Аннотация:
This paper presents the results of thermal-hydraulic calculations performed as part of the technical condition
and lifetime extension assessment of SUNPP-3 reactor. Based on the recommendations of the IAEA and
the results of previously performed computational analyzes, the main conservative assumptions for the
analysis of the selected computational scenarios were identified. These assumptions, in the form of initial
and boundary conditions, were used in thermal-hydraulic analysis analyzes. When choosing the initial and
boundary conditions for each scenario, were used the results of preliminary variant computational analyzes,
engineering assessment of the initial and boundary conditions influence to the results, as well as experience
in performing similar work. Thermal-hydraulic analyzes were performed using a computer code RELAP5
using a reactor model with a detailed breakdown of the downcomer and engineering code GRS-MIX to
account for stratification in reactor downcomer. The results of analyzes showed that the selected initiating
events lead to an intensive cooling down of the reactor pressure vessel and the internals. For scenarios
leading to asymmetrical cooling, a different configuration of the ECCS was considered. For scenarios
leading to a general cooling down of the coolant, the rupture location was chosen in such a way as to obtain
maximum cooling down when the ECCS pumps operate in non-emergency loops. As a result of performing
thermal-hydraulic analyzes of the initial events were determined boundary conditions for strength analysis
performing. These boundary conditions were distribution of the pressure, the coolant temperature and the
heat transfer coefficients.
