DeCART Depletion Calculation for PMR200 Two-Dimensional Core

This paper is to evaluate the depletion capability of the DeCART code for PMR200 two-dimensional core. DeCART solves the burnup equation by the matrix exponential based on the Krylov Subspace method. The depletion calculation is performed up to 270 EFPD by using total 14 burnup steps. The double heterogeneity effect is resolved by introducing the RPT method. The DeCART solutions by using a 47-G PWR neutron library are compared with the McCARD Monte Carlo solution which uses ENDF/B-VII. DeCART shows about maximum 1200 pcm eigenvalue, about maximum 2.5% block and 6.0% pin power differences near 180 EFPDs. The differences are mainly due to the library and the geometrical model discrepancy. While the reference calculation is performed by imposing the vacuum condition for the vessel outside, DeCART uses a zigzag-type boundary model. The use of the VHTR neutron library that is scheduled to develop reduces the eigenvalue differences. In the computing time, DeCART requires about 2 and half hours for 14 depletion steps. Therefore, it is concluded that the DeCART code produces a reasonable result for the VHTR core depletion calculation within an affordable computing time.