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Planning against design basis accidents
Casus can directly evaluate the dose to the public for postulated design basis accidents. Note that the dose assessment for design basis accidents is typically very conservative – in contrast to the dose assessment during real accidents, which should be realistic.
Conservative source term data are usually obtained from a safety analysis report (e.g. PSAR or FSAR). For example, for a postulated fuel handling accident, the activity of the radioactive substance that are released until the ventilation system is isolated (during about 30 minutes) could be as follows:
This source term is entered into the Source Term form. (If required, the source term data can also be imported from a comma-delimited text file in the CSV format.)
All relevant parameter values are specified in the Parameters form. For example:
- If the assumed release pathway is a stack with a height of 100 m, the height of the release point (on the Release tab) is set to 100 m.
- If the assumed distance from the stack to the site boundary is 200 m, the minimum distance for all exposure pathways (on the Exposure tab) is set to 200 m.
- If the assumed chemical composition of the released iodine nuclides is 50 % elemental iodine and 50 % methyl iodide, this composition is specified on the Chemistry tab.
All other parameter values are left at conservative reference values in accordance with the regulatory guides for the assessment of design basis accidents.
On the Dose Results form, the new dose results are shown immediately.
In this case, the calculated maximum effective dose amounts to 0.064 mSv (for the 1-year-old member of the public in a distance of 200 m). This result is well below the corresponding limit value of 50 mSv that is stipulated in § 49 (since 2018, § 104) of the German Radiation Protection Ordinance.
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