It is very important in a nuclear air cleaning system that HEPA (High Efficiency Particulate Air) filter is for reduction of releasing amounts of airborne radioactive particles. HEPA filter, by definition, has a minimum collection efficiency of 99.97% for 0.3μm particles. However, DF (Decontamination Factor), which is necessary for safety management, can not be directly derived from the efficiency. And the current standard defined for 0.3μm particles has no scientific justification, because it has been found that the most penetrating particle size through HEPA filter is not always 0.3μm. In the present paper, a numerical experiment was made in order to estimate a relationship between DF and the efficiency. And new standard, in which the minimum DF is able to be easily obtained, was proposed. In the multistage filtration system, it was found that lower values of DF was possible to be experimentally indicated in the second and the third stages, even if the collection performance of the each filter is the same.
The effects of intravenously injected DTPA (diethylenetriaminepentaacetic acid) to the cardiovascular system were examined pharmacologically in rats. When Zn-DTPA of the various doses (30-900μmol/kg) were injected intravenously to rats, the concentrations of total calcium, ionic calcium in serum decreased significantly 5min after the injection. This hypocalcemia continued 30min later. Correspond to the decreasing rates of total calcium and ionic calcium, the blood pressures raised significantly at 600μmol/kg dose, as compared to those of control group. The heart failure showing the prolong of Q-T wave in the electrocardiogram and the decreases of heart rates and weakened strokes were observed at 900μmol/kg dose, these changes were emphasized at 1, 200μmol/kg dose. On the other hand, no untoward findings were seen by Ca-DTPA injection. As a result, in the case that DTPA was injected intravenously to humans, it appeared that Zn-DTPA was more toxic than Ca-DTPA to cardiovascular system and then induced the damages of cardiovascular system such as the heart failure. Therefore, it should be prepared the available information on the blood pressure and heart diseases of radiation workers obtained from the medical checkup at regular intervals, providing for DTPA intravenous injection to humans.
From the viewpoint of radiation protection, the remaining amounts of radioactive pharmaceutical 133Xe in a gas container, the influence of aging time of a silicone tube of a gas dispenser on the remaining radioactivity and decrease of radioactivity in a container with elapse time were investigated experimentaly. The formulas to calculate the residual radioactivity in a container were obtained by A (X≤80)=100-1.11×X and A (X>80)=8.44×(0.988), where A and X stand for the percentage of the remnant and the total running time (second) of the gas dispenser respectively. The silicone tubes used several times have little practical influence on the remnant and the residual radioactivity decrease with elapse time as if the half time were 4. 88 days, which was shorter than physical half life of 133Xe, 5.25 days. It was considered the shortening of half time was caused by the leakage of radioactivity from the gas container of about 1 percent a day. From these results, it was concluded that the maximum residual radioactivity in the gas container was 7-12 percents of initial radioactivity in the case of the total running time of 80sec or so and the gas containers as radioactive waste should be disposed after waiting for more than 60 days.
This paper deals with the X-radiation from television receivers and video display terminals. The bremsstrahlung production rate was calculated according to the thick target theory, and the transmitted X-radiation was measured by the spectrometry method. The calculated and the measured results were compared and discussed. In addition, evidences were shown that only the highest energy component of the bremsstrahlung can penetrate the cathode ray tube.