Accelerator-driven Transmutation Technology Research Articles

Neutrons from a Proton-Driven Deuterium Target as a Possible Competitor to Spallation for Nuclear Energy Applications

Measurements are reported on the yield of neutrons from protons in the energy range from 7 to 17 MeV striking a stopping-length target of deuterium gas. This combination of beam and target is being investigated as an alternative to spallation for accelerator-driven transmutation technology with perhaps equivalent or lower energy cost per neutron. The concept includes neutrons produced from a cascade of reactions starting with the p + d reaction giving rise to subsequent fusion neutrons and neutrons from higher-order breakup reactions. In our application the incident proton energy is expected to be ~100 MeV so that most of the neutrons produced in these reactions will be higher-energy neutrons that can undergo multiplication in surrounding beryllium or lead. The results reported here for lower proton energies indicate that the expected fusion and higher-order breakup reactions have been observed, and they provide the basis for a measurement at 100 MeV to confirm the larger proton-induced cascade benefits expected at higher proton energies.

Displacement and helium-induced enhancement of hydrogen and deuterium retention in ion-irradiated 18Cr10NiTi stainless steel

There is strong interest in the accelerator-driven transmutation technology community on the synergistic effects of displacement damage and co-generated helium and hydrogen on property changes such as void swelling, irradiation creep, hardening, and possibly on corrosion and cracking. Substituting deuterium for protium offers advantages in experimental studies of the helium–hydrogen-damage synergisms. The influence of preimplanted helium and self-ion induced damage on deuterium trapping in 18Cr10NiTi stainless steel was studied using thermal desorption spectrometry, the nuclear reactions 3He(D, p) 4He and D( 3He, p) 4He, and transmission electron microcopy. Reemission, retention and evolution of depth distribution profiles of deuterium in 18Cr10NiTi SS were studied for 10 keV D 2 + and 10 keV He + implantation at room temperature followed by annealing at 300–1500 K. The amounts of trapped and released deuterium and helium atoms were measured as a function of implantation dose at various temperatures. It was found that retention of hydrogen and deuterium is strongly enhanced by the presence of large amounts of helium and also strongly enhanced by damage introduced by 2 MeV Cr 3+ ions. These results are consistent with recent observations of hydrogen storage in stainless steels after irradiation in LANSCE with high energy protons and neutrons and also after irradiation in light water reactors.

The accelerator driven system strategy in Japan

Recent status of study on accelerator driven system (ADS) in Japan is presented. The double-strata fuel cycle concept has been proposed by Japan Atomic Energy Research Institute (JAERI) under the `OMEGA' program as a system for partitioning and transmutation (P&T) of long-lived radioactive nuclides. The ADS dedicated to transmutation is the key technology of the double-strata fuel cycle concept. The proposed system is a lead–bismuth cooled, nitride fuel 800 MW ADS for transmutation of minor actinides and long-lived fission products. JAERI has carried out a conceptual design study under the joint project between JAERI and KEK (High Energy Accelerator Research Organization) on high-intensity proton accelerators. In addition to a high-intensity proton accelerator complex, two experimental facilities are planned for development and demonstration of accelerator driven transmutation technology: The major objective of an ADS physics experimental facility is to obtain reactor physics data of hybrid subcritical system. The major objective of an ADS engineering experimental facility is to accumulate material data for the design of a lead–bismuth target system.

Absorption of molten fluoride salts in glassy carbon, pyrographite and Hastelloy B

Materials performance is one of the issues of the accelerator driven transmutation technology (ADTT). Identification of the materials, which would satisfy the strength and integrity requirements for the target–blanket assembly (e.g. corrosion and radiation resistance), is a significant challenge. We report on the study of the interaction (i.e. penetration and capture) of molten fluoride salts with glassy carbon, pyrolitic graphite, and Hastelloy B, which are considered as candidates for structural materials of the ADTT systems. Massive penetration into and capture of molten fluorides within a several micrometer thick surface layer was observed for all inspected specimens. The incorporation rate of the molten fluorides depends on the exposure time and temperature of the molten fluoride bath. The corrosion resistance of the specimens was verified in stationary conditions. Whereas excellent resistance has been found for pyrolitic graphite, evident corrosion was observed for glassy carbon and particularly for Hastelloy B.

Molten fluoride salts incorporation into pristine and ion-modified carbon allotropes and metallic foils

Incorporation of molten fluoride salts into different carbon allotropes (glassy carbon, pyrolytic graphite etc.) and metallic foils (Ni, Ti, etc.), pristine and ion- treated substances, has been studied using non-destructive, depth sensitive nuclear analytical methods—Neutron Depth Profiling (NDP) and Rutherford Backscattering (RBS). Strong interaction between the molten LiF and LiF+KF+NaF salts and the tested materials was found. The results are of great interest for accelerator driven transmutation technology (ADTT) which is a promising way towards effective liquidation of nuclear wastes.

A concept for a high-flux spallation neutron source as a radiation damage test facility

A high-flux neutron generator is proposed conceptually. Its spallation target facility is designed to accept a proton beam with parameters close to those of the LAMPF linear accelerator at the Los Alamos National Laboratory (0.8 GeV and 1.6 mA). Fluxes of 1.5 to 2.5×10 15 ns −1 cm −2 are formed in the target facility by a scanning proton beam. This facility is proposed to test the feasibility of the spallation target, especially the target window and coolant circulation, as well as to study other materials under high radiation. Alternatives based on the liquid lead and gas-cooled tungsten particles are compared. In the proposed target, spallation neutrons provide 2–3 times higher rates of radiation damage than fast reactor neutrons due to their harder spectrum. This generator is considered as an integral test facility in the framework of studies for accelerator driven transmutation technologies.

Prompt nuclear analytical techniques for material research in accelerator driven transmutation technologies: Prospects and quantitative analyses

Accelerator driven transmutation technology (ADTT) is a promissing way toward liquidation of spent nuclear fuel, nuclear wastes and weapon grade Pu. The ADTT facility comprises a high current (proton) accelerator supplying a subcritical reactor assembly with spallation neutrons. The reactor part is supposed to be cooled by molten fluorides or metals which serve, at the same time, as a carrier of nuclear fuel. Assumed high working temperature (400–600°C) and high radiation load in the subcritical reactor and spallation neutron source put forward the problem of optimal choice of ADTT construction materials, especially from the point of their radiation and corrosion resistance when in contact with liquid working media. The use of prompt nuclear analytical techniques in ADTT related material research is considered and examples of preliminary analytical results obtained using neutron depth profiling method are shown for illustration.

Development of a high-current microwave ion source for Korean Multipurposed Accelerator (abstract)

A high-current, proton linear accelerator, named as Korean multipurposed accelerator (KOMAC), is being proposed mainly for accelerator-driven transmutation technology (ADTT) by Korea Atomic Energy Research Institute (KAERI). High-current, low emittance continuous power (cw) linear accelerators favor electron cyclotron resonance (ECR) microwave ion sources as an injector (Ref. Reference 1). Recently, these microwave sources are developed and constructed by several institutes especially for high-current cw linear accelerators. A high-density microwave ion source has been designed and constructed as a prototype ion source for the proposed KOMAC linear accelerator. The design of microwave power injection system is similar to that of the 75 keV proton injector at Los Alamos National Laboratory (Ref. Reference 2). A 2.45 GHz, 1.5 kW magnetron source is introduced into the stainless steel plasma chamber with 10 cm diam and 20 cm length through a tapered, double-ridged waveguide and a quartz window. The microwave power supply is separated from the plasma chamber by a high-voltage waveguide break. Axial magnetic fields up to 1 kG can be provided by two sets of water-cooled solenoid coils. A single-hole extraction system is designed for extraction current up to 50 mA at 50 kV extraction voltage. The design and initial operations of the ion source in ECR regimes will be presented.

The technological status of accelerator-Driven nuclear systems for transmutation and energy production

A review is given of the technological status of accelerator-driven nuclear systems for transmutation and energy production based on information given at the 2nd International Conference on Accelerator-Driven Transmutation Technologies and Applications held on June 3–7, 1996 at Kalmar, Sweden. The review includes the present status of accelertor, target/blanket and separation techniques. Aspects on safety and proliferation issues of accelerator-driven systems are also given.

The Coaxial-Ring Cyclotron as a powerful multipurpose proton accelerator

The concept and general layout of a new high-power proton multistage isochronous cyclotron is presented. Key design features include the use of large-diameter cyclotron rings having low magnetic fields and the coaxial nesting of several cyclotron stages. The proposed Coaxial-Ring Cyclotrons (CRC) accelerator system has several advantages as compared to conventional cyclotrons. It has wide turn-to-turn separation of orbits, high energy gains per turn with small number of turns in each cyclotron stage, to produce high space-charge-limited beam current, simplified beam injection and extraction at low loss, an ability to inject and simultaneously accelerate multiple independent beams, and to extract different energy beams from the intermediate orbits of cyclotron stages. One or several Radio Frequency Quadrupole (RFQ) injectors are used to provide the necessary high brightness injection. Thus, a high-current, 1.5-GeV highly-efficient and cost-effective accelerator system is conceived, specifically to serve as the proton driver in several applications of the Accelerator Driven Transmutation Technologies (ADTT), and also to serve as a photon cancer therapy source, a materials processing source, as well as to act as a high-quality accelerator for the conduct of fundamental research in physics with intense beams of neutrons, neutrinos, muons and mesons. This paper describes the general layout of the nested five stages of cyclotrons, to produce 1.0-to-1.5-GeV, 1.0-to-20-mA average-current protons in single-beam injection, or higher currents by multiple-beam injection, fitting into the 70-m diameter main ring and the inner circular hall of the existing 6-GeV Yerevan Electron Synchrotron, and converting all related facilities.

Overview of advanced proton driver for neutron transmutation systems

A linear accelerator for the driver of a mu-mu collider can easily be based on operating characteristics of the Los Alamos Neutron Science Center (LANSCE) linac, or can incorporate many of the advances that have been realized from the Accelerator Driven Transmutation Technologies (ADTT) studies, from the Accelerator Production of Tritium (APT) developments, and from the Strategic Defense Initiative (SDI) developments.

Accelerator-driven transmutation technology for incinerating radioactive waste and for advanced application to power production

Recent work at Los Alamos has revealed new techniques leading to greatly enhanced feasibility for using intense particle accelerators to drive systems for burning existing radioactive waste, and for electrical power generation with a much reduced waste stream in the future. The system requires the intense flux levels that can only be provided by an accelerator to exploit thermal energy neutrons for transmutation; thus the new physics of transmutation is different and more advanced than earlier ideas. Another key aspect affords the use of a dilute inventory system that reduces significantly the amount of fertile/fissile material required in the system at one time, with significant safety and engineering advantages. These concepts will be reviewed, and the requirements on the accelerator, which is on the order of 1.5 GeV, 50–250 mA continuous current, will be outlined.