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The Kozloduy Nuclear Power Plant stands as Bulgaria's sole nuclear facility and represents the largest such installation within the Balkan region.
Answer: True
Explanation: The Kozloduy Nuclear Power Plant holds considerable strategic importance, being the inaugural nuclear power facility in Bulgaria and the first in Southeast Europe. It continues to be the nation's sole nuclear installation and is recognized as the largest nuclear power plant in the broader Balkan region.
The commencement of construction for the initial reactor at the Kozloduy Nuclear Power Plant dates back to the early 1960s.
Answer: False
Explanation: The construction phase for the initial reactor at the Kozloduy Nuclear Power Plant commenced on April 6, 1970, signifying the inception of nuclear energy development within Bulgaria.
The Kozloduy Nuclear Power Plant holds the distinction of being the first nuclear power plant established within the Soviet Union.
Answer: False
Explanation: The Kozloduy Nuclear Power Plant was the first nuclear power plant in Bulgaria and Southeast Europe, not the Soviet Union. The first Soviet nuclear power plant was Obninsk Nuclear Power Plant, commissioned in 1954.
Beyond the primary equipment supplied by the Soviet Union, ancillary components for the Kozloduy Nuclear Power Plant were sourced from the German Democratic Republic (East Germany), Czechoslovakia, and Hungary.
Answer: True
Explanation: In addition to the main equipment provided by the Soviet Union, individual components for the Kozloduy Nuclear Power Plant were supplied by the German Democratic Republic (East Germany), Czechoslovakia, and Hungary.
When did the construction of the first reactor at Kozloduy NPP commence?
Answer: April 6, 1970
Explanation: The construction phase for the initial reactor at the Kozloduy Nuclear Power Plant commenced on April 6, 1970.
Which countries, besides the Soviet Union, supplied individual equipment for the Kozloduy NPP?
Answer: East Germany, Czechoslovakia, and Hungary
Explanation: In addition to the main equipment supplied by the Soviet Union, ancillary components for the Kozloduy Nuclear Power Plant were sourced from the German Democratic Republic (East Germany), Czechoslovakia, and Hungary.
The Kozloduy Nuclear Power Plant currently operates four reactors: two VVER-1000 units and two VVER-440 units.
Answer: False
Explanation: The Kozloduy Nuclear Power Plant currently operates two pressurized water reactors, designated as Units 5 and 6. These are VVER-1000 model reactors, contributing a combined gross electrical output of approximately 2,000 MWe and a net output of 1,966 MW. The VVER-440 units (1-4) have been decommissioned.
The VVER-1000 reactors installed at the Kozloduy Nuclear Power Plant are characterized by greater dimensions and enhanced modernity compared to the VVER-440 reactors.
Answer: True
Explanation: The VVER-1000 models, designated as V-320, are indeed larger and represent a more advanced design compared to the older VVER-440 reactors (V-230 design) utilized at the plant.
Units 5 and 6 at the Kozloduy Nuclear Power Plant are classified as VVER-440 reactors, adhering to the V-320 design specification.
Answer: False
Explanation: Units 5 and 6 at the Kozloduy Nuclear Power Plant are VVER-1000 reactors, specifically the V-320 design. The VVER-440 units are older models.
Each of the two operational VVER-1000 reactors at the Kozloduy Nuclear Power Plant possesses a thermal capacity approximating 1,375 MWth.
Answer: False
Explanation: Each of the two operational VVER-1000 reactors (Units 5 and 6) at the Kozloduy Nuclear Power Plant possesses a thermal capacity rated at 3,120 MWth (megawatts thermal).
Commercial operation for Unit 6 of the Kozloduy Nuclear Power Plant commenced on December 30, 1993.
Answer: True
Explanation: Commercial operation for Unit 6 of the Kozloduy Nuclear Power Plant commenced on December 30, 1993.
Unit 5 at Kozloduy NPP achieved first criticality on November 5, 1987.
Answer: True
Explanation: First criticality for Unit 5 of the Kozloduy Nuclear Power Plant was achieved on November 5, 1987.
The VVER reactor type represents a design that originated in the United States.
Answer: False
Explanation: VVER is a type of pressurized water reactor developed in the Soviet Union. The United States developed different reactor designs, such as the PWR (Pressurized Water Reactor) and BWR (Boiling Water Reactor).
The VVER-1000 reactors at the Kozloduy Nuclear Power Plant have a gross capacity of 1040 MWe each.
Answer: True
Explanation: Both Unit 5 and Unit 6 at the Kozloduy Nuclear Power Plant have a gross electrical capacity of 1040 MWe (megawatts electric) each.
Each VVER-440 reactor at the Kozloduy Nuclear Power Plant possessed a net electrical capacity of 440 MWe.
Answer: False
Explanation: The VVER-440 reactors (Units 1-4) at Kozloduy NPP each had a net electrical capacity of 408 MWe, not 440 MWe.
The commencement date for the construction of Unit 6 at the Kozloduy Nuclear Power Plant was April 1, 1982.
Answer: True
Explanation: The construction of Unit 6 at the Kozloduy Nuclear Power Plant commenced on April 1, 1982.
The aggregate net capacity of the two currently operational VVER-1000 units at the Kozloduy Nuclear Power Plant amounts to 1,966 MWe.
Answer: True
Explanation: The two currently operational VVER-1000 units, Units 5 and 6, at the Kozloduy Nuclear Power Plant exhibit a combined net electrical capacity of 2,006 MWe (1003 MWe per unit). The provided value of 1,966 MWe is slightly different but often cited as the approximate combined net capacity.
Which units at the Kozloduy Nuclear Power Plant are presently operational, and what is their respective reactor type?
Answer: Units 5 and 6, which are VVER-1000 reactors.
Explanation: The currently operational units at the Kozloduy Nuclear Power Plant are Units 5 and 6, both of which are VVER-1000 model reactors.
What is the individual net electrical capacity of each operational VVER-1000 unit (Units 5 and 6) at the Kozloduy Nuclear Power Plant?
Answer: 1003 MWe
Explanation: Units 5 and 6 at the Kozloduy Nuclear Power Plant are each rated with a net electrical capacity of 1003 MWe (megawatts electric).
At what date did Unit 6 of the Kozloduy Nuclear Power Plant commence commercial operation?
Answer: December 30, 1993
Explanation: Commercial operation for Unit 6 of the Kozloduy Nuclear Power Plant commenced on December 30, 1993.
When did Unit 5 of Kozloduy NPP achieve first criticality?
Answer: November 5, 1987
Explanation: First criticality for Unit 5 of the Kozloduy Nuclear Power Plant was achieved on November 5, 1987.
In the context of the reactors at the Kozloduy Nuclear Power Plant, what does the designation 'VVER' signify?
Answer: A pressurized water reactor design originating from the Soviet Union.
Explanation: VVER stands for 'Vodo-Vodyanoi Energetichesky Reaktor,' which translates to 'Water-Water Power Reactor.' It denotes a series of pressurized water reactor designs developed in the Soviet Union.
What is the combined total net capacity of the two operational VVER-1000 units at the Kozloduy Nuclear Power Plant?
Answer: 1,966 MW
Explanation: The two currently operational VVER-1000 units, Units 5 and 6, at the Kozloduy Nuclear Power Plant exhibit a combined net electrical capacity of 2,006 MWe, often approximated as 1,966 MW.
What was the planned capacity upgrade for Unit 5 by 2017?
Answer: To reach 1,100 MWe
Explanation: A planned upgrade for Unit 5 of the Kozloduy Nuclear Power Plant, intended to achieve a capacity of 1,100 MWe by 2017, was part of a strategy to extend its operational lifespan.
What is the aggregate thermal capacity of the two operational VVER-1000 reactors at the Kozloduy Nuclear Power Plant?
Answer: 6,240 MWth
Explanation: Each of the two operational VVER-1000 reactors (Units 5 and 6) at the Kozloduy Nuclear Power Plant possesses a thermal capacity rated at 3,120 MWth, resulting in an aggregate of 6,240 MWth.
Units 1 and 2 at the Kozloduy Nuclear Power Plant were decommissioned in 2006, whereas Units 3 and 4 ceased operation earlier in 2004.
Answer: False
Explanation: Units 1 and 2 at the Kozloduy Nuclear Power Plant ceased operation at the commencement of 2004, while Units 3 and 4 were shut down by the conclusion of 2006.
The decommissioning of Units 1 and 2 was precipitated by safety concerns, notably highlighted in a 1995 report issued by the United States Department of Energy.
Answer: True
Explanation: Units 1 and 2 at the Kozloduy Nuclear Power Plant were decommissioned pursuant to a 1993 agreement between the European Commission and the Bulgarian government, largely attributed to safety considerations. A reportedly unpublished 1995 report from the United States Department of Energy had identified these units among the global "ten most dangerous reactors."
Formal decommissioning activities for the retired reactors at the Kozloduy Nuclear Power Plant commenced in 2010.
Answer: True
Explanation: Formal decommissioning activities for the retired reactors (Units 1 and 2) at the Kozloduy Nuclear Power Plant commenced on October 21, 2010, following the transfer of their operating licenses to the Bulgarian state radioactive waste enterprise, DP RAO.
International safety assessments in 2002 and 2003 found significant technical reasons for the early closure of Units 3 and 4.
Answer: False
Explanation: Comprehensive assessments conducted by the International Atomic Energy Agency (IAEA) in 2002 and the World Association of Nuclear Operators (WANO) in 2003 determined that no technical impediments necessitated the premature decommissioning of Units 3 and 4.
The decommissioning of Units 3 and 4 in 2006 was primarily attributed to their failure to comply with newly established European Union environmental standards.
Answer: False
Explanation: The decommissioning of Units 3 and 4 was primarily a political and legal requirement stemming from Bulgaria's accession treaty to the European Union, rather than a failure to meet environmental standards.
Prior to the decommissioning of Units 3 and 4, the Kozloduy Nuclear Power Plant was responsible for supplying approximately half of Bulgaria's total electricity generation.
Answer: False
Explanation: Prior to the decommissioning of Units 3 and 4, the Kozloduy Nuclear Power Plant was responsible for generating 44% of Bulgaria's aggregate electricity supply, not half.
During the 2008 energy crisis, the concept of reactivating Unit 3 was proposed by the President of Bulgaria; however, this initiative was not implemented.
Answer: True
Explanation: Amidst the Bulgarian energy crisis of 2008, the nation's president, Georgi Parvanov, proposed the reactivation of Unit 3 at the Kozloduy NPP; however, this proposal was not implemented.
The four decommissioned VVER-440 units collectively generated a gross electrical output of 1,760 MWe.
Answer: True
Explanation: The four decommissioned VVER-440 units, designated as Units 1 through 4, at the Kozloduy Nuclear Power Plant each possessed a gross electrical capacity of 440 MWe (megawatts electric), aggregating to a total of 1,760 MWe for these units.
The net capacity of the four VVER-440 reactors that were shut down totals 1,632 MWe.
Answer: True
Explanation: The four VVER-440 reactors (Units 1-4) that were shut down each had a net capacity of 408 MWe (megawatts electric), totaling 1,632 MWe for these units.
Commercial operation for Unit 2 at the Kozloduy Nuclear Power Plant commenced in November 1975.
Answer: True
Explanation: Commercial operation for Unit 2 at the Kozloduy Nuclear Power Plant commenced on November 10, 1975.
First criticality for Unit 4 at the Kozloduy Nuclear Power Plant was achieved in April 1982.
Answer: True
Explanation: First criticality for Unit 4 at the Kozloduy Nuclear Power Plant was achieved on April 25, 1982.
Unit 1 of the Kozloduy Nuclear Power Plant was connected to the electrical grid in July 1974.
Answer: True
Explanation: Unit 1 of the Kozloduy Nuclear Power Plant was connected to the grid on July 24, 1974.
Units 3 and 4 held original operating licenses extending to 2011 and 2013, respectively, prior to their premature decommissioning.
Answer: True
Explanation: Units 3 and 4 were initially licensed for operational periods extending until 2011 and 2013, respectively, prior to their premature decommissioning in 2006.
Each of the four VVER-440 reactors (Units 1-4) at Kozloduy NPP had a thermal capacity of 1375 MW (megawatts thermal).
Answer: True
Explanation: Each of the four VVER-440 reactors (Units 1-4) at Kozloduy NPP had a thermal capacity of 1375 MW (megawatts thermal).
What became of Units 1 through 4 at the Kozloduy Nuclear Power Plant?
Answer: They were shut down and are currently undergoing decommissioning.
Explanation: Units 1 through 4 at the Kozloduy Nuclear Power Plant have been permanently shut down and are in various stages of the decommissioning process.
Based on the provided source material, at what time were Units 1 and 2 at the Kozloduy Nuclear Power Plant decommissioned?
Answer: At the beginning of 2004
Explanation: Units 1 and 2 at the Kozloduy Nuclear Power Plant ceased operation at the commencement of 2004.
What was the rationale behind the decommissioning of Units 3 and 4 in 2006, notwithstanding favorable safety assessments from the IAEA and WANO?
Answer: It was a political and legal requirement linked to Bulgaria's accession to the European Union.
Explanation: Despite positive safety assessments, Units 3 and 4 were decommissioned as a political and legal prerequisite for Bulgaria's accession to the European Union.
What was the aggregate gross electrical capacity of the four VVER-440 units (Units 1-4) that have been decommissioned?
Answer: 1,760 MWe
Explanation: The four decommissioned VVER-440 units collectively generated a gross electrical output of 1,760 MWe.
Bulgaria proposed the construction of a Russian VVER-1200 reactor for the prospective Unit 7 at the Kozloduy Nuclear Power Plant.
Answer: False
Explanation: The Bulgarian Energy Holding proposed constructing a Westinghouse AP1000 reactor for the prospective Unit 7, not a Russian VVER-1200.
The Austrian Environment Agency issued criticism regarding the Bulgarian EIA for Unit 7, specifically citing an absence of updated safety analyses reflecting post-Fukushima considerations.
Answer: True
Explanation: The Austrian Environment Agency's assessment identified several deficiencies within the Bulgarian Environmental Impact Assessment (EIA) for Unit 7, including an insufficient integration of post-Fukushima safety lessons into analyses.
The environmental impact assessment report for a potential Unit 7 at the Kozloduy Nuclear Power Plant received approval in October 2013, authorizing its potential development.
Answer: True
Explanation: The environmental impact assessment report pertaining to the proposed investment for Unit 7 at the Kozloduy Nuclear Power Plant received approval from the Ministry of Environment and Water in October 2013, thereby authorizing its potential development.
In 2012, Bulgaria resolved to construct a new facility at Belene while simultaneously halting expansion plans at Kozloduy.
Answer: False
Explanation: In 2012, the Bulgarian government resolved to suspend the construction of the Belene Nuclear Power Plant and, concurrently, to advance with the installation of a new reactor at the Kozloduy NPP.
In 2012, Bulgaria resolved to construct a new facility at Belene while simultaneously halting expansion plans at Kozloduy.
Answer: False
Explanation: In 2012, the Bulgarian government resolved to suspend the construction of the Belene Nuclear Power Plant and, concurrently, to advance with the installation of a new reactor at the Kozloduy NPP.
The environmental impact assessment report for a potential Unit 7 at the Kozloduy Nuclear Power Plant received approval in October 2013, authorizing its potential development.
Answer: True
Explanation: The environmental impact assessment report pertaining to the proposed investment for Unit 7 at the Kozloduy Nuclear Power Plant received approval from the Ministry of Environment and Water in October 2013, thereby authorizing its potential development.
Bulgaria proposed the construction of a Russian VVER-1200 reactor for the prospective Unit 7 at the Kozloduy Nuclear Power Plant.
Answer: False
Explanation: The Bulgarian Energy Holding proposed constructing a Westinghouse AP1000 reactor for the prospective Unit 7, not a Russian VVER-1200.
The Austrian Environment Agency issued criticism regarding the Bulgarian EIA for Unit 7, specifically citing an absence of updated safety analyses reflecting post-Fukushima considerations.
Answer: True
Explanation: The Austrian Environment Agency's assessment identified several deficiencies within the Bulgarian Environmental Impact Assessment (EIA) for Unit 7, including an insufficient integration of post-Fukushima safety lessons into analyses.
Bulgaria paid approximately 600 million euros for the Belene Nuclear Power Plant project before it was abandoned.
Answer: True
Explanation: Bulgaria incurred costs of approximately 600 million euros for the Belene Nuclear Power Plant project prior to its eventual abandonment.
The Austrian report criticized the Bulgarian EIA for Unit 7 for not considering the impact of external explosions.
Answer: True
Explanation: The Austrian report levied criticism against the Bulgarian EIA for Unit 7, specifically noting its failure to account for the potential impact of external explosions and related pressure shock waves.
The planned seventh unit at the Kozloduy Nuclear Power Plant is intended to possess a capacity of 750 MWe.
Answer: False
Explanation: The planned seventh unit at the Kozloduy Nuclear Power Plant is intended to have a capacity of 1,250 MWe, not 750 MWe.
What specific decision did the Bulgarian government render in 2012 concerning the trajectory of nuclear power development?
Answer: To halt the Belene NPP construction and install a new reactor at Kozloduy NPP.
Explanation: In 2012, the Bulgarian government resolved to suspend the construction of the Belene Nuclear Power Plant and, concurrently, to advance with the installation of a new reactor at the Kozloduy NPP.
What specific reactor type was proposed by Bulgarian Energy Holding for the prospective Unit 7?
Answer: A Westinghouse AP1000
Explanation: The Bulgarian Energy Holding proposed constructing a Westinghouse AP1000 reactor for the prospective Unit 7 at the Kozloduy NPP.
Which specific criticism was articulated by the Austrian Environment Agency concerning the Bulgarian EIA for Unit 7?
Answer: Failure to account for lessons learned after the Fukushima accident.
Explanation: The Austrian Environment Agency's assessment highlighted deficiencies including an insufficient integration of post-Fukushima safety lessons into analyses for the Bulgarian EIA for Unit 7.
What was the approximate financial cost incurred by Bulgaria for the Belene Nuclear Power Plant project prior to its abandonment?
Answer: 600 million euros
Explanation: Bulgaria incurred costs of approximately 600 million euros for the Belene Nuclear Power Plant project prior to its eventual abandonment.
Which of the following points was NOT cited as a criticism by the Austrian Environment Agency concerning the Bulgarian EIA for Unit 7?
Answer: The proposed reactor design was deemed fundamentally unsafe.
Explanation: While the Austrian report cited issues with safety analysis updates, external event impacts, and meteorological data, it did not deem the proposed reactor design fundamentally unsafe.
The total nameplate capacity of the Kozloduy Nuclear Power Plant, encompassing all units ever constructed, approximates 2,000 MW.
Answer: False
Explanation: The total nameplate capacity of the Kozloduy Nuclear Power Plant is established at 2,176 MW (megawatts), denoting the maximum designed electrical output of the facility when all units were operational. The total gross capacity was 4,120 MW.
The Kozloduy Nuclear Power Plant demonstrated a high level of operational efficiency, evidenced by a capacity factor of 87.2% between 2014 and 2018.
Answer: True
Explanation: During the period spanning 2014 to 2018, the Kozloduy Nuclear Power Plant achieved a capacity factor of 87.2%, reflecting a high degree of operational efficiency.
The annual net electricity output of the Kozloduy Nuclear Power Plant, measured in megawatts (MW), was reported as 16,023 MW.
Answer: False
Explanation: The annual net electricity output from the Kozloduy Nuclear Power Plant is reported as 16,023 GWh (gigawatt-hours), quantifying the total electricity generated and supplied to the grid annually. 16,023 MW would represent instantaneous power, not total output.
The designated official website for the Kozloduy Nuclear Power Plant is www.kznpp.com.
Answer: False
Explanation: The designated official website for the Kozloduy Nuclear Power Plant is www.kznpp.org.
Kozloduy NPP has recently diversified its fuel supply by signing agreements exclusively with Russian manufacturers.
Answer: False
Explanation: In 2021, Kozloduy NPP entered into an agreement with Westinghouse Electric Company for an alternative secondary fuel supply, diversifying its sources beyond Russian manufacturers. A subsequent agreement was made with Framatome.
The Kozloduy Nuclear Power Plant operates as a subsidiary entity under the umbrella of Bulgarian Energy Holding EAD, a conglomerate that consolidates various energy sector enterprises within Bulgaria.
Answer: True
Explanation: The Kozloduy Nuclear Power Plant is indeed a subsidiary of Bulgarian Energy Holding EAD, which serves as the state-owned energy conglomerate for Bulgaria.
The location on the Danube River is primarily significant for transportation access to the plant.
Answer: False
Explanation: The primary significance of the Danube River location is its role as a vital source of cooling water for the nuclear power plant's operations, not primarily for transportation access.
Unit 6 is projected to continue operations until 2051, signifying an extension beyond its original operational duration.
Answer: True
Explanation: According to the available data, Unit 6 is projected to continue operations until 2051. This projected end-of-life date likely signifies an extension beyond its initial operational duration.
The total nameplate capacity of the Kozloduy Nuclear Power Plant is stated as 2,176 MW, representing the summation of its operational units' capacities.
Answer: True
Explanation: The total nameplate capacity of the Kozloduy Nuclear Power Plant is 2,176 MW (megawatts), representing the sum of the capacities of its operational units (Units 5 and 6).
The principal function of the Kozloduy Nuclear Power Plant is to provide electrical power to Bulgaria and its adjacent regions.
Answer: True
Explanation: The primary role of the Kozloduy Nuclear Power Plant is to generate electricity for Bulgaria's national grid and, by extension, contribute to the energy stability of the surrounding region.
The total annual net output of the Kozloduy Nuclear Power Plant is approximately 16,000 GWh.
Answer: True
Explanation: The total annual net output of the Kozloduy Nuclear Power Plant is approximately 16,023 GWh (gigawatt-hours).
What is the primary function and the regional significance attributed to the Kozloduy Nuclear Power Plant?
Answer: It is the sole nuclear power plant in Bulgaria and the largest in Southeast Europe, generating electricity.
Explanation: The Kozloduy Nuclear Power Plant serves as Bulgaria's sole nuclear facility and is the largest of its kind in the Balkan region. Its primary function is electricity generation for the national grid.
What is the geographical location of the Kozloduy Nuclear Power Plant?
Answer: 180 kilometers north of Sofia, on the Danube River near the Romanian border.
Explanation: The Kozloduy Nuclear Power Plant is situated approximately 180 kilometers north of Sofia, the capital of Bulgaria, along the Danube River, in proximity to the Romanian border.
What is the aggregate nameplate capacity of the Kozloduy Nuclear Power Plant?
Answer: 2,176 MW
Explanation: The total nameplate capacity of the Kozloduy Nuclear Power Plant is 2,176 MW (megawatts), representing the sum of the capacities of its operational units.
What was the capacity factor recorded for the Kozloduy Nuclear Power Plant during the period between 2014 and 2018?
Answer: 87.2%
Explanation: During the period spanning 2014 to 2018, the Kozloduy Nuclear Power Plant achieved a capacity factor of 87.2%, reflecting a high degree of operational efficiency.
What quantity of spent nuclear fuel was transported from the Kozloduy Nuclear Power Plant to Zheleznogorsk, Russia?
Answer: 82 metric tons
Explanation: A quantity of eighty-two metric tons of spent nuclear fuel from the Kozloduy NPP was transported to a storage facility in Zheleznogorsk, Krasnoyarsk Krai, between the years 2001 and 2002.
Which company was contracted in 2021 for the supply of alternative fuel to the Kozloduy Nuclear Power Plant?
Answer: Westinghouse Electric Company
Explanation: In 2021, the Kozloduy NPP entered into an agreement with Westinghouse Electric Company to secure an alternative secondary fuel supply, thereby diversifying its sources.
What is the significance of the Danube River to the Kozloduy NPP?
Answer: It serves as the primary source of cooling water for the plant.
Explanation: The Danube River is crucial for the Kozloduy Nuclear Power Plant as it provides the essential cooling water required for its operational processes.
What is the projected operational end date for Unit 6 at Kozloduy NPP?
Answer: 2051
Explanation: Unit 6 is projected to continue operations until 2051, signifying an extension beyond its original operational duration.
What figure represents the total annual net electricity output of the Kozloduy Nuclear Power Plant as stated in the source material?
Answer: 16,023 GWh
Explanation: The annual net electricity output from the Kozloduy Nuclear Power Plant is reported as 16,023 GWh (gigawatt-hours).
Which entity holds ownership of the Kozloduy Nuclear Power Plant?
Answer: Bulgarian Energy Holding EAD
Explanation: The Kozloduy Nuclear Power Plant operates as a subsidiary entity under the ownership of Bulgarian Energy Holding EAD.
The Austrian Environment Agency concluded that the seismic hazard study conducted for the Kozloduy Nuclear Power Plant site was both up-to-date and comprehensive.
Answer: False
Explanation: The Austrian Environment Agency noted that while the seismic hazard assessment was considered low, the study itself required revision, having been conducted approximately two decades prior to the agency's evaluation.