Search

Heterogeneous clusters of cancer cells and leukocytes in blood were visualized by combining high-throughput and high-sensitivity fluorescence imaging flow cytometry with 5-aminolevulinic acid stimulation.

To establish systematic guidelines for accelerator decommissioning, a large-scale activation survey was conducted at representative synchrotron radiation facilities in Japan. The neutron flux during accelerator operation was measured with various dosimeters. A Monte Carlo simulation was conducted for some facilities to verify the special neutron distribution and their spectra. Beam loss points, reflected as high-dose-rate areas, were identified by a whole-beamline survey with a survey meter, and the generated radionuclides and their activity were determined with a lanthanum bromide (LaBr3) scintillation spectrometer. In all facilities, the activation level was quite low. Whole-beamline tunnels made of concrete were not activated, and no radionuclides were detected except for natural nuclides. In addition, almost all beamline components were either not or minimally activated. Although the acceleration energy is very high for radiation synchrotron facilities, the generation of radioactive waste would be very low.

Typically, the concentrations of cobalt and europium, which are trace elements in concrete, are difficult to determine by chemical analysis. While data sheets do not usually contain this information, it is important for the decommissioning of accelerators, especially for the decontamination of activated concrete. To understand the variations in trace element concentrations in concrete, we analyzed cobalt and europium concentrations in concrete samples from accelerator facilities in Japan by neutron activation analysis, which is suitable for trace element analysis on the order of parts per million (ppm).

O-GlcNAcylation is the only sugar modification for proteins present in the cytoplasm and nucleus and is thought to be involved in the regulation of protein function and localization. Currently, several methods are known for detecting O-GlcNAcylated proteins using monoclonal antibodies or wheat germ agglutinin, but these methods have some limitations in their sensitivity and quantitative comparison. We developed a new disaccharide-tag method to overcome these problems. This is a method in which a soluble GalNAc transferase is expressed intracellularly, extended to a disaccharide of GalNAc-GlcNAc, and detected using a Wisteria japonica agglutinin specific to this disaccharide. We verified the method using human c-Rel protein and also highly sensitively compared the difference in O-GlcNAc modification of intracellular proteins associated with differentiation from embryonic stem cell (ESC) to epiblast-like cells (EpiLC). As one example of such a modification, a novel O-GlcNAc modification was found in the transcription factor Sox2 at residue Ser263, and the modification site could be identified by nano liquid chromatography-mass spectrometry.

The role of valence electrons for the muon capture process by molecules is experimentally investigated with the aid of cascade calculations. Low-momentum muons are introduced to gas targets of CO, CO2, and COS below atmospheric pressure. The initial states of captured muons are determined from the measured muonic X-ray structure of the Lyman and Balmer series. We propose that the lone pair electrons in the carbon atom of CO significantly contribute to the capture of a muon with large angular momenta.

Per-atom muon capture ratios are precisely determined from characteristic muonic X-ray measurements of three nitrogen oxide samples (NO, N2O, and NO2) at pressures below 100 kPa. A higher density of covalent electrons at the N atoms relative to the O atoms is required if we explain the experimental results using the proposed muon capture models. From molecular orbit calculations, we found that the electron distributions of only the highest occupied molecular orbitals (HOMO) are dominant at the N atoms, and the electrons in the HOMO significantly contribute to the muon capture phenomena in the nitrogen oxide molecules.

Many growth factors, such as fibroblast growth factors (FGFs), are useful for the treatment or prevention of radiation damage after radiation therapy. Although heparin can be supplemented to increase the therapeutic effects of FGFs, it possesses strong anticoagulant effects, which limit its potential for clinical use. Therefore, chemically sulfated hyaluronic acid (HA) was developed as a safe alternative to heparin. This study examined the involvement of sulfated HA in radioprotective and anticoagulant effects.FGF1 was administered intraperitoneally to BALB/c mice with sulfated HA 24 hours before or after total body irradiation with γ-rays. Several radioprotective effects were examined in the jejunum. The blood coagulation time in the presence of sulfated HA was measured using murine whole blood.FGF1 with high-sulfated HA (HA-HS) exhibited almost the same level of in vitro mitogenic activity as heparin, whereas FGF1 with HA or low-sulfated HA exhibited almost no mitogenic activity. Furthermore, HA-HS had high binding capability with FGF1. FGF1 with HA-HS significantly promoted crypt survival to the same level as heparin after total body irradiation and reduced radiation-induced apoptosis in crypt cells. Moreover, pretreatment of HA-HS without FGF1 also increased crypt survival and reduced apoptosis. Crypt survival with FGF1 in the presence of HA depended on the extent of sulfation of HA. Moreover, the blood anticoagulant effects of sulfated HA were weaker than those of heparin. As sulfated HA did not promote the reactivity of antithrombin III to thrombin, it did not increase anticoagulative effects to the same extent as heparin.This study suggested that HA-HS promotes the radioprotective effects of FGF1 without anticoagulant effects. HA-HS has great potential for practical use to promote tissue regeneration after radiation damage.

Three methods to detect neutrons emitted from an electrostatic accelerator were examined. These were gold foil activation, thermoluminescent dosimeters (TLDs), and CR-39. The gold-foil activation method has previously been proven effective in the measurement of neutrons emitted from cyclotron sources. In the case of electrostatic accelerators, a greater amount of fast neutrons and a smaller amount of thermal neutrons are observed compared to a cyclotron accelerator. Therefore, the error in calculating the thermal neutron flux became unacceptably large. By comparison the CR-39 detectors were apparently unable to measure thermal neutrons well, because some tracks were also generated by fast neutrons causing a signal interference. In the case of TLDs, as the material was not sensitive to fast neutrons, it was not affected by them, and hence could adequately measure the thermal neutron flux. However, it was found that in some cases its measurements could be offset by the influence of high dose rate of gamma rays.

Accelerator operations often generate neutrons that may activate concrete in the accelerator room. When accelerators are decommissioned, the concrete will remain as radioactive waste. Not all of concrete in the room will be radioactive wastes, but at place with large amount of neutrons will be radioactive wastes. Therefore, it is very important to determine where and how many neutrons are generated during accelerator operation. We used gold foils to obtain this information in positron emission tomography (PET) cyclotron facilities. We obtained concrete core samples from a PET cyclotron to determine the amount of radioactivity contained in concrete. We obtained the operational parameters (particle, radioactive product, current, and operation time) of the PET cyclotron facility and estimated the radioactivity generated in concrete using the operational parameters and gold foil results. A comparison of the estimated and core sampling measurement results showed good agreement.

Activated accelerator magnets were measured with three different types of commercially available gamma-ray imaging devices (pinhole, Compton scattering, and masked type) and the results were compared to simplify a distinction between activated/non-activated areas in the magnet during the decommissioning of an accelerator facility. In general, an activated magnet includes 60Co and emits gamma rays over 1 MeV; however, current devices are not designed to detect such high-energy photons. Our results showed that two devices could identify the location of highly activated areas, although they could not detect the total absorption peaks of the 1173 and 1333 keV photons from 60Co.

An in situ method to determine the specific activity in concrete structures using a survey meter was established in this study for decommissioning accelerator rooms. This method is much simpler than the conventional sampling method that requires core boring. A survey meter (T-SP2, TAC Inc., Japan) was customised and equipped with a small detector probe, whose size allowed the design of a light-weight Pb shield. For dose rate measurement, a Pb shield thickness of 4.5 cm was enough to shield ambient γ-rays, and its weight (16 kg) was low enough for the device to be carried by a human. A calibration curve was obtained to quickly and easily convert the net contact dose rate on concrete into the specific activity in a PET cyclotron room. The specific activity detection limit for this device was lower than the clearance limit of 152Eu and 60Co in activated materials. Therefore, this method can be used for separating nonactivated concrete from activated concrete during decommissioning. A general correction factor for the slope of the calibration curve was also obtained for use at other accelerator facilities.

Human induced pluripotent stem (hiPS) cells are attracting attention as a tool for regenerative medicine. However, several problems need to be overcome for their widespread and safe use, for example, the high cost of maintaining hiPS cells and the possibility of xenogeneic cell contamination in hiPS cell cultures. One of the main contributors to the high cost of maintaining hiPS cells is basic fibroblast growth factor (bFGF), which is essential for such cultures. Xenogeneic contamination can occur because of the use of mouse-derived feeder cells to culture hiPS cells. To overcome the problems of cell culture cost and xenogeneic contamination, we have developed a novel culture method in which the undifferentiated state and pluripotency of hiPS cells can be maintained under feeder-free and bFGF-free conditions. Our new approach involves the addition to the culture medium of highly sulfated hyaluronic acid (HA-HS), in which the hydroxyl groups of d-glucuronic acid (GlcA) and N-acetyl-d-glucosamine (GlcNAc) are chemically sulfated. HA-HS promotes bFGF signaling and maintains the undifferentiated state and pluripotency of hiPS cells under feeder-free and bFGF-free conditions. By contrast, non-sulfated hyaluronic acid and low sulfated hyaluronic acid do not maintain the undifferentiated state and pluripotency of hiPS cells. These results indicate that the maintenance of hiPS cells under feeder-free and bFGF-free conditions is an HA-HS specific effect. This study is the first to demonstrate the effects of sulfated hyaluronic acid on mammalian pluripotent stem cells, and provides a novel method for maintaining hiPS cells using HA-HS.

Fluorescence imaging flow cytometry offers highly accurate analysis of a large number of cells compared with conventional flow cytometry by virtue of its imaging capability. Unfortunately, the throughput of conventional fluorescence imaging flow cytometers is limited to ~1,000 cells/sec, which is one order of magnitude lower than that of conventional non-imaging flow cytometers. This is due to the low data transfer rate of a CCD image sensor with a time-delay integration technique employed to achieve sufficient sensitivity for fluorescence imaging of fast flowing cells. Replacing the CCD image sensor with a CMOS image sensor can potentially overcome the throughput limitation by virtue of its high data transfer rate, but critically sacrifice the imaging sensitivity because the time-delay integration cannot be employed to current CMOS image sensors. Here we present a fluorescence imaging flow cytometer that achieves comparable throughput and sensitivity with non-imaging flow cytometers. It is enabled by high-energy-density light-sheet excitation of flowing cells on a mirror-embedded PDMS-based microfluidic chip and by fluorescence image acquisition with a CMOS image sensor. The light-sheet excitation allows us obtain fluorescence images of flowing cells at a speed of >1 m/s, corresponding to a high throughput of >10,000 cells/sec. To show its biomedical utility, we use it combined with machine learning to demonstrate accurate screening of white blood cells and real-time identification of cancer cells in blood.

When a negatively charged muon is stopped in a substance, it is captured by an atom of the substance, and the muonic atom is formed. The muon capture process is significantly affected by the chemical environment of the atom and factors such as molecular structure (chemical effect). In this study, we performed muon irradiation for low-pressure CO, CO2, and COS molecules and measured the muonic X-rays emitted immediately after muon capture by an atom. In this paper, we quantitatively discuss the muon capture probability of each type of atom using the LMM model.

"Naive" mouse embryonic stem cells (ESCs) are derived from pre-implantation embryos and possess pluripotency, the ability to differentiate into any cell type of the body. "Primed" mouse epiblast stem cells (EpiSCs) are also pluripotent but are derived from post-implantation embryos. ESC-derived EpiSCs (ESD-EpiSCs) are "primed" pluripotent stem cells and can revert to naive reverted ESCs (rESCs). O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) is a posttranslational modification in the cytoplasm and nucleus. O-GlcNAc is transferred to serine and threonine residues of proteins by O-GlcNAc transferase (Ogt) and removed from them by O-GlcNAcase (Oga). In naive ESCs, O-GlcNAc contributes to maintain the undifferentiated state. In the transition from naive state to primed state, Ogt maintains cell survival, whereas Oga has no function. However, the function of O-GlcNAc in primed ESD-EpiSCs and during the reversion from the primed state to naive rESCs remains unclear. Here, we show that Ogt is required for the survival of primed ESD-EpiSCs. The expression of cytosolic Oga was significantly increased during induction from naive ESCs to primed ESD-EpiSCs. Furthermore, both Ogt and Oga were required for the reversion from primed ESD-EpiSCs to naive rESCs. These findings indicate that O-GlcNAcylation plays an important role in the survival of primed ESD-EpiSCs and in their reversion to naive rESCs.

We present on-chip fluorescence imaging flow cytometry by light-sheet excitation on a mirror-embedded microfluidic chip. The method allows us to obtain microscopy-grade fluorescence images of cells flowing at a high speed of 1 m/s, which is comparable to the flow speed of conventional non-imaging flow cytometers. To implement the light-sheet excitation of flowing cells in a microchannel, we designed and fabricated a mirror-embedded PDMS-based microfluidic chip. To show its broad utility, we used the method to classify large populations of microalgal cells (Euglena gracilis) and human cancer cells (human adenocarcinoma cells). Our method holds promise for large-scale single-cell analysis.

In order to investigate the neutron transportation from a beam-line tunnel to an access maze at a 12-GeV proton accelerator, we measured the spatial distribution of thermal and epithermal neutrons by using the Au activation method in detail. Gold foils were placed at about 70 positions in the maze in the case of the insertion (or extraction) of a copper target of 1 mm thickness into (or from) the beam axis in front of the maze. After the end of accelerator operation, relative activities of the Au foils were simultaneously measured by using an imaging plate technique and the radioactivity of one reference foil was also measured with a HPGe detector to convert to the absolute activities of all foils. It was found that the neutrons reach to the depth of the maze in the case of the insertion of the copper target. This result reflects higher proportion of high-energy particles from the copper target to that from other beam loss points and high-energy particles become the successive source of low-energy neutrons. Furthermore, it was found that several circumstances such as door walls and electric wire cables obviously affect the absorption effect of thermal neutrons. The reaction rates obtained in this study were also used for the benchmark of the Monte Carlo simulation code, MARS15 (version of February 2008). The results of the MARS15 calculations precisely reproduced experimental results and significant effects of the electric wire cables and door walls.

For evaluation of radioactivity induced in the concrete samples from accelerator facilities, the residual radioactivity in concrete sample, collected from seven accelerator facilities, was determined by γ-ray spectrometry. The tritium was extracted by the heating method using an IR furnace, and measured with a liquid scintillation counter. It was found that the major radioisotopes activated mainly by neutrons in the concrete samples were 152Eu, 60Co, 134Cs and 3H. The concentrations of radioactivities induced by thermal neutron capture are the highest at a depth of 10 cm in the concrete wall. The correlation between tritium, 60Co and 152Eu activity was investigated by measuring many concrete samples for seven accelerator facilities. The results indicate that their activities are strongly correlated with each other. So it would also be concluded that the total activity in shielding concrete could be estimated on the basis of the activities of 60Co and 152Eu.

The 36 Cl/Cl ratios of groundwater samples were measured by accelerator mass spectrometry (AMS) in order to investigate the potential use of 36 Cl as a dating tool for modern groundwater. Groundwater samples were obtained from several piezometers in the Oderbruch in northeastern Germany. The shallow confined aquifer of the area is mainly recharged by the infiltration from the River Oder. From the results of measurements, the pre-bomb and the recent background 36 Cl/Cl ratios in the basin of the Oder were estimated to be 7–9 × 10 −14 . The 36 Cl fallout values estimated from the 36 Cl/Cl ratios of the Oderbruch samples, which were dated by the 3 H/ 3 He method, show good agreement with Dye-3 ice core data. These results suggest that the distribution of 36 Cl in groundwaters reflects the influence of the 36 Cl bomb pulse. This, in turn, suggests that the distribution of 36 Cl/Cl in modern groundwaters could reveal groundwater ages and flow systems in a region.

An 129I-AMS system has been developed on the 12UD tandem accelerator at the Tandem Accelerator Complex, University of Tsukuba using a 97Mo16O2 molecular pilot beam method developed at the complex. The acceleration voltage of the tandem is precisely controlled and kept within 0.1% accuracy for several days under the 97Mo16O2 molecular pilot beam method. This stability is enough to maintain a stable transmission of 129I ions through the tandem accelerator. Simultaneously generated 127I negative ions are measured by a Faraday cup installed just after a bending magnet for the ion source. Both 129I− and 97 Mo 16 O 2 - ions are accelerated concurrently and the resultant 129I12+ and 97Mo9+ ions are transported to an AMS beam line. A second stripper foil sweeps out the 97Mo9+ ions from the AMS beam line. The 129I26+ ions are selected over the Mo ions for detection using a pair of magnetic and electrostatic deflectors. Finally, 129I26+ ions are clearly detected using a SSD detector, with no strong background. The accelerator voltage is set to 9.68 MV in order to get the most efficient yields of both 129I12+ and 129I26+. The ratio of the background level of 129I to 127I is ∼1 × 10−13.

We have measured the 36Cl/Cl ratio of uncultivated surface soil samples collected from 11 areas distributed throughout Japan to determine the undisturbed value of the ratio. The ratio was found to be on the order of 10−13 except for the Tokai-mura area, where four research reactors, two commercial nuclear power plants and a nuclear fuel reprocessing plant have been operated. The observed ratio in the Tokai-mura area was higher than 10−12. Notably, soil samples collected from a site of commercial BWR nuclear power plants in Fukushima prefecture showed no significant increase in 36Cl/Cl ratio. The 36Cl/Cl ratio depth profiles of soil samples collected at both of Makabe-town and Tokai-mura were also measured. Since Makabe-town is located about 50 km apart from Tokai-mura, we do not expect it to be affected by the nuclear facilities. No large variations were observed in the Makabe depth profile; the measured ratios ranged from ∼3 to ∼5 × 10−13. The result obtained for Tokai-mura is significantly different in that from the surface to about 80 cm depth, the measured ratios, ∼10−12, are much higher than any at Makabe. At depth below 80 cm, the Tokai-mura ratios are lower and become indistinguishable from those at Makabe. The 36Cl/Cl ratio in unaffected areas of Japan is estimated to be 3–4 × 10−13.

With the current AMS system on the 12UD Pelletron tandem accelerator at the University of Tsukuba, we are able to measure the long-lived radioisotopes of 14 C, 26 Al, 36 Cl and 129 I by employing a molecular pilot beam method that stabilizes the terminal voltage with 0.1% accuracy. Several major improvements have been made to increase the sensitivity of the AMS system to 26 Al and 36 Cl radioisotopes. For 26 Al-AMS, the ions extracted from the ion source have been changed from Al − to AlO − by using an Al 2 O 3 target sample. In addition, 26 MgO − molecular ions are used as a pilot beam to control the terminal voltage through slit current feedback. Also, a fully-stripping AMS technique is used to achieve an effective detection limit of better than 5 × 10 −15 for the 26 Al/ 27 Al ratio. For 36 Cl-AMS, the terminal voltage has been increased from 9 MV to 10 MV, thereby increasing the energy of the 36 Cl 9+ beam to 100 MeV. This energy increment helps us to get a clearer separation between 36 Cl and 36 S in a new Δ E − E detector. In addition, the yield of 36 Cl 9+ is increased by 1.5 times as a result of the higher ion energy at the terminal stripper foil. The standard deviation of the fluctuations of the 36 Cl/ 35 Cl ratio is within ±2%, and the effective detection limit is better than 2.0 × 10 −14 .

The thermal neutron fluence that poured into the shielding concrete of proton accelerator facilities was estimated from the in situ production of 36Cl. The thermal neutron fluences at concrete surfaces during 10–30 years of operation were in the range of 1012–1014 n/cm2. The maxima in thermal neutron fluences were observed at ≈5–15 cm in the depths analyzed for 36Cl/35Cl by AMS. These characteristics imply that thermalization of neutrons occurred inside the concrete. Compared to the several tens of MeV cyclotrons, secondary neutrons penetrate deeper into the concrete at the high-energy accelerators possessing acceleration energies of 400 MeV and 12 GeV. The attenuation length of neutrons reflects the energy spectra of secondary neutrons emitted by the nuclear reaction at the beam-loss points. Increasing the energy of secondary neutrons shifts the maximum in the thermal neutron fluences to deeper positions. The data obtained in this study will be useful for the radioactive waste management at accelerator facilities.

We measured the production rates of the spallation of 197Au, of which plates were attached on the wall of the neutrino target station of KEK, induced by the secondary particles emitted from the 12-GeV proton bombardment of a thick aluminum target. The spallation production rates of 197Au were also calculated using the newly issued MARS15 code system in order to compare the experimental and theoretical production rates. The calculated production rates agreed with the experimental ones. Products with mass numbers close to that of 197Au were produced by the prominent low-energy neutrons. Although, at energies higher than 300 MeV, the fluxes among neutrons, protons, π+ and π− were comparable, the pionic nuclear reactions were highly effective in producing lighter-mass products (

The radiological feature of the radioactive material leak incident at the J-PARC Hadron experimental facility has been investigated. From the systematic analysis focusing on the species and behavior of radionuclides originated in the gold target that had been used for nuclear and particle physics experiments since December 14, 2012, we have figured out the major process that resulted in the release of radioactive materials into the user working areas in the Hadron experimental hall as follows; 1) a variety of radionuclides had been produced in the gold target via nuclear spallation reactions, 2) radionuclides with boiling points lower than the melting points of gold were mainly discharged from the gold target because of the instantaneous overheat which raised the temperature of the gold target above the melting point of gold by injection of the anomalously intense-pulsed beam, 3) the radionuclides diffused in the primary beam line room by the air circulation system and leaked into the user working area through the inadequate hermetic sealing for cables and bulk shields between the primary beam line room and the user working areas.

Accelerator mass spectrometry (AMS) was applied to the analysis of 36Cl induced in concrete samples obtained from accelerator facilities. In order to use a small amount of concrete sample and to separate chlorine as pure as possible, an improvement of separation process was developped. Chlorine was extracted from 1–5 g of concrete into 0.01 M nitric acid in a pressurized decomposition vessel. After determining chlorine using ion chromatography, a certain amount of NaCl solution was added to obtain sufficient amounts of AgCl precipitate and to dilute to a suitable isotope ratio of 36Cl to 35Cl (36Cl/35Cl) for the AMS (10-12–10-10). A careful purification procedure was applied to reduce 36S interference in AMS. Good reproducibility and small error throughout the chemical process for sample preparation was attained. Depth profiles of 36Cl/35Cl in concrete of a medium-energy cyclotron were measured by the developed method and compared with the results of γ-emitters induced by thermal neutrons. Since it was confirmed that 36Cl was produced by thermal neutron capture of 35Cl, the thermal neutron fluence irradiated during accelerator operation could be obtained using 36Cl/35Cl. In order to estimate the neutron fluences, the 36Cl/35Cl measurement by AMS is more useful than radioactivity measurements of other isotopes such as γ-emitters because AMS directly provides the isotope ratio and the half-life of 36Cl is very long.

22Na is one of the long-lived radionuclides induced in shielding concrete of a beam-line tunnel of a high-energy particle accelerator facility and poses a problem of radiation wastes at the decommissioning of the facility. In order to estimate the 22Na concentration induced in shielding concrete, chemical reagents such as NaHCO3, MgO, Al203, SiO2 and CaCO3 were irradiated at several locations in the beam-line tunnel of the 12 GeV proton synchrotron accelerator at KEK, and the 22Na concentrations induced in those chemical reagents were measured. Low-activation concrete made up of limestone aggregates was also irradiated by secondary particles in the beam-line tunnel and the long-lived radionuclide, such as 22Na, concentrations induced in the concrete were measured. It was confirmed that 22Na concentrations induced in Mg, Al, Si and Ca were lower than that in Na, and that 22Na concentrations induced in the low-activation concrete was lower than those induced in ordinary concrete made up of sandstone aggregates.

High-energy protons and neutrons produce a variety of radionuclides as well as noxious and oxidative gases, such as ozone and nitric acid, in the air mainly through the nuclear spallation of atmospheric elements. Samples were collected from the surfaces of magnets, walls, and floors in the neutrino beamline tunnel and the target station of the KEK 12-GeV proton synchrotron facility by wiping surfaces with filter paper. Considerably good correlations were found between the amounts of nitrate and tritium and between those of nitrate and 7Be. This finding gives evidence that at high-energy proton facilities, nitric acid is produced in the radiolysis of air in beam-loss regions. Also, the nitric acid on the surfaces was found to be desorbed and tended to be more uniform throughout the tunnel due to air circulation. The magnitude of diminishing from the surfaces was in the order of tritium>nitrate>7Be.

We measured radiation heating induced by secondary particles from 12-GeV primary proton–beam interactions. A newly developed “cryogenic calorimeter” technique was employed to precisely measure heat fluxes of 0.2–1 W deposited in a large copper absorber. The results were compared with calculations by using Monte-Carlo codes, MARS and PHITS.

An infrared furnace (ULVAC RHL-410P) was newly applied to the extraction of tritium from concrete samples. After studying the tritium recovery yield regarding temperature and time, the best extraction conditions were set to 800 °C (setting temperature) for 30 minutes under Ar-gas flow of 200 ml/min. Tritium was collected in two cold traps and transferred to a vial for liquid scintillation counting. It took about one hour for the extraction of tritium. Reproducibility and recovery yield of tritium were about 100% compared to the values obtained by the ordinary heating method using an electric furnace. Gamma-ray emitters and tritium of concrete samples collected from several accelerator facilities have been determined. The specific activity of tritium strongly correlated with that of 152Eu and 60Co, so it was found that tritium was produced by thermal neutron reaction by the 6Li(n,α)3H reaction. The results indicate that the tritium specific activity in concrete can be estimated from the 60Co specific activity obtained easily by γ-ray measurement.

The radioactive concentrations of radionuclides were measured in the soil and groundwater below the 12 GeV proton beam-line tunnel at KEK. Various long-lived radionuclides, (7Be, 22Na, 46Sc, 54Mn, 60Co, 134Cs, 152Eu and 154Eu) were observed in the soil samples by γ-ray spectra measurements, and 3H was also detected by liquid scintillation counting. On the other hand, 3H, 22Na and 54Mn, which were leached from the soil were measured in the groundwater below the EP2 beam line. 3H and 22Na were also found in slight amounts in groundwater collected in a well dug beside the East Counter Hall. From a comparison with the radioactive concentration in soil and groundwater, the order of the leaching percentages were 3H>22Na>54Mn. This tendency was in agreement with an experimental result of the RI laboratory.

Tritium induced in BWR reactor shielding wall and PWR biological shielding wall irradiated by thermal neutrons is considered to be the critical radionuclide for trench disposal management in Japan. For the purpose of tritium quantification, preparing a specimen of activated concrete without letting tritiated water scatter away is, however, practically impossible. This calls for an alternative means of tritium quantification through indirect estimation from measurement of a substitute radionuclide, such as 152Eu, that is easy to quantify. Many types of concrete and their raw materials were sampled and irradiated by thermal neutrons of the JRR-4 reactor to find out the correlation existing in irradiated concrete between the specific activities of tritium and of 152Eu. The induced activity of for 152Eu was measured by Ge detector, and that of tritium by liquid scintillation counter. From the results measured on the various types of concrete, the formula obtained empirically between 3H and 152Eu was 3H(Bq/g)=...

Aerosol-size distributions of218Po were determined for the accelerator tunnel air sampled during machine operation and for the basement air of a concrete building, where the number and the size distribution of non-radioactive aerosols are greatly different from each other. The218Po distributions depended very much on the size distributions of ambient non-radioactive aerosols, and could be well explained by an attachment model of218Po to ambient non-radioactive aerosols.

Mossbauer effect measurements for the 81 keV transition in133Cs have been performed with133Xe-implanted sources prepared by means of an electromagnetic isotope separator. The behavior of the isomer shift of133Cs impurities was studied in various metals. Some correlations were found between measured isomer shifts and electronic properties of the host materials, and they show that the host conduction electrons have an important role in the determination of the isomer shift in metals.

A simple retardation system has been constructed in order to realize low-energy ion-implantations using an electro-magnetic isotope separator (EMIS). Mass-separated ions are decelerated through a smoothly increasing potential which is produced in a box which is coated inside with a highly resistive film. To test the performance of the system, 133Xe ions retarded from 20 keV by a maximum of 15 keV were implanted into a nickel foil covered by a thin copper layer, and their mean range in copper was determined with a radiochemical technique. The observed ranges are in good agreement with theoretical prediction, which manifests that the system works well as expected.