(a) Development of the stochastic neutronics code ANET (Advanced Neutronics with Evolution and Thermal hydraulic feedback) based on the open-source version of the high energy physics code GEANT3.21 of CERN. ANET is capable of inherently simulating GEN II/III reactors and innovative nuclear reactor designs, such as the Accelerator Driven Systems (ADSs, as an option for safe transmutation of minor actinides) and is designed to be coupled with thermal-hydraulic calculations. For particularly the last feature, an important part of the research was devoted to introduce the time dependency into a coupled Monte Carlo neutronics / thermal-hydraulic model while improving the speed and accuracy of the coupling procedure. In the framework of ANET development within LENSER, two PhD dissertations (one European Doctorat delivered by the School of Electrical & Computer Engineering, Aristotle University of Thessaloniki – ECE/AUTh and another jointly delivered by ECE/AUTh and Ecole Polytechnique de Paris – France) and a diploma thesis/practical training were completed, while 20 publications in International Journals and Conference Proceedings were produced.
(b) Different methods were investigated for improving the utilization of a Research Reactor by proceeding in two main directions, the first aiming at the local increase of the thermal neutron flux at selected core positions by creating flux traps and the second aiming at the local increase of the flux of fission-produced fast neutrons, by using neutron screens. The second target was set responding to the necessity of testing materials for the future Generation-IV fast reactors’ environment. Such tests will necessarily be performed in Thermal RRs since only a few Fast RRs are available worldwide. In both cases, upgrading of the RR utilization was sought without raising safety issues. Relevant simulations were made for both cases, in the first by analyzing various configurations of the Greek RR and in the second by tailoring the neutron spectrum in a given irradiation position of the Jules Horowitz Reactor (CEA/CEN-Cadarache, France) using adequate neutron screens. In the framework of this LENSER Action, one PhD and one Diploma thesis were accomplished while 5 publications in International Journals and Conference Proceedings were produced.