Between length measurements and final storage

The Radiation Engineering degree programme from the energy and environmental engineering degree programme went on a field trip! On January 19, we all met at 6:45 a.m. at the library in Zittau to head to Braunschweig together on the HSZG field trip bus. After the drive, which included a few short breaks, we arrived at our first field trip destination around 11:00 a.m.: the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. Our first stop there was the staff cafeteria for lunch. This was followed by an introductory lecture on the history of the PTB—which was founded as the Physikalisch-Technische Reichsanstalt in Berlin—and its mission. The lecture also covered the transition of SI standards to fundamental constants.

Since we were ahead of schedule, we were given an impromptu look at length measurement technology. In an area where cuboids are normally measured with high precision using interferometers, researchers are now attempting—as part of a research project—to measure nearly perfect spheres and determine their uncertainties. The goal of this determination is to use the spheres as reference standards in a 3D coordinate measuring machine. We were amazed by the precision with which length measurements can be performed at the PTB.

This was followed by tours of three specialized laboratories. First, we visited the Schering Building and its high-voltage measurement technology, then moved on to the Geiger Building, where we learned about the unit of radioactive activity, nuclide standards, and the capabilities of radiation measurement technology. We paid particular attention to the liquid scintillation measurement of beta emitters and the total energy measurement of a beta decay in order to determine the energy spectrum more precisely. Unfortunately, we were unable to gain access to the laboratories where nuclide standards are produced and tested, although this would have been of great interest as the place of origin and reference for all standards and sources. Finally, we were given an explanation of how the various atomic clocks at the PTB work—and were shown their operation in the laboratory—clocks that define our time and transmit the time signal to the world via Frankfurt.

After visiting the PTB, we went to the German Youth Hostel in Braunschweig. Everyone moved into their rooms there until they all met up again in the group at around 6 p.m. to explore Braunschweig a little. After a cozy dinner in a rustic restaurant with a wide variety of dishes and topics of conversation, the group returned to the youth hostel, where the evening came to an end.

After breakfast the next morning, we drove to the Federal Company for Final Disposal (BGE) in Remlingen to the information point at the Asse II mine. There, the group learned a lot of interesting facts about the history of the mine as a salt mine, its use as a final repository, in which around 126,000 barrels of radioactive waste were stored, and the current project to prepare the retrieval of the stored materials to an above-ground interim storage facility. The current state of knowledge and work was explained.

After a briefing on how to behave underground, a safety briefing on the use of the self-rescuer and refreshments at lunchtime, we went to the changing rooms to enter the mine. At a speed of 10 m/s, the pit cage then descended to a depth of 490 m in the repository. Once there, a two-hour tour of the mine began. In addition to the ventilation system and the vehicle workshop, there were also caverns to see, which show continuous water ingress. Due to the age of the facility, it is necessary in many places to stabilize the chambers and paths with Sorelbeton, a special salt concrete. This serves to secure the facility until the planned retrieval, which is scheduled to begin in 2033. Exiting the mine is only possible on the hour, so the group reached the surface again shortly after 4 pm. Any further questions that arose were answered by the BGE employee responsible during a short debriefing. The group then returned to Zittau at 16:45.

The conclusion of all excursion participants was positive. The visit to the Asse II mine was undoubtedly the highlight of the excursion; it was not only interesting, but also exciting and impressive. The visit to the PTB was interesting, but not so tangible and somewhat remote for us due to the PTB's basic tasks.