Α-emitting Nuclides Research Articles

Comparison of Nuclear Medicine Therapeutics Targeting PSMA among Alpha-Emitting Nuclides.

Currently, targeted alpha therapy (TAT) is a new therapy involving the administration of a therapeutic drug that combines a substance of α-emitting nuclides that kill cancer cells and a drug that selectively accumulates in cancer cells. It is known to be effective against cancers that are difficult to treat with existing methods, such as cancer cells that are widely spread throughout the whole body, and there are high expectations for its early clinical implementation. The nuclides for TAT, including 149Tb, 211At, 212/213Bi, 212Pb (for 212Bi), 223Ra, 225Ac, 226/227Th, and 230U, are known. However, some nuclides encounter problems with labeling methods and lack sufficient preclinical and clinical data. We labeled the compounds targeting prostate specific membrane antigen (PSMA) with 211At and 225Ac. PSMA is a molecule that has attracted attention as a theranostic target for prostate cancer, and several targeted radioligands have already shown therapeutic effects in patients. The results showed that 211At, which has a much shorter half-life, is no less cytotoxic than 225Ac. In 211At labeling, our group has also developed an original method (Shirakami Reaction). We have succeeded in obtaining a highly purified labeled product in a short timeframe using this method.

Development of decontamination and detergents for the nuclear industry

At the enterprises of the radiochemical industry in the world, the task is to clean the technological and research equipment, overalls, and personnel from contamination with radioactive products. This task is especially relevant in case of emergencies, for example, such as an accident at a nuclear power plant in Fukushima, Japan. A review of the deactivation methods currently used is reviewed. It has been shown that the most typical pollutants are mixtures of radionuclides 137Cs, 144Ce, 144Pr, 90Sr, and 239Pu. All these elements are prone to the formation of chelate complexes. Therefore, complexing substances should be an essential component of deactivation solutions that form stable, water-soluble complex compounds with these radionuclides. When creating the recipe, we chose those complexing agents with the most persistent complex compounds with the expected pollutants. For research and testing in real conditions, we have prepared three types of technical detergents of various compositions with the code name MDS for decontaminating various surfaces, equipment, and workwear. The composition of these preparations consists mainly of an optimized mixture of surfactants, complexing agents, corrosion inhibitors, and processing aids. The studies were conducted to evaluate the possibility of using these funds for deactivation of premises, equipment, washing clothes in the Federal Unitary Enterprise "Mayak" and at its branch NIKIET in town Zarechny at Beloyarskyaya Nuclear Power Station in Russia. The effectiveness of deactivation was judged by the amount of residual contamination of the surface of the samples. The deactivating ability of MDS preparations for stainless, carbon steel, and plastic contaminated with β- and α-emitting nuclides was tested. The possibility of using MDS detergents for the deactivation of platinum ampoules stored as radioactive waste was assessed. The possibility of using MDS detergents for the deactivation of fabric materials, including underwear and work clothes, was also evaluated. The tests showed the high efficiency of the developed detergent MDS compared to the existing and currently used deactivation agents.

Development of Total Decay Energy Spectrometry of α-Emitting Radionuclides Using Metallic Magnetic Calorimeters

Total decay energy spectrometry with cryogenic detectors is a promising technique for radionuclide analysis of α-emitting nuclides. The radioactive sample is embedded in the detector absorber, and the total decay energy for each disintegration is measured as a temperature elevation. We are developing this technique with metallic magnetic calorimeters (MMCs). The main condition of this technique is a detection efficiency close to unity. However, some α-emitting nuclides emit intense γ-rays that can partially escape from the absorber. So a feasibility study for several nuclides has been carried out based on Monte Carlo simulations of the detection efficiency and numerical calculations of the expected energy resolution to identify the radionuclides that can potentially be measured. Furthermore, an MMC prototype has been built and tested. The total decay energy spectrum of Po-210 was measured, and a FWHM energy resolution of 1.25 keV at 5.4 MeV was obtained and a Gaussian width at half maximum of 0.827 (5) keV. The baseline FWHM energy resolution is 207 eV, consistent with the resolution obtained on low-energy L X-rays in the same spectrum at 14 keV.

Extraction of Long-Lived Radionuclides from High-Level Alkaline Waste with p-Alkylcalix[8]arene

p-Alkylcalix[8]arene containing six tert-butyl and two isononyl groups on the upper rim of the macrocycle was suggested for extraction recovery of long-lived β- and α-emitting nuclides from high-level alkaline waste. The influence of the compositions of the organic and aqueous phases on the extraction efficiency was examined. After four contacts of the extractant solution with the real high-level alkaline solution, the activity of the major dose-producing radionuclide, 137Cs, decreases by two orders of magnitude, and that of α-emitting radionuclides, by a factor of 3.5–40 depending on the initial solution pretreatment. The degree of stripping of the radionuclides after the first contact of the loaded organic phase with the acid exceeds 99%. p-Alkylcalix[8]arenes show promise for treatment of high-level alkaline waste at the Mayak Production Association.

Present and Future Prospects of Radiation Therapy Using α-Emitting Nuclides.

Therapy with α-radiation has issues associated with internal exposure; its clinical use has been avoided. However, phase III clinical tests of the α-emitting nuclide 223Ra on patients with cancer have been conducted, and results were reported in 2011 to 2012. Since then, research has being carried out on targeted internal therapy by introducing α-emitting nuclides directly into the cancers. For many decades, nontargeted radon therapy has been carried out and is controversial because its mechanism of action is stimulation. The low-level radiation sends powerful signals to upregulate many biological protection systems, which protect against the effects of radiogenic and nonradiogenic toxins. These vital systems prevent, repair, and remove DNA and other biomolecular damage being produced endogenously at a very high rate by the very abundant reactive oxygen species associated with aerobic metabolism. Stimulation of protection systems results in beneficial effects, including a lower risk of cancer. This article reports the results of treatments on 4 patients with cancer and reviews the clinical use of α-radiation from 223Ra and radon. It discusses the prospect of using the novel 225Ac-prostate-specific membrane antigen ligand-617 ligand as a therapeutic agent for prostate cancer. It presents a new treatment system that we developed, α-Radiorespiro-Rn, which seems to be extremely effective in treating cancer.

Decontamination of metal items with consideration of the secondary sorption of radionuclides

Decontamination of the surfaces of weakly curved fragments of plutonium-contaminated metal items with pulsed oscillating flow of decontaminating solutions in a pulse decontamination installation is considered. Decontamination of the fragments was performed with an aqueous solution of the composition 5% HNO3 + 0.2% NaF, used for decontamination of metal surfaces from radionuclides. It was found that the reverse contamination of the surface of the treated items in the course of washing out α-emitting nuclides that tend to polymerization and to secondary sorption on the surface of materials should be taken into account.

Chemical endurance of polymeric compounds containing radioactively contaminated spent vacuum oil

Oil-absorbent suspension was incorporated in a matrix material based on epoxy-4,4′-isopropylidenediphenol resin under laboratory conditions. The following powder materials were used as absorbents: magnesium and calcium oxides, Taunit, Aerosil, high-reactivity carbon mixture, and N910 synthetic polymer. Experiments were performed with radioactively contaminated spent VM-4 vacuum oil from chemicalmetallurgical production. The weight fraction of oil in the compounds was varied from 19 to 39%. The chemical endurance of the compound samples under the conditions of prolonged keeping in aqueous medium was examined. The results obtained show that all the polymeric samples ensure sufficiently strong fixation of oil and α-emitting nuclides, preventing their release into the leaching medium. The degree of leaching of oil and α-emitting nuclides from all the examined compounds in 90 days did not exceed 0.23 and 0.10%, respectively.

Determination of the weight and composition of the precipitates formed in the course of dissolution of irradiated WWER oxide fuel

The amount and composition of insoluble precipitates formed in the course of dissolution of spent fuel samples with the burn-up from 15 to 54 MW day (kg U)−1 were examined. The weight of the insoluble precipitates was from 0.03 to 0.44% of the fuel weight. The major elements determining the composition of the precipitates were platinum group metals (Pd, Rh, Ru), Zr, and Mo. The specific β- and α-activity of the precipitates obtained was 30–840 and 0.01–8 Ci kg−1, respectively. The major factor determining the concentration of α-emitting nuclides is the fuel burn-up. Depending on the dissolution conditions, the U content was 0.2–4, and the Pu content, 0.1–3%. The weight of secondary precipitates was from 0.005 to 0.3% of the irradiated fuel weight, or 11–50% of the total weight of the precipitates obtained in the experiments. The specific β-activity of the secondary precipitates obtained varies from 5 to ∼300 Ci kg−1 and is determined by the same radionuclides as in the primary precipitates. The α-activity of the secondary precipitates increases with the burn-up and amounts to 0.1–30 Ci kg−1. The values obtained vary only slightly depending on the dissolution conditions and on the time of solution keeping before control filtration.

Simultaneous determination of 237Np, 238–240Pu and 241Am in HNO 3 solution by combining extraction, liquid scintillation counting, and α spectrometry

α Spectrometry is one of the most important and sensitive techniques for the assay of α-emitting nuclides, but various complicated procedures are often required for preparation of uniform thin plate source. Liquid scintillation counting (LSC) with pulse shape analysis (PSA) combining extraction is much simpler, more rapid and accurate technique, but the extraction processes are often very long. By combining extraction, LSC with PSA, and α spectrometry, we proposed a new approach to determine 237Np, 238 – 240Pu and 241Am. The new approach includes an extraction process of three steps for blind samples or of only one step for those samples without tailing interference with α spectra. Moreover, no complicated procedure is required for α plate source preparation because even non-uniform plate source is feasible for the new approach. The approach has taken advantages of high counting efficiency (nearly 100%) of LSC for α-radiation, high energy resolution of α spectrometry and high recovery yield of actinides by trialkylphosphine oxide (TRPO) extraction. The approach with one step extraction can be expected to determine 237Np, 238 – 240Pu, 241Am and 244Cm simultaneously.

Determination of the plutonium content in samples from a 30-km zone around the Chernobyl nuclear power plant

A method of determining the content of α-emitting plutonium isotopes according to the characteristic Lx radiation line emitted from uranium in samples taken from the environment is proposed. Comparing the method decribed and the standard radiochemical determination of plutonium isotopes for soil samples taken from a 5-km zone around the Chernobyl nuclear power plant showed that the results are in good agreement with one another. The concentration of plutonium and americium in the zones with high contamination with transuranium nuclides is measured. It is established that the migration rate of americium is the same as that of plutonium. It is shown that about 90% of the α-emitting nuclides are located at depths of 5–10 cm.

Application of α/β discrimination in liquid scintillation counting for the purity control of 99mTc medical solutions

99mTc is a widely used nuclide in nuclear medicine for diagnosis. 99mTc solutions are eluted from 99Mo/ 99mTc generators as sodium chloride solutions. As the 99Mo source is a fission product extracted from the reprocessing of nuclear fuel, one might expect the presence of radioactive impurities. One point of special concern described in the 1997 European Pharmacopoeia (1996) is the possible contamination in α-impurities (U, Pu, Am, Cm, …) which must be very low. In order to check this impurity concentration, we used liquid scintillation counting (LSC) with α/β discrimination and a commercial extractive scintillator, Alphaex®. We first made measurements using synthetic mixtures of α and β-emitters and then using the real effluent. This paper describes the measurement procedure used with the optimum chemical conditions for a correct extraction of the α-emitting nuclides. The sensitivity of the method is also described from the measurements made using the real effluent with an addition of a quantitative amount of α particle contamination.

Radioactivity in some gas-flow lantern mantles produced by different manufacturers

Groups of gas-flow lantern mantles of different manufacturers were subjected to radiometric investigation to evaluate the radiological hazards arising from their usage. Interest was given to the long-lived radionuclides found, which were the α-emitting nuclides of thorium and 228Ra. Thorium isotopes were analyzed by α-spectrometry whereas 228Ra was analyzed by γ-spectrometry. The results show that mantles from different manufacturers contain mainly natural thorium with levels that fluctuate over a very wide range, from 350 to 4560 Bq/mantle. For the same manufacturer, thorium levels vary strongly in mantles of different batches and even from the same batch. On burning the mantle, a 10–20% reduction in the thorium activity takes place in the first few minutes. The mantle containers were almost free from significant thorium contamination. Results are given and discussed in detail.

Preparation and characterization of234U for mass spectrometry and alpha-spectrometry

234U of high isotopic purity (>99 atom%) as well as of high radiochemical, purity was separated from aged238Pu prepared by neutron irradiation of237Np. Methodologies based on ion exchange and solvent extraction procedures were used to achieve high decontamination factor from238Pu owing to the very high α-specific activity of238Pu (2800 times) in comparison to that of234U. Isotopic composition of purified234U was determined by thermal ionisation mass spectrometry. Alpha spectrometry was used for checking the radiochemical purity of234U with respect to concomitant α-emitting nuclides. The separated234U will be useful for different investigations using mass spectrometry and alpha spectrometry.

Sensitivity and Precision of Determination of α-Emitting Nuclides of Radium in Water Samples by α-Spectrometry

Article Sensitivity and Precision of Determination of α-Emitting Nuclides of Radium in Water Samples by α-Spectrometry was published on October 1, 1996 in the journal Radiochimica Acta (volume 75, issue 1).

Alpha-emitting radionuclide contents in food samples as related to the Chernobyl accident

As a preliminary survey to establish intake of α-emitting nuclides, in particular239,240Pu, from a daily diet for inhabitants living near the Chernobyl reactor site, some kinds of food samples including total diet samples were collected in the Chernobyl (Ukraine) area and in the Ibaraki prefecture (Japan). Plutonium-239 and 240 were determined together with naturally occurring α-emitters226Ra and U isotopes (234U,235U and238U) by α-spectrometry after chemical separation. In most of the samples studied,239,240Pu was less than the detectable amount, but in some mushrooms from the Ukraine it was found to be 41.6 mBq kg−1 (wet mass) with a high activity ratio(0.58±0.08) of238Pu/239,240Pu, indicating that nearly 100% of the239,240Pu was attributable to the accident. Concentrations of226Ra and238U varied largely, depending on the samples. The measured activity ratios of235U/238U for some samples showed the isotopic composition of natural uranium.

Diffusion thermique d'elements actinides implantes par reaction nucleaire dans le tantale

Thermal diffusion of actinides elements has been studied using α-emitting nuclides implanted in tantalum metal by nuclear recoil, with an automatic apparatus on line with heavy ion accelerators. The depth of implantation and the quantity of radionuclides are determined by α radiometric study. Energies of activation are then deduced from the quantity of atoms present in tantalum after heating at various temperatures. The experimental energies measured are compared with respect to the thermodynamic potential functions.

Measurements of α-emitting plutonium and americium in the intertidal sands of West Cumbria, UK

Samples of surface sand and sand cores were collected from intertidal regions of west Cumbria-between Silloth and Walney Island (including the Duddon Estuary) between 1982 and 1984 and analysed for 238Pu, 239+240Pu and 241Am. Generally, more than 95% of the α-emitting transuranic nuclides were associated with the sand and less than 5% with entrained silt. The greatest concentrations of both plutonium and americium were found at Braystones. Concentrations declined with distance from the Sellafield Works. The largest actinide deposits occurred at Drigg (320 and 720 kBq m −2 of 239+240Pu and 241Am respectively). The integrated deposits in intertidal sand between Silloth and Walney Island were about 4·2 and 7·0 TBq respectively, which represent about 1% of the total α-emitting activity discharged to sea from Sellafield Works up to 1982. The corresponding value for the Duddon Estuary is about 0·3%. Only on beaches close to Sellafield did levels of man-made α-emitters exceed those of natural α-emitting nuclides. The radiological consequences of the intertidal inventory of plutonium and americium are shown to be very small and much less than from the seafood pathway.

Diffusion thermique de l'uranium, du plutonium, du curium dans le tantale

Diffusion of uranium, plutonium and curium has been studied using α-emitting nuclides implanted in tantalum metal by nuclear recoil. The energies measured experimentally were 133, 253 and 274 kJ mol −1 respectively.

Alpha-particle spectrometry and its applications

Alpha-particle spectrometry is a precise and sensitive technique which has many applications in the nuclear-energy field. Using a thin, uniform source with a suitable detector and ancillary electronic equipment, the constituents of a mixture of α-emitting nuclides can be accurately assayed both at activity levels found in the environment and in reprocessing-plant solutions. Factors influencing the achievement of high-quality data and some examples of applications are described.

Transuranic nuclides in plaice (Pleuronectes platessa) from the North-Eastern Irish Sea

The concentrations of a number of α-emitting nuclides, 238Pu, 239/240Pu, 241Am, 242Cm and 243/244Cm have been determined in the organs of plaice, Pleuronectes platessa L., caught in the vicinity of a nuclear fuel reprocessing plant. Fish were taken for analysis every 3 months for a period of 2 years. During this period, the highest concentrations of plutonium and americium nuclides were found in the kidney and the lowest in muscle. In all of the organs analysed, the concentrations of americium were greater than those of plutonium: they were also greater than plutonium when related to the rates of discharge of these two elements and gave higher concentration factors over samples of filtered shore-line sea water taken from the area.