Nondestructive and active interrogation system for special nuclear material:proof of principle and initial results

Herein,we employ the threshold energy neutron analysis(TENA)technique to introduce the world's first active interrogation system to detect special nuclear materials(SNMs),including U-235 and Pu-239.The system utilizes a DD neutron generator based on inertial electrostatic confinement(IEC)to interrogate suspicious objects.To detect secondary neutrons produced during fission reactions induced in SNMs,a tensioned metastable fluid detector(TMFD)is employed.The current status of the system's development is reported in this paper,accompanied by the results from experiments conducted to detect 10 g of highly enriched uranium(HEU).Notably,the experimental findings demonstrate a distinct difference in the count rates of measurements with and without HEU.This difference in count rates surpasses two times the standard deviation,indicating a confidence level of more than 96% for identifying the presence of HEU.The paper presents and extensively discusses the proof-of-principle experimental results,along with the system's planned trajectory.

硼中子俘获治疗外阴黑色素瘤和生殖器乳腺外Paget病的疗效

背景与目的尽管目前对生殖器区的黑色素瘤和乳腺外Paget病(extramammary Paget’s disease,EMPD)最常推荐的治疗方法是广泛性手术切除病变,但该方法侵害性极高并可导致功能性和性方面的问题。当扩大局部切除术不可行的情况下,替代疗法已被用于进行局部控制。本研究描述了4例接受硼中子俘获治疗(boron neutron capture therapy,BNCT)的生殖器恶性肿瘤患者。方法 4例患者中包括1例外阴黑色素瘤(vulvar melanoma,VM)和3例生殖器EMPD患者。他们于2005至2014年间在Kyoto大学研究堆接受了对二羟基硼酰苯丙氨酸作为硼携带剂的BNCT治疗。他们接受了介于治愈性肿瘤剂量和可耐受的皮肤/黏膜剂量之间的超热中子束照射。结果所有患者在BNCT治疗后均表现出相似的肿瘤和正常组织反应,并在6个月内达到完全缓解。最严重的正常组织反应前2个月内出现,随后逐渐减弱的中度皮肤糜烂,排尿困难或接触性疼痛持续2个月,完全解决需4个月。结论 BNCT治疗VM和EMPD后局部肿瘤得到完全控制。根据我们的临床经验,我们认为BNCT是治疗生殖器区原发性VM和EMPD的一种有前景的方法。

Evaluation of D（d,n）^3 He reaction neutron source models for BNCT irradiation system design

<正>A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in energies lower than 1.0MeV.The data of energy spectrum and angular distribution were applied to set up the neutron source model for the beam-shaping-assembly(BSA)design of Boron-Neutron-Capture-Therapy(BNCT)using MCNP-4C code. Three cases of D-D neutron source corresponding to incident deuteron energy of 1000,400 and 150 key were inves- tigated.The neutron beam characteristics were compared with the model of a 2.45 MeV mono-energetic and isotropic neutron source using an example BSA designed for BNCT irradiation.The results show significant differences in the neutron beam characteristics,particularly the fast neutron component and fast neutron dose in air,between the non-isotropic neutron source model and the 2.5 MeV mono-euergetic and isotropic neutron source model.

Effects of thermal aging on Fe ion-irradiated Fe–0.6%Cu alloy investigated by positron annihilation

Thermal aging effects on surface of 2.5 Me V Fe ion-irradiated Fe–0.6%Cu alloy were investigated using positron annihilation techniques. The samples were irradiated at 573 K to a dose of 0.1 dpa. Their thermal aging was performed at 573 K for 5, 50 and 100 h. From the results of Doppler broadening measurement, an obvious trough could be seen in near-surface region from the S parameters and inflection point form at S–W curves. This indicates changes in the annihilation mechanism of positrons in surface region after thermal aging. Coincident Doppler broadening indicates that the density of Cu precipitates in the thermal aged samples decreased, due to recovery of the vacancies.

Effect of Tirapazamine and Mild Temperature Hyperthermia on the Recovery from Radiation-Induced Damage in Pimonidazole-Unlabeled Quiescent Tumor Cell Population

The aim in this study is to examine the effect of tirapazamine (TPZ) and mild temperature hyperthermia (MTH) on the repair of radiation-induced damage in pimonidazole-unlabeled quiescent (Q) tumor cells. Labeling of proliferating (P) cells in C57BL/6J mice bearing EL4 tumors was achieved by continuous administration of 5-bromo-2-deoxyuridine (BrdU). Tumors were irradiated with γ-rays at 1 h after the administration of pimonidazole followed by TPZ treatment or MTH. Twenty-four hours later, assessment of the responses of Q and total (= P + Q) cells were based on the frequencies of micronucleation and apoptosis using immunofluorescence staining for BrdU. The response of the pimonidazole-unlabeled tumor cell fractions was assessed by means of apoptosis frequency using immunofluorescence staining for pimonidazole. With γ-rays only, the pimonidazole-unlabeled cell fraction showed significantly enhanced radio-sensitivity compared with the whole cell fraction more remarkably in Q cells than total cells. However, a significantly greater decrease in radio-sensitivity in the pimonidazole-unlabeled than the whole cell fraction, evaluated using a delayed assay, was more clearly observed in Q cells than total cells. Post-irradiation MTH more remarkably repressed the decrease in radio-sensitivity in the Q cell than the total cells. Post-irradiation TPZ administration produced a large radio-sensitizing effect on both total and Q cells, especially on Q cells. On the other hand, in pimonidazole-unlabeled cell fractions in both total and Q cells, TPZ suppressed the reduction in sensitivity due to delayed assay much more efficiently than MTH, whereas no radio-sensitizing effect was produced. Not only through suppressing the recovery from radiation-induced damage but also through radio-sensitizing effect, post-irradiation TPZ administration is very useful for repressing the increase in the difference in radio-sensitivity due to the delayed assay not only between total and Q tumor cells but also between the pimonidazole-unlabeled and the whole cell fractions within the total and Q tumor cells.

Determination of Apparent Formation Constants of Eu(III) with Humic Substances by Ion Selective Liquid Membrane Electrode

This is the novel measurement of the apparent formation constants of trivalent lanthanide with humic substances by potentiometric titration using an ion selective electrode (ISE) consisting of bis(diphenylphosphoryl)methane as an ionophore. The ISE prepared exhibited a Nernstian response to the Eu3+ concentration in the test solutions in the presence of humic acid and fulvic acid. The effect of the solution conditions, including the pH, initial metal and humic substance concentrations, and ionic strength, on the formation constants was examined. The present formation constants were compared with the reported data using solvent extraction method.

Visualization and Measurement of Water Distribution in Through-Plane Direction of Polymer Electrolyte Fuel Cell during Start-Up by Using Neutron Radiography

Water management in a polymer electrolyte fuel cell (PEFC) is a key topic for PEFC operation. A microporous layer (MPL) has been recently used to improve the water flooding in the gas diffusion layer (GDL) around the catalyst layer. However, the mechanisms of this MPL are not completely understood because of the difficulty of measuring the water distribution during operation. To clarify the water-accumulation phenomena with the MPL, visualization and measurement of the water distribution in the through-plane direction of a small fuel cell is carried out by using neutron radiography. The parallelism of the neutron flux is optimized by using a collimator to observe the transient change in the water distributions, and two-dimensional water distributions in the through-plane direction of the PEFC can be obtained every 60 s. The differences in the water accumulation processes in the GDL without and with the MPL under the lands and channels are compared. It is observed that the water accumulation in the GDL under the land is greater than that under the channel during the period of early PEFC operation. Water evacuation from the GDL to the channel mainly occurs around the land corners. Furthermore, one-dimensional water distributions are calculated from the visualized water distributions, and the results without and with the MPL in the cathode are compared. The water thickness in the through-plane direction attains its maximum value around the boundary between the catalyst layer and the GDL without the MPL, whereas it is attained between the MPL and the GDL with the MPL. The maximum water accumulation in the GDL under the land without the MPL is higher than that with the MPL.

Subunit Arrangement of a 2-Ketoisovalerate Ferredoxin Oxidoreductase from Thermococcus profundus Revealed by a Low Resolution X-Ray Analysis

2-ketoisovalerate ferredoxin oxidoreductase (VOR) is a key enzyme in hyperthermophiles catalyzing the coenzyme A-dependent oxidative decarboxylation of aliphatic amino acid-derived 2-keto acids. The enzyme purified under anaerobic conditions from a hyperthermophilic archaeon, Thermococcus profundus, is a hetero-octamer (αβγδ)2 consisting of four different subunits, α = 45 kDa, β = 31 kDa, γ = 22 kDa and δ = 13 kDa, respectively, and it has three [4Fe-4S] clusters per αβγδ-protomer, similar to other ferredoxin oxidoreductases. In the present study, the native enzyme was purified from this strain and crystallized to give rod-like crystals that were suitable for X-ray diffraction experiments. The crystals belonged to space group P41212, with unit-cell parameters a = b = 136.20 ?, c = 221.07 ?. Diffraction images were processed to a resolution of 3.0 ?. The data collected so far indicate the approximate molecular boundaries and a partial main-chain trace of the enzyme.

Boron neutron capture therapy for vulvar melanoma and genital extramammary Paget’s disease with curative responses

Background:Although the most commonly recommended treatment for melanoma and extramammary Paget’s disease(EMPD)of the genital region is wide surgical excision of the lesion,the procedure is highly invasive and can lead to functional and sexual problems.Alternative treatments have been used for local control when wide local exci-sion was not feasible.Here,we describe four patients with genital malignancies who were treated with boron neutron capture therapy(BNCT).Methods:The four patients included one patient with vulvar melanoma(VM)and three with genital EMPD.They underwent BNCT at the Kyoto University Research Reactor between 2005 and 2014 using para-boronophenylalanine as the boron delivery agent.They were irradiated with an epithermal neutron beam between the curative tumor dose and the tolerable skin/mucosal doses.Results:All patients showed similar tumor and normal tissue responses following BNCT and achieved complete responses within 6 months.The most severe normal tissue response was moderate skin erosion during the first 2 months,which diminished gradually thereafter.Dysuria or contact pain persisted for 2 months and resolved com-pletely by 4 months.Conclusions:Treating VM and EMPD with BNCT resulted in complete local tumor control.Based on our clinical expe-rience,we conclude that BNCT is a promising treatment for primary VM and EMPD of the genital region.