Ionising radiations

The radiation emitted by radioactive materials is harmful to living matter. Small quantities of radioactive isotopes are used in the process industry for various purposes for example, in level and density-measuring instruments, and for the non-destructive testing of equipment. 

The use of radioactive isotopes in industry is covered by government legislation, see hse.gov.uk/pubns. 

A discussion of the particular hazards that arise in the chemical processing of nuclear fuels is outside the scope of this book. 

Over-pressure, a pressure exceeding the system design pressure, is one of the most serious hazards in chemical plant operation. Failure of a vessel, or the associated piping, can precipitate a sequence of events that culminate in a disaster. 

Pressure vessels are invariably fitted with some form of pressure-relief device, set at the design pressure, so that (in theory) potential over-pressure is relieved in a controlled manner. 

Ionising radiation means atomic and nuclear particles, i.e., gamma rays, electrons neutrons, etc. The intensity of ionising radiation at the earth s surface is not high enough to significantly affect mbbers and hence radiation exposure is only a consideration in connection with apphcations in nuclear plant and possibly where radiation is used to induce crosslinking or for sterilisation. 

Each of the types of radiation has a characteristic way of interacting with matter and transferring its energy. 

Fricke showed furthermore that the hydroxyl radicals produced by the irradiation of water can be intercepted by Fe ions, according to the equation  

When the two kinds of interceptions were united and water was irradiated in the presence of both, of oxygen + ferro-ions, the following reactions occurred  

Effects of HO radicals on biological membranes include alterations in membrane proteins, peroxidation of unsaturated lipids accompanied by perturbation of the lipid bilayer polarity. Berroud et al. (1996) have measured radiation-induced membrane modifications using two fluorescent lipophilic membrane probes (TMA-DPH and DPH) by the technique of fluorescence polarization of Chinese hamster ovary K1 and lymphoblastic RPMI 1788 cell lines, ylrradiation from a Co source with dose rates of 0.1 and 1 Gy/min for a final dose of 4 and 8 Gy induced a dose-dependent decrease of 

Low-dose irradiation with 50 cGy of X-ray induced in vivo production of superoxide dismutase-like substances and accelerated antioxidant activity in liver, brain and bone marrow of male C57BL/6 mice (Yamaoka et al. 1999). 

a transcription factor inducible by oxygen radicals may be an important link in lung fibroses induced by ionising radiation (Haase et al. 1997). 

The radiation emitted during radioactive decay can cause the material through which it passes to become ionised and it is therefore called ionising radiation. X-rays are another t5 e of ionising radiation. Ionisation can result in chemical changes which can lead to alterations in living cells and eventually, perhaps, to manifest biological effects. 

The ionising radiations encountered in industry are principally oi, 3, and X-rays, bremsstrahlung and neutrons. Persons can be irradiated by sources outside the body (external irradiation) or from radionuclides deposited within the body (internal irradiation). External irradiation is of interest when the radiation is sufficiently penetrating to reach the basal layer of the epidermis (i.e. the living cells of the skin). Internal irradiation arises following the intake of radioactive material by ingestion, by inhalation or by absorption through the skin or open wounds. 

The a particle consists of two protons and two neutrons. It is therefore heavy and doubly charged. Alpha radiation has a very short range and is stopped by a few centimetres of air, a sheet of paper, or the outer dead layer of the skin. Outside the body, it does not, therefore, present a hazard. However, a-emitting radionuclides inside the body are of concern because a particles lose their energy to tissue in very short distances causing relatively intense local ionisation. 

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Real Time Radiography (RTR) is an advanced method of radiography in which the image is formed while the job is exposed to ionising radiation. RTR is often applied to objects on assembly lines for rapid inspection. Accept-or-reject decisions may be made immediately without the delay or expense of film development. The main advantages of RTR are thus, reduction in inspection cost and processing time. 

The ptincipal commercial initiators used to generate radicals are peroxides and a2o compounds. Lesser amounts of carbon—carbon initiators and photoinitiators, and high energy ionising radiation are also employed commercially to generate radicals. 

The gray is also used for the ionising radiation quantities, specific energy imparted, kerma, and absorbed dose index, which have the SI unit joule per kilogram. 

In general the nitroso rubbers also suffer from a poor resistanee to ionising radiation, sensitivity to degradation by organie bases, highly toxic degradation products and an exceptionally high cost. The advent of the rubbers based on perfluorofmethyl vinyl ether) considered above and of the phosphonitrilic elastomers considered below would appear to put the commercial future of these materials in extreme doubt. 

PM 77 Fitness of equipment used for medical exposure to ionising radiation... 

Annex 12 Use of Ionising Radiation in the Manutacture ot Medicinal Products Annex 13 Manufacture of Investigational Medicinal Products Annex 14 Manufacture of Products derived from Human Blood or Human Plasma Annex 15 Qualification and validation... 

COP 16 Ionising radiations (parts 1 and 2) Protection of persons against ionising radiation arising... 

COP23 Ionising radiations (part 3) Exposure to radon. 

L7 Ionising radiations (part 4) Dose limitation — restriction of exposure. 

Barron, E.S.G., Ambrose, J. and Johnson, P. (1955). Studies on the mechanisms of action of ionising radiations XIII. The effect of X-irradiation on some physiochemical properties of proteins. Radiat. Res. 2, 145-152. 

In terms of atomic spectrometry, NAA is a method combining excitation by nuclear reaction with delayed de-excitation of the radioactive atoms produced by emission of ionising radiation (fi, y, X-ray). Measurement of delayed particles or radiations from the decay of a radioactive product of a neutron-induced nuclear reaction is known as simple or delayed-gamma NAA, and may be purely instrumental (INAA). The y-ray energies are characteristic of specific indicator radionuclides, and their intensities are proportional to the amounts of the various target nuclides in the sample. NAA can thus... 

AQ4a The use of ionising radiation in the manufacture of medicinal products (pages 23-30) 3AQ9a Excipients in the dossier for application for marketing authorisation of a medicinal product (pages 67-74)... 

Annex 12 Use of ionising radiation in the manufacture of medicinal products (pages 113-118)... 

In order to compare exposures to radon decay-products with those to other forms of ionising radiation, it is useful to assess the effective dose equivalent expressed in sieverts (Sv). A conversion coefficient of 15 Sv per J h m"3, equivalent to 5.5 mSv per WLM, has been recommended (UNSCEAR, 1982). With this conversion factor, the... 

A compounding ingredient added to elastomers to increase their resistance to ionising radiation. Antistatic Rubber... 

This same ability to recognise hidden, unexploited treasure induced me to develop the first comprehensive theory of the polymerisations by ionising radiations [146]. None of the original researchers had stood back from their own findings, seen that their rather primitive theory was incompatible with the results of others, and set about constructing the general theory that was evidently needed. My effort [146] eventually produced a much-refined model of the propagating carbenium ion in solution and its different modes of reaction. 

After the author s retirement in 1985 there followed several theoretical researches. The larger enterprises include a new theory to account for the hitherto unexplained features of the CP induced by ionising radiations, and a critical analysis of the alleged propagation rate-constants kp+. This has shown that the great majority of such claims are ill-founded, and the author explained in detail why he considers only 17 rate-constants to be reliable. 

New views on the cationic polymerisations induced by ionising radiations... 

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