Preparation for a neutronics experiment using a discharge fusion device and an imaging plate neutron detector

Tritium breeding ratio (TBR) is one of the most important parameters determining the tritium self-sufficiency of a deuterium-tritium fusion reactor. A neutronics experiment is planned to measure the spectral neutron fluences two-dimensionally (2D) using a discharge-type compact fusion neutron source and a neutron imaging plate (NIP), respectively. We report a calibration method for the NIP and optimization of the discharge condition to enhance the neutron production rate. A linear relationship between the neutron fluence in the NIP and photostimulated luminescence (PSL) per area was obtained in the range of the neutron fluence from 10³ to 10⁷ n/cm². A neutron production rate higher than 10⁷ n/s was successfully achieved by the optimized discharge condition. It is shown that a quantitative 2D measurement by the NIP is feasible using the linear relationship and a correlation coefficient on the energy spectrum

Experimental Visualization of Interstitialcy Diffusion of Li Ion in β-Li₂TiO₃

Monoclinic lithium metatitanate, β-Li₂TiO₃, is a member of the Li₂TiO₃ (M = Ti, Mn, Sn, Ru, and/or Ir) series and an important cation conductor for various energy applications such as Li-ion batteries and nuclear fusion reactors. Comprehensive knowledge of the crystal structure is vital to understand the Li-ion diffusion mechanism, and several possibilities were proposed previously. However, the exact crystal structure and Li-ion diffusion paths of β-Li₂TiO₃ are still unclear. Here, the results of a neutron diffraction study of high-purity ⁷Li-enriched β-Li₂TiO₃ are reported. The occupancy factor 0.033(3) and the atomic coordinates of the interstitial Li ion in the Li–O layer are successfully refined by Rietveld analysis of the time-of-flight neutron diffraction data. The three-dimensional network of Li-ion diffusion pathways is visualized by a combined technique of high-temperature neutron-diffraction and maximum-entropy methods. An interstitialcy diffusion mechanism, in which a lithium ion migrates through both the interstitial tetrahedral and lattice octahedral sites, is proposed for the Li₂TiO₃ series

Corrosion characteristics of reduced activation ferritic-martensitic steel EUROFER by Li₂TiO₃ with excess Li

In a solid breeding blanket, ceramic breeder pebbles are in contact with reduced activation ferritic martensitic (RAFM) steel at high temperatures for years and accordingly form a corrosion layer on the blanket structural steel. Present study focuses on corrosion characteristics of EUROFER97 RAFM steel by an advanced breeder material of Li₂TiO₃ with excess Li (initial ratio of Li/Ti = 2.2) at 623, 823, and 1073 K under sweep gas (He + 0.1% H₂) flow. Formation of a thick oxide double layer was found on the surface of the EUROFER plates heated at 823 and 1073 K, while the corrosion layer formed at 673 K was < 1 µm even after 56 days. On the other hand, the changes that appeared on the contacted surface of the breeder pellet were insignificant. The growth of the corrosion layer shows that the corrosion caused by inward migrations mainly of Li and O from the breeder material will have little influence on mechanical property of the blanket structural steel

先進トリチウム増殖材用過定比メタチタン酸リチウムの結晶構造と高温化学特性に関する研究

学位の種別:課程博士University of Tokyo(東京大学

Case report: Neonatal case of intrauterine gastrointestinal bleeding with suspected cow's milk allergy or neonatal transient eosinophilic colitis

The patient was a female newborn. Ultrasonography performed at 35 weeks and 3 days of gestation revealed honeycomb-like dilatation and peri-intestinal strong echo patterns in the gastrointestinal tract. Nonreassuring fetal status was also diagnosed, leading to an emergency Cesarean section. The baby's birth weight was 2,127 g, whereas the Apgar 1 min and 5 min scores were 8 and 9, respectively. The amniotic fluid showed fecal and hematogenous turbidity. After delivery, there was hematogenous intragastric residue and defecation. Thereafter, the bloody intragastric residue and fecal discharge improved. Aggregations of eosinophils in the stool were observed, and gastrointestinal allergy was suspected. Enteral feeding with the hydrolyzed protein formula was initiated and symptoms did not recur. The allergen-specific lymphocyte stimulation test was positive for lactoferrin, and the patient was suspected with neonatal cow's milk allergy or neonatal transient eosinophilic colitis. After her condition stabilized, an oral challenge test was performed using breast milk without dairy products, and the test was negative. Gastrointestinal allergy is rare even in utero, and when gastrointestinal bleeding is suspected in utero, hemorrhagic or surgical gastrointestinal diseases should be ruled out first; however, the possibility of gastrointestinal allergy should also be kept in mind

Evaluation of tritium production rate in a blanket mock-up using a compact fusion neutron source

We report a neutronics study of a blanket mock-up using a discharge-type compact fusion neutron source. Deuterium–deuterium fusion neutrons were irradiated to the mock-ups composed of tritium breeder and neutron reflector/moderator. The tritium production rate (TPR) per source neutron was measured by a single-crystal diamond detector with a 6Li-enriched lithium fluoride film convertor after the calibration process. Despite the low neutron yield, energetic alpha and triton particles via 6Li(n, t)α neutron capture as well as 12C via elastic scattering were successfully detected by the SDD with high signal to noise ratios. The TPRs were experimentally evaluated with errors of 8.4%–8.5% at the 1σ level at the positions with high thermal neutron fluxes where the errors were dominantly introduced by uncertainties in the monitoring of the neutron production rate. The calculated to experimental (C/E) values of TPR were evaluated to be 0.91–1.27 (FENDL-2.1) and 0.94–1.28 (FENDL-3.1). As the neutron source can generate 14 MeV neutrons using a mixed gas of deuterium and tritium, this approach provides more opportunities for blanket neutronics experiments

Evaluation of 3D printed buckyball-shaped cathodes of titanium and stainless-steel for IEC fusion system

An inertial electrostatic confinement (IEC) fusion device accelerates ions, such as deuterium (D) or tritium (T), to produce nuclear fusion and generate neutrons. The IEC's straightforward configuration consists of a concentric spherical transparent cathode at a negative bias surrounded by a grounded spherical anode. The effects of cathode properties on the neutron production rate (NPR) remain, to date, inadequately studied. This study aims to determine the impact of the cathode material on the NPR by investigating fusion reactions on the cathode surface. Two buckyball-shaped cathodes made of stainless steel (SS) and titanium (Ti), both of 5 cm diameter, fabricated by selective laser melting and 3D printing, are used for this investigation. A SS spherical chamber of 25 cm inner diameter is used as an anode in this experiment. A performance evaluation of surface fusion reaction in the IEC using SS and Ti grids is conducted by examining the NPR as a function of the applied voltage and grid currents at different gas pressures. So far, IEC with Ti and SS cathodes achieves NPRs of 2.32 and 1.41 × 10⁷n/s, respectively, at 5.6 kW (70 kV, 80 mA). The normalized NPRs (NPR/I-cathode) from IEC using SS and Ti cathodes are compared. The results demonstrate that fusion reaction occurs on the cathode surface, and fusion increases with the applied voltage. The measured NPR/I-cathode using the Ti cathode is higher than that of the SS cathode by factors of 1.36–1.64 across the 20–70 kV range. Moreover, fusion on the Ti cathode surface enhances the total NPR significantly compared to the SS cathode under the same conditions. The Ti's considerable ability to accumulate D ions and molecules compared with that of SS explains the difference of measured NPR results

Metastatic Patterns of Myxoid/Round Cell Liposarcoma: A Review of a 25-Year Experience

Myxoid/round cell liposarcoma (MRCL), unlike other soft tissue sarcomas, has been associated with unusual pattern of metastasis to extrapulmonary sites. In an attempt to elucidate the clinical features of MRCL with metastatic lesions, 58 cases, from the medical database of Keio University Hospital were used for the evaluation. 47 patients (81%) had no metastases, whereas 11 patients (11%) had metastases during their clinical course. Among the 11 patients with metastatic lesions, 8 patients (73%) had extrapulmonary metastases and 3 patients (27%) had pulmonary metastases. Patients were further divided into three groups; without metastasis, with extrapulmonary metastasis, and with pulmonary metastasis. When the metastatic patterns were stratified according to tumor size, there was statistical significance between the three groups (P = 0.028). The 8 cases with extrapulmonary metastases were all larger than 10 cm. Similarly, histological grading had a significant impact on metastatic patterns (P = 0.027). 3 cases with pulmonary metastatic lesions were all diagnosed as high grade. In conclusion, large size and low histological grade were significantly associated with extrapulmonary metastasis

Comparison of 19-gauge conventional and Franseen needles for the diagnosis of lymphadenopathy and classification of malignant lymphoma using endoscopic ultrasound fine-needle aspiration

Background/Aims Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) using a 19-gauge needle is an efficient sampling method for the diagnosis of lymphadenopathy. This study compared 19-gauge conventional and Franseen needles for the diagnosis of lymphadenopathy and classification of malignant lymphoma (ML). Methods Patient characteristics, number of needle passes, puncture route, sensitivity, specificity, and accuracy of cytology/histology for lymphadenopathy were analyzed in patients diagnosed with lymphadenopathy by EUS-FNA using conventional or Franseen needles. Results Between 2012 and 2022, 146 patients met the inclusion criteria (conventional [n=70] and Franseen [n=76]). The median number of needle passes was significantly lower in the conventional group than in the Franseen group (3 [1–6] vs. 4 [1–6], p=0.023). There were no significant differences in cytological/histological diagnoses between the two groups. For ML, the immunohistochemical evaluation rate, sensitivity of flow cytometry, and cytogenetic assessment were not significantly different in either group. Bleeding as adverse events (AEs) were observed in three patients in the Franseen group. Conclusions Both the 19-gauge conventional and Franseen needles showed high accuracy in lymphadenopathy and ML classification. Considering sufficient tissue collection and the avoidance of AEs, the use of 19-gauge conventional needles seems to be a good option for the diagnosis of lymphadenopathy