Nuclear Radiation Field Research Articles

Application of data partitioned Kriging algorithm with GPU acceleration in real-time and refined reconstruction of three-dimensional radiation fields

Accurately assessing personal radiation doses in real radiation environments like nuclear power plants requires precise and real-time reconstruction of three-dimensional radiation fields. The Kriging algorithm, known for its accuracy in spatial interpolation, provides a promising approach for this task. However, its computational demands can be significant, especially in real-time scenarios. To address this, we enhance the Kriging algorithm with GPU acceleration and data partitioning strategies, enabling efficient and accurate reconstruction of three-dimensional nuclear radiation fields. Using Fluka software for Monte Carlo simulations, we generated a virtual radiation field of dimensions 5 m × 5 m × 5 m for a single-source, unshielded scenario, and a field of dimensions 20 m × 6 m × 8 m for a multi-source, shielded scenario. Using the simulated data, we compared the prediction accuracy of the improved algorithm with the conventional Kriging algorithm and further explored factors influencing the acceleration ratio of the improved algorithm. The results indicate that the GPU-accelerated and data-partitioned Kriging algorithm achieves nearly identical accuracy compared to the traditional method. In the single-source, unshielded scenario, with more than 343 known (measurement) points and predicting 95×95×95= 857,375 points, the prediction accuracy remains above 92.25%. In the multi-source, shielded scenario, with more than 8000 known (measurement) points and predicting 95×95×95= 857,375 points, the prediction accuracy remains above 91.17%. The acceleration performance of the improved algorithm is consistent across both scenarios, with the acceleration ratio increasing as the number of known and predicted points grows, reaching approximately 20 for smaller datasets and up to 93 for larger datasets. Additionally, the acceleration effect of the improved algorithm varies with data partition size, initially increasing and then decreasing as the partition size increases. When the number of known points is 512 and the number of predicted points is 884,736, the optimal partition size lies between 80,000 and 90,000, resulting in a prediction time of only 0.24 s.

Calculation method of particle angular distribution based on directional probability approach in the Monte Carlo simulation

Abstract To address the limitations of narrow applicability and low computational efficiency in the existing methods for calculating particle angular distribution using Monte Carlo simulations, this paper proposes a method based on the directional probability approach. In this method, when calculating the fluence at a recording point using the directional probability approach, virtual particles are binned based on the cosine of the angle between their direction and different reference directions, enabling statistical calculation of the particle angular distribution at the recording point. The simulated one-dimensional angular distribution of particles at the recording point agrees well with the angular distribution at the recording surface, with a total fluence deviation of less than 2% and an angular distribution deviation of less than 5%. Additionally, to facilitate the coupling of particle transport simulation with other physical fields, corresponding methods have been established to statistically calculate the fluence components in different directions of the xyz coordinate system. This method can calculate one-dimensional, two-dimensional angular distributions, and different directional components of particles at any location within the radiation field, providing technical support for research in ray detection, radiation protection, nuclear radiation field analysis, and nuclear data evaluation.

Surrogate Model of Solved Poisson Kriging Method for Radiation Field Reconstruction

Reverse reconstruction methods for the radiation field do not require information on the radioactive source and are capable of constructing the radiation field using a small amount of monitoring data, showing huge significance for radiation protection. However, in previous studies, inverse reconstruction methods have given less consideration to variations in the time dimension. Herein, the principle of the Poisson Kriging method solved by the surrogate model has been analyzed, and the Poisson Kriging method has been applied to the inverse reconstruction of two-dimensional radiation fields at different moments. On this basis, this work also investigated the effects of the principal function and correlation coefficient model on the objective function, the results of which demonstrate that the quadratic polynomial principal function and the Gaussian model correlation coefficient have good stability and convergence. Compared with the inverse distance weighting methods and the radial basis function methods, the Poisson Kriging method has smaller errors, showing that it is more suitable for reconstructing complex radiation fields. Finally, the Poisson Kriging method was applied to the Fukushima nuclear accident radiation field calculation. The Pearson correlation coefficient of its results was r = 0.49, reflecting the validity of this method. Our work provides a calculation method for the spatial distribution and trend of the radiation field in the early stages of a nuclear accident, which is helpful for furthering radiation protection and emergency responses to nuclear accidents.

Mechanical Properties, Radiation Resistance Performances, and Mechanism Insights of Nitrile Butadiene Rubber Irradiated with High-Dose Gamma Rays.

The radiation effect of materials is very important and directly related to the safety and reliability of nuclear reactors. Polymer materials, one of the indispensable materials in nuclear power equipment, must withstand the ordeal of high-energy ionizing rays. In this work, through screening different γ-ray dose irradiation conditions, we systematically and comprehensively study the changes in the structure and properties of nitrile butadiene rubber (NBR) before and after γ-ray static irradiation at a high dose rate, and master the rule and mechanism of the γ-ray static irradiation effect of these polymer materials. The mapping relationship between the macroscopic properties, microstructure, and irradiation dose of NBR is accurately characterized. With an increase in total irradiation dose, the C=C double bond reaction occurs, and the C≡N bond, C=C, and C=O participate in the hyper crosslinking reaction. The glass transition temperature (Tg) increases with the cumulative irradiation amount. With the increased total irradiation amount, the degree of rubber cross-linking increases, causing an increased crystallinity and decomposition temperature. A growing amount of gamma irradiation causes the mechanical properties of the rubber to degrade simultaneously, increasing the shore hardness while decreasing the tensile strength and ultimate elongation at break. When the cumulative amount reaches 1 MGy, the ultimate elongation at break decreases significantly. A cumulative dose of radiation resistance of 4 MGy can be achieved by the samples. This work can provide theoretical and experimental support for the long-term stability of nitrile butadiene rubber and its derivatives in nuclear radiation fields and space radiation conditions.

Impact of CdO on optical, structural, elastic, and radiation shielding parameters of CdO–PbO–ZnO–B2O3–SiO2 glasses

CdO–PbO-B2O3-SiO2–ZnO glasses were prepared by melt quenching methods with different compositions. Experimental and theoretical techniques examined their structural, optical, elastic and radiation shielding ability. It was found that the internal structural units such as BO4, BO3and nonbridging oxygens changed slightly with further additions of CdO. Moreover, the optical, elastic and radiation shielding properties of these glasses were changed with further CdO additions. In more detail, the density, packing density, Urbach energy, elastic parameters and radiation shielding ability decreased with additional CdO concentrations. In contrast, the optical band gap and dissociation energy increased with additional CdO concentrations. These behaviors of structural, optical, mechanical and radiation shielding ability were attributed to the structural changes produced due to replacing PbO by CdO. Despite the decreased behavior of radiation shielding ability with CdO additions, the half-value layer of all glass samples is compared to standard and well-known shielding materials. From this comparison, we found that, all glass samples are better than the standard and well-known shielding materials. Furthermore, we concluded that, our glass samples could be used in the nuclear radiation fields as effective shields.

Commissioning and Performance Evaluation of Varian TrueBeam Linear Accelerator

Aim: The aim of this study is to present a report on the commissioning results of the Varian TrueBeam machine with available photon energies so that it can benefit medical physicists during the entire commissioning process. Subjects and Methods: All tests were performed as per the recommendation of the Atomic Energy Regulatory Board. The beam profiles and percentage depth dose of both photon and electron beams were measured with Sun nuclear Radiation Field Analyzer and 0.125 cc ionization chamber. Output accuracy and consistency of photon and electron beams were measured using 0.6 cc cylindrical ionization chamber and 0.350 cc parallel plate ionization chamber, respectively. To measure the congruency of radiation and optical field and isocenter check with respect to gantry, collimator, and couch, self-developed films were used. Results: Isocenter shift due to gantry, collimator, and couch, rotation was found to be within ± 2-mm diameter circle. Congruency of optical and radiation fields was measured for symmetric fields 5 cm × 5 cm, 10 cm × 10 cm, 20 cm × 20 cm, and 30 cm × 30 cm for all available energy and was within ± 2 mm. Dosimetric leaf gap value for the multi-leaf collimator was measured with 0.125 cc ionization chamber and values are −0.853 mm, −1.106 mm, −1.097 mm, −0.765 mm, and −1.005 mm for energies 6 MV, 10 MV, 15 MV, 6 flattening filter free (FFF), and 10 FFF, respectively. Conclusions: All electrical, mechanical, dosimetric, and safety measurement were found to be within permissible limits. Before clinical use, the beam data are crosschecked with point dosimetry, portal dosimetry, and MapCHECK two-dimensional detector array and results are within tolerance.

Study of Effects of Atmospheric Humidity on Neutron Transportation and its Dose Field

Accurate calculation of neutron dose in the nuclear radiation field is of great significance to radiation detection, radiation protection, and radiation effect research. The distribution of neutron dose field can be affected by neutron spectrum, air density, and atmospheric humidity. In order to quantitatively investigate the influence of atmospheric humidity on the physical process of neutron transport and the distribution of neutron dose field, the Monte Carlo (MC) simulation model of neutron transport under different humidity conditions is presented in this article, and the parameters of neutron dose at different transport distances under typical humidity conditions for a scenario of an explosion of a nuclear device (ordinary hydrogen bomb) are calculated and analyzed. The quantitative relationship between the neutron dose and atmospheric water content under different mass distances is obtained. Based on this relationship, a fast-parameterized calculation method of neutron dose under different humidity conditions is presented. The relative deviation between the results of fast algorithm and MC simulation is within 8%. The results show that the neutron dose decreases with the increase of atmospheric water content at the same mass distance, and the change of atmospheric humidity can lead to a change of neutron dose up to about 10%–30%. For other types of nuclear devices, in which the source neutrons produced by them are different from that by hydrogen bombs, the influence of atmospheric humidity on the neutron dose field can also be studied by using the method presented here.

Characterization of a polyphenyl ether oil irradiated at high doses in a TRIGA Mark II nuclear reactor

Samples of a commercially available polyphenyl ether (PPE) oil are irradiated in the mixed neutron and gamma radiation field of the Pavia TRIGA Mark II reactor, at irradiation doses ranging from 0.78 MGy to 7.8 MGy. The oil is a nuclear grade product, whose radiation resistance reported in the product specification is based on cobalt-60 gamma irradiation data. The collection of additional data in a nuclear reactor radiation field performed in the present work, is motivated by the need to use this oil in neutron-rich environments such as targets and accelerators.The post-irradiation characterization of the oil samples here reported includes viscosity measurements, total acid number (TAN), Fourier transform infrared spectroscopy (FT-IR), gas chromatography (GC), gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy.The presented results evidence a remarkable increase of kinetic viscosity with the absorbed dose. Differences in the radiation-induced viscosity increase are observed comparing the data collected in mixed neutron and gamma radiation with the previous ones collected in cobalt-60 gamma radiation. This result emphasizes the need of further studies on the dependence of the radiation damage on different radiation environments. A negligible increase of TAN is reported. The FT-IR, GC, GPC and NMR show progressive polymerization with increasing dose. The increasing molecular size is in line with the viscosity data presented.

A Novel Method for Denoising the Image with Nuclear Radiation Noise

In the environment of severe nuclear radiation, remote operation often uses a camera to transmit pictures to the control room. Because the noise generated by the current electronic equipment under the interference of nuclear radiation is random and irregular, the traditional denoising methods cannot meet the requirement of denoising noisy image effectively. Aiming at this problem, a denoising method based on image restoration technology is proposed. Firstly, some representative images are intercepted from the video of actual nuclear radiation field as experimental objects. Then these images are smoothed to get the region A where the pixel difference between the noisy mage and the smoothed image is larger than the threshold and the region B where the pixel difference between the smoothed image and the clean image is greater than the threshold to form two regions to be restored. Finally, the process of image restoring is performed on the two regions respectively. The two images after restoration are fused to obtain the final image. The experiment shows that our method has good performance in protecting the details of the image while removing the nuclear radiation noise. Compared with other methods, our method can obtain a more clear image.

Inversion of radiation field on nuclear facilities: A method based on net function interpolation

In this paper, a novel method based on net function interpolation is proposed to reconstruct nuclear radiation field on the basis of the sparse observed data. In the grid space, the missing data of grid line is filled by means of constructing function. Then, the value of grid interior points is obtained by use of the net function interpolation method. To demonstrate the feasibility of the proposed method, the simulation experiment concerning a single point source is carried out. Compared with the simulation results of Monte Carlo method, the calculation results perform well. To make the simulation environment real, another experiment with multiple volumetric sources is done. The inversion results are also satisfactory. What's more, as the sampling data increases, the degree of reduction is further improved. It is worthwhile mentioning that the results have relative errors of 1.91%, 5.47% and 1.22% respectively. In this paper, the radiation field is restored very well according to the sparse sampling data. Hence, the proposed method is a quite effective way for the inversion of nuclear radiation field.

Radiation induced currents in mineral-insulated cables and in pick-up coils: model calculations and experimental verification in the BR1 reactor

Mineral-insulated (MI) cables and Low-Temperature Co-fired Ceramic (LTCC) magnetic pick-up coils are intended to be installed in various position in ITER. The severe ITER nuclear radiation field is expected to lead to induced currents that could perturb diagnostic measurements. In order to assess this problem and to find mitigation strategies models were developed for the calculation of neutron-and gamma-induced currents in MI cables and in LTCC coils. The models are based on calculations with the MCNPX code, combined with a dedicated model for the drift of electrons stopped in the insulator. The gamma induced currents can be easily calculated with a single coupled photon-electron MCNPX calculation. The prompt neutron induced currents requires only a single coupled neutron-photon-electron MCNPX run. The various delayed neutron contributions require a careful analysis of all possibly relevant neutron-induced reaction paths and a combination of different types of MCNPX calculations. The models were applied for a specific twin-core copper MI cable, for one quad-core copper cable and for silver conductor LTCC coils (one with silver ground plates in order to reduce the currents and one without such silver ground plates). Calculations were performed for irradiation conditions (neutron and gamma spectra and fluxes) in relevant positions in ITER and in the Y3 irradiation channel of the BR1 reactor at SCK•CEN, in which an irradiation test of these four test devices was carried out afterwards. We will present the basic elements of the models and show the results of all relevant partial currents (gamma and neutron induced, prompt and various delayed currents) in BR1-Y3 conditions. Experimental data will be shown and analysed in terms of the respective contributions. The tests were performed at reactor powers of 350 kW and 1 MW, leading to thermal neutron fluxes of 1E11 n/cm2s and 3E11 n/cm2s, respectively. The corresponding total radiation induced currents are ranging from 1 to 7 nA only, putting a challenge on the acquisition system and on the data analysis. The detailed experimental results will be compared with the corresponding values predicted by the model. The overall agreement between the experimental data and the model predictions is fairly good, with very consistent data for the main delayed current components, while the lower amplitude delayed currents and some of the prompt contributions show some minor discrepancies.

Fusion Power Measurement at ITER

Nuclear fusion research aims to provide energy for the future in a sustainable way and the goal of ITER project is to demonstrate the feasibility of nuclear fusion energy. ITER is a nuclear experimental reactor based on a large scale fusion plasma device (of tokamak type) generating Deuterium — Tritium (DT) fusion reactions with emission of 14 MeV neutrons producing up to 700 MW fusion power. The measurement of fusion power, i.e. total neutron emissivity, will play an important role for achieving ITER goals, in particular the fusion gain factor Q related to the reactor performance. Particular attention is given also to the development of the neutron calibration strategy whose main scope is to achieve the required accuracy of 10% for the measurement of fusion power. Neutron Flux Monitors located in diagnostic ports and inside the vacuum vessel will measure ITER total neutron emissivity, expected to range from 1014 n/s in Deuterium — Deuterium (DD) plasmas up to almost 1021 n/s in DT plasmas. The neutron detection systems as well all other ITER diagnostics have to withstand high nuclear radiation and electromagnetic fields as well ultrahigh vacuum and thermal loads.

KGK-2-type detector of gamma-radiation power for diagnosis of nuclear reactor radiation fields within the range from 1 µGy/s to 100 Gy/s

The construction of the KGK-2-type detector of γ-radiation power is briefly described. The diagnostic possibilities of the detector are shown by the example of results of the dose rate measurement in the energy start-ups of the BR-K1 and BR-1M reactors implemented in the mode of generating fission pulses on delayed neutrons. The possibilities of using the KGK-2 detector for postpulse γ diagnostics are demonstrated by the example of results of measurements in the fission pulse on prompt neutrons of the BR-1M reactor.

Performance Analysis of the Ironless Inductive Position Sensor in the Large Hadron Collider Collimators Environment.

The Ironless Inductive Position Sensor (I2PS) has been introduced as a valid alternative to Linear Variable Differential Transformers (LVDTs) when external magnetic fields are present. Potential applications of this linear position sensor can be found in critical systems such as nuclear plants, tokamaks, satellites and particle accelerators. This paper analyzes the performance of the I2PS in the harsh environment of the collimators of the Large Hadron Collider (LHC), where position uncertainties of less than 20 µm are demanded in the presence of nuclear radiation and external magnetic fields. The I2PS has been targeted for installation for LHC Run 2, in order to solve the magnetic interference problem which standard LVDTs are experiencing. The paper describes in detail the chain of systems which belong to the new I2PS measurement task, their impact on the sensor performance and their possible further optimization. The I2PS performance is analyzed evaluating the position uncertainty (on 30 s), the magnetic immunity and the long-term stability (on 7 days). These three indicators are assessed from data acquired during the LHC operation in 2015 and compared with those of LVDTs.

Durability and shielding performance of borated Ceramicrete coatings in beta and gamma radiation fields

Ceramicrete™, a chemically bonded phosphate ceramic, was developed for nuclear waste immobilization and nuclear radiation shielding. Ceramicrete products are fabricated by an acid–base reaction between magnesium oxide and mono potassium phosphate. Fillers are used to impart desired properties to the product. Ceramicrete’s tailored compositions have resulted in several commercial structural products, including corrosion- and fire-protection coatings. Their borated version, called Borobond™, has been studied for its neutron shielding capabilities and is being used in structures built for storage of nuclear materials. This investigation assesses the durability and shielding performance of borated Ceramicrete coatings when exposed to gamma and beta radiations to predict the composition needed for optimal shielding performance in a realistic nuclear radiation field. Investigations were conducted using experimental data coupled with predictive Monte Carlo computer model. The results show that it is possible to produce products for simultaneous shielding of all three types of nuclear radiations, viz., neutrons, gamma-, and beta-rays. Additionally, because sprayable Ceramicrete coatings exhibit excellent corrosion- and fire-protection characteristics on steel, this research also establishes an opportunity to produce thick coatings to enhance the shielding performance of corrosion and fire protection coatings for use in high radiation environment in nuclear industry.

Effects of different types of nuclear radiations on optically stimulated luminescence

This study aims to investigate the effects of different nuclear radiation fields on an optically stimulated luminescence (OSL) dosimeter using Al_2O_3:C material. The Al_2O_3:C material was exposed to alpha- and beta-particles and gamma-photons, and the luminescence signals were measured by stimulation with a blue light emitting diode. It is concluded that the OSL technique is suitable for obtaining an adequate blue light stimulated luminescence signal in alpha, beta, and gamma radiation fields, and if the source activity was low, the statistical distributions were large.

Low-cost Multi-UAV Technologies for Contour Mapping of Nuclear Radiation Field

Low cost UAVs are becoming more and more popular in both research and practical applications, and it leads to a new, potentially significant service product known as UAV-based personal remote sensing (PRS). Multi-UAV system with advanced cooperative control algorithms has advantages over single UAV system, especially in time urgent tasks such as detecting nuclear radiation before deploying the salvage. This paper considers two scenarios for nuclear radiation detection using multiple UAVs, of which contour mapping of the nuclear radiation is simulated. Then, for real applications, this paper presents a low-cost UAV platform with built-in formation flight control architecture together with a formulated standard flight test routine. Three experimental formation flight scenarios that imitate the nuclear detection missions are prepared for contour mapping of nuclear radiation field in 3D space.

Probing the Central Regions of AGN through VHE Gamma-Ray Induced Pair Cascades

Recent discoveries by VERITAS, H.E.S.S., and MAGIC indicate that very-high-energy (VHE) gamma-rays may be produced in all types of blazars, including radio-loud quasars. In the dense nuclear radiation fields (BLR, dust torus IR) in these objects, VHE gamma-rays may be efficiently absorbed and initiate Compton-supported pair cascades. We have developed a Monte-Carlo code following the full 3-dimensional development of pair cascades in AGN environments. We have shown that even very weak magnetic fields may lead to efficient quasi-isotropization of the cascade emission, escaping predominantly in MeV – GeV gamma-rays. We propose this as a potential contributor to the Fermi gamma-ray flux from several radio galaxies, and present model fits to the Fermi-detected radio galaxies NGC 1275 and Cen A.

Fusion neutron diagnostics on ITER tokamak

ITER is an experimental nuclear reactor, aiming to demonstrate the feasibility of nuclear fusion realization in order to use it as a new source of energy. ITER is a plasma device (tokamak type) which will be equipped with a set of plasma diagnostic tools to satisfy three key requirements: machine protection, plasma control and physics studies by measuring about 100 different parameters. ITER diagnostic equipment is integrated in several ports at upper, equatorial and divertor levels as well internally in many vacuum vessel locations. The Diagnostic Systems will be procured from ITER Members (Japan, Russia, India, United States, Japan, Korea and European Union) mainly with the supporting structures in the ports. The various diagnostics will be challenged by high nuclear radiation and electromagnetic fields as well by severe environmental conditions (ultra high vacuum, high thermal loads). Several neutron systems with different sensitivities are foreseen to measure ITER expected neutron emission from 1014 up to almost 1021 n/s. The measurement of total neutron emissivity is performed by means of Neutron Flux Monitors (NFM) installed in diagnostic ports and by Divertor Neutron Flux Monitors (DNFM) plus MicroFission Chambers (MFC) located inside the vacuum vessel. The neutron emission profile is measured with radial and vertical neutron cameras. Spectroscopy is accomplished with spectrometers looking particularly at 2.5 and 14 MeV neutron energy. Neutron Activation System (NAS), with irradiation ends inside the vacuum vessel, provide neutron yield data. A calibration strategy of the neutron diagnostics has been developed foreseeing in situ and cross calibration campaigns. An overview of ITER neutron diagnostic systems and of the associated challenging engineering and integration issues will be reported.

VHE GAMMA-RAY INDUCED PAIR CASCADES IN BLAZARS AND RADIO GALAXIES

Recent discoveries by VERITAS, H.E.S.S., and MAGIC indicate that very-high-energy (VHE) gamma-rays may be produced in all types of blazars, including radio-loud quasars. In the dense nuclear radiation fields (BLR, dust torus IR) in these objects, VHE gamma-rays may be efficiently absorbed and initiate Compton-supported pair cascades. We have developed a Monte-Carlo code following the full 3-dimensional development of pair cascades in AGN environments. We have shown that even very weak magnetic fields may lead to efficient quasi-isotropization of the cascade emission, escaping predominantly in MeV – GeV gamma-rays. We propose this as a potential contributor to the Fermi gamma-ray flux from several radio galaxies, and present model fits to the Fermi-detected radio galaxies NGC 1275 and Cen A.