The Shanghai Synchrotron Radiation Facility (SSRF) is a user facility that requires continuous addition of new beamlines to meet the needs of an increasing number of users. Adding new insertion devices (IDs) to the synchrotron radiation light source is a complex and critical task.

This study aims to highlight the important considerations of dual IDs installation and commissioning when adding new beamlines to synchrotron light sources.

The newly added dual IDs 04IVU (undulator) and 04Wigger for new beamline added to SSRF were taken as an example, key tasks that need to be addressed in the accelerator aspect of engineering were presented in details. Firstly, the design parameters and magnetic measurement results of the IDs were introduced, and the SPECTRA program was employed to calculate the spectral brightness of dual IDs. Then, problems encountered during the installation process and their solutions were discussed, and an orbit feedforward compensation system equipped with corrector coils for mitigating orbit distortions caused by the IDs was implemented. Finally, the significance, methods, and results of vacuum cleaning work in the front-end area, together with a summary of the issues encountered during the trial operation and corresponding solutions were outlined.

The maximum spectral brightness of 04IVU and 04Wiggler are 5.86×10¹⁹ Photon·s^-1·mm^-2·mrad^-2·(0.1% B.W.)^-1 and 2.75×10¹⁵ Photon·s^-1·(0.1% B.W.)^-1 at photon energy of 3 keV, respectively. After compensation, the distortions of 04IVU and 04Wiggler are reduced to below 2 μm.

The dual IDs have been successfully installed and commissioned. This study provides reference value for installation and commissioning of accelerators associated with the new beamline in other synchrotron radiation light sources.

Full-field transmission X-ray microscopy (TXM)–X-ray absorption near-edge structural (XANES) (TXM-XANES) is an imaging method that combines TXM and XANES. By measuring the TXM images of multiple energy points before and after the K-edge of the element of interest, the distribution of elemental chemical states in the sample can be determined. Conventional TXM-XANES data requires the acquisition of images and background images at each energy point, which results in a large data volume and extended acquisition time. At the nanoscale, the instability of the mechanical structure and the movement of the sample may impact the TXM-XANES data analysis.

This study aims to use machine learning methods to achieve background-image sequence prediction modeling using only two spectral background images to reduce the data volume and shorten the acquisition time.

Machine learning, polynomial regression, and linear interpolation were used to generate background image sequences. A prediction model of the complex linear relationship between image grayscale values, pixel points, energy, and other related features based on the known data was established. Subsequently, the entire background image sequence could be predicted using only two spectral background images. Finally, 2D energy distribution maps obtained by conventional TXM-XANES method and this improved TXM-XANES method for standard powder samples and lithium battery cathode material sample were compared and analyzed in details.

The proposed method achieves complete background-image sequence prediction modeling using only two spectral background images. The comparison results show that the proposed method requires a lower data volume and shorter acquisition time than the conventional TXM-XANES methods, which can significantly improve the experimental efficiency of TXM-XANES.

This study addresses the issues of prolonged data gathering time and poor experimental efficiency in TXM-XANES by developing a machine learning model that builds complex linear relationships between pixel values and related features, such as location and color, using machine learning. Using the two TXM-XANES background images for full-sequence background prediction achieves rapid prediction of the entire background image sequence.

Plutonium is an important element for nuclear energy production and radioactive waste disposal, and evaluating its species distribution in natural water systems is essential for investigating its migration behavior. Recently, with the advancements in related research, some new plutonium species have been discovered and confirmed, hence previous related research is now inadequate for accurately describing the species distribution of plutonium in solutions.

This study aims to understand the speciation distribution of plutonium in different water composition systems.

The geochemical calculation software PHEEQC was employed to systematically evaluate the effects of the pH value and coexisting ion concentration on the species distribution of plutonium. The plutonium species proportion in different natural water systems was estimated in according with the latest thermodynamic data embedded into PHEEQC software.

The results reveal that hexavalent plutonium in oxidized groundwater with low hardness mainly exists as PuO₂²⁺ or PuO₂CO₃ under acidic conditions, whereas PuO₂(CO₃)₂^2- or PuO₂(CO₃)₃^4- dominate under neutral or alkaline conditions. Although PuO₂²⁺ and PuO₂CO₃ are the main species of plutonium in acidic environments, CaPuO₂(CO₃)₃^2- is the dominant species under neutral or basic conditions whereas the calcium concentration is high in the solution.

Therefore, the hardness of water (particularly, the calcium concentration) can be concluded to be among the important factors affecting the species of plutonium and must be carefully considered in the geological disposal of plutonium.

An electrolyte waste salt containing LiCl and various products is generated during the pyroprocessing of spent nuclear fuel in metal fast reactors. Separating metal impurities from waste salt can purify molten salt, facilitate salt recycling, and reduce the amount of waste salt, achieving waste minimization.

This study aims to investigate the effects of key factors on the application of the cold finger crystallization method used for removal of Sr and Ba from molten LiCl salt.

A homemade cold finger experimental apparatus was applied to the experimental removal of two alkaline earth metals, Sr and Ba, from molten LiCl salt, and Fluent software was employed to simulate the application of cold finger crystallization equipment during dry reprocessing. The effects of crystal growth time, initial crystallization temperature, and initial SrCl₂/BaCl₂ concentrations on the removal ratio of the crystalline salt during the process were analyzed.

The initial temperature of molten salt is a critical factor that influences cold finger separation efficiency. When the initial temperature reaches 660 ℃, the removal efficiency improves. Moreover, when the impurity contents of Sr and Ba in molten salt are lower than 0.55%(w/w), the removal efficiency of the cold finger crystallization method can exceed 80%. Further analysis shows that the removal effects of different parts of molten salt crystals differ. The solvent salt at the top of the molten salt crystal is better, and the removal ratio of the bottom and inner salts is lower. Therefore, the optimal conditions for removing Sr and Ba from LiCl crystalline salt require an initial temperatures of 660~670 ℃, an airflow intensity of 10 L·min^-1, and a growth time of 20 min. Under these optimal conditions, the removal ratio can reach 90%.

The proposed approach is feasible for purifying solvent salts from electrolyte waste molten salt via cold finger crystallization. This study provides a reference for purifying waste salt and reusing molten salt.

Extraction of carbon from water is a crucial preprocessing step for measuring ¹⁴C in environmental waters using liquid scintillation spectrometry.

This study aims to explore the optimal technological conditions for extracting carbon from water using wet oxidation method.

A wet oxidation system combining sodium persulfate and Fenton's reagent, along with phosphoric acid acidification and nitrogen bubbling, were employed for the wet oxidation carbon extraction experiments on two types of water samples with known (deionized water + sucrose) and unknown carbon components, each with a volume of 10 L. Simultaneously, carbon extraction experiments were conducted on the water samples having unknown carbon component, using a combination of wet oxidation and 185 nm ultraviolet (UV) oxidation so as to determine the optimal timing and sequence of reagent addition, as well as the optimized reagent dosage and ratio. Further experiments under optimized conditions were conducted to obtain more results for deep analysis.

Under the optimized conditions, after a 3-h reaction at 90 °C, the organic carbon extraction rate for the known carbon component (deionized water + sucrose) exceeds 96%. The total carbon extraction rate from the unknown carbon component water is (96.8±0.3)%, with an inorganic carbon extraction rate >98.5%, and an organic carbon extraction rate of (93.4±0.2)%, while the oxidation rate of tannic acid-type organic compounds is only (88±0.2)%. After the combination of wet oxidation and 185 nm UV oxidation, the total carbon extraction rate for the unknown carbon component increases to (98.3±0.5)%, with an inorganic carbon extraction rate ≥99% and an organic carbon extraction rate that can reach (95.6±1.4)%.

Results of this study indicate that wet oxidation alone cannot represent the carbon recovery rate in actual water samples using typical organic compound carbon recovery rates. The combination of wet oxidation and 185 nm UV oxidation proves to be a more effective method for carbon extraction from water.

During the data acquisition of an extreme ultraviolet (EUV) spectroscopic diagnostic system in experimental advanced superconducting Tokamak (EAST), significant amounts of one-pixel noises are consistently observed. This is attributed to the influence of hard X-ray on the charge coupling device (CCD) detector.

This study aims to detect and denoise spectral images in the EUV spectral image processing system based on the field programmable gate array (FPGA).

First of all, based on limiting filtering algorithm, spectral image processing was optimized by replacing fixed limiting thresholds and sample deviations using parameters such as standard deviation and deviation from the mean, and Andor Solis software to was applied to converting the SIF format spectra to BMP format spectral images. Then, data discrimination method was combined with limiting filtering algorithm to process spectral image data in stages according to the setting working area of the algorithm. Finally, a simulation test module was designed to process the video data converted from EUV spectral images in AX7Z100 ZYNQ FPGA platform, simulating the actual acquisition process for functional testing of the system. To assess the system's capacity to protect effective spectral data, the image data was transferred to one-dimensional spectral data for comparative analysis.

Based on the experimental results, the EUV spectral image processing system of this study can effectively eliminate noise data points in the spectral image while essentially maintaining the integrity of the spectral data.

This study enhances the processing of the spectral data and provides a new technological path for EUV spectral image processing.

Detectors based on the third-generation semiconductor material silicon carbide (SiC) offer several important advantages, such as compactness, faster charge-collection times, and easier n/γ identification, and they are widely used in reactor core dose monitoring.

In this study, the n/γ signal amplitude, neutron fluence rate, and linear response calibration performances were tested systematically for a self-developed third-generation SiC semiconductor detector.

Firstly, the neutron conversion layer material ⁶LiF (with a 95% abundance of ⁶Li) was sprayed onto a SiC substrate using electron beam evaporation vacuum coating technology to achieve the optimized thickness of 25 μm for the self-developed third-generation SiC semiconductor detector. Then, ²⁴¹Am α radioactive source (activity 9.37×10³ Bq) was used to observe α particle response signal amplitude, and γ response testing of radiation was conducted in the ¹³⁷Cs γ source (activity 6.23×10⁷ Bq) environment. In addition, the SiC detector's neutron flux response linearity, γ dose rate response linearity and calibration of neutron fluence rate response linearity were measured in the standard radiation field systems.

The measurement results show that the SiC semiconductor detector has a linear fit of R2 = 0.996 9 in the neutron fluence rate range of 1×10³~1×10⁶ cm^-2?s^-1, with a good linear response, and the response range of the neutron/gamma dose is 0.005~20 Gy?h^-1.

The SiC detectors with such good n/γ performance can be used for real-time and accurate monitoring of neutron and gamma doses in nuclear power field reactors.

The silicon photomultiplier (SiPM) is sensitive to environmental noise, its performance is greatly affected by ambient noise.

This study aims to design a negative-feedback selective amplifier circuit for SiPM coupled plastic scintillator detector to reduce the noise and improve the overall performance of SiPM.

It is compared with the traditional OPA657 transimpedance feedback amplifier circuit. The circuit consisted of an RC filter input and an integrated operational amplifier AD8014 with advantages of a high gain and low input noise. The CR high-pass filter circuit was used as the comparator signal input to further filter out signal noise and prevent signal reflection from interfering with the amplifier. The experimental circuit is simulated using Micro-cap12 to obtain the relevant circuit parameters. Finally, the dark noise level and signal consistency of a ¹³⁷Cs source at room temperature was record, and performance of this amplifier circuit for SiPM coupled plastic scintillator detector was compared with that of the traditional OPA657 transimpedance feedback amplifier circuit. [Results and Conclusions] Comparison results show that the proposed circuit effectively filters out ambient noise and exhibits a fast rise time. The output pulse rise time is found to be less than 12 ns, and the dark noise level is observed to be less than 30 mV, which are better than those of the transimpedance amplifier circuit.

The use of neutron-based methods to locate radioactive sources within sealed containers holds great practical significance.

This study aims to locate an AmLi source within the detection space of four position-sensitive neutron detectors.

First of all, the Monte Carlo method was applied to designing the moderating shield of the detector. Then, a delay circuit was added to one end of the detector hence the position coordinate of the source y-axis (detector axis) was determined according to the time difference between the two ends of the detector to detect the source neutron signal, and the axial position function of each detector was calibrated. Finally, the detector was used to build a measurement space around sealed container, and the position coordinates of the x-axis and z-axis (the other two directions) were determined by the ratio of the neutron count rate of the two adjacent detectors, so was the function calibration. During the measurement of neutron point-source 3D coordinates, the detector with the largest count rate was first selected to determine the axial coordinates of the source, and then the coordinates of the other two directions of the source were determined according to the ratio of the count rate of the two adjacent detectors to the detector, so as to realize the location of the source.

Measurement results of five different positions of the point source in the detection space show that the positioning deviation on each coordinate axis is within 1.5 cm, and the relative standard deviation of neutrons measured in this detection space is within 1%.

This methodology effectively demonstrated the feasibility of employing neutron position-sensitive detectors to precisely locate radioactive sources, establishing a strong foundation for future endeavors aimed at accurately determining the positions of nuclear materials within processing equipment in nuclear facilities.

Self-powered neutron detectors (SPNDs) are critical devices in the monitoring and protection systems of nuclear reactors, and their signal current directly reflects the value and distribution of the core power. Insulators play an essential role in the design of SPNDs and are the main factor affecting the calculation accuracy of the signal current.

This study aims to improve the accuracy of the calculation method of the SPND signal current, ensuring that the measured currents accurately reflect the reactor conditions and meet the highest industrial standards.

Firstly, the signal generation mechanism of the SPND was thoroughly discussed, and three independent calculation methods of the current based on the inherent physical characteristics of the space electric field of an insulator were proposed. Then, high-fidelity simulations of the SPND were performed using the Monte Carlo code, and the three methods were validated based on the simulation results. In addition to the current caused by the neutrons, the current caused by the photons inside the reactor was quantitatively analyzed. Meanwhile, extensive radiation experiments on the various reactors have been performed to verify these three current calculation methods.

The difference between the results obtained by using the three methods is less than 1%, demonstrating a considerable accuracy. In addition, the current of the rhodium SPND is primarily owing to the neutrons, whereas the photon-induced current is generally less than 5%. Experimental verification results on the several operating reactors show that the difference between the theoretical and experimental results is less than 3%, which also proves its effectiveness and accuracy.

This method has been applied to the large Chinese Gen-III advanced pressurized water reactor (HPR1000) and is universal. It can be used for the signal analysis of different types of SPNDs, as well as for providing valuable references for core monitoring systems in other reactors, such as the Gen-IV fast reactor as well as future fusion reactors.

Nuclear isomers are crucial in cosmic element synthesis and have potential applications in controlling nuclear energy release. Specifically, Europium (Eu) is significant in fundamental studies. For instance, ¹⁵²Eu is used as a reference source for radioactive experiments, and its isomeric state ^152m1Eu has a probability of 73% to produce cosmological p-nuclei ¹⁵²Gd with β^- decay. Therefore, ^152m1Eu is a crucial nuclide in the nuclearsynthesis of p-nuclei ¹⁵²Gd.

This study aims to realize the efficient excitation of ^152m1Eu with a bremsstrahlung source generated by laser plasma.

Firstly, the laser-plasma bremsstrahlung source was utilized to achieve the efficient excitation of ^152m1Eu (45.6 keV, T_1/2=9.31 h) in the experiment with yields of 8×10⁴ particles/shot by this isotope. Then, numerical simulations of the yield of ^{152m1, m2}Eu were performed using the Geant4-GENBOD program to get generation time, and peak excitation efficiency evolution with electron temperature.

The results demonstrate that when the electron temperature reaches 15 MeV, the yield of ^{152m1, m2}Eu approaches saturation. When the incident electron charge is 17.6 nC, the yield of ^152m1Eu is approximately 8×10⁶ particles/shot, and that of ^152m2Eu is approximately 2×10⁵ particles/shot. The generation time of ^{152m1, m2}Eu in the target is approximately 32 ps. When the electron temperature reaches 15 MeV, the peak excitation efficiency of ^152m1Eu is expected to be ~10¹⁷ particles/s, and that of ^152m2Eu is expected to be ~10¹⁶ particles/s.

The ultrashort ultrahigh intensity laser technology can significantly enhance the excitation efficiency of isotopes of the same nucleus, and this will provide an important research avenue for the study of cosmic element synthesis and nuclear energy release control applications.

The reactor period will dramatically decrease at the beginning of reactivity insertion in the nuclear reactor, which may trigger the protection system of the reactor period and lead to unnecessary shutdown. The instantaneous short reactor period is influenced greatly by the inserting rate of reactivity, but also related with the present delayed neutron precursors, which is difficult to quantify.

This study aims to explore the relationship between the instantaneous short reactor period and the inserting rate of reactivity from a theoretical perspective.

A point reactor model was used to deduce the inserting rate of the reactivity function using the variable factors of reactivity, reactor period, and reactor dynamic parameters, with some conservative assumptions to omit the effect of delayed neutron precursors. The relationship between reactivity insertion rate and transient period of reactor was derived after analysis on the short period phenomenon. Then, the formula of relationship was verified for several transient cases.

The results show that the reactor periods are all larger than the aim reactor periods for all transient cases when using the rate constraint of reactivity insertion in the aforementioned formula. According to the proposed theoretical framework, unnecessary shutdown during an instantaneous short reactor period can be avoided.

A theoretical framework proposed in this study can be applied to the control of rod withdrawal rate during the operation of nuclear reactors.

Passive residual heat-removal system (PRHRS) based on natural circulation has been widely used in small reactors connected on secondary side loop.

This study aims to develop and analyze a passive residual heat-removal system on the secondary side of a small reactor to improve reactor safety.

Based on the completed heat-transfer experiment of the intermediate circuit of a small integrated nuclear power plant, Reactor Excursion and Leak Analysis Program (RELAP) was employed to determine and analyze the natural circulation characteristics of the intermediate loop were determined and analyzed.

The heat transfer rate results of the program are in good agreement with the experimental data, and the natural cycle characteristics of PRHRS can be characterized. The pressure of the system loop is determined by the average temperature of the primary side of the steam generator (SG), and the difference in the inlet temperature of the SG primary side, mass flow rate, and height of the cooling and heating sources significantly influence the heat-transfer performance of the SG system. The heat-transfer performance of the waste-heat-removal system is more sensitive to the resistance of the system loop when the temperature of the primary-side inlet of the SG is higher.

These results provide a valuable application for further investigations of passive systems in small reactors.

LiF-UF₄ and LiF-ThF₄ are used as addition salts in thorium-based molten salt nuclear reactors. Monitoring the product quality during the preparation of molten salts necessitates the analysis of the contents of the main metal elements in LiF-UF₄ and LiF-ThF₄, namely, lithium, uranium, and thorium.

This study aims to establish effective, rapid analysis methods for determination of primary metal elements in LiF-UF₄ and LiF-ThF₄ molten salts.

Firstly, the LiF-UF₄ samples were treated with nitric acid and hydrogen peroxide whilst the LiF-ThF₄ samples were dissolved in aluminum nitrate. Then, inductively coupled plasma atomic emission spectrometry was used as rapid analysis methods for measuring these two molten salts, and manganese was employed as the internal standard element to reduce the effect of signal drift.

In the analytical method of LiF-UF₄, the recoveries of Li and U are detected to be 99.6%~102.4% and 99.6%~101.8%, respectively. The relative standard deviations (RSDs) of Li and U are 0.2%~0.7%, and 1.1%~2.0%, respectively. In the analytical method of LiF-ThF₄, the recoveries of Li and Th are detected to be 99.6%~102.3% and 99.6%~102.4%, respectively. The relative standard deviations of Li and Th are 1.9%~2.0%, and 0.3%~0.4%, respectively.

The proposed methods are simple, time-efficient, accurate, and suitable for rapid analyses of large numbers of samples.

Small rod-controlled pressurized water reactors have foregone the use of soluble boron and heavily rely on control rods and burnable poison rods for reactor control.

This study aims to explore the influence of control rods on the key performance metrics of a long-term small rod-controlled pressurized water reactor.

First, a KLT-40 reactor used for nuclear icebreakers was taken as research object, and a critical rod position-search burnup code was developed based on OpenMC. Then, the core lifetime and other indicators such as the axial power offset, fuel utilization, and radial power peak factor, were compared between with and without the designed control rods for the design and analysis of the control rod layout of KLT-40 reactor. Finally, the influence of different move-in/out strategies on axial power offset was analyzed.

The core lifetime can be extended from 590 effective full power days (EFPDs) to 650~698 EFPDs with the designed control rods. Adopting a strategy of prioritizing the movement of low-value rod groups effectively reduces the axial power offset, with values of -0.69 and +0.8 decreasing to -0.29 and +0.52, respectively.

The control rod burnup calculation strategy adopted to accurately calculate the core lifetime of small rod-controlled pressurized water reactors can effectively reduce the axial power offset by using a reasonable move-in/out strategy.