Highly radioactive nuclear waste: What a super repository looks like

Highly radioactive nuclear waste: What a super repository looks like The search for a location for the storage of highly radioactive waste is ongoing Rock, depth, facility: What criteria does such a repository have to meet? The surface facility also has the function of making the camp visible Info graphic: info text The big question was there from the start

As early as 1957, when the first German nuclear power plant went into operation, the question was: what to do with the radioactive waste? The answer was always postponed There is now an approved repository for low-level and intermediate-level radioactive waste in the Konrad mine in Lower Saxony

But a suitable location for highly radioactive waste has not yet been found The Federal Society for Repository Search (BGE) has been responsible for this since 2016

She has made up her mind not finding just any suitable place, but the best possible one To do this, she is examining the soil all over Germany, and the location should not be known until 2046 at the earliest

That's how long the rubbish lies around in one of the 16 interim storage facilities According to the BGE, a total of 647,000 cubic meters of nuclear waste will be generated, around 5 percent of which will be highly radioactive

The interim storage facilities are usually located in the immediate vicinity of the nuclear power plants so that the transport routes remain short and fewer people are endangered These storage facilities do not offer a long-term solution because nuclear waste remains dangerous for thousands of years

Depending on the type of waste, nuclear waste decomposes at different rates: low- and medium-level radioactive waste takes several tens of thousands of years, high-level radioactive waste several hundred thousand years A common repository is not an option, since there can be interactions between the types of waste

For example, high-level radioactive waste generates heat, while low-level and intermediate-level radioactive waste generates gas If the two types of waste come into contact with each other, this can lead to chemical reactions that endanger the safety of the repository

Other European countries have already found locations for their repository Finland's repository is under construction, the site in Sweden was approved in 2022, and Switzerland wants to build a facility on the German border

Germany is lagging behind, also because the search for a location is linked to a complex selection process In the first step, all areas were excluded in which, due to volcanic activity, previous mining activities or other geological conditions, the construction of a repository is out of the question

The BGE presented the results of this first step in autumn 2020 According to this, 90 so-called sub-areas are geologically suitable for the repository, which covers more than half of the area of ​​Germany

The controversial salt dome in Gorleben is not included In the next step, the number of regions is reduced to a maximum of 4

The most important factor in site selection is the so-called host rock There are basically three materials to consider: clay rock, rock salt and granite, which is called crystalline in technical terms

Clay has the disadvantage that it is sensitive to heat highly radioactive waste emits heat, so storage in clay rock requires much more space than crystalline, because the heat needs to be distributed over a larger area

However, clay rock has the advantage over crystalline that it is more mobile and can therefore withstand tectonic changes longer without cracking Rock salt is good at dissipating heat

However, water seeped into the Asse repository, and the nuclear waste is now to be retrieved from the former salt mine Even if factors such as the depth and size of the repository have not yet been finally determined, the BGE has calculated the first concrete requirements

These include the stability of the host rock, the number of shafts and the width of the tunnels When it comes to questions about the best containers or the requirements for the surface facility, Switzerland and Sweden are a little further along

In our graphic we show a selection of criteria, which the nuclear waste repository of the future must meet based on current knowledge This is how a repository for highly radioactive waste could be set up

Infographic: Info text The surface facility Function The surface facility initially serves as an infrastructure location where building materials and nuclear waste arrive and are shipped underground But the place also fulfills an important task in the long term: it must serve as a marker for posterity

Long-term highly radioactive waste takes several hundred thousand years before it is no longer dangerous That's an incredibly long time in which we could have long since evolved into a new species

Aliens may have settled on Earth So how do you warn subsequent creatures that we have no idea how they will communicate about what, what is under the ground? Ideas A myriad of ways to preserve knowledge have been considered: from cats that glow when they walk over radioactive waste, to secret orders that pass knowledge from generation to generation

In Switzerland, the surface facility is to be converted into a kind of museum All knowledge about the location is stored on different media

The goal: the information must remain findable in the long term There are no such concrete plans for Germany yet

The host rock Material The most important factor in the safe containment of the waste is the rock Basically, granite, clay and salt are suitable because they seal particularly well

None of these rocks is better than the other, all have advantages and disadvantages Stability The rock layer must be wide and high enough to enclose the entire repository

So no radiating particles can escape In addition, the area must be tectonically stable so that no cracks form in the rock

Therefore, only areas come into question in which there have been no significant changes for at least a million years, for example due to volcanic activity or mining Only areas where there has been little or no movement for more than ten million years are considered favorable

The storage of the nuclear waste containers Info graphic: Info text The container requirement The perfect disposal container does not yet exist In autumn 2020, the Ministry of the Environment decreed that highly radioactive nuclear waste must remain recoverable for 500 years

That means: Even in 500 years, future generations must be able to lift the casks out of the repository In order for this to work, the containers must remain sealed over this period of time

Planning Sweden is planning final storage in copper capsules, the durability of which is scientifically disputed Switzerland has not yet found a solution to the container problem either

Shaft limitation The repository of the future should have two entrances It should not be more, so that the host rock is not damaged more than necessary

Separation The mining shaft serves primarily as access for workers and equipment Fresh air also flows into the mine via this shaft

The disposal container transport shaft is reserved for the transport of nuclear waste The strict separation is important in order to keep the mountain working in the event of a leak: inside to enable a safe escape

To ensure that the air on the mining side also remains free of radionuclides in this case, the air supply flows out again via this second shaft The repository Structure The repository is divided into two sections: the infrastructure area and the storage area

In the infrastructure area there are workshops, storage rooms and workplaces for the workers Depending on the rock, storage takes place in tunnels about five meters wide

Storage The containers are brought into the tunnel with the help of excavators or similar vehicles There they are deposited on a bentonite base

In the course of storage, the tunnels are then backfilled with bentonite This clay mixture is intended to stabilize the repository and serve as another barrier for radioactive material

The answer was always postponed There is now an approved repository for low-level and intermediate-level radioactive waste in the Konrad mine in Lower Saxony But a suitable location for highly radioactive waste has not yet been found The Federal Society for Repository Search (BGE) has been responsible for this since 2016 She has made up her mind not finding just any suitable place, but the best possible one To do this, she is examining the soil all over Germany, and the location should not be known until 2046 at the earliest That's how long the rubbish lies around in one of the 16 interim storage facilities According to the BGE, a total of 647,000 cubic meters of nuclear waste will be generated, around 5 percent of which will be highly radioactive The interim storage facilities are usually located in the immediate vicinity of the nuclear power plants so that the transport routes remain short and fewer people are endangered These storage facilities do not offer a long-term solution because nuclear waste remains dangerous for thousands of years Depending on the type of waste, nuclear waste decomposes at different rates: low- and medium-level radioactive waste takes several tens of thousands of years, high-level radioactive waste several hundred thousand years A common repository is not an option, since there can be interactions between the types of waste For example, high-level radioactive waste generates heat, while low-level and intermediate-level radioactive waste generates gas If the two types of waste come into contact with each other, this can lead to chemical reactions that endanger the safety of the repository Other European countries have already found locations for their repository Finland's repository is under construction, the site in Sweden was approved in 2022, and Switzerland wants to build a facility on the German border Germany is lagging behind, also because the search for a location is linked to a complex selection process In the first step, all areas were excluded in which, due to volcanic activity, previous mining activities or other geological conditions, the construction of a repository is out of the question The BGE presented the results of this first step in autumn 2020 According to this, 90 so-called sub-areas are geologically suitable for the repository, which covers more than half of the area of ​​Germany The controversial salt dome in Gorleben is not included In the next step, the number of regions is reduced to a maximum of 4 The most important factor in site selection is the so-called host rock There are basically three materials to consider: clay rock, rock salt and granite, which is called crystalline in technical terms Clay has the disadvantage that it is sensitive to heat Highly radioactive waste emits heat, so storage in clay rock requires much more space than crystalline, because the heat needs to be distributed over a larger area However, clay rock has the advantage over crystalline that it is more mobile and can therefore withstand tectonic changes longer without cracking Rock salt is good at dissipating heat However, water seeped into the Asse repository, and the nuclear waste is now to be retrieved from the former salt mine Even if factors such as the depth and size of the repository have not yet been finally determined, the BGE has calculated the first concrete requirements These include the stability of the host rock, the number of shafts and the width of the tunnels When it comes to questions about the best containers or the requirements for the surface facility, Switzerland and Sweden are a little further along In our graphic we show a selection of criteria, which the nuclear waste repository of the future must meet based on current knowledge This is how a repository for highly radioactive waste could be set up Infographic: Info text The surface facility Function The surface facility initially serves as an infrastructure location where building materials and nuclear waste arrive and are shipped underground But the place also fulfills an important task in the long term: it must serve as a marker for posterity Long-term Highly radioactive waste takes several hundred thousand years before it is no longer dangerous That's an incredibly long time in which we could have long since evolved into a new species Aliens may have settled on Earth So how do you warn subsequent creatures that we have no idea how they will communicate about what, what is under the ground?