The new water right permit

In July 2018, the Technical University of Munich requested a water right permit for the FRM II and Radiochemistry to allow controlled discharge of slightly radioactive sewage into the Isar. The sewage should be discharged from the current discharge building at the 130.300 kilometer position of the Isar river. The new permit was released on 19 December 2019 and published in the Amtsblatt: Gehobene wasserrechtliche Erlaubnis für die TUM It will be valid until the end of 2039.


Questions and answers regarding the water right permit

The use of the water requires a permit. The two TUM institutes, Research Neutron Source Heinz Maier-Leibnitz (FRM II) and Radiochemistry Munich (RCM), must therefore obtain permission from the competent authorities that monitor the water to use it.

On 22.12.1999, the Munich District Office granted TUM a higher water law permit for this purpose. It regulates, among other things, the conditions under which the two TUM institutes may discharge water into the Isar.

The previous decision was valid until the end of 2019, so in July 2018 the TUM applied for a new higher water law permit to discharge cooling water and low-level radioactive waste water into the Isar via an existing discharge structure at river kilometre 130,300. The new higher water law permit will apply from 2020 for a term of 20 years.


Since the decision to grant permission under water law in 1999, a lot has changed at the Research Neutron Source (FRM II) and Radiochemistry Munich. The Atomic Egg and the cyclotron are no longer in operation and no longer discharge wastewater directly. Technical improvements, such as a new demineralisation system (reverse osmosis principle) at FRM II, have also led to a reduction in the number of waste water discharge points into the Isar. Over the past 20 years, the discharges have always remained well below the approved limit values. 

Well water: The required cooling water and rinsing water is pumped from the well (fresh groundwater) and accounts for the largest share (99.8%) of the discharge quantity into the Isar.


Drain cooling: Here, the flow rate of the cooling water that is fed into the cooling system corresponds to the flow rate from this cooling system. The properties of the fresh well water of the effluent cooling system do not change as the temperature increase is very small (maximum 10 K).

Cooling towers: The tertiary cooling system serves to add the waste heat of 20 MW generated by the operation of the reactor to the ambient air. Therefore there is no heat input into the Isar.

Flooding: After evaporation via the cooling towers natural minerals remain that are filtered during the flooding and then introduced into the Isar.


Control area FRM II & RCM: If a scientist in the control area washes his hands for purely hygienic reasons, it is collected in appropriate containers even though the water is not necessarily radioactive.

Over the past 15 years of operation, the research neutron source has discharged an average of 190,000 cubic metres of water per year. Due to the high quantities of well water (fresh groundwater) and the small quantities of potentially low-level radioactive waste water, there is no danger to humans or nature. This is also confirmed by the extensive and independent expert opinions (see application for water law permit).

The flushing water already accounts for 99.8% of the total discharge volume, while the potentially low-level radioactive waste water of the FRM II together with the RCM only accounts for 0.2% (370 cubic metres).

The water is discharged batchwise and after it has been sampled. Technical and administrative measures prevent the limit values from being exceeded. One litre may have a maximum activity of 4000 Becquerel (RCM: 370 Becquerel). In comparison, a kilogram of artificial fertilizer available at a DIY store, for example, has 6300 Becquerel. Over the past 20 years, FRM II and RCM have always remained well below the maximum approved annual limit values. They only make full use of them in the single-digit percentage range.

Of the approximately 80 naturally occurring radionuclides and the more than 3000 artificially produced radionuclides, as compiled in the current Karlsruhe nuclide map, a fraction may be handled by FRM II and RCM. These approx. 200 radionuclides are grouped according to their radiological relevance (radiation hazard) into groups of radionuclides, so-called nuclide vectors. These selected radionuclides of the nuclide vectors also cover the radionuclides not listed with regard to their radiological significance. Thus a conservative evaluation is achieved.

The nuclide vectors are listed and considered in the application. There is an external, independent expert opinion attached to the application which calculates the risk for a reference person at the point of discharge and a potential annual dose. This person is assumed to spend 1000 hours a year at the discharge point and cultivate vegetables there. The dose also takes into account the existing pollution of the Isar by e.g. sewage treatment plants. The contribution of waste water from FRM II and radiochemistry to the maximum calculated annual dose for this reference person amounts to a maximum of 3.9 percent if the approved annual limit values are fully utilised. The annual dose, which is due to wastewater from the research neutron source and radiochemistry directly at the point of discharge, is approximately as high for an infant as for a flight from Frankfurt to Las Palmas (Gran Canaria) or slightly more than for a double X-ray of teeth.

It is defined exactly what, how, when, where, by whom and with which device has to be measured - according to the self-monitoring regulation. Regular checks are carried out, sometimes in parallel, by samples and analyses from FRM II's own laboratory for industrial chemistry, the Federal Office for Radiation Protection, the State Office for the Environment and accredited laboratories.

The potentially low-level radioactive effluents from the controlled areas are treated with conventional methods (precipitation, filtration, oxygen treatment); in rare cases, the pH value is also adjusted.

A complete controlled release, in compliance with the limit values, is ensured by administrative and technical measures. The final release for the batchwise discharge from the transfer container into the Isar is given in writing by the chemical plant, the radiation protection officer and the plant management - the 6-eyes principle applies here!

As a nuclear plant, the FRM II is also continuously monitored (around the clock) by the Bavarian Nuclear Reactor Remote Monitoring System (KFÜ), which is operated by the LfU. For further environmental monitoring, investigations of water, aerosols, sediment, plants, milk, cereals or fish are carried out regularly. An independent measuring station, within the framework of the Directive on Emission and Immission Monitoring (REI), takes samples from the environment of the research neutron source - via LfU - and tests them for their radioactivity content. All environmental monitoring data are published in IMIS (Integrated Measurement and Information System for Monitoring Radioactivity in the Environment) via BfS.

Media entries

Landkreis Anzeiger Garching, August 17
"Die Isar ist kein Atomklo" - Erörterungstermin zum Forschungsreaktor Garching, July 28
Radioaktives Abwasser in der Isar, July 26
TU verrät: So schädlich ist das radioaktive Abwasser in der Isar wirklich, July 26
Alles im Fluss, Juliy 25
Isar ist nicht das Atomklo der TU, July 25
Kommunen gegen Reaktorbetreiber, July 24
Streit um Reaktorabwasser in der Isar, July 24
TU will weiterhin radioaktives Abwasser in die Isar leiten: Grünen-Politiker kämpfen dagegen, July 24
Alternativen gesucht, July 23
Wird weiter radioaktives Wasser in die Isar geleitet?, July 23
Anhörung: Schwach radioaktives Wasser aus Reaktor in Isar?, July 23
Legal? Illegal? Nicht egal!, July 21
Abwasser oder Atommüll - Journalistik Eichstätt, April 29
Medienwerkstatt 2019 - Schwach radioaktives Abwasser in der Isar - Aber wer weiß davon?, February 11
TU will weiter schwach radioaktives Wasser in Isar leiten

Bayerischer Rundfunk, February 07
1400 Einwendungen gegen radioaktives Abwasser in der Isar, February 07
Vermeidbare Belastung, 5. February 05
"Deutlich unter den Jahresgrenzwerten" - Interview mit Technischem Direktor Dr. Anton Kastenmüller

Bayerischer Rundfunk, January 25
Abendschau - ab Minute 9:00, January 25
Radioaktives Abwasser in die Isar: Diese Einwände hat Freising gegen den TUM-Antrag, January 24
Neufahrn wehrt sich gegen Reaktor-Abwasser

sueddeutsche, January 18
Radioaktives Abwasser spaltet die Räte, January 18
Radioaktives Isar-Wasser: Ismaning probt den Aufstand gegen Garchings Forscher, January 18
Eching äußert massive Bedenken, January 18
Radioaktives Abwasser in die Isar: Hallbergmooser Grüne laufen Sturm im Gemeinderat, January 17
Brennende Fragen, January 17
Ziemlich überfordert, January 17
Ismaning will Abwasser nicht hinnehmen, January 16
Schwach radioaktive Forschungs-Abwässer in der Isar: Stadt Garching stimmt Erlaubnis zu, January 16
Garching ist für kürzere Laufzeit, January 13
Streit um radioaktives Abwasser in der Isar, January 11
MdL Becher kämpft gegen radioaktives Abwasser in der Isar

Passauer Neue Presse, January 08
Toni Schuberl will Einleitung von radioaktivem Abwasser in Isar verhindern, January 04
Radioaktivität in der Isar