Antitumor and radiosensitization effect of 12C6+heavy-ion irradiation mediated by radiation-inducible gene therapy

Radio genetic therapy which combines gene therapy with radiotherapy has shown promising results in cancer treatment. In this study, an oncolytic adenovirusbased gene therapy system regulated by radiation was constructed to improve the cancer curative effect. This gene therapy system incorporated the radiation-inducible early growth response gene(Egr-1) promoter and the anticancer gene tumor necrosis factor-related apoptosis-inducing ligand(TRAIL). To confirm the antitumor effect of Ad-ET combined with^12C^(6+)tion irradiation, the survival and apoptosis fraction of tumor cells HT1080 and normal cells MRC-5 in combination treatment were detected by CCK-8 assay and FACS analysis. Then the expression levels of TRAIL gene and protein were tested by real-time PCR and western blotting. The results show that^12C^(6+)tion irradiation could induce cell growth inhibition and apoptosis by activating the TRAIL gene expression in tumor cells, while exhibiting no obvious toxicity to the normal lung cell line MRC-5. Theresults also demonstrate that use of an oncolytic adenovirusbased radiation-inducible gene therapy system together with^12C^(6+)tion irradiation could cause synergistic antitumor effect specifically in tumor cells but not in normal cells. The results indicate that the novel radio genetic therapy could potentiate radiation treatment by improving the safety and efficiency of monotherapy, and provide theoretical support for clinical application of combination treatment.

Design and R＆D Progress of China Lead-Based Reactor for ADS Research Facility

In 2011,the Chinese Academy of Sciences launched an engineering project to develop an acceleratordriven subcritical system(ADS)for nuclear waste transmutation.The China Lead-based Reactor(CLEAR),proposed by the Institute of Nuclear Energy Safety Technology,was selected as the reference reactor for ADS development,as well as for the technology development of the Generation IV lead-cooled fast reactor.The conceptual design of CLEAR-I with 10 MW thermal power has been completed.KYLIN series lead-bismuth eutectic experimental loops have been constructed to investigate the technologies of the coolant,key components,structural materials,fuel assembly,operation,and control.In order to validate and test the key components and integrated operating technology of the lead-based reactor,the lead alloy-cooled non-nuclear reactor CLEAR-S,the lead-based zero-power nuclear reactor CLEAR-0,and the lead-based virtual reactor CLEAR-V are under realization.

Experimental study on fragmentation behaviors of molten LBE and water contact interface

Based on the design of CLEAR(China LEAd-based Reactor), it is important to study the molten LBE(LeadBismuth Eutectic)/water interaction following an incidental steam generator tube rupture(SGTR) accident.Experiments were carried out to investigate the fragmentation behavior of the molten LBE/water contacting interface, with a high-speed video camera to record the fragmentation behavior of 300–600?C LBE at 20?C and 80?C of water temperature. Violent explosion phenomenon occurred at water temperature of 20?C, while no explosion occurred at 80?C. Shapes of the LBE debris became round at 80?C of water temperature, whereas the debris was of the needle-like shape at 20?C. For all the molten LBE and water temperatures in the present study,the debris sized at 2.8–5.0 mm had the largest mass fraction. The results indicate that the dominant physical mechanism of the molten LBE fragmentation was the Kelvin-Helmholtz instability between LBE/water direct contact interface.

Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes

Adsorption and desorption of hydrogen on/from single-vacancy and double-vacancy graphenes were studied by means of first-principles calculations. The structure and stability of continuous hydrogenation in single vacancy were investigated. Several new stable structures were found, along with their corresponding energy barriers. In double-vacancy graphene, the preferred sites of H atoms were identified, and H2 molecule desorption and adsorption of from/on were calculated from the energy barriers. This work provides a systematic and comprehensive understanding of hydrogen behavior on defected graphene.

Seismic and stress qualification of LMFR fuel rod and simple method for the determination of LBE added mass effect

In this study, two different designs of liquid metal fast reactor(LMFR) fuel rods wire-wrapped and nonwire-wrapped(bare) are compared with respect to different parameters as a means of considering the optimum fuel design. Nuclear seismic rules require that systems and components that are important for safety must be capable of bearing earthquake effects, and that their integrity and functionality should be guaranteed. Mode shapes, natural frequencies, stresses on cladding, and seismic aspects are considered for comparison using ANSYS. Modal analysis is compared in a vacuum and in lead–bismuth eutectic(LBE) using potential flow theory by considering the added mass effect. A simple and accurate approach is suggested for the determination of the LBE added mass effect and is verified by a manually calculated added mass, which further proved the usefulness of potential flow theory for the accurate estimation of the added mass effect. The verification of the hydrodynamic function(τ) over the entire frequency range further validated the finite element method(FEM) modal analysis results. Stresses obtained for fuel rods against different loading combinations revealed that they were within the allowable limits with maximum stress ratios of 0.25(bare) and 0.74(wire-wrapped). In order to verify the structural integrity of cladding tubes, stresses along the cladding length were determined during different transients and were also calculated manually for static pressure. The manual calculations could be roughly compared with the ANSYS results, and the two showed a close agreement. Contact analysis methodology was selected,and the most appropriate analysis options were suggested for establishing contact between the wire and cladding for the wire-wrapped design grid independence analysis,which proved the accuracy of the results, confirmed the selection of the appropriate procedure, and validated the use of the ANSYS mechanical APDL code for LMFR fuel rod analysis. The results provided detailed insight into the structural design of LMFR fuel rods by considering different structural configurations(i.e., bare and wire-wrapped) in the seismic loading;this not only provides a FEM procedure for LMFR fuel with complex configuration, but also guides the reference design of LMFR fuel rods.

Experiment and analysis on flow rate and temperature of liquid PbBi in PREKY

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

Correction to:Seismic and stress qualification of LMFR fuel rod and simple method for the determination of LBE added mass effect

In the original article the authors affiliations are incorrectly published.The authors correct affiliations are provided in this correction article.

Flow characteristics of natural circulation in a lead–bismuth eutectic loop

Lead and lead-alloys are proposed in future advanced nuclear system as coolant and spallation target.To test the natural circulation and gas-lift and obtain thermal-hydraulics data for computational fluid dynamics(CFD) and system code validation, a lead–bismuth eutectic rectangular loop, the KYLIN-Ⅱ Thermal Hydraulic natural circulation test loop, has been designed and constructed by the FDS team. In this paper, theoretical analysis on natural circulation thermal-hydraulic performance is described and the steady-state natural circulation experiment is performed. The results indicated that the natural circulation capability depends on the loop resistance and the temperature and center height differences between the hot and cold legs. The theoretical analysis results agree well with,while the CFD deviate from, the experimental results.

A method for direct conversion of EPID images to incident fluence for dose reconstruction

A direct incident fluence measurement method based on amorphous silicon electronic portal imaging device(a-Si EPID) has been developed for pretreatment verification of intensity-modulated radiation therapy(IMRT).The EPID-based incident fluence conversion method deconvolves EPID images to the primary response distribution based on measured lateral scatter kernels in the EPID detector using Conjugate Gradient algorithm.The primary response is converted to the incident fluence based on measured fluence conversion matrix which corrects for off-axis position dependence of the a-Si EPID response and the "horn" beam profile caused by flatting filter. To verify feasibility and accuracy of this method, square fields of various sizes and two IMRT plans were delivered. The dose distributions computed based on EPID-derived incident fluence were compared with the measurement data. For all square field sizes except the smallest field(2 cm), the mean dose differences in cross-line dose profiles were within 1% excluding the penumbra region, and gamma passing percentages with a 2%/2 mm criterion were about 99%. For two IMRT plans, the least gamma passing percentage for all eight IMRT fields was 98.14% with 2%/3 mm criteria. It can be concluded that our direct EPID-based incident fluence conversion method is accurate and capable of being applied to pretreatment dose verification in clinical routines.

Physics Analysis and Optimization Studies for a Fusion Neutron Source Based on a Gas Dynamic Trap

To further investigate the fusion neutron source based on a gas dynamic trap （GDT）, characteristics of the GDT were analyzed and physics analyses were made for a fusion neutron source based on the GDT concept. The prior design of a GDT-based fusion neutron source was optimized based on a refreshed understanding of GDT operation. A two-step progressive development route of a GDT-based fusion neutron source was suggested. Potential applications of GDT are discussed. Preliminary analyses show that a fusion neutron source based on the GDT concept is suitable for plasma-material interaction research, fusion material and subcomponent testing, and capable of driving a proof-of-principle fusion fission hybrid experimental facility.

Development of a 1200 fine group nuclear data library for advanced nuclear systems

Accurate and reliable nuclear data libraries are essential for calculation and design of advanced nuclea systems. A 1200 fine group nuclear data library Hybrid Evaluated Nuclear Data Library/Fine Group(HENDL/FG with neutrons of up to 150 Me V has been developed to improve the accuracy of neutronics calculations and anal ysis. Corrections of Doppler, resonance self-shielding, and thermal upscatter effects were done for HENDL/FG Shielding and critical safety benchmarks were performed to test the accuracy and reliability of the library. The dis crepancy between calculated and measured nuclea parameters fell into a reasonable range.

Biological effects of human lung cells MRC-5 in CBCT positioning for image-guided radiotherapy

Image-guided radiotherapy(IGRT) provides precise positioning for the tumor target, but it may bring extra irradiation dose in the target positioning with a cone beam CT(CBCT) which has been increasingly used in IGRT. In this work, we focused on biological effects of the low-dose irradiation in IGRT, which have not been considered so far. Primary human fibroblasts cells from the lung and MRC-5 were irradiated by a CBCT. DNA doublestrand breaks(c-H2 AX foci) and micronucleus frequency of the irradiated samples were analyzed. Compared to the control, the c-H2 AX foci yields of the samples irradiated to 16 m Gy increased significantly, and the micronuclei rate of the samples irradiated for 3 days increased notably. The dose by imaging guidance device can be genotoxic to normal tissue cells, suggesting a potential risk of a secondary cancer. The effects, if confirmed by clinical studies,should be considered prudentially in designing IGRT treatment plans for the radiosensitive population, especially for children.

Analysis of beryllium poisoning effect on liquid metal reactor with U–Be alloy fuel

A liquid metal reactor(LMR) loaded with a fuel compound of uranium and beryllium(U-Be alloy fuel),which was cooled by a lead-bismuth eutectic alloy(PbBi),has been applied in Russian Alfa-class nuclear submarines.Because of the large amount of beryllium in the core, the reaction between the beryllium atoms and neutrons could result in the accumulation of 3 He and 6 Li, which are called the "poisoned elements" owing to their large thermal neutron capture cross section. The accumulation of neutron absorber can affect the performance of a reactor. In this study, the Super Multi-functional Calculation Program(SuperMC) code, which was developed by Institute of Nuclear Energy Safety Technology of the Chinese Academy of Sciences(INEST, CAS), was adopted to illustrate the influence of beryllium on an LMR.

Analysis of fixation method of fuel assembly for lead-alloy cooled reactor

As a potential candidate for generation IV reactors, lead-alloy cooled reactor has attracted much attentions in recent years. The China LEAd-based research Reactor(CLEAR) is proposed as the primary choice for the accelerator driven subcritical system project launched by Chinese Academy of Sciences. Lead-bismuth eutectic(LBE) is selected as the coolant of CLEAR owing to its efficient heat conductivity properties and high production rate of neutrons. In order to compensate the buoyancy due to the high density of lead-alloy, fixation methods of fuel assembly(FA) have become a research hotspot worldwide. In this paper, we report an integrated system of ballast and fuel element for CLEAR FA. It guarantees the correct positioning of each FA in normal and refueling operations. Force calculation and temperature analysis prove that the FA will be stable and safe under CLEAR operation conditions.

Biasing transition rate method based on direct MC simulation for probabilistic safety assessment

Direct Monte Carlo(MC) simulation is a powerful probabilistic safety assessment method for accounting dynamics of the system.But it is not efficient at simulating rare events.A biasing transition rate method based on direct MC simulation is proposed to solve the problem in this paper.This method biases transition rates of the components by adding virtual components to them in series to increase the occurrence probability of the rare event,hence the decrease in the variance of MC estimator.Several cases are used to benchmark this method.The results show that the method is effective at modeling system failure and is more efficient at collecting evidence of rare events than the direct MC simulation.The performance is greatly improved by the biasing transition rate method.

Preliminary analysis of reactivity reconstruction capability based on inverse kinetics method under different initial reactivity states

Online reactivity monitoring plays an important role in operation and safety analyses of fission reactor systems. The inverse kinetics method, which is based on a point kinetics model, is the most widely used method for reactivity reconstruction of critical water reactors. However, this method is seldom applied to the reactivity reconstruction of subcritical reactors. In this study, an inverse kinetics method was employed for the reactivity reconstruction of a lead-based reactor under different initial reactivity states(ρ_0= 0,-2786,-5486,-8367, and-12,371 pcm). The results showed that the deviation in the reactivity of the lead-based subcritical reactor was greater when ρ_0 became smaller. The reactivity reconstructed using the inverse kinetics method was globally underestimated. At a given reactivity perturbation, the relative and absolute errors increased with the decrease in the initial reactivity. At a given initial reactivity, with the increase in the reactivity perturbation, the absolute error increased, whereas the relative error remained the same.This deviation is due to the variation in the external neutron source, spatial-spectral effects, and sub-diffusive effects, which require further study.

An algorithm for Monte Carlo simulation of bremsstrahlung emission by electrons

An algorithm for Monte Carlo simulation of bremsstrahlung emission by electrons based on the framework of Super MC is presented in this paper with efficient and accurate methods to sample the angular distribution and energy of bremsstrahlung photons. The photon energy is sampled according to scaled energy-loss differential cross sections tabulated by Seltzer and Berger. A novel hybrid model for photon angular distribution by low-and high-energy incident electrons is developed. The model uses Tsai's full form of angular distribution function with atomic form factors for high-energy incident electrons. For electrons o\500 ke V, a simple efficient and accurate analytical distribution function is developed, using adjustable parameters determined from the fitting of numerical values of the shape functions tabulated by Kissel et al. The efficiency of sampling photon energy is 80%. Our angular sampling algorithm for high-energy electron bremsstrahlung based on Tsai distribution function is very efficient(sampling efficiency*70%) in the useful photon energy range.

Data decomposition method for full-core Monte Carlo transport–burnup calculation

Monte Carlo transport simulations of a full-core reactor with a high-fidelity structure have been made possible by modern-day computing capabilities. Performing transport–burnup calculations of a full-core model typically includes millions of burnup areas requiring hundreds of gigabytes of memory for burnup-related tallies. This paper presents the study of a parallel computing method for full-core Monte Carlo transport–burnup calculations and the development of a thread-level data decomposition method. The proposed method decomposes tally accumulators into different threads and improves the parallel communication pattern and memory access efficiency. A typical pressurized water reactor burnup assembly along with the benchmark for evaluation and validation of reactor simulations model was used to test the proposed method.The result indicates that the method effectively reduces memory consumption and maintains high parallel efficiency.

Direct aperture optimization based on genetic algorithm and conjugate gradient in intensity modulated radiation therapy

For resolving the problem that a conventional intensity modulated radiotherapy （IMRT） plan designed with the ＂two-step method＂-creates a greater number of apertures and total Monitor Units （MU）, the direct aperture optimization （DAO） method using a genetic algorithm and conjugate gradient was studied based on Accurate/ Advanced Radiation Therapy System （ARTS） developed by the FDS Team （www.fds.org.cn）.