Comparative thermohydraulic analyses of VVER 1000 active core for two different assembly construction types

28th Symposium of AER on VVER Reactor Physics and Reactor Safety (2018, Olomouc, Czechia)
[5] Reactor dynamics and safety analysis

Authors

Perin Y., Nikonov S.P., Henry R., Pasichnyk I., Velkov K. (GRS)

Abstract

The OECD/NEA Benchmark on NPP Kalinin Unit 3 “Switching-off of one of the four operating main circulation pumps at nominal power” ¹ based on real measurements is at its end phase. The core load consists of 163 assemblies of the type “TBCA”. A new benchmark is starting based on measurements from the NPP Rostov Unit 2 ² “Reactivity compensation with diluted boron by stepwise insertion of control rod cluster into the VVER-1000 core”. The Rostov core also has 163 assemblies but of a new modern type “TBC-2M” which differs in construction in comparison with the “TBCA”.

The goal of the performed study is to determine the thermohydraulic differences between the cores due to the implementation of the new assembly type. This work will help the Benchmarks’ Rostov-2 participants to set up more accurate core thermohydraulic models.

The paper compares results of steady state simulations for the two cores (Kalinin-3 and Rostov-2) with the same assembly wise axial power distributions. Calculations are done with an under-development version of the GRS system code ATHLET, which has sub-channel modeling capabilities. Thus, seven assemblies around a control rod location are calculated at the sub-channel (pin-by-pin) level. To ensure that the observed differences only come from the fuel assembly construction, the same axial power density is used for all cases.

¹ V.A.Tereshonok, S.P.Nikonov, M.P.Lizorkin, K.Velkov, A.Pautz, K.Ivanov, International Benchmark for Coupled Codes and Uncertainty Analysis in Modelling: Switching-off of one of the four operating main circulation pumps at nominal power at NPP KALININ UNIT 3, 18th Symposium of AER on VVER Reactor Physics and Reactor Safety, Hungary, Eger, Oct. 6-10, 2008.
² M. Avramova A. Denisenko, M. Denisova, P. Gordienko, K. Ivanov, S. Nikonov, I. Pasichnyk, B. Shumskiy, R. Sizov, K. Velkov, EGMPEBV Benchmark “Rostov-2”, 27th Symposium of AER on VVER Reactor Physics and Reactor Safety, Germany, Munich, Oct. 17-20, 2017.