Study of transient connected with WWER-1000 cluster drop with subsequent working of automatic power controller

A.Kuchin, I.Ovdiienko, V.Khalimonchuk, SSTC N&RS, Ukraine

20th Symposium of AER on VVER Reactor Physics and Reactor Safety (2010, Hanasaari, Espoo, Finland)
Reactor dynamics and safety analysis


Results of calculation study of transient connected with drop of WWER-1000 cluster of
working group are presented. Transient was considered in the mode of automatic power
control without forming of warning protection signal due to reaching of dropped cluster of
core bottom. Calculations are shown that given transient can cause valuable distortion of
power distribution in axial direction. At that main increase of pin power is occurred in upper
part of the core, whereas power in lower part is almost not changed. The additional increase
of power in the upper part of core makes conditions for initiation of DNB. This effect can be
observed if in initial state axial power distribution is displaced in upper part of core nearby to
rest of supported power clusters of working group. It is necessary to define conservatively
with taking into account assumed working group efficiency ? in which row from extracted
clusters of working group the displacement of axial power in the upper part is possible.
Probability of such displacement and its localization in plane of core must be properly
analyzed. The work was performed in framework of orders BMU SR 2511 and BMU
R0801504 (SR2611). The report describes the opinion and view of the contractor ? SSTC
N&RS – and does not necessarily represent the opinion of the ordering party – BMU-BfS/GRS
and T?V S?D.

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