Vol.27,

Due to the interesting properties of Hafnium diboride (HfB2) as a ceramic, it has drawn considerable attention from several researchers. To understand the radiation properties of HfB2 that may be used in the nuclear industry, the interaction of this composite under neutron irradiation was studied. It is obvious that, because HfB2 has Boron, this composite has the potential to absorb neutrons particularly in the range of thermal energy. The ¹⁰B (n, α) ⁷Li interaction is dominant among other interactions that produce alpha particles. The results revealed that alpha particles have a high fluctuation diagram following a saw-tooth spectrum, for thermal neutron energy which has to be carefully analyzed. If HfB2 intended to be used in fusion facilities, for example; in fusion reactors, its interaction with high neutrons (14 MeV) should be studied. The results for this case showed that, in the wide range of alpha energy, the amount of alpha particle is almost constant so this continuum spectrum is almost flat and there is just a small peak at 2.31 MeV that is belong to the very famous interaction (¹⁰B (n, α) ⁷Li)..

327

There are few reports with respect to the details of acute effects (during and following RT) of ionizing radiation in liver tissue in epidemiology, pathology, physiology and imageology. Therefore, this study was undertaken to assess the diagnostic value of 2-[¹⁸F]-fluoro-2-deoxy-D-glucose positron emission tomography with computed tomography ([¹⁸F]-FDG-PET/CT) in the detection of acute radiation toxicity in normal liver using Tibet minipigs as a model. Thirty-six male Tibetan minipigs were randomly divided into six groups (n = 6). The irradiation groups were treated with a single dose of 2, 5, 8, 11 and 14 Gy total body irradiation using an 8-MV X-ray linac, at dose rate of 255 cGy/min. The control group was not irradiated. The pigs were evaluated with[¹⁸F]-FDG-PET/CT, and their alanine aminotransferase (AST), aspartate aminotransferase (ALT) activity and the ratio of ALT/AST, INRatio, bilirubin were measured on Day 7 post-TBI. All pigs were sacrificed on Day 7 post-TBI to collect liver tissues for pathological examination. The results showed that liver standardized uptake value (SUV) increased with the dose from 2 Gy to 11 Gy, and decreased suddenly at 14 Gy. HAI score showed a radiation dose-dependent increase in of 2 Gy–11 Gy, and was positively correlated with SUV (p<0.05). However, HAI score showed no correlation with liver function. Therefore, we concluded that[¹⁸F]-FDG-PET/CT has the potential to assess acute radiation-induced hepatic injury on early stage.

512

La_(1-x)Mg_xNi_4.25Al_0.75 (x=0.0, 0.1, 0.2, 0.3) alloys for tritium storage were prepared by a method of electromagnetic induction melting. The crystal structure and hydrogen storage performance of the as-cast alloys were investigated. The results showed that a single phase of LaNi₄Al was in the alloys with x=0.0 and 0.1 and that LaNi₄Al and second phases of (La,Mg)Ni₃ and AlNi₃ were in the alloys with x=0.2 and 0.3. On the other hand, the plateau pressures of P-C isotherms of the alloys were increased with the rise of the x value from 0.2 to 0.3 and the hydrogen storage capacity was obviously degraded simultaneously. It was found that the alloy had faster absorption kinetics as the proportion of Mg increased from 0.1 to 0.3.

446

^99mTc-BnAO, as a nonnitroaromatic hypoxia marker, is the subject of intensive research in recent years. In this study, a butene amine oxime-nitrotriazole (BnAO-NT) was synthesized and radiolabeled with ^99mTc in high yield. Cellular uptakes of ^99mTc-BnAO-NT and ^99mTc-BnAO were tested using murine sarcoma S180 and hepatoma H22 cell lines. The highest hypoxic cellular uptake of ^99mTc-BnAO-NT was 27.11±0.73% and 14.85±0.83% for the S180 and H22 cell lines, respectively, whereas the normoxic cellular uptake of the complex was about 4%~8% for both cell lines. For ^99mTc-BnAO, the highest hypoxic cellular uptake was 30.79±0.44% and 9.66±1.20% for the S180 and H22 cell lines, respectively, while the normoxic cellular uptake was about 5% for both cell lines. Both ^99mTc-BnAO-NT and ^99mTc-BnAO complexes showed hypoxic/normoxic differentials in the two cell lines, but the results were more significant for the S180 cell line. The in vitro results suggested that S180 may be better than H22 cell line in hypoxic biological evaluation of BnAO complexes. The biodistribution study was tested using a S180 tumor model. The complex ^99mTc-BnAO-NT showed a selective enrichment in tumor tissues: at 4 h, the tumor-to-muscle ratio was 3.79±0.98 and the tumor-to-blood ratio was 2.31±0.34. Compared with the results of ^99mTc-BnAO, the latter was at the same level. In vitro and in vivo studies demonstrated that ^99mTc-BnAO-NT could be a hypoxia-sensitive radiotracer for monitoring hypoxic regions in a sarcoma S180 tumor.

318

Potted soybean plants were exposed to evaporated HTO for 1h inside an exposure box at two different growth stage (flowering and podding stage, filling stage) during nighttime and daytime. The concentration of tissue-free water tritium (TFWT) and organically-bound tritium (OBT) in leaves and beans were measured at the end of the exposure. The results indicated that the quasi-equilibrium between the TFWT concentrations in the soybean leaves and the HTO concentration of the ambient air moisturerequired more than 1 h to be reached. The relative TFWT concentrations in the nighttime represent about 1/2~2/3 of the concentrations obtained in the day in the leaves compared to about 1/2~4/3 in the beans. The relative OBT concentrations under night conditions were about 2/5~1/2 of those under day conditions in the leaves, contrary to 1/2~7/10 for the beans. By developing tritium concentration assessment model with a short-term release of atmospheric HTO, we comprehensively considered the plant growth stage and the environmental conditions.

354

A novel magnetic chitosan bead cross-linked with glutaraldehyde was prepared, characterized and applied for Cs(I) removal from aqueous solution. Characteristics and mechanism of Cs(I) removal were investigated. The equilibrium data of Cs(I) adsorption by magnetic chitosan beads were fitted using the Langmuir, Freundlich, Tempkin, Redlich-Peterson(R-P), Slips and Dubini-Radushkevich (D-R) models. The maximum adsorption capacity was estimated at 3.86 mg/g from the Langmuir isotherm. FTIR study revealed that N atom was mainly involved in Cs(I) sorption by magnetic chitosan. The magnetic chitosan is a promising adsorbing material for treating Cs(I)-containing radioactive wastewater.

350

This paper presents findings on the sliding-mode controller for a nuclear reactor. One of the important operations in nuclear power plants is load-following. In this paper, a sliding mode control system which is a robust nonlinear controller is designed to control the Pressurized-Water Reactor (PWR) power. The reactor core is simulated based on the point kinetics equations and six delayed neutron groups. Considering neutron absorber poisons and regarding the limitations of the xenon concentration measurement, a sliding mode observer is designed to estimate its value and finally a sliding mode control based on the sliding mode observer is presented to control the core power of reactor. The stability analysis is given by means Lyapunov approach, thus the control system is guaranteed to be stable within a large range. The employed method is easy to implement in practical applications and moreover, the sliding mode control exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed observer based controller in terms of performance, robustness and stability.

332

Pebble bed reactors enable the circulation of pebble fuel elements when the reactors are in operation. This unique design helps to optimize the burnup and power distribution, reduce the excessive reactivity of the reactor, and provides a mean to identify and segregate damaged fuel elements during the operation. The movement of the pebbles in the core, or the kinematics of the pebble bed, significantly affect the above features and are not fully understood. We designed and built a detection system that can measure 3-axis acceleration, 3-axis angular velocity, 3-axis rotation angles, and vibration and temperature of multiple pebbles anywhere in the pebble bed. This system uses pebble-shaped detectors that can flow with other pebbles and does not disturb the pebble movement. We used new technologies to enable instant response, precise measurement and simultaneous collection of data from a large number of detectors. Our tests show that the detection system has a negligible zero drift and the accuracy is better than the designed value. The residence time of the pebbles in a moving pebble bed was also measured using the system.

417

An improvement for application of Dancoff factor is developed. It combines Stamm’ler’s two-term method for resonance integral calculation with neutron current method for Dancoff factor calculation. Stamm’ler’s formulation, which is originally derived for the infinite lattice geometry, can be easily revised to contain the Dancoff factor explicitly. While the neutron current method can easily calculate the Dancoff factor for general irregular assembly geometry. For the resonance interference effects, the resonance interference factor (RIF) table is built in pairs of nuclides, only for the interference between ²³⁸U and other resonance nuclides, spanning over a range of background cross-section and number density ratio of the pairing nuclides. A series of verification calculations have been carried out for problems of infinite lattice and single assembly geometry, with two or multiple resonance absorbers. For these verification calculations, our improvement on Dancoff factor application and resonance interference give good results.

336

Irradiation tests of tungsten surface were performed with He and He/Ar plasma generated by microwave electron cyclotron resonance (ECR). Thickness loss was used as the erosion rate of tungsten surface under the plasma irradiation. The results revealed that the thickness loss increased linearly with negative bias. SEM images proved that the addition of Ar apparently increased the plasma erosion. The thickness loss increased sharply with the Ar fraction of Ar/He mixture when it was less than 20%, where the increasing slope of thickness loss lowered down gradually.

341

The Institute of High Energy Physics, Chinese Academy of Sciences have designed a new type of photomultiplier tube (PMT) based on microchannel plates (MCPs) with large-area photocathode, known as large-area microchannel plate photomultiplier tube (MCP-PMT). The aging characteristics of the large area MCP-PMTs are different from dynode PMTs and small proximity-focus MCP-PMT. In this work, a prototype large area MCP-PMT was aged by operating with nearly 1000 photoelectrons per pulse for three months, and aging process of the MCP-PMT was discussed based on the aging curve.

490

The growth, activation and deposition of corrosion products are the primary sources of radiation buildup on the surface of out-of-core piping in nuclear power plants. The buildup of radiation can have negative effects on performance of the facility and cause harm to staff during maintenance outages for refueling. In this paper, we report on the crystalline and amorphous structures of corrosion products sampled in the boiling water reactors in nuclear power plants of Kuo-Sheng, and identified using an acid dissolving technique. X-ray diffraction, scanning electron microprobe and inductively coupled plasma-atomic emission spectroscopy were used to analyze the samples. The results indicate that the quantity of amorphous iron oxide at inlet of the condensate demineralizer in Unit 2 is higher than that in Unit 1. The proportion of crystalline to amorphous corrosion products can affect the efficiency of removal. Thus, these results can be used to explain the difference in removal efficiency of condensate demineralizers in different units. Moreover, this study observed iron oxide structures with various properties that developed in different operational periods. It is probable that the higher proportion of amorphous structures with a smaller particle size would reduce efficiency in the removal of condensate demineralization in Unit 2.

407

The fluoride salt-cooled high-temperature reactor (FHR) uses molten FLiBe salt as the coolant, which introduces a corrosive effect on the alloy-N structure material. Fission neutrons activate the corroded alloy-N, along with alloy-N structures inside the reactor vessel. The activation products of the alloy-N have a big impact on radiation protection during operation, maintenance, and decommissioning of the reactor. We have constructed a SCALE 6.1 model for the core of a typical 10 MW_th FHR and analyzed the activity of each constituent of the irradiated alloy-N. The results show that the activity is predominantly due to short-lived ²⁸Al, ^60mCo, ⁵⁶Mn, ⁵¹Ti, and ⁵²V, as well as long-lived ⁶⁰Co, ⁵¹Cr, ⁵⁵Fe, ⁵⁹Fe, and ⁵⁴Mn. Furthermore, because of their relatively long half-life and high-energy γ-rays emissions, ⁶⁰Co and ⁵⁴Mn are the major contributors to the radiation source terms introduced by alloy-N activation. The yield of ⁶⁰Co and ⁵⁴Mn per unit mass of alloy-N under the current core design is 5.58×10⁵Bq∙MWd^-1∙g^-1 and 1.55×10³Bq∙MWd^-1∙g^-1, respectively. The results of this paper, combined with future corrosion studies, may provide a basis for evaluating long-term radiation source terms of the primary loop salt and components.

387

Corrosion behavior of AA2037 T8 Al alloy in a 1 M NaOH aqueous solution was investigated using slow positron beam, together with microscopy techniques and electrochemical tests. The alloy was homogenized at 510℃ for 2 hours and 30 seconds, respectively, before final peak-ageing, so that one Sample A had more dispersoids than Sample B after homogenization. It was found that S parameter of the Doppler-broadened annihilation was significantly decreased near the surface in both samples in the alkaline solution. With increasing the dissolution time, Sample A showed a slower decrease rate than Sample B, which might imply that the pre-existence of more dispersoids might hinder the corrosion process in Sample A. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations found that the surfaces of both samples were uniformly thinned due to intense chemical dissolution by the attack of OH^-. With increasing the dissolution time, Sample B was corroded more substantially and produced more and larger pits in a short dissolution time than Sample A. Furthermore, polarization curves showed that Sample A had a lower corrosion current and corrosion rate than Sample B, which revealed that the presence of the dispersoids was responsible for the better corrosion resistance in the alloy.

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367

Mercury ions have been considered highly toxic to human health. What would be great is to develop the ionic probes without any toxicities themselves. Here we report a friendly, highly sensitive mercury (II) ionic probe, water-soluble photoluminescence carbon dots which were synthesized by simply hydrothermal treatment of fresh cherry tomatoes without adding any other reagents. The ultra-small (< 1 nm) carbon dots show robust excitation-depended photoluminescence under a wide pH range (4-10) or a strong ionic strength of up to 1 M, and the detection limit of mercury (II) has been determined as low as 18 nM. We envision such water-soluble, biocompatible carbon dots could be applied to bio-labeling, bio-imaging, and bio-sensing fields.

488

To treat technical problems of data acquisition, alarm management, and historical data archiving of radiation protection control system in TMSR (Thorium Molten Salt Reactor), a network prototype system was designed based on Experimental Physics and Industrial Control System (EPICS). Radiation level of many locations in Jiading campus of Shanghai Institute of Applied Physics is being continuously monitored, and boundaries of accelerator facilities and radiochemical areas are defined by the access control system. In this paper, we introduce the control system design, including human-machine interfaces, alarm system, historical data archiving system, and the software for access control. The software development followed the standard of Capability Maturity Model Integration (CMMI®) Level 3, and the software had passed a third party test, which indicated that the functionality and the reliability could fulfill the requirements of the radiation protection system.

350

A model of the operational amplifier based on VHDL-AMS is proposed. According to needs of simulating the total ionizing dose (TID) radiation effect, parameters of operational amplifier are taken into account when the performance is specified. The operational amplifier model used for the TID radiation effect simulation is completed after verifying each modeled parameter. And a parameter for describing the external environment is introduced to make the model combined with TID. Finally, an example is used to illustrate the TID effect on the operational amplifier of MC14573, proving the validity of the model.

415

A novel X-ray tube spectrum reconstruction method has been proposed based on transmission measurements. Aluminum bars of varying lengths attenuate the X-rays to different levels. The detectors are of lutetium yttrium oxyorthosilicate scintillator (LYSO) and silicon photomultiplier (SiPM). With the detected X-ray intensities, the X-ray spectrum is unfolded using the least square method. The detectors, aluminum bars and collimating apertures are integrated in a detection module made of lead. Its response to X-ray is calculated by Monte Carlo codes Geant4. Due to the high photon flux, the detectors work in current mode. The electronics system, consisting of 24-bit high precision ADCs with 144KSPS sampling rate and field programmable gate array (FPGA), make the data acquisition process effective and precise. Measurements on a 70 kVp tungsten anode X-ray was taken to verify the method. The unfolded spectrum agrees well with the simulated spectrum, demonstrating that the method is reliable and practical.

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424

Flow rate and temperature are important parameters for design and operation of liquid lead-bismuth (PbBi) experimental loop. The PREKY facility was designed to study test technique of flow rate and local temperature of PbBi loop. In this work, flow rate monitoring of molten PbBi was performed, and temperatures of the PbBi and pipe surface were measured. The results show that the flow rate of the Venturi-nozzle flow meter (VNFM) had an uncertainty of ±5% in the range of 0.6~2.0 m/s, and the maximum temperature difference between the PbBi and pipe surface was about 8°C. PREKY can be used to measure high temperature PbBi.

328

Due to its advantages in large-area application situations, the R&D of the Resistive Plate Chamber (RPC) has always been carried out. A performance test station for RPC R&D has been designed and developed based on the VME bus and ROOT in Linux. This system can be customized expediently according to the requirements of different tests, which facilitates detector R&D because of its automatic HV scan, especially for long term test. With this system, we have implemented the RPC performance test, including the efficiency curve, counting rate, dark current and charge and timing resolution.

428

The Experimental Advanced Superconducting Tokamak (EAST) has two suits of ion cyclotron radio frequency (ICRF) heating systems, in which the two antennas are of different structures. Their performance is assessed and compared by CST Microwave studio (MWS). The radiating capacity of antennas and the arcing around them are estimated. The impurity release is analyzed by the radio frequency (RF) potential in the plasma sheath. The simulation results show that the radiating capacity for the folded antenna (I-port) is better than those for the double loops antenna (B-port). However, the folded antenna is worse than the double loops antenna in terms of breakdown. Moreover, the impurity production is relevant to spectrum shaping. The RF potential at (0,π,π,0) phasing with the peak of spectrum k_//=8.5 m⁻¹ is lower than the one with other phases. The impurity is reduced obviously when the folded antenna is powered with (0,π,π,0) phasing.

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