Alpha-particle Activity Research Articles

Gross Alpha-Particle Activity and High 226Ra Concentrations Do Not Correspond with High 210Po in the Atlantic and Gulf Coastal Plain Aquifers of the United States

210Po, which is of human-health concern based on lifetime ingestion cancer risk, is indirectly regulated in drinking water through the U.S. Environmental Protection Agency’s gross alpha-particle activity (GAPA) maximum contaminant level of 15 pCi/L (picocuries per liter). This regulation requires independent measurement of 226Ra for samples exceeding the GAPA screening level of 5 pCi/L. There is no such requirement for 210Po. Co-occurrence of 226Ra and 210Po, alpha-emitting 238U-decay-series progeny, might be helpful in locating high-210Po waters but is unverified. Relations among 210Po, 226Ra, and GAPA evaluated for samples from 257 public-supply wells from Coastal Plain aquifers showed that concentrations of 226Ra correlated with GAPA but neither correlated with 210Po concentrations. The highest concentrations of 226Ra and 210Po were found under differing geochemical conditions. The highest 226Ra occurred in low-pH oxidizing waters and in neutral-pH reducing waters, where geochemical conditions render Fe–Mn-hydroxide sorbents inefficient. 210Po was highest (10.1 pCi/L) in reducing waters with high pH (>7.5, which results from progressive cation exchange), where 226Ra was lowest─exchanged to clay minerals. Because 226Ra and 210Po did not co-occur, the GAPA screening might not be protective for 210Po. Independent 210Po analysis is prudent, especially where groundwater is reducing with high pH and low 226Ra concentrations.

Site-specific concentration of uranium in urine of workers of the hydrometallurgical plant of Stepnogorsk mining and chemical combine.

Radiation monitoring is an important radiation safety measure implemented at the hydrometallurgical plant of the Stepnogorsk mining and chemical combine (HMP SMCC, Republic of Kazakhstan). Follow-up of the workers and their regular medical examinations has laid the basis to create a cohort with the potential to be used in radiation epidemiology. The aim of current pilot study was to analyze the dose forming factors for workers of HMP SMCC. For this, bioassays samples collected from 54 workers employed at eight HMP workshops were measured using the "Agilent 7800 ICP-MS" mass spectrometer. Three years later, measurements were repeated for four workers with the highest concentrations of uranium in urine. The results of site-specific measurements of dose rates, long-lived alpha-particle activity concentrations and equivalent equilibrium volume activity of radon were derived from the archive of the HMP SMCC Service of Radiation and Toxic Safety and analyzed to fully evaluate the radiation situation at those workplaces. Maximum urine uranium concentrations were measured for workers at the extraction workshop and mechanical repair shop (up to 26.7µg/L and 14.6µg/L, respectively). Urinary uranium from workers employed at other sites was mainly (for about 72% of the samples) in the range of values that may occur in natural conditions (< 0.4µg/L). A wide individual variability in uranium concentration in urine samples (from 60% to 200% of CV) was found. A linear dependence of cumulative effective dose on work experience was found with a slope of 7.5mSv per year. This slope did not depend on working place. For the investigated workers, cumulative effective doses of workers were found in the range of low (< 100mSv) and medium doses (100-500mSv). It is concluded that the newly created cohort of HMP SMCC workers has the potential to improve the knowledge on health effects from low- and medium doses of ionizing radiation.

Charged particle activation facility in NPI CAS and in future GANIL/SPIRAL2-NFS

The proton, deuteron and alpha induced reactions are of a great interest for the assessment of induced radioactivity of accelerator components, targets and beam stoppers as well as isotope production for medicine and also to nuclear astrophysics. We present a new irradiation chamber for activation measurements, that forms a prolongation of long-term experimental activities using stacked-foil activation technique in NPI CAS, Řež. The chamber is based on an airlock system and is coupled to a pneumatic transfer system delivered by KIT Karlsruhe. This system is installed in GANIL/SPIRAL2-NFS and will be used for proton, deuteron and alpha particle activation measurements with long- and short-lived isotopes.

A Monte Carlo Method for Determining the Response Relationship between Two Commonly Used Detectors to Indirectly Measure Alpha Particle Radiation Activity.

Using targeted ligands to deliver alpha-emitting radionuclides directly to tumor cells has become a promising therapeutic strategy. To calculate the radiation dose to patients, activities of parent and daughter radionuclides must be measured. Scintillation detectors can be used to quantify these activities; however, activities found in pre-clinical and clinical studies can exceed their optimal performance range. Therefore, a method of correcting scintillation detector measurements at higher activities was developed using Monte Carlo modeling. Because there are currently no National Institute of Standards and Technology traceable Actinium-225 (225Ac) standards available, a well-type ionization chamber was used to measure 70.3 ± 7.0, 144.3 ± 14.4, 222.0 ± 22.2, 299.7 ± 30.0, 370.0 ± 37.0, and 447.7 ± 44.7 kBq samples of 225Ac obtained from Oak Ridge National Lab. Samples were then placed in a well-type NaI(Tl) scintillation detector and spectra were obtained. Alpha particle activity for each species was calculated using gamma abundance per alpha decay. MCNP6 Monte Carlo software was used to simulate the 4π-geometry of the NaI(Tl) detector. Using the ionization chamber reading as activity input to the Monte Carlo model, spectra were obtained and compared to NaI(Tl) spectra. Successive simulations of different activities were run until a spectrum minimizing the mean percent difference between the two was identified. This was repeated for each sample activity. Ionization chamber calibration measurements showed increase in error from 3% to 10% as activities decreased, resulting from decreasing detection efficiency. Measurements of 225Ac using both detector types agreed within 7% of Oak Ridge stated activities. Simulated Monte Carlo spectra of 225Ac were successfully generated. Activities obtained from these spectra differed with ionization chamber readings up to 156% at 147.7 kBq. Simulated spectra were then adjusted to correct NaI(Tl) measurements to be within 1%. These were compared to ionization chamber readings and a response relationship was determined between the two instruments. Measurements of 225Ac and daughter activity were conducted using a NaI(Tl) scintillation detector calibrated for energy and efficiency and an ionization chamber calibrated for efficiency using a surrogate calibration reference. Corrections provided by Monte Carlo modeling improve the accuracy of activity quantification for alpha-particle emitting radiopharmaceuticals in pre-clinical and clinical studies.

Laudation for Professor Susanta Lahiri Hevesy Medal Awardee 2015

Susanta Lahiri was born in Darjeeling, India, in 1961. He received his PhD (1994) from the University of Calcutta. In the same year he started his career as a lecturer (Assistant Professor) in Chemistry at the University of Burdwan, India. He moved to the Saha Institute of Nuclear Physics in 1997 where he became a Professor in 2003 and a Senior Professor in 2013. He is also a Professor at Homi Bhabha National Institute, Bhabha Atomic Research Centre in Mumbai, India. Professor Lahiri’s work is associated with many ‘‘firsts’’. In his early career, he started cyclotron production of no-carrier-added (NCA) radionuclides by alpha particle activation. Prof. Lahiri was the first scientist to irradiate lanthanide targets by heavier projectiles like Li, B, C, O etc. which made access to neutron deficient short-lived radioisotopes easier and expanded the horizon of clinically important radionuclides. He introduced the ‘‘tracer packet’’ idea, which allows one to deal with many similar radioactive tracers at-a-time in one experiment rather than setting up many experiments with individual tracers. His group is developing a number of green chemistry radioanalytical methods based on aqueous biphasic systems and room temperature ionic liquids. His group reported the first green chemistry synthesis of radioactive gold nanoparticles by adding HAuCl4 to polyethylene glycol. Professor Lahiri and his colleagues also joined the TASCA group in GSI, Germany. Recently they independently confirmed E-117. Neutrino mass measurement is a burning problem of fundamental science. Professor Lahiri’s team, for the first time, proposed indirect production route of Ho via Dy/Er and Tb/Er reactions to increase the yield of Ho by orders of magnitude to help neutrino studies. He carried out most of his basic Nuclear Chemistry work using medium energy accelerators in Mumbai and Kolkata and complemented it by collaborating with international institutions such as CERN, GSI, Heidelberg University, Institute of Modern Physics in China, TU Munich, ATOMKI Hungary, TU Delft, ETH Switzerland, and others. His team for the first time unveiled the total radionuclide inventory produced by bombardment of 1.4 GeV proton on thick lead–bismuth target. In a nutshell, Prof. Lahiri’s wide research interest is reflected in about 190 publications in international journals, and 250 reports in international and national conferences. He made contributions in ten books. He has received several national and international awards. He is a member of distinguished reviewers’ board of JRNC since 2005. He has supervised 11 PhD and 26 MSc theses so far. In recognition of his contribution in Nuclear Chemistry, The University of Calcutta conferred the highest academic honor, namely DSc degree, upon him in 2009. The title of his DSc dissertation was ‘‘Production and separation of carrier free radionuclides’’. Recently Indian Chemical Society bestowed him ‘‘Acharya J. C Ghosh Memorial Award’’ for the year 2014. It is indeed a pleasure to honor Prof. Susanta Lahiri with the Hevesy Medal Award 2015 for his outstanding contributions on heavy ion induced radioisotope production, tracer packet technique, converter targets, and green chemistry. The Hevesy Medal Award Selection Panel 2015 (HMASP-15) consisted of Professor Amares Chatt (Dalhousie University, Canada; also Chair of JRNC Board of & A. Chatt chatt@dal.ca

Study of Gross Alpha and Gross Beta Activity in Bottled Water in Dhaka City of Bangladesh

Gross alpha and gross beta particle activity was selected for the screening of radioactive species. The purpose of this study is to determine gross alpha and gross beta activities in bottled water samples. Sixteen different branded bottled water samples were collected from different markets in Dhaka city and analyzed by dual phosphor Zinc Sulphide Scintillation Detector, ZnS(Ag) for the measurement of gross alpha and gross beta activity. The observed gross alpha activity concentration ranged from 0.73 ± 0.02 mBqL -1 to 0.96 ± 0.07 mBqL -1 with an average 0.83 ± 0.057 mBqL -1 while gross beta activity concentration ranged from 65.54 ± 0.98 mBqL -1 to 77.29 ± 2.04 mBqL -1 with an average 71.47 ± 3.44 mBqL -1 . The obtained results showed that the average activity concentrations of alpha and beta emitting radionuclides in the bottled water samples did not exceed WHO recommended limits and The Environmental Conversation Rule of Bangladesh, 1997. The results of gross alpha and gross beta activities in bottled water were compared with the corresponding global values. To ensure the safe level of radioactivity in drinking water, however, periodic monitoring of water quality for compliance is necessary. This study will help to prepare baseline data for gross alpha and gross beta radioactivity in bottled water that can be used to evaluate the possible changes and the radiological impact on the public health in future.

A PLS-Based Weighted Artificial Neural Network Approach for Alpha Radioactivity Prediction inside Contaminated Pipes

Long-range alpha detection (LRAD) has been used to measure alpha particles emitting contamination inside decommissioned steel pipes. There exists a complex nonlinear relationship between input parameters and measuring results. The input parameters, for example, pipe diameter, pipe length, distance to radioactive source, radioactive source strength, wind speed, and flux, exhibit different contributions to the measuring results. To reflect these characteristics and estimate alpha radioactivity as exactly as possible, a hybrid partial least square back propagation (PLSBP) neural network approach is presented in this paper. In this model, each node in the input layer is weighted, which indicates that different input nodes have different contributions on the system and this finding has been little reported. The weights are determined by the PLS. After this modification, a variety of normal three-layered BP networks are developed. The comparison of computational results of the proposed approach with traditional BP model and experiments confirms its clear advantage for dealing with this complex nonlinear estimation. Thus, an integrated picture of alpha particle activity inside contaminated pipes can be obtained.

Optimization Method to Determine Gross Alpha-Beta in Water Samples Using Liquid Scintillation Counter

Liquid scintillation counting (LSC) is an adequate nuclear technique to determine radioactivity levels, as verified by this study for the determination of the gross alpha and beta activities of aqueous samples because of its simplicity and low associated cost comparison with other techniques. This paper discusses a new approach to the monitoring of gross alpha and gross beta activities in water. The method consists of using pulse decay discrimination (PDD) liquid scintillation counting LSC of 2 ml of the sample after conditioning with 12 ml of AB-Ultima Gold LSC cocktail, and PDD 139 condition. Different factors that affected on the counting efficiency were studied such as quench reaction, volume of sample, and type of vial. The gross alpha and gross beta particle activity measurement using 40K and 243Am with different activities concentration for efficiency determination. The calculated detection limits were 0.07 Bq/l and 0.12 Bq/l for gross alpha and gross beta respectively for 500 min measurements of samples produced by concentration of one liter of water.

210Po in Nevada Groundwater and Its Relation to Gross Alpha Radioactivity

Polonium-210 ((210) Po) is a highly toxic alpha emitter that is rarely found in groundwater at activities exceeding 1 pCi/L. (210) Po activities in 63 domestic and public-supply wells in Lahontan Valley in Churchill County in northern Nevada, United States, ranged from 0.01 ± 0.005 to 178 ± 16 pCi/L with a median activity of 2.88 pCi/L. Wells with high (210) Po activities had low dissolved oxygen concentrations (less than 0.1 mg/L) and commonly had pH greater than 9. Lead-210 activities are low and aqueous (210) Po is unsupported by (210) Pb, indicating that the (210) Po is mobilized from aquifer sediments. The only significant contributors to alpha particle activity in Lahontan Valley groundwater are (234/238) U, (222) Rn, and (210) Po. Radon-222 activities were below 1000 pCi/L and were uncorrelated with (210) Po activity. The only applicable drinking water standard for (210) Po in the United States is the adjusted gross alpha radioactivity (GAR) standard of 15 pCi/L. (210) Po was not volatile in a Nevada well, but volatile (210) Po has been reported in a Florida well. Additional information on the volatility of (210) Po is needed because GAR is an inappropriate method to screen for volatile radionuclides. About 25% of the samples had (210) Po activities that exceed the level associated with a lifetime total cancer risk of 1× 10(-4) (1.1 pCi/L) without exceeding the GAR standard. In cases where the 72-h GAR exceeds the uranium activity by more than 5 to 10 pCi/L, an analysis to rule out the presence of (210) Po may be justified to protect human health even though the maximum contaminant level for adjusted GAR is not exceeded.

RAPID SCREENING AND ANALYSIS OF ALPHA- AND GAMMA-EMITTING RADIONUCLIDES IN LIQUIDS USING A SINGLE SAMPLE PREPARATION PROCEDURE

A multifaceted radiochemical testing procedure has been developed to analyze a large number of liquid samples and measure a wide range of radionuclides in a short period of time. This method involves a single, unique and fast sample preparation procedure and allows sequential/concurrent determination of analytes with accuracy and precision. The same prepared sample can be selectively analyzed by gross alpha counting, gamma-ray spectroscopy, and alpha spectroscopy. This method is especially attractive in radiological emergency events where analytical data will be needed urgently as a basis for protective action. Given the simplicity and rapidity of the method, it may be suitable for field portable laboratories, which could save time and the cost associated with the transit of samples to a fixed laboratory. A 100 mL aliquot of sample was spiked with ¹³³Ba and ⁵⁹Fe tracers and subjected to a chemical separation procedure using a combined BaSO4 and Fe(OH)3 co-precipitation scheme. Then, the gross alpha-particle activity of the prepared sample was measured with a low-background gas-proportional counter, followed by the analysis of its photon-emitters using a gamma-ray spectroscopy system with high-purity intrinsic Ge detectors. Gamma-ray determination of ¹³³Ba and ⁵⁹Fe tracers was used to assess the chemical recoveries of BaSO4 and Fe(OH)3 fractions, respectively. Selectivity of the radionuclides for co-precipitation with either BaSO4 or Fe(OH)3 components was also investigated. Alpha mass-efficiency curves were derived using ²³⁰Th and ²⁴¹Am standards as alpha-calibration sources. Various mixtures of radionuclides, including ⁵⁴Mn, ⁵⁷Co, ⁶⁰Co, ⁸⁵Sr, ⁸⁸Y, ¹⁰⁹Cd, ¹¹³Sn, ¹³⁷Cs, ¹³⁹Ce, ²⁰³Hg, ²⁰⁹Po, ²²⁶Ra, ²²⁸Ra, ²³⁰Th, ²⁴¹Am, and natural uranium were used in this study. Most were quantitatively assayed with high chemical recoveries. Alpha-isotope identification and assessment of the prepared sample was achieved by alpha spectroscopy using passivated implanted planar silicon (PIPS) detectors. It has been shown that fission products could potentially be captured and analyzed by this method.

A 238Pu irradiator for exposure of cultured cells with alpha-radiation: Construction, calibration and dosimetry

An alpha-particle irradiator that can facilitate investigations of alpha-radiation effects on human cells in radiation protection, carcinogenesis and radioimmunotherapy was constructed. The irradiator was based on a 1.3 GBq 238Pu source, housed in a stainless steel tube flushed with helium. Radiation provided by 238Pu consists mainly of alpha-particles with energy of 5.5 MeV. The alpha-particle fluence and energy spectra were measured with a silicon semiconductor detector. Monte Carlo simulations were used to estimate the mean number of alpha-particles and the mean absorbed alpha-particle dose to cells for various irradiation times and distances between cells and source. There was a linear dependence between exposure time and alpha-particle fluence for exposure times above 1 s. The alpha-particle activity concentration varied with a factor 2.7 over the source area, while the variation in energy peak position was <4%. At the cell nucleus position and with a distance of 45 mm between the source and the mylar dish surface, the α-fluence was 4.6×10 4 counts/(mm 2 s), the average incident α-particle energy was 2.5 MeV and the average linear energy transfer was 167 keV/μm. The average dose rate to the cells, with 5 μm diameter nucleus, was 1.2 Gy/s. The 238Pu α-particle irradiator is feasible for irradiation of cells and it can be used for studies of both direct effects and bystander effects of alpha-radiation.

Gross alpha and gross beta particle activity in recycled water for augmentation of drinking water supplies

Research Article| May 01 2009 Gross alpha and gross beta particle activity in recycled water for augmentation of drinking water supplies Clemencia Rodriguez; Clemencia Rodriguez 1School of Population Health, Faculty of Medicine, Dentistry and Health Sciences, University of Western Australia, 35 Stirling Hwy, (M431), Crawley, 6009, WA, Australia Tel.: +61 (08) 6488 Fax: +61(08) 6488 1188; E-mail: clemencia.rodriguez@uwa.edu.au Search for other works by this author on: This Site PubMed Google Scholar Brian Devine; Brian Devine 1School of Population Health, Faculty of Medicine, Dentistry and Health Sciences, University of Western Australia, 35 Stirling Hwy, (M431), Crawley, 6009, WA, Australia Search for other works by this author on: This Site PubMed Google Scholar Angus Cook; Angus Cook 1School of Population Health, Faculty of Medicine, Dentistry and Health Sciences, University of Western Australia, 35 Stirling Hwy, (M431), Crawley, 6009, WA, Australia Search for other works by this author on: This Site PubMed Google Scholar Philip Weinstein; Philip Weinstein 2School of Population Health, Faculty of Health Sciences, University of Queensland, Herston Road, Herston, 4006, Qld, Australia Search for other works by this author on: This Site PubMed Google Scholar Paul Van Buynder Paul Van Buynder 3Department of Health, Government of Western Australia, Grace Vaughan House, 227 Stubbs Terrace, Shenton Park, 6008, WA, Australia Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2009) 58 (3): 191–202. https://doi.org/10.2166/aqua.2009.058 Article history Received: July 29 2008 Accepted: October 21 2008 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Clemencia Rodriguez, Brian Devine, Angus Cook, Philip Weinstein, Paul Van Buynder; Gross alpha and gross beta particle activity in recycled water for augmentation of drinking water supplies. Journal of Water Supply: Research and Technology-Aqua 1 May 2009; 58 (3): 191–202. doi: https://doi.org/10.2166/aqua.2009.058 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex An assessment of potential health impacts of radioactive compounds in recycled water to augment drinking water supplies was conducted. Gross alpha and gross beta particle activity was selected for the screening of radioactive species. Samples both pre- and post-reverse osmosis treatment of secondary effluent in Perth, Australia were examined in both a full-scale and in a pilot water reclamation plant. Risk quotients (RQs) were estimated by expressing the mean (RQ mean) and the maximum concentration (RQ max) at each sampling point as a function of the recommended Australian screening levels of 0.5 Bq/L. The results indicate that reverse osmosis (RO) is able to reduce the concentration of gross alpha particle activity (average removal of almost 80%) and gross beta particle activity (average removal of 95%) and produce water of high quality. Maximum gross alpha particle activity in the recycled water was 0.023 Bq/L and maximum gross beta (excluding 40K) particle activity was 0.03 Bq/L, which correspond to an RQ max of 0.07 for gross alpha and 0.06 for gross beta particle activity, respectively. No increased human radiological risk is anticipated if recycled water is used to augment drinking water supplies in Perth. Australia, radionuclides, reverse osmosis, water quality, water reuse This content is only available as a PDF. © IWA Publishing 2009 You do not currently have access to this content.

AN EXPERIMENTAL ANALYSIS OF THE CONTRIBUTION OF 210Po AND OF 210Po PRODUCED BY 210Pb DECAY TO THE GROSS ALPHA-PARTICLE ACTIVITY OF WATER SAMPLES

The contribution of 210Po and of 210Po produced by 210Pb decay to the gross alpha-particle activity of water samples by U.S. Environmental Protection Agency Method 900.0 is investigated as a function of residue mass and geometry and time between sample collection and analysis. It is shown that these factors can cause the contribution to gross alpha-particle activity of 210Po to be up to 2.0 and 1.1 times the initial 210Po activity for grab and quarterly composite samples, respectively, and can cause the contribution to gross alpha-particle activity of 210Po from 210Pb decay to be up to 1.1 times and 1.5 times the 210Pb activity for grab and quarterly composite samples, respectively. It is also shown qualitatively that at least for some residues, there is a loss of polonium due to volatilization when the sample is heated over a flame.

AN EXPERIMENTAL ANALYSIS OF THE CONTRIBUTION OF 228Ra PROGENY TO THE GROSS ALPHA-PARTICLE ACTIVITY OF WATER SAMPLES

The contribution of 228Ra progeny to the gross alpha-particle activity of water samples by EPA Method 900.0 is investigated as a function of residue mass and geometry and time between sample collection and analysis. It is shown that these factors can cause the contribution of 228Ra progeny to gross alpha-particle activity to be up to 2.2 times the initial 228Ra activity for grab samples and up to 3.5 times the initial 228Ra activity for quarterly composite samples when samples are held for the maximum 6-mo holding time. Thus, under some conditions, 228Ra, by itself, can cause a gross alpha-particle violation (>0.55 Bq L(-1)). Since 228Ra activity is already regulated, a gross alpha-particle activity violation that only exists because of the presence of 228Ra can be considered to be a false positive violation.

AN EXPERIMENTAL ANALYSIS OF THE CONTRIBUTION OF 224Ra AND 226Ra AND PROGENY TO THE GROSS ALPHA-PARTICLE ACTIVITY OF WATER SAMPLES

The gross alpha-particle activity of water samples analyzed by EPA Method 900.0 is investigated as a function of residue mass and geometry, time between sample collection and analysis, and time between sample preparation and analysis for samples containing 224Ra, 212Pb, and 226Ra. It is shown that the gross alpha-particle activity due to 224Ra and its progeny can be up to 10 times the 224Ra activity at collection time and that due to 212Pb progeny can be up to 3 times the 212Pb activity at collection time. In samples with roughly equal activities of 224Ra and 226Ra analyzed soon after collection, it is shown that the gross alpha-particle activity is approximately constant with time because the decay of 224Ra and its progeny is offset by the ingrowth of 226Ra progeny.

AN EXPERIMENTAL ANALYSIS OF SOME OF THE FACTORS AFFECTING GROSS ALPHA-PARTICLE ACTIVITY WITH AN EMPHASIS ON 226Ra AND ITS PROGENY

This work presents an experimental investigation of the measurement of the gross alpha-particle activity of water samples by EPA Method 900.0. The residue produced in Method 900.0 is modeled by a BaSO4 precipitate distributed over a planchet. The dependence of the gross alpha-particle activity on the activity of Ra and its progeny, on the residue mass and geometry, and on the time between sample preparation and analysis is studied. It is shown that these factors can cause the gross alpha-particle activity of a sample to vary by more than a factor of three for replicate samples and to significantly overestimate the alpha activity of the residue. For a given sample geometry, the gross-alpha particle activity generally increases as the residue mass increases owing to the presence of the radium progeny.

DETERMINATION OF GROSS ALPHA, 224Ra, 226Ra, AND 228Ra ACTIVITIES IN DRINKING WATER USING A SINGLE SAMPLE PREPARATION PROCEDURE

The current federal and New Jersey State regulations have greatly increased the number of gross alpha and radium tests for public and private drinking water supplies. The determination of radium isotopes in water generally involves lengthy and complicated processes. In this study, a new approach is presented for the determination of gross alpha, 224Ra, 226Ra, and 228Ra activities in water samples. The method includes a single sample preparation procedure followed by alpha counting and gamma-ray spectroscopy. The sample preparation technique incorporates an EPA-approved co-precipitation methodology for gross alpha determination with a few alterations and improvements. Using 3-L aliquots of sample, spiked with 133Ba tracer, the alpha-emitting radionuclides are isolated by a BaSO4 and Fe(OH)3 co-precipitation scheme. First the gross alpha-particle activity of the sample is measured with a low-background gas-flow proportional counter, followed by radium isotopes assay by gamma-ray spectroscopy, using the same prepared sample. Gamma-ray determination of 133Ba tracer is used to assess the radium chemical recovery. The 224Ra, 226Ra, and 228Ra activities in the sample are measured through their gamma-ray-emitting decay products, 212Pb, 214Pb/214Bi, and 228Ac, respectively. In cases where 224Ra determination is required, the gamma-ray counting should be performed within 2-4 d from sample collection. To measure 226Ra activity in the sample, the gamma-ray spectroscopy can be repeated 21 d after sample preparation to ensure that 226Ra and its progeny have reached the equilibrium state. At this point, the 228Ac equilibration with parent 228Ra is already established. Analysis of aliquots of de-ionized water spiked with NIST-traceable 230Th, 224Ra, 226Ra, and 228Ra standards demonstrated the accuracy and precision of this method. Various performance evaluation samples were also assayed for gross alpha as well as radium isotope activity determination using this procedure and the results were in close agreement with the assigned values. In addition, method comparison results of actual sample analyses agreed well with the ones performed using EPA-approved procedures. With a 3-L sample aliquot and 1,000-min counting time, the average gross alpha minimum detectable concentration (MDC) was about 0.002 Bq L(-1). The average MDC's for 224Ra, 226Ra, and 228Ra were 0.034 Bq L(-1), 0.017 Bq L(-1), and 0.036 Bq L(-1), respectively, based on a 3-L sample aliquot, 85% chemical yield, 40% intrinsic Ge detector, and 1,000-min count time. This method combines and simplifies the analytical procedures and reduces labor while achieving the precision, accuracy, and minimum detection limit requirements of EPA regulations.

Recent outgassing from the lunar surface: The Lunar Prospector Alpha Particle Spectrometer

The Lunar Prospector Alpha Particle Spectrometer (APS) was designed to detect characteristic‐energy alpha particles from the decay of Rn‐222, Po‐218, and Po‐210 and to therefore map sites of radon release on the lunar surface. These three nuclides are radioactive daughters from the decay of U‐238; hence the background level of alpha particle activity is a function of the lunar crustal uranium distribution. Radon reaches the lunar surface either at areas of high soil porosity or where fissures release the trapped gases in which radon is entrained. Once released, the radon spreads out by “bouncing” across the surface on ballistic trajectories in a random‐walk process. The half‐life of Rn‐222 allows the gas to spread out by several hundred kilometers before it decays (depositing approximately half of the Po‐218 recoil nuclides on the lunar surface) and allows the APS to detect gas release events up to several days after they occur. The long residence time of the Pb‐210 precursor to Po‐210 allows the mapping of gas vents which have been active over the last approximately 60 years. The APS found only a faint indication of Po‐218 alpha particles. However, the Rn‐222 alpha particle map shows that radon gas was emanating from the vicinity of craters Aristarchus and Kepler at the time of Lunar Prospector. The Po‐210 alpha particle distribution reveals a variability in time and space of lunar gas release events. Po‐210 and Rn‐222 detections are associated with both thorium enhancements and lunar pyroclastic deposits.

Electret ion chambers for estimating alpha particle energy.

Electret ion chambers (EICs) are inexpensive, lightweight, robust, commercially available, passive, charge-integrating devices for measuring different radiations. At Florida International University's Hemispheric Center for Environmental Technology (FIU-HCET), EIC performance was evaluated with the goal of providing the U.S. Department of Energy (DOE) with a low-cost, low-risk means of alpha contamination monitoring using an existing commercial technology. During this evaluation, sensitivity of electrets in 960-mL hemispherical ion chamber (radius: 7.6 cm) was observed to increase with alpha particle energy because alpha particles expended their entire energy in the chamber volume. This observation prompted us to explore another EIC application: estimation of alpha particle energy. Correlation between electret mid-point voltage, alpha particle energy, and response was developed for the 960-mL EIC and was used to determine energy of an unknown source. The response (change in voltage per disintegration) is the ratio of the change of voltage per unit time and alpha particle activity. Since an EIC measures only the change in voltage per minute, to determine the alpha particle energy, the source activity should be accurately determined by another method.

Lung Carcinogenesis in Rats after Inhalation Exposure to 237 NpO 2

The results of several studies of experimental carcinogenesis suggest that, after inhalation of alpha-particle emitters, lung tumor incidence varies depending on the exposure rate and dose distribution in the tissue. In the case of transuranics, the main influencing factor would be the specific alpha-particle activity of the inhaled actinide. To confirm these results, long-term studies were performed using male Sprague-Dawley rats exposed to (237)NpO(2) by inhalation. The initial lung burdens of the animals ranged from 0. 1 to about 7 kBq. The rats were followed during their life span and weighed regularly, and their lung burdens were determined in vivo and at death to estimate the lung dose. At death, the incidence of lung tumors and their malignancy and histological types were analyzed. The analysis revealed a typically linear-quadratic dose response for incidence of malignant lung neoplasm and a differential dose response for various types of tumors. Although these results confirm the influence of the activity of the inhaled actinide oxide, further experiments are needed to be able to compare a more homogeneous population of animals.