Safety of Storage Containers

Drop test with steel container

Our specialist competence is the safety evaluation of container designs manufactured for interim and final storage of radioactive wastes under the Atomic Energy Act.

One key issue are interim storage containers for heat generating high activity wastes such as spent fuel elements from nuclear power plants and highly radioactive and vitrified wastes from reprocessing. Typical containers of this type are the CASTOR® containers constructed from ductile cast iron.

In addition, containers for interim and final storage of wastes with low or medium activity and with negligible heat generation are also subjected to engineering assessment. These containers are either cuboid or cylindrical in shape and are made from sheet steel, concrete or cast iron, and are usually certified for both long-term intermediate storage and later final disposal in the "Konrad Mine" repository.

The division undertakes scientific investigations in all areas of container safety in order to maintain and develop the necessary specialist competence as well as developing test methods and test standards. The key issues here are long-term stability, in particular of the sealing systems, and numerical simulation of container impact scenarios on solid grounds using the Finite Element Method (FEM).

Sections

• Interim Storage Containers
• Safety Evaluation of Disposal Containers, Decommissioning, Dismantling
• Numerical Container Analysis

Safety evaluation

Instrumented CASTOR® 1:2 reduced scale test cask – prepared for a 0.3 m drop test without impact limiters onto the unyielding IAEA-test target of BAM

Assessing the engineering quality of containers is based on state-of-the-art science and technology. The key requirement is to guarantee the safe containment of radioactive substances, sufficient shielding from the emitted ionizing radiation, maintain subcriticality as well as adequate removal of the generated decay heat. The following detailed aspects are in the forefront:

• Assessment of the mechanical design of containers under normal storage conditions. This includes loads caused by handling e.g. in bolted trunnions and lid-seal-systems.
  
• Assessment of thermal suitability and stability of the materials and components used from minimum to maximum container temperature. Extreme ambient temperatures as well as the maximum heat generated from nuclear decay in the container have to be considered.
  
• Assessment of the effects of incidents, e.g. earthquake or fire or dropping a container from a crane in the storage hall.
  
• Assessment of effects of residual risk events which may have only a very low probability of occurrence. Such as pressure waves by explosions outside the storage area and aircraft crashing onto a container storage hall.
  
• Assessment of long-term suitability of the containers and all of their components, in particular the seals under mechanical, thermal, radiological and other environmental conditions over 40 years of currently expected storage.
  
• Assessment, determination and monitoring of the necessary quality assurance measures for development, production and operation of the containers.

Scientific investigations

Scientific investigations are carried out in order to maintain and develop the specialist competence needed in all fields of engineering assessment. They concentrate on

• development of methods for mechanical and thermal stress analysis of containers and components,
• model development and analysis of the impact of containers on solid foundations using the Finite Element Method (FEM),
• development of static and dynamic fracture-mechanics analysis and evaluation methods,
• investigation of the long-term behaviour of materials and structures e.g. sealing systems,
• determination of safety margins.

Consultation and advice

The division provides advice on all issues of container safety for storing radioactive substances. It advises

• the public,
• Federal and State Ministries,
• other authorities and
• the industry.

Also, the division is represented in national and international committees. It takes part in information exchange in its specialist field and publishes research and development results at national and international conferences as well as in technical journals and other publications.

top