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[en] Five far ultraviolet light sensitive (Uvs) strains - CL77, CL89, CL90, CL104 and CL105- were isolated from an auxotrophic strain of Streptomyces clavuligerus (ATCC 27064). When compared to their progenitor, strain CL7, all exhibited a changed mutagenic response to far ultraviolet light (FUV). Strains CL77 and CL104 failed to yield detectable mutants, whereas induced mutants were obtained in strains CL90 and CL89, but only at low FUV doses (up to 20 J m-2). Strain CL89 was hypermutable at these low doses relative to strain CL7. Strain CL105 gave an increased response in terms of mutants per surviving cell. Caffeine increased the FUV-induced mutation frequency at a particular FUV dose in strain CL7 by up to 3000%. All the Uvs strains showed an altered response to caffeine compared with strain CL7. (author)
Journal
Journal of General Microbiology; ISSN 0022-1287; 
; v. 128(pt.2); p. 381-385
; v. 128(pt.2); p. 381-385
[en] Conidia, derived from a strain of Aspergillus nidulans known to carry a specific chromosomal duplication, were irradiated. The duplicated segment had genetic markers, which, when eliminated from the genome, allowed the easy detection of deletion mutants. Survival curves derived following 15 MeV electron and γ-ray irradiation were characterised by the presence of an appreciable shoulder, whilst 50 kvp X-rays gave a much smaller shoulder. Irradiation with β-particles and α-particles gave rise to exponential survival curves. The RBE values for these radiations, based on the D37 value were for γ-rays, 1.0, 15 MeV electrons 1.0,50 kvp X-rays 1.9, β-particles 2.1 and α-particles 3.4. With the exception of γ-rays the radiations described were compared with respect to their ability to induce chromosomal deletions. When the number of deletants amongst survivors was plotted against dose, a linear relationship was found for electrons, X-rays and β-particles. The response recorded for α-particles was essentially linear but with a biphasic component. The RBE values for the radiations, based on a value of unity for 15 MeV electrons were as follows: X-rays 1.3, β-particles 0.8, α-particles above 7.5 krad 2.3 and below 7.5 krad 3.5 (Auth.)
Journal
Mutation Research; ISSN 0027-5107; ; v. 59(2); p. 167-177
; v. 59(2); p. 167-177
[en] There are nine commercial Magnox gas-cooled reactor power stations in the United Kingdom. Three of these stations have been shutdown and are being decommissioning, and plans have also been prepared for the eventual decommissioning of the remaining operational stations. The preferred strategy for the decommissioning of the Magnox power stations has been identified as 'Safestore' in which the decommissioning activities are carried out in a number of steps separated by quiescent periods of care and maintenance. The final clearance of the site could be deferred for up to 135 years following station shutdown so as to obtain maximum benefit from radioactive decay. The first step in the decommissioning strategy is to defuel the reactors and transport all spent and new fuel off the site. This work has been completed at all three shutdown stations. Decommissioning work is continuing on the three sites and has involved activities such as dismantling, decontamination, recycling and disposal of some plant and structures, and the preparation of others for retention on the site for a period of care and maintenance. Significant experience has been gained in the practical application of decommissioning, with successful technologies and processes being identified for a wide range of activities. For example, large and small metallic and concrete structures, some with complex geometries, have been successfully decontaminated. Also, the reactors have been prepared for a long period of care and maintenance, with instrumentation and sampling systems having been installed to monitor their continuing integrity. All of this work has been done under careful safety, technical, and financial control. (author)
Source
International Atomic Energy Agency, Vienna (Austria); 314 p; ISSN 1011-4289; ; Sep 1998; p. 71-83; Technical committee meeting on technologies for gas cooled reactor decommissioning, fuel storage and waste disposal; Juelich (Germany); 8-10 Sep 1997; 3 refs, 7 figs
; Sep 1998; p. 71-83; Technical committee meeting on technologies for gas cooled reactor decommissioning, fuel storage and waste disposal; Juelich (Germany); 8-10 Sep 1997; 3 refs, 7 figs
[en] Magnox Electric is the U.K. government-owned utility that is responsible for nine commercial Magnox nuclear power stations. The stations were commissioned between 1962 and 1971, each having twin gas-cooled, graphite-moderated reactors. Three stations (Berkeley, Hunterston A, and Trawsfynydd) were shut down between 1989 and 1993, and they are being decommissioned in accordance with the preferred SAFSTOR strategy. The six reactors have been defueled, and extensive dismantling and decontamination have already been carried out
Journal
[en] The motions of neutron absorbing atoms in chemical compounds can be studied by measuring the shape of neutron resonance absorption lines. If the independence of nuclear and atomic motions is assumed, the observed shape of a line is given by a convolution of a Breit-Wigner function with a scattering law which represents the motions of the atoms composing the sample. The scattering law is observed in this work with a resolution function equal to the natural width of the resonance. Although this is usually much wider than the experimental resolution of conventional scattering experiments, this method is, nevertheless, worthwhile because it has two advantages over the conventional one: (1) There are negligible interference effects in the observed quantity, (2) The motion of one atom (the species showing the resonance) can be observed in a compound containing many other atoms. Since the scattering law function is non-symmetrical, the measured effect will be seen as an asymmetry in line shape. Also, the effect should be more significant for oxides than metals since the kinetic energy per atom is greater for the former, leading to a broader scattering law. Measurements of line shapes have been made with the Dido fast chopper and the measured resonance lines are compared between Ta and Ta2O5 ; and Hf and HtO2. A detailed calculation of line shape has also been made for each case from an assumed frequency function and using the methods of EGELSTAPF and SCHOFIELD (NucLSci. Engng) with the programmes LEAP and LINESHAPE written by McLatchie. Finally, conclusions derived by this technique are compared with those obtained by conventional neutron scattering methods. (author)
[fr]
On peut etudier les mouvements des atomes absorbant des neutrons dans les composes chimiques en mesurant la forme des raies d'absorption resonante des neutrons. Si on admet que les mouvements nucleaires et atomiques sont in- dependants, la forme d'une raie peut s'exprimer au moyen de la convolution d'une fonction de Breit-Wigner avec une loi''de diffusion qui represente les mouvements des atomes composant l'echantillon. Les auteurs ont constate que la fonction de resolution de la loi de diffusion est egale a la largeur naturelle de la resonance. Bien que cette resolution soit d'ordinaire superieure a celle qui est obtenue dans les experiences de diffusion classique, la methode employee est quand meme utile car elle presente, sur les methodes habituelles, les avantages suivants : 1. Les effets d'interferences sont negligeables dans les quantites observees ; 2. Le mouvement d'un atome (de l'espece presentant une resonance) peut etre observe dans un compose contenant plusieurs autres atomes. La fonction de la loi de diffusion n'etant pas symetrique, l'effect mesure se traduira par une asymetrie dans la forme de la raie. En outre, l'effet devrait etre plus marque pour les oxydes que dans les metaux etant donne que l'energie cinetique par atome est superieure dans les oxydes, ce qui donne lieu a une loi de diffusion plus large. Les auteurs ont mesure les formes spectrales a l'aide du selecteur mecanique rapide du reacteur Dido et compare les raies de resonance mesurees entre Ta et Ta2O5 ainsi qu'entre Hf et HfO2. Ils ont aussi procede a un calcul detaille de la forme des raies dans chacun des cas, en se fondant sur une fonction de frequence hypothetique et en employant la methode d'Egelstaff et Schofield dans les programmes LEAP et LINESHAPE etablis par McLatchie. Enfin, ils comparent les conclusions que l'on peut tirer de cette technique a celles que l'on obtient a partir des methodes de diffusion neutronique classique. (author)[es]
Los movimientos de los atomos que absorben neutrones en compuestos quimicos pueden estudiarse midiendo la forma de las rayas de absorcion de neutrones por resonancia. Si se supone que los movimientos nucleares y atomicos son independientes, la forma observada de una raya viene dada pot la convolucion de una funcion Breit-Wigner con una ley de dispersion que representa los movimientos de lois atomos que componen la muestra. En este trabajo, la ley de dispersion se obseiva con una funcion resolutiva igual a la amplitud natural de la resonancia. Si bien esta suele ser mucho mayor que el poder de resolucion alcanzado en los experimentos corrientes de dispersion, este metodo es util porque respecto del tradicional presenta dos ventajas:1. Los efectos de interferencia en la cantidad observada son despreciables; 2. El movimiento de un atomo (la especie que presenta la resonancia) puede observarse en un compuesto que contenga muchos otros atomos. Como la funcion de Ja ley de dispersion carece de asimetria, el efecto medido se observa como asimetria en la forma de la raya. Asimismo, el efecto debe ser mas marcado en los oxidos que en los metales, dado que la energia cinetica por atomo es mayot en los primeros y, como consecuencia, la ley de dispersion es mas amplia. Los autores han efectuado mediciones de la forma de las rayas con el selector mecanico rapido del reactor Dido y comparan entre si las rayas de resonancia medidas en el caso del Ta y del Ta2O5, y en el caso del Hf y del HfO2. Tambien han realizado un calculo detallado de la forma de las rayas para cada caso utilizando una funcion hipotetica de frecuencia y los metodos de Egelstaff y Schofield (Nuclear Science and Engineering), asi como los programas LEAP y LINESHAPE elaborados por McLatchie. Por ultimo, comparan las conclusiones obtenidas por este procedimiento con las deducidas conforme a los metodos corrientes de dispersion heutronica. (author)Source
International Atomic Energy Agency, Vienna (Austria); United Nations Educational, Scientific and Cultural Organization, Paris (France); 360 p; Jan 1963; p. 183-197; Symposium on Inelastic Scattering of Neutrons in Solids and Liquids; Chalk River (Canada); 10-14 Sep 1962; ISSN 0074-1884; ; Abstract also available in Russian; 7 figs., 11 refs.
; Abstract also available in Russian; 7 figs., 11 refs.
[en] A genetically marked heterozygous diploid of Aspergillus nidulans was synthesized and the feasibility of using this system for the simultaneous estimation of radio-induced mitotic crossing-over and non-disjunction has been investigated. In the case of the latter, serious experimental problems have been encountered. Nevertheless, induction curves for non-disjunction with 15-MeV electrons, 50-kVp X-rays, β-particles and α-particles are presented showing an increase in non-disjunction with increasing LET. (Auth.)
Journal
Mutation Research; ISSN 0027-5107; ; v. 61(1); p. 29-36
; v. 61(1); p. 29-36
[en] The processing, packaging, transport and disposal of solid low level radioactive waste that arises at nuclear power stations has been undertaken using well established methods for many years. During 1985 it was recognised that there were a number of major changes that were likely to occur. A thorough review of all CEGB low level waste activities was therefore undertaken. As a result, a number of major developments were implemented in recognition of the identified future requirements. The review and the progress achieved with the developments are addressed in this paper. (author)
Source
British Nuclear Energy Society, London (UK); 356 p; ISBN 0 7277 1525 9; ; 1989; p. 13-18; British Nuclear Energy Society; London (UK); Radioactive waste management 2: international conference; Brighton (UK); 2-5 May 1989
; 1989; p. 13-18; British Nuclear Energy Society; London (UK); Radioactive waste management 2: international conference; Brighton (UK); 2-5 May 1989
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