Integral ($n$,$\gamma$) Cross-sections Measurement of Standard Light Water Reactors Materials

International audienceMAESTRO is an experimental program in support of the French nuclear industry recently carried out in the MINERVE facility. MINERVE is a pool type zero power reactor (ZPR), well known for being equipped with an oscillating device that makes it possible to measure small-sample reactivity with a very high precision (< 0.1 pcm). MAESTRO is devoted to the improvement of neutron cross sections of elements such as neutron absorbers, detection materials and reactor structure materials widely used in Gen-II and-III pressurized water reactors (PWRs). Neutron activation and pile-oscillation techniques are used together 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. Samples of high elemental purity have been manufactured to reach a target accuracy of < 2 % (1 $\sigma$) on the measurement. This paper focuses on neutron activation measurements performed on several absorbing materials. The capture rates of 16 isotopes were studied by gamma spectrometry on their activation products: Eu-151, Eu-153, In-113, In-115, Ag-109, Cs-133, Mo-98, Mo-100, Sn-112, Sn-116, Sn-122, V-51, Zn-64, Zn-68, Zr-94 and Zr-96. Cadmium ratio measurements were also carried out on small dosimeters of gold, silver, cesium and indium. Since gold is generally considered as a reference element, results are constructed as ratios of the capture rates of interest to the gold capture rate. This procedure eliminates possible systematic errors and reduces uncertainties coming from the detector calibration. The complete uncertainty analysis is presented and discussed along with the experimental results