Flux distribution of the Superphénix start-up core for the validation of neutronic codes

Abstract

The Superphénix reactor remains the largest Sodium-cooled Fast Reactor ever built in the world and its legacy is a unique source of information for SFRs. At the Superphénix start-up, a series of tests (Transversal Irradiation tests) were devoted to the core flux distribution with measurements in several subassembly positions located from the core center to its periphery. On the other hand, the recent development of neutronic codes has improved accuracy and it is worthwhile to try reproducing these tests. The APOLLO3 code for instance can treat complex geometries without substantial approximations. The Superphénix radial and axial flux profiles are assessed for two Transversal irradiation tests, with a reference Monte Carlo code (TRIPOLI-4) and two deterministic codes, the ERANOS code and its successor the APOLLO-3 code. In a first time, a numerical validation between codes is done to observe the deterministic code bias on the fission rate by comparing the ERANOS and APOLLO-3 evaluations to the TRIPOLI-4 model. Good agreement is seen between codes, and discrepancies between ERANOS and APOLLO-3 remain limited. However, the use of APOLLO-3 eliminates any potential fission rate bias due to the possible compensating errors at the assembly step calculation. An additional survey on the fission rate variations between the JEFF 3.1.1 and the JEFF 3.2 with the same code shows that minor differences are found for the Transversal irradiation tests. It can be concluded that current computational tools are relevant for predicting core flux distribution.

Analysis of the Superphenix Start-Up Tests With Apollo-3: From Zero Power Isothermal Conditions to Dynamic Power Transient Analysis

“…Discrepancies for the core temperature distribution are within 4% to 8%, with an overestimation at the center and an underestimation at the core periphery. These discrepancies are in fact larger than those observed in previous analysis for the flux distribution tests in isothermal conditions [9]. Indeed, in Superphénix, anomalies in the thermal-hydraulic measurements were present as indicated in reference [12] relating to the assembly design.…”

“…Previous research concerning the Superphénix consisted in the development and validation of the start-up tests with the TRIPOLI-4 Monte Carlo code [8]. Besides the core flux distribution at isothermal conditions has been assessed with multiple codes using different nuclear data [9]. Currently our objective is to reproduce the core dynamic behavior by analyzing the NRI test.…”

Validation of fast neutron reactors fertile blanket depletion calculations through the analysis of the DOUBLON experiment in Phenix with TRIPOLI-4® and DARWIN3-SFR

“…For subcritical mediums such as the fertile blanket, ERANOS uses a calculation scheme based on many approximations, which can induce biases for obtaining of the 33 energy group cross sections used for the core calculation. On the other hand, a lot of work has been carried out with APOLLO3® in order to improve the calculation schemes for subcritical mediums (Garcia et al, 2019). It seems that the generation of the cross sections for the subcritical mediums is a key point, which needs more calculation and experimental validation.…”