The objective of this topic is to assist SSM by reviewing the material provided by TVEL regarding thermal hydraulics and transient analyses for the TVS-K fuel.
TVEL is a new supplier of fuel for Swedish reactors with, from a Swedish perspective, new analyses methodologies and codes. The authority needs assistance in reviewing these for quality control and compliance with Swedish regulations. Assumptions regarding the fuel modelling and assumed uncertainties as well as the used correlations shall be assessed and reviewed as a part of the safety evaluation. The TVS-K fuel documentation shall be reviewed for all operational modes, event classes and accident scenario and the risk for the plant shall be evaluated and assessed. The coolability of the fuel must be ensured for all event classes and accident scenarios.
The safety evaluation should include, but is not limited by, an assessment of the critical heat flux (CHF), criticality and shutdown margin, reactivity induced accident cladding failure and cladding embrittlement. Furthermore, the effects arising from the mixed assembly core in Ringhals 3 shall be evaluated as well as CRUD deposition and coolant activity.