Nuclear track emulsion

Construct a radioautographic sandwich consisting of a slide with a thin layer of collodion containing pollen and another slide to which was affixed a thin layer of Kodak NTB-2 Nuclear Track Emulsion (use appropriate safelight and bulb wattage see Table 1). 

Protocol updated from Krolak et al. (49) and Dashek and Mills (50). Controls (a) Germinate pollen without [14C]-pro and process as before, (b) Construct a radioautographic sandwich with collodion lacking pollen, (c) Expose a slide coated with Kodak NTB-2 Nuclear Track Emulsion to light and develop emulsion with D-19. (Sample autoradiographs are presented in Fig. 3.)... 

In other studies, Edwards (248), Fairchild, Tonna, and Seibold (257, 258) and Frigero (293) have employed activation analysis low-background radiographic techniques to measure the boron distribution within cells in order to use Boron-10 in clinical trials of an experimental therapuetic procedure, that is, neutron capture therapy. These particular cellular distribution studies were carried out on mouse spleen, and, after the activation, the materials were exposed to photographic nuclear track emulsions of Eastman Kodak Type NTA. The countable a-particle tracks obtained in these experiments showed that concentrations of B-10 of 60 Mg/gm, the amount that can be safely delivered to tumors in human subjects, could be readily determined. In other applications of activation analysis and autoradiography, Vincent (963) and Vincent, Haumont and Roels (964) made microscopic determinations of sodium in compact bone and of bone phosphorus. 

Photographic detection of H-labelled substances on sihca gel, is time-consuming and insensitive [262, 426]. Nuclear-Track Emulsion, Kodak NTB (Firm 52) is more sensitive for tritium than is X-ray film [632]. The sensitivity of autoradiography of tritium-labelled substances can be raised also by impregnating the thin-layer with a photographic emulsion like, e. g., Ilford XK (Firm 75) [126]. This is however a comparatively comphcated procedure. The autoradiographic method can be appreciably improved by inducing fluorescence with tritium at low temperature [408]. This technique is described below ... 

From 20 ml heparinized venous blood lymphocytes were isolated and one part of these was suspended in TC 199 medium, supplemented with calf serum, chicken embryo extract, antibiotics, and cultured for 72 hours in the presence of phytohaemagglutinin (PHA). The other part was used for experiments immediately. Before incubation, the cells were washed twice with isotonic Na,K-phosphate buffer pH 7.4 and resuspended in incubation medium, containing hypoxanthine-8- H (10 uCi/ml). After incubation for three hours at 37 , cells were spun down and washed three times. After hypotonic treatment and fixation, the cells were brought on slides, spread by flame drying, and stained with orceine. The slides were coated with Kodak Nuclear Track emulsion and developed after exposurefor 7 days. Details of the procedure are reported elsewhere (5) ... 

The tracks formed can be directly observed by the naked eye in cloud and bubble chambers, but the tracks remain only for a short time before they fade. For a permanent record we must use photography. On the other hand, in solid state nuclear track detectors (SSNTD), of which the photographic emulsion is the most common variant, the tracks have a much longer lifetime during which they can be made permanent and visible by a suitable chemical treatment. Because of the much higher density of the absorber, the tracks are also much shorter and oft therefore not visible for the naked eye. Thus the microscope is an essential tool for studying tracks in solids. 

Sensitive methods for analysis of plutonium in urine are particularly important for estimating occupational plutonium body burdens. Routinely available instrumentation, such as the alpha spectrometer, can readily detect these low concentrations. More sensitive methods are commonly required for urine samples in order to assess chronic exposures to plutonium. These low detection limits were first achieved in the past by nuclear emulsion track counting (see Table 6-1). In this method, the electrodeposited sample is exposed to nuclear track film, subsequent to the isolation of plutonium. The alpha-particle emitting isotopes of plutonium will leave tracks on the film which are counted to quantify the amount of plutonium. Nuclear emulsion track counting has been used in the past to measure plutonium concentrations in the urine of workers at a nuclear reactor plant (Nielsen and Beasley 1980). A type of scintillation counting has been used to measure plutonium-239 and americium-241 in animal tissues (NCRP 1985). 

Figure 17.1 Trails of ionization left by heavy charged particles (initial energy of 10 MeV/ nucleon) as they penetrate through a photographic plate (nuclear emulsion). The ions interact with the atomic electrons in the emulsion creating ion pairs to expose the emulsion and the hacks become visible after the Him is developed. Notice the straight-line tracks. (From Knoll, 2000.)...

Such search for experiments coincided with studies of the heavy element abundances in the cosmic radiation, carried out by exposure of particle track detectors - nuclear emulsions or plastic sheets - in balloon flights to high altitudes and analysis of the recorded tracks for atomic number and abundance. A survey [33] of all data obtained until 1970 showed one single... 

A more common technique employs a nuclear emulsion to detect the radiation. The sample is irradiated in close proximity to a sensitive emulsion, which is subsequently developed, fixed, and examined under the microscope. In this way it is possible to distinguish tracks due to alpha particles, fission fragments, etc. Faraggi et al. 22) and Mayr 54) used this technique to determine boron by the B (n,a)Lr reaction down to a level of 2 X 10" gm. Lithium at the 10" -gm level was determined by Picciotto and van Styvendael 69) by the reaction Li (n.,a)H and Curie and Faraggi 18) studied the distribution of uranium in the surface of polished mineral specimens by the U (n,/) reaction. 

The and decay-series methods are based on the fact that Th and Pa are generated in seawater by the decay of U isotopes. The isotopes are then carried to the sea floor on particles and incorporated into the nodules and crusts. The residence times for Th and Pa in seawater are short (less than 40 and 160 years respectively). The distribution of Th and Pa with depth in nodules or crusts can be measured by counting a particles after separation from the nodule material and plating on a planchet or more rapidly by a-track counting on nuclear emulsion plates. The growth rate of the nodule or crast can then be calculated from the formula... 

The most striking evidence for the existence of atoms comes from the observation of tracks formed by nuclear particles in cloud chambers, in solids and in photographic emulsions. The tracks reveal individual nuclear reactions and radioactive decay processes. From a detailed study of such tracks, the mass, charge and energy of the particle can be determined. 

Another class of search for experiments is the measurement of heavy element abundances in the cosmic radiation by exposure to particle track detectors— nuclear emulsions or plastic sheets—in balloon flights at high altitudes with analysis of the recorded tracks for atomic number and abundance. A survey [33] of all data obtained until 1970 showed one single event beyond Z 100. With the data collected in the Skylab space station, the limit became more stringent no superheavy nucleus in spite of the 204 recorded tracks with atomic number 74—87 [77]. A similar hmit was deduced [78] after exposure in a satelhte. In a study of cosmic-ray induced tracks in olivine crystals enclosed in iron-stone meteorites, which were exposed in space over millions of years, unusually long tracks were found and attributed to superheavy elements [79, 80]. However, this conclusion could not be maintained [81, 82] after calibration experiments of track dimensions with energetic beams delivered by accelerators. 

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