The article was written on the occasion of the 100. anniversary of the Nobel Prize in Chemistry awarded to Maria Skłodowska-Curie. The United Nations General Assembly honoured this event by announcing the year 2011 the International Year of Chemistry. Maria Skłodowska-Curie was i.a. the initiator of radiation chemistry, a branch of science analyzing the chemical effects that matter shows when exposed to ionizing radiation. The development of this branch resulted in radiation technologies’ applications in many fields of industry, medicine, agriculture, protection of the environment, space research and science. Our point of departure was the article Sur l’étude des courbes de probabilité relatives à l’action des rayons X sur les bacilles that Maria Skłodowska-Curie published in 1929 in the Bulletin of the Académie des sciences. In this study, she presented - for the first time ever - the curves of the so called radiation inactivation, i.e. the relationship between the bacteria life expectancy and the dose of radiation absorbed by it. From the today’s point of view, it can be stated that the researcher laid the foundations of the methods of radiation sterilization and material processing by means of radiation. In this context, we recall the history of the first accelerator installation devised and built in 1968 at the Institute of Nuclear Chemistry and Technology in Warsaw. Basing on experiences with the linear electron accelerator, the LAE 13/9 was completed in 1992 as the so far only Polish industrial installation for radiation sterilization of medical products and transplants as well as for food irradiation.
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The article presents from the perspective of one hundred years the work of Maria Curie-Skłodowska, which in many cases was ahead of the state of knowledge of the time. It opened new horizons and for this reason we made many digressions. The fact of awarding her the Nobel Prize twice is a sensation enough to present the values of careful activity of the Nobel Prize Committee that emphasizes the importance of Maria’s achievements. A significant element of Maria Sklodowska-Curie’s achievements was still mysterious character of the radiation in her time, and only chemical approach made it possible to organise the phenomena and explain the origin of the radiation. The essence of the research was an arduous separation of components following the track of growing radiation of successive fractions of preparations. This research was a start of the technology of educement of dispersed elements in great mass of materials. We underline the paramount role of the chemical research Maria Skłodowska conducted while still in Warsaw in the laboratories of the Museum of Industry and Agriculture under the guidance of an excellent chemist Józef Jerzy Boguski. Her research in Paris was the origin of the semi-commercial scale in chemistry and setting aside a special shed outside the university building was the beginning of the institutes that now function beyond universities and are key element of scientific and technical progress. Technology of splitting developed by Maria Skłodowska-Curie was applied also by other radiochemists, e.g. By Otto Hahn. Lively movement in radiochemistry of her lifetime resulted in Maria’s disputes with e.g. German chemist Marckwald, who questioned the originality of polonium. The scientific disputes like this one Maria won triumphantly although in several others she had to accept opponents’ argument, as in the case of radon. Her experiments were planned with utmost rationality as it was with the rejection of the hypothesis saying that radioactivity was transferred from the outer space or from the sun. A great part of Maria Sklodowska-Curie’s work was connected with biology which was demonstrated by describing in mathematical terms, for the first time in the history of radiobiology, nonexistent at that time, of the phenomenon of inactivation of bacteria by ionizing radiation. We emphasize difficult conditions for the health of the radiochemists of the time but we don’t find any proof that there was any influence of ionizing radiation on Maria’s health. She must have absorbed much greater doses of radiation during her heroic work in the mobile radiological surgery at the front of the 1st World War. We don’t think it’s appropriate to speculate rashly about contamination with alpha emitters. Unfortunately, due to her family’s protest it was impossible to collect samples of remains before their relocation to the Pantheon in Paris.
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The communication reports a serious complication connected with preparation, storage and transportation of fuel for thorium and uranium/thorium nuclear reactors. Whereas uranium fuel of any degree of enrichment is free from radium, which produces radon-222, thorium itself produces thoron (radon-220). Measurement of thoron by a routine ionization-chamber device around a small sample of 2 g thorium dioxide shows already the health endangerment situation. The presence of thoron is also confirmed by a typical solid state dosemeter (polymer CR-39), exposed to the air around ThO2 and etched afterwards with warm NaOH solution. The unavoidable presence of thoron can cause increase of price of production of nuclear fuel, demanding special approach to the method of manufacture.
Radon in the environment of early Earth was present in sites, determined by location of deposits of uranium, in very different geological formations. According to the decay of uranium-238, the total production of radon at the beginnings was twice as high as now and was continuously diminishing to the present levels. This nuclide could not play as big a role as do radioactive elements connected with the presence of high concentration of 235U, which was high enough in some places to give rise to formation of natural nuclear fission reactors (e.g. Oklo phenomenon in Africa). The main role of ionizing radiation in prebiotic chemistry and biological evolution was played by low LET (linear energy transfer) radiations, as deep penetrating sources of external energy. High LET radiations are of low penetration and could act only superficially. Radon is an exception, due to its easy transfer in the air. Therefore, it could play a role already in the cases of these early organisms which exhibited the gaseous exchange of chemical compounds with the surrounding atmosphere. The action was destructive, but, on the other hand, was also mutagenic. Nevertheless, the general quantitative effect of radon on the global scale could not be larger than of other radioactive nuclides. Presented considerations are part of the chapter by the present author on the role of nuclear and radiation chemistry in astrobiology, in the monograph published by American Scientific Publishers [1].
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A technically useful composition containing polypropylene (PP) as a principal constituent, expected to be working or to be processed in ionizing radiation field, e.g. for sterilization, has to be protected from undesired radiolysis resulting in radiation damage. Usually, conventional additives are used which are generally effective, especially when containing aromatic groups. They can be sometimes unacceptable, e.g. in medical applications. Polystyrene (PS) has been investigated as a protective component, in analogy to the classical case of cyclohexane/benzene system. Mechanical mixing of both polymers showed to be of modest effect, but two other procedures, of soaking polypropylene powder with polystyrene dissolved in styrene, or soaking with styrene and gamma preirradiation with resulting grafting (G = 12000 effects/100 eV), resulted in the composition of improved resistance towards radiation. The energy transfer, which explains the effect, is extended at a distance of 8-12 mers of polypropylene. The investigations have been made by gas chromatography and diffuse light reflection spectrophotometry (DRS), after 10 MeV electron beam irradiations.
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Motivation of the present paper is the new interest in the so called "cold fusion" of deuterium. The author, former electrochemist and presently a radiation chemist, was involved in writing a paper expressing criticism toward original Fleischmann and Pons [1], next called F&P "discovery", after experimental trials performed to repeat the claims. Actual efforts to revive an old idea of the D+D reaction in palladium electrode during electrolysis of heavy water consist in application of a new kind of palladium cathode, additional electric and magnetic fields around the electrolytic cell and experiments with polymeric detector, supposed to show nuclear disintegration of palladium and other strange nuclear transmutations. These new approaches to the almost twenty year old idea did not bring revelations in the field of energetics, therefore the nowadays reaction of popular media is far less enthusiastic than the original outburst of curiosity after the F&P paper. The author of the present paper analyses the artifacts and wishful thinking approach seen in publications, indicating that the problem of cold fusion is still unsolved, as it was at the beginning. The whole field belongs to the category of pathological science, like previously polywater, water with the memory of the solute present before dilution, etc.. However, almost all other cases of pathological science have died quietly, the remaining interest in cold fusion asks for an explanation. The international conferences devoted to cold fusion convene frequently every second year or every year, the only change is, that recently the term cold fusion is no longer used but is substituted by enigmatic LENR (low energy nuclear reaction) and CANR (chemically assisted nuclear reaction). In the meantime between different versions of F&P approaches, another cold version of D+D fusion in perdeuterated acetone appeared as so called sonofusion, lasting as pathological science even shorter. Financial support for cold fusion still exists, sometimes by organizations that wish to remain anonymous. The author of the review draws attention to the fact, that presently the majority of affiliations of authors of papers, and financial supports of civil laboratories are connected with military (USNavy) research and more general weaponry research, like in the case of DARPA (Defense Advanced Research Project Agency). The reason is probably a hope, that creation of a true neutron bomb can be achieved, because the actual one is an ordinary nuclear device with enhanced yields of neutrons only. Vivid interest in cold fusion in Japan is connected with the fear, that some nuclear achievements may escape the attention, as it was the case of what happened in 1945. The last but not least reason for the interest in cold fusion are the controversial European projects of ITER and HiPER trying to develop the high temperature fusion power plants, with an active zone of nuclear reaction heated to 100 million degrees K. Among many unsolved objections, the link between that zone and economic production of electric current is prohibited by actual physical and chemical laws. Therefore physicists involved in the projects are aware of difficulties and express interest in approaches to cold fusion ideas, especially in chemical aspects connected with solving, perhaps, difficult problems, e.g. from the area of material science.
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W wyniku działania promieniowania jonizującego w polimerach mogą zachodzić równolegle cztery podstawowe procesy chemiczne: sieciowanie, degradacja, tworzenie wiązań nienasyconych oraz utlenianie. Często efekt tworzenia wiązań poprzecznych przeważa nad zjawiskiem pękania łańcuchów, co w konsekwencji prowadzi do korzystnej modyfikacji właściwości polimeru. Zastosowanie indukowanego radiacyjnie sieciowania jest niekiedy wygodniejsze od sieciowania chemicznego ze względu na możliwość prowadzenia procesu w temperaturze zbliżonej do pokojowej oraz łatwość kontroli i optymalizacji dawki pochłoniętej promieniowania. Z punktu widzenia praktycznych zastosowań istotne wydaje się zwłaszcza poznanie wpływu niehomogeniczności odkładania energii promieniowania, a w szczególności roli gniazd wielojonizacyjnych na procesy tworzenia sieci wiązań poprzecznych w elastomerach. Zastosowanie nowoczesnych technik analitycznych w chemii radiacyjnej polimerów pozwala odkryć nowe fakty. W szczególności określone za pomocą chromatografii gazowej wydajności radiolityczne wodoru wydzielanego z napromienionego elastomeru typu HNBR wskazują, że tylko połowę wiązań porzecznych powodujących powstanie fazy żelowej można powiązać z reakcjami sąsiednich łańcuchów polimeru. Wodór nie jest oznaczany w konwencjonalnych, chemicznych metodach sieciowania, ponieważ jest wydzielany jedynie w nietypowych procesach sieciowania radiacyjnego. Również nietypowe techniki spektroskopii (DRS), zastosowane np. w radiolizie HNBR, pozwalają badać indukowane radiacyjnie procesy chemiczne w elastomerach.
EN
Absorption of ionizing radiation energy by polymers results in four, parallely running chemical processes: crosslinking, degradation, formation of unsaturation, including multiple bonds and oxidation. If crosslinking prevails over degradation, the modification of properties of polymer goes in useful direction. Intentional, radiation induced crosslinking is in many respects better than chemical, because it is realized at ambient temperature and is readily controlled by adjustment of optimal dose. From the practical point of view, especially important is recognition of inhomogeneous deposition of energy and the role of multi-ionization spurs on processes of formation of the net of crosslinking bonds in elastomers. Introduction of analytical methods used in radiation chemistry of polymers revealed new facts. In particular, gas chromatographic determination of radiation yield of hydrogen in irradiated HNBR rubber has shown, that only the half of crosslinks, as determined by gel fraction, is due to hydrogen abstraction from two neighboring chains and the rest is due to entanglements. Hydrogen is not determined in conventional, chemical crosslinking reactions, because this gas is emitted only in the non typical, radiation induced crosslinking. Another non-typical analytical method, the diffuse reflected light spectrophotometry (DRS) is applied to irradiated elastomers, showing the radiation induced chemical reactions.
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The discussion of chemical reactions caused by ionizing radiation is started, as usual, with the nature of the object which absorbs the energy. First, the composition (CO2 = 95.3%) and density of martian atmosphere is discussed; the latter is low, 120 times smaller than over the Earth atid does not protect the surface of Mars from ionizing radiations. The atmosphere over the Earth secures the shield equivalent to 3 m of concrete, with many positive consequences for the Life on Earth. In addition, high energy protons from the Sun are diverted magnetically around the Earth, and that is not the case around the Mars. The radiolysis of Martian atmosphere starts with formation of CO2 as the primary product of single ionization spurs. The multi-ionization spurs can yield exotic carbon-oxygen compounds, not explored yet. Anyway, the radiolysis of martian atmosphere is completely different from the case of Earth, where the primary product is N* ion-radical. The lack of water vapor over Mars prevents the formation of an analogue to acid rains, and of creation of many other compounds. The most interesting feature of Martian regolith is the possibility of the presence of hydrated minerals, which could have been formed milliards years ago, when (probably) water was present on Mars. Water present in the crystalline lattice undergoes only limited radiolysis, as it is known from the case of concrete, produced as biological shield build on Earth, around the sources of ionizing radiation. Formation of natural hydrated silicates on Mars was possible, therefore survival of traces of H2O on Mars is possible. However, this kind of water cannot be recovered easily, to be used by Mars explorers. The interface of the atmosphere and the regolith is probably the site of many chemical reactions. Very intensive UV, which includes part of the vacuum UV, can cause reduction of carbon dioxide to methane, recently discovered in traces over Mars, hopefully, but erroneously connected, in the mode of wishful thinking, to the Life. Minerals like sodalite, discovered on Mars can contribute as reagents in the mentioned reaction, and could be the source of hydrogen. Conclusions are dedicated to questions of the live organisms connected with exploration of Mars; from microorganisms, comparatively resistant to ionizing radiation, to human beings, considered not to be fit to manned flight, survival on Mars and return to Earth. The genius of Mankind which is able to create effective means of exploration over the distance of millions of kilometers, should be a satisfaction more important than the extremely expensive presence of man or woman on Mars.
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Zbadano wpływ polarności uwodornionego kauczuku butadienowo-akrylonitrylowego (HNBR) na procesy jego sieciowania i degradacji radiacyjnej. Różniące się zawartością (34, 39, 43 % mas.) związanego akrylonitrylu (AN) próbki HNBR (odpowiednio oznaczone symbolami H34, H39 i H43) poddano działaniu promieniowania elektronowego o mocy 10 MeV dawką od 20 do 300 kGy. Oznaczono stałe elastyczności Mooney'a-Rivlina (2C1N), zawartość zolu (S), wydajność sieciowania radiacyjnego (E) oraz dawkę żelowania (Dg). Stwierdzono, że HNBR ulega sieciowaniu radiacyjnemu, a gęstość jego sieci przestrzennej jest wprost proporcjonalna do dawki (D). Zawartość związanego AN nie wpływa na procesy sieciowania i degradacji badanych HNBR. Wykorzystując równanie Charlesby'ego-Pinnera [równanie (3)] wyznaczono stosunek aktów degradacji (p) do aktów sieciowania (q) i stwierdzono, że procesom sieciowania radiacyjnego HNBR towarzyszy umiarkowana degradacja łańcuchów (p/q = 0,05-0,10), zachodząca prawdopodobnie wg mechanizmu rozpadu b [równanie (4)]. Metodą spektroskopii z całkowitym wewnętrznym odbiciem promieniowania podczerwonego (IRS) określono względną intensywność pasma absorpcji przy 810 cm-1 odpowiadającego końcowym ugrupowaniom >C=CH2.
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Influence of polarity of hydrogenated butadiene-acrylonitrile rubber (HNBR) on its crosslinking and radiation degradation was investigated. HNBR samples differing in bounded acrylonitrile (AN) content (34, 39 or 43 wt. %) (denoted with the symbols H34, H39 and H43, respectively) (Table 1) were irradiated with 10 MeV electron beam. Doses varied from 20 to 300 kGy. The following properties have been determined: Mooney-Rivlin elasticity constant (2C1N - Fig. 2), sol content (S - Fig. 3 and 4), radiation crosslinking efficiency (E) and gel dose (Dg) (Table 2). It was found HNBR undergoes radiation crosslinking and its network density is directly proportional to the dose (D). Bounded acrylonitrile content does not influence the processes of HNBR crosslinking and degradation. Ratio of scission acts (p) and crosslinking acts (q) has been determined using Charlesby-Pinner equation [equation (3)]. It has been found that the process of HNBR radiation crosslinking was accompanied with moderate degradation of the chains (p/q = 0.05-0.10, Table 2) going probably according to b-scission mechanism. Relative intensity of absorption band at 810 cm-1 related to >C=CH2 end groups (Table 3) was determined by internal reflection spectroscopy (IRS).
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