Nagao Ikeda

Determination of technetium-99 in environmental samples by inductively coupled plasma mass spectrometry

Abstract A new analytical technique using inductively coupled plasma mass spectrometry (ICP-MS) was applied to the determination of 99Tc in some environmental samples. The accuracy and precision of the new method were assessed by comparison with those of the liquid scintillation counting method. The results obtained by ICP-MS were in good agreement with those by liquid scintillation counting at a relative deviation of 3%. The detection limit is 1.1 mBq/mL (1.73 pg/mL).

Determination of237Np in environmental samples using inductively coupled plasma mass spectrometry

A new analytical technique using ICP-MS was applied to the determination of237Np in some environmental samples. The accuracy and precision of the new method were assessed by comparison with those of conventional NAA and α-spectrometric method as well as by analysis of the intercomparison sample of Ravenglass NRPB silt. The results obtained by ICP-MS were in good agreement with those by NAA or α-spectrometry at a relative deviation of 2–9%. The detection limit is 0.02 mBq/ml (26 mBq=1 ng).

Measurement of240Pu/239Pu ratio by fission track method and inductively coupled plasma mass spectrometry

Fission track /FT/ method and inductively coupled plasma mass spectrometry /ICP-MS/, that is a new analytical technique for the analysis of trace element, were used for the measurement of240Pu/239Pu ratios in environmental samples. The results obtained by both methods are in agreement within the relative deviation of 9–13%. The precision in ICP-MS was found to be better than in it the FT-method. These methods are applicable to measure the Pu isotopes ratio at low concentration levels in environmental samples.

Determination of U in Japanese human tissues by the fission track method.

Uranium in several human tissues (lung, liver, kidney, muscle, spleen, heart, cerebrum and bones) from Japanese in the Tokyo area was determined by the fission track method. The average U content was the highest in lung with 1.70 ppb wet, and decreased in the order of lung greater than bones greater than heart and muscle greater than kidney greater than liver and spleen, showing markedly different tendencies from the description in the 1982 UNSCEAR Report (UNSCEAR82). Correlations were observed between U content in lung and in other tissues. These data suggest that the contribution of inhalation of U to its total intake is not negligible. The total body burden of U for the ICRP Reference Man (ICRP74) was estimated to be about 40 micrograms, which is rather small compared with the average normal burden of 90 micrograms currently accepted by the International Commission on Radiological Protection (ICRP79).

Distribution and behavior of long-lived radioiodine in soil

The concentration of129I in soil in Japan was determined by neutron activation analysis. For the activation analysis, pre-irradiation chemical separation of the iodine was carried out by acid decomposition and distillation and post-irradiation treatment was performed by ion exchange and solvent extraction. The concentration of stable iodine and137Cs were also determined and compared with the behavior of129I in soil.Soil samples from Ibaraki, Fukui, Fukushima, and Nagasaki Prefectures were analyzed and129I was detected in amounts ranging from 10−7 to 10−5 Bq/g soil in uncultivated surface soil. There are apparently small variations in the129I concentrations in each of the regions analyzed.From depth profile studies in sandy soil, the iodide form of129I was found to migrate downward at a relatively rapid rate while other species remain longer in the surface soil.

Distribution and behaviour of99Tc,237Np,239,240Pu, and241Am in the coastal and estuarine sediments of the Irish Sea

Intertidal coastal and estuarine sediments from 24 sites in the Irish Sea have been analyzed for99Tc,237Np,238Pu,239,240Pu and241Am. The237Np activity and239Pu/240Pu ratio were measured simultaneously by ICP-MS, and99Tc was determined by HR-ICP-MS which is ten times more sensitive than Q-ICP-MS.The activities of99Tc,237Np,239,240Pu and241Am were distributed over a wide range of 1.5–70.5, 0.01–13.3, 2.3–1589, 2.6–1894 Bq/kg, respectively. Activities of these radionuclides decreased exponentially with distance from the Sellafield source. The241Am/239,240Pu and237Np/239,240Pu ratios were almost constant with distance from the Sellafield. This result suggests that the distribution and behavior of Np and Pu are controlled by complicated factors such as the influence of transport, the variation with time of Np/Pu ratio in the Sellafield discharges and sedimentary mixing processes in the Irish Sea.

Particle-size distribution of fission products in airborne dust collected at Tsukuba from April to June 1986

Abstract The radioactivity released by the reactor accident at Chernobyl was detected in surface air at Tsukuba, Japan. Gamma-spectrometry of airborne dust collected using aerodynamic separation showed higher concentrations of radionuclides in fine particles. The particle-size distribution of radionuclides changed with time.

Activation analysis for technetium-99 by the use of a neutron-excitation reaction

The formation of99mTc was observed when99Tc was irradiated by reactor neutrons as a result of the99Tc(n, ń)99mTc reaction. A good linearity was observed between the activities of99mTc produced and99Tc irradiated. The cross section of the excitation reaction was estimated to be 0.24 b. The application of the nuclear excitation reaction to the activation analysis for low level99Tc was studied.

Determination of radioiodine species in rain water collected at Tsukuba near Tokyo

Abstract The distribution of radioiodine ( 131 I) species in rain water collected at Tsukuba in May 1986 was studied using the isotopic exchange method. Organic-soluble forms of radioiodine were not observed. Iodide (I ∗− ) was the predominant species, and the concentration of iodate (I ∗ O 3 − ) was less than half of I ∗− . The results were compared with those for 131 I produced by neutron-irradiation of uranyl nitrate.

フィッショントラック法による人歯, 人骨, 組織中のウランの定量

The uranium content of several human tooth, bone and soft tissue samples was determined by the fission tract method. The average uranium content in teeth, bones and soft tissues were 6.7, 8.4 and 64 ppb ash, respectively. The distribution of uranium in bones is less uniform than that of teeth, and the uranium content of soft tissues is generally higher than that of teeth and bone. The presence of thorium does not interfere with the uranium determination in most cases.