Self-absorption Factor Research Articles

The comparison of manganese spectral lines for self-absorption reduction in LIBS using laser-induced fluorescence

The detection of manganese (Mn) in steel by laser-induced breakdown spectroscopy (LIBS) provides essential information for steelmaking. However, self-absorption greatly disrupts the LIBS spectral lines of Mn with high content. In this study, to minimize self-absorption for Mn spectral lines in LIBS, laser-induced fluorescence (LIF) was applied. Compared with conventional LIBS, the self-absorption factors (α) of Mn I 403.08, 403.31, and 403.45 nm lines were reduced by 90%, 88%, and 88%, respectively; the root mean square errors of cross-validation were decreased by 88%, 85%, and 87%, respectively; the average relative errors were reduced by 93%, 90%, and 91%, respectively; and average relative standard deviations were decreased by 29%, 32%, and 33%, respectively. The LIBS-LIF was shown to successfully minimize the self-absorption effect and spectral intensity fluctuation and improve detection accuracy.

Meta-Study of Particulate Detection Losses on Radioactive Air Sample Filters

Several mathematical relationships between air sample filter mass loading and the correlated analytical self-absorption factor were developed using data from other published research in this meta-study. Gross-alpha and -beta applications are addressed for this research. As filter media becomes loaded with particulate matter, there is potential for measurement losses due to self-absorption by mass loading. Components contributing to absorption include particulate dust, radioactive particulates, and filter material. Standards indicate a correction factor should be used when the penetration of radioactive material into the collection media or self-absorption of radiation by the material collected would reduce the detection rate by more than 5%. Previously, losses due to self-absorption have been reported up to 100% over a range up to ~10 mg⋅cm-2 mass loading. These absorption losses then can be used to determine a correction factor for sample results. For low mass loadings (e.g., ≤0.1 mg⋅cm-2) corrections factors in the 0.85 - 1 range have been recommended and used, while at higher mass loadings nearer to 10 mg⋅cm-2 correction factors closer to 0 (representing near 100% losses) are used. Based on data from published studies, the different methods for relating percent loss due to self-absorption to mass loading include linear, exponential, quadratic, and trinomial derived functions. Where applicable, both forced zero and non-forced zero results were evaluated. From the derived functions evaluated, the trinomial function provided the best fit. Once the sample filter mass loading is known, the trinomial function can be applied to estimate losses and the corresponding self-absorption factor. When applied to routine operating conditions for radiological facility stacks monitored at the Pacific Northwest National Laboratory for an average sample filter mass loading of 0.09 ± 0.12 (2σ) mg⋅cm-2 (excluding negative values and outliers) and a range from 0 - 0.24 mg⋅cm-2, the estimated trinomial function nominal self-absorption losses are less than 5% at 0.09 mg⋅cm-2 and less than 10% at 0.24 mg⋅cm-2. The trinomial function is one method that may be used to adjust the activity results of an air sample when the sample-specific mass loading is determined. The application of no correction factor when the ANSI/HPS N13.1-2021 guidance of a 5% threshold for loss is not reached with typical stack sample mass loadings may be reasonable in high-efficiency particulate air filtered systems. For simplicity, it would be conservative in assigning the self-absorption correction factor at the 5% threshold (i.e., 0.95) for general uses but in cases of heavy mass loading to calculate the factor.

Radiation-transmission and self-absorption factors of P2O5 – SrO – Sb2O3 glass system

A high performance simulation method is an essential research tool, especially for some complicated problems related to the radiation exposure and human health. In this paper, we study the radiation-transmission and self-absorption factors of the newly developed P2O5 – SrO – Sb2O3 glass system using 3D Geant4 simulations. The validation of our results is presented against a collection of theoretical methods by calculating the mass/linear attenuation coefficients (MAC & LAC). A good agreement between our simulation results and the theoretical ones demonstrates that the present simulation model can be helpful for solving further problems in the radiation shielding field. The obtained data are then utilized to assess the radiation shielding efficiency and half value layer for the samples within P2O5 – SrO – Sb2O3 glass system. Finally, we compare the shielding competence of our glass system with the published data of several standard shields. The results reveal that the mean free paths (MFPs) of PSS4 glass sample are smaller than those of RS-253-G18 (standard shield) and ordinary concrete. This means that the Sb2O3 content may play a beneficial role to improve the shielding competence of the present glass system. Therefore, the P2O5 – SrO – Sb2O3 glass system has a potential use to be a successful application for radiation protection (shielding) in the nuclear sites.

Investigation of 18F and 89Zr Isotopes Self-Absorption and Dose Rate Parameters for PET Imaging.

This work concerns study of self-absorption factor (SAF) and dose rate constants of zirconium-89 (89Zr) for the purpose of radiation protection in positron emission tomography (PET) and to compare them with those of 18F-deoxyglucose (18F-FDG). We analyzed the emitted energy spectra by 18F and 89Zr through anthropomorphic phantom and calculated the absorbed energy using Monte Carlo method. The dose rate constants for both radionuclides were estimated with 2 different fluence-to-effective dose conversion coefficients. Our estimated SAF value of 0.65 for 18F agreed with the recommendation of the American Association of Physicists in Medicine (AAPM). The SAF for 89Zr was in the range of 0.61-0.66 depending on the biodistribution. Using the fluence-to-effective dose conversion coefficients recommended jointly by the American National Standards Institute and the American Nuclear Society (ANSI/ANS), the dose rate at 1 m from the patient for 18F was 0.143 μSv·MBq−1·hr−1, which is consistent with the AAPM recommendation, while that for 89Zr was 0.154 μSv·MBq−1·hr−1. With the conversion coefficients currently recommended by the International Committee on Radiological Protection (ICRP), the dose rate estimates were lowered by 2.8% and 2.6% for 89Zr and 18F, respectively. Also, we observed that the AAPM derived dose is an overestimation near the patient, compared to our simulations, which can be explained by the biodistribution nature and the assumption of the point source. Thus, we proposed new radiation protection factors for 89Zr radionuclide.

Self-absorption Correction Factors: Applying A Simplified Method to Analysis of Lead-210 in Different Environment Samples by Direct Counting of Low-energy Using HPGe Detector

This study aimed to determine the self-absorption correction factors of lead-210 (210Pb) in various Syrian environment samples. Seven sediments, five soils, and four plant samples were analysed by Gamma Spectroscopy using simple and direct analysis method called Cutshall. The method is based on measuring the penetration of gamma which emitted from a standard source, prepared in the laboratory by deposition of QCYB40 Standard Solution on stainless steel disk. The source was placed on top of the studied sample and the reference air sample during the measurement. The purpose was to study the self-absorption inside each sample by calculation of its self-absorption factors without knowing its chemical composition. The self-absorption correction results for the sediment samples SE3, SE6 and SE8 ranged between 36% and 45%, and 34% to 42% for the soil samples S5 and S1, respectively. Also, for the four plant samples, it recorded variance range from 4% to 18%. This is due to the difference in the density of the G4 sample, which appeared to be very low. However, the self-absorption correction factors CF were set for the different environmental samples, and the results show that the density factor of the sample is not the only influent factor in the CF values for low energies measurement, the sample chemical composition (sample matrix) is also more effective in addition to the samples’ particle sizes.

Spectral interference elimination and self-absorption reduction in laser-induced breakdown spectroscopy assisted with laser-stimulated absorption

Spectral interference and self-absorption seriously affect the accuracy of quantitative analysis in laser-induced breakdown spectroscopy (LIBS). In this work, we used LIBS assisted with laser-stimulated absorption (LSA-LIBS) to solve these problems. Taking nickel (Ni) in the alloy structural steel as an example, the results show that the spectral interference of Ni lines was eliminated, the self-absorption factor of the Ni I 341.47 nm line was reduced by 85%, and the average relative error for determination of Ni element was reduced by 83% using LSA-LIBS. The results indicate that spectral interference and self-absorption can be reduced simultaneously in LSA-LIBS.

Comparison of BCF-10, BCF-12, and BCF-20 Scintillating Fibers for Use in a 1-Dimensional Linear Sensor

One-dimensional fiber-bundle arrays may prove useful in a number of radiation sensing applications where radiation detection over large areas is needed. Tests have been performed to evaluate the light generation and transmission characteristics of 15-meter long, 10-fiber bundles of BCF-10, BCF-12, and BCF-20 scintillating fibers (Saint Gobain) exposed to collimated gamma-ray sources. The test set-up used one R9800 (Hamamatsu) photomultiplier tube (PMT) at each end, with a high-speed waveform digitizer to collect data. Time constraints were imposed on the waveform data to perform time-of-flight analysis of the events in the fiber bundles, eliminating spurious noise pulses in the high gain PMTs and also allowing 1-dimensional localization of interactions along the lengths of the fiber bundles. Measurements show that the spatial response of these three fibers is linear over at least 15-m lengths and that, with the equipment used here, the spatial resolution for events irradiating 1 cm of fiber (using a collimated source) ranges from 50 cm to 60 cm over the entire length of the bundles. The efficiency for detecting events varies along the length of the arrays, with the sensitivity at the midpoint (half of the distance) of an array ranging from ~ 2X to ~ 3X the efficiency at the ends, depending on the length of the fiber-bundle array and the self-absorption factor for each fiber's scintillation light. Compared to prior work, a 20-fold improvement in detection sensitivity has been shown for this technique, most likely due to improved optical coupling and improved signal analysis.

Investigation of Alpha and Beta Self-Absorption Factors in the Calibration of Water Sample Measurements

Detector efficiencies and self-absorption factors for a variety of sample preparation methods and naturally occurring dissolved ions have been studied for the gross alpha and gross beta measurement of water samples. The most consistent results are obtained for samples prepared by evaporation of small volumes of water under an infrared lamp. Due to its uniform and homogeneous deposition in the cupped stainless steel planchet, CaCO₃ was found to best serve as the dry residue radionuclide carrier in this study. Detector efficiencies and self-absorption factors for gross alpha and gross beta measurements closely follow the expected exponential and logarithmic dependence, respectively.

Experimental determination of the self-absorption factor for MTR plates by passive gamma spectrometric measurement

The measurement of the absolute activity or the mass of radioactive substances by gamma spectrometry needs to include a correction for the radiation absorption inside the source volume, the so-called self-absorption factor. It depends on geometry and material composition of the source, the detector geometry and on the geometrical arrangement of source and gamma radiation detector; it can be calculated if full information about all that is available. This article however describes how to determine the self-absorption factor from measurements if the radiation sources are plates of uranium fuel with typical parameters of nuclear fuel for MTR reactors and without using detail information on the source geometry, thus allowing easy inspection without relying on – potentially falsified – declarations on the internal properties of the fuel objects and without calculation.

Methods for spectral interference corrections for direct measurements of 234U and 230Th in materials by gamma-ray spectrometry

When the high-resolution gamma-ray spectrometry was used in the analysis of (234)U and (230)Th in samples, there is a much more need to correct for the measured activity results of (234)U and (230)Th mainly due to self-absorption effects and the interfering lines from (226)Ra, (235)U, (238)U and their decay products that often might be present in the samples. Therefore, in the present study, the methods for the spectral interference corrections for the analytical peaks of (234)U and (230)Th are suggested to take into account the contributions of the overlapping gamma rays to these peaks. For the method validation, direct gamma-ray spectrometric measurements were carried out using certified reference materials (CRM) by use of a 76.5 % n-type Ge detector. The activities measured for the CRM samples were corrected for spectral interferences, self-absorption and true coincidence-summing (TCS) effects. The obtained results indicate that ignoring of the contribution of the interference gamma rays to the main analytical peak at 53.2 keV of (234)U leads to a lager systematic error of 87.3-90.4 % for the measured activities of (234)U, and similarly if one ignores the contributions of the interference gamma rays to the main analytical peak at 67.7 keV of (230)Th, this leads to a much smaller systematic error of 2.1-2.7 % for the activities of (230)Th. Therefore, the required correction factors for spectral interferences to the analytical peaks of (234)U and (230)Th are not negligible and thus they should also be considered besides necessary self-absorption factors to determine more accurate activities in the samples. On the other hand, it is estimated that although the TCS effects on the main analytical peaks of both (234)U and (230)Th are negligibly small, those TCS correction factors for their interference gamma rays to these peaks should be taken into account when direct measurements are performed in a close-counting geometry condition. Otherwise, the resulted activities can have serious erroneous results for both (234)U and (230)Th while using gamma-ray spectrometry, thereby leading to inaccuracies in their derived quantities, for instance, the corresponding age determinations of the samples.

Experimental and simulation methods to evaluate the alpha self-absorption factors for radioactive aerosol fiber filters

Air sampling for particulate radioactive material involves collecting airborne particles on a filter in order to measure the radioactivity in the environment or in working areas. The amount of alpha radioactivity collected on the sampling filter is frequently determined by global alpha-particles measurements. Several factors can affect the alpha energy while passing through the filter to reach the detector. The most affecting factor on the alpha spectrum degradation is the absorption of alpha particle energies in the filter fibers. The fibers' density can range from 1 to 9 mg cm −2. The counting losses can accordingly be important, and the global activity in the filter can be underestimated. The complexity of the experiments and the diversity of the filter types, filtration conditions as well as detector types used for survey incite us to formulate a numerical model to simulate the correction factors of the degraded activity. Comparisons between experimental and simulated correction factors for a commonly used filter are presented. The good agreement found between experimental and calculated values validates the method in the studied conditions.

Gross alpha determination in radioactive wastes from nuclear power plants using the track registration technique

Low and intermediate level nuclear wastes (ion-exchange resins and evaporator concentrates) essentially contain beta and gamma emitters, with very few alpha emitters. Several techniques may be used to determine gross alpha activity but, in this case, solid-state nuclear track detectors (SSNTDs) are a suitable technique for gross alpha determination because track detectors are not sensitive to beta and gamma emitters. Also, this technique is simple and inexpensive. In this paper, we studied the parameters (background, efficiency and self-absorption) that could affect the gross alpha determination using SSNTDs for both sample preparation methods, the “dry method” with tensioactives and the “wet method”. For the “dry method”, a self-absorption curve for 241Am standard was prepared using a set of varying thickness of sodium salt and for two different tensioactives: Tween ® 20 and Teg. The results showed that, below 1 mg / cm 2 , the self-absorption factor can be considered similar for both tensioactives and equal to unity. Several detectors for gross alpha determination were compared and we found that the most suitable techniques were ZnS(Ag) solid scintillator and track detectors. Both detectors were used to compare radioactive waste samples. Finally, the proposed methods (“dry method” with Teg tensioactive and “wet method”) using track detectors were tested by analysing the gross alpha activity of several radioactive wastes.

A new technique for the accurate measurement of 226Ra by gamma spectroscopy in voluminous samples

Accuracy in the measurements of 226Ra concentrations by gamma spectroscopy depends on an appropriate determination of the concentrations of 222Rn decay products ( 214Pb and 214Bi) in the sample. As an inert gas, radon can leak from the sample vessel or accumulate in the void upper part of it. In the latter case, radon decay products can be attached on the inner surface of the sample container, and therefore the gamma rays have another geometry and self-absorption factor which differs from the one assumed (similar to the calibration sample). The influence of the above procedures on the accuracy of the measurements depends mainly on the emanation factor of radon in the sample, the geometry used in the measurement and the structure of the sample container. Results of the tests that have been performed with a new technique developed in order to eliminate radon diffusion through the sample are presented. Two materials with different effective 226Ra concentrations were used for the tests: soil with 5 Bq kg −1 effective 226Ra (total 226Ra concentration 20 Bq kg −1 and emanation factor 25%) and phosphate fertilizer with 22 Bq kg −1 effective 226Ra (total 226Ra concentration 306 Bq kg −1 and emanation factor 7%). From gamma-spectroscopy measurements it was found out that the increase in 226Ra concentration, when charcoal was added to the samples, was about 35% of the effective 226Ra of the sample. This could lead to an underestimate of about 10% of the 226Ra concentrations in voluminous samples with high emanation factor (25%).

Dose estimate of inhaled hafnium tritide using the ICRP 66 lung model.

Metal tritide is widely used for research, purification, compression, and storage of tritium. The current understanding of metal tritide and its radiation dosimetry for internal exposure is limited, and ICRP publications do not provide the tritium dosimetry for hafnium tritide. The current radiation protection guidelines for metal tritide particles (including hafnium tritide) are based on the assumption that their biological behavior is similar to tritiated water, which is completely absorbed by the body. However, the solubility of metal tritide particles depends on the chemical form of the material. The biological half-live of hafnium tritide particles and the dosimetry of an inhalation exposure to those particles could be quite different from tritiated water. This paper describes experiments on the dissolution rate of hafnium tritide particles in a simulated lung fluid. The results showed that less than 1% of the tritium was dissolved in the simulated lung fluid for hafnium tritide particles after 215 d. The short-term and long-term dissolution half times were 46 and 4.28 x 10(5) d, respectively. This indicates that hafnium tritide is an extremely insoluble material. Self-absorption of beta rays in the hafnium tritide particles was estimated by a numerical method. The dose coefficients were calculated as a function of particle size using in vitro solubility data and a calculated self-absorption factor. The dose coefficient decreased with aerodynamic diameters in the range of 0.25 to 10 microm, mainly because the self-absorption factor decreased with increasing particle size. For a particle 1 microm in aerodynamic diameter, the dose coefficient of a hafnium tritide particle was about 10 times higher than that of tritiated water but was about 1.4 times lower than that calculated by ICRP Publication 71 for Type S tritiated particles. The ICRP estimate did not include a self-absorption factor and thus might have overestimated the dose. This finding has significant implications for current health protection guidelines.

Characterization of Carbon Tritide Particles in a Tokamak Fusion Reactor

ABSTRACTAmorphous tritiated carbon films are formed through co-deposition of the radioactive isotope tritium (3H or T) with carbon onto plasma facing surfaces in fusion plasmas. The Tokamak Fusion Test Reactor (TFTR), operated by the Princeton Plasma Physics Laboratory, was fueled by tritium and deuterium neutral beam injection and gas puffing. Tritium was co-deposited as amorphous hydrogenated carbon onto graphite tiles and stainless steel surfaces inside the reactor. Since termination of plasma operations, carbon tritide particles have remained in the air in the vessel. Dosimetric limits for occupational exposure to carbon tritide particles need to be established. The purpose of this study was to characterize carbon tritide particle samples inside the TFTR in terms of size, self-absorption of tritium beta, and dissolution rate in simulated lung fluid. Dose estimates of the inhaled carbon tritide particles can be calculated based on the dissolution rate, particle size, and self-absorption factor. The count median diameter and geometric standard deviation were 1.23 µm and 1.72, respectively, indicating that they are respirable particles and can stay suspended in the air for a longer time. The dissolution rate in the lung-simulated fluid was determined in a static system. The dissolution rate ranged from 10−1–10−3 per day in the first few hours, then it decreased to between 10−3 and 10−4. The retention curve of tritium in carbon indicated that >90% of the tritium remained in the particles after 110 d in the simulated lung fluid. This information is being used to support the establishment of respiratory protection requirements.

Rapid determination of gross alpha-activity in sea water by coprecipitation

The radiological examination of water requires a rapid screening that permits the determination of gross alpha-activity in order to decide if further radiological analyses are necessary. The usual method of gross alpha-determination includes sample evaporation to dryness on a disk and counting using a ZnS(Ag) scintillation detector or a proportional counter. The determination of gross alpha-activity in sea water using this method has a number of drawbacks such as high mass attenuation, lack of homogeneity in the precipitate, and very small volume of sample. In this work, coprecipitation is proposed to enable a 500 ml sample of water to be analyzed. The minimum detectable activity (MDA) achieved was 0.004 Bq.l–1 for a counting time of only 4 hours. Weight variation, self-absorption factor, efficiency and blanks were studied. In order to test reproducibility of the method, several Spanish coastal sea water samples were analyzed by two different laboratories.

Biokinetics and dosimetry of titanium tritide particles in the lung.

Doses of internal radiation from inhalation of metal tritide aerosols are potentially a major radiation protection problem encountered by nuclear industry workers. Based on results of experiments with rats intratracheally instilled with titanium tritide particles and on a self-absorption factor of beta particles determined by a numerical method, a biokinetic model was developed for inhaled particles of titanium tritide. Results showed that lung burdens of the tritide are well represented by a two-component exponential equation; biological half-lives derived for the retention of 3H in lung were 0.81 d and 66 d. The tritium clearance rate via urine or feces was described by bi-phase exponential components. At 121 d after instillation, 82% of the initial lung burden of 3H had been eliminated, of which 37% was excreted in urine, 29% via feces, and 16% through exhaled air. Based on simulation results of the biokinetic model, the cumulative absorbed dose and committed effective dose were calculated as well as the annual limit of intake (ALI) and derived air concentration (DAC). The ALI and DAC values for titanium tritide were a factor of 5 lower than values for tritiated water. This information will be useful in developing new guidelines for radiation protection purposes.

Self-absorption of tritium betas in metal tritide particles.

Inhaling metal tritide particles is a potential occupational hazard. The radiation dose to tissue from tritide particles depends on their solubility and retention in the body. In each tritide particle, a portion of the beta particles from decay of tritium is absorbed by the metal matrix and therefore cannot contribute to absorbed radiation dose to tissue. A theoretical model for estimating the self-absorption of tritium betas in spherical metal tritide particles is presented. Numerical calculations are made with this method for titanium, zirconium, and erbium particles from 0.5 to 50 microm in diameter. The tritium spectrum is divided into energy groups to facilitate estimation of the energy that escapes the particle for dose calculations. Our results show considerable absorption of beta particles and their energy, even for respirable particles smaller than 5 microm. Limited experimental data of self-absorption for titanium and zirconium tritides supported the theoretical calculation. It is concluded that the self-absorption factors should be required for counting tritide particle samples as well as for estimating absorbed radiation dose to tissue.

Self-absorption corrections for well-type germanium detectors

Corrections for self-absorption are of vital importance to accurate determination by gamma spectroscopy of radionuclides such as 210Pb, 241Am and 234Th which emit low energy gamma radiation. A simple theoretical model for determining the necessary corrections for well-type germanium detectors is presented. In this model, self-absorption factors are expressed in terms of the mass attenuation coefficient of the sample and a parameter characterising the well geometry. Experimental measurements of self-absorption are used to evaluate the model and to determine a semi-empirical algorithm for improved estimates of the geometrical parameter.

Mouth and Throat Deposition of 3.6 μm Radiolabelled Particles in Asthmatics

Deposition in mouth and throat of 3.6 μm (aerodynamic diameter) monodispersed Teflon particles labelled with 111In was studied in agroup (n=29) of mild to moderately severe asthmatics. The particles were inhaled at 0.5 1/sec. with maximally deep inhalations. Immediately after the inhalation radioactivity was measured in mouth and throat, lungs, stomach, rinsing water and exhalation filter. Radioactivity in mouth and throat, rinsing water and stomach were considered to represent the amount deposited in mouth and throat. From measurements on a phantom factors of selfabsorption in mouth and throat, lungs and stomach was 2, 2.5 and 4, respectively. Calculations using rather large changes in the interrelationship between these selfabsorption factors effected only to a minor extent the calculated depositions in mouth and throat. There was a large variation in deposition in mouth and throat among the subjects, range 7-66% with about 3/4 in the range 0-30% and 1/4 in the range 30-70%. The women had higher deposition than the men. In 20 of the asthmatics who inhaled the test particles twice, the deposition correlated well between the two inhalations, r=0.84. This fairly high reproducibility suggests that it might be valuable to measure deposition in mouth and throat of a test aerosol in patients with asthma in order to estimate individual risks or benefits of aerosols of similar particle sizes.