Abstract
In a boiling water reactor (BWRs), when neutrons collide nuclear fuel, huge energy is generated by nuclear fission in the reactor core, and the heat it produced causes the cooling water to boil, producing steam. That it combines the neutron and thermal effects under high power /low-flow causes the instability resulted from oscillation of power and flow. In Taiwan, there are three different types of BWRs, one is BWR / 4 (Chinshan Nuclear Power Plant), another is BWR / 6 (Kuosheng Nuclear Power Plant) and the other is ABWR (Lungmen Nuclear Power Plant). Therefore, building a localized stability methodology is crucial. LAPUR5.2 methodology is employed in this study to compare the global and regional mode decay rate at the same power / flow points between Chinshan, Kuosheng and Lungmen Nuclear Power Plant. By comparing the parameters that concerns stability of core, we can observe and analyze why different decay rates are generated between different types of BWRs at the same power/flow points. Furthermore, the stability operating boundary of Chinshan and Kuoshen NPP with 0.8 decay ratio also have been built and calculated. According to above analysis, we can figure out which type of BWRs will perform better in stability.