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- Radioactive material (6)
- Transport packages (6)
- Safety assessment (5)
- Leakage rate (4)
- Spent fuel assessment (4)
- Spent fuel (3)
- Ageing (2)
- Finite element methods (2)
- Gas generation (2)
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Organisationseinheit der BAM
The design of a special form radioactive material has to resist a severe transport accident without undue loss or dispersal of radioactive material.
Safety assessment by authorities competent for design approval has to include besides the required test program (impact, percussion, bending and heat test) also the evaluation of the quality management system for design, manufacture, testing, documentation, use, maintenance and inspection.
These quality assurance measures have to assure that every specimen of the approved design is produced in the same verified quality and every specimen must be able to survive the severe mechanical and thermal tests without undue loss or dispersal of radioactive material at any time of its working life.
All important aspects in the design approval procedure by BAM as the competent authority for approvals of special form radioactive material in Germany are summarized in a guideline published in 2014. This paper will give additional explanations to some aspects in safety assessment, e.g.:
the applicability of leak test methods and the need to consider ageing aspects.
The containment systems of transport casks for spent fuel and high radioactive waste usually include bolted lids with metallic or elastomeric seals.
The mechanical and thermal loadings associated with the routine, normal and accident conditions of transport can have a significant effect on the leak tightness of such containment system.
Scaled cask models are often used for providing the required mechanical and thermal tests series. Leak tests have been conducted on those models.
It is also common practice to use scaled component tests to investigate the influence of deformations or displacements of the lids and the seals on the standard leakage rate as well as to study the temperature and time depending alteration of the seals.
In this paper questions of the transferability of scaled test results to the full size design of the containment system will be discussed.
In accordance with the IAEA transport regulations, the design of special form radioactive material (SFRM) shall resist a severe transport accident without undue loss or dispersal of radioactive material. The safety assessment for design approval includes besides the program for physical tests (impact, percussion, bending and heat test) also the evaluation of the management system for design, manufacture, testing, documentation, use, maintenance, and inspection.
SFRM source design plus management system shall ensure, that every specimen of the approved design is able to survive the severe mechanical and thermal tests at any time of its SFRM-working life.
Due to the long-term use of SFRM designs in most cases, the assessment of the source ageing behavior is an important aspect in the approval procedure. Different fields of application imply a wide range of environmental conditions, from clean room atmosphere to highly aggressive industrial conditions. Besides of radioactive content, corrosion is a main factor for possible SFRM design degradation.
Although the IAEA Advisory Material SSG-26 already implies an indication of the need for considering ageing mechanisms, suitable amendments in the regulatory requirements of SSR-6 should be introduced to make the approval procedure more transparent and help to reduce rounds of questions by the authority. A supplementary requirement for considering of ageing mechanisms could be a helpful contribution to an international harmonization of the approval procedure.
This paper will describe major influencing factors to be considered to assess the ageing behavior of a SFRM design and will identify the need for a regulatory specification of a SFRM-working life as basis for the assessment of the SFRM design regarding time-dependent weakening. A proposal for an explicit requirement for consideration of ageing mechanisms in safety assessment of SFRM, which should be considered in the ongoing SSR-6 revision cycle, will be explained.