The scenario of Federal Minister of Economics Robert Habeck simply sounded: The three remaining nuclear power plants in Germany-Emsland, Isar-2 and Neckarwestheim II-will no longer produce electricity from the end of 2022, as the nuclear law adopted by the former Black and Yellow Federal Government provides. If, on the other hand, there is a current shortage in winter 2023, for example, the four large electricity network operators warn after a stress test, the reactors of the two power plants Isar-2 and Neckarwestheim II will be switched on again if necessary.
"Reserve operation" is what the minister calls the concept, which would keep all options open to him: On the one hand, the Green politician delivers the long-awaited nuclear phase-out at the end of the year, which many in his party and in the environmental movement are looking forward to. On the other hand, he could not be accused of risking a blackout. Should acute supply bottlenecks threaten at the beginning of 2023 due to a lack of nuclear power, a short-term continued operation of the plants could probably be justified even against the uncompromising opponents of nuclear power. And by mid-April at the latest, the fuel elements in the reactor cores of both plants would be exhausted anyway.
Reactors cannot restart with exhausted fuel
But reactor technology and safety requirements are now putting a stop to Habeck's plan for such a reserve operation: according to experts and the Federal Environment Ministry, Isar-2 and Neckarwestheim II could not simply be used for electricity production again in a largely spent state. The reactor cores would have to be refitted – with more powerful fuel elements from reserve tanks.
The announcement of the Federal Environment Ministry about a leak in the Isar-2 nuclear power plant showed on September 19 how strongly the fuel rods in the remaining German nuclear plants are already exhausted. The operator Preussenektra had already informed the Bavarian authorities and the federal government about it last week. Before the end of 2022, no repair was actually necessary, but for a possible continued operation 2023. "In order to be available for a service company beyond December 31, 2022, according to Preussenelekehr, a standstill must take place," said the Federal Environment Ministry. According to the operator, this standstill must be made in October, "since the fuel elements of the reactor core had too low reactivity in November, in order to then raise the facility out of the standstill".
This statement confirmed the warnings of the head of the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) Uwe Stoll, who had first warned in "RiffReporter" and ten days later in the "Süddeutsche Zeitung" about the start-up of reactors with exhausted fuel elements. The GRS is an important authority for reactor safety. It is 46 percent owned by the federal Government and the TÜV, the remaining eight percent are shared by Bavaria and North Rhine-Westphalia. According to Stoll, reactors with severely depleted fuel elements have never been restarted in Germany. The fact that this state of affairs at Isar-2 would now already occur in November was only announced by the announcement of the Federal Environment Ministry on Monday.
Experience is missing
"We simply haven't had such a way of restarting yet, there is no experience with this in Germany," says Stoll. Operational experience is one of the most important things in nuclear technology. If they don't exist, there is a risk.
Unlike coal and gas power plants, core reactors work, in which fuel is continuously refilled and burned. Nuclear power plants are usually only shut down once a year as part of a so -called revision, in which the reactor core receives new fuel elements and then goes back to the network with high performance.
The Isar-2 nuclear power plant near Landshut is operated by the Eon subsidiary PreussenElektra. It went into operation in 1988 and is one of the most powerful reactors in the world. In previous years, it supplied around 12 percent of the electricity consumed in Bavaria. Neckarwestheim Block II, located south of Heilbronn, belongs to the electricity company EnBW and was connected to the grid in 1989. According to the operator, the plant covered almost 17 percent of Baden-Württemberg's electricity consumption in 2021.
If pressure water reactors are raised again under normal conditions, the energy performance of fresh uranium is so large that the nuclear reaction must be slowed down. For this purpose, the freedom neutrons are captured with boric acid.
However, if Isar-2 and Neckarwestheim II are to continue to operate in reserve mode, they would be in a fundamentally different condition than usual after a revision. Their fuel elements are exhausted, and for the restart, the cooling water is best not to contain any braking boric acid at all. For this purpose, the substance would have to be laboriously removed from the cooling water before restarting the reactor. "We don't know how the reactor behaves in this process, whether there are vibrations, for example," says reactor expert Stoll. Another member of the Reactor Safety Commission, who does not want to be named, shares this assessment.
The scenario of a simple reserve operation is off the table
Experts' warnings have now led to the fact that Habeck's scenario of a simple reserve business was taken off the table in the talks between the federal government and operators. "The fact that the two nuclear power plants intended for emergency operation will be driven at the current core at the turn of the year 2022/23 and this core will then be approached at a later date is none of the scenarios that are currently being discussed between the Federal Government and the operators as possible scenario" , a spokesman for the Federal Environment Ministry responsible for reactor security said on request.
The Ministry of the Environment, led by the Green politician Steffi Lemke, is actively working on the plans for a possible deployment of Isar-2 and Neckarwestheim II in winter. "Now it's about creating the conditions for the power plants to be able to go into power operation in an emergency beyond December 31, 2022," said a spokesman for Lemke.
However, with the notification of Preussenelekehr that Isar-2 would have to be temporarily shut down to repair a valve leaf in October if it is to be available for electricity production in 2023, the situation has now changed in principle. Only at Neckarwestheim II is now conceivable that the reactor simply "drives through" beyond the end of the year, as the Federal Environment Ministry calls it. The facility was only in revision in June and the periodic security check that was up to ten years was only a few years ago.
The situation is different with Isar-2. True, according to experts, the valve leak does not pose a safety hazard. Pressure valves in a reactor are subject to quite normal wear and tear and it is continuously measured how much steam escapes through leaky points. Only when a certain threshold is exceeded, the operator must act. Surprisingly, there is apparently little about the process. According to the operator, the plant could easily pass through by the end of the year.
But in order to be able to produce 2023 electricity for a possible supply of supply, it would have to be repaired now. Because in November you couldn't just go up again with exhausted fuel elements. In Isar-2, the situation is explosive on top of that, because the periodic security check has been overdue since 2019 and has only been dispensed with because of the approaching date of exit.
A simple drive-through beyond the end of the year is therefore no longer an option for Isar-2. On the basis of the repair, the federal government must decide now whether it wants the reactor to be upgraded for operation in 2023 and not only in December, as Economy Minister Habeck had wished.
A standstill of the power plant as early as 2022 could be expensive for the federal government. If several weeks are repaired at your behest, the operators cannot sell electricity during this time. If the reserve performance is then not used in 2023, the state would have to pay the failures.
In the case of both reactors, an important technical question of principle must also be clarified: How can it be avoided that the fuel assemblies are too exhausted to be able to restart the reactor safely, whether after repair, for reserve operation or after another interruption of operation? The warnings of GRS boss Stoll that reactors with such leached cores have never been restarted have arrived in Berlin. The German government is now planning that the reactor cores would have to be reassembled for reserve operation.
Fuel elements that would have to be purchased new and would significantly extend the potential term should not be used in this case. Instead, one would fall back on reserve fuel elements, which are already in the reactor core in separate tanks.
Reserve burning elements enable longer electricity production
The use of reserve fuel elements has so far hardly played a role in the public debate about the extension of the service life. Technically, it is possible, because during the annual revisions sometimes fuel elements are taken that have not yet completely burned down. This may be necessary so that there is not too much fresh, fissile uranium in the core and overheating occurs.
While newly purchased fuel elements are stored outside the core in special locations on the power plant, the reserve burning elements are kept in the reactor core in order to be able to put together an ideal-configured core in the context of revisions. Fresh fuel rods are combined with already used fuel rods and are so spatially arranged that the reactor core can deliver optimal performance without overheating. "This optimization (...) would maximize the power yield," says reactor expert and GRS boss Stoll. This means that Neckarwestheim II can only be "well operated well until February to at least the end of March and Isar-2 instead of only until the end of March to the end of March to the end of June.
Federal Minister of Economics Robert Habeck is ultimately in a multiple quota: if he states hard on the nuclear phase -out on December 31, 2022 and if there is a shortage of care, he will be considered the culprit for an angry public - whether this is that the energy bottleneck is caused by the predecessor Desorted energy transition is obvious, objectively justified or not. If, on the other hand, something goes wrong and there is an accident, it is also clear here who has to hold the head.
If the systems in 2023 are actually transferred to the reserve operation and first shut down, there are also two risks: each newly assembled reactor core must be removed and approved by the nuclear authorities before the reactor is restarted. Problems could arise during the inevitable security check. The system then inevitably stays off the net forever, although Habeck also urgently wants it in electricity production.
And even if the examiners give the green light, the minister could be the debate on the part of the Union and FDP, whether it does not make sense in view of the considerable expenses and costs for the conversion of the kernels and the existing electricity bottlenecks, the potential of the systems Use the generation of electricity to be fully extended - so it may be extended by nuclear power until June. Opponents of nuclear power in their own ranks would probably be upgraded by the core as an affront and betrayal of the nuclear phase -out.
The time for the decision is pressing, because in addition to the investment operators, the public, unsettled by high energy prices, also wants clarity about how the government wants to get through the winter. "Safe operation of nuclear power plants requires good planning and preparations down to the last detail," says GRS CEO Uwe Stoll. He warns: "If you do something hoppladihopp in nuclear technology, it's risky.«
© Riffreporterder Text is originally on »riffreporter.de« under the title »Habeck's Zwickmühle: With exhausted fuel elements, reactors cannot be restarted« and was adapted and supplemented.
