A method was developed for the rapid dissolution of plutonium in soil by fusion with ammonium hydrogen sulfate, and the determination of plutonium content by ion exchange separation and alpha spectrometry. By this method, plutonium in environmental soil containing plutonium oxide in a soluble and/or insoluble form could successfully be determined.
A radiological survey and whole body counting of 137Cs were carried out in Rongelap Island (main island) of Rongelap Atoll in July 1999. The maximum values of 137Cs contamination and of g-ray dose rate were 39 kBq/m2 and 0.033 mSv/h, respectively. The maximum a and b gross counting rates on the surface of ground were 1 cpm and 182 cpm in active area of 72 cm2, respectively. Activity of 239,240Pu for soil was 80 Bq/kg in the top 5 cm and aerial deposition was 3.4 kBq/m2 in Rongelap Island in 1999. The body burden of 137Cs was observed to be 27±11 Bq/kg for 6 workers. Assessment of external and internal annual doses (0.1 and 0.07 mSv/y) indicates that as of 1999 there is no large risk to the inhabitants of Rongelap Island from a radiological point of view. The radiological status of Rongelap Island, which was severely contaminated by the radiological fallouts of nuclear testings carried out in 1954, has improved year by year as shown by the decrease of 137Cs. The effective halftime of 137Cs, which is estimated to be 6.6 y is much shorter than the physical half-life of 137Cs. Radioactive contamination in Kaballe Island, (a part of the northern islands used for farming) which is located 25 km northeast of Rongelap Island, was still high in 1999. One site nearby a beach was highly contaminated with 137Cs, where the maximum activity of 137Cs was 3.4 MBq/m2, a-ray of 2 cpm, b-ray of 1205 cpm and g-ray of 0.73 mSv/h. Activity of 239,240Pu in soil (n = 1) was 294 Bq/kg (top 5 cm) and 16 kBq/m2.
Thorium-232 and238U contents in four food groups were measured by inductively coupled plasma mass spectrometry (ICP-MS). Daily intakes of232Th and238U for Japanese were estimated to 2.22 mBq and 15.5 mBq per person, respectively. Furthermore, preliminary estimations were made for the effects of imported foods on internal exposures for Japanese.
Low-energy photon spectrometry with -spectrometry was used to determine the environmental concentrations of low-level actinides and other nuclides, especially210Pb and210Po. The isotopic ratio of240Pu/239Pu was successfully determined by measuring Lx-ray/-ray counting ratio. A reliable method has been developed for the determination of extremely low-level237Np global fallout in environmental samples. The non-destructive determination by Ge-LEPS for natural210Pb in various samples (tobacco leaves, commercially available tobacco, etc.) was also carried out with the determination of210Po by -spectrometry using209Po as a yield tracer.
An analytical method was developed for the measurement of low-level 54Mn in soil sample by ultra low-background g-ray spectrometry after radiochemical separation. The method consists of decomposition of sample by a mixture of HNO3 and HF, dissolution by HNO3, precipitation as hydroxide, solvent extraction with diisopropyl ether and anion exchange. Finally, for purification of Mn it was precipitated as MnO2 by adding KClO3. 54Mn in the precipitate was measured by ultra low-background well-type Ge detector at Ogoya Underground Laboratory. Measurements of 54Mn using 30-200 g of soil samples from the JCO grounds were successfully performed by the present method. The minimum detectable activity of 54Mn was about 0.01 dpm (0.2 mBq) for a 7-day counting period.
Mixed-valence μ-phenolate-bis(μ-carboxylate) diiron(II, III) complex [Fe2(bpmp)(ppa)2](BF4)2 (1) is prepared. The temperature dependence of the Mössbauer spectra of the complex 1 is measured. The Mössbauer parameters of the complex 1 show the unusual increase of isomer shift and quadrupole splitting with an increase in temperature. The spectra are explained
by the dynamic electronic states in which the valence states of two iron atoms in a molecule are 2.2 and 2.8 on the Mössbauer
time scale at 293 K. The single crystal X-ray structure of the complex 1 is determined at 133 K. The complex 1 crystallizes in the triclinic space group
Hokutolite, and hot spring water and river water collected recently at Peitou Hot Spring in Taiwan were analyzed for U, Th,
Ra and 210Pb isotopes. Concentrations of major chemical elements were also measured. Hokutolite had its typical chemical composition
make-up for this area. The concentrations of 238U, 234U, 232 Th, 230 Th, 228 Th, 226Ra, 228Ra and 210Pb in samples scrapped into 7 layers from the surface to the bottom of a hokutolite specimen were 0.0021-0.0068, 0.0022-0.0075,
1.47-2.07, 1.00-1.29, 1.56-1.97, 56.7-68.6, 1.46-2.06 and 25.9-36.0 Bq/g, respectively. All the radionuclides exhibited a
relatively uniform distribution, and radioequilibrium was confirmed among 232 Th, 228Ra and 228 Th. From the relationship between the decay and growth of Th-series nuclides it was considered that the hokutolite studied
was isolated from the stream water at least 70-80 years ago. The U/Th-series radionuclides in the hot spring water were in
rather high concentrations and the enrichment of 228Ra and 228 Th to 232 Th was the most prominent feature. Evaluation of the distribution coefficients (Kd) using the data on hot spring water or river water and hokutolite indicated that Th (Kd = 104-105) in water was likely to be precipitated (and/or co-precipitated) with BaSO4 as Th(SO4)2 with a relatively high concentration into hokutolite, together with Ra (Kd = 106-107).
Neptunium is sorbed, together with plutonium, uranium and iron on Bio Rad AG 1×4 anion exchange resin from 9 mol/1 HCl, eluted with 7 mol/l HNO3 and 1.2 mol/l HCl, purified on a second, identical column and electrodeposited on stainless steel discs.237Np is determined by -spectrometry,239Np by -spectrometry with a Ge detector, or via its 14.3 keV LX-rays in a Si(Li) measurement. The neptunium yield is determined from the count rate of the 13.6 keV LX rays of the tracer235Np in a later Si(Li) measurement. The average chemical yield is 78±11%. The detection limit for237Np is 1 mBq. The procedure allows the sequential determination of neptunium, together with plutonium, strontium, uranium and iron from one sample. The method was applied to air and total deposition samples from Munich-Neuherberg and to sediment samples from the Irish sea.
A multiple-site competitive model has been developed to evaluate quantitatively the equilibrium competition of drugs that bind to multiple classes of binding sites on human serum albumin (HSA). The equations, which are based on the multiple-class binding site model, assume that competition exists at individual sites, that the binding parameters for drug or drug competitor pertain to individual sites, and also that the binding parameters for drug or competitor at any given site are independent of drug or competitor bound at other sites. For the drug-competitor pairs, ethacrynic acid (EA) -caproic acid (C6), -lauric acid (C12), and -palmitic acid (C16), the reaction heat of EA binding to HSA was measured in the absence and the presence of fatty acids at the molar ratio of 3:1 with HSA at pH 7.4 and 37°C by isothermal titration microcalorimetry. The calorimetric titration data induced by the presence of fatty acids were directly compaired to the computer simulation curves by the corresponding multiple-site competititve models, which were precedently calculated from binding parameters of EA and fatty acids. In the case of EA-C12 or -C16 competitive binding, EA binding at the first and the second classes of binding sites on HSA were instantaneously inhibited by C12 or C16, resulting that the binding constant of the first class of binding sites of EA were decreased and that the second class of binding sites on HSA entirely disappeared. In the competition between EA and C6, the first class of binding sites of EA was diminished by C6, resulting in the decrease of the binding constants and the number of binding sites in the first class of EA, whereas, the second class of binding sites was unaffected. The multiple-site competitive model assuming site-site competition could be directly comparable to the calorimetric data and be suitable to account for the competitive processes for drugs bound to the multiple-class of binding sites on HSA.
Authors:M. Takeyasu, T. Iida, H. Watanabe, M. Takeishi, and A. Yamamoto
The performance of the computer code system, SIERRA-II, for calculating the environmental radiation dose due to an accident
was assessed over a coastal area, using the environmental monitoring data around the coastally located Tokai Reprocessing
Plant (TRP) when 85Kr was discharged during its operation. The agreement within a factor of 5 between the calculated and observed air concentrations
of 85Kr in areas of a few km from the TRP was achieved in 57% of the comparison data, disregarding the internal boundary layer.
The mean fraction bias was −0.6, which meant a slight overestimation. According to the vertical profile of the atmospheric
temperatures, the internal boundary layer was modeled with the SIERRA-II and the agreement became better than when the internal
boundary layer was not considered.