As part of SSM’s Initial Review Phase of SKB’s SR-Site safety assessment of the final disposal of spent nuclear fuel at the Forsmark site, Quintessa has been requested by SSM to review SKB’s MARFA code and consider whether the technical arguments and assumptions used for developing the code are sound, appropriate and adequate to support its use in SR-Site. This Technical Note summarises the findings of Quintessa’s review.
The main concern raised in the review is the poor quality of the documentation associated with the MARFA code, in particular the scope and presentation of the verification cases. It is suggested that SSM could carry out a full QA audit of the MARFA development process.
The linkage between the flow (DFN) modelling and the transport modelling in MARFA requires further consideration. The passing of data should be checked. The handling of variability and uncertainty between the DFN codes and MARFA is not clearly explained and would merit deeper review.
MARFA is designed to handle changes in flow rates as sudden events and the biosphere modelling takes a similar view of climate change. In reality both are gradual and there is need to check whether there is a potential for higher doses during transitions.