Vol.34,

N,N,N’,N’-Tetraoctyl diglycolamide (TODGA) is one of the most promising extractants tailored for high-level liquid radioactive waste treatment during nuclear fuel reprocessing. The γ-radiolysis of TODGA (0.2 mol/L) in n-dodecane (nDD) solution with and without pre-equilibrated 3.0 mol/L HNO₃ was investigated using HPLC and UPLC-QTOF-MS and compared with the γ-radiolysis of neat TODGA in this study. With increased absorbed doses, the concentration of TODGA decreased exponentially for the studied systems. Moreover, pre-equilibration with HNO₃ (3.0 mol/L) slightly influenced the γ-radiolysis of TODGA in nDD. Seven radiolytic products generated from the rupture of the C – C, C – O, and C – N bonds in TODGA were identified in the studied extraction system. The influence of γ-radiation on TODGA/nDD for the extraction of Eu(III) was evaluated using the first combination of extraction experiments and density functional theory (DFT) calculations, in which the complexations of Eu(III) with TODGA and its radiolytic products were systematically compared. Based on the radiolysis kinetic model of TODGA, the slope curve of the distribution ratio of Eu(III) (D_Eu) and the absorbed dose, and fluorescence titration analysis, the empirical equation of the absorbed dose and D_Eu was obtained successfully. Below 300 kGy, the experimental D_Eu agreed well with the obtained empirical equation for TODGA/nDD. Conversely, at a high absorbed dose, the experimental D_Eu was higher than the theoretical D_Eu based on the empirical equation because the radiolytic products of TODGA with similar coordination structures still possessed partial complexation toward Eu(III) This was confirmed by DFT calculations. This work provides a method to predict the extraction distribution ratio of an irradiated extractant system and to understand the complex extraction process.

500

The spatial distributions of ^239+240Pu and ¹³⁷Cs in soils from Longji Rice Terraces were investigated to evaluate soil erosion. The activity concentrations of ^239+240Pu and ¹³⁷Cs in the surface soils of the paddy fields were in the range of 0.089-0.734 and 1.80-7.88 mBq/g, respectively. The activities of ^239+240Pu and ¹³⁷Cs showed very similar distribution trends, first increasing and then decreasing with increasing elevation. The ²⁴⁰Pu/²³⁹Pu atom ratios in the surface soils ranged from 0.162–0.232. The activities of ^239+240Pu and ¹³⁷Cs in the soil cores tended to be uniformly distributed within the plowed layer and declined exponentially below this depth. The mean soil erosion rates of Longji Rice Terraces estimated by ^239+240Pu and ¹³⁷Cs tracer methods were 5.44 t/(ha·a) and 5.16 t/(ha·a), respectively, which demonstrated that plutonium can replace ¹³⁷Cs as an ideal tracer for soil erosion research in the future. Landform features are the main factors affecting the distribution of plutonium and ¹³⁷Cs as well as soil erosion in the Longji Rice Terraces.

551

Gamma-emitting radionuclide ^99mTc is globally used for the diagnosis of various pathological conditions owing to its ideal single-photon emission computed tomography (SPECT) characteristics. However, the short half-life of ^99mTc (T_1/2 = 6 h) makes it difficult to store or transport. Thus, the production of ^99mTc is tied to its parent radionuclide ⁹⁹Mo (T_1/2 = 66 h). The major production paths are based on accelerators and research reactors. The reactor process presents the potential for nuclear proliferation owing to its use of highly enriched Uranium (HEU). Accelerator-based methods tend to use deuterium-tritium (D-T) neutron sources but are hindered by the high cost of tritium and its challenging operation. In this study, a new ⁹⁹Mo production design was developed based on a deuterium-deuterium (D-D) gas dynamic trap fusion neutron source (GDT-FNS) and a subcritical blanket system (SBS) assembly with a low-enriched Uranium (LEU) solution. GDT-FNS can provide a relatively high neutron intensity, which is one of the advantages of ⁹⁹Mo production. We provide a Monte Carlo-based neutronics analysis covering the calculation of the subcritical multiplication factor (k_s) of the SBS, optimization design for the reflector, shielding layer, and ⁹⁹Mo production capacity. Other calculations, including the neutron flux and nuclear heating distributions, are also provided for an overall evaluation of the production system. The results demonstrated that the SBS meets the nuclear critical safety design requirement (k_s<0.97) and maintained a high⁹⁹Mo production capacity. The proposed system can generate approximately 157 Ci ⁹⁹Mo for a stable 24 h operation with a neutron intensity of 1×10¹⁴ n/s, which can meet 50% of China's demand in 2025.

630

In this study, based on a two-potential approach, we systematically investigated the proton radioactivity half-lives of spherical proton emitters with 69≤ Z ≤ 81 from the ground and/or isomeric state, choosing the nuclear potential to be a modified Woods–Saxon potential that contains the isospin effect of the daughter nucleus. It was found that the calculated half-lives could reproduce the experimental data well. Furthermore, we extended this model to predict the half-lives of 17 proton-emitting candidates whose radioactivity is energetically allowed or observed but not yet quantified in NUBASE2020. For comparison, the unified fission model, Coulomb potential and proximity potential model, universal decay law for proton emission, and new Geiger–Nuttall law were also used. All the predicted results are consistent with each other.

397

Compton camera-based prompt gamma (PG) imaging has been proposed for range verification during proton therapy. However, a deviation between the PG and dose distributions, as well as the difference between the reconstructed PG and exact values, limit the effectiveness of the approach in accurate range monitoring during clinical applications. The aim of the study was to realize a PG-based dose reconstruction with a Compton camera, thereby further improving the prediction accuracy of in-vivo range verification and providing a novel method for beam monitoring during proton therapy. In this paper, we present an approach based on a subset-driven origin ensemble with resolution recovery and a double evolutionary algorithm to reconstruct the dose depth profile (DDP) from the gamma events obtained by a Cadmium-Zinc-Telluride Compton camera with limited position and energy resolution. Simulations of proton pencil beams with clinical particle rate irradiating phantoms made of different materials and the CT-based thoracic phantom were used to evaluate the feasibility of the proposed method. The results show that for the monoenergetic proton pencil beam irradiating homogeneous-material box phantom, the accuracy of the reconstructed DDP was within 0.3 mm for range prediction and within 5.2% for dose prediction. In particular, for 1.6-Gy irradiation in the therapy simulation of thoracic tumors, the range deviation of the reconstructed spread-out Bragg peak was within 0.8 mm, and the relative dose deviation in the peak area was less than 7% compared to the exact values. The results demonstrate the potential and feasibility of the proposed method in future Compton-based accurate dose reconstruction and range verification during proton therapy.

629

In this study, the rapidity distribution, collective flows, and nuclear stopping power in ¹⁹⁷Au+¹⁹⁷Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics (UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.

601

429

Workers who conduct regular facility inspections in radioactive environments will inevitably be affected by radiation. Therefore, it is important to optimize the inspection path to ensure that workers are exposed to the least amount of radiation. This study proposes a discrete Rao-combined artificial bee colony (ABC) algorithm for planning inspection paths with minimum exposure doses in radioactive environments with obstacles. In this algorithm, retaining the framework of the traditional ABC algorithm, we applied the directional solution update rules of Rao algorithms at the employed bee stage and onlooker bee stage to increase the exploitation ability of the algorithm and implement discretion using the swap operator and swap sequence. To increase the randomness of solution generation, the chaos algorithm was used at the initialization stage. The K-opt operation technique was introduced at the scout bee stage to increase the exploration ability of the algorithm. For path planning in an environment with complex structural obstacles, an obstacle detour technique using a recursive algorithm was applied. To evaluate the performance of the proposed algorithm, we performed experimental simulations in three hypothetical environments and compared the results with those of improved particle swarm optimization, chaos particle swarm optimization, improved ant colony optimization, and discrete Rao's algorithms. The experimental results show the high performance of the proposed discrete Rao-combined ABC algorithm and its obstacle detour capability.

552

Considering the significance of low-energy electrons (LEEs; 0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles (AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.

381

When multiphysics coupling calculations contain time-dependent Monte Carlo particle transport simulations, these simulations often account for the largest part of the calculation time, which is insufferable in certain important cases. This study proposes an adaptive strategy for automatically adjusting the sample size to fulfil more reasonable simulations. This is realized based on an extension of the Shannon entropy concept and is essentially different from the popular methods in time-independent Monte Carlo particle transport simulations, such as controlling the sample size according to the relative error of a target tally or by experience. The results of the two models show that this strategy can yield almost similar results while significantly reducing the calculation time. Considering the efficiency, the sample size should not be increased blindly if the efficiency cannot be enhanced further. The strategy proposed herein satisfies this requirement.

584

A novel and fast three-dimensional reconstruction method for a Compton camera and its performance in radionuclide imaging is proposed and analyzed in this study. A conical-surface sampling back-projection method with scattering angle correction (CSS-BP-SC) can quickly perform the back-projection process of the Compton cone and can be used to precompute the list-mode maximum likelihood expectation maximization (LM-MLEM). A dedicated parallel architecture was designed for the graphics processing unit acceleration of the back projection and iteration stage of the CSS-BP-SC-based LM-MLEM. The imaging results of the two-point source Monte Carlo (MC) simulation demonstrate that by analyzing the full width at half maximum along the three coordinate axes, the CSS-BP-SC-based LM-MLEM can obtain imaging results comparable to those of the traditional reconstruction algorithm, that is, the simple back-projection-based LM-MLEM. The imaging results of the mouse phantom MC simulation and experiment demonstrate that the reconstruction results obtained by the proposed method sufficiently coincide with the set radioactivity distribution, and the speed increased by more than 664 times compared to the traditional reconstruction algorithm in the mouse phantom experiment. The proposed method will further advance the imaging applications of Compton cameras.

549

The application of a thermoluminescent detector (TLD) for dose detection at the liver irradiation site in mice under linear accelerator precision radiotherapy and the use of a single high dose to irradiate the mouse liver to construct a biological model of a radiation-induced liver injury (RILD) in mice, in order to determine the feasibility of constructing a precision radiotherapy model in small animals under a linear accelerator. A 360° arc volumetric rotational intensity-modulated radiotherapy (VMAT) plan with a prescribed dose of 2 Gy was developed for the planned target volume (PTV) at the location of the TLD within solid water to compare the difference between the measured dose of TLD and the assessed parameters in the TPS system. The TLD was implanted in the livers of mice, and VMAT was planned based on TLD to compare the measured and prescribed doses. C57BL/6J mice were randomly divided into control and 25 Gy radiation groups, and were examined daily for changes in body weight. they were euthanized at 3 and 10 weeks after radiation, and the levels of liver serum enzymes such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were measured to observe any pathological histological changes in the irradiated areas of the mouse liver. The measured values of solid underwater TLD were within ±3% of the D_mean value of the evaluation parameter in the TPS system. The mice in the 25 Gy radiation group demonstrated pathological signs of radiation-induced liver injury at the site of liver irradiation. The deviation in the measured and prescribed doses of TLD in the mouse liver ranged from –1.5% to 6%; construction of an accurate model of RILD using the VMAT technique under a linear accelerator is feasible.

545

IMPCAS has constructed and currently manages a large number of accelerator facilities. However, the current accelerator monitoring methods are unable to satisfy all of the device requirements. The Accelerator Control Monitoring System (ACMS) was created and established to provide an efficient and accurate accelerator control monitoring system. It enables automatic alerting of problems with accelerator control systems and infrastructure. It utilizes a big data distributed stream processing engine and open-source monitoring tools. Metrics, logs, and EPICS PV values are the major three types of data that it monitors. Prometheus is primarily used to monitor metrics such as network traffic, hardware devices, and software operations. Graylog is used to monitor logs created by various applications and systems. We also created the EPICS Pulsar connector software, which allows us to transfer PV values to the Pulsar messaging cluster and use the Flink compute engine for real-time monitoring. The designed data management module allows users to define alert rules in a variety of ways. The ACMS enables the separation of the Flink business system and alarm rules. Users may use the data management module to add or alter alarm rules in real time without having to restart the alarm software. This reduces the effect of alarm flooding when the accelerator reaches the beam shifting or shutdown condition and dramatically enhances alarm efficiency. The main components of the ACMS may be deployed in clusters, making it extremely versatile. Experimental results demonstrated that it has a higher throughput than the Phoebus Alarm system and can handle millions of monitoring indicators. The ACMS employs a modular framework that is very scalable. Long-term stability analyses were performed at the SESRI and HIRFL facilities. It achieved all of the intended goals and could greatly improve the accident handling efficiency while minimizing the failure time of the accelerator control system.

602

The neutron spectrum unfolding by Bonner Spheres Spectrometer (BSS) is considered a complex multidimensional model, which requires complex mathematical methods to solve the first kind of Fredholm integral equation. In order to solve the problem of the Maximum Likelihood Expectation Maximization (MLEM) algorithm which is easy to suffer the pitfalls of local optima and the particle swarm optimization (PSO) algorithm which is easy to get unreasonable flight direction and step length of particles, which leads to the invalid iteration and affect efficiency and accuracy, an improved PSO-MLEM algorithm, combined of PSO and MLEM algorithm, is proposed for neutron spectrum unfolding. The dynamic acceleration factor is used to balance the ability of global and local search, and improves the convergence speed and accuracy of the algorithm. Firstly, the Monte Carlo method was used to simulated the BSS to obtain the response function and count rates of BSS. In the simulation of count rate, four reference spectra from the IAEA Technical Report Series No. 403 were used as input parameters of the Monte Carlo method. The PSO-MLEM algorithm was used to unfold the neutron spectrum of the simulated data and was verified by the difference of the unfolded spectrum to the reference spectrum. Finally, the ²⁵²Cf neutron source was measured by BSS, and the PSO-MLEM algorithm was used to unfold the experimental neutron spectrum. Compared with maximum entropy deconvolution (MAXED), PSO and MLEM algorithm, the PSO-MLEM algorithm has fewer parameters, and automatically adjusts the dynamic acceleration factor to solve the problem of local optima. The convergence speed of the PSO-MLEM algorithm is 1.4 times and 3.1 times that of the MLEM and PSO algorithms. Compared with PSO, MLEM and MAXED, the correlation coefficients of PSO-MLEM algorithm increase by 33.1%, 33.5% and 1.9%, and the relative mean errors decreased by 98.2%, 97.8% and 67.4%.

677

In this paper, we propose Hformer, a novel supervised learning model for low-dose computer tomography (LDCT) denoising. Hformer combines the strengths of convolutional neural networks (CNNs) for local feature extraction and transformer models for global feature capture. The performance of Hformer was verified and evaluated based on the AAPM-Mayo Clinic LDCT Grand Challenge Dataset. Compared with the former representative state-of-the-art (SOTA) model designs under different architectures, Hformer achieved optimal metrics without requiring a large number of learning parameters, with metrics of 33.4405 PSNR, 8.6956 RMSE, and 0.9163 SSIM. The experiments demonstratdesignedt Hformer is a SOTA model for noise suppression, structure preservation, and lesion detection.

527

A kicker is a critical component for beam injection and accumulation in circular particle accelerators. A ceramic slat kicker plated with a TiN conductive coating was applied in the Beijing Electron Positron Collider (BEPC2). However, the ceramic slat kicker has experienced several sudden malfunctions during the operation of the BEPC2 in the past. With a reliable kicker structure, a three-metal-strip kicker can substitute the original ceramic slat kicker to maintain the operational stability of the BEPC2. A comparison of the numerical simulation was conducted for three kicker models, demonstrating the comprehensive advantage of the three-metal-strip kicker. Furthermore, impedance bench measurements were conducted on a prototype of a three-metal-strip kicker. The longitudinal beam-coupling impedance was measured using a vector network analyzer (VNA) via the coaxial wire method. A satisfactory agreement was obtained between the numerical simulations and measurements. Based on the numerical simulation data, the loss factor was 0.01721 V/pC, and the effective impedance was 3.59 mΩ (σ=10 mm). The simulation of the heat deposition on each part of the kicker demonstrated that 84.4% of the parasitic loss of the beam was deposited on the metal strips, and the total heat deposition power on the kicker was between 113.3 W and 131.5 W. The obtained heat deposition powers can be considered as a reference for establishing the cooling system.

705