Short-lived Radionuclides Research Articles

Beyond Barnwell: Applying lessons learned from the Barnwell site to other historic underground nuclear tests at Pahute Mesa to understand radioactive gas-seepage observations

An underground nuclear explosion (UNE) generates radioactive gases that can be transported through fractures to the ground surface over timescales of hours to months. If detected, the presence of particular short-lived radionuclides in the gas can provide strong evidence that a recent UNE has occurred. By drawing comparisons between sixteen similar historical U.S. UNEs where radioactive gas was or was not detected, we identified factors that control the occurrence and timing of breakthrough at the ground surface. The factors that we evaluated include the post-test atmospheric conditions, local geology, and surface geology at the UNE sites. The UNEs, all located on Pahute Mesa on the Nevada National Security Site (NNSS), had the same announced yield range (20–150 kt), similar burial depths in the unsaturated zone, and were designed and performed by the same organization during the mid-to-late 1980s. Results of the analysis indicate that breakthrough at the ground surface is largely controlled by a combination of the post-UNE barometric pressure changes in the months following the UNE, and the volume of air-filled pore space above the UNE. Conceptually simplified numerical models of each of the 16 historical UNEs that include these factors successfully predict the occurrence (5 of the UNEs) or lack of occurrence (remaining 11 UNEs) of post-UNE gas seepage to the ground surface. However, the data analysis and modeling indicates that estimates of the meteorological conditions and of the post-UNE, site-specific subsurface environment including air-filled porosity, in combination, may be necessary to successfully predict late-time detectable gas breakthrough for a suspected UNE site.

Preparation of a Guideline for Radiation Safety Management of Short-Lived Radionuclides

Preparation of a Guideline for Radiation Safety Management of Short-Lived Radionuclides

One of the earliest refractory inclusions and its implications for solar system history

A ∼175 µm refractory inclusion, A-COR-01 from one of the least altered carbonaceous chondrites, ALHA 77307 (CO3.0), has been found to bear unique characteristics that indicate that it is one of the first solids to have formed at the very birth of the solar system while isotopic reservoirs were still evolving rapidly. Its core is composed mainly of hibonite and corundum, the two phases predicted to condense first from a gas of solar composition, and like many common types of Calcium-, Aluminium-rich Inclusions (CAIs) is surrounded by a rim of diopside.Core minerals in A-COR-01 are very 16O-rich (Δ17OCore = −32.5 ± 3.3 (2SD) ‰) while those in the rim display an O isotopic composition (Δ17ORim = −24.8 ± 0.5 (2SD) ‰) indistinguishable from that found in the vast majority of the least altered CAIs. These observations indicate that this CAI formed in a very 16O-rich reservoir and either recorded the subsequent evolution of this reservoir or the transit to another reservoir. The origin of A-COR-01in a primitive reservoir is consistent with the very low content of excess of radiogenic 26Mg in its core minerals corresponding to the inferred initial 26Al/27Al ratio ((26Al/27Al)0 = (1.67 ± 0.31) × 10−7), supporting a very early formation before injection and/or homogenisation of 26Al in the protoplanetary disk. Possible reservoir evolution and short-lived radionuclide (SLRs) injection scenarios are discussed and it is suggested that the observed isotope composition resulted from mixing of a previously un-observed early reservoir with the rest of the disk.

Radiogenic Power and Geoneutrino Luminosity of the Earth and Other Terrestrial Bodies Through Time

AbstractWe report the Earth's rate of radiogenic heat production and (anti)neutrino luminosity from geologically relevant short‐lived radionuclides (SLR) and long‐lived radionuclides (LLR) using decay constants from the geological community, updated nuclear physics parameters, and calculations of theβspectra. We track the time evolution of the radiogenic power and luminosity of the Earth over the last 4.57 billion years, assuming an absolute abundance for the refractory elements in the silicate Earth and key volatile/refractory element ratios (e.g., Fe/Al, K/U, and Rb/Sr) to set the abundance levels for the moderately volatile elements. The relevant decays for the present‐day heat production in the Earth (19.9 ± 3.0 TW) are from40K,87Rb,147Sm,232Th,235U, and238U. Given element concentrations in kg‐element/kg‐rock and densityρin kg/m3, a simplified equation to calculate the present‐day heat production in a rock isurn:x-wiley:ggge:media:ggge22244:ggge22244-math-0001The radiogenic heating rate of Earth‐like material at solar system formation was some 103to 104times greater than present‐day values, largely due to decay of26Al in the silicate fraction, which was the dominant radiogenic heat source for the first∼10 Ma. Assuming instantaneous Earth formation, the upper bound on radiogenic energy supplied by the most powerful short‐lived radionuclide26Al (t1/2= 0.7 Ma) is 5.5×1031 J, which is comparable (within a factor of a few) to the planet's gravitational binding energy.

Use of portable gamma spectrometers for triage monitoring following the intake of conventional and novel radionuclides

Current internal dosimetry monitoring programmes generally feature periodic measurements that are defined for the most commonly-encountered radionuclides. These programmes are not directly applicable to research centres that produce novel and short-lived radionuclides which are then used for the manufacture of radiopharmaceuticals, such as the CERN-MEDICIS facility hosted at CERN. This work presents an in vivo internal dosimetry programme based on the concept of triage monitoring. The programme allows to comply with the annual committed effective dose limit of E50=1 mSv by performing rapid gamma-spectroscopy screening measurements. Two portable spectrometers (HPGe- and NaI-based) were characterised using two different phantoms: a simplified model of the human torso and an anthropomorphic phantom allowing for customised source-filling geometries. The efficiencies of the spectrometers were determined using both phantoms and the minimum detectable activities were computed as a function of the measuring time for a selection of 21 among novel and conventional radionuclides. The minimum detectable activity was then used to calculate the minimum committed effective dose associated to each measurement for a realistic intake scenario. For a single screening measurement of 30 s performed at the end of the working day, the minimum detectable committed effective dose resulting from a radionuclide inhalation ranged between few μSv and hundreds of μSv for the majority of the considered radionuclides. The suggested approach allows to set up pragmatic in vivo measurements to monitor the workers’ internal contamination in research centres and industries where unsealed conventional and/or novel radionuclides may be handled.

Tracking natural and human impact on sediment dynamics using radiometric approach in Oualidia lagoon (Morocco)

ABSTRACT Chemical analysis, grain size distribution and short-lived radionuclides (210Pb and 137Cs) were combined to investigate the sedimentary processes in the Oualidia lagoon. Grain size and major elements profiles indicate an unexpected change in the layers characterising 1978 and 1986. Sediment accumulation rates (SAR) depth profiles exhibited the same behaviour and revealed two different sediment deposition conditions or regimes, involving modification of this ecosystem equilibrium. The profiles of major elements behave vertically almost the same as SAR, and grain size distribution. The observed changes reflect modifications in sediments supply and ecosystem drivers due to the variation of hydrodynamics conditions, confinement phenomena located in the upstream zone of the lagoon and to the various anthropogenic activities around the Oualidia lagoon.

Fallout from Nuclear Weapons Tests: Environmental, Health, Political, and Sociological Considerations.

The process of nuclear fission, which was discovered in 1938, opened the door to the production of nuclear weapons, which were used in 1945 by the United States against Japan in World War II, and to the detonation of >500 nuclear weapons tests in the atmosphere by the United States, the former Soviet Union, the United Kingdom, China, and France from 1946-1980. Hundreds of radionuclides, most of them short-lived, were produced in the atmospheric tests. The radioactive clouds produced by the explosions were usually partitioned between the troposphere and the stratosphere: the activity that remained in the troposphere resulted in local and regional fallout, consisting mainly of short-lived radionuclides and in relatively high doses for the populations residing in the vicinity of the test site, whereas the activity that reached the stratosphere returned to the ground with a half-life of ~1 y and was composed of long-lived radionuclides that contaminated all uncovered materials on Earth to a small extent and led to low-level irradiation of the world population for decades or more. The health effects resulting from exposure to radioactive fallout constitute, in most cases, small excesses over baseline rates for thyroid cancer and leukemia. An extra 49,000 cases of thyroid cancer would be expected to occur among the US population from exposure to radioactive fallout from the atmospheric nuclear weapons tests that were conducted at the Nevada Test Site in the 1950s. In addition, there could be as many as 11,000 deaths from non-thyroid cancers related to fallout from all atmospheric tests that were conducted at all sites in the world, with leukemia making up 10% of the total. Public concern arose in part from the secrecy that surrounded the nuclear testing programs and, for a long time, the poor communication regarding the consequences of the tests, both in terms of radiation doses and of health effects. Sociological and political pressures contributed to the establishment of programs of compensation for radiation exposures and evidence of radiation-induced diseases in countries that incurred significant fallout from nuclear weapons testing.

Thyroid Doses in Children from Radioiodine following the Accident at the Fukushima Daiichi Nuclear Power Plant

Background Huge amounts of radionuclides were released into the environment due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, which caused not only serious contamination on the ground, but also radiation exposure to the public. One problem that remains in performing the dose estimation is the difficulty of estimating the internal thyroid dose due to the intake of radioiodine (mainly, 131I) because of limitations to the human data available. Materials and Methods The relevant papers were collected and reviewed by the authors. The results of thyroid dose estimates from different studies were tabulated for comparison. Results and Discussion The thyroid dose estimates from the studies varied widely. The dose estimates by the United Nations Scientific Committee on the Effects of Atomic Radiation were higher than the others due to the ingestion dose being based on conservative assumptions. The dose estimates by Japanese experts were mostly below 20–30 mSv. The recent studies suggested that exposure on March 12, 2011 would be crucial for late evacuees from the areas near the FDNPP because of the possible intake of short-lived radionuclides other than 131I. Further multilateral studies are vital to reduce uncertainties in the present dose estimations. Conclusion The estimation of the thyroid doses to Fukushima residents still has many uncertainties. However, it is considered unlikely that the thyroid doses exceeded 50 mSv except in some extreme cases. Further multilateral studies are thus necessary to reduce the uncertainties in the present dose estimations. Keywords: Fukushima, Nuclear Accident, Iodine-131, Thyroid, Dose Estimation

Absorbed Dose Assessment from Short-Lived Radionuclides of Radon (222Rn) Decay Chain in Lung Tissue: A Monte Carlo Study

Introduction: Internal exposure to radon gas progeny can lead to serious biologic damages to the lung tissue. The aim of this study was to evaluate the absorbed dose by lung tissue due to the exposure from short-lived radioactive products of radon (222Rn) decay using Monte Carlo simulation. Material and Methods: A lung equivalent phantom including 64 air sacs was simulated by MCNPX code. Then, the absorbed dose from short-lived radioactive products of radon decay chain including 218Po, 214Po, 214Pb and 214Bi was calculated for both suspended and deposited states of daughter nuclides inside the lung. Results: The results showed that alpha decay has more contribution to the lung absorbed dose in comparison with the beta and gamma decay. Furthermore, the received dose by the lung was higher when the radon progenies were deposited inside the lung so that the maximum received dose to lung was 100 times higher than that of calculated in suspended state. Conclusion: Short-lived daughter radionuclides of radon decay chain, especially alpha emitter products, can be considered as dangerous internal radiation sources. The biological effects of these daughter radionuclides is more severe when are suspended inside the respiratory system.

Preclinical Evaluation of a Novel 18F-Labeled dTCO-Amide Derivative for Bioorthogonal Pretargeted Positron Emission Tomography Imaging.

Pretargeted positron emission tomography (PET) imaging based on the bioorthogonal inverse-electron-demand Diels–Alder reaction between tetrazines (Tz) and trans-cyclooctenes (TCO) has emerged as a promising tool for solid tumor imaging, allowing the use of short-lived radionuclides in immune-PET applications. With this strategy, it became possible to achieve desirable target-to-background ratios and at the same time to decrease the radiation burden to nontargeted tissues because of the fast clearance of small PET probes. Here, we show the synthesis of novel 18F-labeled dTCO-amide probes for pretargeted immuno-PET imaging. The PET probes were evaluated regarding their stability, reactivity toward tetrazine, and pharmacokinetic profile. [18F]MICA-213 showed an extremely fast kinetic rate (10,553 M–1 s–1 in 50:50 MeOH/water), good stability in saline and plasma up to 4 h at 37 °C with no isomerization observed, and the biodistribution in healthy mice revealed a mixed hepatobiliary and renal clearance with no defluorination and low background in other tissues. [18F]MICA-213 was further used for in vivo pretargeted immune-PET imaging carried out in nude mice bearing LS174T colorectal tumors that were previously treated with a tetrazine-modified anti-TAG-72 monoclonal antibody (CC49). Pretargeted μPET imaging results showed clear visualization of the tumor tissue with a significantly higher uptake when compared to the control.

Manipulating the In Vivo Behaviour of 68Ga with Tris(Hydroxypyridinone) Chelators: Pretargeting and Blood Clearance.

Pretargeting is widely explored in immunoPET as a strategy to reduce radiation exposure of non-target organs and allow the use of short-lived radionuclides that would not otherwise be compatible with the slow pharmacokinetic profiles of antibodies. Here we investigate a pretargeting strategy based on gallium-68 and the chelator THPMe as a high-affinity pair capable of combining in vivo. After confirming the ability of THPMe to bind 68Ga in vivo at low concentrations, the bifunctional THPMe-NCS was conjugated to a humanised huA33 antibody targeting the A33 glycoprotein. Imaging experiments performed in nude mice bearing A33-positive SW1222 colorectal cancer xenografts compared pretargeting (100 μg of THPMe-NCS-huA33, followed after 24 h by 8–10 MBq of 68Ga3+) with both a directly labelled radioimmunoconjugate (89Zr-DFO-NCS-huA33, 88 μg, 7 MBq) and a 68Ga-only negative control (8–10 MBq of 68Ga3+). Imaging was performed 25 h after antibody administration (1 h after 68Ga3+ administration for negative control). No difference between pretargeting and the negative control was observed, suggesting that pretargeting via metal chelation is not feasible using this model. However, significant accumulation of “unchelated” 68Ga3+ in the tumour was found (12.9 %ID/g) even without prior administration of THPMe-NCS-huA33, though tumour-to-background contrast was impaired by residual activity in the blood. Therefore, the 68Ga-only experiment was repeated using THPMe (20 μg, 1 h after 68Ga3+ administration) to clear circulating 68Ga3+, producing a three-fold improvement of the tumour-to-blood activity concentration ratio. Although preliminary, these results highlight the potential of THPMe as a 68Ga clearing agent in imaging applications with gallium citrate.

Activation study of a 15MeV LINAC via Monte Carlo simulations

Medical linear accelerators are increasingly used in radiotherapy. During the operational life of the accelerator, the different components of the LINAC head become radioactive due to photonuclear reactions. Activation induced has to be evaluated to assess not only the dose due to residual activation but also the amount of radioactive waste that has to be managed in the dismantling phase of the facility. The aim of this work is to define a Monte Carlo approach for the preliminary assessment of activation levels of a LINAC head. In this work the MC code FLUKA was used to simulate the Elekta Precise Treatment System 15 MeV LINAC installed in 2004 at the Bellaria Hospital (Bologna, IT) and routinely used in radiotherapy treatments. The activation of the LINAC head was assessed in each component after 15 years of operation. The main long-lived radionuclides found in head components are W-181, Re-184, Ni-63, Co-57, Fe-55, Mn-54, while short-lived radionuclides are W-187, W-185, W-179, Re-188, Re-186, Re-184, Cu-64, Cu-62, Ni-65, Ni-57, Cr-55 and Mn-56. As expected the most active component is the target while no considerable activation were found in the ionization chamber and in the wedge.

Measurement of S34(He3,p)Cl36 cross sections for nuclide enrichment in the early solar system

Isotopic studies of meteorites have provided ample evidence for the presence of short-lived radionuclides (SLRs) with half-lives of less than 100 Myr at the time of the formation of the solar system. The origins of all known SLRs is heavily debated and remains uncertain, but the plausible scenarios can be broadly separated into either local production or outside injection of stellar nucleosynthesis products. The SLR production models are limited in part by reliance on nuclear theory for modeling reactions that lack experimental measurements. Reducing uncertainty on critical reaction cross sections can both enable more precise predictions and provide constraints on physical processes and environments in the early solar system. This goal led to the start of a campaign for measuring production cross sections for the SLR $^{36}$Cl, where Bowers et al. found higher cross sections for the ${}^{33}$S($\alpha$,p)$^{36}$Cl reaction than were predicted by Hauser-Feshbach based nuclear reaction codes TALYS and NON-SMOKER. This prompted re-measurement of the reaction at five new energies within the energy range originally studied, resulting in data slightly above but in agreement with TALYS. Following this, efforts began to measure cross sections for the next most significant reaction for $^{36}$Cl production, $^{34}$S($^{3}$He,p)$^{36}$Cl. Activations were performed to produce 9 samples between 1.11 MeV/nucleon and 2.36 MeV/nucleon. These samples were subsequently measured with accelerator mass spectrometry at two labs. The resulting data suggest a sharper-than-expected rise in cross sections with energy, with peak cross sections up to 30\% higher than predictions from TALYS.

A mushy Earth's mantle for more than 500 Myr after the magma ocean solidification

SUMMARYIn its early evolution, the Earth mantle likely experienced several episodes of complete melting enhanced by giant impact heating, short-lived radionuclides heating and viscous dissipation during the metal/silicate separation. After a first stage of rapid and significant crystallization (Magma Ocean stage), the mantle cooling is slowed down due to the rheological transition, which occurs at a critical melt fraction of 40–50%. This transition first occurs in the lowermost mantle, before the mushy zone migrates toward the Earth's surface with further mantle cooling. Thick thermal boundary layers form above and below this reservoir. We have developed numerical models to monitor the thermal evolution of a cooling and crystallizing deep mushy mantle. For this purpose, we use a 1-D approach in spherical geometry accounting for turbulent convective heat transfer and integrating recent and solid experimental constraints from mineral physics. Our results show that the last stages of the mushy mantle solidification occur in two separate mantle layers. The lifetime and depth of each layer are strongly dependent on the considered viscosity model and in particular on the viscosity contrast between the solid upper and lower mantle. In any case, the full solidification should occur at the Hadean–Eoarchean boundary 500–800 Myr after Earth's formation. The persistence of molten reservoirs during the Hadean may favor the absence of early reliefs at that time and maintain isolation of the early crust from the underlying mantle dynamics.

Dose assessment for NPP staff for beyond design basis accident taking into account typical site infrastructure

Assessment of radiation effect on nuclear power plant staff was made for beyond design basis accident (4 hours period). The considered accident scenario includes emergency radionuclide emission through containment bypass. Assessment of radiation effect on NPP staff was done on the basis of radionuclide concentration distribution on site considering typical infrastructure. Concentration mapping was calculated by developed program module for COMSOL 3.5a application. The obtained data included average volume radionuclide activities in lower air layer, total inhalation dose, effective dose of external exposure, equivalent and effective dose in thyroid and total effective dose for NPP staff during beyond design basis accident. Doses from radioactive cloud (external exposure) and from inhalation (internal exposure) were estimated for the following radionuclides: 137Cs, 134Cs, 131I, 133I, 90Sr. In the case of selected beyond design basis accident the total effective dose of staff is 61,98 mSv for the first 4 hours after the accident beginning. This number is slightly above the threshold of the allowable annual dose limit for personnel in emergency situations (50 mSv). Taking into account that short-lived iodine radionuclides 131I и133I give the main contribution in the dose (50.23 mSv including 27.23 mSv for thyroid), such emergency actions as respiratory protection and iodine prophylaxis for the staff can significantly decrease the received doses.

Transmutation of 129I Containing Nuclear Waste by Proton Bombardment

As a long-lived nuclear waste, iodine (129I) which is primarily generated from nuclear fission of uranium or plutonium is considered harmful to human and environment. Therefore, proper steps are required to treat the radioactive isotope. In this work, we propose transmutation of I-129 isotope using cyclotron-based proton bombardment. The TALYS code was employed to calculate nuclear cross-sections of various nuclear reactions possible to transmute I-129 into shortlived radionuclides or stable isotopes. Twelve different nuclear reactions, namely (p,n), (p,2n), (p,3n), (p,np), (p,2np), (p,a), (p,d), (p,2p), (p,nα), (p,γ), (p,3He), and (p,t), which have significant cross-sections (greater than 1 mb) were analyzed. Based on the nuclear reactions, there were 6 possible stable isotopes produced from proton bombardment of 129I, such as 129Xe, 128Xe, 127I, 126Te, 125Te and 130Xe. Short-lived radionuclides such as 29mXe (half life = 8.88 days), 127Xe (half life = 36.35 days), 127mXe (half life = 62.9 seconds), 128I (half life = 24.99 minutes), 125mTe (half life = 57.40 days), 127Te (half life = 9.35 hours) and 127mTe (half life = 106.1 days) could also be possibly produced from the proton irradiation of 129I nuclear waste. To sum up, the longest radionuclide could be generated from proton bombardment of 129I nuclear waste is 127mTe (half life = 106.1 days), which is a lot shorter than 129I (half life = 1.57x107 years). This theoretical study indicates that transmutation of 129I nuclear waste by proton bombardment into short-lived radionuclides is greatly feasible. Current available cyclotrons in Indonesia may be employed to help transmute 129I into short-lived radionuclides or stable isotopes. This theoretical study can be used as a reference for future 129I nuclear waste if proton beams are employed in the transmutation.

Preparation of Educational Materials for Safety Handling of Short-lived Radionuclides

Preparation of Educational Materials for Safety Handling of Short-lived Radionuclides

Estimation of Radiation Doses for a Case-control Study of Thyroid Cancer Among Ukrainian Chernobyl Cleanup Workers.

Thyroid doses were estimated for 607 subjects of a case-control study of thyroid cancer nested in the cohort of 150,813 male Ukrainian cleanup workers who were exposed to radiation as a result of the 1986 Chernobyl nuclear power plant accident. Individual thyroid doses due to external irradiation, inhalation of I and short-lived radioiodine and radiotellurium isotopes (I, I, I, Te, and Te) during the cleanup mission, and intake of I during residence in contaminated settlements were calculated for all study subjects, along with associated uncertainty distributions. The average thyroid dose due to all exposure pathways combined was estimated to be 199 mGy (median: 47 mGy; range: 0.15 mGy to 9.0 Gy), with averages of 140 mGy (median: 20 mGy; range: 0.015 mGy to 3.6 Gy) from external irradiation during the cleanup mission, 44 mGy (median: 12 mGy; range: ~0 mGy to 1.7 Gy) due to I inhalation, 42 mGy (median: 7.3 mGy; range: 0.001 mGy to 3.4 Gy) due to I intake during residence, and 11 mGy (median: 1.6 mGy; range: ~0 mGy to 0.38 Gy) due to inhalation of short-lived radionuclides. Internal exposure of the thyroid gland to I contributed more than 50% of the total thyroid dose in 45% of the study subjects. The uncertainties in the individual stochastic doses were characterized by a mean geometric standard deviation of 2.0, 1.8, 2.0, and 2.6 for external irradiation, inhalation of I, inhalation of short-lived radionuclides, and residential exposure, respectively. The models used for dose calculations were validated against instrument measurements done shortly after the accident. Results of the validation showed that thyroid doses could be estimated retrospectively for Chernobyl cleanup workers two to three decades after the accident with a reasonable degree of reliability.

Accounting for ingrowth of radioactive progeny in dose assessments: generic weighting factors for dose coefficients

In this paper, we describe a practical and convenient method to include the contribution of the ingrowth of radioactive progeny in dose assessments of the corresponding parent nuclides. This method modifies the dose coefficients (DCs) of parent nuclides by adding weighted DCs of the corresponding daughter nuclides to them. Based on the decay kinetics of serial nuclear transformations, the progeny weighting factors, with values between 0 and 1, are derived by analysis of the time-integrated activity of each nuclide in the (branched) decay chain headed by a parent nuclide. Using the electronic, nuclear-decay database of Publication 107 of the International Commission on Radiological Protection (ICRP 2008), DC weighting factors for annual dose assessments are calculated for all daughter radionuclides in the decay chains and are tabulated in this paper. Weighting factors based on integration periods other than one year, ranging from 1 h–70 years, are also provided (see the supplementary material). With a priori established weighting factors, dose assessments become significantly simplified by considering the decay kinetics of only the parent nuclides and by applying the modified DCs. This ensures that the ingrowth of progeny is taken into account realistically. In some cases, one requires a conservative estimate of the dose, for instance when dealing with issues of the clearance of materials under regulatory control. Therefore, we adapted the weighting-factor method to derive conservative DC weighting factors for dose evaluations. These values are calculated for various integration periods and compared with those from an existing method adopted by the Euratom Article 31 Group of Experts and by the International Atomic Energy Agency. Identical progeny weighting factors are obtained for long-lived parent radionuclides, whereas for short-lived parent radionuclides, the new method can yield significantly larger values. For example, the weighting factor of I-131 (daughter of parent Te-131) increases from 0.002 to 1.0 based on an integration period of 1 year. The progeny DC weighting factors, derived based on nuclear transformations in exit-only decay chains, may not always be suitable for use in radiological dose evaluations. For instance, when environmental removal pathways are dominant, the application of these weighting factors may have its limitations. This paper, therefore, provides guidance on the proper selection and application of weighting factors.

Nanohydroxyapatite and its textures as potential carriers of promising short-lived lead isotopes

The possibility of sorption and cocrystallization binding of lead(n) with nanohydroxyapatite (HAP) acting as a potential carrier of short-lived lead radionuclides 211,212Pb was studied. The peculiarities of the kinetics were revealed, and the isotherms of sorption of lead ions on hydroxyapatite with different textures were constructed. A multistage sorption mechanism accompanied by a change in the structure and morphology of the sorbent was studied. The possibility of the formation of a new phase (hydroxypyromorphite) of lead during the sorption and cocrystallization interaction was shown. The introduction of lead into the synthesis of HAP at the early stages of crystallization exerts the highest effect on its morphology and structure. The optimization of the formation of the HAP-Pb composite over the course of the process will make it possible to use the short-lived 211Pb radionuclide in subsequent experiments.