High power proton accelerators allow providing, by spallation reaction, the neutron fluxes necessary in thesynthesis of fissile material, starting from Uranium 238 or Thorium 232. This is the basis of the concept ofsub-critical operation of a reactor, for energy production or nuclear waste transmutation, with the objective ofachieving cleaner, safer and more efficient process than today's technologies allow.Designing, building and operating a proton accelerator in the 500-1000 MeV energy range, CW regime,MW power class still remains a challenge nowadays. There is a limited number of installations at presentachieving beam characteristics in that class, e.g., PSI in Villigen, 590 MeV CW beam from a cyclotron, SNS inOakland, 1 GeV pulsed beam from a linear accelerator, in addition to projects as the ESS in Europe, a 5 MWbeam from a linear accelerator.Furthermore, coupling an accelerator to a sub-critical nuclear reactor is a challenging proposition: some ofthe key issues/requirements are the design of a spallation target to withstand high power densities as well asensure the safety of the installation.These two domains are the grounds of the PhD work: the focus is on the high power ring methods inthe frame of the KURRI FFAG collaboration in Japan: upgrade of the installation towards high intensityis crucial to demonstrate the high beam power capability of FFAG. Thus, modeling of the beam dynamicsand benchmarking of different codes was undertaken to validate the simulation results. Experimental resultsrevealed some major losses that need to be understood and eventually overcome.By developing analytical models that account for the field defects, one identified major sources of imperfectionin the design of scaling FFAG that explain the important tune variations resulting in the crossing of severalbetatron resonances. A new formula is derived to compute the tunes and properties established that characterizethe effect of the field imperfections on the transverse beam dynamics. The results obtained allow to developa correction scheme to minimize the tune variations of the FFAG. This is the cornerstone of a new fixed tunenon-scaling FFAG that represents a potential candidate for high power applications.As part of the developments towards high power at the KURRI FFAG, beam dynamics studies have toaccount for space charge effects. In that framework, models have been installed in the tracking code ZGOUBIto account for the self-interaction of the particles in the accelerator. Application to the FFAG studies is shown.Finally, one focused on the ADSR concept as a candidate to solve the problem of nuclear waste. In orderto establish the accelerator requirements, one compared the performance of ADSR with other conventionalcritical reactors by means of the levelized cost of energy. A general comparison between the different acceleratortechnologies that can satisfy these requirements is finally presented.In summary, the main drawback of the ADSR technology is the high Levelized Cost Of Energy comparedto other advanced reactor concepts that do not employ an accelerator. Nowadays, this is a show-stopper forany industrial application aiming at producing energy (without dealing with the waste problem). Besides, thereactor is not intrinsically safer than critical reactor concepts, given the complexity of managing the targetinterface between the accelerator and the reactor core.

High power proton accelerators allow providing, by spallation reaction, the neutron fluxes necessary in the synthesis of fissile material, starting from Uranium 238 or Thorium 232. This is the basis of the concept of sub-critical operation of a reactor, for energy production or nuclear waste transmutation, with the objective of achieving cleaner, safer and more efficient process than today's technologies allow. Designing, building and operating a proton accelerator in the 500-1000 MeV energy range, CW regime, MW power class still remains a challenge nowadays. There is a limited number of installations at present achieving beam characteristics in that class, e.g., PSI in Villigen, 590 MeV CW beam from a cyclotron, SNS in Oakland, 1 GeV pulsed beam from a linear accelerator, in addition to projects as the ESS in Europe, a 5 MW beam from a linear accelerator. Furthermore, coupling an accelerator to a sub-critical nuclear reactor is a challenging proposition: some of the key issues/requirements are the design of a spallation target to withstand high power densities as well as ensure the safety of the installation. These two domains are the grounds of the PhD work: the focus is on the high power ring methods in the frame of the KURRI FFAG collaboration in Japan: upgrade of the installation towards high intensity is crucial to demonstrate the high beam power capability of FFAG. Thus, modeling of the beam dynamics and benchmarking of different codes was undertaken to validate the simulation results. Experimental results revealed some major losses that need to be understood and eventually overcome. By developing analytical models that account for the field defects, one identified major sources of imperfection in the design of scaling FFAG that explain the important tune variations resulting in the crossing of several betatron resonances. A new formula is derived to compute the tunes and properties established that characterize the effect of the field imperfections on the transverse beam dynamics. The results obtained allow to develop a correction scheme to minimize the tune variations of the FFAG. This is the cornerstone of a new fixed tune non-scaling FFAG that represents a potential candidate for high power applications. As part of the developments towards high power at the KURRI FFAG, beam dynamics studies have to account for space charge effects. In that framework, models have been installed in the tracking code ZGOUBI to account for the self-interaction of the particles in the accelerator. Application to the FFAG studies is shown. Finally, one focused on the ADSR concept as a candidate to solve the problem of nuclear waste. In order to establish the accelerator requirements, one compared the performance of ADSR with other conventional critical reactors by means of the levelized cost of energy. A general comparison between the different accelerator technologies that can satisfy these requirements is finally presented. In summary, the main drawback of the ADSR technology is the high Levelized Cost Of Energy compared to other advanced reactor concepts that do not employ an accelerator. Nowadays, this is a show-stopper for any industrial application aiming at producing energy (without dealing with the waste problem). Besides, the reactor is not intrinsically safer than critical reactor concepts, given the complexity of managing the target interface between the accelerator and the reactor core.

This volume captures the contents of the talks given at the Workshop on Applications of High Intensity Proton Accelerators held at Fermilab Oct 19-21, 2009. This workshop brought together experts from a variety of disciplines to explore new and profound ways proton accelerators can be used in the future. The workshop explored uses of such a proton source for producing intense muon, kaon and neutrino beams as well as using the intense protons for new forms of nuclear reactors that go by the name Accelerator Driven Sub-critical systems that promise to increase our available nuclear fuel supply by orders of magnitude while at the same time solving the nuclear waste problem. Intense proton beams can also be used to produce short-lived nuclear isotopes that are important in the medical industry.

This volume captures the contents of the talks given at the Workshop on Applications of High Intensity Proton Accelerators held at Fermilab Oct 19ndash;21, 2009. This workshop brought together experts from a variety of disciplines to explore new and profound ways proton accelerators can be used in the future. The workshop explored uses of such a proton source for producing intense muon, kaon and neutrino beams as well as using the intense protons for new forms of nuclear reactors that go by the name Accelerator Driven Sub-critical systems that promise to increase our available nuclear fuel supply by orders of magnitude while at the same time solving the nuclear waste problem. Intense proton beams can also be used to produce short-lived nuclear isotopes that are important in the medical industry.

The use of high power particle accelerators in various areas of applied nuclear science is presented with special emphasis on accelerator driven reactor systems (ADS) for transmutation of nuclear waste.

One of the greatest challenges for nuclear energy is how to properly manage the highly radioactive waste generated during irradiation in nuclear reactors. Accelerator Driven Systems (ADSs) may offer new prospects and advantages for the transmutation of such high level nuclear waste. ADS or accelerator driven transmutation of waste (ATW) consists of a high power proton accelerator, a heavy metal spallation target that produces neutrons when bombarded by the high power beam, and a sub-critical core that is neutronically coupled to the spallation target. This publication provides a comprehensive state of the art of the ADS technology by representing the different ADS concepts proposed worldwide in the last 15 years, as well as the related R&D activities and demonstration initiatives carried out at national international level.