Radiation Physics and Chemistry (1977)最新文献

Absorption and emission spectra of the methylviologen (MV²⁺)/tris (2,2'-bipyridine) ruthenium(II)[Ru(bpy)²⁺₃ system in a variety of solid systems—ethylene glycol-water glass, polymer foil, cellulose, and wool—have been studied at 4.2, 77, and 298 K. It was found that MV²⁺ always quenches the luminescence of $\text{∗}\text{Ru(bpy)}{}^{\mathrm{2+}}{}_3$. However, the MV^+. radical cation, which is generated at 298 K as a result of a quenching process, is not generated at 77 and 4.2 K. Lowering of the temperature probably prevents the diffusion of electron donor to the oxidized form of photosensitizer and enables instantaneous back reaction. The formation of the MV^+. radical cation under the influence of light λ > 300 nm at low and ambient temperatures has been studied. The crucial role of water in the oxidation of MV^+. was confirmed in a pulse radiolysis experiment.

The radiation chemical reaction of CO-H₂ mixture up to 8.4 x 10⁵ Pa has been studied. The G values of oxygen containing organic compounds except methanol increased with increasing total pressure of reactant. The G values of most of products except trioxane and tetraoxane were increased with raising of temperature in the range from 210 to 350 K, while the G values of trioxane and tetraoxane reached the maxima at 243 K and decreased rapidly with raising of temperature. From the dependencies of G values of these cyclic ethers on pressure and temperature of the reactant, it is considered that these cyclic ethers produced from the neutralization reaction of HCO⁺ (CO)_n cluster ions with electrons in an atmosphere of relatively large amount of hydrogen. The effects of CO content on G values of products did not change with the pressure change of the reactant.

Electron-beam and UV radiation can induce covalent attachment of unsaturated monomers onto a variety of polymer surfaces. The surface characteristics of a polymeric material can therefore be precisely manipulated by grafting the proper combination of monomers onto the surface. Radiation-grafted, sterically nonhindered tertiary acrylamides behave surprisingly well as primers for acidic pressure-sensitive adhesives. Physical and spectroscopic analyses of grafted acrylamides indicate that this unusual behavior is due to hydrogen bonding between the amide functionality in the primer and the acid functionality in the adhesive. Primary and secondary acrylamides are postulated to be less effective because they have the tendency to form hydrogen bonded dimers within the primer rather than interacting with the adhesive.

CONSERVATOME SA have operated a facility at DAGNEUX near LYON, France since 1961. This operation is among the very first of its kind in the entire world. The process is based on gamma rays from Cobalt 60 of which there are three separate units. In addition there is a small experimental unit using Cesium 137. At present CONSERVATOME is owned by TRANSNUCLEAIRE and EPICEA as principal shareholders and so has the support of the French Atomic Energy Commission.

This paper describes the larger D3 unit and reviews some of the products treated at DAGNEUX.

For many years, it was believed that a clear, flame-retardant polyolefin was impossible from technical view-points. But we have developed a clear, flame-retardant radiation cross-linked polyolefin product.

This clear, flame-retardant polyolefin tubing (CFP tubing) using a special technique of material formulation has (1) transparency, (2) excellent flame resistance, and (3) good heat resistance.

Many kinds of coated or impregnated reflecting papers change color or become colored by large radiation doses. Such papers or “labels” do not generally supply dosimetry information, but may give useful inventory information, namely a visual indication of whether or not an industrial product or location has been irradiated to high doses. Among labels available worldwide, a few are suitable for indicating absorbed dose regions of slightly less than 10⁴ Gy (< 1 Mrad), and some are intended for monitoring high dose ranges (i.e., sterilization dose levels of > 10⁴ Gy or > 1 Mrad), and in some cases even up to very high dose regions (∼10⁵ to 10⁶ Gy or ∼10 to 100 Mrad). Only one labels which is expected to be commercially available, was studied for lower dose levels, 10¹-10³ Gy (1-100 krad), namely one based on polymerization of diacetylene. Tests of stability, sensitivity of ambient light, and differences in dose rate and radiation type (gamma rays and electron beams) were made on 15 kinds of labels. The results show that, for many types of indicators, diverse effects may give misleading conclusions unless countermeasures are taken. For example, some of the most commonly used labels, which contain dyes that indicate changes of pH due to release of halogen from halogenated substrates, have limited shelf life and must be protected from extreme environmental conditions. Some also show a marked rate dependence of response. Readings of color reflection optical densities on labels or long paper strips permit somewhat more precise discrimination of dose levels, and may sometimes be useful for monitoring differences in local dose distributions or area monitoring of radiation damage probabilities around particle accelerators or large radionuclide sources.

A self-contained, cesium-137 Research Irradiator with the strength of approximately 147, 000 Ci is located at the Eastern Regional Research Center (ERRC). When the irradiator was installed, the absorbed dose in a reference position of the irradiation field was calibrated and the absorbed doses in other locations of the irradiation field relative to the calibrated positions were measured to map its irradiation field. Self-read pocket dosimeters for gamma-ray were calibrated with a 120 M Ci Calibration Cs-137 source which delivered about 50 mR exposure during a 20-min irradiation at 50 cm from the source. A ferrous sulfate/cupric sulfate solution was used to calibrate the dosimetry of the irradiation chamber which holds three number 10 cans (16 cm inside diameter X 17.5 cm height each). At 20-min exposure, Dmax:Dmin = 1.35, except at the top and bottom $\text{1}\text{3}$ portions of the cans, all positions received a more or less uniform dose (about 0.13 kGy/min) during irradiation. A straight line of total dose (kGy) vs time (min) was constructed following the equation y = 0.127 + 0.137 with r = 0.99, where y is the total dose, and x is time. Radiochromic films and PVC strips were also used to monitor the irradiation operation after comparing results obtained from the chemical dosimeter. Two equations were constructed, respectively, as follows: y = 0.0091x + 0.0015 with r = 0.99, where y = absorbance and x = time (min), and y' = 0.0041x' + 0.0185 with r = 0.99, where y' = absorbance and x' = time (min). Controlled environment is important when such chemical and solid state dosimeters are used during irradiation at subfreezing, refrigerated, or ambient temperature conditions; the equipment has this capability.

The potential of irradiated latex as raw material of commercial use is under testing on pilot plant scale in Indonesia which has 225 kCi Co-60 irradiation facility and can irradiate 1000 tonnes of centrifuged latex per annum. The facility was jointly designed by BATAN of Indonesia and JAERI of Japan and was jointly financed by UNDP/IAEA, Government of Japan and Government of Indonesia under UNDP/IAEA Regional Cooperative Agreement Project on Industrial Application of Isotopes and Radiation Technology. The facility is a water pool type and can accomodate 400 kCi Co-60. The Co-60 rack has two shapes, plate and cylindrical shapes. The plate shape source is used for natural rubber latex irradiation and the cylindrical one is used for other irradiation services. The vulcanization system consists of three major components : emulsification unit ( height : 650 mm, diameter 500 mm ), mixing unit ( height : 1900mm, diameter 1200 mm ) and vulcanization reactor ( height : 1800 mm, diameter 1300 mm ). The first two components are located outside shielded room while the third one-in irradiation room. The radiation vulcanization process is a much simpler energy saving process comparedto the conventional thermal process which has two vulcanization steps before and after dipping.

The physical and mechanical properties of irradiated NR Latex are comparable to those of sulfur vulcanized, and depend on many factors such as irradiation dose, sensitizer content, dry rubber content and storage time.

Some properties of the membranes obtained by radiation grafting of 4-vinylpyridine onto poly(vinyl chloride), PVC, have been studied. Quaternization of nitrogen atoms in the grafted films was completely achieved by using Mel and HCL as quaternizing agents. The grafted quaternized pure and plasticized PVC films possess much higher water uptake percent than those grafted unquaternized ones. The quaternized grafted films also show higher electrical conductivity than grafted unquaternized ones. Furthermore, the electrical conductivity of Mel- and HCL-quaternized plasticized PVC films was 100 times that those of quaternized pure, at a given degree of grafting. The tensile strength and elongation percent for the trunk films were measured at various irradiation doses in N₂ atmosphere and in air. The mechanical properties of the wet grafted films were also investigated for films having various degrees of grafting. The good swelling behaviour of the grafted quaternized PVC films and the good mechanical strength of the grafted films may make them acceptable for handling and practical use as anion-exchange membranes.