Antioxidant activities of sulfated polysaccharides from brown and red seaweeds

The in vitro antioxidant activities of the following six sulfated polysaccharides were investigated: iota, kappa and lambda carrageenans, which are widely used in the food industry, fucoidan (homofucan) from the edible seaweed Fucus vesiculosus and fucans (heterofucans) F0.5 and F1.1 from the seaweed Padina gymnospora. With respect to the inhibition of superoxide radical formation, fucoidan had an IC50 (the half maximal inhibitory concentration) of 0.058 mg·mL−1, while the IC50 for the kappa, iota and lambda carrageenans were 0.112, 0.332 and 0.046 mg·mL−1, respectively. All of the samples had an inhibitory effect on the formation of hydroxyl radicals. The results of peroxidation tests showed that fucoidan had an IC50 of 1.250 mg·mL−1 and that the kappa, iota and lambda carrageenans had an IC50 of 2.753 and 2.338 and 0.323 mg·mL−1, respectively. Fucan fractions showed low antioxidant activity relative to fucoidan. These results clearly indicate the beneficial effect of algal polysaccharides as antioxidants

Radiolysis influence on low alloy steel atmospheric corrosion at 80°C

International audienceThe degradation of iron-based materials by atmospheric corrosion is a well-known problem thatmay have incidence, especially for the storage of radioactive nuclear wastes. It is of importanceto evaluate the damages due to this kind of corrosion within long time-periods. One parameterwhich can influence atmospheric corrosion in the case of storage container is irradiation. Asatmospheric corrosion happens when a water film condensates at the surface of a material,radiolysis of this water film in contact with air can have for consequence the formation of acid anoxidizing species which can modify the corrosion process.As a consequence the aim of this work is to evaluate the influence of γ-irradiation onatmospheric corrosion of low alloy steel. In this goal, an experiment, called CASIMIR, has beendeveloped. During this experiment, samples of low alloy steel have been introduced into smallstainless steel container. In these ones, two different media has been introduced. The firstmedium is a small quantity of water in order to fix a relative humidity (RH) of 100 %. Thesecond medium is a melt of KH$_2$PO$_4$/ K$_2$HPO$_4$in a small quantity of water corresponding to arelative humidity of about 70% at the surface of the samples. The small containers have beenintroduced in a heating system which enables to fix a temperature of 80°C. This system has beeninstalled in an irradiation pool with three $^{60}$Co sources which fix, according to the location of thestainless steel in the system, a dose rate of 80 Gy.h$^{-1}$ or 20 Gy.h$^{-1}$ at the surface of the low alloysteel samples.After six, nine and twelve months of corrosion in these conditions some samples were extractedof the experiment and analyzed by different methods. Gravimetry after desquamation of thecorrosion layer enables to measure total corroded thickness in function of RH, dose rate andtime. As show on figure 1, after 6 month of exposure, sample aged with a RH of 100% are morecorroded than the one aged at 70%. Moreover the dose rate does not have an effect on thecorroded thickness for 20 Gy.h$^{-1}$ whereas it increases corrosion when the dose rate is equal to 80Gy.h$^{-1}$. This result is confirmed for longer times. Gas analysis after corrosion experiment haveshown that for the higher corrosion rate, oxygen was totally consumed after 6 month and revealalso a production of hydrogen. Microscopical observations also confirm the influence of doserate on atmospheric corrosion.All the results show that dose rate does not influence atmospheric corrosion until a valuebetween 20 and 80 Gy.h$^{-1}$. For a dose rate up to these thresholds, irradiation increase corrosionrate on low alloy steel in presence of high values of relative humilities.6th International Works

Study of concrete radiation ageing

International audienceConcrete is a durable material which is a vital part of engineering barrier for radioactive waste disposal. In many concepts of low and intermediate level waste (e.g. the French concept) and in some cases even of high level waste, concrete is planned to be used for construction of containers carrying the primary packages of the immobilized waste. Therefore, it is needed to understand the effect of gamma irradiation on concrete with respect to its durability. A joint experimental program of Czech and French research organizations CVR and CEA respectively was started in order to study the changes in the properties of cementitious composites after their exposition to gamma irradiation. Samples of cement mortars, manufactured in CVR, were divided into two sets, each of them irradiated and characterized with both CVR and CEA facilities. Samples tested in CVR were exposed to cumulative doses of 1.6 to 1.8 et61655;106 Gy with doses from 0.5 to 4.5 kGy/h, while samples in Saclay were exposed to cumulative doses of 0.72 to 3.1et61655;106 Gy with doses 0.6, 1.6 and 2.6 kGy/h, respectively. Mechanical properties of irradiated mortars were then defined by ultrasonic measurement to obtain changes in Young modulus of elasticity and by classical loading to obtain changes of flexural and compressive strength. A comparison with non-irradiated samples maintained in same environment was done. Moreover, investigation of microscopic changes in the concrete structure was executed by scanning electron microscope.Comparison of all the results can be seen in the paper

US/French joint research program regarding the behavior of polymer base materials subjected to beta radiation: Volume 2, Phase-2a screening tests: (Final report)

As part of the ongoing joint NRC/CEA cooperative test program to investigate the relative effectiveness of beta and gamma irradiation to produce damage in polymer base materials, ethylene propylene rubber (EPR) specimens, in slab geometry, were exposed to Cobalt-60 gamma rays and accelerator produced electron beams. Specimens were irradiated and evaluated at research facilities in the US (Sandia National Laboratories) and France (Compagnie ORIS Industrie). These tests included several electron beam energies, sample thicknesses, exposure doses, and dose rates. Based on changes in the tensile properties, of the test specimens, results of these studies suggest that material damage resulting from electron and gamma irradiations can be correlated on the basis of absorbed radiation dose

US/French Joint Research Program regarding the behavior of polymer base materials subjected to beta radiation. Volume 1. Phase-1 normalization results

As part of the ongoing multi-year joint NRC/CEA international cooperative test program to investigate the dose-damage equivalence of gamma and beta radiation on polymer base materials, dosimetry and ethylene-propylene rubber (EPR) specimens were exchanged, irradiated, and evaluated for property changes at research facilities in the US (Sandia National Laboratories) and France (Compagnie ORIS Industrie). The purpose of this Phase-1 test series was to normalize and cross-correlate the results obtained by one research center to the other, in terms of exposure (1.0 MeV accelerated electrons and /sup 60/Co gammas) and postirradiation testing (ultimate elongation and tensile strength, hardness, and density) techniques. The dosimetry and material specimen results indicate good agreement between the two countries regarding the exposure conditions and postirradiation evaluation techniques employed

Creep and shrinkage of Intermediate Level Long Life containers concrete comparison between gamma-irradiated and non-irradiated material

International audienceMany of the facilities and structures involved in the radioactive waste repository call for reinforced concrete (RC) in their construction. RC is used for containers as well as for surface and deep geological structures. In this paper we will focus on concrete containers (about 2 cubic meter) which would receive 1 to 4 waste containers (steel or concrete waste packages) of Intermediate Level Waste Long Lived (ILW-LL). With regards to the present disposal concept these containers would be placed one above the others up to 4 levels in the repository cells. In such context, Andra has to demonstrate the continuous mechanical integrity of the structure all over the operating / reversibility period.Classical mechanical properties of this concrete, as compressive strength, tensile limit and Young modulus are well known in classical non irradiated environment and must be confirmed in irradiated environment. This present study deals with the assessment of creep, shrinkage and others physical properties both under and out gamma irradiation, the samples being at the same thermal and hydric conditions.Specific experiment has been developed to address these parameters using cylindrical concrete dedicated to creep measurement and prisms dedicated to shrinkage.Samples are split in two groups, half irradiated and half non-irradiated. Gamma-irradiation has been carried out at the dose level representative of such ILW-LL wastes ($\approx$30 Gy/h) during 8 months to reach a total dose near to 180 kGy in average.The results show only a very small dimensional differences between irradiated and non-irradiated concrete samples in the same order of magnitude both for creep and shrinkage samples. Irradiation at such dose does not induced significate mechanical deterioration of the cementitious material

Tests under irradiation of optical fibers and cables devoted to corium monitoring in case of severe accident in a Nuclear Power Plant

The DISCOMS project, which stands for “DIstributed Sensing for COrium Monitoring and Safety”, considers the potential of distributed sensing technologies, based on remote instrumentations and Optical Fiber Sensing cables embedded into the concrete floor under the reactor vessel, to monitor the status of this third barrier of confinement. This paper focuses on the selection and testing of singlemode (SM) optical fibers with limited RIA (Radiation Induced Attenuation) to be compliant with remote distributed instruments optical budgets, the ionizing radiation doses to sustain, and their reduction provided by the concrete basemat shielding. The tests aimed at exposing these fibers and the corresponding sensitive optical cables, to the irradiation doses expected during the normal operation of the reactor (up to 60 years for the European Pressurized Reactor), followed by a severe accident. Several gamma and mixed (neutron-gamma) irradiations were performed at CEA Saclay facilities: POSÉÏDON irradiator and ISIS reactor, up to a gamma cumulated dose of about 2 MGy and fast neutron fluence (E > 1 MeV) of 6 x 1015 n/cm2. The first gamma test permitted to assess the RIA at various optical wavelengths, and to select three radiation tolerant singlemode fibers (RIA < 5 dB/100 m, at 1550 nm operating wavelength). The second one was performed on voluminous strands of sensitive cables encapsulating the selected optical fibers, up to approximately the same accumulated dose, at two temperatures: 30°C and 80°C. A significant increase of the RIA, without any saturation tendency, appeared for fibers inserted into cables, correlated with the increase of the hydroxyl attenuation peak at 1380 nm. Molecular hydrogen generated by the radiolysis of compounds of the cable is at the origin of this phenomenon. A third gamma irradiation run permitted to measure the radiolytic hydrogen production yield of some compounds of a dedicated temperature cable sample. The efficiency of a carbon coating layer over the silica cladding, acting as a barrier against hydrogen diffusion, was also successfully confirmed. Finally, the efficiency of this carbon coating layer has also been tested under neutron irradiation, then qualified as a protection barrier against hydrogen diffusion in the optical fiber cores

Tests under irradiation of optical fibers and cables devoted to corium monitoring in case of severe accident in a Nuclear Power Plant

International audienceThe DISCOMS project, which stands for “DIstributed Sensing for COrium Monitoring and Safety”, considers the potential of distributed sensing technologies, based on remote instrumentations and Optical Fiber Sensing cables embedded into the concrete floor under the reactor vessel, to monitor the status of this third barrier of confinement. This paper focuses on the selection and testing of singlemode (SM) optical fibers with limited RIA (Radiation Induced Attenuation) to be compliant with remote distributed instruments optical budgets, the ionizing radiation doses to sustain, and their reduction provided by the concrete basemat shielding. The tests aimed at exposing these fibers and the corresponding sensitive optical cables, to the irradiation doses expected during the normal operation of the reactor (up to 60 years for the European Pressurized Reactor), followed by a severe accident. Several gamma and mixed (neutron-gamma) irradiations were performed at CEA Saclay facilities: POSÉÏDON irradiator and ISIS reactor, up to a gamma cumulated dose of about 2 MGy and fast neutron fluence (E > 1 MeV) of 6 x 10$^{15}$ n/cm$^2$ . The first gamma test permitted to assess the RIA at various optical wavelengths, and to select three radiation tolerant singlemode fibers (RIA < 5 dB/100 m, at 1550 nm operating wavelength). The second one was performed on voluminous strands of sensitive cables encapsulating the selected optical fibers, up to approximately the same accumulated dose, at two temperatures: 30°C and 80°C. A significant increase of the RIA, without any saturation tendency, appeared for fibers inserted into cables, correlated with the increase of the hydroxyl attenuation peak at 1380 nm. Molecular hydrogen generated by the radiolysis of compounds of the cable is at the origin of this phenomenon. A third gamma irradiation run permitted to measure the radiolytic hydrogen production yield of some compounds of a dedicated temperature cable sample. The efficiency of a carbon coating layer over the silica cladding, acting as a barrier against hydrogen diffusion, was also successfully confirmed. Finally, the efficiency of this carbon coating layer has also been tested under neutron irradiation, then qualified as a protection barrier against hydrogen diffusion in the optical fiber cores

Tests under irradiation of optical fibers and cables devoted to corium monitoring in case of severe accident in a Nuclear Power Plant

The DISCOMS project, which stands for “DIstributed Sensing for COrium Monitoring and Safety”, considers the potential of distributed sensing technologies, based on remote instrumentations and Optical Fiber Sensing cables embedded into the concrete floor under the reactor vessel, to monitor the status of this third barrier of confinement. This paper focuses on the selection and testing of singlemode (SM) optical fibers with limited RIA (Radiation Induced Attenuation) to be compliant with remote distributed instruments optical budgets, the ionizing radiation doses to sustain, and their reduction provided by the concrete basemat shielding. The tests aimed at exposing these fibers and the corresponding sensitive optical cables, to the irradiation doses expected during the normal operation of the reactor (up to 60 years for the European Pressurized Reactor), followed by a severe accident. Several gamma and mixed (neutron-gamma) irradiations were performed at CEA Saclay facilities: POSÉÏDON irradiator and ISIS reactor, up to a gamma cumulated dose of about 2 MGy and fast neutron fluence (E > 1 MeV) of 6 x 1015 n/cm2. The first gamma test permitted to assess the RIA at various optical wavelengths, and to select three radiation tolerant singlemode fibers (RIA < 5 dB/100 m, at 1550 nm operating wavelength). The second one was performed on voluminous strands of sensitive cables encapsulating the selected optical fibers, up to approximately the same accumulated dose, at two temperatures: 30°C and 80°C. A significant increase of the RIA, without any saturation tendency, appeared for fibers inserted into cables, correlated with the increase of the hydroxyl attenuation peak at 1380 nm. Molecular hydrogen generated by the radiolysis of compounds of the cable is at the origin of this phenomenon. A third gamma irradiation run permitted to measure the radiolytic hydrogen production yield of some compounds of a dedicated temperature cable sample. The efficiency of a carbon coating layer over the silica cladding, acting as a barrier against hydrogen diffusion, was also successfully confirmed. Finally, the efficiency of this carbon coating layer has also been tested under neutron irradiation, then qualified as a protection barrier against hydrogen diffusion in the optical fiber cores