Information Centre of The Temelín Nuclear Power Station

• Information Centre
• The Castle Vysoký Hrádek
• Cloud chamber

Information Centre

Mediaeval knight would be surprised?

In the immediate vicinity of The Temelín Nuclear Power Plant, there is located a renaissance manor of Vysoký Hrádek.You would not see anything inside from what would usually be in manors and even though, the manor has become a tourist attraction of the South Bohemia region. The reason being, actually, that it is the place where Information Centre of The Temelín Nuclear Power Station is situated.

Do you know how to control a nuclear reactor? Do you know what a yellow cake is or what can you observe in the cloud chamber? Just come to see us and have a look! In historical interiors, we present an attractive journey to electricity from the atomic core.

In the manor attic floor, there is a state-of-the-art moving-picture theatre. The excursion to the information center we start with the Travel To The Sun film. What is hidden behind the title, we shall not reveal in advance. The guide shall make you acquainted, on computer presentations and animations, with the nuclear power plant function, its main facilities, and therefore with basics of reactor physics and safety.

The program includes a stereoscopic projection of the Mysterious Power movie, where you will have a look into the most interesting parts of the nuclear power plant, which undoubtedly are the fresh fuel storage, reactor hall, and production unit machine room. The movie is watched through polarizing specs, providing for a space vision. Among other interesting exhibits, there is a cloud chamber. You will have an opportunity to see on your own eyes, how the environment, where we live, is virtually interlarded with particles of natural ionising radiation (for detail information please see the Cloud Chamber chapter).

And what else can you expect?

At the manor first floor, there is a large exhibition available, for all those, who are interested. In the northern extension of the building, you can take the opportunity to learn, how the 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, then, is devoted to energy hidden in the mass – nuclear energy, principles of its release, and finally, to the entire fuel cycle.

The second part of the exhibition in the south extension of the building is devoted to The Temelín Nuclear Power Station, 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 showing layout arrangements of the operating objects in the power station 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. Apart from it, you can test your knowledge in an entertaining quiz game. There is trained personnel available providing guidance during the entire exposition visit. At the end of the visit, you can pick up some information leaflets and brochures.

Apart from other events presented to the visitors, some topical art and photography exhibitions are organized; at present, we are preparing for you another exhibition.

We invite to the information center everybody interested in learning about The Temelín Nuclear Power Station and its operation.

The most frequent visitors are schools, for which 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 recommend, therefore, the visit from the first grades of the primary school. For secondary and further education schools, companies, and technically orientated members of the public, we naturally prepare, in addition, specifically designed excursions, that may include, if conditions allow, visits to the nuclear power plant premises themselves.

The excursion to the information center is to be arranged in advance, by e-mail (infocentrum.ete@cez.cz) or by phone (381 102 639). A group may include 5 persons, as the minimum and 50 persons, as the maximum.

For those who are interested in a freely organized visit and for individual visitors, the information center is opened each day (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 program (the movie theatre is only accessible if there is no group visit arranged in advance. Please contact us if you want to make sure that the movie theatre is available on a particular day and at a particular hour).

A visit to the information center of The Temelín Nuclear Power Station is free of charge for all visitors.

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

Information Centre

The Temelín Nuclear Power Station
373 05 Temelín - Power Station
E-mail: infocentrum.ete@cez.cz
Fax: +420 381104900

Phone: +420 381102639

The Castle Vysoký Hrádek

According to the 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 news we have is of Albert of Březí, who died in 1367. The fortress was inherited by his son, Svatomír, and then by two other 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, but in the pre-Hussite period split into several branches. 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 the 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 Chvalešovice was 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 to 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 branch, 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 (in 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’ 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; 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 in 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 the initials WM (Wenceslaus Malowetz) 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 served in the army and in 1825 he 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 offices of a farming estate. The Hirsches were the first of several owners who were either of bourgeois origin or gentleman farmers, managing the estate independently, and the castle changes hands several times in quick succession, especially as of the end of the 19^th 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 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,each acquiring 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 Hromádkofor 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’sdeath 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 vandals, so the museum had to cancel this plan.

The castle was rescued from destruction by a sale 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 information centre for Temelín Power Station

Cloud chamber

When you visit NPP Temelin Information Center, there is interesting equipment to se -the cloud chamber. 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 possible to introduce into the observation space artificial emitters and conduct interesting experiments.

What is the cloud chamber used for?

Since the very beginning, ionizing radiation has been present in the Earth biosphere. Live organisms came into existence and developed under conditions of permanent effects of natural radioactive background. From the sun, as well as from other stars in the universe, space rays come. Radiation of radioactive elements from geological formations, the air, the water, etc., is one of natural contents of our environment and ourselves.

Human senses cannot perceive the ionizing radiation, however, people learn to detect, distinguish, and exactly measure such radiation, using various instruments. The cloud chamber is one of a few devices enabling to observe trajectories of the radiation particles just by human eyes.

Which kinds of particles can we observe in the cloud?

The cloud chamber makes visible trajectories of electrically charged particles, which loose their high energy through a number of interactions with 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 a ionization process).

In addition, types of radiation are stated, 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; is identical with the helium nucleus. Alpha-particles are emitted by nuclei of some unstable (radioactive) atoms. E. g., natural radioactive gas, radon, ²²²Rn, exists in the air, emitting alpha-particles during its decay. And majority of alpha-particle emission traces, that we observe in the cloud chamber as strong short small clouds, come from the radon.  

• beta-particle emission

The beta-particle emission consists of either electrons with the negative electrical charge (e^-) or electrons with the positive electrical charge - positrons (e⁺). The highly energetic beta-particle emission comes from the radioactive decay. High energy electrons may be created, in addition, 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 narrow short traces, irregularly curved. cosmic radiation - mesons

From the sun and other stars, radiation of energy rich particles falls on the air envelope of the Earth (atmosphere) – the cosmic radiation. The radiation mostly consists of protons (hydrogen nucleus). During a collision with air molecules (N-14 nitrogen and O-16 oxygen, in fact) atomic nucleus fission occurs. Within the process, new nuclei and particles come into existence, which move further and partially may fissure other nuclei. On the Earth surface (and therefore in our cloud chamber, too) is only visible the radiation generated by these multifaceted secondary processes. 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 extremely short life-span and disintegrate to, e. g., electrons and positrons. Mesons leave longer traces, similar to traces of alpha-particles.

• cosmic radiation - protons

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

• gamma rays

The 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, traces of which we can observe directly.

An interesting experiment, e. g., is an attachment of a uranite piece to the upper glass board of the chamber and an observation of multi-frequent traces of electrons released from electron shells of glass atoms, due to 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 vapor of isopropyl alcohol (2-propanol C₃H₈O) where a passing electrically charged particle causes ionization – development of ions and unpaired electrons. On these ions, along the particle path, the isopropyl alcohol vapor condenses to small droplets. The droplet trace we can see and according to its shape we can identify, which particle probably created the trace.

nabitá částice – charged articleprůlet nabité částice prostředím par vytváří ionty – charge article pass through the vapors produces ionsionty - ionspáry alkoholu kondenzují na vzniklých iontech a vytvářejí tak viditelnou mlžnou stopu – alcohol vapors condense on ions created, thus producing a visible cloud track

Similarly, condensing traces are created behind airplanes flying in 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 vapor contained in exhaust pipe fumes.

Diffusion cloud chamber design:

vytápění a odsávání iontů – ion heating and aspiration
pára – vapor
elektrické vytápění – electrical heatingkondenzát – condensate
vrstva přesycených par – supersaturated vapor layer
přívod pracovního média - operation media inlet
chlazení – cooling
pozorovací deska – observation board
odvod zkondenzovaných par – condenzated vapor outlet

Between a moderately heated chamber lid and the intensively heated black observation board (down to -30°C, approximately), a temperature gradient is created. A pump moves isopropyl alcohol in the chamber upper part to electrically heated grooves. In the grooves, the isopropyl alcohol evaporates, with its vapors diffusing downwards. At the height of 1 - 20 mm above the observation board, a layer of supersaturated vapors is created, where visible condensation traces are created, after a pass of a charged particle. 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 Price for „development of methods making tracks of electrically charged particles visible by condensed vapors.“

Ch. T. Wilson was born in 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. Since 1895, he studied atmospheric electricity. After a radioactivity discovery, he worked on rain and snow radioactivity, which became the path to his vapor condensation research. Using experiments, Wilson worked out a new method of observation of various kinds of radiation and in 1913, he designed equipment allowing to make visible and photograph tracks of the radiation. In honor 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 tracks of ionized particles and analyze their mass, electrical charge, and particle energy. It has become 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. Those only with a sufficiently long decay period have been preserved into our days. The most important radionuclides from the viewpoint of natural radiation background are ⁴⁰K, the natural uranium (²³⁸U and ²³⁵U), and ²³² Th. Because all the nuclei with the Z proton number exceeding 83 are radioactive, daughter products of uranium and thorium decay gradually produce decay chains ending with a stable element, having Z = 82 (Pb).

Decay chain elements include, in addition, 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 an introduction of thoron into the cloud chamber, we can well observe a part of ²³²Th decay chain.

²²⁰Rn disintegrates according to the following schematic:

In the cloud chamber, we can see a track of an alpha-particle emitted from decay of ²²⁰Rn (decay period of 55 s, approximately), and immediately the second track of alpha, from the decay of daughter nuclei of ²¹⁶Po (decay period of 0.15 s, approximately). This sequence of a pair of alpha disintegration produces, in the cloud chamber, the characteristic "V"-shape tracks. Apart from it, we can observe that statistically, the second track of the alpha-particle is longer than the first one, because the energy of the emitted alpha-particle is higher, in the second decay. Another effect, that we observe, is the gradual reduction in frequency of alpha tracks observed, due to diminishing of ²²⁰Rn initial quantity. Each 55 s, this amount decreases to a half. In 10 decay periods (9 minutes, approximately) the quantity of radionuclides decreases about 1000 times and we do not observe other traces of the decay in the cloud chamber.

Poločas - period
Energie - energy
stabilní - stable

Has the observation in the cloud chamber caught your interest? Come to the information center of NPP Temelin. With pleasure, we shall show you the cloud chamber and if you are interested in physics even more, we shall demonstrate for you the described experiment with thoron.