Impact of Erbia in Long Cycle Operation of PWR

In this paper, we design a core suitable for long cycle operation and we perform sensitivity tests of MTC on the content of erbia (Er₂O₃) in fuel rods. The correlations between the erbia content and MTC, peaking factor, critical boron concentration (CBC) and fuel cycle length are analyzed. CASMO-4E/SIMULATE-3, which is Studsvik's reactor core design code system, has been used for these simulations. In this paper, we designed a core suitable for long cycle operation and we conducted sensitivity tests of MTC on the content of erbia in fuel rods. Erbia is used in normal and zoning fuel region. The correlation between the erbia content and MTC, peaking factor and CBC was analyzed. The more the Er₂O₃ enrichment increases, the more the MTC is enhanced. However, although Er enrichment increases, initial CBC and fuel cycle length do not change remarkably. Er presents the right property of reducing MTC without causing a large change to initial CBC and fuel cycle length. In conclusion, using the properties of Er, MTC can be enhanced and the safety margins can be increased for long cycle operation of cores