Multivariate statistical analyses of artificial radionuclides and heavy metals contaminations in deep mud of Keban Dam Lake, Turkey.

On the basis of the artificial radioactive and heavy metal compositions, factor and cluster analyses are employed to identify the inter-relationship among different variables and their similarity groups. In this paper, 15 physico-chemical variables, including the activities of 137Cs, 90Sr, total alpha, total beta, and concentrations of Fe, Mg, Ca, K, Na, Zn, Cu, Cr, Co, Ni, and Mn, are used for the application of the proposed methodologies. The spatio-temporal samples of these variables are collected from deep mud at about 30-35 m mean depth in the reservoir of Keban Dam Lake, which is located in the eastern part of Turkey. Spatially, there are 20 sampling sites at the dam with 150 km2 lake surface area where samples were taken in 2006. The lake is affected by man-made and industrial influxes. The application of the factor and cluster analysis methods yields that the former method reduces the number of variables into six factors with 77.2% variance explanation whereas the latter yields three distinctive groups of the same variables.     

Large-scale purification of 90Sr from nuclear waste materials for production of 90Y, a therapeutic medical radioisotope.

A major limitation on the supply of the short-lived medical isotope 90Y (t1/2 = 64 h) is the available quantity of highly purified 90Sr generator material. A radiochemical production campaign was therefore undertaken to purify 1,500 Ci of 90Sr that had been isolated from fission waste materials. A series of alkaline precipitation steps removed all detectable traces of 137Cs, alpha emitters, and uranium and transuranic elements. Technical obstacles such as the buildup of gas pressure generated upon mixing large quantities of acid with solid 90Sr carbonate were overcome through safety features incorporated into the custom-built equipment used for 90Sr purification. Methods are described for analyzing the chemical and radiochemical purity of the final product and for accurately determining by gravimetry the quantities of 90Sr immobilized on stainless steel filters for future use.     

Simultaneous measurement of 89Sr and 90Sr in aqueous samples by liquid scintillation counting using the spectrum unfolding method.

Two radiostrontium isotopes, 89Sr and 90Sr, were measured simultaneously by liquid scintillation counter coupling with a full spectrum DPM counting protocol. Strontium was separated from the aqueous media by extraction chromatography using Sr-spec resin. Individual count rates were evaluated from quench correlation curves for 89Sr and 90Sr related with SIS and tSIE quench indicators. The method exhibited a counting efficiency of 95% for 89Sr and 92% for 90Sr within their full energy channels and gave highly precise results when the sample was counted within 4 h after strontium separation. Lower limits of detection were 37 mBq/l for 90Sr and 32 mBq/l for 89Sr with a 60 min counting time.     

Combination of chemical separation and data treatment for 55 Fe, 63 Ni, 99 Tc, 137 Cs and 90 Sr/90Y activity determination in radioactive waste by liquid scintillation.

Routine operations involving nuclear reactors and decommissioning activities require numerous chemical analyses. Most of the procedures developed for these chemical characterisations involve several separation steps to prepare the sample for measurement. Chemical treatments are time- and manpower-consuming, labour intensive and produce significant quantities of waste. In order to address this problem, we evaluate a data treatment procedure (multivariate calibration--PLS), which we propose as a substitute to some of these separation steps. Mixtures of beta emitter radionuclides of increasing complexity ((90)Sr/(90)Y--(99)Tc, (90)Sr/(90)Y--(99)Tc--(63)Ni--(137)Cs and (90)Sr/(90)Y--(99)Tc--(63)Ni--(137)Cs--(55)Fe) have been measured by liquid scintillation (LS) counting. The influences of quenching and level of activity was evaluated and the activity of unknown samples determined. Despite the spectra overlapping and low resolution of LS, relative errors in the activities quantification of unknown samples inside the range covered by the calibration matrix are lower than 15% whatever the number of radionuclides included in the solution was.     

Activity measurements of the high-energy pure beta-emitters 89Sr and 90Y by the TDCR efficiency calculation technique.

The absolute activities of the pure beta-emitters 89Sr and 90Y have been determined by a direct method, namely the triple-to-double coincidence ratio (TDCR) efficiency calculation technique. This undertaking has extended further the number of radionuclides that have been standardized by this non-extrapolation liquid scintillation (LS) method. Both measurements were carried out within the framework of international key comparisons under the auspices of the International Bureau of Weights and Measures (BIPM). The TDCR results agreed well with those of other participating national laboratories, most using alternative (tracer) methods.     

Excitation functions for the production of 82Sr by proton bombardment of natRb at energies up to 100 MeV.

The excitation functions for the production of (82)Sr and other radionuclides produced in the proton bombardment of rubidium were measured by means of the activation technique. Stacks were assembled from RbCl targets, aluminium and copper monitor foils and bombarded with protons of energy up to 100 MeV and nominal current 0.1 microA. The measured data were compared with the theoretical calculations obtained by means of ALICE-IPPE, and also with previously published data. The measured data sets exhibit good agreement at incident energies below 45 MeV and greater than 60 MeV but show large discrepancies in the energy range between these values. The ALICE-IPPE calculations evidently overestimate all reported experimental cross sections, in particular overestimating the present data by a factor of 1.6. Notwithstanding the fact that there are discrepancies in the cross sections, good agreement is found with regards to the shape of the excitation function.     

Analytical calculations of the solid angles subtended by a well-type detector at point and extended circular sources.

Knowledge of the solid angle (and consequently, the geometrical efficiency) is essential in all absolute measurements of the strengths of radioactive materials and to calibrate detectors. The method of high-efficiency gamma counting by means of well-type HPGe and NaI (Tl) detectors is widely used and has proved a powerful tool, particularly when low-activity, small-volume environmental samples are to be analyzed by gamma-ray spectrometry. In the present work, we introduce a direct analytical method for calculating the solid angle subtended by a well-type detector at axial point, non-axial point, extended circular disk and cylindrical sources. The validity of the derived analytical expressions was successfully confirmed by the comparisons with some published data (experimental and Monte Carlo).     

Fatalities by inhalation of volcanic gas at Mt. Aso crater in Kumamoto,Japan

Volcanic gas is one of the hazards which tourists rarely meet in mountains. We present six fatalities due to volcanic gas inhalation on Mt. Aso, an active volcano in Kumamoto, Japan, over a period of nine years (1989-1997). One accident occurred at the lip of the crater and the other five within a distance of 250 m from the lip of the crater. Four of the six fatalities had a history of bronchial asthma. A forensic autopsy was performed for a fatality with a history of hypertensive heart disease; pulmonary emphysema was disclosed for this victim. These findings supported the idea that individuals with chronic lung diseases were at higher risk of death by volcanic gas inhalation. Safety precautions are effected through regular surveillance of the area and monitoring of volcanic gas levels. The criterion for sulfur dioxide levels has been changed to a more rigorous one (from >5.0 ppm to >0.2 ppm) according to our advice based on the autopsy. Further forensic analyses will help to design additional preventive measures so as to reduce mortality resulting from inhalation of toxic volcanic gas.     

Radioprotection and environmental pollution by the use of the radionuclides 89Sr, 186Re, and 153Sm for pain palliation in metastatic bone diseases. Related calculations

Due to the fact that the existing commercial analgesic drugs are not able to reduce effectively the pain caused by the metastatic bone disease, the use of radiopharmaceuticals with avidity to selectively localize in the metastatic skeletal sites, such as strondium-89 chloride (89Sr-Cl2), rhenium-186-hydroxy ethylene diphosphonate (186Re-HEDP), and samarium-153-ethylene diamine tetramethylene (153Sm-EDTMP), is widely accepted. However this medical application may be dangerous for the occupied personnel and more for general public, if radioactive waste is not properly disposed. In the following article we try to estimate the degree and the significance of that risk. For that reason we discuss the physical properties of these radionuclides and their distribution in the body of the patient. We conclude that 89Sr is not harmful for the physician, the attending personnel or those who live with the patient, because it radiates beta-radiation, while its gamma-radiation is negligeable. The radionuclides 186Re and 153Sm besides beta-radiation, also emit a perceptible amount of gamma-radiation. It has been shown that the exposure to gamma-radiation from these radionuclides of the physician, the attending personnel or those who live with the patient is very low as compared to the internationally accepted radioprotection limits. However the environmental contamination per treatment by either of these three radionuclides is not negligeable in comparison to the national and international accepted limits. Patients that are not in good clinical condition may pose an additional contamination danger to those attending them. For limiting radiocontamination, the annual number of treatments by the above three previous radionuclides, should be considered according to the ALARA principle in relation with the correct handling of these patients, and also considering the fundamentals of radioprotection.     

Nuclear data for production of the therapeutic radionuclides 32P, 64Cu, 67Cu, 89Sr, 90Y and 153Sm via the (n,p) reaction: evaluation of excitation function and its validation via integral cross-section measurement using a 14 MeV d(Be) neutron source.

Nuclear data for production of the therapeutic radionuclides 32P, 64Cu, 67Cu, 89Sr, 90Y and 153Sm via (n,p) reactions on the target nuclei 32S, 64Zn, 67Zn, 89Y, (90)Zr and 153Eu, respectively, are discussed. The available information on each excitation function was analysed. From the recommended data set for each reaction the average integrated cross section for a standard 14 MeV d(Be) neutron field was deduced. The spectrum-averaged cross section was also measured experimentally. A comparison of the integrated value with the integral measurement served to validate the excitation function within about 15%. A fast neutron source appears to be much more effective than a fission reactor for production of the above-mentioned radionuclides in a no-carrier-added form via the (n,p) process. In particular, the possibility of production of high specific activity 153Sm is discussed.