Search

Boron neutron capture therapy (BNCT), a binary cancer therapeutic modality, has moved to a new phase since development of accelerator-based neutron sources and establishment of BNCT centers in Finland and Japan. That stimulated efforts for better boron delivery agent development. As liposomes have shown effective boron delivery properties and sufficient tumor retention, fluorescent liposome labelling may serve as a rapid method to study initial ability of newly synthesized liposomes to be captured by tumor cells prior to experiments on boron accumulation and neutron irradiation. In this work, we studied the accumulation and biodistribution of pegylated liposomes with encapsulated borocaptate (BSH) and a fluorescent label (Nile Red) in U87 (human glioblastoma), SW-620 (human colon carcinoma), SK-MEL-28 (human melanoma), FetMSC (mesenchymal human embryo stem cells), and EMBR (primary embryocytes) cell lines as well as an orthotopic xenograft model of U87 glioma in SCID mice. Results indicate that fluorescent microscopy is effective at determining the intracellular localization of the liposomes using a fluorescent label. The synthesized, pegylated liposomes showed higher accumulation in tumors compared to normal cells, with characteristic concentration peaks in SW-620 and U87 cell lines, and provided in vivo tumor selectivity with several-fold higher tumor tissue fluorescence at the 6-h timepoint. [ABSTRACT FROM AUTHOR]

For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer 4He2* are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + 3He → 3T + p. This reaction is induced by neutron irradiation of the 3He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (JPARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These 4He2* clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the 4He2* clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium. [ABSTRACT FROM AUTHOR]

In this paper we report results from a neutron irradiation campaign of Ultra-Fast Silicon Detectors (UFSD) with fluences of 1e14, 3e14, 6e14, 1e15, 3e15 and 6e15 neq/cm2. The UFSD used in this study are circular 50 μ m thick Low-Gain Avalanche Detectors (LGAD), with a 1.0 mm diameter active area. Hamamatsu Photonics (HPK), Japan, produced the UFSD with pre-irradiation internal gain in the range 5–70 depending on the bias voltage. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr β -source. The leakage current, internal gain and the timing resolution were measured as a function of bias voltage at −20 °C and −30 °C. The timing resolution of each device under test was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction discriminator (CFD) method for both. The dependence of the gain upon the irradiation fluence is consistent with the acceptor removal mechanism; at −20 °C the highest gain decreases from 70 before radiation to 2 after a fluence of 6e15 n/cm2. Consequently, the timing resolution was found to deteriorate from 20 ps to 50 ps. The results indicate that the most accurate time resolution is obtained varying with fluence the CFD value used to determine the time of arrival, from 0.1 for pre-irradiated sensors to 0.6 at the highest fluence. Key changes to the pulse shape induced by irradiation, i.e. (i) the contribution of charge multiplication not limited to the gain layer zone, (ii) the shortening of the rise time and (iii) the reduced pulse height, were compared with the WF2 simulation program and were found to be in agreement. [ABSTRACT FROM AUTHOR]

Abstract We report results from the testing of 35 μ m thick Ultra-Fast Silicon Detectors (UFSD) produced by Hamamatsu Photonics (HPK), Japan and the comparison of these new results to data reported in a previous paper on 50 μ m thick UFSD produced by HPK. The 35 μ m thick sensors were irradiated with neutrons to fluences of 1 ⋅ 10 14 , 1 ⋅ 10 15 , 3 ⋅ 10 15 , 6 ⋅ 10 15 neq/cm 2. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr β -source. The leakage current, capacitance, internal gain and the timing resolution were measured as a function of bias voltage at −20 °C and −27 °C. The timing resolution was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction discrimination method for both devices. Within the fluence range measured, 35 μ m thick UFSD present advantages in timing accuracy, bias voltage and power consumption. [ABSTRACT FROM AUTHOR]

• Dogleg type beam transport line design for preventing the contamination of the superconducting linac system from the free surface liquid metal target system. • Moderate pressure gradient design to establish a vacuum system for satisfying the different required pressure. • Quantitative estimation of the reduction of the contamination for the newly designed dogleg beam line. The Advanced Fusion Neutron Source (A-FNS) project is progressing at the QST Rokkasho institute, Japan. The A-FNS will conduct fusion neutron irradiation tests of materials for a fusion demonstration reactor (DEMO reactor). For these tests a high intensity deuteron beam accelerator is used to produce a high neutron flux with the neutron energies around 14 MeV. The accelerator system accelerates a deuteron beam to a beam energy of 40 MeV, guides the beam towards a liquid lithium target and shapes the uniform beam at the Li target using a magnet system. Two of the main considerations for the A-FNS high energy beam transport (HEBT) design are protection of the Superconducting Radio-Frequency linear accelerator (SRF) and vacuum system design for the interface of the HEBT and the target system. For the A-FNS, back streaming of Li vapor from the windowless free surface of the Li target is a concern. In addition, widely different vacuum pressure must be maintained between the accelerator system and the target system. This paper shows the detailed design of the A-FNS HEBT section regarding these considerations. [ABSTRACT FROM AUTHOR]

This paper addresses influence of two different temperature profiles during startup periods in the Japan Materials Testing Reactor and a boiling water reactor upon microstructural evolution and mechanical properties of austenitic stainless steel irradiated with neutrons to about 1 dpa and 3 dpa. One of the temperature profiles was that the specimens experienced neutron irradiation in both reactors, under which the irradiation temperature transiently increased to 290 °C from room temperature with increasing reactor power during reactor startup periods. Another was that the specimens were pre-heated to about 150 °C prior to the irradiation to suppress the transient temperature increase. Tensile tests at 290 °C and Vickers hardness tests at room temperature were carried out, and their microstructures were observed by FEG-TEM. Difference of the temperature profiles was observed obviously in interstitial cluster formation, in particular, growth of Frank loops. Although influence of neutron irradiation involving transient temperature increase to 290 °C from room temperature on the yield strength and the Vickers hardness is buried in the trend curves of existing data, the influence was also found certainly in increment of in yield strength, existence of modest yield drop, and loss of strain hardening capacity and ductility. As a result, Frank loops, which were observed in austenitic stainless steel irradiated at doses of 1 dpa or more, seemed to have important implications regarding the interpretation of not irradiation hardening, but deformation of the austenitic stainless steel. [ABSTRACT FROM AUTHOR]

The dose response of embryos of the zebrafish, Danio rerio , irradiated at 5 h post fertilization (hpf) by 2-MeV neutrons with ≤100 mGy was determined. The neutron irradiations were made at the Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) facility in the National Institute of Radiological Sciences (NIRS), Chiba, Japan. A total of 10 neutron doses ranging from 0.6 to 100 mGy were employed (with a gamma-ray contribution of 14% to the total dose), and the biological effects were studied through quantification of apoptosis at 25 hpf. The responses for neutron doses of 10, 20, 25, and 50 mGy approximately fitted on a straight line, while those for neutron doses of 0.6, 1 and 2.5 mGy exhibited neutron hormetic effects. As such, hormetic responses were generically developed by different kinds of ionizing radiations with different linear energy transfer (LET) values. The responses for neutron doses of 70 and 100 mGy were significantly below the lower 95% confidence band of the best-fit line, which strongly suggested the presence of gamma-ray hormesis. [ABSTRACT FROM AUTHOR]

Abstract: The effect of neutron-irradiation damage has been mainly simulated using high-energy ion bombardment. A recent MIT report (PSFC/RR-10-4, An assessment of the current data affecting tritium retention and its use to project towards T retention in ITER, Lipschultz et al., 2010) summarizes the observations from high-energy ion bombardment studies and illustrates the saturation trend in deuterium concentration due to damage from ion irradiation in tungsten and molybdenum above 1 displacement per atom (dpa). While this prior database of results is quite valuable for understanding the behavior of hydrogen isotopes in plasma facing components (PFCs), it does not encompass the full range of effects that must be considered in a practical fusion environment due to short penetration depth, damage gradient, high damage rate, and high primary knock-on atom (PKA) energy spectrum of the ion bombardment. In addition, neutrons change the elemental composition via transmutations, and create a high radiation environment inside PFCs, which influences the behavior of hydrogen isotope in PFCs, suggesting the utilization of fission reactors is necessary for neutron-irradiation. Under the framework of the US–Japan TITAN program, tungsten samples (99.99at.% purity from A.L.M.T. Co.) were irradiated by fission neutrons in the High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL), at 50 and 300°C to 0.025, 0.3, and 2.4dpa, and the investigation of deuterium retention in neutron-irradiated tungsten was performed in the Tritium Plasma Experiment (TPE), the unique high-flux linear plasma facility that can handle tritium, beryllium and activated materials. This paper reports the recent results from the comparison of ion-damaged tungsten via various ion species (2.8MeV Fe2+, 20MeV W2+, and 700keV H−) with that from neutron-irradiated tungsten to identify the similarities and differences among them. [Copyright &y& Elsevier]

Abstract: IFMIF is a major installation in the fusion programme to irradiate and characterize the fusion materials, under intense neutron field, necessary for contributing to the development of DEMO and the future fusion Power Plants. The Engineering Validation and Engineering Design Activities, launched mid 2007 in the framework of the Broader Approach agreement between Euratom and Japan, comprise four sub-projects: engineering design of IFMIF, accelerator prototype validation, liquid lithium loop validation, and irradiation test modules validation. After two years, many modifications have been brought to the former conceptual design, the most important ones being the change of technology for the high energy part of the accelerator, a totally new design for the Test Cell, new design of the lithium target assembly and the high flux test module with vertical setup. These modifications and other design improvements, and the general status of the project are overviewed. [Copyright &y& Elsevier]

Abstract: The Japan Materials Testing Reactor (JMTR) of the Japan Atomic Energy Agency is a testing reactor for various neutron irradiation tests on nuclear fuels and materials, as well as for radioisotope production. The operation of JMTR stopped temporarily in August 2006 for refurbishment and improvement. The renewed JMTR will resume operation in Japanese fiscal year 2011. The renewal of aged reactor components, the preparation of new irradiation facilities, and the development of irradiation technologies have been carried out for the resumption of the new JMTR. The new JMTR with the new irradiation facilities and the irradiation technologies will be utilized for the research and development of fission and fusion reactor fuels and materials. This paper describes the present status of the refurbishment and the irradiation technologies focused on instrumentation such as the multi-paired thermocouple which is applicable to irradiation temperature control and a ceramic oxygen sensor in JMTR. [Copyright &y& Elsevier]

Abstract: The “analytical” PYCASSO (PYrocarbon irradiation for Creep and Swelling/Shrinkage of Objects) irradiations focus on determining the effects of neutron irradiation in the temperature range of 900–1100°C, excluding effects due to the presence of fuel, such as pressurization or chemical attack by fission products. These irradiations can therefore be considered separate effect tests, where only the influence of neutron fluence and temperature on coatings and coating combinations is investigated. For this purpose dedicated particles have been manufactured consisting of surrogate kernels (ZrO2 and Al2O3) with different types of PyC/SiC/ZrC coatings and coating combinations. All specimens delivered have been extensively characterized, such that even potentially small changes due to the irradiation in dimensions, microstructure and density can be determined accurately after irradiation. Partners involved in this irradiation are CEA (France), JAEA (Japan) and KAERI (South Korea). The PYCASSO irradiations take place in the High Flux Reactor (HFR) in Petten, and are coordinated by NRG (The Netherlands). The partnership for PYCASSO was initiated by the RAPHAEL (V)HTR European 6th Framework Program and is integrated in the Generation IV International Forum VHTR Fuel and Fuel Cycle project. [ABSTRACT FROM AUTHOR]

Abstract: The current material design of the International fusion materials irradiation facility (IFMIF) back-plate in Japan consists of an austenitic stainless steel type-316L and a RAF/M steel type-F82H. The 316L and F82H are welded together. The 316L region of the back-plate is also welded to the target assembly made of 316L. The back-plate operates under a severe neutron irradiation condition (50dpa/year). Therefore, it is important to perform metallurgical and mechanical tests for these welds in engineering design of the IFMIF. The F82H/316L weld joint with a filler metal type-Y309 was fabricated using TIG-welding method, followed by PWHT at 1013K for 1h. The 316L/316L weld joint was fabricated using YAG-laser welding method. The F82H/316L TIG-weld was found to be satisfactory. However, although the 316L/316L YAG-weld showed no harmful defect, the hardness was somewhat lower in the weld metal. Rupture occurred in the weld metal, and strength and elongation decreased somewhat. Furthermore, small dimples with several large voids were also visible in the fracture surface. [Copyright &y& Elsevier]

Abstract: A small-sized motor with a resistance to neutron and gamma-ray radiation was developed. This motor was rotating normally at a gamma-ray dose of 7×108 Gy, a fast neutron (E >1MeV) fluence of 2×1021 m−2 and a thermal neutron (E <0.683eV) fluence of 4×1022 m−2. The gamma-ray dose for this motor was about 700 times as high as the specification of a commercial motor. Much progress in radiation resistance was attained by using radiation-proof materials without organic lubricant. It became clear that this small-sized motor is able to be used for in-pile tests of a fusion blanket using the Japan Materials Testing Reactor (JMTR). [Copyright &y& Elsevier]

Tungsten (W) based materials for fusion reactor applications have been developed in Japan for the last decade to improve thermo-mechanical properties and tolerance with respect to neutron-irradiation effects. Potassium (K) doping for dispersion strengthening and alloying by rhenium (Re) for solid solute softening and strengthening were applied to W fabricated by powder metallurgy. Thereby modified W materials, e.g. K-doped W and K-doped W-3%Re, demonstrated a higher recrystallization temperature threshold, an increase in strength and ductility, and a reduction in ductile-to-brittle transition temperature (DBTT) compared to pure W in the non-irradiated state. Embrittlement caused by displacement damage and its amplification due to solid transmutation products is expected to be an intrinsic issue of W based materials under neutron irradiation environment inherent to future fusion reactors. In this paper, the effect of K-doping and alloying by Re on the neutron-irradiation-induced embrittlement of W was investigated at neutron fluence causing a considerable amount of solid transmutation products. [ABSTRACT FROM AUTHOR]

Provides information on the dose-response of survivors exposed to neutron irradiation after the Hiroshima and Nagasaki bombing in Japan, based on data collected in 1965. Interpretation of epidemiological data on the occurrence and death rates for various kinds of cancer in 1965; Estimates of the A-bomb dosimetries based on T-65 into turmoil; Evaluation of radiation risk estimates.

There remain some drawbacks of mechanical properties of W materials as a plasma facing material (PFM) for fusion reactor divertors, which are low temperature brittleness, high ductile-to-brittle transition temperature (DBTT), and recrystallization-induced embrittlement. To solve these issues, development of W materials with improved thermo-mechanical properties, neutron irradiation tolerance, and possibility of mass-production with microstructural uniformity has been advanced for the last decade under the collaboration R&D by universities in Japan. In this paper, the effects of grain refining, K-doping, dispersion strengthening by La 2 O 3 particles, and alloying by Re are discussed from the viewpoints of both short- and long-term material properties and phenomena, including effects of neutron irradiation and high heat loads, which should be considered under the actual fusion reactor environments. Through this R&D, K-doping and Re-addition showed several positive effects. Among the materials developed in this R&D, K-doped W-3%Re hot-rolled plate could be a better solution for PFM, which demonstrated superior properties from several perspectives. However, materials alloyed by Re have an intrinsic concern of higher irradiation hardening caused by neutron irradiation up to higher doses. Therefore, it is pointed out that investigations of thermo-mechanical properties under higher dose neutron irradiation are significantly required to realize long-term structural reliability and lifetime of fusion reactors. [ABSTRACT FROM AUTHOR]

• A variety of test modules for DEMO and neutron application are planned in A-FNS. • Conceptual design of the blanket nuclear property test module was reported. • Conceptual design of the diagnostic and control device test module was reported. • Concept of the radio-isotope production module was reported. In the conceptual design activity of advanced fusion neutron source A-FNS, a variety of test modules for fusion DEMO reactor are planned. In these modules, progresses of design activities on Blanket Nuclear Property Test Module (BNPTM) and Diagnostic and Control Device Test Module (DCDTM) were reported. The BNPTM is a module in order to evaluate accuracies of nuclear analyses of the DEMO blanket such as tritium production rate. The influences of the cooling water and test cell wall were evaluated in order to decide its design. The DCDTM is one to achieve irradiation data of functional materials on diagnostic and control devices such as mirror and window. It was clarified from its nuclear analysis that the neutron fluence obtained in the DCDTM was enough to investigate the accumulated irradiation effects on the materials. In addition to the irradiation tests on the fusion reactor materials, various neutron applications are planned at A-FNS. One of the applications is medical isotope production. We clarified that enough amount of the medical isotope molybdenum-99 could be produced in comparison with the demand in Japan by using Radio-Isotope Production Module (RIPM). The RIPM affects little influence on the fusion reactor material irradiation tests. [ABSTRACT FROM AUTHOR]

Two hundred and twenty-five papers relevant to fusion technology and engineering were presented at the 27th IAEA Fusion Energy Conference. The ITER project has reached 57.4% of the total construction work scope through to first plasma. Construction of ITER is indeed progressing at full speed, with some ITER components having already been manufactured, such as the toroidal field coil structures and the gyrotrons of the electron cyclotron heating and current drive system, as a result of decades of technological development. Construction of JT-60SA and WEST is also progressing on schedule to support ITER in various engineering and physics aspects. The EU and Japan are advancing with their pre-conceptual designs for DEMO, and the experience and lessons learned from ITER are already being applied to both designs. China reported on the status of the China Fusion Engineering Test Reactor engineering design. One of the technical issues evident from these DEMO designs is the interfacing of the plasma-facing, in-vessel components with plasmas. Advanced plasma-facing elements having liquid metals and an advanced in situ boron coating technology were applied to existing fusion reactors, the results of which were reported at this conference. It was also reported that commissioning of the injector for the International Fusion Materials Irradiation Facility engineering validation and engineering design activities (IFMIF/EVEDA) project has been completed and testing of the Radio Frequency Quadrupole accelerator has begun. Europe and Japan presented their plans to construct neutron irradiation test facilities: the DEMO-Oriented Neutron Source (DONES) and Advanced Fusion Neutron Source (A-FNS), respectively. A new strategy based on a probability-based design method was proposed to mitigate the difficulty of defining the allowable limit for irradiation-induced degradation with limited empirical evidence. [ABSTRACT FROM AUTHOR]

We installed a source for ultracold neutrons at a new, dedicated spallation target at TRIUMF. The source was originally developed in Japan and uses a superfluid-helium converter cooled to 0.9K. During an extensive test campaign in November 2017, we extracted up to 325000 ultracold neutrons after a one-minute irradiation of the target, over three times more than previously achieved with this source. The corresponding ultracold-neutron density in the whole production and guide volume is 5.3cm-3. The storage lifetime of ultracold neutrons in the source was initially 37 s and dropped to 24 s during the 18 days of operation. During continuous irradiation of the spallation target, we were able to detect a sustained ultracold-neutron rate of up to 1500s-1. Simulations of UCN production, UCN transport, temperature-dependent UCN yield, and temperature-dependent storage lifetime show excellent agreement with the experimental data and confirm that the ultracold-neutron-upscattering rate in superfluid helium is proportional to T7. [ABSTRACT FROM AUTHOR]

Abstract: Weld specimens of the reference low activation vanadium alloy, NIFS-HEAT-2, were irradiated up to a neutron fluence of 1.5×1025 nm−2 (E >0.1MeV) (1.2dpa) at 670K and 1.3×1026 nm−2 (5.3dpa) at 720K in the JOYO reactor in Japan. The base metal exhibited superior irradiation resistance with the ductile-to-brittle transition temperature (DBTT) much lower than room temperature (RT) for both irradiation conditions. The weld metal kept the DBTT below RT after the 1.2dpa irradiation; however, it showed enhanced irradiation embrittlement with much higher DBTT than RT after the 5.3dpa irradiation. The high DBTT for the weld metal was effectively recovered by a post-irradiation annealing at 873K for 1h. Mechanisms of the irradiation embrittlement and its recovery are discussed, based on characterization of the radiation defects and irradiation-induced precipitation. [Copyright &y& Elsevier]

Abstract: With the Japan–US joint research project Tritium, Irradiations, and Thermofluids for America and Nippon (TITAN), an initial set of tungsten samples (99.99% purity, A.L.M.T. Co.) were irradiated by high flux neutrons at 323K to 0.025dpa in High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). Subsequently, one of the neutron-irradiated tungsten samples was exposed to a high-flux deuterium plasma (ion flux: 5×1021 m−2 s−1, ion fluence: 4×1025 m−2) in the Tritium Plasma Experiment (TPE) at Idaho National Laboratory (INL). The deuterium retention in the neutron-irradiated tungsten was 40% higher in comparison to the unirradiated tungsten. The observed broad desorption spectrum from neutron-irradiated tungsten and associated TMAP modeling of the deuterium release suggest that trapping occurs in the bulk material at more than three different energy sites. [Copyright &y& Elsevier]