No abstract available

[en] A rapid method for determination of iron-containing minerals affecting the indications of nuclear magnetic logging of oil wells is suggested. The method is based on application of nuclear gamma-resonance spectroscopy (NGRS). It is shown that for the rapid determination of iron content the measurement of Moessbauer γ-quanta nonresonance absorption values is more effective. Core samples from Romashkin oil deposit of Tatar ASSR are investigated. Absolute iron content can be determined both in the process of NGR spectrum obtaining and separately

No abstract available

[en] IFA-503 is the base irradiation experiment with the main objective to generate representative and comparative information about standard WWER-440 fuel with that of PWR rods. The rig carries two clusters with six rods in each. Each cluster holds three rods of each origin. The rod instrumentation includes 8 expansion thermometers, 4 fuel stack elongation detectors and 4 pressure sensors. Fuel pellets are hollow with a bore of 1.8 mm, except the two PWR rods with PFIEF instruments. Two pellet-clad gaps are used, .210 and .270 mm As of April '96 the test has reached a burnup of 6 MWd/kg UO₂. The preliminary results from the test indicate that the WWER fuel densities somewhat more than the PWR fuel. The centreline temperature measurements during the initial operation were in compliance with FTEMP2 code calculations. A slight steady increase in temperature with burnup is observed at isopower conditions for all rods. The rod internal pressure measurements show stable pressure readings with burnup since power levels is far below the threshold for fission gas release. The WWER rods show in general some higher pressure than the PWR rods. It is believed that this is due to the hollow fuel in WWER causing a higher temperature of the filler gas than in the PWR fuel rods which contain solid pellets. (author)

[en] The review deals with the methodological issues on performing in-pile experiments on determining critical parameters of water-cooled reactor fuel (rods ultimate heat load, rate of its changes) under various fuel burnup. Programs for testing fuel performance under power ramp conditions are described that are used by foreign research nuclear centers. Practical tests applilcation is illustrated by independent results of experimental researches

[en] Pressure history inside fuel element-cladding was experimentally investigated during their life tests at the MR reactor in constant and dynamic modes. N-1 alloy clad UO₂ fuel was irradiated. Length of fuel column amounted to 1003 mm. Fuel elements were filled with He at pressure of up to 0.1 MPa and tested for tightness. Pressure inside fuel cladding irradiated for 17000 h to 22 MWxday/kg(U) burnup increased from 0.2 to 3.0 MPa in hot fuel elements and from 0.1 to 1.1 MPa in cold ones. Pressure history can be conditionally separated into four periods: three-step increase of filling gases pressure with corresponding increases of reactor power during first hours of operation; incubation period (zone of stable pressure) at burnup from 0.5 to 1.0 MWxday/kg(U) conditioned with times of formation and saturation of intergranular pores; period of intense pressure growth at burnup from 3 to 8 MWxday/kg(U); decay of pressure growth at burnup above 8 MWxday/kg(U). It is concluded that gas pressure growth has a step profile with abrupt pressure increase during each start-up after reactor shut-down

No abstract available

[en] Basic programs on studying the behaviour of water cooled and moderated reactor fuel elements under unsteady energy release conditions in the regimes of fast power increase are described. Data on experimental investigation into the dependence of maximum admissible thermal loads on burnup for the sake of providing standard fuel element safe operation and preventing destruction due to mechanical fuel-cladding interaction are presented. Results of testing the advanced fuel elements with increased resistance to destruction are presented

[en] Measurement of gas pressure in fuel rods with uranium dioxide are conducted in water cooled loop of the MR reseach reactor till the maximal burnup of 33.4 MWxday/kg. Full elements with 6.5% enrichment, initial 10.42 g/cm³ fuel density and the ratio O/U = 2.001 are investigated. Fuel elements in initial state were filled with helium at 0.1 MPa pressure. Analysis of the obtained data enables to reveal 4 periods in pressure change: 1. release and partial absorption of process gases during the first hours of operation, 2. incubation period at rather low burnup, 3. period of increasing pressure growth rate and 4. the period of decreasing this value at sufficient burnup

[en] The purpose of the study is to reveal nuclear gamma resonance (NGR) spectra which allow to find out partially reversed natural chromium-spinelides. For the solution of the problem on cation distribution on nonequivalent positions of chromium-spinelides structure methods of experimental determining the electric field gradient sign and studying cation distribution on characteristic change of symmetry of separate structure positions on consequtive variation of samples composition are suggested. The NGR spectrum of partially reversed chromium-spenelide differs from the normal one of the same composition by smaller quadrupole splitting value ΔE for Fesub(B) sup(3+) and greater one for Fesub(A)sup(2+). These spectra peculiarities allow one in search for partially reversed samples to avoid difficulties of discovering weak intensity lines