Pierre Leconte

Oscillation experiments techniques in CEA MINERVE experimental reactor

The CEA is deeply involved in a research program (Material Testing Reactors, Zero Power Reactors) concerning the nuclear fuel advanced studies (actinides, plutonium), the waste management, the scientific and technical support of running French PWR reactors and EPR reactor, and innovating systems. In this framework, specific neutron integral experiments have been carried out in the critical facilities of the CEA Cadarache, such as MINERVE, EOLE and MASURCA. This paper deals with experiments in the MINERVE pool Zero Power Reactor.

MAESTRO: An ambitious experimental programme for the improvement of nuclear data of structural, detection, moderating and absorbing materials - First results for nat V, 55 Mn, 59 Co and 103 Rh

The MAESTRO experimental programme has been designed to improve the nuclear data uncertainty on a large range of materials used for detection, absorption, moderation and structures in LWRs. Samples of high purity elements have been manufactured with severe constraints to reach a target accuracy of ±2% (1σ) on the measurement. Experiments are carried out in the MINERVE low-power facility between 2011 and 2014. Neutron activation and pile-oscillation techniques are used to provide complementary information on the capture and scattering cross sections through the measurement of isotopic capture rate and global reactivity-worth for each material. Preliminary results were obtained for natV, 55Mn, and 59Co in support to the instrumentation of GEN-III reactors, just like for 103Rh due to its major contribution to the reactivity loss in LWR. They show that the JEFF-3.1.1 evaluations are in close agreement with the experiment, especially for 103Rh where consistent results were obtained from microscopic experiments at GELINA.

Feedback on 239Pu and 240Pu nuclear data and associated covariances through the CERES integral experiments

Benchmark measurements of irradiated and un-irradiated fuel samples were performed in the framework of the CERES collaborative program between AEA (UK Atomic Energy Agency) and CEA (French Atomic Energy Commission). These experiments provide relevant data for the validation of fuel burn-up and criticality-safety calculations for the whole fuel cycle. As part of this program, pile-oscillation measurements were carried out on a range of mixed-oxide samples with plutonium of various mass and isotopic contents, both in the MINERVE and DIMPLE reactors. Four core configurations, two over-thermalized situations and two pressurized water reactor (PWR)-type situations, were constituted with different forward and adjoint flux spectra, emphasizing fission and/or capture contributions. The experiments were analyzed using reference TRIPOLI4 calculations with the JEFF-3.1.1 library, using exact three-dimensional models of the core configurations. In a first step, calculations of each DIMPLE configuration were performed and compared with the experiment, showing very good agreements with a maximum C-E of −230 pcm. In the second step, reactivity worth experiments were analyzed, using recently developed exact-perturbation capabilities in TRIPOLI4. A consistent assimilation of calculation over experiment discrepancies was performed with the CONRAD code, using the integral data assimilation method. Covariance matrix on multigroup neutron cross sections and multiplicities were generated and significant trends were identified, especially on the 239Pu and 240Pu capture cross sections in the thermal energy range (E < 0.1 eV). Further investigations should be required to confirm these conclusions, due to the strong dependence of these trends and of posterior covariances to prior covariances.