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The power amplification factor PAF of a driven subcritical system is defined as the ratio of the fission power output of the blanket to the power which the driver must deliver to sustain its neutron source intensity. This parameter decisively determines the effectiveness of the whole system independent of its special purpose as energy amplifier or as transmutation facility. The present note derives a refined analytical expression for the PAF which reveals more physical details than the expressions given by other authors. Moreover, the traditionally used forms of the static reactor eigenvalue equation and of its adjoint equation are rewritten for subcritical systems and used in the derivation of the expression for the PAF. The derived formula and the modified eigenvalue equations are discussed.

Progress in particle accelerator technology makes it possible to use a proton accelerator to produce energy and to destroy nuclear waste efficiently. Energy Amplifier (EA) systems consist of a sub-critical fast neutron core driven by a proton accelerator. If well designed, they prevent any possible criticality accidents. It has been proposed to take advantage of this sub-criticality in order to use certain types of fuel with poor neutronic properties (for instance those with very small delayed neutron fractions). In this respect, they are particularly attractive for destroying, through fission, transuranic elements produced by present nuclear reactors. EA's could also transform efficiently and at minimal cost long-lived fission fragments using the concept of Adiabatic Resonance Crossing (ARC), an innovative method tested at CERN with the TARC experiment.

The nuclear data sensitivity in 3D Monte Carlo burnup calculations of minor actinide transmutation in Energy Amplifier Systems is assessed. Ansaldo Nucleare’s 80 MW th Energy Amplifier Demonstration Facility (EADF) design serves as a technical and geometrical platform for the analysis. The accelerator-driven EADF is a fast, subcritical system based on classical MOX-fuel technology and on molten lead–bismuth eutectic cooling. For Monte Carlo simulations, the state-of-the-art computer code package EA-MC, developed by C. Rubbia and his group at CERN, is utilised. The code offers treatment of both high-energy particle interactions and low-energy neutron transport with a sophisticated method based on a full Monte Carlo simulation, together with the option of employing different modern nuclear data libraries. In particular, the impact of nuclear data discrepancies on transmutation properties prediction with increasing exposure is examined. Monte Carlo simulation accelerator-driven systems transmutation burnup fast neutron spectrum minor actinides nuclear waste.

A speculative propulsion concept is presented, based on accelerating a spacecraft by impact of a stream of matter in relative motion with respect to the spacecraft. To accelerate the stream to the needed velocity, the stream mass is contained in a transit craft, launched at low velocity and hence low energy cost, and then sent on a trajectory with near encounters of the planets for gravitational assist. The mass arrives at Earth or wherever the propellant is needed at much higher velocity and kinetic energy, where it is released into an extended stream suitable for propulsion. The stream, moving at a relative velocity in the range of 10 to 30 km/s, should be capable of both high thrust and high specific impulse. Means of limiting the transverse expansion of the stream during release and for the ∼1000 s duration of impact are a critical requirement for practicality of the concept. The scheme could potentially lead to a virtually unlimited energy source. One can imagine using a portion of one stream to launch another, larger payload on a similar trajectory. This creates, in effect, an energy amplifier extracting energy from the orbital motions of the planets. The gain of the energy amplifier is only limited by the capacity to prepare mass in transit craft.

Accelerator Driven Systems (ADS) are an old technological idea: Relativistic proton accelerators deliver their beams onto massive heavy element targets, thus producing abundant neutron fluences. Placing this target into sub-critical nuclear fission assemblies is yielding substantial fission reactions, thus additional fission energy (Rubbia called such a system “Energy Amplifier”). This technology has recently attracted considerable attention due to advances in the construction of powerful accelerators. It allows the safe and cheap production of nuclear energy simultaneously with the destruction (Transmutation) of long lived radioactive waste, in particular plutonium and other minor actinides (neptunium and americium). The principles and the present-state-of-the-art are described, including first experiments to transmute plutonium this way. This technology needs, however, many more years of further “research and development” before large scale ADS's can be constructed. It may be even necessary to investigate the question, if all basic physics phenomena of this technology are already sufficiently well understood.

Progress in particle accelerator technology makes it possible to use a proton accelerator to produce energy and to destroy nuclear waste efficiently. The energy amplifier (EA) proposed by Carlo Rubbia and his group is a subcritical fast neutron system driven by a proton accelerator. It is particularly attractive for destroying, through fission, transuranic elements produced by presently operating nuclear reactors. The EA could also efficiently and at minimal cost transform long-lived fission fragments using the concept of adiabatic resonance crossing (ARC), recently tested at CERN with the TARC experiment. The ARC concept can be extended to several other domains of application (production of radioactive isotopes for medicine and industry, neutron research applications, etc.).

SummaryExperimental studies on the transmutation of some long-lived radioactive waste nuclei, such as129I,237Np, and239Pu, as well as on natural uranium and lanthanum were carried out at the Synchrophastron of the Laboratory for High Energies at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The radioactive targets (I, Np and Pu) were contained in weld-sealed aluminium holders produced by the Institute of Physics and Power Engineering, Obninsk, Russia. Spallation neutrons were produced by relativistic protons with energies in the range of 0.5 GeV≤Ep≤1.5 GeV interacting with 20 cm long uranium or lead target stacks. The metallic targets were surrounded by 6 cm thick paraffin moderators. The uranium and lanthanum samples were positioned on the outside of the moderator surface and typically contained approximately 0.5 to 1.0 gram of uranium or lanthanum. The highest fluence of spallation neutrons was observed in the region of 5 to 10 cm downstream the entrance of the primary beam into the metallic target, rather independent of the target material or the proton energy. The results obtained by nuclear chemistry methods were supplemented by SSNTD (Solid State Nuclear Track Detector) studies. Consistent and systematic results ofB-values and spectral distributions for neutrons have been found. From the experimentally observed transmutation rates one can extrapolate that in a subcritical nuclear power assembly (or "energy amplifier") using a 10 mA proton beam of 1 GeV onto a Pb-target as used here, one can transmute within one month in one gram of sample about 3 mg129I, 21 mg237Np, 3.3 mg238U, and 200 mg239Pu. Rather similar results have been found by another group for129I and239Pu. Observations show that the transmutation rates increase almost linearly with the proton energy in the energy interval 0.5 GeV up to 7.4 GeV. These findings are largely confirmed by model calculations using the LAHET- and DCM/CEM-codes.

Transmutation rates of 239Pu and some minor actinides (237Np, 241Am, 245Cm and 246Cm), in two accelerator-driven systems (ADS) with lead or graphite moderating environments, were calculated using the LAHET code system. The ADS that were used had a large volume (∼32 m3) and contained no fissile material, except for a small amount of fissionable waste nuclei that existed in some cases. Calculations were performed at an incident proton energy of 1.5 GeV and the spallation target was lead. Also breeding rates of 239Pu and 233U as well as the transmutation rates of two long-lived fission products 99Tc and 129I were calculated at different locations in the moderator. It is shown that an ADS with graphite moderator is a much more effective transmuter than that with lead moderator.

The LAHET code system is used to study the behaviour of the spallation neutrons resulting from the interaction of 2.5 GeV/c protons with a massive lead target within a large (∼32 m3) lead and graphite moderating environments. The spatial and energy distribution of the neutrons with presence and absence of a fissile material in Accelerator Driven Systems (ADS) are investigated. It is shown that the energy spectra of the neutrons in graphite and lead moderators are very different and such difference is expected to result in noticeable differences in the nuclear waste transmutation abilities of the ADSs that use graphite and lead for neutron moderation and storage.

We summarize here the results of the TARC experiment whose main purpose is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS proton beam line to study how neutrons produced by spallation at relatively high energy ( E n ⩾1 MeV ) slow down quasi-adiabatically with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 and 3.5 GeV/c protons) slowing down in a 3.3 m×3.3 m×3 m lead volume and of neutron capture rates on LLFFs 99Tc, 129I, and several other elements were performed. An appropriate formalism and appropriate computational tools necessary for the analysis and understanding of the data were developed and validated in detail. Our direct experimental observation of ARC demonstrates the possibility to destroy, in a parasitic mode, outside the Energy Amplifier core, large amounts of 99Tc or 129I at a rate exceeding the production rate, thereby making it practical to reduce correspondingly the existing stockpile of LLFFs. In addition, TARC opens up new possibilities for radioactive isotope production as an alternative to nuclear reactors, in particular for medical applications, as well as new possibilities for neutron research and industrial applications.

The Transmutation by Adiabatic Resonance Crossing (TARC) experiment was carried out as PS211 at the CERN PS from 1996 to 1999. Energy and space distributions of spallation neutrons (produced by 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3×3.3×3 m3 lead volume and neutron capture rates on long-lived fission fragments 99Tc and 129I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.

Suggestions for superpowerful linear accelerators for electronuclear setups and high-intensity neutron generators are reviewed. The most important technical solutions, the characteristic features, and the state of the projects for linear accelerators with average accelerated beam power from 1 to 100 MW are examined: APT, SNS, JAERI/KEK, TRISPAL, TRASCO, ESS, KOMAC, Energy Amplifier, IFMIF, joint proposal by the Institute of Theoretical and Experimental Physcis, the Moscow Radio Electronics Institute, the Institute for High-Energy Physics, and other nuclear centers. 8 figures, 3 tables, 74 references.

The Feynman-alpha and Rossi-alpha formulae are derived analytically for subcritical systems driven by a multiple emission source,i.e. one that emits several neutrons on each source emission event. The prime example of such sources is a spallation source, which will be used in future accelerator driven subcritical systems (ADS) such as the energy amplifier. Such formulae for ADS have been derived recently but in simpler neutronic models. In this paper six groups of delayed neutron precursors are taken into account, and the full joint statistics of the prompt and all delayed groups is included. Thus the present results are generalisations of earlier ones. The involved problems that are encountered are solved with a combination of effective analytical techniques and symbolic algebra codes.

The conceptual Fast Energy Amplifier, proposed by Rubbia et al. consists of a combination of a U-233/Th-232 fuelled fast-neutron subcritical facility with a proton accelerator. An intense beam of 1 GeV protons is injected into liquid lead at the core centre and drives the reactor by producing spallation neutrons. The burst of spallation neutrons produced by a single proton alters the basic neutron statistics which are well known for thermal neutrons in conventional nuclear reactors. A short assessment of standard neutron noise analysis methods is made with respect to monitoring neutron parameter data.

We investigate a compact, pulsed racetrack microtron as an energy amplifier and bunch compressor to produce bunch charges of ∼100 pC in beams with a peak current of ∼30 A or more having longitudinal emittance of 50 keV × deg and transverse emittance of 5–15π mm × mrad with energies from 5 to 35 MeV selectable in 2.5 MeV steps.

A uranium thermometer has been designed and built in order to make local power measurements in the First Energy Amplifier Test (FEAT). Due to the experimental conditions power measurements of tens to hundreds of nW were required, implying a sensitivity in the temperature change measurements of the order of 1 mK. A uranium thermometer accurate enough to match that sensitivity has been built. The thermometer is able to determine the absolute energetic gain obtained in a tiny subcritical uranium assembly exposed to a proton beam of kinetic energies between 600 MeV and 2.75 GeV. In addition, the thermometer measurements have provided information about the spatial power distribution and the shape of the neutron spallation cascade.

The feasibility of cyclotrons to produce high power beams is discussed based on the experience gained with the operation of the upgraded 590 MeV cyclotron facility at PSI in Villigen (Switzerland) at a beam power level up to 0.9 MW. In view of new applications of particle beams in neutron spallation sources, energy amplifier and transmutation technologies a possible design of a 1 GeV cyclotron is presented that would be capable to deliver a 10 MW beam, based on the same contruction principles as used in the PSI 590 MeV Ring cyclotron. Questions concering power conversion efficiency, beam loading and space charge forces are discussed. Space charge effects are not expected to be a major problem in the high energy cyclotron, but they play an important role in the preaccelerator and further studies are needed to propose an optimized configuration.

A fission detector developed for the first energy amplifier test made at CERN-PS during the period September–October 1994 [1,2] will be described. The device is a small dimension high pressure argon gas ionization chamber with high background rejection and very high efficiency on 2π for fission fragments. The number of fissions produced in a fissile target allows the neutron flux measurement.

A new view upon an energy amplifier (based on a subcritical reactor driven by an accelerator motivated source of neutrons) as a system united by the energy flow between the accelerator and the subcritical reactor is given in the paper. A new approach to the calculation of the gain of the energy amplifier using the neutron balance equation is also introduced. The expression for the gain obtained here is compared with an expression derived earlier [C. Rubbia et al.: Rep. ISC 93-31, ISC/P 57, CERN, 1993].

An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 109 ppp) proton beam from CERN-PS at several kinetic energies from 600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically G ≈ 30 in reasonable agreement with calculations, where G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which G decreases but is still acceptable in the energy range explored

We describe a new approach for commercial nuclear energy production without a long-term high-level waste stream and for transmutation of both fission product and higher actinide commercial nuclear waste using a thermal flux of accelerator-produced neutrons in the 1016 n/cm2s range. Continuous neutron fluxes at this intensity, which is approximately 100 times larger than is typically available in a large scale thermal reactor, appear practical, owing to recent advances in proton linear accelerator technology and to the spallation target-moderator design presented here. This large flux of thermal neutrons makes possible a waste inventory in the transmutation system which is smaller by about a factor of 100 than competing concepts. The accelerator allows the system to operate well below criticality so that the possibility for a criticality accident is eliminated. No control rods are required. The successful implementation of this new method for energy generation and waste transmutation would eliminate the need for nuclear waste storage on a geologic time scale. The production of nuclear energy from 232Th or 238U is used to illustrate the general principles of commercial nuclear energy, production without long-term high-level waste. There appears to be sufficient thorium to meet the world's energy needs for many millenia.

Because of the safer and more reliable mode of operation, a Superconducting Linac has been proposed as the proton beam accelerator which drives a nuclear plant based on the concept of the Energy Amplifier. An example based on the net generation of 400 MW (electric) is described. This requires a proton beam energy of 1 GeV with a continuous beam current of 10 mA, corresponding to a beam power of 10 MW. Two frequencies cases, 360 and 805 MHz, have been considered for the Linac design. Performance and cost comparison for the two cases are given.

The Sincrotrone Trieste proposal for a 100 MeV proton accelerator, driving a 1+2.5 GeV booster linac for the Energy Amplifier Project, is based on a Multi-Tank Drift Tube Linac (MTDTL) structure, since it seems to be the most simple and efficient solution for a high power, CW proton beam. The optimization of the RF system, in terms of efficiency and cost, is a crucial point in the design of the MTDTL. A possible solutions for the low level distribution and the RF power distribution are presented and analysis of the efficiencies are given.

The science and technology of proton accelerators have progressed considerably in the past three decades. Three to four orders of magnitude increase in both peak intensity and average flux have made it possible to construct high intensity proton accelerators for modern applications, such as: spallation neutron sources, kaon factory, accelerator production of tritium, energy amplifier and muon collider drivers. The accelerator design focus switched over from intensity for synchrotrons, to brightness for colliders to halos for spallation sources. An overview of this tremendous progress in both accelerator science and technology is presented, with special emphasis on the new challenges of accelerator physics issues such as: H/sup -/ injection, halo formation and reduction of losses.

For the design of the linear optics of the superconducting linear accelerator for a Full Scale Energy Amplifier, a computer code is under development for the 3-dimensional linear motion with space charge and transverse cavity effects included. A sequential matching routine allows an easy optimization of the optics for the long structure of the linear accelerator. The program is described and first results of the optics optimization for the linear accelerating structure are discussed.

The goal of this accelerator complex is to provide a 10 MW proton beam for driving the Energy Amplifier recently proposed by C. Rubbia. It is lower (by one order of magnitude) than the requirements of most of the accelerator-driven projects based on c-w linacs. Therefore, the requirements for the Energy Amplifier open an alternative solution based on ring cyclotrons producing a continuous beam. Thus taking into account the present development of high-intensity cyclotrons, a three-stage cyclotron accelerator is a possible solution. It comprises of: (1) the injector(s) which should be able to deliver a 10 mA beam in a given phase width-a solution based on two 5mA compact isochronous cyclotrons working in parallel is proposed; (2) the intermediate stage which is a four-separated-sector cyclotron accelerating the injected beam up to 120 MeV; and (3) the final booster which has ten separated sectors and six cavities raising the kinetic energy up to about 1000 MeV.

To provide beams with characteristics required by the Energy Amplifier Test, the CERN PS had to deliver new beams, of low kinetic energy (0.6-2.7 GeV), low intensity (0.5-5/spl times/10/sup 9/ p) and short duration (

The performance of the PSI cyclotron facility is described in detail. The facility consists of the 72 MeV injector cyclotron and the 590 MeV Ringcyclotron. It is used as a powerful driver for the routine production of a 1 MW proton beam for SINQ, the spallation neutron source at PSI. In July 2000 a record beam current of 2 mA could be extracted form the Ringcyclotron. All aspects relevant to the high intensity operation of the cyclotrons are discussed, such as bunching, beam collimation, beam loss, activation and space charge effects at low energies as well as at the high-energy end. Based on the experience with 1 MW beam power the performance is extrapolated to higher beam intensities and some assessments are made on the feasibility of using cyclotrons as possible drivers for the production of e.g. 10 MW beam power in view of future applications in transmutation technologies, in the energy amplifier or to generate high flux secondary beams of neutrons, pions or other particles.

In the framework of the Italian participation in the project of a high intensity proton facility for the energy amplifier and nuclear waste transmutations, LNL is involved in the design and construction of same prototypes of the injection system of the 1 GeV linac that consists of a RFQ (5 MeV, 30 mA) followed by a 100 MeV linac. This program has already been supported financially and the work is in progress. In this context LNL has proposed a project for the construction of a second generation facility for the production of radioactive ion beams (RIBs) by means of the ISOL method. The final goal is the production of neutron rich RIBs with masses ranging from 30 to 150 by using primary beams of protons, deuterons and light ions with energy of 100 MeV and 100 kW power. This project is expected to be developed in about 10 years from new and intermediate milestones and experiments are foreseen and under consideration for the next INFN five year plan (1999-2003). During that period the construction of a proto...

In the frame work of the Italian participation to the project of a high intensity proton facility for the energy amplifier and nuclear waste transmutations, LNL is involving in the design and construction of prototypes of the injection system of the 1 GeV linac that consists of a RFQ (5 MeV, 30 mA) followed by a 100 MeV linac. This program has been already financially supported and the work is actually in progress. In this context, the LNL has been proposed a project for the construction of a second generation facility for the production of radioactive ion beams (RIBs) by using the ISOL method. The final goal consists in the production of neutron rich RIBs with masses ranging from 80 to 160 by using primary beams of protons, deuterons and light ions with energy of 100 MeV and 100 kW power. This project is proposed to be developed in about 10 years from now and intermediate milestones and experiments are foreseen and under consideration for the next INFN five year plan (1999–2003). In such period of time is proposed the construction of a proton/deuteron accelerator of 10 MeV energy and 10 mA current, consisting of a RFQ (5 MeV, 30 mA) and a linac (10 MeV, 10 mA), and of a neutron area dedicated to the RIBs production, to the BNCT applications and to the neutron physics. Some remarks on the production methods will be presented. The possibility of producing radioisotopes by means of the fission induced by neutrons will be investigated and the methods of production of neutrons will be discussed.

In the frame work of the Italian participation to the project of a high intensity proton facility for the energy amplifier and nuclear waste transmutations, the LNL has been proposed a project for the construction of a second generation facility for the production of radioactive ion beams (RIBs) by using the ISOL method. The final goal consists in the production of neutron rich RIBs with masses ranging from 80 to 160 by using primary beams of protons/deuterons with energy of 100 MeV/u and 100 kW power. This project is proposed to be developed in about 10 years from now and intermediate milestones and experiments are foreseen and under consideration for the next INFN five year plan (1999-2003). In such period of time is proposed the construction of a deuteron accelerator of 20 MeV energy and 5 mA current, consisting of a RFQ (5 MeV) and a linac (20 MeV), and of a neutron area dedicated to the RIBs production and other applications. Besides the RIBs production, neutron beams for the BNCT applications and neutron physics are also planned.

The use of accelerator driven system (ADS) like for instance the Energy Amplifier concept (EA) proposed by C. Rubbia and his group might be one of the solutions to solve the energy problem and in particular to answer the question: what could we do with the nuclear waste produced by the present nuclear reactors? We present in this paper the EA concept, which is illustrated by two experiments performed at the CERN-PS facility. One of them is the TARC (Transmutation by Adiabatic Resonance crossing) experiment which is designed to demonstrate the high efficiency offered by the EA to destroy the long-lived fission fragments.

The conceptual design of Rubbia et al. CERN/AT/95-44 (ET), 1995, for an accelerator driven system, known as the Energy Amplifier (EA), proposes use of a spallation neutron source that is in turn induced by protons from a Cyclotron or a Linac, in a subcritical array that makes use of liquid lead coolant. This paper introduces some qualitative changes to the concept of Rubbia et al. examining use of more than one point of spallation, in order to reduce the requirements placed on proton energy and current of the accelerator, and specifically to obtain a flatter power density distribution.

Neutron activation of structural materials gives rise to an energy release during the subsequent radioactive decay. In large devices for energy production like a fission reactor, the future proposed Energy Amplifier or a Fusion power plant, this energy release represents a source of heat, which although at a very much lower level than the heating during operations is of the order of MWs for large nuclear power plants. Accurate estimation of the decay power is essential for safety analyses of the power plant against loss of coolant accidents, etc. Some computer codes have been developed to predict the decay power, but validation of the computer codes through experimental measurements is essential. A new large, almost 4π detector, formed by coupling a well-type CsI scintillator and a small plastic β detector has been developed for accurate and efficient measurements of decay power from γ and β radiation. Preliminary measurements of decay power produced in neutron-activated tungsten are presented and compared with the predictions of the European Activation Code System, EASY-99.