Nuclear reactor fuel rods are essential nuclear components from the operational and safety points of view. Recent experience in nuclear industry is to increase fuel discharge bumup as much as possible. This, in turn, raise the question of fuel rod integrity and radioactivity release at extended bumup and especially during operational transients. At this point, cladding may be considered as the most vital and vulnerable component of the fuel road. Cladding behavior normally is deterioted as bumup increases and power history dependency is significant. In this study, steady-state and long term transient behavior of WWER-440 fuel elements is analyzed with FRAPCON-3 computer code. Operational parameters which are related with the overall reactor safety evaluated as a function of fuel bumup. Especially, the effect of power ramp on mechanical parameters and fission gas release analyzed and an assessment is made. Comparison is made for the parameters in cases of relatively fresh fuel and at extended bumup. Hence, the variation of fuel behavior for high bumup fuel is presented.
(Turkish Atomic Energy Authority, 2000-10) Çolak, Üner; 169746; Bölüm Yok
Safety assessment of nuclear reactors is carried out by simulating the events taking place in
nuclear reactors by realistic computer codes. Such codes are developed in a way that each event
is represented by differential equations derived based on physical laws. Nuclear fuel is an
important barrier against radioactive fission gas release. The release of radioactivity to
environment is the main concern and this can be avoided by preserving the integrity of fuel rod.
Therefore, safety analyses should cover an assessment of fuel rod behavior with certain extent.
In this study, common approaches for fuel behavior modeling are discussed. Methods utilized
by widely accepted computer codes are reviewed. Shortcomings of these methods are explained.
Current research topics to improve code reliability and problems encountered in fuel rod
behavior modeling are presented.