Biosorption of 241Am by immobilized Saccharomyces cerevisiae

More than half of the world's annual production of radionuclides is used for medical purposes such as diagnostic imaging of diseases and patient therapy. Using aqueous homogeneous solution reactor technology, production quantities of medical radioisotopes ⁹⁹Mo and⁸⁹Sr, can be extracted from one reactor cycle. ⁹⁹Mo may be produced directly from UO₂SO₄ uranyl sulfate in an aqueous homogeneous solution nuclear reactor in a manner that produces high purity radionuclides, making efficient use of the reactor's uranium fuel solution. The process is relatively simple, economical, and waste free, eliminating uranium targets. The short-lived radioisotope ^99mTc is eluted from ⁹⁹Mo for diagnostic imaging. Radioisotope ⁸⁹Sr infusion is a therapeutic modality that reduces reliance on narcotic analgesia through palliation of metastatic bone pain caused by metastases of the cancer to the bone. Painful disseminated osseous metastases are common with carcinomas of the lung, prostate, and breast. Synergistic interleaving of two manufacturing processes, one producing ⁹⁹Mo and another producing ⁸⁹Sr in the same production cycle of an aqueous homogeneous solution reactor makes full and efficient use of the time for both the neutron irradiation stage and the extraction stage of each radionuclide. Interleaving the capture of ⁸⁹Sr radioisotope with production processing of ⁹⁹Mo radioisotope is achieved, since the extraction and subsequent elimination of radionuclide impurities occurs during separate parts of the reactor cycle. The process applies to either HEU or LEU nuclear fuels in an aqueous homogeneous solution reactor.     

Assessment of gamma-ray emissions from natural and manmade decorative stones

Decorative stones (32 natural and 18 manufactured) and five ceramic tiles that are used in home interiors were measured with gamma-ray spectrometry, to identify and quantify the naturally occurring radionuclides. Activity concentrations of the radioisotopes varied by more than two orders of magnitude across the stone samples, with maximal levels of 3380, 850, and 2130 Bq/kg, for ²³⁸U, ²³²Th, and ⁴⁰K, respectively. A radiation index and measurements with a radiation meter established that the annual effective dose rates due to a 1 h/day exposure to gamma rays emitted by the granite samples were often low, but can occur as high as 1 mSv/year.     

Dynamic range optimization in SIMS analyses of arsenic and antimony dopants in silicon

Summary The application of two sample preparation techniques leads to a better understanding of the profile tailing in SIMS analyses of As and Sb distributions measured with Cs primary ions. The dynamic range in the SIMS depth profiles in terms of the detected concentration range is improved nearly by three orders of magnitude on samples with extremely high surface concentrations compared to measurements without preparation. More than five orders of magnitude are obtained. The application of the preparation techniques to As ion implants in silicon reveals a channeling tail below a concentration level of 5·10¹⁶ at/cm³ which is nearly independent of the implanted ion dose if it exceeds 5·10¹² at/cm².     

Synthesis and biodistribution of two novel 99mTc nitrido dithiocarbamate complexes containing heterocyclic linkage as potential brain perfusion imaging agents

Various plutonium compounds are handled in nuclear facilities of BARC. Hence, there is a possibility of occupational workers getting exposed to Pu. In vitro bioassay monitoring in which Pu is separated by chemical procedures from excreta samples and estimated by alpha-spectrometry, is the method of choice for the evaluation of internal dose to the occupational workers handling Pu. However, this method requires a suitable Pu tracer for reducing the uncertainties due to chemical yield in the separation, electro-deposition and counting efficiency. ²⁴²Pu is commonly used as a tracer but due to its non-availability, efforts were made earlier to indigenously synthesis ²³⁶Pu by proton irradiation of ²³⁷Np in BARC-TIFR pelletron facility. The present study, reports the feasibility of using ²³⁶Pu as a radiochemical yield monitor (tracer) in bioassay samples.     

Feasibility studies to assess the use of <Superscript>236</Superscript>Pu as a radiochemical yield monitor in bioassay samples

Various plutonium compounds are handled in nuclear facilities of BARC. Hence, there is a possibility of occupational workers getting exposed to Pu. In vitro bioassay monitoring in which Pu is separated by chemical procedures from excreta samples and estimated by alpha-spectrometry, is the method of choice for the evaluation of internal dose to the occupational workers handling Pu. However, this method requires a suitable Pu tracer for reducing the uncertainties due to chemical yield in the separation, electro-deposition and counting efficiency. ²⁴²Pu is commonly used as a tracer but due to its non-availability, efforts were made earlier to indigenously synthesis ²³⁶Pu by proton irradiation of ²³⁷Np in BARC-TIFR pelletron facility. The present study, reports the feasibility of using ²³⁶Pu as a radiochemical yield monitor (tracer) in bioassay samples.     

Neutron spectral measurement of the Ohio state research reactor pneumatic tube

Pneumatic irradiation facilities are used for neutron activation analysis, materials testing, electronics hardening, and radioisotope production. The application of these facilities can benefit from a greater understanding of the neutron energy profile inside the irradiation cavities as often only the cadmium ratio is known. A program to measure the energy-dependent neutron fields inside the pneumatic tube at the Ohio State University Research Reactor was undertaken using wires consisting of thermal activation materials and threshold reaction materials with and without thermal and resonance absorbers surrounding them. The measured activities were unfolded using the MAXED unfolding code to reconstruct the neutron energy spectra and compared to the MCNP-calculated flux.     

Comparison of two ultra-sensitive methods for the determination of 232Thby recovery corrected pre-concentration radiochemicalneutron activation analysis

The determination of isotopic thorium by alpha spectrometric methods is a routine practice for bioassay and environmental measurement programs. Alpha-spectrometry has excellent detection limits (by mass) for all isotopes of thorium except ²³²Th due to its extremely long half-life. This paper discusses improvements in the detection limit and sensitivity over previously reported methods of pre-concentration neutron activation analysis (PCNAA) for the recovery corrected, isotopic determination of thorium in various matrices. Following irradiation, the samples weredissolved, ²³¹Pa added as a tracer, and Pa isolated by two different methods and compared (extraction chromatography and anion exchange chromatography) followed by alpha spectrometry for recovery correction. Ion exchange chromatography was found to be superior for this application at this time, principally for reliability. The detection limit for ²³²Th of 3.5 · 10^-7 Bq is almost three orders of magnitude lower than foralpha spectrometry using the PCRNAA method and one order of magnitude below previously reported PCNAA methods.     

Dose assessment from exposure to radon,thoron and their progeny concentrations in the dwellings of sub-mountainous region of Jammu &amp; Kashmir,India

The present work deals with the assessment of annual inhalation dose due to exposure of indoor radon, thoron and their progeny concentrations in the villages situated in sub-mountainous region of Jammu & Kashmir, India. The distribution of the data and the homogeneity of medians among different seasons and dwellings were assessed with the Shapiro–Wilk test and the Mann–Whitney test. The estimated total annual inhalation dose in these villages varied from 0.5 to 1.9 mSv year^?1 which is less than the prescribed limit by ICRP (2008). Thus, the investigated area is safe from irradiation of radon, thoron and their progeny.     

Investigation of radon and thoron concentrations in a landmark skyscraper in Tokyo

The temporal variation of the radon concentration, and the radon and thoron concentrations every 3 months for a year were measured using two types of devices in a landmark skyscraper, the Tokyo Metropolitan Government Daiichi Building. In the measurement of temporal variation of the radon concentration using a pulse type ionization chamber, the average radon concentration was 21 ± 13 Bq m^?3 (2–68 Bq m^?3). The measured indoor radon concentration had a strong relationship with the operation of the mechanical ventilation system and the activities of the office workers. The radon concentration also increased together with temperature. Other environmental parameters, such as air pressure and relative humidity, were not related to the radon concentration. In the long-term measurements using a passive radon and thoron discriminative monitor, no seasonal variation was observed. The annual average concentrations of radon and thoron were 16 ± 8 and 16 ± 7 Bq m^?3, respectively. There was also no relationship between the two concentrations. The annual average effective dose for office workers in this skyscraper was estimated to be 0.08 mSv y^?1 for 2000 working hours per year. When considering the indoor radon exposure received from their residential dwellings using the annual mean radon concentration indoors in Japan (15.5 Bq m^?3), the annual average effective dose was estimated to be 0.37 mSv y^?1. This value was 31 % of the worldwide average annual effective dose.     

Activation rates and chemical recovery of67Cu produced with low energy proton irradiation of enriched70Zn targets

Copper-67 is a radioisotope with significant potential for diagnostic and therapeutic applications in nuclear medicine. Despite its promise,⁶⁷Cu has failed to make an impact in clinical nuclear medicine, primarily because it is available sporadically, and in limited quantities. Common methods of production rely on high energy proton irradiation of natural zinc targets or on induced reactions using high energy neutrons at nuclear reactors. We have evaluated alternative production methods that could provide year-round adequate supply of this isotope. Using a low energy accelerator, we have studied the production of⁶⁷Cu by proton reactions on enriched⁷⁰Zn. Our results indicate that it is possible to produce useful quantities of⁶⁷Cu from the irradiation of enriched⁷⁰Zn with protons that have energies of less than 20 MeV. Production rates are higher than currently used methods at high energy accelerators or reactors. This isotope can be made available throughout the year as a result of this research.     

Production of the radioisotope88Y

Carrier-free⁸⁸Y radioisotope, which has the longest half life /T=106.6 d/ of yttrium radioisotopes and is a -ray emitter, was obtained by proton irradiation of strontium, followed by cooling for one month. Then,⁸⁸Y was purified by precipitating strontium as strontium nitrate and extracting yttrium with tri-n-butyl phosphate /TBP/. The decontamination factor of strontium to yttrium was more than 4×10³ and chemically pure yttrium radioisotope was obtained.     

Neutron spectrum parameters in irradiation channels of the Nigeria Research Reactor-1 (NIRR-1) for the <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-NAA standardization

Summary The first nuclear research reactor in Nigeria has been commissioned for neutron activation analysis and limited radioisotope production. In order to extend its utilization to include the k₀-standardization method, the following neutron spectrum parameters in inner and outer irradiation channels were determined by the “Cd-ratio for multi-monitor method”: the thermal-to-epithermal flux ratio, f, and the epithermal flux shape factor, α. Neutron spectrum parameters determined in the inner irradiation channel B2, are: α = -0.052±0.002 and f = 19.2±0.5. For the outer irradiation channel B4, the neutron spectrum parameters were found to be α = +0.029±0.003 and f = 48.3±3.3. The results are compared with the neutron spectrum parameters of other reactor facilities with similar core configuration such as the Slowpoke and Miniature Neutron Source Reactor facilities available in the literature.     

Vacuum-UV and Low-Energy Electron-Induced DNA Strand Breaks – Influence of the DNA Sequence and Substrate

DNA is effectively damaged by radiation, which can on the one hand lead to cancer and is on the other hand directly exploited in the treatment of tumor tissue. DNA strand breaks are already induced by photons having an energy below the ionization energy of DNA. At high photon energies, most of the DNA strand breaks are induced by low-energy secondary electrons. In the present study we quantified photon and electron induced DNA strand breaks in four different 12mer oligonucleotides. They are irradiated directly with 8.44 eV vacuum ultraviolet (VUV) photons and 8.8 eV low energy electrons (LEE). By using Si instead of VUV transparent CaF₂ as a substrate the VUV exposure leads to an additional release of LEEs, which have a maximum energy of 3.6 eV and can significantly enhance strand break cross sections. Atomic force microscopy is used to visualize strand breaks on DNA origami platforms and to determine absolute values for the strand break cross sections. Upon irradiation with 8.44 eV photons all the investigated sequences show very similar strand break cross sections in the range of 1.7–2.3×10⁻¹⁶ cm². The strand break cross sections for LEE irradiation at 8.8 eV are one to two orders of magnitude larger than the ones for VUV photons, and a slight sequence dependence is observed. The sequence dependence is even more pronounced for LEEs with energies <3.6 eV. The present results help to assess DNA damage by photons and electrons close to the ionization threshold.     

Assessment of radon concentration and external gamma radiation level in the environs of Narwapahar uranium mine,India and its radiological significance

In the environs of uranium mining, milling and processing facilities and in the uranium mineralized terrain, a little higher ambient radon concentration and gamma radiation level may be expected in comparison with natural background. The present study gives a brief account of atmospheric radon concentration, gamma absorbed dose rate and radiation dose received by the members of public in the vicinity of Narwapahar uranium mine. The ambient radon concentration in the air in the study area was found to vary from 5 to 107 Bq m⁻³ with geometric mean of 24 Bq m⁻³ and geometric standard deviation of 1.74 Bq m⁻³. The measured gamma absorbed dose rate in air at 1 m above the ground ranged from 87 to 220 nGy h⁻¹ with an overall arithmetic mean of 128 ± 18.5 nGy h⁻¹. The mean annual effective dose received by the members of public from inhalation of radon and its progeny and external gamma exposure was estimated to be 0.32 mSv year⁻¹, which is comparable to other reported values elsewhere.     

Estimation of indoor radon and the annual effective dose from building materials by ionization chamber measurement

Indoor radon and its annual effective dose from the building materials commonly used in Thailand were reported. Radon emission from samples collected in the closed chamber was measured by an ionization chamber. Indoor radon and the annual effective dose were calculated from radon concentration in the closed chamber. Granite yields the highest annual effective dose. Three samples of granite shown the annual effective dose higher than the annual exposure limit for the general public of 1 mSv year^?1 recommended by the International Commission on Radiological Protection. Applying appropriate surface coating, the radon emission from some building materials has decreased substantially.     

Effects of gamma irradiation on optical and structural properties of PbO–Bi2O3–B2O3 glasses

Optical and structural properties of xPbO·2xBi₂O₃(1−3x)B₂O₃ glasses of different composition have been studied using UV-VIS and FTIR spectroscopic techniques. Effects of gamma radiations on glass network and structural units have been studied by irradiating glass samples with a ⁶⁰Co radioisotope to the overall dose of 2.5 kGy. It is shown that irradiation causes compaction of the borate network by breaking the bonds between trigonal elements, which leads to a decrease in the optical band gap energy. Changes in the atomic structure before and after the irradiation are observed and explained.     

Assessment of intake of a complex radionuclide bearing dust formed at a nuclear power plant

The aim of this work was to provide an experimental basis for assessing intakes of an industrial actinide-bearing dust from measurements of⁶⁰Co and¹³⁷Cs in the body or urine. Whilst these radionuclides comprised 72% and 19% of the radioactivity present, greater than 90% of the committed effective dose will result from the low concentrations of the actinides present, 0.4%. To assess the dose coefficient for the dust and predict the biokinetics of⁶⁰Co and¹³⁷Cs in workers, absorption parameters for transfer from lungs to blood obtained from an animal study were combined with information on particle deposition and clearance from the ICRP human respiratory tract model and with tissue distribution and excretion data from the most recent systemic models. All other radionuclides were assumed to have Type M absorption characteristics. The dose coefficient for the dust, 1.29·10^–7 Sv·Bq^–1 was estimated to contain 113 kBq⁶⁰Co, 29 kBq¹³⁷Cs and 0.64 kBq of the actinides. The predicted retention and excretion characteristics of⁶⁰Co and¹³⁷Cs in workers after acute or chronic exposure to the dust suggested that measurements of these radionuclides in the body or urine could detect intakes equivalent to a few percent of an annual dose limit of 20 mSv·y^–1.     

Surface characterization and depth profiling of biological molecules by electrospray droplet impact/SIMS

Electrospray droplet impact (EDI) was applied to the analysis of peptides. The etching rate of bradykinin was estimated to be ~2 nm/min. This value is about one order of magnitude greater than the etching rate for SiO₂ (0.2 nm/min). Considering that the etching rate of argon cluster ions Ar₇₀₀⁺ for organic compounds is more than two orders of magnitude larger than that for inorganic materials, the rather small difference in etching rates of EDI for organic and inorganic materials is unique. When water/ethanol (1/1, vol%) solution of gramicidin S and arginine was dried in air, [gramicidin S + H]⁺ was observed as a predominant signal with little [Arg + H]⁺ right after the EDI irradiation, indicating that EDI is capable of detecting the analytes enriched on the sample surface. Copyright © 2011 John Wiley & Sons, Ltd.     

Measurement of activation cross sections of the proton induced nuclear reactions on palladium

Excitation functions of proton induced reactions on Pd are important for medical radioisotope production, for activation analysis, for development of low activation materials and other purposes. No experimental data exist in the literature for low and medium energy range protons. A detailed study of the excitation functions was performed up to 80 MeV proton energy by using the stacked foil irradiation technique and gamma-ray spectrometry. The irradiations were carried out at the external beam lines of the AVF cyclotron at the Tohoku University. Japan (80 and 70 MeV) and the CGR 560 cyclotron at the Vrije Universiteit Brussels (38, 29 and 17 MeV). The beam intensity, the incident energy and the energy degradation were controlled by a method based on flux constancy via normalization to the parallel measured excitation functions of ^natAl(p,x)^22,24Na and ^natCu(p,x)^56,58Co, ^62,65Zn monitor reactions. Excitation functions for direct and cumulative cross sections have been measured for the production of ^{105mg,106m,110m}Ag, ¹⁰¹Pd, ^101mRh and ⁹⁷Ru radionuclei. Calculations for the excitation functions using the Alice-IPPE code were performed with a view to estimate the weight of the different contributing reactions and to check the trend and the magnitude of the obtained experimental data.     

An automated irradiation device for use in cyclotrons

Two cyclotrons are being operated at IPEN-CNEN/SP: one model CV-28, capable of accelerating protons with energies up to 24 MeV and beam currents up to 30 mA, and three other particles; the other one, model Cyclone 30, accelerates protons with energy of 30 MeV and currents up to 350 mA. Both have the objective of irradiating targets both for radioisotope production for use in nuclear medicine and general research. The development of irradiating systems completely automatized was the objective of this work, always aiming to reduce the radiation exposition dose to the workers and to increase the reliability of use of these systems.