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.     

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.     

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.”

     

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.     

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.     

Changes in cell proliferation due to environmental non-ionizing radiation: 2. Microwave radiation

Due to the use of mobile telephones, there is an increased exposure of the environment to weak radiofrequency (RF) electromagnetic fields, emitted by these devices. This study was undertaken to investigate if the microwave radiation from these fields will have a similar effect on cell proliferation as weak electromagnetic (ELF) fields. The field was generated by signal simulation of the Global System for Mobile communications (GSM) of 960 MHz. Cell cultures, growing in microtiter plates, were exposed in a specially constructed chamber, a Transverse Electromagnetic (TEM) cell. The Specific Absorption Rate (SAR) values for each cell well were calculated for this exposure system. Experiments were performed on cell cultures of transformed human epithelial amnion cells (AMA), which were exposed to 960 MHz microwave fields at three different power levels and three different exposure times, respectively. It was found that cell growth in the exposed cells was decreased in comparison to that in the control and sham exposed cells. Cell proliferation during the period following exposure varied not only with the various SAR levels, but also with the length of exposure time. On the other hand, repeated periods of exposure did not seem to change the effects. There was a general linear correlation between power level and growth change. However, the exposure time required to obtain the maximum effect was not the same for the various power levels. It turned out that at low power level, a maximum effect was first reached after a longer exposure time than at higher power level. A similar phenomenon was registered in the studies on ELF electromagnetic fields. Here, it was found that there was a linear correlation between the length of exposure time to obtain maximum effect and field strength.     

Erythrocyte response to near-infrared radiation

The effects of NIR (near-infrared radiation 700-2,000 nm) on bovine erythrocytes in plasma was studied as a continuation of earlier studies. Cell shape was observed and the changes of ratio of hemolysis and electrokinetic potential measured as a function of irradiation time. After 10 min of irradiation, the shape of erythrocyte cells was mainly echinocytic. When these cells were incubated at 311 K for 24 h they regained their initial shape, but fresh erythrocytes that were irradiated for 30 min and aged in vitro did not. These phenomena are due to: (1) the absorption of NIR excitation by hemoglobin; the primary photochemical process being the photo-dissociation of oxyhemoglobin to deoxyhemoglobin. Resulting shape and ratio of hemolysis, structural changes and oxidative stress follow higher deoxyhemoglobin concentration. (2) The absorption of the NIR excitation by proteins, water and lipids. After NIR absorption the membrane surface dehydrates, leading to enhanced protonation and dissociation of hydrogen-bonded complexes. This in turn leads to a change in electrokinetic potential.     

Recombination radiation from organic solids

The recombination radiation from organic solids, defined as the light emission following the fusion of oppositely charged carriers into an electrically neutral state, is discussed as a phenomenon underlying the function of organic light-emitting diodes (LEDs). Its intensity and spectral range depend on the population and nature of the emissive states, which differ, in general, from those created using light. These differences are pointed out and shown to be a result of the reverse pathways of the mutual transformation of localized molecular excitons and coulombically-correlated charge-pair excited states formed either by photoexcitation or electron-hole recombination. Spectral features of the radiation produced by the recombination of statistically independent charge carriers are discussed in terms of two molecules-based excited states like excimers or electromers in single-component materials and exciplexes or electroplexes in multicomponent materials. Consequences for optical and electrical characteristics of organic LEDs are discussed and illustrated by examples. Progress in the fundamental and applied research may be expected based on properties of recombination-produced electronic excited states.     

Wastewater treatment with ionizing radiation

In water treatment by ionizing radiation ^·OH is suggested to initiate the degradation of organics. In these reactions mostly carbon centred radicals form. Here we show that other inorganic radicals also highly contribute to the initiation of degradation. Cl^? and HCO₃ ^? in the treated water reacting with ^·OH transform to Cl ₂ ^·? and CO ₃ ^·? . In their reactions C-centred radicals form, too. The reactions of e _aq ^? and H^· water radiolysis intermediates may also produce carbon centred radicals. The C-centred radicals react readily with dissolved O₂, this is the starting step of the gradual oxidation.     

Environmental radiation monitoring in Korea

Environmental radiation monitoring in Korea can be categorized as (1) nationwide monitoring program and (2) monitoring program for nuclear facilities. The former is designed to quickly detect any abnormal situation in environmental radioactivity levels. The latter has the objective of evaluating environmental radioactivity levels resulting from the operation of nuclear facilities. This paper describes the two monitoring programs, how they are implemented, items of being measured, analytical techniques, quality control programs and R&D activities associated with the monitoring. Also, some of the latest data obtained by the monitoring programs are introduced.     

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.     

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.     

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.     

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.