[en] The present paper is devoted to post-irradiation examinations (PIE) of U-Gd fuel rods with different geometry of the fuel pellets irradiated as part of the VVER-1000 fuel assembly. As evidenced by their PIE data, they did not exhaust their service life based on the main parameters (geometrical dimensions, corrosion state, and release of fission product gases). (author)

[en] The presented material contains the data on change in form, corrosion state and mechanical properties of fuel rod claddings, change in fuel structure and release of gaseous fission products (GFP) under the cladding. The results of PIEs of the VVER-1000 fuel rods with the high burnup of fuel (average value is 72.3 MW·day/kgU and maximum is 75 MW·day/kgU) carried out in JSC 'SSC RIAR' show that by the basic operational characteristics the lifetime of fuel rods with such burnup of fuel is not exhausted. The state of fuel rods is characterized by following key parameters. The fuel-to-cladding gap on the most part of the fuel meat is absent. With the burnup growth, diameter of the fuel rod increases due to fuel meat swelling. In so doing, the reverse strain achieves the values of 0.40-0.47 %. Ridges on the cladding are formed practically along the entire length of the fuel meat, average height of ridges makes up 25 μm, maximum - 40 μm. At burnups exceeding 55 MW·day/kgU, the rate of the fuel rod elongation is less than at low and average burnups. So if within a burnup range of 20-55 MW·day/kgU, the rate of the fuel rod elongation makes up about 0.330mm per 1 MW·day/kgU, at burnups exceeding 55 MW·day/kgU it is only 0.085mm per 1 MW·day/kgU. Corrosion state of the claddings of fuel rods with high burnup of fuel is satisfactory. The oxide film, as a rule, is uniform, dense, without cracks and exfoliation, its thickness on the external surface does not exceed 13 μm, while on the internal surface - 15 μm. Hydrogenation is insignificant, mass fraction of hydrogen does not exceed 0.01 %. Interaction of fuel rods with spacer grids does not result in significant fretting-corrosion. Based of the results of tests, short-term mechanical properties of the claddings of fuel rods with high burnup of fuel remain at high level. The state of fuel is characterized by absence of the fuel-to-cladding gap on the most part of the fuel meat, fuel is tightly fixed to the cladding. Concentration and size of pores in the main part of the pellet section increase with the growth of burnup, the rim-layer the width of which changes from 20 up to 250 μm with the increase of burnup in the section from 55 up to 75 MW·day/kgU is formed at the periphery of the fuel pellet. Swelling of fuel at a local burnup of 75 MW·day/kgU achieves 4.7 %. The FGR intensifies and at a burnup of 71 MW·day/kgU achieve 6 %. (authors)

[en] The VVER type reactors are the basis of the Russia's nuclear power engineering and they will keep their leadership in the near future being exported to other foreign countries. Due to this, the improvement of their feasibility characteristics and competitiveness is an urgent task. In the lower part of the VVER 1000 fuel rod there is an E 110 alloy spacer. A VVER 1000 fuel column is fixed by a spring type stopper. As for the VVER 440 fuel rod, its fuel column is fixed by a split bushing stopper. The upper plugs are sealed by butt resistance welding (BRW 2); the lower plugs are sealed by BRW 2 (VVER 1000) and electron beam welding (EBW) (VVER 440). All the main indices that determine the VVER 1000 and VVER 440 core performance (geometry, corrosion state, mechanical properties, GFP release, etc) show that the lifetime of fuel rods achieved a burnup of 73MW day/kgU is not exhausted

No abstract available

[en] In this paper operation experience, results of investigated E365 alloy components of Balakovo NPP Unit 1 and Kalinin NPP unit 1 fuel assemblies are presented. Appearance, shape changes and geometric size, corrosion state of guide thimbles, angles and fuel rods, corrosion of fuel claddings are studied. At the end authors concluded that: I) E635 alloy corroborated its high operation reliability as fuel claddings and WWER-1000 FA components during 6 year service to the fuel burnup of 72MWd/kgU; II) Based on the results from the post-irradiation investigations of the fuel rods and other structural elements of WWER-1000 FAA, fabricated from E635 alloy, in terms of the basic operational characteristics, their resources after the 6 year operation cycle have not been exhausted; III) The geometrical parameters, corrosion states, tensile properties of items fabricated from fuel alloy did not attain the values that would prevent their further operation: 1) the elongations of the fuel rods at the mean burnups up to 66.2 MWd/kgU do not exceed 15 mm or < 0.4%; 2) decreases in fuel E635 alloy cladding diameters at the burnup of ∼ 60 MWd/kgU make up 0.01-0.02 mm; 3) the fuel-cladding gap is not closed in fuels having E635 alloy claddings at the burnup up to ∼ 72 MWd/kgU; 4) the elongation of CT in FAA as 6 years operated makes up 7.1 mm or 0.18%; 5) the elongations of the angles are within 7.4-8.5 mm (0.19-0.21%); 6) the elongation of GT in FAA after the operation time does not exceed 4.7 mm (0.11-0.12%); 7) the amount of the oxide coat densely adherent to the metal at the burnup up to ∼ 72 MWd/kgU does not exceed 80 μm and the hydrogen content is not more than 0.03% mass; the cladding retains the adequate ductility δt>4.9%; 8) the amount of the oxide coat at surface of GT and CT does not exceed 45 μm, the hydrogen content is <0.03% mass; 9) the oxide coat at the surfaces of the frame angles does not exceed 50 μm, the hydrogen content is <0.04% mass

[en] The paper studied the features of distribution of main heavy metals in the water-bottom sediments system in the Red River Delta (Vietnam). The tasks were to determine the flow of heavy metals, to study the adsorption processes of heavy metals in suspended matter and burial in bottom sediments. The studies were carried out during the main hydrological seasons of 2014 – 2016 years at 6 stations of main branches of the river for 8 basic heavy metals (Cu, Pb, Zn, Hg, Cd, As, Cr and Fe). Each year, the total flow of heavy metals entering the top of the delta was 98.8 thousand tons. The total flow of all heavy metals differed by hydrological seasons and by watercourses. In general, 1.76% - 16.25% of the flow of heavy metals accumulated throughout the year, the highest accumulation rates are for lead, iron and zinc. In the branches Ba Lat, Tra Ly, Ninh Co, due to the decrease in flow rates, an intensive process of the accumulation of suspended substances and sorbed heavy metals was observed. (paper)

[en] The results of trial operation of E110M alloy fuel rod claddings as part of TVS-2M type fuel assemblies in unit 2 of Balakovo NPP VVER-1000 reactor during 3 18-month-long cycles were analyzed. Inspection data of three experimental TVS-2M, which reached a burn-up of (55-60) MW·day/kgU, testifies to the high shaping and corrosion resistance of E110M alloy in comparison with other cladding materials. High characteristics of the E110M alloy are confirmed by tests results of experimental fuel rods in the Halden reactor under conditions in water-chemical regime (WCR) PWR in comparison with E110opt, E125 and E635M alloys. Irradiation was carried out at a design temperature of 351 ºC in lithium WCR (up to 10 ppm Li) with steam content up to 2.0% by volume and a duration of 907 effective days with a burn-up of 60.55 MW·day/kgU. This report presents the results of non-destructive tests in SC «SSC RIAR» and Halden: oxide film growth kinetics on fuel rods and samples received by eddy current method, the state of their outer surface from visual observations and data on diameter measurements and elongation of fuel rods in the process of reactor tests. Destructive post-irradiation examinations according to metallography confirm the results of eddy current measurements of the oxide film thickness on studied alloys fuel rod claddings. The results of post-irradiation examinations in SC «SSC RIAR» and Halden are compared with data from non-reactor examinations of fuel rod cladding samples. Obtained results show that the best combination of properties for fuel claddings under irradiation in a VVER conditions and in a hard lithium water-chemical mode of Halden-reactor are demonstrated by E110opt and E110M alloys. At the same time, E110M alloy has an advantage over E110opt in creep resistance, having the same corrosion resistance. Keywords: E110M Alloy, Fuel Rod Cladding, Non-Destructive Tests, Destructive Post-Irradiation Examinations

No abstract available