Effect of type of ionizing radiation on radiation crosslinking of polyacrylonitrile fiber hydrolyzate

A comparative study was performed on the effect of different types of ionizing radiation differing by four orders of magnitude in dose rate, namely, γ-rays and electron-beam radiation, on the formation of the network structure in an aqueous salt solution of the industrial hydrolyzate of polyacrylonitrile fiber, as well as on the properties of irradiated solutions and polyelectrolyte gels obtained from these solutions. For the first time, it was shown that the efficiency of radiation-chemical processes induced by electron-beam radiation in macromolecules of the polyacrylonitrile fiber hydrolyzate is two-three times that in the case of γ-irradiation.     

Multi-point radiation monitor

A simple, inexpensive instrument for measuring radiation fields in otherwise inaccessible locations has been developed. The RadRope consists of a series of radiation detectors inside a flexible sheath and connected to a data readout device to alert the operator to unexpected radiation fields at a remote location. The instrument is designed for use in a maritime environment and will assist inspection personnel in detecting potential illicit radioactive materials or radiological/nuclear weapons of mass destruction.     

Analytical application of Cherenkov radiation

The application of Cherenkov photometry gives a new possibility in isotope dilution analysis for determination of specific activity in a simple way. If the compound of the isotope is coloured or it can be converted into a coloured compound, it is possible to measure the activity and the concentration of the compound in one sample in one series of measurement. Methods were worked out for the determination of³²P specific activity by measuring the³²P efficiency, activity and the phosphorus content of the same sample. It is possible to measure the specific activity in an automatic mode with some modification of the liquid scintillation spectrometer.     

Practical applications of radiation chemistry

The physical, chemical, and biological effects of ionizing radiation on matter are the basis of many practical applications. The number of such applications is growing, and sources of gamma radiation and X-rays are now being operated in harsh, demanding environments. They play an important role in the economic development of many countries. The text was submitted by the author in English.     

Status of radiation processing dosimetry

Several milestones have marked the field of radiation processing dosimetry since IMRP 7. Among them are the IAEA symposium on High Dose Dosimetry for Radiation Processing and the international Workshops on Dosimetry for Radiation Processing organized by the ASTM.

Several standards have been or are being published by the ASTM in this field, both on dosimetry procedures and on the proper use of specific dosimeter systems. Several individuals are involved in this international cooperation which contribute significantly to the broader understanding of the role of dosimetry in radiation processing.

The importance of dosimetry is emphasized in the standards on radiation sterilization which are currently drafted by the European standards organization CEN and by the international standards organization ISO. In both standards, dosimetry plays key roles in characterization of the facility, in qualification of the process and in routine process control.

As a function of the work on the standards, several issues are now receiving major attention. These include traceability and uncertainty limits of the dose measurements, calibration procedures, environmental influence and combination of influence factors such as dose rate and temperature.

The increased attention to these factors have increased the demands on existing dosimeter systems, and rather than new dosimeters, the latest years have seen improvements on established dosimeters.     

Future perspectives of radiation chemistry

Future perspectives of radiation chemistry are discussed by the analysis of the related information in detail as obtained from our recent surveys of publications and scientific meetings in radiation chemistry and its neighboring research fields, giving some examples, and are summarized as follows. (1) Traditionally important core-parts of radiation chemistry should be activated more. The corresponding research programs are listed in detail. (2) Research fields of physics, chemistry, biology, medicine, and technology in radiation research should interact more among them with each other. (3) Basic research of radiation chemistry should interact more with its applied research. (4) Interface research fields with radiation chemistry should be produced more with mutually common viewpoints and research interests between the two. Interfaces are not only applied research but also basic one.     

Analytical application of Cherenkov radiation

Studies were made to establish the possibilities and limitations of the photometric application of Cherenkov radiation. The colour quenching brought about by various coloured substances can be utilized for Cherenkov photometric measurements. The colour quenching is the strongest in the case of yellow, and the least strong for blue; accordingly, the slope of the linear logarithmic correlation between the efficiency and the concentration is higher for yellow than for blue. Glass and plastic vessels alike can be used for the measurements. The measurements have the greatest sensitivity in the case of the external standard. With the aid of an external standard, measurements of very high sensitivity can be made under isotope-free conditions.     

Depolarization of atomic two-photon radiation

A technique of depolarization is used to investigate the coherence and spectral properties of the radiation emitted in the two-photon decay of metastable atomic deuterium. The results agree with the quantum mechanical predictions but may also be interpreted to show that a single photon of a two-photon pair can be considered to have a very short coherence length, a very short coherence time and a broad bandwidth, all limited, in practice, by the transmission properties of the detection system.     

Acetylene-sensitized radiation crosslinking of polytetrafluoroethylene

The radiation crosslinking of PTFE in the presence of acetylene was studied. The yield of crosslinking was determined from thermomechanical testing data and, on this basis, it was concluded that crosslinking follows the chain mechanism. Radiation-crosslinked PTFE possesses high wear resistance and enhanced radiation stability.     

Low-temperature radiation chemistry

An overview of studies on the radiation-initiated chemical reactions of polymerization, copolymerization, graft polymerization, telomerization, oxidation, cryoozonolysis, hydrobromination of olefins, and chlorination of paraffins occurring at low and ultralow temperatures has been presented. Particular attention has been paid to self-oscillating reactions.     

Effects of UV radiation of cells

UV radiation interacts with mammalian cells in a very complex manner, although DNA appears to be the main chromophore. Recent literature within this field is reviewed. The review is concentrated on the following main topics: Chromophores for UV action, photoproducts in DNA, repair of UV-induced DNA damage, wavelength interactions, inactivation, mutagenesis, transformation and protection mechanisms against UV damage.     

Chitosan and radiation chemistry

Chitosan as a raw material with special properties has drawn attention of scientists working in the field of radiation processing and natural polymer products development, and also of specialists working in the field of radiation protection and oncologists. Especially the applications concern reduced molecular weight chitosan which still retain its chemical structure; such form of the compound is fostering biological, physical and chemical reactivity of the product. Chitosan degrades into fragments under γ-ray or electron beam irradiation. Antibacterial properties of the product are applied in manufacturing hydrogel for wound dressing and additional healing properties can be achieved by incorporating in the hydrogel matrix chitosan bonded silver clusters. Another possible application of chitosan is in reducing radiation damage to the radiation workers or radiation cured patients. In the case of radioisotopes oral or respiratory chitosan-based materials can be applied as chelators. Applications of chitosan in oncology are also reported.     

ISO radiation sterilization standards

This presentation provides an overview of the current status of the ISO radiation sterilization standards. The ISO standards are voluntary standards which detail both the validation and routine control of the sterilization process. ISO 11137 was approved in 1994 and published in 1995. When reviewing the standard you will note that less than 20% of the standard is devoted to requirements and the remainder is guidance on how to comply with the requirements.

Future standards developments in radiation sterilization are being focused on providing additional guidance. The guidance that is currently provided in informative annexes of ISO 11137 includes: device/packaging materials, dose setting methods, and dosimeters and dose measurement, currently, there are four Technical Reports being developed to provide additional guidance:

1. 1. AAMI Draft TIR, “Radiation Sterilization Material Qualification”

2. 2. ISO TR 13409-1996, “Sterilization of health care products — Radiation sterilization — Substantiation of 25 kGy as a sterilization dose for small or infrequent production batches”

3. 3. ISO Draft TR, “Sterilization of health care products — Radiation sterilization Selection of a sterilization dose for a single production batch” li]4. ISO Draft TR, “Sterilization of health care products — Radiation sterilization-Product Families, Plans for Sampling and Frequency of Dose Audits.”

     

Analytical application of Cherenkov radiation

Data are reported on the development of a Cherenkov photometric producere, applying the basic principle of the method of LOWRY et al. At various amplifications and channel settings, linear correlations may be obtained between the logarithm of the protein content and the external standard activity or the channel ratio. The values obtained by Cherenkov spectrophotometry based on the Filin method display a linear correlation with each other with a good correlation coefficient.     

Mechanism of radiation degradation of polyisobutylene

GC, GC/MS, GPC, and Solution NMR spectra were used to study the γ radiolysis of polyisobutylene (PIB) in vacuum to different total doses (0–900 kGy) and at different temperatures (77–423 K). NMR spectra show a large number of new resonances with relatively narrow line widths, and a variety of NMR techniques have been employed to determine and quantify the structures associated with these new resonances. Chemical shift assignments were made by comparison with those for small molecule model compounds and predictions based upon calculations according to several different schemes. Chain-end structures have been proposed that account well for the majority of the new resonances, all being the result of an initial chain scission reaction initiated by the radiation. These assignments support some previous proposals for the mechanism of radiation degradation of polyisobutylene and exclude others. For example, NMR provides no evidence for the formation of ethyl chain ends and some of the main chain unsaturated structures previously proposed. NMR also indicate that at higher doses the chain end products formed during initial stages undergo secondary reactions. GC/MS data show the formation of oligomers during irradiation, which may be due to a backbitting mechanism. © 1996 John Wiley & Sons, Inc.     

Degradation of chlorpyrifos by ionizing radiation

Summary A survey was carried out to determine radioactivity concentrations and associated dose rates from the naturally occurring nuclides ²³² Th, ²³⁸U and ⁴⁰K in various surface soil formations of Alhkraje city. Samples were collected from different areas of the study, sieved through a fine mesh, sealed in 0.5-liter plastic Marinelli beaker, and measured in the laboratory for 24 hours each. From the measured g-ray spectra, radioactivity concentrations were determined for ²³² Th ranging from 5.32±2.59 to 16.40±2.04 Bq ^. kg^-1, ²³⁸U (2.87±0.18 to 18.83±0.81 Bq ^. kg^-1), ⁴⁰K (211.33±55.04 to 378.97±36.46 Bq ^. kg^-1) and ¹³⁷Cs (0 to 3.19±1.02 Bq ^. kg^-1). Absorbed dose rates in air doors were calculated to be in the range of 15.29±2.65 to 30.00±3.24 nGy ^. h^-1, the corresponding effective dose rates per person outdoors were estimated to be between 21.00±0.95 to 36.83±2.11 mSν^. y^-1, assuming a 20% occupancy factor.     

Synchrotron radiation spectroscopy of quasi-one-dimensional materials

The optical reflectivity spectra of quasi-one-dimensional polymers (SN)_x, trans-(CH)_x, and polydiacetylene are investigated in an energy range from 1 to 25 eV by use of synchrotron radiation. Observed structures associated with π-electron states are interpreted in terms of the quasi-one-dimensional one-electron bands calculated by the LCAO -type model.     

Useful transformation of a radiation field

The paper deals with the characteristics of the radiation field, namely the flux density and current density. Two transformations of the general radiation field are presented which could considerably simplify the calculations in several situations.     

Quality of the radiation field image

The work defines and analyzes the resolution angle in image obtained by a directional detector. The effect of both the relative directivity diagram of the detector used and complexity of the scanned field are discussed.