Light weight concrete: Ra, Th, K contents and dose reduction assessment

Four types of light weight concrete (LWC) commonly used in Hong Kong, namely, autoclave aerated concrete (plus lime), autoclave aerated concrete (plus Pulverized Fuel Ash or PFA), concrete with synthetic aggregate ‘Leca’ and concrete with polystyrene bean as aggregate were measured for their ²²⁶Ra, ²³²Th and ⁴⁰K contents using high-resolution gamma spectrometry. All the radionuclide contents except those for the PFA autoclave aerated concrete were below the world averages of building materials. The Ra-equivalents for these four LWC were 49.6, 249, 122 and 44.2 Bq kg⁻¹, respectively, and were much smaller than a recommended limit of 370 Bq kg⁻¹ for construction materials for dwellings. The gamma-dose rate for an indoor environment with partition walls built with LWC was estimated to be about 20 × 10⁻⁸ Gy h⁻¹, which corresponded to a reduction in the effective dose of about 0.25 mSv y⁻¹ when compared to that obtained for an indoor environment built with normal concrete (NC) only. The Rn exhalation rates from the three lowest Ra-equivalent LWC were calculated as 0.509, 1.28, and 0.335 mBq m⁻² s⁻¹, respectively, which corresponded to a reduction in the indoor Rn concentration of around 14 Bq m⁻³ and reduction in the tracheobronchial dose reaching 1 mSv y⁻¹ by using the James lung-dosimetry model, when compared to the case of NC.     

An audit of clinically relevant abnormal laboratory parameters investigating athletes with persistent symptoms of fatigue

The aim of this audit was to assess the yield of a selection of laboratory tests as part of the clinical assessment of the fatigued athlete. Clinical charts and blood test results of fifty consecutive athletes who presented with the primary complaint of fatigue were retrospectively reviewed. Blood tests results reviewed were: haematology (haemoglobin, red cell count, mean cell volume, mean cell haemoglobin content, platelets, white cell count, differential white cell count); erythrocyte sedimentation rate; serum biochemistry (urea, creatinine, electrolytes, urate, glucose, liver function tests, albumin, globulin); blood iron status (serum iron, total iron binding capacity, percent transferring saturation, and ferritin concentration); thyroid stimulating hormone; and immune measures (Epstein–Barr virus serology, cytomegalovirus serology). We identified only 3 abnormal results that contributed to the diagnosis of medical disease as a cause for fatigue. Laboratory testing identified 2 fatigued female athletes with serum ferritin concentration between 15 μg L⁻¹ and 20 μg L⁻¹ plus two of the other criteria of iron concentration (serum iron <10 μmol L⁻¹, iron binding capacity >68 μmol L⁻¹, or transferrin saturation <15%). We concluded that the yield from a selection of blood tests investigating fatigued athletes was low. Future study is needed to further define the role of laboratory testing and to study whether low iron stores in the absence of anaemia is related to symptoms in fatigued athletes.     

Indoor radon measurement with The Lucas cell technique

Rn-222 is the most important source of natural radiation and is responsible for approximately half of the received dose from all sources. Most of this dose is from inhalation of the Rn-222 progeny, especially in closed atmospheres. A Lucas cell technique, using a portable device, “PRASSI” (SILENA mod. 5S), for Rn-222 measurements inside the Centre for Radiation Protection and Radioecology (ZSR), Hannover University was used. The portable radon monitor PRASSI is suitable for radon gas continuous or grab sampling measurements with the scintillation cell technique. In recognition of the wide periodic variations in concentration, measurements were made daily for extended periods. At the same time, meteorological variables, such as temperature and humidity were observed so that their influence on radon levels could be evaluated. The radon average concentration during the year was about 55.9 Bq/m³ which gives rise to an annual effective dose 2.2 mSv y⁻¹. The radon concentration is within the limits prescribed by the International Commission for Radiation Protection. A detailed analysis of radon distribution with seasonal variation is presented.     

Investigating the background of a 1-cm quartz gas proportional counter

The background count rate of a 1-cm³ quartz gas proportional counter (GPC) was investigated for measuring natural radioactivity levels of small samples. Using a new multiparameter digital counting system, spurious or afterpulses that contribute to background were identified by their pulse waveform and by a special event indicator defined by the time (<2000 μs) between two successive pulses. With the GPC in coincidence with a low-background NaI(Tl) scintillation guard detector, the weighted mean and standard uncertainty anticoincidence counts per day (d⁻¹) was 6.2±0.4 d⁻¹.     

A liquid-scintillation-based primary standardization of Pb

A new radioactivity solution standard of ²¹⁰Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new ²¹⁰Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133±0.002) g of a nominal 1 mol L⁻¹ nitric acid solution, has a density of (1.028±0.002) g mL⁻¹ at 20 °C, has carrier ion concentrations of about 11 μg Pb²⁺ and 21 μg Bi³⁺ per gram of solution, and is certified to contain a massic activity (9.037±0.22) kBq g⁻¹ as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the ²¹⁰Pb content of the solution was based on 4πβ liquid scintillation (LS) measurements using CIEMAT/NIST ³H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe γ-ray spectrometry, by 2π spectrometry with a Si surface barrier detector of separated ²¹⁰Po, and by 4πβ(LS)–γ(NaI) anticoincidence counting.     

Decomposition of aqueous solutions of phenol using high energy electron beam irradiation—A large scale study

High-energy electron-beam irradiation was used to remove phenol from aqueous solution. The variables that affected phenol decomposition were solute concentration, absorbed dose and total alkalinity. Experiments were conducted at large scale (480 L min⁻¹), at solute concentrations of 10.6, 106 and 531 μmol L⁻¹ (1, 10 and 50 mg L⁻¹) over the pH range 5–9, and in the presence and absence of solids (3% w/w kaolin clay). Absorbed doses ranged from 0–7 kGy (0–700 krad). At low absorbed doses, catechol, hydroquinone and resorcinol were identified as the major reaction byproducts. These compounds are consistent with hydroxyl radical (OH·) addition to phenol. Subsequent ring cleavage of hydroxylated phenolic radicals and continued oxidative processes resulted in the formation of formaldehyde, acetaldehyde, glyoxal and formic acid. At high doses only trace amounts of the carbonyl derivatives were observed. Two recirculation experiments were conducted at higher phenol concentrations (≈950 μmol L⁻¹) and it was shown that phenol was removed while the total organic carbon of the solution decreased only slightly. These results suggest that phenol was not mineralized but, rather, that irradiation resulted in the possible formation of higher molecular weight polymers.     

The effect of contrast temperature water therapy on repeated sprint performance

The aim of this study was to compare the effectiveness of two recovery techniques on blood lactate and repeated sprint performance. In a randomised cross-over design 20 junior representative rugby players (aged 19 ± 1 years) were given either contrast temperature water therapy or active recovery after performing a repeated sprint test. The test was then repeated 1 h later to gauge the effects of the two recovery methods on subsequent repetitive sprinting performance. One week later, the two groups were reversed and the testing repeated. The test consisted of ten 40-m sprints with a 30-s turn-around between sprints. Recovery consisted of 6 min slow jogging (6.8 km h⁻¹) for the active recovery group or 6 min of contrast temperature water therapy consisting of three 1-min hip-height immersions in cold water (8–10 °C) alternated with three 1-min hot water (38 °C) showers. Blood lactate concentration and heart rates were measured throughout the testing. Relative to the active recovery group the contrast temperature water therapy group showed a substantial decrease in blood lactate concentration 3 min after the procedure (−2.1 mmol L⁻¹, 95% confidence limits, ±1.8 mmol L⁻¹), and substantially lower heart rates both during the procedure (−9.1 ± 8.7 min⁻¹) as well as 1 h later during the second set of sprints (−11.7 ± 8.6 min⁻¹). Effects of recovery group on repeated sprint performance were small to trivial and unclear. Compared to active recovery, contrast temperature water therapy decreases blood lactate concentration and heart rate but has little effect on subsequent repetitive sprinting performance.     

Radiochemical purification of no-carrier-added scandium-47 for radioimmunotherapy

A procedure, adaptable to large-scale remote operation, was developed to purify no-carrier-added (NCA) ⁴⁷Sc from irradiated Ti targets. Methods based on extraction chromatography and cation-exchange chromatography were compared. Results of this comparison led to the development of an optimized procedure based on cation-exchange with Dowex AG 50W-X4 and ⁴⁷Sc elution with HCl/HF. This method gave 90–97% overall ⁴⁷Sc recovery, with a Ti separation factor greater than 2.4×10⁻⁵, and specific activities ≥0.9 GBq μg⁻¹. Use of the ⁴⁷Sc product, for labeling monoclonal antibodies, resulted in consistent labeling yields of ≥90%.     

Investigation of the NMR relaxation rate dose-response of a ceric sulphate dosimeter

The relationship between the radiation absorbed dose and the NMR longitudinal and transversal relaxation rates, R₁ and R₂, respectively, of a ceric sulphate dosimeter was examined. By adding copper sulphate, the R₁ and R₂ dose-responses were found to be linear up to 60 kGy with dose sensitivities of 13×10⁻⁶ and 15×10⁻⁶ s⁻¹ Gy⁻¹, respectively. There is thus the potential for a three-dimensional ceric dosimeter for high dose applications, provided a suitable gelling substance is used.     

A Monte Carlo brachytherapy study for dose distribution prediction in an inhomogeneous medium

The purpose of this study was to present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions. This study was carried out using a Monte Carlo simulation of the dose distribution in homogeneous medium for 3 commonly used brachytherapy seeds. The 3 seeds investigated in this study are iridium-192 (¹⁹²Ir) iodine-125 (¹²⁵I), and palladium-103 (¹⁰³Pd). The computer code was validated by comparing the specific dose rate (Λ), the radial dose function g(r), and anisotropy function F(r,θ) for all 3 seeds with the AAPM TG-43 dosimetry formalism and current literature. The ¹⁹²Ir seed resulted in a dose rate of 1.115 ± 0.001 cGy-hr⁻¹-U⁻¹, the ¹²⁵I seed resulted in a dose rate of 0.965 ± 0.006 cGy/h⁻¹/U⁻¹, and the ¹⁰³Pd seed resulted in a dose rate of 0.671 ± 0.002 cGy/h⁻¹/U⁻¹. The results for all 3 seeds are in good agreement with the AAPM TG-43 and current literature. The validated computer code was then applied to a simple inhomogeneous model to determine the effect bone has on dose distribution from an interstitial implant. The inhomogeneous model showed a decrease in dose rate of 2% for the ¹⁹²Ir, an increase in dose rate of 84% for ¹²⁵I, and an increase in dose rate of 83% for the ¹⁰³Pd at the surface of the bone nearest to the source.     

Contrast water immersion hastens plasma lactate decrease after intense anaerobic exercise

The benefits of rapid recovery after intense exercise are widely recognised, and lactate elimination is one indicator of recovery rate. This study examined the effect of contrast (alternating hot and cold) water immersion (CWI) on the rate of plasma lactate decrease during recovery after intense anaerobic exercise. Eleven subjects on each of two occasions undertook four successive 30-s Wingate tests separated by 30-s rest periods. On each occasion, plasma lactate concentration during recovery was measured 5 min post-exercise and thereafter at 5 min intervals for 30 min. On one occasion (determined randomly), the subjects recovered passively (PR) on a recovery bed and, on the other, they alternated partial body immersion in hot (36 °C) and cold (12 °C) water baths. Plasma lactate concentrations were analysed by repeated measures analysis of variance and by fitting a linear regression model, allowing for both gender and recovery mode differences. The rate of decrease in plasma lactate concentration over the 30-min recovery period was significantly higher (p < 0.001) in CWI; 0.28(±0.02) mmol L⁻¹ min⁻¹ (CWI) compared to 0.22(±0.02) mmol L⁻¹ min⁻¹ (PR). These values do not differ significantly between males and females. Contrast water immersion is a valid method of hastening plasma lactate decrease during recovery after intense anaerobic exercise for both males and females. An approximately 1.8 mmol L⁻¹ difference between the two conditions may be expected after 30 min. With differences among elite competitors as little as 1–2%, this reduction may be of practical significance.     

Development of a simple neutron irradiation facility utilizing the stray neutron field of a medical cyclotron

During the routine isotope production schedule at the Australian National Medical Cyclotron thick copper plates, electroplated with enriched target materials, are bombarded with 30 MeV protons with an average beam current of 200 μA. As a result an intense high-energy, prompt neutron flux of the order of 1.72 × 10¹³ neutrons·cm⁻²·2⁻¹ is generated in the immediate vicinity of the target. The stray fast neutrons were moderated using a water-filled PVC bucket placed on the target station. A maximum thermal neutron flux of 3.88 × 10⁹ neutrons·cm⁻²·s⁻¹ was measured in the bucket using cobalt activation discs. The thermal neutrons from this irradiation facility has been used for the neutron activation analysis of trace elements in archaeological artefacts. It has also been planned to utilize the fast neutron flux by varying the geometry of the water moderator in order to estimate oxygen concentration in high-temperature superconductors and aluminium and silicon in ceramics.     

Thermoluminescence and electron spin resonance properties of some travertines from Turkey

For the sake of dating certain calcite geological samples, the TL and ESR properties of travertines from Denizli (in the southwestern part of Turkey) were studied and the effects of pre-heating temperature and pre-heating time on the sensitivity of the samples to radiation evaluated. Heat treatment above 350°C increases the sensitivity of all radiation-induced TL peaks except the 330°C glow peak. Results of gamma-ray dose calibration in travertine (CaCO₃ crystal of trigonal symmetry) indicate that the 180 and 280°C TL peak amplitudes increase exponentially with dose. We show that second-order kinetics characterizes the 180 and 280°C glow peaks reasonably well. The Mn²⁺ lines of the ESR spectra are used to investigate the thermal decomposition processes of travertine samples, showing very good agreement with those of thermogravimetry. Glow mechanisms of TL in travertine have also been studied using ESR analysis. The pre-heating and subsequent laboratory irradiation procedure is found to enhance the TL and ESR signals of CO₃³⁻ and CO₂⁻ centres. An isochronal thermal anneal sequence experiment showed that 180 and 280°C peaks in travertines are correlated with CO₃³⁻ and CO₂⁻ centres in the same way that the peak at 330°C is correlated with SO₂⁻ centres. A model for the recombination mechanism is suggested on the basis of the TL and ESR measurements.     

Effect of pH and concentration on the diffusion of radiostrontium in compacted bentonite—a capillary experimental study

The effects of pH and Sr²⁺ solution concentration on diffusion and sorption of Sr²⁺ in compacted bentonite (ρ_b=1000±30 kg/m³) were studied using an “in-diffusion” method at an ionic strength of 0.1 M NaClO₄. The results (distribution coefficients, K_d, apparent and effective diffusion coefficients, D_a and D_e) derived from the capillary method are in good agreement with the literature data obtained for similar bentonite dry densities and fit Fick's second law very well. The results suggest that the diffusion of Sr²⁺ in compacted bentonite decreases slightly with increasing pH values and also increases slightly with increasing Sr²⁺ solution concentration. The distribution coefficients are weakly dependent on the solution concentrations and show a slight increase with increasing pH values. The average effective diffusion coefficient of Sr²⁺ in compacted bentonite is (1.2±0.2)×10⁻⁹ m²/s, surface diffusion effects are found for the diffusion of Sr²⁺ in compacted bentonite.     

Characterization of trace elements in Casearia medicinal plant by neutron activation analysis.

Leaves of Casearia sylvestris, Casearia decandra and Casearia obliqua plant species, collected at the Atlantic Forest in Brazil, were analyzed by using instrumental neutron activation analysis (INAA). Short and long irradiations using thermal neutron flux of the IEA-R1 nuclear reactor were carried out for these analyses. Concentrations of Ca, K and Mg were found in these samples at the percentage levels, Br, Cl, Fe, Mn, Na, Rb and Zn at the μg g⁻¹ levels and Co, Cr, Cs, La, and Sc at the μg kg⁻¹ levels. Comparisons were made among the element concentrations obtained in these three Casearia species and significant differences were found for the elements Cl, Co, Cs, Cr, La, Mn, Na and Sc. The precision and the accuracy of the results were evaluated by analyzing the certified reference materials NIST-1515 Apple Leaves and NIST-1573a Tomato Leaves.     

Theoretical basis for long-term measurements of equilibrium factors using LR 115 detectors

In this paper, we propose a method to determine the equilibrium factor using a bare LR 115 detector. The partial sensitivities ρ_i of the LR 115 detector to ²²²Rn and its alpha-emitting short-lived progeny, ²¹⁸Po and ²¹⁴Po, were investigated. We first determined the distributions of lengths of major and minor axes of the perforated alpha tracks in the LR 115 detector produced by ²²²Rn, ²¹⁸Po and ²¹⁴Po through Monte Carlo simulations. The track parameters were calculated using a track development model with a published V function, by assuming a removed active layer of 6.54 μm. The distributions determined for different alpha emitters were found to completely overlap with one another. This implied equality of partial sensitivities for radon and its progeny, which was also confirmed through analytical considerations. Equality of partial sensitivities makes possible convenient measurements of the proxy equilibrium factor F_p, which is defined in the present work as (F₁+F₃) and is equal to the ratio between the sum of concentrations of the two alpha emitting radon progeny (²¹⁸Po+²¹⁴Po) to the concentration of radon gas (²²²Rn). In particular, we have found F_p=(ρ/ρ_itC₀)−1, where ρ (track/m²) is the total track density on the detector, ρ_i=0.288×10⁻² m, t is the exposure time and C₀ (Bq/m³) is the concentration of ²²²Rn. If C₀ is known (e.g. from a separate measurement), we can obtain F_p. The proxy equilibrium factor F_p is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor.     

Development and application of Marinelli beaker standards for monitoring radioactivity in Dairy-Products by gamma-ray spectrometry

Marinelli (reentrant) beakers are recommended for measurement of low-activity radioactive environmental samples, in both liquid and solid phase.

The preparation of Marinelli beaker standards of milk powder containing ²³²ThO₂ at secular equilibrium with its daughter radionuclides was studied. Standards were prepared by mixing of known amounts of solid ThO₂ and milk powder. The densities of the standards were 0.5–0.7 kg dm⁻³.

Measurements of calibrated Marinelli beaker standards with HPGe detector showed that the energy dependence of the efficiency is similar to that of a point source, i.e. an almost linear dependence of log-efficiency vs. log-energy in the 200–2000 keV range, however the parabolic correlation fits better.

The validity of these standards was checked by comparison with certified standard reference material IAEA-152-Milk powder containing radiocesium and radiopotassium. The results obtained were found to be in a good agreement with the published certified data.

The limit of detection for the determination of radiocesium by gamma ray spectrometry under the prevailing experimental conditions is 0.03 Bq (i.e. 0.8 pCi), for samples of dairy products having lower densities of 0.7 kg dm⁻¹.     

Highly efficient automated synthesis of [C]choline for multi dose utilization

[¹¹C]Choline has been under investigation as a PET ligand for imaging tumor tissue, especially prostate cancer. An improved, automated synthesis of the tracer now was established. [¹¹C] Choline was produced by labeling 2-(dimethylamino)-ethanol (DMAE) with [¹¹C]CH₃I in a Tefzel^® tube at room temperature without solvent. The product was purified using a cation exchange cartridge. Reaction conditions were optimized with respect to synthesis time and amount of DMAE, resulting in radiochemical yields higher than 80% using 60 μl of DMAE in 20 min, radiochemical purity was >99% and residual DMAE was below 10 ppm. After ¹¹C-production of 1 h at 50 μA [¹¹C]choline activities of 30.0±5.6 GBq (n=29) were obtained in sterile solution ready for intravenous administration.     

Evaluation of Dosimetric Parameters for Various Ir Brachytherapy Sources Under Unbounded Phantom Geometry by Monte Carlo Simulation

As per TG-43 dose calculation formalism, it is essential to obtain various dosimetric parameters such as the air-kerma strength, dose rate constant, radial dose function, and anisotropy function, as they account for accurate determination of dose rate distribution around brachytherapy sources. Most of the available reported Monte Carlo simulations were performed in liquid water phantoms with a bounded region of 30-cm diameter. In this context, an attempt was made to report the dosimetric parameters for various commercially available pulsed-dose rate (PDR) and high-dose rate (HDR) sources under unbounded phantom conditions, as the data may be used as input to treatment planning systems (TPSs) for quality control assistance. The air-kerma strength per unit activity, S_k/A, was computed for various Iridium-192 (¹⁹²Ir) sources in dry air medium. The air-kerma strength and dose rate constant for old PDR is (9.77 ± 0.03) 10⁻⁸ U/Bq and 1.124 ± 0.001 cGyh⁻¹U⁻¹; for new PDR, the values are (9.96 ± 0.03) 10⁻⁸ U/Bq and 1.124 ± 0.001 cGyh⁻¹U⁻¹; for old MHDR, the values are (9.80 ± 0.01) 10⁻⁸ U/Bq and 1.115 ± 0.001 cGyh⁻¹U⁻¹; for new MHDR, (9.80 ± 0.01) 10⁻⁸ U/Bq and 1.112 ± 0.001cGyh⁻¹U⁻¹; for old VHDR, the values are (10.32 ± 0.01) 10⁻⁸ U/Bq and 1.035 ± 0.002 cGyh⁻¹U⁻¹; for new VHDR, the values are (10.34 ± 0.02) 10⁻⁸ U/Bq and 1.096 ± 0.001 cGyh⁻¹U⁻¹. The computed radial dose function values and anisotropy function values are also in good agreement with available data.     

Measurement of Pu γ-ray intensities between 148 and 161 keV

Utilizing Pu isotopic standards characterized by the Institute for Nuclear Materials and Measurement (IRMM), New Brunswick Laboratory (NBL) measured the γ-ray branching ratios of the 148.567-keV ²⁴¹Pu, the 152.72-keV ²³⁸Pu, the 159.995-keV ²⁴¹Pu and the 160.28-keV ²⁴⁰Pu γ-rays. The study reported here includes the measurement of four IRMM standards, utilizing three different detectors for a total of 16 spectra, finding branching ratios of (1.863 ± 0.008) × 10⁻⁶, (9.230 ± 0.068) × 10⁻⁶, (6.321 ± 0.040) × 10⁻⁸ and (4.065 ± 0.017) × 10⁻⁶, γ/disintegration, respectively.