made shrewd purchases of many other estates, including Hrádek. He died in 1577. In the process of dividing up his inheritance, Hrádek was given to Zikmund’s younger son Pavel Malovec; when Pavel died, Hrádek went to an older brother, Václav, who lived in Chvalešovice.Václav Malovec Liběšický of Chvalešovicewas a well-known figure in contemporary society. He enjoyed amicable relations with Petr Vok, to whom he lent money, and played a significant role at his funeral in 1611. Shortly before his death, Václav sold Chvalešovice to relatives (Václav Malovec Dříteňský the younger) in 1616, either to pay off debts or to relieve himself of the burden of running two estates, and kept Hrádek, where he had probably moved some time before.It seems highly likely that the fortress was given its Renaissance appearance by the ostentatiously living Václav, or perhaps the conversion was made beforehand by his brother Pavel, for whom Hrádek was his sole residence. The newness and the relative comfort of the estate may have been the key factors in the decision of the aging, childless Václav Malovec the elder to keep Hrádek.

Václav Malovec the elder died in 1617 as the last of his family lineage, and in his will of 1616 he bequeathed Hrádek and the surrounding villages to his aunt Anna Benedová of Vřesovice, as a widow’s advancement. Under this arrangement, Anna Benedová was to keep Hrádek undamaged and free of debt throughout her life, and if she had not remarried by the time of her death, the estate was to go to Zdeněk Malovec of Chýnov and Vimperk, from the Chýnov branch of the family, and on his death to his younger brothers Oldřich, Petr, and Jindřich, or to their firstborn sons or other members of the Chýnov branch.

It is not known how long Anna Benedová resided at Hrádek, but after her death, the fortress passed into the hands of Zdeněk Malovec’s eldest son, Pavel Malovec of Chýnov. After his death, Hrádek and all its chattels were acquired in 1666 by his brother Jan Oldřich Malovec of Chýnov, the commissioner of the Prácheň Region (1659 – 1676).

We will mention the subsequent owners of the fortress in brief. After Jan Oldřich it was inherited by his son Václav, the chief lieutenant of the Serfenberk Regiment, who fell in battle against the Turks in 1686. Hrádek then passed into the hands of his cousin Jan Bohuslav of Chýnov (Pavel’s son), as the oldest member of the family. He died in 1700, and his brother Vilém Arnošt (who died in about 1710) became the master of Hrádek. He was followed by his eldest son Ferdinand Ignác. Ferdinand served in the army and in 1749 he was appointed the commissioner of the Prácheň Region, and in 1760, by order of Marie Theresa, he was made a noble (together with his brother Arnošt Vilém and his cousin Josef František, the grandson of Jan Bohuslav).

After Ferdinand, Hrádek was inherited in 1760 by Arnošt Vilémas, the oldest member of the family, who was appointed an appeals councillor in 1731, the Lesser Quarter commissioner in 1743, and a councillor in the regional representation, chamber and sub-chamber from 1751 – 1764. He died in 1770, and bequeathed Vysoký Hrádek to his nephew Maxmilián Malovec, the son of Ferdinand Ignác. These frequent changes of owner clearly helped the old Renaissance fortress to retain its original appearance, because it is unlikely that any of the above-mentioned owners resided here permanently, preferring to stay at other family estates in Skalice, Vysoký Dvůř, Zdíkov, and Čestice.

After Maxmilián’s death, the next owner of Vysoký Hrádek was Václav Malovec, son of Arnošt Vilém, who acquired the estate under inheritance law in 1790. Under his ownership, the fortress was converted into a small castle, as depicted by the coat-of-arms of the Malovec line with the year and WM (Wenceslaus Malowetz) initials above the entrance to the castle.

After Václav, Vysoký Hrádek was inherited by his only son, František Malovec, when the estate had a value of 84,462 guilders. František was the last Malovec to own the castle (he died in 1842). He also served in the army and in 1825 sold Vysoký Hrádek to Josef Hirsch and his wife Barbora, Baroness of Lipov, for 65,000 guilders. In the description of Bohemia, written by J.G. Sommer in the 1830s, Vysoký Hrádek is mentioned as a castle with a Chapel of St. Anne and farming estate offices. The Hirsches were the first of several owners who were either of bourgeois origin or gentleman farmers, managing the estate independently, and the castle changed hands several times in quick succession, especially as of the end of the 19th century.

After the death of Josef Hirsch in 1843 and his wife in 1848, the estate was inherited by their son, also called Josef Hirsch, who remained the owner until 1882, when he sold it for 148,000 guilders to Václav and Anežka Wenzel. Vysoký Hrádek was then sold in 1894 to Josef Sailer for 306,000 crowns. Sailer managed the 328-hectare estate with a courtyard and distillery with the assistance from an adjunct, distillery director, gardener, and gamekeeper.

In 1914, under a market agreement, the castle became the estate of Matěj Kovář and his wife Antonie, and Jaromír Kovář, evidently Matěj’s brother, and Marie Antonieta Kovářová, who each acquired a quarter. The first land reform in 1919 did not affect the Hrádek estate – of the 355 hectares, only half a hectare was redistributed.

In 1925, Vysoký Hrádek was purchased by František Hromádko for 1,350,000 crowns, who sold it just a year later for 1,700,000 crowns to Hedvika Šulcová and Antonín Hynek, each acquiring half. However, this couple did not stay here long either, and in 1927 it was acquired by František and Antonie Zahradník. By this time, the estate included the castle and gardens, a distillery, commercial gardening, and 354 hectares of land – 131 hectares of fields, 18 hectares of meadows, 3 hectares of gardens, 8 hectares of ponds, and 192 hectares of woodland.

In 1933, Mr Zahradník sold Vysoký Hrádek to Václav Diviš and his wife Jindřiška, and soon after this the last structural changes to the castle were made. After Václav’s death in 1943, his wife and son Jan managed the estate. In 1948, the estate was confiscated as part of land reforms.

Following the departure of the Diviš family, Vysoký Hrádek and 50 hectares of land became property of the state. The estate and castle fell into disrepair; the gardens, restored by Diviš in his time as owner, suffered particularly severely. Ducks were bred in the greenhouses, pigs were let loose in the gardens, the castle roof leaked. Because the estate was so poorly managed, it was removed from the list of protected monuments. It was not until 1987 – 1989 that conservationists and the Municipal Museum in Týn nad Vltavou repaired the structure and installed new roofing. There were plans for the castle to become a depository for the Týn Museum. However, after the farming cooperative departed from the castle in 1986 – 1987, leaving behind it a works canteen, offices, and a nursery school, the castle fell victim to vndals and the museum cancelled this plan.

TThe castle was rescued from destruction by a sales contract concluded in 1994 between ČEZ, a. s. and the descendants of the last owners, the Diviš family, who won the castle back in the restitution process. Following large-scale reconstruction, in October 1997 the castle started serving the public as the Temelín Power Plant Information Centre.


Cloud chamber

The cloud chamber makes interesting viewing when visiting the Temelín NPP Information Centre. The observation area of the cloud chamber is 80 x 80 cm, which is the largest in the Czech Republic. In addition, the chamber design makes it possible to introduce artificial emitters and conduct interesting experiments in the observation space..

What is the cloud chamber used for?

Since time immemorial, ionising radiation has been present in the Earth’s biosphere. Live organisms came into existence and developed under conditions of the permanent effects of a natural radioactive background. From the sun, as well as from other stars in the universe, space rays arrive and radiation from radioactive elements such as geological formations, the air and water, etc., is one of natural contents of our environment and ourselves.

Human senses cannot perceive the ionising radiation, however, people have learnt to detect, distinguish, and exactly measure such radiation using various instruments. The cloud chamber is one of a few devices enabling the observance of radiation particles trajectories with only the human eye.

Which kinds of particles can we observe in the cloud?

The cloud chamber creates visible trajectories of electrically charged particles, which lose their high energy through a number of interactions with the atom electron shells of the working media in the cloud chamber (with those interactions positively charged nuclei and free electrons come into existence – we call this the ionisation process).

In addition, the types of radiation are stated, the traces of which are visible in the cloud chamber:

  • alpha-particle emission

The alpha-particle emission consists of 2 positively charged protons and 2 neutrons; identical with the helium nucleus. Alpha-particles are emitted by the nuclei of some unstable (radioactive) atoms, e.g., natural radioactive gas, radon, 222Rn, exists in the air, emitting alpha-particles during its decay. The majority of alpha-particle emission traces that we observe in the cloud chamber as strong short small clouds come from radon.  

  • beta-particle emission

The beta-particle emission consists of either electrons with a negative electrical charge (e-) or electrons with the positive electrical charge – positrons (e+). The highly energetic beta-particle emission comes from radioactive decay. High energy electrons may be additionally created by cosmic radiation collisions with atomic electron shells in the chamber. The high energy electrons leave narrow long traces and the lower energy electrons create irregularly curved  narrow short traces, cosmic radiation – mesons.

Energy rich radioactive particles fall into the Earth’s (atmosphere) from the sun and other stars – cosmic radiation. This radiation mostly consists of protons (hydrogen nucleus). During a collision with air molecules (N-14 nitrogen and O-16 oxygen) atomic nuclear fission occurs. Within the process, new nuclei and particles come into existence, which move further and may partially fissure with other nuclei. On the Earth’s surface (and therefore in our cloud chamber) only the radiation generated by these multifaceted secondary processes is visible. At the level of the terrestrial surface, 90% of the cosmic radiation consists of mesons. Mesons are electrically charged elementary particles, the mass of which is somewhere between the mass of electrons and protons. They have an extremely short life-span and disintegrate to, e.g., electrons and positrons. Mesons leave longer traces similar to the traces of alpha-particles.

  • cosmic radiation - protons

Protons are positively charged particles, which together with neutrons, represent the building particles of a nucleus; e.g., the hydrogen nucleus only consists of a single proton. On the terrestrial surface, protons occur as a part of cosmic radiation. They can additionally be created in the atmosphere during cosmic radiation collisions with air molecules. Traces of protons in the cloud chamber are similar to alpha-particles.

  • gamma rays

Gamma rays consist of high energy photons. Gamma rays usually accompany alpha or beta decay or result from cosmic radiation effects on the atmosphere. Gamma radiation photons do not carry any electrical charge and their traces, therefore, are not directly visible in the cloud chamber. They may, however, influence atoms in the cloud chamber, thus creating electrons, the traces of which can be observed directly.

An interesting experiment, e.g., is the attachment of uranite to the upper glass board of the chamber and the observation of multi-frequent traces of electrons released from electron shells of glass atoms as a result of the photo-electric effect.

How does the cloud chamber work?

The cloud chamber principle is based on the phenomenon of a thin layer of supersaturated vapour of isopropyl alcohol (2-propanol C3H8O) where a passing electrically charged particle causes ionisation – development of ions and unpaired electrons. On these ions along the particle path, the isopropyl alcohol vapour condenses into small droplets. We can see the droplet trace and according to their shape can identify which particle probably created the trace.

nabitá částice – charged article

průlet nabité částice prostředím par vytváří ionty – charged articles pass through the vapours producing ions

ionty – ions

páry alkoholu kondenzují na vzniklých iontech a vytvářejí tak viditelnou mlžnou stopu – alcohol vapours condense on the created ions producing a visible cloud track

Similarly, condensing traces are created behind airplanes flying at high altitudes, where the air humidity is close to the condensing temperature. Cloud traces are created either by a reduced air pressure above the wing surface or by condensation of water vapour contained in exhaust pipe fumes.

Diffusion cloud chamber design:

vytápění a odsávání iontů – ion heating and aspiration
pára – vapour
elektrické vytápění – electrical heating

kondenzát – condensate
vrstva přesycených par – supersaturated vapour layer
přívod pracovního média – operation media inlet
chlazení – cooling
pozorovací deska – observation board
odvod zkondenzovaných par – condensate vapour outlet

A temperature gradient is created between a moderately heated chamber lid and the intensively heated black observation board (down to approximately -30°C). A pump moves isopropyl alcohol in the chamber’s upper part into electrically heated grooves. The isopropyl alcohol evaporates in the grooves with its vapours diffusing downwards. At a height from 1-20 mm above the observation board, a layer of supersaturated vapours is created, where visible condensation traces are created after a charged particle passes. Developing traces are even more highlighted due to the lighting situated at the observation part perimeter. The greatest part of the credit for the diffusion cloud chamber design is to be given to an English physicist, Mr Charles Thomson Wilson (1869 – 1959), who was awarded the 1927 Nobel Prize for “development of methods making tracks of electrically charged particles visible by condensed vapours.”

C.T. Wilson was born to a farmer’s family in 1869. He was educated at Owens College (later renamed the Victoria College of Manchester) where he studied zoology, and at Cambridge University where he studied physics and chemistry. He worked at the Cavendish laboratory and a sun research observatory. In 1925, he became a professor of physics at Cambridge University. From 1895 he studied atmospheric electricity. After a radioactivity discovery, he worked on rain and snow radioactivity, which became the path to his vapour condensation research. Wilson worked out a new method of observation of various kinds of radiation through experiment and in 1913 he designed equipment enabling the visibility and photographic identification of the radiation tracks. In honour of this man, the name of the equipment has until now been Wilson’s Cloud Chamber. The cloud chamber helps physicists to register and observe the tracks of ionised particles and analyse their mass, electrical charge, and particle energy. It has become an indispensable part of nuclear physics and helped with discoveries of a substantial number of new particles.

Radioactive decay observation of 220Rn (thoron) gas:

Thoron is a gaseous element of a decay chain of thorium 232Th. The 232Th radionuclide came into existence during the initial synthesis of elements from which the planets of our solar system are composed. Only those with a sufficiently long decay period have been preserved to the current day. The most important radionuclides from the viewpoint of a natural radiation background are 40K, the natural uranium (238U and 235U), and 232 Th. Because all nuclei with a Z proton number exceeding 83 are radioactive, daughter products of uranium and thorium decay gradually and produce decay chains ending with a stable element – Z = 82 (Pb).

Decay chain elements additionally include isotopes of radon 219Rn, 220Rn, and 222Rn that belong to the main sources of the atmosphere and water natural radioactivity. Radon isotopes are released from ground formations and diffuse into the atmosphere, as well as into the subsoil water. Due to a substantially shorter decay period, thoron (220Rn) contributes to natural radioactivity to a smaller extent than 222Rn.

Following introduction of thoron into the cloud chamber we can easily observe a part of 232Th decay chain.

220Rn disintegrates according to the following schematic:

We can see a track of an alpha-particle emitted from the decay of 220Rn (decay period of approximately 55 s) in the cloud chamber, and an immediate second track of alpha from the decay of the daughter nuclei of 216Po (decay period of approximately 0.15 s). This paired sequence of alpha disintegration produces the characteristic “V”-shape tracks in the cloud chamber. Furthermore, we can statistically observe that the second track of the alpha-particle is longer than the first one due to the energy of the emitted alpha-particle being higher in the second decay. Another effect that we observe is the gradual reduction in frequency of observed alpha tracks because of the diminishing 220Rn initial quantity. Each 55 s, this amount decreases by half. In 10 decay periods (approximately 9 minutes) the quantity of radionuclides decreases about 1,000 times and we do not observe further traces of decay in the cloud chamber.

Poločas - period
Energie - energy
stabilní - stable

Has the observation in the cloud chamber caught your interest? Come to the Temelín NPP Information Centre. It would be our pleasure to show you the cloud chamber and, if you are even more interested in physics, we will demonstrate the described experiment with thoron for you.