As a radioactive nuclide activity detection technique with advantages such as high sensitivity, high detection efficiency, and simple operation, liquid scintillation measurement is widely used for measuring the activity of low-energy nuclides (e.g., ¹⁴C, ³H, and ⁵⁵Fe) in samples from the atmosphere, water bodies, soil, and biological specimens. During the measurement process, interference from background events (e.g., muons) leads to inflated results, thereby affecting the final analysis. To address the above problem, this paper proposes a dual-channel signal coincidence method to eliminate muon signals from background events. This method leverages the favorable signal time-preserving characteristics of fast-response photomultiplier tubes (PMTs). It marks the β signal output from the last dynode of the fast-response PMT and applies coincidence rejection to the muon signal. The marked β signal controls the switching of a gate, enabling the gating of the β signal output from the PMT anode. Experimental verification was conducted using ¹⁴C liquid scintillation samples. The results show a significant difference in the decay times between muon signals and β signals. The typical decay time for muon signals is 154.4 ns, while for β signals it is 41.6 ns. Specifically, muon signal decay times exceed 80 ns, whereas β signal decay times fall within the 10~80 ns range. The proposed method effectively eliminates muon signals. This research can serve as a reference for the accurate measurement of portable low-energy β nuclide activity.

Liquid scintillators, composed of organic solvents, scintillating solutes, and phase shifters, offer advantages such as strong neutron/gamma-ray (n/γ) resolution capability, high detection efficiency, and excellent stability. In this study, three chemically distinct scintillator solutes (PPO, KCB, and BBOT) were selected to prepare corresponding liquid scintillators. Systematic measurements of ultraviolet absorption spectra, fluorescence emission spectra, scintillation count rates, and n/γ discrimination performance were conducted. Molecular simulations and experimental measurements were employed to investigate the underlying mechanisms. Results indicate that scintillation counting rates and n/γ discrimination performance reach maximum values when the solute contains strong electron-donating groups, a high hydrogen atom ratio in transition atoms, and transition groups containing N or O atoms. These findings provide valuable guidance for further optimizing the counting sensitivity and n/γ discrimination efficiency of liquid scintillators.

Thirty cases of computed tomography (CT) localization images of patients with colorectal cancer undergoing radiotherapy were selected. The CT values of air cavities within the planning target volume (PTV) were modified in the treatment planning system (TPS), and models with different volume ratios were constructed. The treatment plans were transferred to the modified images, and the dose distributions were calculated. The dose parameters (D_max, D_mean, D_98%, D_50%, D_2%, conformity index CI, homogeneity index HI) of the PTV and the dose changes of organs at risk were evaluated. Paired sample t test or Wilcoxon signed rank test was used to analyze the differences between groups, quantify the influence of changes in the CT values and volume ratios of intestinal air cavities on dose distribution, and establish risk warning thresholds. The results showed that an increase in the CT values of air cavities led to a significant decrease in D_98% of the PTV, with the average relative deviation expanding to -1.215%, while D_2% remained relatively stable. CI and HI increased significantly (P<0.05). Except for the Dmean of the small intestine, there were no statistically significant changes in the doses of other organs at risk (P>0.05). There was a critical threshold for the synergistic effect of CT values and volume ratios: when the CT value of the air cavity was ≥250 HU and the volume ratio was >6%, the maximum relative deviation of D_98% increased to -4.927%. Therefore, when both reached the thresholds simultaneously, the coupling of dose algorithm distortion and volume effect could result in clinically unacceptable cold spots. Risk stratified management should be established: for high-risk patients (those reaching the thresholds), comprehensive interventions (diet control, electron density correction) should be implemented, and the changes in air cavities should be dynamically monitored through cone beam CT (CBCT). When the volume ratio of air cavities within the PTV was >6% and the CT value was ≥250 HU, adaptive radiotherapy should be initiated.

In response to the requirement of special conditioning for end fittings and spent cladding in the spent fuel reprocessing process, this paper clarifies the core functional requirements of the metering and filling equipment based on the overpressure-based volume reduction conditioning technical process: separation and separate filling of end fittings and spent cladding, accurate metering, lid handling (removal and closing), and multi-station transfer of compaction canisters. Combined with the design principles of non-standard equipment,a system comprising a metering separator, a rotary table, a lid handling device, and a control system was designed. The complete working process follows: “empty canister supply → lid removal → layered filling (cladding-end fittings-cladding) → lid closing → transfer.”Through the dumping parameter test of the circulation bucket, the operation parameter test of the metering separator, and the equipment linkage test, the key operating parameters were determined: dumping speed of the circulation bucket at 0.015~0.08 r/min (regulated in intervals), drum speed at 0.10 r/min, spiral coil speed at 1.0 r/min, and turntable rotation speed at 0.25 r/min. These parameters achieve the index requirements of a single canister filling time of ≤20 min, a filling rate of ≥80%, and a cladding metering deviation of ≤±1 kg. Finally, a comprehensive metering and filling treatment scheme for end fittings and spent claddings is formed, providing a technical reference for the design of similar reprocessing equipment for spent fuel assemblies.

Phytoremediation has been proposed due to its characteristics such as in-situ remediation, ease of operation, low cost, and environmental friendliness. The key to phytoremediation technology lies in screening suitable hyperaccumulator plants. This study employed methods including field investigation and sampling, indoor potted plant simulation screening, and field planting experiments to rank the uranium concentration factor (F_V) and translocation factor (f_tr) of candidate plants. The results showed that field investigation and sampling identified Phragmites australis and Themeda caudatahad as having F_V>1, making them potential plants for ecological restoration in severely uranium-contaminated areas. The pot experiment screened six uranium hyperaccumulator plants (F_V>1), namely Bidens pilosa, Abelmoschus esculentus, Eleusine indica, Solanum nigrum, Commelina communis and Lolium perenne, while Amaranthus retroflexus had F_V<1 but f_tr>1. The field planting experiment results indicated that Eleusine indica, Sorghum sudanense and Brassica juncea had F_V>1 and f_tr<1, whereas Arachis hypogaea had F_V<1 and f_tr>1, making them candidates for uranium phytoremediation research. Combining the three methods, a total of ten hyperaccumulator plants for the radionuclide uranium (F_V>1) were identified: Phragmites australis and Themeda caudatahad, Bidens pilosa, Abelmoschus esculentus, Eleusine indica, Solanum nigrum, Commelina communis, Lolium perenne, Sorghum sudanense and Brassica juncea. It is anticipated that future efforts involving genetic engineering, breeding, and related agronomic management techniques will enhance the remediation potential of these ten plants, as well as Amaranthus retroflexus and Arachis hypogaea.

Cement powder, fly ash, slag powder, and lime were used as curing materials to immobilize radioactive monazite waste. A 4-factor 3-level orthogonal experiment was conducted to study the variation patterns of unconfined compressive strength, uranium (U) and thorium (Th) leaching rates, freeze-thaw resistance, and acid neutralization capacity under different mix ratios. The optimal curing ratio was selected through fuzzy optimization theory, with curing mechanisms analyzed via XRD, FTIR, and SEM. Experimental results demonstrated that the slag-to-curing material ratio had the greatest impact on unconfined compressive strength and freeze-thaw resistance, while fly ash dosage significantly affected U leaching toxicity. All factors showed similar impacts on acid neutralization capacity, whereas Th leaching toxicity remained relatively unaffected. Using unconfined compressive strength, U leaching rate, freeze-thaw cycles, acid neutralization capacity, and curing cost as fuzzy optimization indicators,It is concluded through the fuzzy optimization that when the content of fly ash is fixed at 15%, the content of slag is in the range of 15%~25%, the content of lime is in the range of 2.5%~5.0%, and the slag-solid ratio is in the range of 1.0~1.4, the solidified body meet the requirements specified in Performance Requirements for Solidified Forms of Low and Intermediate Level Radioactive Waste-Cement Solidified Forms (GB 14569.1—2011)with a reasonable treatment cost.Post-curing treatment resulted in pore elimination, structural densification, and enhanced strength in the monazite waste solidification body.

To meet the stringent requirements for precise prediction of radioactive pollutant dispersion in nuclear facility regions, this study investigates the optimization of simulation parameterization schemes for multi-scale atmospheric flow fields. A numerical model was developed based on three-dimensional non-hydrostatic fully compressible equations to systematically evaluate the applicability of 192 parametric combinations across three typical terrains (inland flat, coastal flat, and coastal complex terrains). High-precision topographic data and land use characteristics from representative domestic nuclear facility sites were selected, with the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis data serving as the initial field. Multi-scale nested simulations were performed using the RAMS regional atmospheric model. The validity of the simulation results for various parametric schemes was verified using metrics such as the root mean square error (RMSE) of wind speed and the mean absolute error (MAE) of wind direction. The findings indicate that for shortwave radiation schemes, the Mahrer/Pielke scheme is recommended in coastal mid-to-low latitude areas, while the Chen scheme is more suitable for inland flat regions. Among planetary boundary layer schemes, the Cyclic scheme effectively mitigates lateral boundary effects.

Estimation of radon exposure dose is a main component of internal radiation dose assessment, in which the dose conversion factor (DCF) serves as a key parameter. This study focuses on Taurus, the latest internal radiation software released by the UK Health Security Agency, and investigates and validates its application in calculating DCFs. First, by comparing the differences in calculating the deposition fractions of radon progeny in the respiratory system between Taurus and the previously widely used internal radiation software LUDEP and IMBA, it is found that the primary cause of these differences lies in the distinct respiratory tract models employed by each software. Second, Taurus is utilized to calculate DCFs for each of the five progeny of ²²²Rn and ²²⁰Rn under various conditions, such as different particle size distributions. The results indicate that the DCF for ²²⁰Rn progeny is approximately six times higher than that for ²²²Rn progeny, and the contribution of unattached radon progeny to the DCF is greater than that of attached radon progeny. Finally, Taurus is applied to calculate a series of DCFs in typical indoor and outdoor environments. The results, which show a high consistency with the DCFs in the International Commission on Radiological Protection (ICRP) Publication 137, demonstrate that Taurus not only offers comprehensive functionality and a high degree of flexibility in selecting input parameters but is also aligned with the latest ICRP database in terms of respiratory tract models, gastrointestinal tract models, and related biokinetic parameters.

During the operation of a nuclear power plant, it is necessary to measure the neutron flux distribution in the reactor core. As components related to neutron flux measurement enter fuel assemblies, where fission reactions occur and the components themselves become activated, there exists an extremely high and complex risk of unplanned radiation exposure to personnel. From 1997 to 2024, several serious unplanned radiation exposure incidents related to neutron flux measurement have occurred in the industry. Taking the M310 reactor type as the reference, this paper conducts a detailed risk analysis based on the operational process of neutron flux measurement. By combining the failure causes of unplanned radiation exposure incidents in the industry, and on the basis of optimizing general control and prevention measures for nuclear power plants, this paper further applies the principle of defense-in-depth and proposes an innovative method of “using physical barriers and interlocks to compensate for potential human errors”. This method has been applied for the first time in the M310 reactor type. The risk analysis and control measures described in this paper can serve as a reference for domestic reactor types evolved from the M310, such as CPR1000, CNP600, and CNP1000, to prevent the recurrence of similar incidents and protect personnel safety.