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

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.