Vol.31,

The China Dual-Functional Lithium-Lead test blanket module (DFLL-TBM) is a liquid LiPb blanket concept developed by the Institute of Nuclear Energy Safety Technology of the Chinese Academy of Sciences for testing in ITER to validate relevant tritium breeding and shielding technologies. In this study, neutronic calculations of DFLL-TBM were carried out using a massively parallel three-dimensional transport code, Hydra, with the Fusion Evaluated Nuclear Data Library/MG. Hydra was developed by the Nuclear Engineering Computational Physics Lab based on the discrete ordinates method and has been devoted to neutronic analysis and shielding evaluation for nuclear facilities. An in-house Monte-Carlo code (MCX) was employed to verify the discretized calculation model used by Hydra for the DFLL-TBM calculations. The results showed two key aspects: 1) in most material zones, Hydra solutions are in good agreement with the reference MCX results within 1%, and the maximal relative difference of the neutron flux is merely 3%, demonstrating the correctness of the calculation model; 2) whilst the current DFLL-TBM design meets the operation shielding requirement of ITER for four years, it does not satisfy the tritium self-sufficiency requirement. Compared to the two-step approach, Hydra produces higher accuracies as it does not rely on the homogenization technique during the calculation process. The parallel efficiency tests of Hydra using the DFLL-TBM model also showed that this code maintains a high parallel efficiency on O(100) processors, and as a result, is able to significantly improve computing performance through parallelization. Parameter studies have been carried out by varying the thickness of the beryllium armor layer and the tritium breeding zone to understand the influence of the beryllium layer and breeding zone thickness on tritium breeding performance. This establishes a foundation for further improvement in the tritium production performance of DFLL-TBM.

345

Early fault warning for nuclear power machinery is conducive to timely troubleshooting and reductions in safety risks and unnecessary costs. This paper presents a novel intelligent fault prediction method, integrated probabilistic principal component analysis (PPCA), multi-resolution wavelet analysis, Bayesian inference, and RNN model for nuclear power machinery that consider data uncertainty and chaotic time series. After denoising the source data, the Bayesian PPCA method is employed for dimensional reduction to obtain a refined data group. An recurrent neural network (RNN) prediction model is constructed, and a Bayesian statistical inference approach is developed to quantitatively assess the prediction reliability of the model. By modeling and analyzing the data collected on the steam turbine and components of a nuclear power plant, the results of the goodness of fit, mean square error distribution, and Bayesian confidence indicate that the proposed RNN model can implement early warning in the fault creep period. The accuracy and reliability of the proposed model are quantitatively verified.

481

The enhanced diffusion in materials under irradiation plays an important role in the long-term microstructural evolution. In this work, the self-ion irradiation in high-purity nickel was used as a model system to study the effect of radiation-enhanced diffusion on the implanted ion profiles. Initially, the depth profiles of vacancies and implanted ions for nickel self-ion irradiation with ion energies up to 15 MeV were computed by the high-efficiency Monte Carlo code IM3D (Irradiation of Materials in 3D). The results are in good agreement with those predicted by SRIM (Stopping and Range of Ions in Matter). Then, diffusion coefficients as functions of temperature and damage rate were obtained, and the depth-dependent diffusion coefficients at various temperatures and damage rates were also illustrated. For this purpose, we used a temperature-dependent effective sink concentration for nickel, which was estimated from the available experimental investigations on the damage structures of irradiated nickel. At length, case studies on the time evolution of implanted ion profiles under the condition of nickel self-irradiation were performed and discussed based on Fick’s second law. The results help to understand the fundamental atomic diffusion properties in ion irradiation, especially under higher-dose irradiation.

450

The recent development of molten salt fast reactors has generated a renewed interest in them. As compared to traditional solid-fueled fast neutron systems, it has many unique advantages, e.g., lower fissile inventory, no initial criticality reserve, waste reduction, and a simplified fuel cycle. It has been recognized as an ideal reactor for achieving a closed Th-U cycle. Based on the carrier-salt, molten salt fast reactors could be divided into either a molten chloride salt fast reactor (MCFR) or a molten fluoride salt fast reactor (MFFR); to compare their Th-U cycle performance, the neutronic parameters in a Breeding and Burning (B&B) transition scenario were studied based on similar core geometry and power. The results demonstrated that the required reprocessing rate for an MCFR to achieve self-breeding was lower than that of an MFFR. Moreover, the breeding capability of an MCFR was better than that of an MFFR; at a reprocessing rate of 40 L/day, using LEU and Pu as start-up fissile materials, the doubling-time (DT) of an MFFR and MCFR were 88.0 years and 48.0 years, and 16.5 years and 16.2 years, respectively. Besides, an MCFR has lower radio-toxicity due to lower buildup of fission products (FPs) and transuranium (TRU), while an MFFR has a larger, delayed neutron fraction with smaller changes during the entire operation.

384

In recent years cooling technology for Liquid Xenon (LXe) detectors has advanced driven by the development of Dark Matter (DM) detectors with target mass in the 100 – 1000 kg range. The next generation of DM detectors based on LXe will be in the 50000 kg (50 t) range requiring more than 1 kW of cooling power. Most of the prior cooling methods become impractical at this level. For cooling a 50 t scale LXe detector, a method is proposed in which Liquid Nitrogen (LN2) in a small local reservoir cools the xenon gas via a cold finger. The cold finger incorporates a heating unit to provide temperature regulation.The proposed cooling method is simple, reliable, and suitable for the required long-term operation for a rare event search. The device can be easily integrated into present cooling systems, e.g. the 'Cooling Bus’ employed for the PandaX I and II experiments. It is still possible to cool indirectly with no part of the cooling or temperature control system getting in direct contact with the clean xenon in the detector. Also the cooling device can be mounted at a large distance, i.e. the detector is cooled remotely from a distance of 5 – 10 m. The method was tested in a laboratory setup at Columbia University to carry out different measurements with a small LXe detector and behaved exactly as predicted.

367

The ramifications of the effective mass splitting on the nuclear stopping and isospin tracer during heavy-ion collisions within the gigaelectron volt energy region are studied using an isospin-dependent quantum molecular dynamics model. Three isotope probes, i.e., a proton, deuteron, and triton, are used to calculate the nuclear stopping. Compared to the mn*>mp* case, the mn*<mp* parameter results in a stronger stopping for protons but a weaker stopping for tritons. The calculations of the isospin tracer show that the mn*>mp* parameter results in a higher isospin mix than the mn*<mp* parameter. The rapidity and impact parameter dependences of the isospin tracer are also studied. A constraining of the effective mass splitting using the free nucleons with high rapidity and in a central rather than peripheral collision is suggested.

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Automatic conversion from a computer-aided design (CAD) model to Monte Carlo geometry is one of the most effective methods for large-scale and detailed Monte Carlo modeling. The CAD to Monte Carlo geometry converter (CMGC) is a newly developed conversion code based on the boundary representation to constructive solid geometry (BRep→CSG) conversion method. The goal of the conversion process in the CMGC is to generate an appropriate CSG representation to achieve highly efficient Monte Carlo simulations. We designed a complete solid decomposition scheme to split a complex solid into as few nonoverlapping simple sub-solids as possible. In the complete solid decomposition scheme, the complex solid is successively split by so-called direct, indirect, and auxiliary splitting surfaces. We defined the splitting edge and designed a method for determining the direct splitting surface based on the splitting edge, then provided a method for determining indirect and auxiliary splitting surfaces based on solid vertices. Only the sub-solids that contain concave boundary faces need to be supplemented with auxiliary surfaces because the solid is completely decomposed, which will reduce the redundancy in the CSG expression. After decomposition, these sub-solids are located on only one side of their natural and auxiliary surfaces; thus, each sub-solid can be described by the intersections of a series of half-spaces or geometrical primitives. The CMGC has a friendly graphical user interface and can convert a CAD model into geometry input files for several Monte Carlo codes. The reliability of the CMGC was evaluated by converting several complex models and calculating the relative volume errors. Moreover, JMCT was used to test the efficiency of the Monte Carlo simulation. The results showed that the converted models performed well in particle transport calculations.

530

The mechanism of deuteron formation in neutron-induced reactions is studied within the framework of the isospin-dependent quantum molecular dynamics (IQMD) model, using the GEMINI code. The influence of the n+p→d reaction channel is investigated by analyzing the deuteron production cross-sections in the neutron-induced reactions ¹²C(n,d), ¹⁶O(n,d), and ²⁸Si(n,d), with incident energies of 20-100 MeV. By including the n+p→d reaction channel when modeling the collision, the deuteron production cross-sections increase, optimizing the cross-section results and bringing them closer to the experimental data values. This indicates that the n+p→d reaction channel is an important mechanism for enhancing deuteron production.

419

Stealth technology plays an important role in modern military conflicts, especially when used in fighter jets. Since airfoil structures have a leading edge, inlet, and surface bulge that are easily detected by radar, it is necessary to study the stealth of these structures. In this study, we investigate structures coated with radionuclides to generate plasma. Using simulation and calculation methods, the attenuation of 0.1–10 GHz electromagnetic waves propagating in plasma was studied. The results show that the attenuation of low-frequency electromagnetic waves is greater than that of high-frequency electromagnetic waves. The attenuation of 0.1–1 GHz electromagnetic waves is found to be less than –2.7 dB, –3.0 dB, and –15.6 dB at the airfoil leading edge, inlet, and surface bulge structures, respectively. We also found that the attenuation of electromagnetic waves with 0°-incidence is greater than that of waves with 10°, 20°, and 30° incidence angles. Additionally, the attenuation of electromagnetic waves decreases gradually as the incident angle increases.

331

Serotonin is one of the significant signaling molecules used by several neural systems in the gut and brain. This study aimed to develop a novel and potent tracer for targeting, detecting, and imaging serotonin receptors (5-HTRs), which is a promising tool in the determination of the receptor’s function and relationship with the diseases related to serotonin and it’s receptor dysfunction.. Serotonin was effectively labeled via a direct electrophilic substitutional reaction using an oxidizing agent such as iodogen with ¹²⁵I in a neutral medium, and ¹²⁵I-serotonin was achieved with a maximum labeling yield of 91 ± 0.63% with in vitro stability up to 24 h. Molecular modeling was conducted to signify ¹²⁵I-serotonin structure and confirm that the radiolabeling process did not affect serotonin binding ability to its receptors. Biodistribution studies show that the maximum gastro intestinal tract Gastro Intestinal Tract (GIT) uptake of ¹²⁵I-serotonin was 17.8 ± 0.93% ID/organ after 30 min post-injection and the tracer’s ability to pass the blood-brain barrier. Thus, ¹²⁵I-serotonin is a promising single photon emmision computed tomography Single Photon Emission Computed Tomography (SPECT) tracer in the detection of 5HTRs.

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