A new method for estimating the numerical value of the first hydrolysis constant of tetravalent plutonium is illustrated by
examples. It uses the pH and the equilibrium fractions of two of the Pu oxidation states. They are substituted into one or
more of a choice of formulas that render explicit estimates of the hydrolysis constant.
The stochastic processes of activation, disintegration and counting have been studied, taking into account reactor noise. Deviation of the variance of the number of counts from Poisson limit is shown to result. Explicit expressions for the variance in the case of Markovian autocorrelation function of the neutron flux density are presented and their relevance to neutron activation analysis is discussed.
Gamma-ray treatment in the presence of ozone (O3) and titanium dioxide (TiO2) showed an efficient removal of trichloroethylene (TCE) and perchloroethylene (PCE). Without gamma-irradiation, TCE and PCE were not sufficiently decomposed to comply with the water quality limit of groundwater. However, near 100% of TCE and PCE were removed at a dose of 300 Gy in the presence of O3 and TiO2, where TiO2 showed an explicit enhancement of decomposition. Cytotoxicity test using Chinese hamster V79 cells showed no toxicity of the TCE and PCE decomposition products.
Radionuclide identification from a measured gamma-spectrum is an iterative process, where the analyst aims to find correct nuclides by decreasing the amount of possibilities by trial and error. Although the process of identification is quite complex, it can be formulated using rules of thumb combined with exact mathematical analysis. Thus, an expert system can be built, where the knowledge of a human expert is converted to explicit rules. In this paper expert system SHAMAN is presented, which carriess out the qualitative nuclide identification and activity determination with minimum of user intervention. The reasoning process is performed by an inference engine written in C-language. The system uses a database containing over 2000 radionuclides with about 48 000 gamma-transitions. Spectra are provided in preprocessed format, where peak energies, intensities and backgoounds with respective error estimates have been calculated by a separate analysis program.
Kinetics and concentration profile associated with the regulated radiodegradation of bilirubin in an organic solvent were
assessed. The pure unconjugated specimen was prepared in chloroform (40.0 µM). The depletion of bilirubin was almost linear
with dose, and complete degradation was accomplished with doses in excess of 100 Gy. The method was also evaluated for the
explicit production of the long-wavelength isomer of biliverdin, which was characterized spectrometrically by an absorbance
band in the region 600–650 nm. Results including differences in air, N2 and O2 purged samples are presented to identify the atmospheric medium for optimum production of biliverdin. The process was regulated
by controlling the dose. The general rate constant of the depletion process was estimated at a dose rate of 5.67·10−2Gy·s−1. The method is a convenient substitute for light illumination studies of bilirubin.
The non-destructive methods of thermal and epithermal neutron activation analysis have been employed to determine the aluminum concentration of seven National Institute of Standards and Technology certified biological reference materials. Through the judicious use of both thermal and epithermal neutron activation analysis using bare and boron-lined irradiation carriers, the major and minor contributions of the31P/n, /28Al and of the28Si/n, p/28Al reactions, respectively, to the27Al/n, /28Al reaction could be corrected for explicitly. Based on replicate determinations precision of the analysis ranged from 2.5% for citrus leaves determined at the 75 ppm level to 18% for bovine liver measured at the 1 ppm level. Accuracy was demonstrated whenever possible by comparison to existing published data.
A theory of the evaluation of kinetic parameters of induction periods for non-isothermal processes is outlined and a method
to obtain the parameters from non-isothermal differential scanning calorimetry measurements, based on the dependence of onset
temperature of oxidation peak on heating rate, is presented. The applicability of the method is demonstrated on the study
of oxidation induction periods of edible oils and polyolefines. In all cases, the parameters of an Arrhenius-like equation
describing the temperature dependence of induction period have been obtained. It is shown that the method gives the parameters
not affected by oxygen diffusion which are transferable to be used in modelling the non-isothermal induction periods where
the effects of diffusion, heat transfer and evolution of reaction heat are explicitly involved. A method of estimating the
residual stability after a thermooxidative stress of the material is suggested.
Authors:S. Changlai, H. Tsai, S. Tsai, H. Chen, C. Chang, Y. Yao, and C. Chen
This work is the first evaluation of environmental gamma exposure rates by the Nuclear Medicine Department at Lin Shin Hospital
(LSH) in Taichung with Thermoluminescent dosimeter (TLD-100H) during the Fukushima Nuclear Power Plant (FNPP) accident. After
the 9.0 MW strong earthquake hit northern Japan on March 11, 2011, a TLD-100H was used to monitor environmental kerma rate at Taichung
(2,500 km away from northern Japan) from Mar-08 to Apr-09, 2011 and evaluated kerma rate due to global fallout of the sever
FNPP accidents. Exposure rates varied widely among positions close to the PET/CT facility. Observed kerma rates of up to 4.12 ± 0.62 mSv mo−1 indicated an explicit, heavy leakage of photon through the PET/CT facility. No significant contributions were detected at
Taichung, Taiwan. Hence, the health effect cause by the “extra radiation” from FNPP accidents is negligible. As this was a
rare case of environmental monitoring during a nuclear power plant accident, its findings are of considerable significance.
A variety of isoconversional and model fitting approaches, all of which use multiple heating schedules, are used to analyze
selected data from the ICTAC kinetics and lifetime projects as well as additional simulated data sets created for this work.
The objective is to compare the accuracy and suitability of various approaches for various types of chemical reactions. The
various simulated data sets show that model fitting and isoconversional methods have comparable reliability for extrapolation
outside the range of calibration. First, there is as much variability in prediction for various isoconversional methods as
there is between isoconversional methods as a group and different plausible explicit models. Of the three isoconversional
models investigated, the Friedman method is usually the most accurate. This is particularly true for energetic materials that
have a drop in apparent activation energy in the latter stages of reaction, which leads to a delayed onset of rapid autocatalysis
at lower temperatures. It is difficult to determine a priori whether isoconversional or model fitting approaches will give
more accurate predictions. The greatest reliability is attained by using both the isoconversional and model fitting approaches
on a combination of isothermal and constant heating rate data.
The fission yields of 38 fission products in the fast-neutron induced fission of238U have been determined using a rapid, multiscaling gamma-ray spectroscopic method. To obtain absolute yields for fission products having half-lives ranging from 32 s to 40 d, a total of 56 multi-scaling gamma-ray spectra were collected using various irradiation and cooling periods. Gamma-rays and photopeak areas of interest were assigned to the fission products by their energies and half-lives. Fission product activities were evaluated from spectral data using growth and decay calculations and fission yields were determined by normalizing the140Ba yield to the average value from reported data. The depleted uranium target, covered with a boron-cadmium thermal neutron shield, was used to keep interference from the fission of235U minimal. Results for the cumulative fission yields, including 17 mostly short-lived fission products measured for the first time, are compared with previous measurements and with the recommended yields in recent evaluations. The agreement, and some discrepancies, in the comparisons are discussed. No explicit even-odd pairing effects are observed in the fission yield data for fast-neutron induced fission of238U.