Takakazu Takizuka

Review of research and development of accelerator-driven system in Japan for transmutation of long-lived nuclides

Abstract Active and comprehensive studies on an accelerator-driven subcritical system (ADS) for transmutation of long-lived nuclides have been carried out at the Japan Atomic Energy Research Institute (JAERI). In the late 1970s, JAERI started the basic study of this subject and later, comprehensive studies have been performed under the “OMEGA” program of Japan: the long-term program for research and development on partitioning and transmutation (P&T) technology. Based on a design study of a dedicated transmutation system, JAERI decided to concentrate its efforts for transmutation study on the development of ADS. The construction of an experimental facility for the ADS development was proposed as a part of the Neutron Science Project of JAERI, which aimed at the construction of the world most powerful spallation neutron source. Since 1998, JAERI and the High Energy Accelerator Research Organization (KEK) are jointly proposing a High-Intensity Proton Accelerator Project. An ADS experimental facility composed of a subcritical assembly and a liquid lead-bismuth target/coolant engineering facility will be constructed under this project. In this paper, the development of ADS at JAERI, together with related technologies of P&T, both under the OMEGA program and the joint proposal, is reviewed. Other activities on ADS study in Japan are also reviewed.

Cost and performance design approach for GTHTR300 power conversion system

Japan Atomic Energy Research Institute (JAERI) has been carrying out a design and developmental program for the gas turbine high temperature reactor of 300 MWe nominal-capacity (GTHTR300) power plant, aiming at prototype demonstration in Japan during 2010s. This paper introduces overall objectives of the program and describes the plant design and development approach taken to achieve these goals. A detailed description is focused on the power conversion system design and associated component research and development undertaken in the present program. The power conversion system incorporates unique design approach of non-intercooled cycle to attain economical performance at minimal system complexity, intrinsic cycle flow provision for reactor pressure vessel cooling, simplified and high-performance turbomachine in a horizontal design, and modularity of maintenance for all major power conversion equipment. This paper reports extensive technical evaluation related to these significant system design features, which are shown to offer the optimum solution of plant cost, efficiency potential, reliability and maintainability in addition to near-term commercial deployment.

Design study of lead-bismuth cooled ADS dedicated to nuclear waste transmutation

Research and development on nuclear waste transmutation are being carried out with a special emphasis placed on dedicated accelerator-driven systems at the Japan Atomic Energy Research Institute under the Japanese OMEGA Program. The reference accelerator-driven system design employs eutectic lead-bismuth as spallation target material and coolant. The fuel for the subcritical core is minor-actinide mononitride. The system consists of a 1.5GeV, 14mA proton accelerator and an 800MWt subcritical core with an effective neutron multiplication factor of 0.95. The transmutation rate of minor actinides is approximately 250 kg/y at 80% load factor. The design has salient features that the coolant inventory is large due to the tank-type configuration, the temperature rise through the core is relatively low, and the power conversion is operated on a saturated steam turbine cycle. These features make the plant response to a beam trip slow and much less demanding.

Accelerator-driven system for transmutation of high-level waste

Abstract The accelerator-driven transmutation system has been studied at the Japan Atomic Energy Research Institute. This system is a hydrid system which consists of a high intensity accelerator, a spallation target and a subcritical core region. In the conceptual design study, two types of system concepts, sodium cooled and lead-bismuth cooled system, are being studied. In this study, we fucus on our lead-bismuth cooled accelerator-driven transmutation system to investigate basic characteristics. The fuel compositions were optimized for efficient transmutation of minor actinide. The transmutation of long-lived fission products was also considered.

Partitioning and transmutation studies at JAERI both under OMEGA program and high-intensity proton accelerator project

Abstract At the Japan Atomic Energy Research Institute (JAERI), active and comprehensive studies on partitioning and transmutation (P&T) of long-lived nuclear waste from the reprocessing processes of spent fuel has been carried out under the OMEGA program. Studies at JAERI include a design study of dedicated transmutation systems both of an MA burner fast reactor (ABR) and an accelerator-driven subcritical system (ADS), and the development of a high intensity proton accelerator as well as the development of partitioning process, nitride fuel fabrication/dry separation process technologies and nuclear data studies. During the course of studies, JAERI developed the concept of the double-strata fuel cycle, in which a dedicated system is used for transmutation. Comparing the various transmutation systems, such as thermal neutron spectrum or fast neutron spectrum systems, power reactors or dedicated systems, from the viewpoints of reactor physics, nuclear fuel cycle and socio-technical issues, it was concluded that the ADS is the best option for transmutation of minor actinide(MA). JAERI, therefore, decided to concentrate its R&D efforts on the development of ADS and related technologies. One of the goals of R&D is to provide a basis for designing demonstration facilities of ADS, aqueous partitioning process and nitride fuel fabrication and dry separation technologies. As the initial step toward this purpose, the construction of an ADS experimental facility is planned under the High-Intensity Proton Accelerator Project which JAERI and the High Energy Accelerator Research Organization (KEK) are jointly proposing since 1998. The paper discusses the some of the results of P&T studies and the outline of the High-Intensity Proton Accelerator Project under which ADS experimental facility will be constructed.

Transmutation of long-lived radioactive waste based on double-strata concept

A considerable attention is directed toward the reduction in the long-term potential hazard by partitioning and transmutation (P-T): separating long-lived nuclides from the waste stream and converting them into either shorter-lived or non-radioactive ones. The effects of higher Pu and minor actinide (MA) compositions on the transmutation rates have been studied for a typical mixed oxide (MOX)-fuel fast breeder reactor (FBR) core with 2600 MWt. The calculations showed that the transmutation rate for (Pu, MA) compositions from MOX -LWR becomes one half than that from UO 2 -light water reactor (LWR). Furthermore, MA accumulation and transmutation based on Double-Strata Scenario have been investigated for introducing the accelerator driven transmutation system (ADS) with 800 MWt. It was shown that in the scenario of nuclear plant capacities for maximum 140 GWe, which consists of LWRs and FBRs, the introduction of ADS can play a significant role as Transmuter in the back-end of fuel cycle.

Code development for the design study of the OMEGA Program accelerator-driven transmutation systems

Abstract The Japan Atomic Energy Research Institute carries out R&D on accelerator-driven transmutation systems (ADTS) under the national OMEGA program (Options Making Extra Gains from Actinides and fission products). The code system named ATRAS was developed to analyze neutronics and burnup characteristics of ADTS. It has a unique function of burnup analysis taking into account the effect of the spallation neutron source. ATRAS consists of a hadronic cascade code, a neutron transport code and a burnup analysis code. Utility programs for fuel exchange, pre-processing and post-processing were also incorporated. The neutronics design study of a spallation target as well as the analysis of the neutronics and burnup characteristics of the sodium-cooled ADTS were performed using ATRAS.

JAERI R&D on accelerator‐based transmutation under OMEGA program

The overview of the Japanese long‐term research and development program on nuclide partitioning and transmutation, called ‘‘OMEGA,’’ is presented. Under this national program, major R&D activities are being carried out at JAERI, PNC, and CRIEPI. Accelerator‐based transmutation study at JAERI is focused on a dedicated transmutor with a subcritical actinide‐fueled subcritical core coupled with a spallation target driven by a high intensity proton accelerator. Two types of system concept, solid system and molten‐salt system, are discussed. The solid system consists of sodium‐cooled tungsten target and metallic actinide fuel. The molten‐salt system is fueled with molten actinide chloride that acts also as a target material. The proposed plant transmutes about 250 kg of minor actinide per year, and generates enough electricity to power its own accelerator. JAERI is proposing the development of an intense proton linear accelerator ETA with 1.5 GeV‐10 mA beam for engineering tests of accelerator‐based transmutat...

Crossflow characteristics of HTGR fuel blocks

Abstract Leakage crossflow characteristics in an HTGR core have been studied experimentally and numerically. Two-block crossflow experiments were carried out and the crossflow rate and the pressure difference were measured for various interface gap configurations. A numerical model has been proposed to predict crossflow rates, and the numerical results using the finite element method agreed well with experimental ones. In addition, empirical crossflow equations, which apply to various fuel blocks, were derived for the analysis of the flow distribution in an HTGR core.

Flow around turbulence promoters in parallel channel, (I). Flow patterns around cylinder-type turbulence promoters.:Flow Patterns around Cylinder-Type Turbulence Promoters

Flow characteristics in relation to heat transfer characteristics in parallel channel with turbulence promoters were studied experimentally. Flow visualization experiments were made in paralle channel with one or two turbulence promoters for Reynolds number region of 100≤Rew≤3,600. The vortex patterns behind one promoter were that a steady vortex was formed for low Reynolds number and vortex was shed for high Reynolds number. For higher Reynolds number, it was observed that shedding vortex caused other vortices or disappeared itself randomly. The results indicate that the shedding vortices will augment heat transfer, whereas the steady vortex will give rise to deterioration in heat transfer. This inference agrees with the experimental results of Hishida et al. The results of two promoters experiment showed that the maximum performance of promoter would be attained at p/d–7. This agrees with the results formerly studied by other investigators.