Schacht Asse II
Encyclopedia
The Asse II pit is a former salt mine
used as a deep geological repository
for radioactive waste
in the mountain range of Asse
in district Wolfenbüttel
in Lower Saxony
, Germany
.
was placed in storage.
The mine is operated by the German government, and was executed by the Helmholtz Zentrum München
. Research was stopped in 1995; between 1995 and 2004 cavinates were filled with salt.
After media reports in 2008 about brine contaminated with radioactive caesium-137
, plutonium
and strontium
politicians accused the operator of not having informed the inspecting authorities. At Sept. 8th, 2008 the responsible ministers of Lower Saxony and the German government concluded to change the operator. The new one, the Bundesamt für Strahlenschutz
(federal office for radiation protection), will close the mine according to atomic law instead of mining law.
effects are taken into account as they naturally occur in salt dome
s. Significant mechanical stress is built up between the surrounding diapir
s and the artificial construction. The capping mass in Asse II moves 15 cm a year which undermines the strength of the construction.
Because of the high number of tunnel constructions and the decades of use, the deformation in Asse II has reached the state that the pressurised salt is losing its stability: "The supporting construction is softening by creep deformation, plasticity effects and local fractures from the ground pressure." The Institut für Gebirgsmechanik (IfG) in Leipzig
which has been monitoring Asse II since 1996 predicted in 2007 that, from the beginning of 2014, an increase in the loss of the load carrying capacity will result in an increased displacement of the capping mass. The shifts may lead to an uncontrollable increase in water inflow and make the continued operation as a dry pit impossible.
In 1979 a report on the stability of the pit building was released by a working group under the leadership of HH Juergens which describes the now imminent scenario of uncontrolled inflow from the capping mass in the southern flank resulting in the subsequent loss of the load carrying capacity. The manager of Asse II in 1979 and his advisers categorised this report as "unscientific" and declared that there were no stability problems .
For the period 1906 to 1988 there were 29 documented water breaches. They were sometimes successfully sealed off, partly dry, sometimes negligible (less than 0.5 m³ per day). For the current operational security, they are meaningless.
Between 1988 and 2008 32 new entry points were recorded. Part of the solution
is explained as coming from the diapir
in the south area. The solution is collected at 658, 725, 750 m and since 2005 at 950 m, the inflow is currently (2008) 11.8 m³/Day. The liquid is tested for radioactivity and if levels are passed pumped into a tank truck and transported to the abandoned K+S AG mines (Bad Salzdetfurth
, Adolfsglück
and Mariaglück
) The brine in Mariaglück was tested again at the end of 2008 with results for caesium-137
and tritium
.
The German mineral- and table water decree (Mineral- und Tafelwasserverordnung, 24.5.2004) is set at 120 milli-Bq
/l
U-233 or U-235 for drinking water.
Asse II is licensed for the storage of intermediate radioactive waste (LILW-LL, Long lived) and low level waste
(LILW-SL, Short lived), defined as waste without significant heat generation. After public speculation about the presence of radioactive high level waste
in the pit all material was once again reviewed in August 2008:
1) 125,787 drums of low level radioactive waste stored from 1967 to 1978 in various chambers at 750 meters depth. The containers are mostly drums with volumes from 100 to 400 liters or concrete vessels. The declared total activity at the time of the respective storage amounted to 1.8·1015 Bq
. Around 50% of the containers came from the nuclear reprocessing
plant of the former Forschungszentrum Karlsruhe, 20% from nuclear power plant
s and 10% from the former Jülich Research Centre
. The containers typically included mixed- and laboratory waste, rubble, scrap, filter residues and combustion residues. Liquids such as evaporator concentrates, sludges, oils, resins and solvents had to be bound as solids. According to some former employees barrels of liquid waste were accepted in the early days of storage.
2) 1293 containers with medium-level radioactive waste stored from 1972 to 1977 in the chamber 8a on 511-meter depth. Only 200-liter roll drums were allowed with waste fixed in concrete or bitumen. The declared total activity at the time of the respective storage amounted to 2.8·1015 Bq. About 97% of the packages (and thus over 90% of the total activity inventory of Asse II) originated from the reprocessing plant in Karlsruhe. A part of the Karlsruhe drums contained waste from the reprocessing plant itself and thus produced fissile
material. With storage limits of 200 grams U-235, 15 g U-233 and 15 g Pu-239 per drum. These limits were not reached, the maximum values were 24 g U-235
, 5.7 g Pu
-239 and less than 1 g U-233
per drum on 511-meter.
The stored radioactivity of 4.6·1015 Bq is not the only measure to evaluate, the largest part of the radiologically most effective and long-lived alpha radiation occurs in the low-level radioactive waste. Therefore, the low level active waste is of particular importance for the long-term security by creating the biggest problems. The medium-active waste contains mostly relatively short-lived radionuclide
s which is of minor importance to the long-term safety.
Salt mine
A salt mine is a mining operation involved in the extraction of rock salt or halite from evaporite deposits.-Occurrence:Areas known for their salt mines include Kilroot near Carrickfergus, Northern Ireland ; Khewra and Warcha in Pakistan; Tuzla in Bosnia; Wieliczka and Bochnia in Poland A salt mine...
used as a deep geological repository
Deep geological repository
A deep geological repository is a nuclear waste repository excavated deep within a stable geologic environment...
for radioactive waste
Radioactive waste
Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
in the mountain range of Asse
Asse (Germany)
The Asse is a small hill range in the district of Wolfenbüttel in southeastern Lower Saxony with a median height of 200 metres ASL; the highest elevation is the Remlinger Herse with a height of 234 m. There are more than 600 different plants found here; the Asse is mostly covered by trees...
in district Wolfenbüttel
Wolfenbüttel (district)
Wolfenbüttel is a district in southeastern Lower Saxony, Germany. Neighboring districts are the district-free City of Braunschweig, the district of Helmstedt, the district of Harz in Saxony-Anhalt, and the districts of Goslar, Hildesheim and Peine...
in Lower Saxony
Lower Saxony
Lower Saxony is a German state situated in north-western Germany and is second in area and fourth in population among the sixteen states of Germany...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
History
Asse II was allegedly used as a research mine since 1965. Between 1967 and 1978 radioactive wasteRadioactive waste
Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
was placed in storage.
The mine is operated by the German government, and was executed by the Helmholtz Zentrum München
Helmholtz Zentrum München
The Helmholtz Zentrum München is a member of the Helmholtz Association of German Research Centres and is responsible for studying environmental health issues. Founded in 1964, it is a joint project of the Federal Ministry of Education and Research and Bavaria's Finance Ministry...
. Research was stopped in 1995; between 1995 and 2004 cavinates were filled with salt.
After media reports in 2008 about brine contaminated with radioactive caesium-137
Caesium-137
Caesium-137 is a radioactive isotope of caesium which is formed as a fission product by nuclear fission.It has a half-life of about 30.17 years, and decays by beta emission to a metastable nuclear isomer of barium-137: barium-137m . Caesium-137 is a radioactive isotope of caesium which is formed...
, plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
and strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
politicians accused the operator of not having informed the inspecting authorities. At Sept. 8th, 2008 the responsible ministers of Lower Saxony and the German government concluded to change the operator. The new one, the Bundesamt für Strahlenschutz
Bundesamt für Strahlenschutz
The Bundesamt für Strahlenschutz is the German Federal Authority for Radiation Protection. The BfS was established in November 1989, the headquarter is located in Salzgitter, with branch offices in Berlin, Bonn, Freiburg, Gorleben, Oberschleißheim and Rendsburg. It has 708 employees and an annual...
(federal office for radiation protection), will close the mine according to atomic law instead of mining law.
Instability of the pit
No columns and struts are used in a salt mine. The extra stress in the remaining salt structure (the pit building) by constructing the chamber is handled in the capping mass. PlasticityPlasticity (physics)
In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the...
effects are taken into account as they naturally occur in salt dome
Salt dome
A salt dome is a type of structural dome formed when a thick bed of evaporite minerals found at depth intrudes vertically into surrounding rock strata, forming a diapir....
s. Significant mechanical stress is built up between the surrounding diapir
Diapir
A diapir is a type of intrusion in which a more mobile and ductily-deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh-Taylor instability-type structures in regions with low tectonic stress...
s and the artificial construction. The capping mass in Asse II moves 15 cm a year which undermines the strength of the construction.
Because of the high number of tunnel constructions and the decades of use, the deformation in Asse II has reached the state that the pressurised salt is losing its stability: "The supporting construction is softening by creep deformation, plasticity effects and local fractures from the ground pressure." The Institut für Gebirgsmechanik (IfG) in Leipzig
Leipzig
Leipzig Leipzig has always been a trade city, situated during the time of the Holy Roman Empire at the intersection of the Via Regia and Via Imperii, two important trade routes. At one time, Leipzig was one of the major European centres of learning and culture in fields such as music and publishing...
which has been monitoring Asse II since 1996 predicted in 2007 that, from the beginning of 2014, an increase in the loss of the load carrying capacity will result in an increased displacement of the capping mass. The shifts may lead to an uncontrollable increase in water inflow and make the continued operation as a dry pit impossible.
In 1979 a report on the stability of the pit building was released by a working group under the leadership of HH Juergens which describes the now imminent scenario of uncontrolled inflow from the capping mass in the southern flank resulting in the subsequent loss of the load carrying capacity. The manager of Asse II in 1979 and his advisers categorised this report as "unscientific" and declared that there were no stability problems .
Water inflow
Water will always flow into a salt mine where the salt barrier in the surrounding structure is breached. This happens when the salt barrier is damaged in the drilling operation or by plasticity deformation of the salt resulting in cracks. Asse II is particularly threatened by water because the salt barrier is in some places only a few meters thick.For the period 1906 to 1988 there were 29 documented water breaches. They were sometimes successfully sealed off, partly dry, sometimes negligible (less than 0.5 m³ per day). For the current operational security, they are meaningless.
Between 1988 and 2008 32 new entry points were recorded. Part of the solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
is explained as coming from the diapir
Diapir
A diapir is a type of intrusion in which a more mobile and ductily-deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh-Taylor instability-type structures in regions with low tectonic stress...
in the south area. The solution is collected at 658, 725, 750 m and since 2005 at 950 m, the inflow is currently (2008) 11.8 m³/Day. The liquid is tested for radioactivity and if levels are passed pumped into a tank truck and transported to the abandoned K+S AG mines (Bad Salzdetfurth
Bad Salzdetfurth
is a town on the banks of the river Lamme in the district of Hildesheim, in Lower Saxony, Germany. It was mentioned in Tom Clancy's bestseller Red Storm Rising.-Geography:...
, Adolfsglück
Lindwedel
Lindwedel is a municipality in the district of Heidekreis, in Lower Saxony, Germany....
and Mariaglück
Höfer, Germany
Höfer is a municipality in the district of Celle, in Lower Saxony, Germany.Höfer has an abandoned mine named Mariaglück, about 910 m deep, from which the sum of 13.2 million tons of common salt and potash salt was mined between 1916 and 1977. As the maximum, in 1943 about 241,000 tons of salt were...
) The brine in Mariaglück was tested again at the end of 2008 with results for caesium-137
Caesium-137
Caesium-137 is a radioactive isotope of caesium which is formed as a fission product by nuclear fission.It has a half-life of about 30.17 years, and decays by beta emission to a metastable nuclear isomer of barium-137: barium-137m . Caesium-137 is a radioactive isotope of caesium which is formed...
and tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
.
The German mineral- and table water decree (Mineral- und Tafelwasserverordnung, 24.5.2004) is set at 120 milli-Bq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
/l
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...
U-233 or U-235 for drinking water.
Inventory
Asse II is licensed for the storage of intermediate radioactive waste (LILW-LL, Long lived) and low level waste
Low level waste
Low-Level Waste is a term used to describe nuclear waste that does not fit into the categorical definitions for high-level waste , spent nuclear fuel , transuranic waste , or certain byproduct materials known as 11e wastes, such as uranium mill tailings...
(LILW-SL, Short lived), defined as waste without significant heat generation. After public speculation about the presence of radioactive high level waste
High level waste
High level waste is a type of nuclear waste created by the reprocessing of spent nuclear fuel. It exists in two main forms:* First and second cycle raffinate and other waste streams created by nuclear reprocessing....
in the pit all material was once again reviewed in August 2008:
1) 125,787 drums of low level radioactive waste stored from 1967 to 1978 in various chambers at 750 meters depth. The containers are mostly drums with volumes from 100 to 400 liters or concrete vessels. The declared total activity at the time of the respective storage amounted to 1.8·1015 Bq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
. Around 50% of the containers came from the nuclear reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
plant of the former Forschungszentrum Karlsruhe, 20% from nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
s and 10% from the former Jülich Research Centre
Jülich Research Centre
Forschungszentrum Jülich GmbH is a member of the Helmholtz Association of German Research Centres and is one of the largest interdisciplinary research centres in Europe...
. The containers typically included mixed- and laboratory waste, rubble, scrap, filter residues and combustion residues. Liquids such as evaporator concentrates, sludges, oils, resins and solvents had to be bound as solids. According to some former employees barrels of liquid waste were accepted in the early days of storage.
2) 1293 containers with medium-level radioactive waste stored from 1972 to 1977 in the chamber 8a on 511-meter depth. Only 200-liter roll drums were allowed with waste fixed in concrete or bitumen. The declared total activity at the time of the respective storage amounted to 2.8·1015 Bq. About 97% of the packages (and thus over 90% of the total activity inventory of Asse II) originated from the reprocessing plant in Karlsruhe. A part of the Karlsruhe drums contained waste from the reprocessing plant itself and thus produced fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...
material. With storage limits of 200 grams U-235, 15 g U-233 and 15 g Pu-239 per drum. These limits were not reached, the maximum values were 24 g U-235
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
, 5.7 g Pu
PU
PU or Pu may refer to:* A computer processing unit, such as central processing unit and graphics processing unit * Guinea-Bissau's NATO country code...
-239 and less than 1 g U-233
Uranium-233
Uranium-233 is a fissile isotope of uranium, bred from Thorium as part of the thorium fuel cycle. It has been used in a few nuclear reactors and has been proposed for much wider use as a nuclear fuel. It has a half-life of 160,000 years....
per drum on 511-meter.
The stored radioactivity of 4.6·1015 Bq is not the only measure to evaluate, the largest part of the radiologically most effective and long-lived alpha radiation occurs in the low-level radioactive waste. Therefore, the low level active waste is of particular importance for the long-term security by creating the biggest problems. The medium-active waste contains mostly relatively short-lived radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
s which is of minor importance to the long-term safety.
See also
- Nuclear decommissioningNuclear decommissioningNuclear decommissioning is the dismantling of a nuclear power plant and decontamination of the site to a state no longer requiring protection from radiation for the general public...
- Repository for radioactive waste MorslebenRepository for radioactive waste MorslebenThe repository for radioactive waste Morsleben is a deep geological repository for radioactive waste in the rock salt mine Bartensleben in Morsleben, district Börde in the federal state Saxony-Anhalt.-History:...
- Salt dome GorlebenSalt dome GorlebenThe salt dome Gorleben is a proposed deep geological repository in a salt dome in Gorleben in the Lüchow-Dannenberg district in the far north-east of Lower Saxony for low-, medium- and high-level radioactive waste.-Site selection:...
- Shaft miningShaft miningShaft mining or shaft sinking refers to the method of excavating a vertical or near-vertical tunnel from the top down, where there is initially no access to the bottom....
- Schacht KonradSchacht KonradThe pit Konrad is a former iron ore mine proposed as a deep geological repository for medium- and low level radioactive waste in the city Salzgitter in the Metropolitan region Hannover-Braunschweig-Göttingen-Wolfsburg in southeast Lower Saxony, Germany, located between Hildesheim and Braunschweig...
- Waste Isolation Pilot PlantWaste Isolation Pilot PlantThe Waste Isolation Pilot Plant, or WIPP, is the world's third deep geological repository licensed to permanently dispose of transuranic radioactive waste for 10,000 years that is left from the research and production of nuclear weapons...