More than 30 pressurised water reactors of the Russian or Soviet VVER (water-water-energy reactor) type are currently in operation in Eastern and Central Europe, and several new plants are under construction. Mochovce-3, for example, started commercial operation in Slovakia in October 2023. Not least the war in Ukraine and the fact that the Zaporizhzhya nuclear power plant (NPP) became the theatre of war have shown that technical knowledge about this type of plant is still needed in Germany too, e.g. to be able to assess any risks. Experts at GRS are therefore involved in numerous research projects on VVER reactors, including international ones. 

On 15 April 2023, the last nuclear power plants in Germany will be shut down. This will mark the end of the history of electricity production from nuclear power after more than 60 years: in June 1961, the Kahl experimental nuclear power plant fed electricity generated by nuclear energy into the West German grid for the first time; five years later, the Rheinsberg nuclear power plant was the first commercially used nuclear power plant in the GDR. The six decades of nuclear power use were initially marked by euphoria, then increasingly by scepticism and rejection. This article, however, focuses less on social or political aspects than on (safety) technical aspects.

Steam generator tubes in pressurised water reactors are exposed to high stresses such as high temperatures or large pressure differences. In combination with possible corrosive effects due to deposits in the outer area of the tubes, these stresses can at worst lead to leakages, which in turn could have an influence on operational safety. A team of researchers from GRS and the Materials Testing Institute of the University of Stuttgart has therefore conducted in-depth investigations into such leakages with the support of the Federal Ministry for the Environment and the Federal Ministry of Economic Affairs. The scientists have now developed a flow model with which the leakage rate of the escaping medium can be determined even more precisely than previously possible.

GRS now offers an extended and revised version of its AC² code package which is used worldwide by supervisory authorities, expert organisations and universities as well as research centres to review the safety of nuclear power plants and other nuclear facilities. The updated version allows i. a. the better simulation of technical features of so-called SMRs (Small Modular Reactors). 

"The Internet is on fire" – that was the message in mid-December 2021 when a security loophole in the Java framework log4j became known, making a wide range of cyber-attacks possible. The Federal Office for Information Security then raised a "red" alert, the highest warning level. Quite a number of companies around the world have turned out to be affected. On behalf of the Federal Ministry for the Environment, GRS experts are analysing cyber-attacks and security incidents that may also be relevant for German nuclear facilities and installations in order to protect them accordingly.

GRS experts develop computational code that can be used to simulate muon radiographic images in order to test the suitability of the method for examining storage casks for spent fuel assemblies.

Researchers worldwide are working on small modular reactors (SMR) and microreactors (very small modular reactor, vSMR). Many of these new reactor concepts are being developed for specific applications and have special core geometries. In order to be able to simulate the neutron-physical behaviour of these cores, GRS is developing the simulation code FENNECS (Finite ElemeNt NEutroniCS).

To ensure the safe operation of technical installations such as nuclear power plants (NPPs), it is important to continuously identify and analyse possible risk factors. In addition to technical safety, the so-called human factor, i.e. human influence and contribution, is of crucial importance for the safe operation of installations. Human-organisational aspects are therefore an aspect of safety research that should not be underestimated. In a recent study, GRS scientists have identified organisational factors that can have a negative influence on plant safety. These are specific characteristics that affect the structure of the organisation (organisational structure), the organisation of activities and processes (process organisation), and the corporate culture.
 

The mineral graphite is used in some types of reactors and can be activated by neutron radiation, i.e. converted into radioactive isotopes. In order to select a suitable disposal option, the graphite must be thoroughly examined radiologically. However, many measuring methods are relatively costly and in turn produce new radioactive waste themselves. A team of researchers from GRS and the University of Cologne is therefore developing a method with which reactor graphite can be characterised quickly and reliably.

Since the search for a repository site was restarted, crystalline rock, such as that found in Bavaria or Saxony, has also been considered as a host rock for a repository for high-level radioactive waste. Currently, experts from the GRS Repository Research Centre are working on several research projects to deepen the understanding of fundamental properties of the host rock and to develop concepts for assessing the safety of a repository in crystalline rock – in their own laboratory tests, in cooperation with foreign research partners, and as part of experiments carried out in the Swiss underground laboratory at Grimsel.