Radiation dose aspects in the handling of emerging nuclear fuels.

The occupational annual dose levels, encountered at fabrication of emerging nuclear fuels, have been studied. Emerging fuels for the single and multiple recycling of Pu and MA have resulted in considerably higher gamma and neutron doses in comparison with commercial fuels. The occupational dose limit is exceeded at fabrication by a single fuel rod in all fuel cases with (241)Am and Cm isotopes present in their composition. In the absence of these isotopes, 2-4 adjacent fuel rods are sufficient to exceed the limit. Self-shielding within the fuel reduces significantly only the gamma dose that would have been delivered otherwise. Hence, only the first row of fuel rods in an assembly contributes to the dose, whereas in the case of neutrons, all fuel rods contribute.

The solid angle subtended by a well-type detector and a cylindrical source.

A Monte Carlo approach, based on total variance reduction, was presented in order to evaluate the solid angle subtended between a well-type NaI detector and a cylindrical source within the well. The results obtained, in the form of the geometrical efficiency εg, were within 0.7% of those in the literature, for a point and a volumetric radioactive source within the well. The effect of self-absorption on the geometrical efficiency was investigated for different gamma-ray energies emitted by the volumetric source, different source matrices and radii. Self-absorption is found to be particularly significant for gamma-ray energies below 300keV regardless the source matrix and radius. Furthermore, self-absorption becomes significant, in the case of the larger radius volumetric source, for the gamma-ray energies up to 1MeV considered. Hence, the effect of self-absorption on the geometrical factor should be considered in the absolute quantification of radioactivity of volumetric sources.

The comparison of four neutron sources for Prompt Gamma Neutron Activation Analysis (PGNAA) in vivo detections of boron.

A Prompt Gamma Ray Neutron Activation Analysis (PGNAA) system, incorporating an isotopic neutron source has been simulated using the MCNPX Monte Carlo code. In order to improve the signal to noise ratio different collimators and a filter were placed between the neutron source and the object. The effect of the positioning of the neutron beam and the detector relative to the object has been studied. In this work the optimisation procedure is demonstrated for boron. Monte Carlo calculations were carried out to compare the performance of the proposed PGNAA system using four different neutron sources (241Am/Be, 252Cf, 241Am/B, and DT neutron generator). Among the different systems the 252Cf neutron based PGNAA system has the best performance.

Role of continuous positive airway pressure to the non-ventilated lung during one-lung ventilation with low tidal volumes.

INTRODUCTION: In multiple study populations large tidal volumes (8 - 12 ml/kg) have deleterious effects on lung function in multiple study populations. The accepted approach to hypoxemia during one-lung ventilation is the application of continuous positive airway pressure to the non-ventilated lung first, followed by application of positive end-expiratory pressure to the ventilated lung. To our knowledge the effectiveness of positive end-expiratory pressure or continuous positive airway pressure on maintaining PaO(2) with one-lung ventilation was not studied with smaller tidal volume (6ml/kg) ventilation. Our objective was to compare continuous positive airway pressure of 5 cm H(2)O or positive end-expiratory pressure of 5 cm H(2)O during small tidal volume one-lung ventilation. METHODS: Thirty patients undergoing elective, open thoracotomy with one-lung ventilation were randomized to continuous positive airway pressure or positive end-expiratory pressure and then crossed over to the other modality.  RESULTS: There was a statistically significant higher PaO(2) (141±81.6 vs 112±48.7, p = 0.047) with continuous positive airway pressure than positive end-expiratory pressure while on one-lung ventilation. Two patients desaturated requiring 100% O(2) with both positive end-expiratory pressure and continuous positive airway pressure. On two occasions the surgeon requested the continuous positive airway pressure be discontinued due to lung inflation. CONCLUSION: The use of continuous positive airway pressure of 5 cm H(2)O to the non-ventilated lung while using small tidal volumes for one-lung ventilation improved PaO(2) when compared with positive end-expiratory pressure of 5 cm H(2)O to the ventilated lung.

The concentration of 137Cs in the surface of the Greek marine environment.

The radiological status of the Greek marine environment, prior to the Chernobyl accident, was characterized mainly by the fallout from nuclear weapon tests. However, the release of radioactivity into the environment from the accident in the Chernobyl Nuclear Power Plant and its deposition in the Greek marine environment resulted in an increase of the (137)Cs activity concentration by approximately one order of magnitude. In addition, the direct transport of radiocaesium into the North Aegean Sea has been further influenced by the late impact of the Chernobyl accident on the Greek marine environment, related to the transfer of (137)Cs, mainly through the Dnieper but also the Danube rivers, to the Black Sea and further to the North Aegean Sea through the Straits of Dardanelles. The aim of this work is to provide a present day picture of the geographic variation of the concentration of (137)Cs in the surface layer of the Greek marine environment and hence, to evaluate the annual committed effective dose delivered to humans through the ingestion pathway from marine sources.

Arterial pCO2 changes during thoracoscopic surgery with CO2 insufflation and one lung ventilation.

INTRODUCTION: The respiratory effects (changes in pH and PaCO(2)) of carbon dioxide insufflation in thoracoscopic surgery in adult patients with pulmonary disease were not documented previously. METHODS: In this observational study 21 patients scheduled for elective thoracoscopic surgery with one lung ventilation using a double lumen tube and intraoperative carbon dioxide insufflation were studied. Arterial blood gas findings were correlated with demographic and intraoperative variables. RESULTS: When compared to baseline (10-15 minutes of one lung ventilation before carbon dioxide insufflation), carbon dioxide insufflation lowered the pH, 7.31±0.08 vs 7.40±0.05 (p<0.001) caused increased PaCO(2), 53±12 vs 42±6.0 (p<0.001) at 40-60 minutes after carbon dioxide insufflation. These derangements in arterial blood gases persisted in the post-anesthetic care unit with pH 7.33±0.04 vs 7.40±0.05 (p<0.001) and PaCO(2) 51±6.7 vs 42±6.0 (p<0.001). Moderate hypercarbia defined as PaCO(2) >50 mmHg, developed in 12 of 21 patients (57%) and was associated to lower FEV1/FVC ratios 60±21 vs 81±3%, older age 69±9 vs 56±17 years, and history of smoking, 43 ± 30 vs 16±21 pack years, p<0.05. CONCLUSIONS: Intrathoracic carbon dioxide insufflation causes significant derangements in pH and PaCO(2) which is worse in patients with lower FEV1/FVC, increased age and smoking history.

Relative radiological impact from a reactor accident in the case of emerging nuclear fuels.

An assessment has been carried out on the radiological impact on an area contaminated from an accident of a nuclear reactor loaded with different actinide fuels considered in transmutation and recycling schemes. The impact of these schemes is compared to reference cases of commercial UO2 and MOX fuels. The effective dose equivalent delivered to permanent residents has been calculated using the RESRAD code and used as an index for the assessment purposes. The highest and lowest doses would be delivered from the self-generating recycling of actinides in fast and thermal reactors, respectively. External irradiation is the main contributor to the dose delivered to the target population in comparison to ingestion and inhalation. The external dose delivered would be attributed for the first few years to 134Cs and for the following several tens of years to 137Cs.

Provenance of unknown plutonium material.

The determination of the provenance of 'unknown' plutonium material is demonstrated through a simulation study based on an isotopic fingerprinting approach. Plutonium of known provenance was considered as the 'unknown' nuclear material in order to evaluate the potential of the approach and verify its predictive capabilities. Factor analysis was used to compare the Pu isotopic composition of the 'unknown' material with Pu isotopic compositions simulating well known spent fuels from a range of commercial nuclear power stations. The provenance of the 'unknown material' is assigned to the commercial fuel with which exhibits the highest degree of similarity with respect to the Pu composition. The approach appears promising since it accurately predicted the provenance of the one 'unknown' sample considered; nevertheless, the approach is still at the development stage. Important challenging issues related to the simulation uncertainties and its testing on real laboratory samples have to be explored prior to evaluating the potential of the approach.

A mathematical description of the diurnal variation of radon progeny.

The variation of the alpha radioactivity in the air near the ground and the ground-level total gamma radiation has been monitored in North-eastern Greece over several days. Meteorological information regarding the temperature of the air and humidity has been simultaneously recorded. The alpha-radioactivity shows a periodic diurnal variation with a peak in the morning followed by a decrease in the afternoon; then, the variation rises again to the peak the next morning. The variation of the ground gamma-radiation follows that of the air alpha-radioactivity. Furthermore, their significant dependence on the air temperature and humidity is confirmed, rising with an increase in humidity and a decrease in temperature. Hence, a mathematical function has been developed to describe the diurnal variation of the alpha-radioactivity in terms of the ground-level gamma-radiation and the meteorological variables of temperature and humidity.

Diurnal variation of radon progeny.

The diurnal variation of the gross alpha (alpha) radioactivity in the air near the ground and the gamma (gamma) radioactivity emitted from the ground have been monitored in North-eastern Greece. Meteorological information comprising air temperature and humidity has been simultaneously recorded. Over a period of the 24h of a typical day, the variation of alpha-radioactivity reaches a peak in the morning followed by a remarkable decrease, rising to a second peak in the afternoon. Furthermore, its significant dependence on the air temperature and humidity is confirmed, rising with an increase in humidity and decrease in temperature. The variation of the ground gamma-radioactivity follows that of the air alpha-radioactivity. A mathematical model has been developed to describe the diurnal variation of the alpha-radioactivity in the air near the ground in terms of the above meteorological variables and ground level gamma-radioactivity.

An assessment of the external radiological impact in areas of Greece with elevated natural radioactivity.

In the present study, the radiological impact assessment in three selected areas of elevated natural radioactivity in Greece is attempted, based on measurements, theoretical relations, and simple model application. These areas are Milos--an island of volcanic origin in Cyclades Archipelago, Ikaria--an island in the Eastern Aegean Sea and Loutraki--a coastal area in mainland Greece. These areas are characterized by their geothermal springs and vents, which emit fluids into the littoral and sublittoral zones. The results include: (a) the exposure dose rates assessed by a car-borne scintillation spectrometry system; (b) laboratory measurements of the activity concentrations of the gamma-emitters of 238U and 232Th series and 40K in soil, spring water, seawater and sediments by gamma-spectrometry; (c) estimations of the effective dose rate equivalents and health risk assessment for humans and external dose rates for natural aquatic populations in relation to organism habitat; and (d) a radiological evaluation for the environmental quality, in terms of the discrete zones of impact of ionizing radiation.

Determination of the origin of unknown irradiated nuclear fuel.

An isotopic fingerprinting method is presented to determine the origin of unknown nuclear material with forensic importance. Spent nuclear fuel of known origin has been considered as the 'unknown' nuclear material in order to demonstrate the method and verify its prediction capabilities. The method compares, using factor analysis, the measured U, Pu isotopic compositions of the 'unknown' material with U, Pu isotopic compositions simulating well known spent fuels from a range of commercial nuclear power stations. Then, the 'unknown' fuel has the same origin as the commercial fuel with which it exhibits the highest similarity in U, Pu compositions.

Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold.

PURPOSE: This study was conducted to test the hypothesis that clonidine produces a dose-dependent increase in the sweating threshold and dose-dependent decreases in vasoconstriction and shivering thresholds. METHODS: Six healthy subjects (two female) were studied on four days after taking clonidine in oral doses of either 0 (control), 3, 6 or 9 micrograms.kg-1. The order followed a balanced design in a double-blind fashion. Oesophageal temperature and mean skin temperature (from 12 sites) were measured. Subjects were seated in 37 degrees C water which was gradually warmed until sweating occurred (sweat rate increased above 50 g.m-2.h-1). The water was then cooled gradually until thresholds for vasoconstriction (onset of sustained decrease in fingertip blood flow) and shivering (sustained elevation in metabolism) were determined. Thresholds were then referred to as the core temperature, adjusted to a designated mean skin temperature of 33 degrees C. RESULTS: High dose clonidine similarly decreased the adjusted core temperature thresholds for vasoconstriction by 1.16 +/- 0.30 degrees C and for shivering by 1.63 +/- 0.23 degrees C (P < 0.01). The dose response effects were linear for both cold responses with vasoconstriction and shivering thresholds decreasing by 0.13 +/- 0.05 and 0.19 +/- 0.09 degree C.microgram-1 respectively (P < 0.0001). The sweating threshold was unaffected by clonidine, however the interthreshold range between sweating and vasoconstriction thresholds increased from control (0.19 +/- 0.48 degree C) to high dose clonidine (1.31 +/- 0.54 degrees C). CONCLUSION: The decreases in core temperature thresholds for cold responses and increased interthreshold range are consistent with the effects of several anaesthetic agents and opioids and is indicative of central thermoregulatory inhibition.

Fluorine concentrations in bone biopsy samples determined by proton-induced gamma-ray emission and cyclic neutron activation.

Fluorine concentrations in bone biopsy samples taken from the iliac crest of subjects, divided into four groups depending on the length of dialysis treatment, and aluminium levels in blood and bone pathology, in terms of osteoporosis, were determined by two instrumental methods. Proton-induced gamma-ray emission (PIGE), making use of the resonance reaction of 19F(p, alpha gamma)16O at 872 keV, and cyclic neutron activation analysis (CNAA), using the 19F(n, gamma)20F reaction in a reactor irradiation facility, were employed. Rutherford backscattering (RBS) was used to calculate the volume, and, hence, mass of the sample excited in PIGE by determining the major element composition of the samples in order to express results in terms of concentration. From this preliminary investigation, a relationship is suggested between fluorine concentrations in bone and aluminium levels in the system.

Inductively coupled atomic emission spectrometry and neutron activation analysis for the determination of element reference values in human lung tissue.

An investigation was undertaken in order to assess the performance of neutron activation analysis and inductively coupled plasma atomic emission spectrometry techniques for determining reference values for minor and trace elements in human lungs of urban subjects. Results show that in both instances experimental conditions must be carefully optimized to guarantee reliability of experimental data. Strict criteria for tissue sampling and pretreatment also had to be set. Provisional reference values for ca. 50 elements could thus be established.

Trace element reference values in tissues from inhabitants of the European community. I. A study of 46 elements in urine, blood and serum of Italian subjects.

Neutron activation analysis-electrothermal atomic absorption spectroscopy (ETA-AAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) have been used for the determination of 46 elements in urine, 35 in blood and 26 in serum of unexposed Italian subjects living in the same region (Lombardy). The results allowed the proposal of reference values for various elements determined in more than 350 healthy subjects, these being Ag, Al, As, Be, Bi, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se, Tl, V, Zn, in urine; Ag, As, Bi, Cd, Cr, Co, Cu, Hg, Pb, Se, Tl, Zn in blood; and Ag, Al, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se, Tl, V, Zn in serum (or plasma). For all other elements indicative values are suggested. In addition to the mean value and the "reference range", a "range of uncertainty" and an upper limit above which metabolic abnormalities could be expected have also been defined on the basis of simple statistical considerations.

In vitro inhibition of HIV-1 proteinase by cerulenin.

Retroviruses encode proteinases necessary for the proteolytic processing of the viral gag and gag-pol precursor proteins. These enzymes have been shown to be structurally and functionally related to aspartyl proteinases such as pepsin and renin. Cerulenin is a naturally occurring antibiotic, commonly used as an inhibitor of fatty acid synthesis. Cerulenin has been observed to inhibit production of Rous sarcoma virus and murine leukaemia virus by infected cells, possibly by interfering with proteolytic processing of viral precursor proteins. We show here that cerulenin inhibits the action of the HIV-1 proteinase in vitro, using 3 substrates: a synthetic heptapeptide (SQNYPIV) which corresponds to the sequence at the HIV-1 gag p17/p24 junction, a bacterially expressed gag precursor, and purified 66 kDa reverse transcriptase. Inhibition of cleavage by HIV-1 proteinase required preincubation with cerulenin. Cerulenin also inactivates endothiapepsin, a well-characterised fungal aspartyl proteinase, suggesting that the action of cerulenin is a function of the common active site structure of the retroviral and aspartic proteinases. Molecular modelling suggests that cerulenin possesses several of the necessary structural features of an inhibitor of aspartyl proteinases and retroviral proteinases. Although cerulenin itself is cytotoxic and inappropriate for clinical use, it may provide leads for the rational design of inhibitors of the HIV proteinase which could have application in the chemotherapy of AIDS.

Trace element analysis in environmental and occupational health: box plot representation of elemental composition results.

Box plots are used in the visual representation of large data sets and in exploratory data analysis. They display batches of data with five values being used to describe the data set. These are the median, the upper and lower extremes of the range of values and the 75 and 25 percentiles. A notch about the median, e.g. at the 95 percent level of significance, can be incorporated in the display allowing the difference between the medians of different sets to be established. The method, although not recently established, has so far found little application in the analytical field. Hence, in an effort to strengthen its applicability, the features and capabilities of box plots, in terms of data reporting and insight into the data set, are here described through elemental composition studies in relation to environmental and occupational health.

Multielement determination of metals in biological specimens of hard metal workers: a study carried out by neutron activation analysis.

Multielemental analysis, using neutron activation, was carried out on the urine, whole blood, pubic hair and toenails of thirty subjects occupationally exposed to hard metal dusts. A high concentration of Co, W and Cr was observed in all samples analysed. The concentrations determined, when subjected to statistical analysis using pattern recognition techniques (e.g. cluster analysis), indicated a positive correlation, at p = 0.001, for the pair (Co, W) in urine and blood, as well as a possible influence of Cr on this pair.