Theoretical Models and Relevant Calculations of Photon Production and Photonuclear Reaction Data

Photon production and photonuclear reaction data, with emphasis on theoretical model aspects aimed at reliable evaluations, represent a challenge in many technological applications, from radiation shielding for different nuclear systems, including accelerators, to devices relevant to nuclear energy applications, particularly the ones concerning the Accelerator Driven Systems for nuclear waste transmutation. In this field of applied science, theoretical calculations complementing the existing experimental data play an essential role in performing valuable nuclear data evaluations, particularly when the measured quantities are discrepant, scarce, or even lacking. In this framework, new improved results of theoretical and evaluation activities carried out at ENEA, Division for Advanced Physics Technologies, are presented especially concerning photonuclear reaction cross sections. Relevant aspects of nuclear structure models are discussed together with a critical analysis of the related computing codes considered in the present ENEA evaluations, aimed at producing specific contributions to the above-mentioned nuclear programs and applications and at cooperating in the framework of the international initiatives and efforts on the inter-comparison of the evaluated data and of the relevant models and codes. An innovative method has been developed and utilized for microscopic and statistical models of nuclear structure, especially referring to algebraic models aimed at complementing the reaction models for the treatment of pre-equilibrium and compound-nucleus processes. The relevant microscopic algebraic model calculations are discussed, as they reasonably approximate the observed structure of photonuclear cross sections due to multi-polarity effects. Accordingly, theoretical calculation methods are presented for Ti and Mo isotopes, as materials relevant to nuclear applications, and significant results are reviewed for Ti natural isotopes and the element in comparison with the experimental data when available from the existing literature.