When it comes to the safety of the deep geological repository for radioactive waste, a distinction is sometimes made between operational safety on the one hand and long-term, post-closure safety on the other. Both have the same objective and are sometimes confused with each other – or equated, but there are some differences behind these two unwieldy terms.
Whether providing protection against radioactive substances, accidents, fire or even an aircraft crash or terrorist attack: operational safety covers all aspects of safety while the repository is in operation.
The negative effects from internal and external sources include storms, flooding, earthquakes, accidents that occur during the transport of radioactive waste, construction hazards and health-related risks for the workers.
Nagra must carry out safety analyses for all these risks and demonstrate in technical reports how it can meet the corresponding legal requirements. Only by doing so can the operational safety of the deep geological repository be optimally ensured. Nuclear power plants must provide the same safety demonstrations.
Formally speaking, operational safety begins with the granting of the operating licence. Only then will Nagra be authorised to transport the disposal canisters containing the radioactive waste from the interim storage facility to the repository, where they will be emplaced. However, before Nagra is granted this licence, it must demonstrate operational safety.
Protected at great depth
Nagra must also demonstrate a second type of safety: post-closure safety. The main function of the repository is to ensure the safety of the radioactive waste in the long term. To this end, the repository is to be constructed at a depth of 800 to 900 metres in the Opalinus Clay. The tight clay rock is particularly suitable for enclosing the waste.
Once the backfilled repository is closed, the buildings at the surface will no longer be needed and will be dismantled. From then on, the second type of safety, namely post-closure safety will come to the fore. Whether in the form of an aircraft crash, a conflagration, a flood or even a future ice age glaciation: the great depth of the repository will protect the waste from such dangers.
Radioactive waste must be kept away from humans and the environment for hundreds of thousands of years. During this time period, it will decay to a harmless level. Whether as a result of war or the collapse of state order: at the earth’s surface, safety cannot be ensured for such a long time period, which is why the waste is to be emplaced at great depth.
Geology is far more stable than society. It can ensure the safety of the repository without the need for monitoring or maintenance repairs by humans as we would rely on, for example, for cars. In a nuclear power plant, the focus is slightly different as the focus lies “only” on operational safety. For example, the fuel rods in the reactor must be cooled constantly to prevent a core meltdown. This requires active safety measures.
In other words, humans manage (from Latin: manus, the hand) or handle (the hand again) the waste safely, which corresponds to our everyday understanding of safety. While many hands will still be at work during the construction and operational phases of the repository, humans will gradually fade from the scene. Once the repository has been sealed, the period of passive post-closure safety will begin, and human intervention will no longer be necessary. From this point on, the laws of nature will ensure safety, and humans will no longer even have to lift a finger.
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