[en] Possibilities and limits of X-ray absorption spectroscopy for cation site description in silicate glasses and possible applications for complex glasses, like glass for fission product containment, are examined. In borosilicate glasses two types of sites are evidenced for actinides at the valence 4: Coordinance 6 sites with a narrow radial distribution for the distance An-0; higher coordination (7, 8 or more) with a wider and asymmetrical radial distribution. Proportion of low coordinance sites increases when cation size decreases (Th > Np). U and Np VI and V are characterized as actinyles with a chain 0-An-0 practically linear, coordinance in a plane perpendicular to this complex is probably 5. X-ray absorption spectroscopy allows an accurate description of actinide sites in fission product glasses

[en] The process for monitoring the wall of a chamber containing a radioactive liquid which emits uniformly gamma radiations consists of locating a gamma detector at the outer surface of the wall measurement zone, counting the number of photons emitted passing through the wall in a standard reference zone and using the result to deduce when there is a defect in the measurement zone. 7 figs

[en] This report deals with the assessment of the amount of radioactive wastes arising from hypothetic decommissioning of the power fast breeder reactor SUPER PHENIX 1. Following assumptions have been used: - Activities are produced through neutronic captures in materials, - The reactor has been run at full power for 30 years. - Results obtained assume a 2 years decay time after ultimate reactor shut down. The more active structures and components are situated along the core axis (core cover plug, diagrid, diagrid support...). Radially beyond the core are the lateral neutron shielding assemblies which reduce primary pump and intermediate heat exchanger activation. Main contributors arise from the following isotopes ⁵⁹Co, ⁵⁴Fe, ⁶²Ni. Stellite (about 50% of ⁵⁹ Co) coating of spherical seats on the props which the subassemblies are stuck in, and stellite coatings on diagrid-diagrid support seats, have a high maximum local volumic activity (about 10¹² and 10⁹ Bq/cm³) while 85% of the analysed 3000 steel tons, have an activity lower than 100Bq/g. Above the roof slab and outside the safety tank, structures and components are not active

[en] The DLS program has been developed at Interatom to solve shielding problems on fast breeder reactors (FBRs) easily and economically. An important option of this code is the use of diffusion theory in material-filled regions and the line-of-sight method in cavities. The geometry is modeled in r-z coordinates. The code was applied in shielding calculations for the first German fast research reactor KNK and the German prototype FBR SNR-300. The DLS program is currently being used in the shielding work for the European Fast Reactor (EFR), which is a project involving several European partners. The development of all national projects are included in the layout of the EFR, mainly the Superphenix (France), the Prototype Fast Reactor (United Kingdom) and the SNR (DeBeNe)

[en] This report is a part of the studies of nuclear installation decommissioning, which relates to fast breeder reactors of the European type. More precisely, it deals with the assessment of the amount of radioactive wastes arising from decommissioning. Activities are produced through neutronic captures in materials. In the following pages, radioactive wastes arising from the Super Phenix 1 reactor structure and component dismantling are described. The following assumptions have been used; the reactor has been run at full power for 30 years and results assume a 2 year decay time after ultimate reactor shut down. The more active structures and components are situated on the core axis (core cover plug, diagrid, diagrid-support....). Radially beyond the core are the lateral neutron shielding assemblies which reduce primary pump and intermediate heat exchanger activation. Main contributors arise from the following isotopes ⁵⁹Co, ⁵⁴Fe, ⁶²Ni. Stellite (about 50% of ⁵⁹Co) coating of spherical seats on the props which the subassemblies are stuck in, and stellite coatings on diagrid-diagrid/support seats, have a high maximum local volumic activity (about 10¹² and 10⁹ Bq/cm³). While 85% of the analysed 3000 tons of steel, have an activity lower than 100 Bq/g. Above the roof slab and outside the safety tank, structures and components are not active. (author)

[en] In the conception and realization studies of a LMFBR, the decommissioning aspects are not much taken in account. It appears that low cost and unsophisticated dispositions can notably facilitate these operations of decommissioning. The objective of this research consists in the identification of the conception and construction measures that can facilitate these operations. By priority we considerate the measures requiring low cost and low development study

[en] Anticipated assessment of offsite consequences resulting from an accidental release of radioactivity into the atmosphere is commonly made, for the 1-50 km range, by application of statistical treatments, based on meteorological records, to a set of dose-distance relationships previously calculated by means of the ALICE computer code for various weather conditions, release durations and exposure modes. Input data comprise population distribution around the site and weather data, the latter consisting of mean frequencies per angular sector for short release duration problems or of actual records to account for weather variability in the case of prolonged releases. Consequences are currently expressed in terms of complementary cumulative distribution functions for various dose levels. An application to a reference site is presented

[en] The evolution of FBR design in Europe shows that pool-type design will become the reference design for future FBR and the projected European Fast Reactor (EFR) is based on this concept. The identification of design features shows that the main contributors of the sodium and structures activity are the Co60 for gamma radiation source and low decay, Ni63, Nb94 and Ni59 for long time decay. So, the technical benefits of a Co content reduction are interesting for the high activated structures and for diagrid thimbles coating and we made proposals to lower Co content in steels or alloys and to substitute coatings. We identify measures which must facilitate both the sodium draining and the reactor block and internal cleaning: all which improve the gravity draining and the downing of the sodium flow make easier the penetration of cleaning products. The features, connected with the dismantling of the very activated internal structures, of the roof and of the lay-out, are mentioned. (author)

[en] In this paper calculations of neutron and gamma streaming through various penetrations in the plug and neutron shield of the sodium cooled fast reactor PEC, currently under construction, are described. The object of the calculations has been to verify the accessibility, 3 days after reactor shut-down, of the area directly above the reactor. (author)

No abstract available