32P Activity Research Articles

Alternatives to NIST Cf-252 Iirradiations for Transfer Calibration of S-32 Neutron Monitors

Gas-flow proportional counting systems are used by the Radiation Metrology Laboratory (RML) at Sandia National Laboratories for reactor fluence monitoring with the 32S(n,p)32P reaction. Calibration of these systems has traditionally been accomplished by fluence-transfer irradiations at the NIST 252Cf facility. Such calibrations have become increasingly difficult as the NIST 252Cf source decayed to unusable levels. To minimize the risk to the testing programs from an inability to properly calibrate these systems, the RML has developed two alternative calibration techniques: 1) development and implementation of certified 32P sources for activity calibrations and subsequent calculation of neutron fluence, and 2) direct counting of non-certified reactor-irradiated sulfur pellets by liquid scintillation counting to determine 32P activity for the subsequent calibration of gas-flow proportional counters. Preliminary comparisons show that the several calibration methods are capable of overall uncertainties within about 5 percent.

Assessment of Seasonal Variability in Phosphorus Biodynamics by Cosmogenic Isotopes 32P, 33P around Balaklava Coast.

The sorption efficiency of phosphorus from seawater by aluminum oxide and sorbents based on Fe(OH)3 obtained by various methods (using prepared sodium ferrate or precipitation of Fe(OH)3 with ammonia) was assessed. It was shown that phosphorus was recovered most efficiently at a seawater flow rate of one-to-four column volumes per minute with a sorbent based on hydrolyzed polyacrylonitrile fiber with a precipitation of Fe(OH)3 with ammonia. Based on the results obtained, a method for phosphorus isotopes recovery with this sorbent was suggested. Using this method, the seasonal variability of phosphorus biodynamics in the Balaklava coastal area was estimated. For this purpose, the short-lived isotopes of cosmogenic origin 32P and 33P were used. Volumetric activity profiles of 32P and 33P in particulate and dissolved forms were obtained. Based on 32P and 33P volumetric activity, indicators of phosphorus biodynamics were calculated: the time, rate, and degree of phosphorus circulation to inorganic and particulate organic forms. In spring and summer, elevated values of phosphorus biodynamic parameters were determined. This is explained by the peculiarity of the economic and resort activities of Balaklava, which negatively affect the state of the marine ecosystem. The results obtained can be used to assess the dynamics of changes in the content of forms of dissolved and suspended phosphorus, and the biodynamic parameters when performing a comprehensive environmental assessment of the state of coastal waters.

Reductive dissolution of iron phosphate modifies rice root morphology in phosphorus-deficient paddy soils

Root morphology reflects plant adaptations to phosphorus (P) deficiency. We hypothesized that changes in rice root morphology reflect P deficiency decrease after ferric iron (Fe(III))-bound phosphate (Fe–P) dissolution in low-redox paddy soils. We developed a novel in-situ32P phosphor-imaging approach under flooding to estimate P uptake by rice roots released from Fe–P dissolution. 32P-labeled ferrihydrite (31 mg P kg−1) was supplied either (1) in polyamide mesh bags (30 μm mesh size) to prevent roots but not microorganisms from direct Fe–P mobilization, or (2) directly mixed with soil to enable roots and microorganisms unrestricted access to the Fe–P. The establishment of low redox conditions (Eh values between −176 and −224 mV) drove the reductive dissolution of Fe–P. Rice root-derived organic acids alone were unable to control Fe–P dissolution, and Fe(III) reduction is predominately a microbially-mediated process. Direct root access to Fe–P raised both the number and mean diameter of crown roots and root tips, and increased P uptake by 149–231%. Crown root elongation rate, 32P activities along roots and root tips were 5–133% higher when roots directly accessed Fe–P compared to Fe–P excluded from roots in mesh bags. Iron accumulation on roots depended on the rice growth stage, but not on their access to Fe–P. Roots’ access to Fe–P increased rice crown roots elongation and branching and increased P accessibility under P deficiency.

A rapid screening method for 32P in urine samples by TDCR Cerenkov measurement

Based on triple-to-double coincidence ratio (TDCR) Cerenkov measurement, a rapid screening method for the analysis of 32P in urine samples was developed. In this method, urine samples were pre-treated to decompose organics by adding concentrated HCl and H2O2 with heating at 60 °C for 1 h and at 90 °C for 30 min. Acetic acid was then added, and the samples were cooled to ambient temperature before counting in Cerenkov mode using a Hidex 300SLL TDCR liquid scintillation counter. An empirical formula between Cerenkov counting efficiency of 32P and the TDCR value was established to correct for color quenching present in the processed samples. The performance of the method was examined using several sets of urine spike samples, and the measurements agreed very well with the expected 32P activities. The detection limit of 11 Bq L−1 was achieved for 15 mL of urine sample with a counting time of 30 min.

The role of organic acids on the uptake and relationship of phosphorus and zinc in corn (Zea mays L.) by application of 32P and 65Zn radioisotopes

ABSTRACTTo investigate the effect of oxalic and citric acids on the uptake and relationship of phosphorus and zinc in corn (Zea mays L.), some greenhouse experiments were performed by individual and combined application of monopotassium phosphate [KH232PO4] and zinc sulfate [65ZnSO4.7H2O] fertilizers in microcosm. For this purpose after planting corn seeds, solutions of phosphorus (32P) and zinc (65Zn) (14 and 2 M) and organic acids treatments (1 and 10 mM) were injected in microcosms at suitable times. Then, plants were harvested, digested, extracted, and activity of 32P and 65Zn was measured in samples. Results revealed that the highest uptake of 32P in shoots was 18.8% and observed at 10 mM concentration of oxalic acid. But no effect on 65Zn uptake was seen and the highest uptake was observed in control (1.27%). The highest uptake of 32P and 65Zn in plant shoots and roots was observed at 10 mM concentration of oxalic and citric acids, respectively.

Herbivorous snails can increase water clarity by stimulating growth of benthic algae

Eutrophication in shallow lakes is characterized by a switch from benthic to pelagic dominance of primary productivity that leads to turbid water, while benthification is characterized by a shift in primary production from the pelagic zone to the benthos associated with clear water. A 12-week mesocosm experiment tested the hypothesis that the herbivorous snail Bellamya aeruginosa stimulates the growth of pelagic algae through grazing on benthic algae and through accelerating nutrient release from sediment. A tube-microcosm experiment using 32P-PO4 as a tracer tested the effects of the snails on the release of sediment phosphorus (P). The mesocosm experiment recorded greater total nitrogen (TN) concentrations and a higher ratio of TN:TP in the overlying water, and a higher light intensity and biomass of benthic algae as measured by chlorophyll a (Chl a) in the snail treatment than in the control. Concentrations of total phosphorus (TP), total suspended solids (TSSs), and inorganic suspended solids (ISSs) in the overlying water were lower in the snail treatment than in the control, though no significant difference in Chl a of pelagic algae between the snail treatment and control was observed. In the microcosm experiment, 32P activity in the overlying water was higher in the snail treatment than in the control, indicating that snails accelerated P release from the sediment. Our interpretation of these results is that snails enhanced growth of benthic algae and thereby improved water clarity despite grazing on the benthic algae and enhancing P release from the sediment. The rehabilitation of native snail populations may therefore enhance the recovery of eutrophic shallow lakes to a clear water state by stimulating growth of benthic algae.

Reactor production of 32P for medical applications: an assessment of 32S(n,p)32P and 31P(n,γ)32P methods

The article describes a comparative study carried out on the reactor production of 32P by two different processes, namely, 32S(n,p)32P and 31P(n,γ)32P with a view to determine the merits and bottlenecks of each method and assess the usefulness of 32P obtained from each of the processes. In a typical batch, 250 g of elemental sulfur when irradiated at a fast neutron flux of ~8 × 1011 n cm−2 s−1 for 60 days, after chemical processing provided about 150 GBq(4.05Ci) of 32P having specific activity of 200TBq(5500Ci)/mmole. On the other hand, irradiation of 0.35 g of red phosphorus at a fast neutron flux of ~7.5 × 1013 n cm−2 s−1 for a period of 60 days gave 75 GBq(2.02Ci) of 32P of specific activity 7 GBq(190mCi)/mol-1. While the specific activity of 32P obtained from 32S(n,p)32P is superior to that obtained from the 3lP(n,γ)32P process, the requirement of elaborate target processing steps involving distillation and purification emerged as a deterrent that limits its widespread adaptability. Both the production routes offer 32P of acceptable quality amenable for medical applications although their specific activity differs.

Effects of deposit-feeding tubificid worms and filter-feeding bivalves on benthic-pelagic coupling: Implications for the restoration of eutrophic shallow lakes

Benthic-pelagic coupling is a key factor in the dynamics of shallow lakes. A 12-week mesocosm experiment tested the hypothesis that deposit-feeding tubificid worms stimulate the growth of pelagic algae while filter-feeding bivalves promote the growth of benthic algae, using the deposit-feeding tubificid Limnodrilus hoffmeisteri and the filter-feeding bivalve Anodonta woodiana. A tube-microcosm experiment using a 32P radiotracer tested for differential effects of tubificids and bivalves on the release of sediment phosphorus (P). In this experiment A. woodiana was replaced by Corbicula fluminea, a smaller bivalve from the same functional group whose size was more appropriate to the experimental tubes needed for the tracer study. The first experiment recorded greater nutrient concentrations in the overlying water, higher biomass of pelagic algae as measured by chlorophyll a (Chl a), lower light intensity at the sediment and lower biomass of benthic algae in the worm treatments than in the controls, while nutrients and Chl a of pelagic algae were lower and the light intensity and Chl a of benthic algae were higher in the bivalve treatments than in the controls. In the second experiment, 32P activity in the overlying water was higher in both treatments than in the controls, but highest in the worm treatment indicating that both animals accelerated P release from the sediment, with the biggest effect associated with the presence of worms. Our study demonstrates that worms promote pelagic algal growth by enhancing the release of sediment nutrients, while bivalves, likely through their grazing on pelagic algae increasing available light levels, stimulate benthic algal growth despite enhanced P release from the sediment and thus aid the establishment of clear water states. The rehabilitation of native bivalve populations may therefore enhance the recovery of eutrophic shallow lakes.

Accidental neutron dosimetry with human hair

Human hair contains sulfur, which can be activated by fast neutrons. The 32S(n,p)32P reaction with a threshold of 2.5MeV was used for fast neutron dose estimation. It is a very important parameter for individual dose reconstruction with regards to the heterogeneity of the neutron transfer to the human body. Samples of human hair were irradiated in a radial channel of a training reactor VR-1. 32P activity in hair was measured both, directly by means of a proportional counter, and as ash dispersed in a liquid scintillator. Based on neutron spectrum estimation, a relationship between the neutron dose and induced activity was derived. The experiment verified the practical feasibility of this dosimetry method in cases of criticality accidents or malevolent acts with nuclear materials.

Determination of cosmogenic 32P and 33P in environmental samples

Understanding phosphorus dynamics inmarine environment is of great importance, and appropriate tracers for phosphorus cycling in oceans are invaluable. In this study, two methods were developed for extraction, purification, and determination of naturally occurring 32P and 33P in rainwater, marine plankton and sediments using both a low-level beta counter (LBC) and an ultra-low-level liquid scintillation spectrometer (LSS). Blanks, chemical yields and counting efficiencies were quantified for bothmethods. The chemical purification of 32P and 33P separated by both procedures was validated by their decay curves. The absorber thickness of aluminum for LBC was assessed as 39.2 mg/cm2. 32P and 33P specific activities in some rain samples were determined by both methods and showed good consistent results. The advantage of the LSS over the LBC is apparent in its high counting efficiency and in determining samples with high concentration of stable phosphorus. However, when measuring environmental samples with low concentration of stable phosphorus, such as rainwater, both methods can be used and each has its distinct advantage.

The effect of benthic algae on phosphorus exchange between sediment and overlying water in shallow lakes: a microcosm study using 32P as a tracer

Sediments are of key importance in determining the nutrient levels of water in shallow lakes as they can act as either source or sink for phosphorus (P) depending on environmental conditions, sediment characteristics, and external nutrient loading. We examined the role of benthic algae in the P cycling between sediment and overlying water in experiments using 32P as a tracer. Sediment and water samples were collected from Huizhou West Lake, a shallow, eutrophic waterbody located in Huizhou City, South China. Laboratory cultured benthic algae were transferred to cover the sediment core in tubes. When 32P was added to the water in experimental tubes containing sediment cores with and without benthic algae, 32P activity after 48 h was significantly lower in the tubes with algae, indicating that benthic algae removed P from the overlying water. When the tracer was injected into the sediment, 32P activity in the water overlying sediment with benthic algae was substantially lower than in tubes with naked sediment, suggesting that benthic algae reduce the release of sediment P. Oxygen levels were significantly higher in the upper 3 mm of the sediments covered by benthic algae; thus, we hypothesized that oxygen produced by the algae helps inhibit the release of P from the sediment. Our study demonstrates that benthic algae are capable of reducing P levels in water overlying the sediment, suggesting that loss of benthic algae during eutrophication triggered by impoverished light conditions may accelerate the shift in shallow lakes from a clear water to a turbid state.

Nafion–Zirconium Phosphate Composite Membrane: A New Approach to Prepare 32P Patches for Superficial Brachytherapy Applications

This article describes a method for the preparation of (32)P patch for the treatment of skin cancer. It is based on the surface modification of a Nafion film by treatment with ZrOCl(2) solution, impregnation of a predicted quantity of (32)P into the film, and its subsequent immobilization into a nonleachable matrix by lamination. The effect of variations of critical parameters on the incorporation of (32)P into the membrane, such as solution pH, contact time, reaction volume, inactive carrier concentration of the feed, reaction temperature, and so on, was investigated to arrive at the conditions resulting in optimum retention of (32)P activity. The morphology of the membrane was evaluated by scanning electron microscope and energy dispersive spectral analyses. Quality control tests were carried out to ensure nonleachability, uniform distribution of activity, and stability of the patches.

Novel method for quantifying radiation-induced single-strand-break yields in plasmid DNA highlights 10-fold discrepancy

The widely used agarose gel electrophoresis method for assessing radiation-induced single-strand-break (SSB) yield in plasmid DNA involves measurement of the fraction of relaxed-circular (C) form that migrates independently from the intact supercoiled (SC) form. We rationalized that this method may underestimate the SSB yield since the position of the relaxed-circular form is not altered when the number of SSB per DNA molecule is >1. To overcome this limitation, we have developed a novel method that directly probes and quantifies SSBs. Supercoiled 3H-pUC19 plasmid samples were irradiated with γ-rays, alkali-denatured, dephosphorylated, and kinated with γ-[ 32P]ATP, and the DNA-incorporated 32P activities were used to quantify the SSB yields per DNA molecule, employing a standard curve generated using DNA molecules containing a known number of SSBs. The same irradiated samples were analyzed by agarose gel and SSB yields were determined by conventional methods. Comparison of the data demonstrated that the mean SSB yield per plasmid DNA molecule of [21.2 ± 0.59] × 10 −2 Gy −1 as measured by direct probing is ∼10-fold higher than that obtained from conventional gel-based methods. These findings imply that the SSB yields inferred from agarose gels need reevaluation, especially when they were utilized in the determination of radiation risk.

Cherenkov radiation imaging of beta emitters: in vitro and in vivo results

The main purpose of this work was to investigate both in vitro and in vivo Cherenkov radiation (CR) emission coming from 18F and 32P. The main difference between 18F and 32P is mainly the number of the emitted light photons, more precisely the same activity of 32P emits more CR photons with respect to 18F. In vitro results obtained by comparing beta counter measurements with photons average radiance showed that Cherenkov luminescence imaging (CLI) allows quantitative tracer activity measurements. In order to investigate in vivo the CLI approach, we studied an experimental xenograft tumor model of mammary carcinoma (BB1 tumor cells). Cherenkov in vivo dynamic whole body images of tumor bearing mice were acquired and the tumor tissue time activity curves reflected the well-known physiological accumulation of 18F-FDG in malignant tissues with respect to normal tissues. The results presented here show that it is possible to use conventional optical imaging devices for in vitro or in vivo study of beta emitters.

Dosimetry of a New P-32 Ophthalmic Applicator

Purpose: A 90Sr/Y applicator has been used as a β-source for postoperative irradiation after pterygium excision. As an alternative to 90Sr/Y irradiation, we proposed treatments with 32P. This study aims to provide the dosimetry for this new applicator. Method and Materials: A 32P ophthalmic applicator, of which the design and materials were optimally designed by Monte Carlo simulations, was fabricated by the Korea Atomic Energy Research Institute. The absorbed dose at the front surface of the cylindrical 32P applicator was measured by using an extrapolation ionization chamber. Radiochromic film (RCF) was used to measure depth dose distributions and dose profiles at various depths. A micro-MOSFET detector was used for depth dose measurements. Results: The absorbed dose rates to the reference point (i.e., at the centre on the front surface of 32P applicator) were 0.238 ± 0.012 cGy/s for an extrapolation ionization chamber, 0.280 ± 0.001 cGy/s for RCF, and 0.257 ± 0.020 cGy/s for MOSFET. The axial depth dose rate was reduced into approximately 1/10 as 32P betas penetrate every 2 mm depth. Measured data in depths of 1 mm to 3.5 mm agreed with Monte Carlo data. Due to non-uniform absorption of 32P into an absorbent disk, the dose at the centre of trans-axial plane was 2%–4% less than the peak dose around the periphery. We confirmed no leakage of 32P activities and negligible exposure rate around the hand grip of the applicator. Conclusions: The 32P applicator can deliver uniform therapeutic doses to the surface of the conjunctiva, while sparing the lens better than 90Sr/Y applicators. The doses at any points from the 32P applicator can be calculated by using these measured data sets. The safety of 32P applicator was confirmed. However, prior to the clinical application of every new applicator, safety, dose uniformity, and absorbed dose rate at the reference point should be carefully evaluated by the method developed in this study.

Pediatric dosimetry for intrapleural lung injections of 32P chromic phosphate

Intracavitary injections of 32P chromic phosphate are used in the therapy of pleuropulmonary blastoma and pulmonary sarcomas in children. The lung dose, however, has never been calculated despite the potential risk of lung toxicity from treatment. In this work the dosimetry has been calculated in target tissue and lung for pediatric phantoms. Pleural cavities were modeled in the Monte Carlo code MCNP within the pediatric MIRD phantoms. Both the depth–dose curves in the pleural lining and into the lung as well as 3D dose distributions were calculated for either homogeneous or inhomogeneous 32P activity distributions. Dose–volume histograms for the lung tissue and isodose graphs were generated. The results for the 2D depth–dose curve to the pleural lining and tumor around the pleural cavity correspond well with the point kernel model-based recommendations. With a 2 mm thick pleural lining, one-third of the lung parenchyma volume gets a dose more than 30 Gy (V30) for 340 MBq 32P in a 10 year old. This is close to lung tolerance. Younger children will receive a larger dose to the lung when the lung density remains equal to the adult value; the V30 relative lung volume for a 5 year old is 35% at an activity of 256 MBq and for a 1 year old 165 MBq yields a V30 of 43%. At higher densities of the lung tissue V30 stays below 32%. All activities yield a therapeutic dose of at least 225 Gy in the pleural lining. With a more normal pleural lining thickness (0.5 mm instead of 2 mm) the injected activities will have to be reduced by a factor 5 to obtain tolerable lung doses in pediatric patients. Previous dosimetry recommendations for the adult apply well down to lung surface areas of 400 cm2. Monte Carlo dosimetry quantitates the three-dimensional dose distribution, providing a better insight into the maximum tolerable activity for this therapy.

Influence of Physical Raking and Biological Process in the Mud-water Exchange Dynamics of P in Fish Culture Ponds

Experiment was conducted in the laboratory using radioactive 32P for ascertaining the dynamics and quantifying the exchangeable amount of P between sediment and water phase under the influence of physicalraking and biological processes. Collected sediment (100 g) was dispensed in a glass beaker and treated with radioactive 32P after reaction with CaCO3. Each beaker filled with 250 ml tap water. Four different treatments: physical raking once (RO), repeated raking (RR), bacteria (Bacillus, 167 X 102 ml-1) inoculum (BI) and bacteriainoculum (Bacillus, 167 X 102 ml-1) plus repeated raking (BI + RR) were used in the study. Water samples were collected and tested for specific activity of radioactive 32P, concentration of orthophosphate and count of heterotrophic bacterial (HB) population. The 32P value of BI+RR treatment was 20, 25, 37 and 56% higher than BI,RR, RO and control, respectively. Therefore, it can be concluded that synergistic effect of bacteria inoculum plus repeated raking (BI + RR) released maximum amount of phosphorus than the rest three treatments. Critical appraisal of data clearly revealed four states of dynamic of 32P between sediment and overlaying water: initial rapid increase of 32P level in water - rapid desorption period (RDP) from day 0 to 12, slow increase of 32P level of water - slow desorption period (SDP) from day >12 to 55, the 32P moves to sediment resulting in decrease 32P level in water - absorption period (AP) from day >55 to 90 and steady period (SP) from day >90 to 124, when 32P concentration of water and sediment supposed to be equal indicating no movement of 32P occurred between the water and sedimentphase.

MO-EE-A1-02: Dosimetry for an Ophthalmic Applicator of P-32

Purpose: A 90Sr/Y applicator has been used as a ‐source for postoperative irradiation after pterygium excision. As an alternative to 90Sr/Y irradiation, we proposed treatments with 32P. This study aims to provide the dosimetry for this new applicator. Method and Materials: In order to optimize the design and materials of 32P ophthalmic applicators, Monte Carlo simulations were performed. The absorbed dose at the surface of a sealed beta source is often measured by using an extrapolation ionization chamber. Radiochromic film (RCF) was used to measure depth dose distributions and dose profiles at various depths. A micro‐MOSFET detector was used for depth dose measurements. Results: The absorbed dose rates to the reference point were 0.238 ± 0.012 cGy/s for an extrapolation ionization chamber, 0.280 ± 0.001 cGy/s for radiochromic films, and 0.257 ± 0.020 cGy/s for MOSFET. The axial depth dose rate was reduced into approximately 1/10 as 32P betas penetrate every 2 mm depth. Measured data sets in depths of 1 mm to 3.5 mm agreed with Monte Carlo data. Due to non‐uniform absorption of 32P into an absorbent disk, the dose at the center of transaxial plane were 2%–4% less than the peak dose around the periphery. We confirmed no leakage of 32P activities and negligible exposure rate around the hand grip of the applicator. Conclusions: The 32P applicator can deliver uniform therapeutic doses to the surface of the conjunctiva, while sparing the lens better than 90Sr/Y applicators. The doses at any points from the 32P applicator can be calculated by using these measured data sets. The safety of 32P applicator was confirmed. However, prior to the clinical application of every new applicator, safety, dose uniformity, and absorbed dose rate at the reference point should be carefully evaluated by the method developed in this study.

Monte Carlo and analytical calculations of dose distributions in craniopharyngioma cysts treated with radiocolloids containing 32P or 186Re

In radiation treatments of some types of brain tumors, such as craniopharyngiomas, selection of an appropriate radionuclide is critical. The aim of this work was to calculate distributions of dose rates from 32P and 186Re in radiocolloids injected into craniopharyngioma cysts. The calculations were performed with the MCNP4C radiation transport code. Analytical calculations based on the Loevinger formula were also performed for 32P with the MATLAB software. The results of the two techniques for identical models were compared. The effects of the cyst wall type and of the density of the cyst inner fluid were investigated. The 32P activities required for providing 200, 250, and 300Gy to cysts of different sizes were calculated.

Application of neutron transmutation doping method to initially p-type silicon material

The neutron transmutation doping (NTD) method was applied to the initially p-type silicon in order to extend the NTD applications at HANARO. The relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material was investigated. The proportional constant between the neutron fluence and the resistivity was determined to be 2.3473×10 19 n Ω cm −1. The deviation of the final resistivity from the target for almost all the irradiation results of the initially p-type silicon ingots was at a range from −5% to 2%. In addition, the burn-up effect of the boron impurities, the residual 32P activity and the effect of the compensation characteristics for the initially p-type silicon were studied. Conclusively, the practical methodology to perform the neutron transmutation doping of the initially p-type silicon ingot was established.