Pin Power Calculation Scheme for Reactor Pressure Vessel Fast Neutron Fluence Estimation

Abstract

The estimation of the neutron fluence at the Reactor Pressure Vessel (RPV) is classically carried out by a two-step approach. The first step is to estimate the full core neutron source term whether the second step of the calculation consists in the transport of neutrons from the core (source term) to the RPV using the neutron fission distribution determined in the previous step. For this purpose, the neutron fission distribution is to be accurately determined at the fuel pin level for the assemblies on the border of the core. To achieve this goal, two methods are evaluated in this study. The first method considered is a full core 2D Monte Carlo calculation using the MNCP6 code. The second method is based on a deterministic approach using the CASMO5 multi-segment option, allowing a full 2D transport calculation at the pin level with an expected accuracy similar to a stochastic method. The comparison of the two methods shows an overall good agreement with differences within the statistical uncertainty for different cores: homogeneous UOX core, mixed UOX-MOX loading and the effect of the hafnium rods used in the assemblies in the periphery of the core. The modelling limitation and the associated calculational time are discussed for the comparison of the two approaches.

Analysis of ENRESA BWR samples: nuclide inventory and decay heat

“…Table 1 summarized the non-proprietary data for GN592 assembly parameters from reference [12]. The assembly GN592 was irradiated for five consecutive cycles (cycle [16][17][18][19][20] from July 24, 2000, and was discharged on May 28, 2005. One can notice that the fuel temperature is provided at a specific burnup value. It is nevertheless recognized that the fuel temperature can vary up to a few hundred degrees as a function of the segment burnup and power [14].…”

“…The goal of this, so-called "MxN", simulation (or multi-segment option) is to compute the sample exposure by performing burnup calculations for an entire, 3 × 3-assembly system. Examples of such approach can be found in reference [15] for the ARIANE BM1 sample, for pin power calculations of a full PWR core [16], and for bowing effects in references [17,18].…”