Japan Atomic Energy Research Institute Research Articles

Corrections to the 148Nd method of evaluation of burnup for the PIE samples from Mihama-3 and Genkai-1 reactors

The value of the burnup is one of the most important parameters of samples taken by post-irradiation examination (PIE). Generally, it is evaluated by the Neodymium-148 method. Precise evaluation of the burnup value requires: (1) an effective fission yield of 148Nd; (2) neutron capture reactions of 147Nd and 148Nd; (3) a conversion factor from fissions per initial heavy metal to the burnup unit GWd/t. In this study, the burnup values of the PIE data from Mihama-3 and Genkai-1 PWRs, which were taken by the Japan Atomic Energy Research Institute, were re-evaluated using more accurate corrections for each of these three items. The PIE data were then re-analyzed using SWAT and SWAT2 code systems with JENDL-3.3 library. The re-evaluation of the effective fission yield of 148Nd has an effect of 1.5–2.0% on burnup values. Considering the neutron capture reactions of 147Nd and 148Nd removes dependence of C/E values of 148Nd on the burnup value. The conversion factor from FIMA(%) to GWd/t changes according to the burnup value. Its effect on the burnup evaluation is small for samples having burnup of larger than 30 GWd/t. The analyses using the corrected burnup values showed that the calculated 148Nd concentrations and the PIE data is approximately 1%, whereas this was 3–5% in prior analyses. This analysis indicates that the burnup values of samples from Mihama-3 and Genkai-1 PWRs should be corrected by 2–3%. The effect of re-evaluation of the burnup value on the neutron multiplication factor is an approximately 0.6% change in PIE samples having the burnup of larger than 30 GWd/t. Finally, comparison between calculation results using a single pin-cell model and an assembly model is carried out. Because the results agreed with each other within a few percent, we concluded that the single pin-cell model is suitable for the analysis of PIE samples and that the underestimation of plutonium isotopes, which occurred in the previous analyses, does not result from a geometry model.

Measurements of deuteron-induced activation cross sections for IFMIF accelerator structural materials in the energy range of 22–40 MeV

In order to investigate the activation performance of prospective materials of the IFMIF facility, we have carried out irradiation experiments with the AVF cyclotron in the TIARA facility of the Japan Atomic Energy Research Institute (JAERI). We measured the production cross sections of the nuclides Cu-61, Cu-64, Zn-62 and Zn-63 by deuterons irradiation of copper with natural isotope abundance ( natCu) in the energy range of 22–40 MeV. The obtained cross sections were compared with data from the ACSELAM library and with previously measured cross section data. The comparisons revealed that some of the ACSELAM cross section data are different from the experimental data and have to be improved.

高温ガス炉ガスタービン発電システム(GTHTR300)の経済性評価

Japan Atomic Energy Research Institute (JAERI) has been developing a graphite moderate and helium cooled High Temperature Gas-cooled Reactor (HTGR) with gas turbine, the GTHTR300 based on experience gained in development and operations of the High Temperature Engineering Test Reactor (HTTR) in JAERI. The GTHTR300 is a simplified and economical power plant with a high level of safety characteristics and a high plant efficiency of approximately 46%. Cost evaluation for plant construction and power generation is studied in order to clarify the economical feasibility of the GTHTR300. The construction cost is estimated to be about 200 thousands Yen/kWe. The power generation cost is estimated to be about 3.8Yen/kWh by the conditions of 90% load factor and 3% discount rate. The economical feasibility of the GTHTR300 is certified. The present study is entrusted from Ministry of Education, Culture, Sports, Science and Technology of Japan.

Development of Control Technology for the HTTR Hydrogen Production System

Japan Atomic Energy Research Institute has performed the research and development of hydrogen production using the high-temperature engineering test reactor (HTTR). One of the key issues for the HTTR hydrogen production system is the development of control technology for stable operation. A thermal load absorber concept using a steam generator installed downstream of a reformer is proposed to mitigate a variation of helium temperature. Thermal-hydraulic analyses for the start-up operation and the suspension of the feed gas supply to the reformer are carried out. These results show that a large variation of the reformer outlet helium temperature takes place because of a change of the feed gas flow rate. However, the steam generator can mitigate the variation of the helium temperature. It is clarified that the HTTR can continue normal operation independently of the feed gas flow rate.

Analysis of sequential charged particle reaction experiments for fusion reactors

Sequential charged particle reactions, that is, reactions induced by secondary charged particles generated due to neutron reactions, may cause non-negligible radioactivity in low activation material. A computer code ACT4, which had been developed to calculate radioactivity, decay heat and gamma ray source for fusion reactors was supplemented an ability to deal with the reactions. Experiments conducted with Fusion Neutronics Source in Japan Atomic Energy Research Institute for the radioactivity by sequential charged particle reactions were analyzed with the newly revised code of ACT4. As the result, the activations via sequential reaction in LiF showed reasonable agreement with experimental data, which means that the ACT4 program will work well. However, the other activations in vanadium and low activation ferritic steel did not. The disagreement must be caused by incorrectness in neutron cross sections, charged particle cross sections, charged particle emission spectra, etc., and they need to be fully reviewed for the detailed and reliable design analysis of fusion reactors.

Overview of research and development activities on fusion nuclear technologies in Japan

Strategy and research and development activities (R&Ds) on fusion nuclear technologies in Japan are reviewed. The fusion program of Japan places a clear stress on energy oriented R&Ds in two areas: those directly to ITER and those for high performance and more challenging options of fusion nuclear technology (FNT) components and systems. Collaboration between Japan Atomic Energy Research Institute (JAERI), universities, National Institute for Fusion Science (NIFS) and industries was strongly encouraged to attain the goal. Recent activities including development of solid and liquid breeding blankets and other FNT issues like PMI, tritium process, fusion safety, inertial fusion and modeling, are summarized, and it is stressed that fusion researchers in Japan concentrate on the development of ITER and eventually for fruition of fusion reactor.

Development and operation of the JAERI superconducting energy recovery linacs

The Japan Atomic Energy Research Institute free-electron laser (JAERI FEL) group at Tokai, Ibaraki, Japan has successfully developed one of the most advanced and newest accelerator technologies named “superconducting energy recovery linacs (ERLs)” and some applications in near future using the ERLs. In the text, the current operation and high power JAERI ERL–FEL 10 kW upgrading program, ERL-light source design studies, prevention of the stainless-steel cold-worked stress-corrosion cracking failures and decommissioning of nuclear power plants in nuclear energy industries were reported and discussed briefly as a typical application of the ERL–FEL.

Upgrade of the 32 m small-angle neutron scattering instrument SANS-U

The small-angle neutron scattering instrument, SANS-U, owned by the Institute for Solid State Physics, The University of Tokyo, has been upgraded. The SANS-U is a 32 m SANS instrument installed in 1991 at the guide hall of the JRR-3M research reactor of the Japan Atomic Energy Research Institute, and has been serving for inter-university cooperative research use since 1993. The major upgrades include (i) replacement of the two-dimensional area detector by a multi-wire type position-sensitive proportional counter, (ii) renewal of the operating system from a VAX and sequencers to an integrated PXI system controlled byLabVIEW-RTsoftware, (iii) a focusing collimation system, and (iv) a variety of accessory equipment. These upgrades provide a wide dynamic range of neutron counting, user-friendly operation and real-time circular averaging of two-dimensional data.

Collisionless reversed magnetic shear trapped electron instability and contribution of sidebands to anomalous transport

By keeping account of the trapped electron ∇B and curvature drifts, it is found that the spatial decay of the collisionless electron drift wave is governed either by the trapped electron response or by the resonant interaction of ions with the sidebands of the primary oscillation. In the former case, pairs of spatially bounded unstable and damped solutions are obtained for negative magnetic shear (ŝ<0) if, as usual, LTe=1∕∂rlnTe<0; there are no bounded solutions if ŝLTe<0. In the latter case, there is either a set of bounded damped solutions if ηi>0 or a set of bounded unstable solutions if ηi<0. The unstable modes have a radiating character and the growth rates are γ∼(2n+1)1+2q2∣ŝ∣∣LNωe*∕qR∣ (n is the Hermite polynomial solution index, q the safety factor, ŝ the magnetic shear parameter, R the major radius, ωe* the electron diamagnetic frequency, LN=1∕∂rlnNe, and ηi=LN∕LTi).The sidebands are responsible for unusually large ratios Qe∕TeΓe, where Qe and Γe are the anomalous electron energy flux and the particle flux. These results may explain the box-type Te profile observed in lower hybrid current drive reversed magnetic shear plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60U Team, Phys. Fluids B 4, 2070 (1992)]. It is finally demonstrated that the ballooning hypothesis generally leads to conflicting requirements: it is thus hardly relevant for the electron drift branch! The “radiating” boundary condition that has formerly been imposed on the slab solution is finally discussed.

EARTH SIMULATOR AND SIMULATION RESEARCH PROGRESS

Earth simulator is a parallel vector super-computer which developed by National Space Development Agency of Japan(NASDA)and Japan Atomic Energy Research Institute(JAERI)and Japan Agency for Marine-Earth Science and Technology(JAMSTEC).Understanding and forecasting high-impact phenomena in the atmosphere and ocean,global warm,crust.The performance of Earth Simulator,birth of the Earth Simulator,research contents of five groups which are Atmosphere and Ocean Simulation Research Group,Solid Earth Simulation Research Group,Multiscale Simulation Research Group,Advanced Perception Research Group and Holistic Simulation Research Group,research projects and collaborations are introduced.At last,usage details details of the Earth Simulator and sustained performance of actual application are introduced.

Inelastic Neutron Scattering from CeOs4Sb12

Inelastic Neutron Scattering from CeOs₄Sb₁₂

Chemical studies on rutherfordium (Rf) at JAERI

SummaryChemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide261Rf has been produced in the reaction248Cm(18O, 5n) at the JAERI tandem accelerator with the production cross section of about 13 nb. On-line anion-exchange experiments on Rf together with the lighter homologues, group-4 elements Zr and Hf, in acidic solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, it has been found that the properties of Rf in HCl and HNO3solutions are quite similar to those of Zr and Hf, definitely confirming that Rf is a member of the group-4 elements. However, we have observed an unexpected chemical behavior of Rf in HF solutions; the fluoride complex formation of Rf is significantly different from those of the homologues. Prospects of extending chemical studies on transactinide elements in the near future at JAERI are briefly considered.

Field Emission-Type Scanning Electron Microscope for Examination of Irradiated Fuels

A field emission-type scanning electron microscope (FE-SEM) for observation of irradiated fuels and materials was installed at the Reactor Fuel Examination Facility at the Japan Atomic Energy Research Institute. A cell with remote-handling systems only for the FE-SEM was made to enable safe manipulation of highly radioactive samples. Some parts of the FE-SEM were modified for the remote handling outside the cell. The energy dispersive spectrometer modified for the samples was also equipped on the FE-SEM to determine element compositions of the observed samples. After the modifications, characterization tests were carried out using deposited gold film and uranium rock samples that were unirradiated. In results of the tests, high-resolution images of those specimens were obtained with high magnification above 10 000. From those results, it was expected that the FE-SEM kept the high performance even after the modifications and would be utilized for radioactive samples.

Case Study on Unexpected Tritium Release Happened in a Ventilated Room of Fusion Reactor

At the Tritium Process Laboratory (TPL) in Japan Atomic Energy Research Institute (JAERI), the three-dimensional “TBEHAVIOR” code has been developed and improved to understand initial tritium behavior and tritium confinement performance in a ventilated room of a fusion reactor in case of tritium leak event. The purpose of this study was mainly focused to; 1) investigate the effect of atmospheric exchange time per hour on the tritium confinement performance in an actual scaled tritium handling room after off-normal tritium release; 2) investigate the effect of atmospheric exchange time per hour on the time necessary for detecting tritium release; 3) investigate the suitable location of exhaust ducts and alarm monitors. The simulated room used in the present analysis is approximately 3000 m3 of tritium handling room (12.00 mW, 29.00 mD and 8.50 mH) with six supply ducts and six exhaust ducts. Atmospheric exchange time per hour is changed as a parameter from 0.67 to 3.33 times per hour.

Alfvén eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges

Rapid frequency sweeping modes observed in reversed magnetic shear (RS) plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60 Team, Phys. Fluids B 4, 2070 (1992)] have been identified as reversed-shear-induced Alfvén eigenmodes (RSAEs), which are ideal magnetohydrodynamic Alfvén eigenmodes (AEs) localized to the region of minimum safety factor, qmin, and are excited by negative-ion-based neutral beam injection. The chirping and subsequent saturation of the mode frequency are consistent with theoretical predictions for the transition from RSAEs to toroidal Alfvén eigenmodes (TAEs). The previously observed rapid frequency sweeping modes in ion cyclotron wave heated plasmas in JT-60U can also be similarly explained. The observed AE amplitude is largest during the transition from RSAEs to TAEs, and fast ion loss is observed when the AE amplitude is largest at this transition. It is preferable to operate outside the transition range of qmin, e.g., 2.4<qmin<2.7 for the n=1AE to avoid substantial fast ion loss in RS plasmas.

The Oxidation Performance Test of Detritiation System under Existence of CO and CO2

To obtain performance data of atmosphere detritiation system at the off normal events such as fire for the safety of ITER, the detritiation experiment was planned and performed at Tritium Process Laboratory (TPL) in Japan Atomic Energy Research Institute (JAERI) using a new scaled detritiation system for the oxidation performance test which can process gas flow rate of ~2.64 m3/hr in circulation through 2m3 tank. The detritiation system consists of two oxidation catalyst beds (473K and 773K) for converting hydrogen isotopes and tritiated methane in compounds to water vapor and a molecular sieve drying absorber for removing water vapor as the usual detritiation system. In this time, the performance of oxidation catalyst bed of the detritiation system for hydrogen and methane under existence of carbon monoxide or carbon dioxide which are produced in the fire was investigated.Basic performance of the detritiation system for hydrogen (1.9%) and methane (1.3%) in air was evaluated under maximum ventilation flow rate (2.64m3/h). Obtained oxidation efficiency was more than 99.99% for hydrogen in the catalyst bed at 473K and more than 99.9% for methane in the 773K one, respectively. It was confirmed that these performances were maintained even under carbon dioxide of up to 20%, carbon monoxide of up to 10% if sufficient oxygen remained in the process gas, and that the existence of carbon monoxide and carbon dioxide at the fire would not influence the performance of the oxidation catalyst bed in the detritiation system.

Design, fabrication and installation of cryogenic target system for 14 MeV neutron irradiation on superconducting magnet materials

A large scale superconducting magnet system is indispensable to realize a fusion reactor and researches on fusion neutron irradiation effects on the magnet materials must be performed continuously and systematically to promote an establishment of reasonable design and fabrication of a fusion reactor. Since pure 14 MeV neutrons are expected to give clear results easily understood in comparison with energy-distributed neutrons, a new cryogenic target system has been installed in Fusion Neutronics Source at Japan Atomic Energy Research Institute under collaboration among Universities, National Institutes and JAERI. The new system has the potential to perform the electrical measurement at cryogenic temperature without warm-up of the samples. This report describes the design and installation of the cryogenic target system for 14 MeV neutron irradiation and some performance test results. The cold target is able to be cooled down within 2 h and there is no temperature rise during a 3 h neutron irradiation.

R&D on a high energy accelerator and a large negative ion source for ITER

R&D pertaining to a 1 MeV accelerator and a large negative ion source has been carried out at the Japan Atomic Energy Research Institute for the ITER neutral beam system. The R&D is, at present, progressing towards: (1) 1 MeV acceleration of H− ion beams at the ITER relevant current density of 200 A m−2 and (2) improvement of uniform negative ion production over wide extraction area in large negative ion sources. Recently, H− ion beams of 1 MeV and 140 mA level have been generated with a substantial beam current density (100 A m−2). In the uniformity study, it was clarified that the electron temperature in the ion extraction region was locally high (>1 eV), which resulted in the destruction of negative ions at a high reaction rate. Interception of fast electrons leaking through a transverse magnetic field called ‘magnetic filter’ has been found to be effective in lowering the local electron temperature, followed by an improvement of negative ion beam profile.

The hydration structure of a Z-DNA hexameric duplex determined by a neutron diffraction technique

In order to reveal the hydration structure of Z-DNA, a neutron diffraction study has been carried out at 1.8 A resolution on a Z-DNA hexamer d(CGCGCG). Neutron diffraction data were collected with the BIX-3 single-crystal diffractometer at the JRR-3 reactor in the Japan Atomic Energy Research Institute (JAERI) using a large crystal (1.6 mm3) obtained from D2O solution. It has been found that almost all the guanine bases have participated in H/D exchange at the C8-H8 group, consistent with the acidic nature of this bond. 44 water molecules were found in the nuclear density maps, of which 29 showed the entire contour of all three atoms (D-O-D). The remaining 15 water molecules had a simple spherical shape, indicating that they were rotationally disordered. An interesting relationship was found between the orientational disorder of the water molecules and their locations. Almost all water molecules in the minor groove were well ordered in the crystal, while 40% of the water molecules in the major groove were rotationally disordered. The hydrogen-bonding networks in the hydration shells have two structural aspects: flexibility and regularity.

A Simulation of the Interaction Among Pressure Wave Propagation, Wall Deformation and Bubble Dynamics in a Mercury Target

Japan Atomic Energy Research Institute (JAERI) is promoting the construction of a mercury target as a neutron source by a nuclear spallation reaction. In the spallation reaction process, high density heat is released and strong pressure wave is generated consequently. It is considered that an erosion of the target wall might be caused due to the cavitation. In fact, some experiments show that fine damage is created on the wall when a strong pressure wave reflects on it. In this paper, a simulation of the interaction among three physical phenomena such as pressure wave propagation, wall deformation and bubble dynamics is carried out in order to investigate the possibility of the cavitation in a mercury target. In particular, we propose a method in which the bubble dynamics model is linked with the so-called weakly coupled method between the fluid model and the solid model.