Yukio Kanda

Characterization of radiolytic products from air at a high-energy electron-positron storage ring

Abstract The measurements of radiolytic products have been made by irradiating the air using a flow-type reaction chamber with synchrotron radiation at the KEK TRISTAN electron-positron colliding ring. The products have been observed to be O 3 , NO 2 and N 2 O 5 in dry air and to be O 3 , NO 2 , HNO 2 and HNO 3 in moist air, and their relative production yields have also been estimated.

Particle size distribution of 7Be-aerosols formed in high energy accelerator tunnels

Abstract The 7Be, produced by nuclear spallation reactions in the air of high energy accelerator tunnels, is present in the form of an aerosol. The size distribution of the 7Be-aerosols was measured with a parallel plate diffusion battery and was found to be a log-normal distribution with a geometric mean radii of 27 nm and a logarithmic standard deviation of 0.36. The formation of the 7Be-aerosol is adequately explained by the attachment of 7Be to non-radioactive aerosols containing sulfates, which are produced by radiation induced oxidation reactions of SO2 present in the air.

Estimation of nickel-63 in steel and copper activated at high-energy accelerator facilities

Abstract 63Ni(β− decay; t 1 2 = 100.1 y ) is produced abundantly in stainless steel and copper hardware at high-energy accelerators. A measurement method using a liquid-scintillation counter has been developed. Its approximate activity could be estimated based on the thermal and fast-neutron fluxes measured by an activation method using gold and copper. After a few tens of years from beam-off, the existence of a no γ-radiation level from this accelerator hardware does not necessarily mean that all activity has decayed out, since there is still a possibility that an appreciable amount of 63Ni remains.

Radioactive airborne species formed in the tunnels of a high energy accelerator facility

Abstract By using a simple air filter technique, the fractions of aerosol and gaseous components were measured for individual nuclides formed in the air of a high energy accelerator tunnel. The size distributions for 7Be, 24Na and 38S aerosols were also measured by using a diffusion battery and found to be log-normal with a geometric mean radius of about 28 nm; the radioactive aerosol formation was adequately explained by simple attachment reactions.

Sequential multi-element analysis of sediments and soils by inductively-coupled plasma/atomic emission spectrometry with a computer-controlled rapid-scanning echelle monochromator

Abstract A computer-controlled rapid-scanning echelle monochromator is used to determine the major, minor and trace elements in reference sediments and soils. The high resolving power of the echelle spectrometer effectively decreases line overlap interferences, and permits a wide selection of analytical lines to be used. The concentrations of 17 elements in five standard materials are determined by using a single set of analytical lines without any corrections for line overlap interferences. Averages of relative standard deviations and relative deviations from the certified values for the 17 elements range from 2.4 to 4.3% and from 1 to 5%, respectively.

Development of CeF3 crystal for high-energy electromagnetic calorimetry

Abstract An R&D study has been performed to develop a long CeF3 crystal for electromagnetic calorimetry in high-energy physics. The successful growth of samples with good quality implies that application could be near.

Airborne gaseous 13N species and noxious gases produced at the 12 GeV proton synchrotron

The irradiation of atmospheric air with high-energy protons has been performed at the 12 GeV proton synchrotron. The specific activity of 13N, one of the principal airborne radioactivities, was measured as a function of the irradiation time at a dose rate of about 6·1016 eV/g/s, and compared with the calculated values. The predominant chemical species of 13N produced were found to be 13N2and 13NO2. Their proportions were approximately 55% for 13N2 and 45% for13NO2, being almost independent of the irradiation time. Smaller quantities of 13NO and H13NO2 were also observed. Measurements of radiolytic products showed that ozone is a main product and that NO2predominates among the products of nitrogen compounds, including HNO2 and HNO3. The G-value for ozone formation in air was estimated from the experimental data as 6.4 molecules/100 eV.

Simultaneous determination of atmospheric nitric acid and nitrous acid by reduction with hydrazine and ascorbic acid with chemiluminescence detection

A continuous-flow system for the simultaneous determination of atmospheric HNO3 and HNO2 has been developed that consists of two sets of dual-channel flow systems: one is for the measurement of total HNO3—HNO2 and the other is for the measurement of HNO2. Nitric acid and HNO2 are continuously stripped from the atmosphere into an NaOH solution by drawing the air sample and the solution through a glass coil. The nitrate is reduced with hydrazine sulfate in the presence of Cu11 to nitrite, which is then reduced to NO with ascorbic acid solution, and the NO is detected by a chemiluminescence NOx analyser. This measurement system can also be used to determine HNO2, thus giving the total concentration of HNO3 and HNO2. The measurement system without the hydrazine reduction procedure determines HNO2 alone. The concentration of HNO3 is determined by the difference between the two measurements. Of the common pollutants, NO2 and peroxyacetyl nitrate showed positive interferences. In order to correct for these positive interferences, each of the measurement systems utilizes a dual flow system and a dual-channel NOx analyser.

Study of particle size distribution and formation mechanism of radioactive aerosols generated in high-energy neutron fields

The size distributions of 38Cl, 39Cl, 82Br and 84Br aerosols generated by irradiations of argon and krypton gases containing di-octyl phthalate (DOP) aerosols with 45 MeV and 65 MeV quasi-monoenergetic neutrons were measured in order to study the formation mechanism of radioactive particles in high energy radiation fields. The effects of the size distribution of the radioactive aerosols on the size of the added DOP aerosols, the energy of the neutrons and the kinds of nuclides were studied. The observed size distributions of the radioactive particles were explained by attachment of the radioactive atoms generated by the neutron-induced reactions to the DOP aerosols.

Particle size analysis of radioactive aerosols formed by irradiation of argon using 65 MeV quasi-monoenergetic neutrons.

The size distributions of 38Cl and 39Cl aerosols formed from the irradiation of argon gas containing di-octyl phthalate (DOP) aerosols by 65 MeV quasi-monoenergetic neutrons were measured to study the formation mechanism of radioactive aerosols in high-energy radiation fields. Both the number size distribution and the activity-weighted size distribution were measured using an electrical low-pressure impactor. It was found that the 35Cl and 39Cl aerosols are formed by attachment of the radioactive atoms generated by the neutron-induced reaction to the DOP aerosol particles.