Multi-Layered Composites of Natural Rubber (NR) and Bismuth Oxide (Bi2O3) with Enhanced X-ray Shielding and Mechanical Properties.

Due to rapid increases in the utilization of radiation and nuclear technologies, effective and suitable radiation-shielding materials have become one of the most sought-after options to protect users and the public from excessive exposure to the radiation. However, most radiation-shielding materials have greatly reduced mechanical properties after the addition of fillers, resulting in their limited useability and shortened lifetime. Therefore, this work aimed to alleviate such drawbacks/limitations by exploring a possible method to simultaneously enhance both the X-ray shielding and mechanical properties of bismuth oxide (Bi2O3)/natural rubber (NR) composites through multi-layered structures, with varying (1-5) layers and a total combined thickness of 10 mm. To correctly determine the effects of the multi-layered structures on the properties of NR composites, the formulation and layer configuration for all multi-layered samples were tailored such that their theoretical X-ray shielding properties were equal to those of a single-layered sample that contained 200 phr Bi2O3. The results indicated that the multi-layered Bi2O3/NR composites with neat NR sheets on both outer layers (sample-D, sample-F, sample-H, and sample-I) had noticeably higher tensile strength and elongation at break than those of the other designs. Furthermore, all multi-layered samples (sample-B to sample-I), regardless of the layer structure, had enhanced X-ray shielding properties compared to those with a single layer (sample-A), as shown by their higher values of the linear attenuation coefficient (µ) and lead equivalence (Pbeq) and the lower value of the half-value layer (HVL) in the former. This work also determined the effects of thermal aging on relevant properties for all samples, with the results revealing that all the thermal-aged composites had higher values for the tensile modulus but lower values for the swelling percentage, tensile strength, and elongation at break, compared with the non-aged composites. Hence, based on the overall outcomes from this work, it could be concluded that the worrisome decreases in mechanical properties of the common single-layered NR composites after the addition of Bi2O3 could be prevented/reduced by introducing appropriate multi-layered structures, which would not only widen potential applications but also prolong the lifetime of the composites.

Fruit Peel Powder as Natural Antioxidant and Reinforcing Bio-Filler in Natural Rubber Latex Gloves: Cases of Mangosteen, Pomelo and Durian.

As the world is facing rapid increases in agricultural wastes that greatly affect global health, the environment, and economies, this work aims to alleviate such issues by introducing simple uses of waste fruit peel powder (FPP) derived from mangosteen (MPP), pomelo (PPP), or durian (DPP), as dual natural antioxidants and reinforcing bio-fillers in natural rubber latex (NRL) gloves. A thorough investigation was undertaken of the relevant characteristics for both FPP (morphological, functional groups, particle sizes, and thermals stability) and NRL gloves (morphological, functional groups, density, color, thermal stability, and mechanical properties-both before and after thermal/25 kGy gamma aging). The results indicated that the initial addition (2-4 parts per hundred parts of rubber by weight; phr) of FPP to NRL composites generally enhanced the strength and elongation at the break of the specimens, with the levels of the improvement varying depending on the type and content of FPPs. In addition to the reinforcing effects, the FPP also offered natural antioxidant properties, evidenced by higher values of aging coefficients for all FPP/NRL gloves under either thermal or 25 kGy gamma aging than those of pristine NRL. Furthermore, by comparing the tensile strength and elongation at break of the developed FPP/NRL gloves with the requirements for medical examination latex gloves according to ASTM D3578-05, the recommended FPP contents for actual glove production were 2-4 phr for MPP, 4 phr for PPP, and 2 phr for DPP. Consequently, based on the overall outcomes, the FPPs of interest showed promising potential for utilization as simultaneous natural antioxidants and reinforcing bio-fillers in NRL gloves, which would not only enhance the strength and ability of the gloves to resist oxidative degradation from heat and gamma irradiation but also increase their economical value as well as reducing the amounts of the investigated wastes.

Assessing tritium contamination in Thailand's rainwater: A study of environmental monitoring and nuclear surveillance.

Tritium, whether naturally occurring or caused by human nuclear activity, can result in a large amount of tritium contamination in the environment, especially in the water cycle, causing a high concentration of tritium in rainfall. The objective of this research was to measure the level of tritium in the environment from rainfall in two different areas as a basis for monitoring tritium contamination in the environment. Rainwater samples were collected in Thailand every 24 h for a period of 1 year during 2021-2022 at the Kasetsart University Station, Sriracha Campus, Chonburi province and at the Mae Hia Agricultural Meteorological Station, Chiang Mai province. The tritium levels were measured in rainwater samples using the electrolytic enrichment method combined with liquid scintillation counting. The chemical composition of the rainwater was analyzed based on ion chromatography. The results (presented with ± combined uncertainty) showed that the tritium content in the rainwater samples at Kasetsart University Station Sriracha Campus was in the range 0.9 ± 0.2-1.6 ± 0.3 TU (0.11 ± 0.02-0.19 ± 0.03 Bq.L-1). The mean concentration was 1.0 ± 0.2 TU (0.12 ± 0.03 Bq.L-1). The most common ions found in the rainwater samples were SO42-, Ca2+, and NO3-, with mean concentrations of 1.52 ± 0.82, 1.08 ± 0.51, and 1.05 ± 0.78 mg.L-1, respectively. The tritium content in rainwater collected from the Mae Hia Agricultural Meteorological Station was in the range 1.6 ± 0.2-4.9 ± 0.4 TU (0.19 ± 0.02-0.58 ± 0.05 Bq.L-1). The mean concentration was 2.4 ± 0.4 TU (0.28 ± 0.05 Bq.L-1). The most common ions found in the rainwater were NO3-, Ca2+, and SO42-, with mean concentrations of 1.21 ± 1.02, 0.67 ± 0.43, and 0.54 ± 0.41 mg.L-1, respectively. The tritium concentration in the rainwater at both stations differed but remained at a natural level (less than 10 TU). There was no correlation between the tritium concentration and the chemical composition of the rainwater. The tritium levels obtained from this study could be used as a basis for reference and monitoring of future environmental changes due to nuclear accidents or activities, both domestically and internationally.

Estimation of Ambient Dose Equivalent Rate Distribution Map Using Walking Survey Technique in Hirosaki City, Aomori, Japan.

At present, much emphasis is placed on the health risks associated with radioactivity present in the environment, especially since the accident at the Fukushima Daiichi Nuclear Power Plant. In this study, a walking survey was conducted in Hirosaki City using a NaI(Tl) scintillation spectrometer to estimate and map the distribution of the ambient dose equivalent rate to monitor the radiological safety of the general public in Hirosaki City, where many nuclear facilities are located nearby. The average (±standard deviation) ambient dose equivalent rate was 0.056 ± 0.020 µSv h-1. By comparison with the measurement data, it was found that the values of 85% of the data obtained using the walking survey technique deviated within ±20% relative to those obtained by spot measurements. Furthermore, the distribution of dose rates obtained in the nighttime survey was not significantly different from those obtained in the daytime.

Dual X-ray- and Neutron-Shielding Properties of Gd2O3/NR Composites with Autonomous Self-Healing Capabilities.

The neutron- and X-ray-shielding, morphological, physical, mechanical, and self-healing properties were investigated for natural rubber (NR) composites containing varying gadolinium oxide (Gd2O3) contents (0, 25, 50, 75, and 100 parts per hundred parts of rubber; phr) to investigate their potential uses as self-healing and flexible neutron- and X-ray-shielding materials. Gd2O3 was selected as a radiation protective filler in this work due to its preferable properties of having relatively high neutron absorption cross-section (σabs), atomic number (Z), and density (ρ) that could potentially enhance interaction probabilities with incident radiation. The results indicated that the overall neutron-shielding and X-ray-shielding properties of the NR composites were enhanced with the addition of Gd2O3, as evidenced by considerable reductions in the half-value layer (HVL) values of the samples containing 100 phr Gd2O3 to just 1.9 mm and 1.3 mm for thermal neutrons and 60 kV X-rays, respectively. Furthermore, the results revealed that, with the increase in Gd2O3 content, the mean values (± standard deviations) of the tensile strength and elongation at break of the NR composites decreased, whereas the hardness (Shore A) increased, for which extreme values were found in the sample with 100 phr Gd2O3 (3.34 ± 0.26 MPa, 411 ± 9%, and 50 ± 1, respectively). In order to determine the self-healing properties of the NR composites, the surfaces of the cut samples were gently pressed together, and they remained in contact for 60 min; then, the self-healing properties (the recoverable strength and the %Recovery) of the self-healed samples were measured, which were in the ranges of 0.30-0.40 MPa and 3.7-9.4%, respectively, for all the samples. These findings confirmed the ability to autonomously self-heal damaged surfaces through the generation of a reversible ionic supramolecular network. In summary, the outcomes from this work suggested that the developed Gd2O3/NR composites have great potential to be utilized as effective shielding materials, with additional dual shielding and self-healing capabilities that could prolong the lifetime of the materials, reduce the associated costs of repairing or replacing damaged equipment, and enhance the safety of all users and the public.

A Comparative Study on X-ray Shielding and Mechanical Properties of Natural Rubber Latex Nanocomposites Containing Bi2O3 or BaSO4: Experimental and Numerical Determination.

This work experimentally determined the X-ray shielding and morphological, density, and tensile properties of sulfur-vulcanized natural rubber latex (SVNRL) nanocomposites containing varying content of nano-Bi2O3 or nano-BaSO4 from 0 to 200 phr in 100 phr increments, with modified procedures in sample preparation to overcome the insufficient strength of the samples found in other reports. The experimental X-ray shielding results, which were numerically verified using a web-based software package (XCOM), indicated that the overall X-ray attenuation abilities of the SVNRL nanocomposites generally increased with increasing filler content, with the 0.25-mm-thick SVNRL films containing 200 phr of the filler providing the highest overall X-ray shielding properties, as evidenced by the highest values of lead equivalence (Pbeq) of 0.0371 mmPb and 0.0326 mmPb in Bi2O3/SVNRL nanocomposites, and 0.0326 mmPb and 0.0257 mmPb in BaSO4/SVNRL nanocomposites, for 60 kV and 100 kV X-rays, respectively. The results also revealed that the addition of either filler increased the tensile modulus at 300% elongation (M300) and density but decreased the tensile strength and the elongation at break of the Bi2O3/SVNRL and BaSO4/SVNRL nanocomposites. In addition, the modified procedures introduced in this work enabled the developed nanocomposites to acquire sufficient mechanical and X-ray shielding properties for potential use as medical X-ray protective gloves, with the recommended content of Bi2O3 and BaSO4 being in the range of 95-140 phr and 105-120 phr, respectively (in accordance with the requirements outlined in ASTM D3578-19 and the value of Pbeq being greater than 0.02 mmPb). Consequently, based on the overall outcomes of this work, the developed Bi2O3/SVNRL and BaSO4/SVNRL nanocomposites show great potential for effective application in medical X-ray protective gloves, while the modified procedures could possibly be adopted for large-scale production.

Comparative X-ray Shielding Properties of Single-Layered and Multi-Layered Bi2O3/NR Composites: Simulation and Numerical Studies.

This work theoretically compared the X-ray attenuation capabilities in natural rubber (NR) composites containing bismuth oxide (Bi2O3) by determining the effects of multi-layered structures on the shielding properties of the composites using two different software packages (XCOM and PHITS). The shielding properties of the single-layered and multi-layered Bi2O3/NR composites investigated consisted of the transmission factor (I/I0), effective linear attenuation coefficient (µeff), effective mass attenuation coefficient (µm,eff), and effective half-value layer (HVLeff). The results, with good agreement between those obtained from XCOM and PHITS (with less than 5% differences), indicated that the three-layered NR composites (sample#4), with the layer arrangement of pristine NR (layer#1)-Bi2O3/NR (layer#2)-pristine NR (layer#3), had relatively higher X-ray shielding properties than either a single-layer or the other multi-layered structures for all X-ray energies investigated (50, 100, 150, and 200 keV) due to its relatively larger effective percentage by weight of Bi2O3 in the composites. Furthermore, by varying the Bi2O3 contents in the middle layer (layer#2) of sample#4 from 10 to 90 wt.%, the results revealed that the overall X-ray shielding properties of the NR composites were further enhanced with additional filler, as evidenced by the highest values of µeff and µm,eff and the lowest values of I/I0 and HVLeff observed in the 90 wt.% Bi2O3/NR composites. In addition, the recommended Bi2O3 contents for the actual production of three-layered Bi2O3/NR composites (the same layer structure as sample#4) were determined by finding the least Bi2O3 content that enabled the sample to attenuate incident X-rays with equal efficiency to that of a 0.5-mm lead sheet (with an effective lead equivalence of 0.5 mmPb). The results suggested that the recommended Bi2O3 contents in layer#2 were 82, 72, and 64 wt.% for the combined 6 mm, 9 mm, and 12 mm samples, respectively.

High-Energy Photon Attenuation Properties of Lead-Free and Self-Healing Poly (Vinyl Alcohol) (PVA) Hydrogels: Numerical Determination and Simulation.

This work numerically determined high-energy photon shielding properties of self-healing poly(vinyl alcohol) (PVA) hydrogels containing lead-free, heavy-metal compounds, namely, bismuth oxide (Bi2O3), tungsten oxide (WO3), and barium sulfate (BaSO4), through XCOM software packages. In order to understand the dependencies of the shielding properties of the hydrogels on filler contents and photon energies, the filler contents added to the hydrogels were varied from 0-40 wt.% and the photon energies were varied from 0.001-5 MeV. The results, which were verified for their reliability and correctness with those obtained from PHITS (Particle and Heavy Ion Transport code System), indicated that overall shielding performances, which included the mass attenuation coefficients (µm), the linear attenuation coefficient (µ), the half-value layer (HVL), and the lead equivalence (Pbeq), of the hydrogels improved with increasing filler contents but generally decreased with increasing photon energies. Among the three compounds investigated in this work, Bi2O3/PVA hydrogels exhibited the highest photon attenuation capabilities, determined at the same filler content and photon energy, mainly due to its highest atomic number of Bi and the highest density of Bi2O3 in comparison with other elements and compounds. Furthermore, due to possible reduction in self-healing and mechanical properties of the hydrogels with excessive filler contents, the least content of fillers providing a 10-mm sample with the required Pbeq value of 0.5 mmPb was investigated. The determination revealed that only the hydrogel containing at least 36 wt.% of Bi2O3 exhibited the Pbeq values greater than 0.5 mmPb for all photon energies of 0.05, 0.08, and 0.1 MeV (common X-ray energies in general nuclear facilities). The overall outcomes of the work promisingly implied the potential of PVA hydrogels to be used as novel and potent X-ray and gamma shielding materials with the additional self-healing and nonlead properties.

Roles of Chitosan as Bio-Fillers in Radiation-Vulcanized Natural Rubber Latex and Hybrid Radiation and Peroxide-Vulcanized Natural Rubber Latex: Physical/Mechanical Properties under Thermal Aging and Biodegradability.

Although natural rubber was regarded as biodegradable, the degradation is a time-consuming process that could take weeks or months for any degradation or substantial weight loss to be observable, resulting in the need for novel processes/methods to accelerate the rubber degradation. As a result, this work investigated the potential utilization of chitosan (CS) as a biodegradation enhancer for radiation-vulcanized natural rubber latex (R-VNRL) and hybrid radiation and peroxide-vulcanized natural rubber latex (RP-VNRL) composites, with varying CS contents (0, 2, 4, or 6 phr). The R-VNRL samples were prepared using 15 kGy gamma irradiation, while the RP-VNRL samples were prepared using a combination of 0.1 phr tert-butyl hydroperoxide (t-BHPO) and 10 kGy gamma irradiation. The properties investigated were biodegradability in the soil and the morphological, chemical, mechanical, and physical properties, both before and after undergoing thermal aging. The results indicated that the biodegradability of both the R-VNRL and RP-VNRL composites was enhanced with the addition of CS, as evidenced by increases in the percentage weight loss (% weight loss) after being buried in soil for 8 weeks from 6.5 ± 0.1% and 6.4 ± 0.1% in a pristine R-VNRL and RP-VNRL samples, respectively, to 10.5 ± 0.1% and 10.2 ± 0.1% in 6-pph CS/R-VNRL and 6-pph CS/RP-VNRL composites, respectively, indicating the biodegradation enhancement of approximately 60%. In addition, the results revealed that the addition of CS could increase the value of tensile modulus by 119%, while decrease the values of tensile strength and elongation at break by 50% and 43%, respectively, in the specimens containing 6-phr CS. In terms of the color appearances, the samples were lighter and yellower after the addition of CS, as evidenced by the noticeably increased L* and b* values, based on the CIE L*a*b* color space system. Furthermore, the investigation into the effects of thermal aging showed that the overall tensile properties for both curing systems were reduced, while varying degrees of color change were observed, with the pristine R-VNRL and RP-VNRL samples having more pronounced degradation/changes for both properties. In conclusion, the overall results suggested that CS had great potential to be applied as a bio-filler in R-VNRL and RP-VNRL composites to effectively promote the biodegradability, environmental friendliness, and resistance to thermal degradation of the composites.

Simulation of Neutron/Self-Emitted Gamma Attenuation and Effects of Silane Surface Treatment on Mechanical and Wear Resistance Properties of Sm2O3/UHMWPE Composites.

This work reports on the simulated neutron and self-emitted gamma attenuation of ultra-high-molecular-weight polyethylene (UHMWPE) composites containing varying Sm2O3 contents in the range 0-50 wt.%, using a simulation code, namely MCNP-PHITS. The neutron energy investigated was 0.025 eV (thermal neutrons), and the gamma energies were 0.334, 0.712, and 0.737 MeV. The results indicated that the abilities to attenuate thermal neutrons and gamma rays were noticeably enhanced with the addition of Sm2O3, as seen by the increases in µm and µ, and the decrease in HVL. By comparing the simulated neutron-shielding results from this work with those from a commercial 5%-borated PE, the recommended Sm2O3 content that attenuated thermal neutrons with equal efficiency to the commercial product was 11-13 wt.%. Furthermore, to practically improve surface compatibility between Sm2O3 and the UHMWPE matrix and, subsequently, the overall wear/mechanical properties of the composites, a silane coupling agent (KBE903) was used to treat the surfaces of Sm2O3 particles prior to the preparation of the Sm2O3/UHMWPE composites. The experimental results showed that the treatment of Sm2O3 particles with 5-10 pph KBE903 led to greater enhancements in the wear resistance and mechanical properties of the 25 wt.% Sm2O3/UHMWPE composites, evidenced by lower specific wear rates and lower coefficients of friction, as well as higher tensile strength, elongation at break, and surface hardness, compared to those without surface treatment and those treated with 20 pph KBE903. In conclusion, the overall results suggested that the addition of Sm2O3 in the UHMWPE composites enhanced abilities to attenuate not only thermal neutrons but also gamma rays emitted after the neutron absorption by Sm, while the silane surface treatment of Sm2O3, using KBE903, considerably improved the processability, wear resistance, and strength of the composites.

X-ray Shielding, Mechanical, Physical, and Water Absorption Properties of Wood/PVC Composites Containing Bismuth Oxide.

The potential utilization of wood/polyvinyl chloride (WPVC) composites containing an X-ray protective filler, namely bismuth oxide (Bi2O3) particles, was investigated as novel, safe, and environmentally friendly X-ray shielding materials. The wood and Bi2O3 contents used in this work varied from 20 to 40 parts per hundred parts of PVC by weight (pph) and from 0 to 25, 50, 75, and 100 pph, respectively. The study considered X-ray shielding, mechanical, density, water absorption, and morphological properties. The results showed that the overall X-ray shielding parameters, namely the linear attenuation coefficient (µ), mass attenuation coefficient (µm), and lead equivalent thickness (Pbeq), of the WPVC composites increased with increasing Bi2O3 contents but slightly decreased at higher wood contents (40 pph). Furthermore, comparative Pbeq values between the wood/PVC composites and similar commercial X-ray shielding boards indicated that the recommended Bi2O3 contents for the 20 pph (40 ph) wood/PVC composites were 35, 85, and 40 pph (40, 100, and 45 pph) for the attenuation of 60, 100, and 150-kV X-rays, respectively. In addition, the increased Bi2O3 contents in the WPVC composites enhanced the Izod impact strength, hardness (Shore D), and density, but reduced water absorption. On the other hand, the increased wood contents increased the impact strength, hardness (Shore D), and water absorption but lowered the density of the composites. The overall results suggested that the developed WPVC composites had great potential to be used as effective X-ray shielding materials with Bi2O3 acting as a suitable X-ray protective filler.

Rare-Earth Oxides as Alternative High-Energy Photon Protective Fillers in HDPE Composites: Theoretical Aspects.

This work theoretically determined the high-energy photon shielding properties of high-density polyethylene (HDPE) composites containing rare-earth oxides, namely samarium oxide (Sm2O3), europium oxide (Eu2O3), and gadolinium oxide (Gd2O3), for potential use as lead-free X-ray-shielding and gamma-shielding materials using the XCOM software package. The considered properties were the mass attenuation coefficient (µm), linear attenuation coefficient (µ), half value layer (HVL), and lead equivalence (Pbeq) that were investigated at varying photon energies (0.001-5 MeV) and filler contents (0-60 wt.%). The results were in good agreement (less than 2% differences) with other available programs (Phy-X/PSD) and Monte Carlo particle transport simulation code, namely PHITS, which showed that the overall high-energy photon shielding abilities of the composites considerably increased with increasing rare-earth oxide contents but reduced with increasing photon energies. In particular, the Gd2O3/HDPE composites had the highest µm values at photon energies of 0.1, 0.5, and 5 MeV, due to having the highest atomic number (Z). Furthermore, the Pbeq determination of the composites within the X-ray energy ranges indicated that the 10 mm thick samples with filler contents of 40 wt.% and 50 wt.% had Pbeq values greater than the minimum requirements for shielding materials used in general diagnostic X-ray rooms and computerized tomography rooms, which required Pbeq values of at least 1.0 and 1.5 mmPb, respectively. In addition, the comparisons of µm, µ, and HVL among the rare-earth oxide/HDPE composites investigated in this work and other lead-free X-ray shielding composites revealed that the materials developed in this work exhibited comparable X-ray shielding properties in comparison with that of the latter, implying great potential to be used as effective X-ray shielding materials in actual applications.

Theoretical Determination of High-Energy Photon Attenuation and Recommended Protective Filler Contents for Flexible and Enhanced Dimensionally Stable Wood/NR and NR Composites.

This work aimed to theoretically determine the high-energy-photon-shielding properties of flexible wood/natural rubber (NR) and NR composites containing photon protective fillers, namely Pb, Bi2O3, or Bi2S3, using XCOM. The properties investigated were the mass attenuation coefficient (µm), linear attenuation coefficient (µ), and half value layer (HVL) of the composites, determined at varying photon energies of 0.001-5 MeV and varying filler contents of 0-1000 parts per hundred parts of rubber by weight (phr). The simulated results, which were in good agreement with previously reported experimental values (average difference was 5.3%), indicated that overall shielding properties increased with increasing filler contents but decreased with increasing incident photon energies. The results implied the potential of bismuth compounds, especially Bi2O3, to replace effective but highly toxic Pb as a safer high-energy-photon protective filler, evidenced by just a slight reduction in µm values compared with Pb fillers at the same filler content and photon energy. Furthermore, the results suggested that the addition of 20 phr wood particles, primarily aimed to enhance the rigidity and dimensional stability of Pb/NR, Bi2O3/NR, and Bi2S3/NR composites, did not greatly reduce shielding abilities; hence, they could be used as dimensional reinforcers for NR composites. Lastly, this work also reported the optimum Pb, Bi2O3, or Bi2S3 contents in NR and wood/NR composites at photon energies of 0.1, 0.5, 1, and 5 MeV, with 316-624 phr of filler being the recommended contents, of which the values depended on filler type and photon energy of interest.

Soil-to-plant transfer factors of natural radionuclides (226Ra and 40K) in selected Thai medicinal plants.

A soil-to-plant transfer factor (TF) is an important parameter that could be used to estimate radionuclides levels in medicinal plants. This work reports concentrations of natural radionuclides (226Ra and 40K) and TFs in six Thai medicinal plants grown in central Thailand using an HPGe gamma ray spectrometer. Either root, leaf, or flower parts of each medicinal plant were selected for use in the investigation according to their practical uses in traditional medicine. The results showed that due to K being essential in plants, 40K had higher arithmetic means of activity concentrations and geometric means of TFs (geometric standard deviations in parentheses) of 610 ±â€¯260 Bq kg-1 dry weight (DW) and 2.0 (1.4), respectively, than 226Ra, which had the activity concentrations and TFs of 4.8 ±â€¯2.6 Bq kg-1 DW and 0.17 (1.8), respectively. The results also showed that the leaves of medicinal plants had higher activity concentrations and TFs than root and flower parts, probably due to higher metabolic activities in leaves. Furthermore, there was good agreement between the results from the current work and other similar reports on medicinal plants. The information obtained from this work could strengthen knowledge of natural radionuclides in plants and particularly increase available TF data on Thai medicinal plants.