Paks Nuclear Power Plant
Encyclopedia
The Paks Nuclear Power Plant (Hungarian
: Paksi Atomerőmű), located 5 kilometres (3.1 mi) from Paks
, central Hungary
, is the first and only operating nuclear power station in Hungary. Altogether, its four reactors produce more than 40 percent of the electrical power generated in the country.
is the Soviet designation for a pressurized water reactor
. The number following VVER, in this case 440, represents the power output of the original design. The VVER-440 Model V213, was a product of the first uniform safety requirements
drawn up by the Soviet designers. This model includes added emergency core cooling and auxiliary feedwater
systems as well as upgraded accident localization systems.
Each reactor contains 42 tons of slightly enriched uranium dioxide
fuel. Fuel takes on average three years to be used (or "burned") in the reactors; after this the fuel rods are stored for five years in an adjacent cooling pond
before being removed from the site for permanent disposal.
The power plant is nearly 100% owned by state-owned power wholesaler Magyar Villamos Művek (MVM). A few shares are held by local municipalities, while a voting preference or "golden" share is held by the Hungarian government. The government is planning to partially privatize MVM but has said that due to security concerns, the Paks nuclear power generator will be kept fully state owned.
One brand-new reactor was bought from Poland
after the Żarnowiec Nuclear Power Plant
project was abandoned in its late development stage.
On the 30th of March 2009 the National Assembly of Hungary
gave its principal consent by votes 330 for, 6 against and 10 abstained to the preparation works of the possible new units. On 26th of February 2010 the owner state company MVM Group
decided the expansion with about 2000 billion Hungarian Forint
s price. On the 17th of January 2011 Tamás Fellegi
, the National Developmental Minister of Hungary discussed with Sergey Kiriyenko (Rosatom) and Deputy Finance Minister of Russia
Dmitriy Pankin in Moscow
about Paks Nuclear Power Plant expansion.
In 2000, the Paks Nuclear Power Plant commissioned a feasibility study which concluded that the plant may remain in operation for another 20 years. The study was updated in 2005 with similar conclusions.
In November 2005, Hungary's Parliament passed a resolution with overwhelming bipartisan majority to support the lifetime extension.
The feasibility study concluded that the non-replaceable parts are in sufficient condition to remain in operation for another 20 years while a minority of replaceable parts needed replacement or refurbishment.
The power generator made repeated surveys of public opinion on the lifetime extension and concluded that support for the decision hovered near 70%.
Following the Fukushima I nuclear accidents in March 2011, Hungary's government said it would conduct a stress test on the Paks Nuclear Power Plant to assess safety, but it would not abandon plans for lifetime extension and it would also go ahead with plans for its expansion.
upgrades it was possible to safely increase the output power of the Unit 4 reactor to 500 MWe in 2006, followed by Unit 1 in 2007. With upgrades to the remaining two units the plant's power generation reached 2000 MWe in 2009.
level 3 event ("serious incident") occurred on 10 April 2003 at the Unit 2 reactor. The incident occurred in the fuel rod cleaning system located under 10 metres (32.8 ft) of water in a cleaning tank next to the spent fuel cooling pond, located adjacent to the reactor in the reactor hall. The reactor had been shut down for its annual refueling and maintenance period on 28 March and its fuel elements removed.
The cleaning system had been installed to remove dirt and corrosion from fuel elements and control rods during shutdown, as there had previously been problems with magnetite
corrosion products from the steam generators
being deposited on the fuel elements which affected the flow of coolant. The sixth set of thirty partially spent elements were in the tank having been cleaned, the cleaning having finished at 16:00. At 21:50, radiation alarms mounted on the cleaning system detected a sudden increase in the amount of krypton-85
. The suspicion was that one of the fuel rod assemblies was leaking. At 22:30, the reactor hall was evacuated because of elevated radiation levels both there and in the ventilation stack.
At 02:15 the following morning, the hydraulic lock of the cleaning vessel lid was released, and immediately the dose rate increased significantly (6-12 millisievert
s/hour) around the spent fuel pond and the pool containing the cleaning machine, and the water level dropped for a short time, by about 7 cm (2.8 in). Water samples from the pond showed contamination due to damaged fuel rods. The lid on the cleaning machine was winched up at 04:20, but one of the three lifting cables attached to it broke; and it was not finally removed until 16 April.
The incident was initially given an INES
rating of 2 ("incident"). However a video examination of the damaged fuel elements following the successful removal of the lid caused the rating to be raised to 3 ("serious incident"). This revealed that cladding on the majority of the 30 fuel elements had been broken, with radioactive spent uranium fuel pellets spilling from the elements into the bottom of the cleaning tank. Apart from the release of radioactive material, a concern was that the accumulation of a compact mass of fuel pellets could lead to a criticality accident
, as the pellets were in a tank of neutron moderating
water. Water containing neutron absorbing boric acid
was added into the tank to raise its concentration to 16 g/kg to prevent this. Ammonia
and hydrazine
were also added to the water to help with the removal of radioactive iodine-131
.
An investigation by the Hungarian Atomic Energy Agency concluded that the cause of the incident was inadequate cooling of the fuel elements, which were heated due to the radioactive decay of short-lived fission product
s. These were kept cool by water circulated by a submerged water pump
. However the cooling was inadequate, leading to the damage to some elements through a build-up of steam around them, depriving them of most of their cooling. The investigation proposed that the severe damage probably occurred when the lid was released, causing thermal shock
to cladding because of the sudden entry of cool water into the system, and explosive steam production.
One of the interesting results of the investigation was that the Hungarian Atomic Agency had placed too much trust in the technology and knowledge of the French Framatome Company (now Areva
). The agency did not investigate documentation provided by the company deeply enough, missing a fatal design flaw in the Framatome-designed, produced, and operated cleaning equipment.
The discharge of radioactive gases through the stack continued for several days after the incident, although the Hungarian Atomic Energy Agency determined that the radiation levels adjacent to the plant were only about 10% above normal. However, the reactor remained out of service for over a year, finally resuming commercial electricity production in September 2004.
Hungarian language
Hungarian is a Uralic language, part of the Ugric group. With some 14 million speakers, it is one of the most widely spoken non-Indo-European languages in Europe....
: Paksi Atomerőmű), located 5 kilometres (3.1 mi) from Paks
Paks
Paks is a town in Tolna county, central Hungary, on the banks of the Danube River. Paks is the home of the only Hungarian nuclear power plant, which provides about 40% the country's electricity....
, central Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
, is the first and only operating nuclear power station in Hungary. Altogether, its four reactors produce more than 40 percent of the electrical power generated in the country.
Technical parameters
VVERVVER
The VVER, or WWER, is a series of pressurised water reactors originally developed by the Soviet Union, and now Russia, by OKB Gidropress. Power output ranges from 440 MWe to 1200 MWe with the latest Russian development of the design...
is the Soviet designation for a pressurized water reactor
Pressurized water reactor
Pressurized water reactors constitute a large majority of all western nuclear power plants and are one of three types of light water reactor , the other types being boiling water reactors and supercritical water reactors...
. The number following VVER, in this case 440, represents the power output of the original design. The VVER-440 Model V213, was a product of the first uniform safety requirements
Nuclear safety
Nuclear safety covers the actions taken to prevent nuclear and radiation accidents or to limit their consequences. This covers nuclear power plants as well as all other nuclear facilities, the transportation of nuclear materials, and the use and storage of nuclear materials for medical, power,...
drawn up by the Soviet designers. This model includes added emergency core cooling and auxiliary feedwater
Auxiliary feedwater
Auxiliary feedwater is a backup water supply system found in pressurized water reactor nuclear power plants. This system, sometimes known as Emergency feedwater, can be used during shutdowns, including accident conditions, and sometimes during startup. It works by pumping water to the steam...
systems as well as upgraded accident localization systems.
Each reactor contains 42 tons of slightly enriched uranium dioxide
Uranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
fuel. Fuel takes on average three years to be used (or "burned") in the reactors; after this the fuel rods are stored for five years in an adjacent cooling pond
Spent fuel pool
Spent fuel pools are storage pools for spent fuel from nuclear reactors. They are typically 40 or more feet deep, with the bottom 14 feet equipped with storage racks designed to hold fuel assemblies removed from the reactor. A reactor's pool is specially designed for the reactor in which the...
before being removed from the site for permanent disposal.
The power plant is nearly 100% owned by state-owned power wholesaler Magyar Villamos Művek (MVM). A few shares are held by local municipalities, while a voting preference or "golden" share is held by the Hungarian government. The government is planning to partially privatize MVM but has said that due to security concerns, the Paks nuclear power generator will be kept fully state owned.
One brand-new reactor was bought from Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
after the Żarnowiec Nuclear Power Plant
Zarnowiec Nuclear Power Plant
The Żarnowiec Nuclear Power Plant was supposed to be the first nuclear power plant in Poland. Due to changes in the economical and political situation in Poland after 1989, as well as public protests in the late 1980s and early '90s which escalated in the wake of the Chernobyl disaster, the...
project was abandoned in its late development stage.
| Station | Type | Net capacity | Gross capacity | Construction start | Grid date | Exp. shutdown |
|---|---|---|---|---|---|---|
| PAKS-1 | VVER-440/V213 | 437 MWe MWE MWE may refer to:*Manufacturer's Weight Empty*McDermott Will & Emery*Midwest Express, an airline*Merowe Airport - IATA code*Multiword expressionMWe may refer to:*Megawatt electrical... |
500 MWe | 01-Aug-1974 | 28-Dec-1982 | 2032 |
| PAKS-2 | VVER-440/V213 | 441 MWe | 500 MWe | 01-Aug-1974 | 06-Sept-1984 | 2034 |
| PAKS-3 | VVER-440/V213 | 433 MWe | 500 MWe | 01-Oct-1979 | 28-Sept-1986 | 2036 |
| PAKS-4 | VVER-440/V213 | 444 MWe | 500 MWe | 01-Oct-1979 | 16-Aug-1987 | 2037 |
| PAKS-5 | VVER-1000 | 950 MWe | 1000 MWe | 2014 (planned) | 2020 (planned) | |
| PAKS-6 | VVER-1000 | 950 MWe | 1000 MWe | 2014 (planned) | 2025 (planned | |
On the 30th of March 2009 the National Assembly of Hungary
National Assembly of Hungary
The National Assembly or Diet is the parliament of Hungary. The unicameral body consists of 386 members elected to 4-year terms. Election of members is based on a complex system involving both area and list election; parties must win at least 5% of the popular vote in order to enter list members...
gave its principal consent by votes 330 for, 6 against and 10 abstained to the preparation works of the possible new units. On 26th of February 2010 the owner state company MVM Group
MVM Group
MVM is a Hungarian power company, the largest in the country responsible for the production, distribution and sale of electricity...
decided the expansion with about 2000 billion Hungarian Forint
Hungarian forint
The forint is the currency of Hungary. It is divided into 100 fillér, although fillér coins are no longer in circulation. The introduction of the forint on 1 August 1946 was a crucial step of the post-WWII stabilization of the Hungarian economy, and the currency remained relatively stable until...
s price. On the 17th of January 2011 Tamás Fellegi
Tamás Fellegi
Tamás László Fellegi , Hungarian politician, jurist, political scientist, businessman. Since 2010 he is Minister of National Development in Viktor Orbán's government...
, the National Developmental Minister of Hungary discussed with Sergey Kiriyenko (Rosatom) and Deputy Finance Minister of Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
Dmitriy Pankin in Moscow
Moscow
Moscow is the capital, the most populous city, and the most populous federal subject of Russia. The city is a major political, economic, cultural, scientific, religious, financial, educational, and transportation centre of Russia and the continent...
about Paks Nuclear Power Plant expansion.
Lifetime extension
The original 30-year lifetime of the four blocs will begin to run out in 2012. As Hungary lacks energy resources and relies heavily on the power plant, it has committed to a 20-year lifetime extension.In 2000, the Paks Nuclear Power Plant commissioned a feasibility study which concluded that the plant may remain in operation for another 20 years. The study was updated in 2005 with similar conclusions.
In November 2005, Hungary's Parliament passed a resolution with overwhelming bipartisan majority to support the lifetime extension.
The feasibility study concluded that the non-replaceable parts are in sufficient condition to remain in operation for another 20 years while a minority of replaceable parts needed replacement or refurbishment.
The power generator made repeated surveys of public opinion on the lifetime extension and concluded that support for the decision hovered near 70%.
Following the Fukushima I nuclear accidents in March 2011, Hungary's government said it would conduct a stress test on the Paks Nuclear Power Plant to assess safety, but it would not abandon plans for lifetime extension and it would also go ahead with plans for its expansion.
Power uprating
Thanks to optimizations, modernization and fuelNuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
upgrades it was possible to safely increase the output power of the Unit 4 reactor to 500 MWe in 2006, followed by Unit 1 in 2007. With upgrades to the remaining two units the plant's power generation reached 2000 MWe in 2009.
2003 incident
An INESInternational Nuclear Event Scale
The International Nuclear and Radiological Event Scale was introduced in 1990 by the International Atomic Energy Agency in order to enable prompt communication of safety significance information in case of nuclear accidents....
level 3 event ("serious incident") occurred on 10 April 2003 at the Unit 2 reactor. The incident occurred in the fuel rod cleaning system located under 10 metres (32.8 ft) of water in a cleaning tank next to the spent fuel cooling pond, located adjacent to the reactor in the reactor hall. The reactor had been shut down for its annual refueling and maintenance period on 28 March and its fuel elements removed.
The cleaning system had been installed to remove dirt and corrosion from fuel elements and control rods during shutdown, as there had previously been problems with magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
corrosion products from the steam generators
Steam generator (nuclear power)
Steam generators are heat exchangers used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors between the primary and secondary coolant loops....
being deposited on the fuel elements which affected the flow of coolant. The sixth set of thirty partially spent elements were in the tank having been cleaned, the cleaning having finished at 16:00. At 21:50, radiation alarms mounted on the cleaning system detected a sudden increase in the amount of krypton-85
Krypton-85
Krypton 85 is a radioisotope of krypton.It decays into rubidium-85, with a half-life of 10.756 years and a maximum decay energy of 0.687 MeV.Its most common decay is by beta particle emission with maximum energy of 687...
. The suspicion was that one of the fuel rod assemblies was leaking. At 22:30, the reactor hall was evacuated because of elevated radiation levels both there and in the ventilation stack.
At 02:15 the following morning, the hydraulic lock of the cleaning vessel lid was released, and immediately the dose rate increased significantly (6-12 millisievert
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...
s/hour) around the spent fuel pond and the pool containing the cleaning machine, and the water level dropped for a short time, by about 7 cm (2.8 in). Water samples from the pond showed contamination due to damaged fuel rods. The lid on the cleaning machine was winched up at 04:20, but one of the three lifting cables attached to it broke; and it was not finally removed until 16 April.
The incident was initially given an INES
International Nuclear Event Scale
The International Nuclear and Radiological Event Scale was introduced in 1990 by the International Atomic Energy Agency in order to enable prompt communication of safety significance information in case of nuclear accidents....
rating of 2 ("incident"). However a video examination of the damaged fuel elements following the successful removal of the lid caused the rating to be raised to 3 ("serious incident"). This revealed that cladding on the majority of the 30 fuel elements had been broken, with radioactive spent uranium fuel pellets spilling from the elements into the bottom of the cleaning tank. Apart from the release of radioactive material, a concern was that the accumulation of a compact mass of fuel pellets could lead to a criticality accident
Criticality accident
A criticality accident, sometimes referred to as an excursion or a power excursion, is an accidental increase of nuclear chain reactions in a fissile material, such as enriched uranium or plutonium...
, as the pellets were in a tank of neutron moderating
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
water. Water containing neutron absorbing boric acid
Boric acid
Boric acid, also called hydrogen borate or boracic acid or orthoboric acid or acidum boricum, is a weak acid of boron often used as an antiseptic, insecticide, flame retardant, as a neutron absorber, and as a precursor of other chemical compounds. It exists in the form of colorless crystals or a...
was added into the tank to raise its concentration to 16 g/kg to prevent this. Ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
and hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...
were also added to the water to help with the removal of radioactive iodine-131
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...
.
An investigation by the Hungarian Atomic Energy Agency concluded that the cause of the incident was inadequate cooling of the fuel elements, which were heated due to the radioactive decay of short-lived fission product
Fission product
Nuclear fission products are the atomic fragments left after a large atomic nucleus fissions. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat , gamma rays and neutrinos. The...
s. These were kept cool by water circulated by a submerged water pump
Water Pump
Water Pump is one of the neighbourhoods of Gulberg Town in Karachi, Sindh, Pakistan. It is near main Water Pump that supplies fresh water to the city of Karachi....
. However the cooling was inadequate, leading to the damage to some elements through a build-up of steam around them, depriving them of most of their cooling. The investigation proposed that the severe damage probably occurred when the lid was released, causing thermal shock
Thermal shock
Thermal shock is the name given to cracking as a result of rapid temperature change. Glass and ceramic objects are particularly vulnerable to this form of failure, due to their low toughness, low thermal conductivity, and high thermal expansion coefficients...
to cladding because of the sudden entry of cool water into the system, and explosive steam production.
One of the interesting results of the investigation was that the Hungarian Atomic Agency had placed too much trust in the technology and knowledge of the French Framatome Company (now Areva
Areva
AREVA is a French public multinational industrial conglomerate headquartered in the Tour Areva in Courbevoie, Paris. AREVA is mainly known for nuclear power; it also has interests in other energy projects. It was created on 3 September 2001, by the merger of Framatome , Cogema and...
). The agency did not investigate documentation provided by the company deeply enough, missing a fatal design flaw in the Framatome-designed, produced, and operated cleaning equipment.
The discharge of radioactive gases through the stack continued for several days after the incident, although the Hungarian Atomic Energy Agency determined that the radiation levels adjacent to the plant were only about 10% above normal. However, the reactor remained out of service for over a year, finally resuming commercial electricity production in September 2004.