In order to clarify both the effect of tritium (3H or T) on the ecosystem and the reactivity of materials having H atoms, the reactivity of L-cysteic acid (or L-cysteine) having three different kinds of functional groups was studied. The hydrogen-isotope exchange reaction between each compound and HTO vapor (T-for-H exchange reaction) was observed at 50-70°C, and the reaction was analyzed with both the A″-McKay plot method and the data obtained from the exchange reaction. The following seven matters have been consequently found in the T-for-H exchange reaction. (1) The reactivity of the functional groups in each compound increases with increasing temperature. (2) As to L-cysteic acid, the reactivity of SO3H group is 2.6 times greater than that of COOH one, and is 5.6 times greater than that of NH2one. (3) As to L-cysteine, the reactivity of SH group is 1.4 times greater than that of COOH one, and 3.5 times greater than that of NH2one. (4) The reactivity of NH2group progressed by the substituent having large electron-attractive effect, however, the reactivity of COOH group does not so progress by such a substituent. (5) Applying the A″-McKay plot method, the reactivity of the three functional groups in each aliphatic compound can be nondestructively and simultaneously clarified under the condition of non-masking reagent. (6) Degree of T-incorporation in a certain material can be nondestructively and quantitatively clarified. (7) The results obtained in this work is useful to prevent T contamination in the environment and to clarify the reactivity of the materials having plural functional groups, and the method used in this work can be also useful as a analytical method to obtain the reactivity of multi-functional groups in a certain compound.
From the standpoint of radiological protection and diagnostic procedures, dose evaluation of the urinary bladder is important since the radionuclides entered the body are partially excreted by urine. As the absorbed dose for the radiosensitive cells reflects the radiation risks, the present study has evaluated the photon and electron SAFs for the basal cells-radiosensitive cells-in the bladder wall as well as the bladder wall surface using a Monte Carlo code. S values were also evaluated for nine radionuclides : 11C 13N, 15O 18F 89Sr, 90Sr, 90Y, 99mTc and123I. Consequently, the photon SAFs for basal cell layers in the energy range 10-30 keV are significantly larger than those of the whole bladder wall. The electron SAFs in all cases increase with the electron energy in the range 10 keV-4 MeV. As for S values, the discrepancy was observed between the result of this study and conventional values, particularly in low energy region. These results demonstrate that determining the depth of radiosensitive cells is necessary for realistic dose evaluation.
Time interval analysis (TIA), which is one type of delayed coincidence method, was applied to214Bi-214Po correlated events with a microsecond scale (214Po half-life: 164μs) . A measurement system with a silicon semiconductor detector was constructed in combination with a special time recording device and a personal computer. This system was designed to shorten dead time. The basic performance of this system was examined using an electrodeposited230Th source and actual dust samples. The measurement data for the time intervals of neighboring pulses were analyzed by a single time interval analysis (STA) . The following results were obtained. (1) The214Bi-214Po correlated events, which are included in Rn-progeny, were used for sensitive measurement by the TIA method. (2) Theories for214Po mmeasurement using the TIA method were established. (3) The measurement system for214Po was developed. (4) Efficiency and detection limit of measurement system were discussed through the experiment with an electrodeposited230Th source and dust samples. The present method is applicable to on-line monitoring of a-ray measurements, because the TIA method is able to detect any artificial a-decay radionuclides by compensating for disturbance due to Rn progenies.