Original scientific paper
Analysis of Rod Withdrawal at Power (RWAP) Accident using ATHLET Mod 2.2 Cycle A and RELAP5/mod 3.3 Codes
Vesna Benčik
; Faculty of Electrical Engineering and Computing, University of Zagreb Unska 3, 10000 Zagreb, Croatia
Nikola Čavlina
; Faculty of Electrical Engineering and Computing, University of Zagreb Unska 3, 10000 Zagreb, Croatia
Davor Grgić
; Faculty of Electrical Engineering and Computing, University of Zagreb Unska 3, 10000 Zagreb, Croatia
Abstract
The system code ATHLET (Analysis of THermal-hydraulics of Leaks and Transients) is
being developed by the Gesellschaft für Anlagen-und Reaktorsicherheit (GRS) mbH in Garching,
Germany. In the paper, an overview of activities performed at Faculty of Electrical Engineering and
Computing (FER), University of Zagreb, in application of system code ATHLET in transient
analyses for NPP Krško (NEK) is presented. Newly, the NEK input deck for the released ATHLET
version (Mod 2.2 Cycle A) has been developed. For that purpose, the NEK data base that has been
developed and maintained at FER for the last two decades primarily for development of standard
input deck for RELAP5 code was used. The ATHLET model has been validated by analyzing the
Rod Withdrawal At Power (RWAP) accident at nominal power. The results for steady state
calculation as well as RWAP transient were assessed against the analysis performed by
RELAP5/mod 3.3 code. In both ATHLET and RELAP5 calculation, the RWAP accident was
simulated by constant reactivity insertion rate equal to 2.4 pcm/sec. For ATHLET analysis, two
fluid dynamic options were tested for the primary side: a) base case analysis with 5 conservation
equations and mixture level model and b) two-fluid model with separate conservation equations for
liquid and vapour phases for all the volumes except for the pressurizer where 5 equations+mixture
level model was retained. The Steam Generators (SGs) were built using basic ATHLET elements
together with the dedicated separator model. For RELAP5/mod 3.3 analysis, a standard option with
thermal and mechanical non-equilibrium (6 equations) was used. The results of the steady state
calculation for the ATHLET model have shown a very good agreement with RELAP5 calculation.
In the transient analysis very small differences for the main physical parameters between ATHLET
and RELAP5 as well as between the two ATHLET models were obtained.
Keywords
Hrčak ID:
199042
URI
Publication date:
31.7.2017.
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