SENSITIVITY OF HYDRODYNAMIC PARAMETERS’ DISTRIBUTIONS IN VVER-1000 REACTOR PRESURE VESSEL (RPV) WITH RESPECT TO UNCERTAINTY OF THE LOCAL HYDRAULIC RESISTANCE COEFFICIENTS
23rd Symposium of AER on VVER Reactor Physics and Reactor Safety (2013, Štrbské Pleso, Slovakia)
Reactor dynamics and safety analysis
Abstract
The present paper is a continuation of the uncertainty and sensitivity (U&S) study of the
VVER-1000 reactor, already started in [1-2]. It is based on the OECD/NEA coolant transient
Benchmark (K-3) on measured data at Kalinin-3 Nuclear Power Plant (NPP) where a switch
off of one main coolant pump (MCP) at nominal reactor power is analyzed 3. The novelty of
the work consists of taking into consideration of all hydraulic uncertainty parameters used in
the modeling of the reactor pressure vessel (RPV) internals. A detailed parallel channel
ATHET model of the RPV is developed. It consists of 26600 control volumes most of them
connected with junctions for cross flows. The specific geometry of the gap between upper
part of the baffle and upper part of fuel assembly and also a fuel assembly head are taken
explicitly into account. To reach the specified goals the GRS methodology for uncertainty and
sensitivity analysis ?SUSA? is applied. According to it, 500 samples are generated taking into
account 50 hydraulic parameters in the ATHLET RPV model. The ranking of uncertainty
parameters is obtained and analyzed in detail. The influence of the input parameters on the
uncertainties of the assembly-wise mass flow and coolant temperature axial distributions is
shown.
The significance of the paper consists in pushing forward an approach of ?best-estimate
calculations with a validated system code in combination with performing uncertainty and
sensitivity analysis?. The performed work is the first step in the application of the global
uncertainty parameters? study for K-3 benchmark. Parallel to this work studies are launched
on the influence of nuclear data uncertainties and thermal parameters on the final results.