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Interim Storage & Transport

Transport - Storage - Surveillance of Radioactive Waste

Safety of Nucleare Waste Management

Safety and security

The protection of people and the environment is the top priority for the storage of high-level radioactive materials at interim storage facilities. Radiation exposure for local residents and staff, in particular, must be kept as low as possible. In addition to the reliability and expertise of the operator and the necessary precautions for the payment of punitive damages, further requirements must be met.

To be granted a licence, evidence must be provided that sufficient measures have been taken against damage that might result from the storage of the nuclear fuels themselves at an interim storage facility (safety), and that sufficient measures have been taken against criminal and terrorist acts (security). If all the aforementioned prerequisites for the granting of a licence are demonstrably met, the Federal Office for the Safety of Nuclear Waste Management (BASE) must grant a licence (so-called bound decision).

Safety

Radiation exposure

What constitutes impermissible radiation exposure is not determined solely by the corresponding exposure limits: The Radiation Protection Act further stipulates that any radiation exposure during the interim storage of nuclear fuels "must be kept as low as possible, even below the limits, taking into account the state of the art in science and technology and considering all circumstances of each individual case". The limits defined in the Radiation Protection Act and the Radiation Protection Ordinance are thus merely maximum limits, not the test standard.

Exposure limits:

  • Employees at the interim storage facility: 20 mSv per year
  • Persons of the normal population: 1 mSv per year; 50 mSv for all accidents that an interim storage facility is tested for.

In this context, the term ‘safety’ refers to the proof that the precautions required according to the state of the art in science and technology have been taken against damage that may arise from the storage of nuclear fuel at an interim storage facility. This concerns radiological safety during normal operation of the interim storage facility, in the event of incidents during operation, and in the event of natural disasters, e.g. earthquakes or floods.

For each interim storage licence and for each substantial modification of a licence, BASE will monitor compliance with the safety requirements according to the state of the art in science and technology (Section 6 para 2 of the Atomic Energy Act). These are specified in particular by the nuclear rules and regulations. They contain numerous specifications such as technical regulations, recognised verification and calculation methods, regulations for safety management, specifications for organisation and quality management systems. The overriding objective is to avoid impermissible radiation exposure inside and outside the interim storage facility.

Audit objectives

To ensure that the overall objective of avoiding unacceptable radiation exposure is met, BASE examines four sub-objectives:

  1. Safe containment of the radioactive substances
  2. Safe compliance with subcriticality
  3. Safe dissipation of the decay heat
  4. Avoidance of unnecessary radiation exposure

The following safety requirements are derived from these sub-objectives:

  • Ionising radiation shielding
  • Design and construction of the facilities in accordance with operational and maintenance requirements
  • safety-oriented organisation and implementation of the operation
  • safe handling and transport of radioactive material
  • Design against incidents
  • Measures to reduce the damage effects of beyond-design-basis events.

The test procedure

Anyone applying for a licence for an interim storage facility pursuant to Section 6 of the Atomic Energy Act must provide BASE with complete proof of the safety of the storage facility. This includes, in particular, an exact description of the storage casks, the storage building, the technical facilities, the planned monitoring measures as well as calculations or experimental investigations for the radiological effects of the operation of the repository and for all events to be tested that may occur during operation.

All evidence must be conservative. This means that the risk is deliberately overestimated rather than assuming realistic or very probable conditions. Damage precautions, i.e. the preventive measures taken by the operator, must correspond to the state of the art in science and technology.

The application documents are reviewed by BASE and by experts appointed by BASE. If questions remain unanswered during this review, or if documents are missing, BASE will request additional evidence or documents from the applicant. Only if all requirements pertaining to the safety of the storage facility are fulfilled will the test procedure for the safety test point end with a positive result.

The casks

High-level radioactive waste is stored in transport and storage casks, which must fulfil the so-called protection goals. Safety at the interim storage facilities is – not exclusively but to a great extent – ensured by the casks, so that the first barrier already offers the greatest possible safety. Specific requirements for their construction are:

  • Solid metal casks made of ductile cast iron or forged steel
  • Monitored double lid sealing system or a welded lid
  • Transportability

The radioactive substances stored in the storage casks emit small quantities of gases. The storage casks must be designed in such a way that neither the solid nor the gaseous radioactive substances can escape under normal circumstances. For the event of incidents at the interim storage facility or, for example, an earthquake, precautions must be taken to ensure that no cask can be damaged to such an extent that it results in inadmissible radiation exposure.

No nuclear chain reaction may occur in the storage casks (compliance with subcriticality). When storing spent fuel elements, this is ensured, among other things, by the arrangement of the fuel elements in the casks, and a specified minimum burn-up of the fuel elements.

The ionising radiation emitted by the radioactive waste must be adequately shielded. The forged steel or cast iron of the casks and special materials in the casks must ensure that the radiation is shielded, and that as little radiation as possible leaves the casks. However, complete shielding is not possible.

The storage facilities

Interim storage facilities are designed as reinforced concrete storage halls, with the exception of the Neckarwestheim site.

The heat generated by the spent nuclear fuel must be dissipated. For this purpose, the interim storage building must have air intake ducts and exhaust openings. The air ducts must be designed in such a way that the heat emitted by the casks is dissipated to the outside. In addition, the casks must be far enough apart to ensure safe heat dissipation by convection, and to keep mutual heating low.

The operator of an interim storage facility must take measures to shield radioactive radiation, so as to keep the radiation exposure of persons inside and outside the interim storage facility as low as possible. Such measures can be, for example, to use shielding building materials or to restrict access to the areas where the casks are located.

Incidents

An incident is an event against which the operator must equip their plant in terms of technology and organisation. For this purpose, they will prepare an incident analysis that also considers very rare events. A distinction is made here between internal and external events.

Internal events include the falling or toppling of loaded casks, the falling of loads onto casks, fires, or staff errors during handling. The interim storage facilities must also be protected against external events such as lightning, floods, earthquakes, fires, and incidents in neighbouring facilities. In the event of an incident, the radiation exposure for the population must not exceed the limit value of 50 mSv.

Beyond the accidents, there are events whose probability of occurrence is classified as very low, so that the operator does not need to provide evidence for any special protective measures (beyond-design-basis events). These can include the accidental crash of a military aircraft or an explosion pressure wave. Nevertheless, BASE will check whether measures have to be taken by the operator that would reduce the radiation exposure in such an event.

Security

In terms of nuclear facilities and installations, ‘security’ is defined as the necessary protection against disruptive actions or other interference by third parties (SEWD). Terrorist acts and criminal acts in particular are also considered as such.

The protection of the population against crime and terrorism is one of the core duties of the state. However, the state can make the individual private operators discharge their duties, too, if they operate facilities that pose a particular danger in the event of criminal or terrorist acts. The protection of the population is thus achieved through the interaction of all protective measures taken by the state and the safety measures taken by the respective private operators. This is why we speak of an "integrated security and security concept".

BASE’s examination within the framework of the licencing procedure includes the part of the measures for which the respective private operator is responsible. As with safety, the yardstick will be the best possible hazard prevention and risk precaution. A licence will only be granted if, based on the safety measures taken, hazards and risks posed by SEWD can be assessed as practically non-existing according to the state of the art in science and technology.

When it comes to protection, probabilities of occurrence cannot be used, because the execution of SEWD is a wilful and intentional decision. Instead of the objectively determined probability of failure, the competent federal and state security authorities will follow a defined procedure to determine which criminal scenarios (including various aspects, such as the expected size of a group of perpetrators or possible armament) are to be expected. Concrete requirements and measures for protection against SEWD are derived from this assessment - which is subject to constant re-evaluation. These are laid down in so-called SEWD guidelines issued by the Federal Ministry for the Environment. These guidelines are subject to secrecy to prevent potential perpetrators from optimising their criminal intentions and actions..

Audit objectives

The required protection against SEWD is given if the following protection goals are met:

  • Prevention of theft of the nuclear fuel to be stored,
  • Preventing a significant release of nuclear fuel at the facility,
  • Prevention of a significant release of nuclear fuel elsewhere following theft

IT security

The protection of interim nuclear fuel storage facilities against SEWD also includes ensuring the IT security of the interim storage facility. The specific requirements for the security of IT systems of an interim storage facility are laid down in a separate SEWD guideline (so-called SEWD IT guideline), considering, in particular, the hazard situation and the state of the art in science and technology.

The respective applicants must prove compliance with the requirements of this guideline within the scope of a licencing procedure by submitting an IT security concept, which will be reviewed by BASE to ensure that it meets the requirements.

Targeted plane crash

Even though, according to an assessment of the Federal Ministry of the Interior, a deliberate airplane crash on a nuclear facility/equipment is outside the realm of probability, it cannot be completely ruled out. In addition to the scenarios for protection against SEWD contained in the SEWD guidelines of the Federal Ministry of the Environment, BASE has therefore included the potential radiological effects of a targeted crash of a wide-bodied aircraft on interim storage facilities for nuclear fuels as a mandatory criterion to be fulfilled in licensing procedures according to Section 6 of the Atomic Energy Act following the events of September 11, 2001.

In this context, BASE will examine whether a deliberately induced aircraft crash on the respective interim storage facility would lead to particularly severe damage for the protected interests of the Atomic Energy Act. In accordance with the "Calculation basis for determining radiation exposure as a result of disruptive measures or other effects of third parties (SEWD) on nuclear facilities and installations", a value of the resulting radiation exposure of 100 mSv is used as a standard of comparison.

The conservative considerations carried out for the respective interim nuclear fuel storage facilities have so far shown that the integrity of all casks would be maintained in the event of such a scenario at the interim storage facilities, and that the maximum radiation exposure for the respective reference person would be significantly lower than the reference value of 100 mSv.

Security-related retrofitting

Once every three years, the safety authorities of the Federal Government and the Länder will assess whether the interim storage facilities are adequately protected against SEWD on the basis of the current state of knowledge. In 2010, the assessment and knowledge of certain attack scenarios in the vicinity of the transport and storage casks changed to such an extent that the security measures had to be optimised. To this end, mainly structural and technical measures at the interim storage facilities were implemented by the operators of the interim storage facilities in addition to the already existing security measures.

The operators of the interim storage facilities will require a licence pursuant to Section 6 of the Atomic Energy Act as well as corresponding building licences for such retrofitting work. BASE is responsible for issuing the nuclear licences for retrofitting the interim storage facilities. BASE has issued retrofitting licences for eleven of the sixteen interim storage facilities (TBL Gorleben, TBL Ahaus, SZL Philippsburg, SZL Gundremmingen, SZL Biblis, SZL Lingen, SZL Unterweser, SZL Krümmel, SZL Grafenrheinfeld, SZL Isar and SZL Neckarwestheim).

The nuclear licensing procedures of the interim storage facilities in Grohnde and Brokdorf have reached an advanced stage. New licensing procedures are pending for the Brunsbüttel and Jülich interim storage facilities, and the respective applicants must prove compliance with the applicable safety requirements.

The application for retrofitting the existing interim storage facility North (ZLN) was withdrawn by the operator in 2015. The operator intends to store the nuclear fuel in a new interim transport cask storage facility to be built at the Lubmin site instead. An application for the construction of this new interim storage facility was submitted in May 2019.

In the case of interim storage facilities for which safety-related retrofitting has not yet been fully implemented, the operators of the interim storage facilities currently have so-called sufficient temporary measures in place in addition to the already existing safety measures to provide the necessary protection against SEWD. These are, in particular, staff and organisational measures, such as the deployment of additional guards.

State of 2022.12.21

© Federal Office for the Safety of Nuclear Waste Management