Measurement of \Gamma_{ee}(J/\psi)*Br(J/\psi->e^+e^-) and \Gamma_{ee}(J/\psi)*Br(J/\psi->\mu^+\mu^-)

The products of the electron width of the J/\psi meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron-positron collider. The results are \Gamma_{ee}(J/\psi)*Br(J/\psi->e^+e^-)=(0.3323\pm0.0064\pm0.0048) keV, \Gamma_{ee}(J/\psi)*Br(J/\psi->\mu^+\mu^-)=(0.3318\pm0.0052\pm0.0063) keV. Their combinations \Gamma_{ee}\times(\Gamma_{ee}+\Gamma_{\mu\mu})/\Gamma=(0.6641\pm0.0082\pm0.0100) keV, \Gamma_{ee}/\Gamma_{\mu\mu}=1.002\pm0.021\pm0.013 can be used to improve theaccuracy of the leptonic and full widths and test leptonic universality. Assuming e\mu universality and using the world average value of the lepton branching fraction, we also determine the leptonic \Gamma_{ll}=5.59\pm0.12 keV and total \Gamma=94.1\pm2.7 keV widths of the J/\psi meson.Comment: 7 pages, 6 figure

Search for narrow resonances in e+ e- annihilation between 1.85 and 3.1 GeV with the KEDR Detector

We report results of a search for narrow resonances in e+ e- annihilation at center-of-mass energies between 1.85 and 3.1 GeV performed with the KEDR detector at the VEPP-4M e+ e- collider. The upper limit on the leptonic width of a narrow resonance Gamma(R -> ee) Br(R -> hadr) < 120 eV has been obtained (at 90 % C.L.)

Measurement of main parameters of the \psi(2S) resonance

A high-precision determination of the main parameters of the \psi(2S) resonance has been performed with the KEDR detector at the VEPP-4M e^{+}e^{-} collider in three scans of the \psi(2S) -- \psi(3770) energy range. Fitting the energy dependence of the multihadron cross section in the vicinity of the \psi(2S) we obtained the mass value M = 3686.114 +- 0.007 +- 0.011 ^{+0.002}_{-0.012} MeV and the product of the electron partial width by the branching fraction into hadrons \Gamma_{ee}*B_{h} = 2.233 +- 0.015 +- 0.037 +- 0.020 keV. The third error quoted is an estimate of the model dependence of the result due to assumptions on the interference effects in the cross section of the single-photon e^{+}e^{-} annihilation to hadrons explicitly considered in this work. Implicitly, the same assumptions were employed to obtain the charmonium leptonic width and the absolute branching fractions in many experiments. Using the result presented and the world average values of the electron and hadron branching fractions, one obtains the electron partial width and the total width of the \psi(2S): \Gamma_{ee} =2.282 +- 0.015 +- 0.038 +- 0.021 keV, \Gamma = 296 +- 2 +- 8 +- 3 keV. These results are consistent with and more than two times more precise than any of the previous experiments

Dynamic stability of the VVER-1200 power unit

The paper presents the results of critical experiments to study the dynamic stability of a power unit with the VVER-1200 reactor conducted as part of the pre-commissioning activities at the pilot operation stage of Novovoronezh NPP II's unit 1. The following dynamic tests were conducted: – trip of one main feedwater pump (MFP) with no standby MFP starting to operate at the power level of 100% Nnom, involving a detailed analysis of the variation in the process parameters of such mode and the process dynamics, and an assessment of the test results on a full-scale simulator; – trip of one out of four reactor coolant pump sets (RCPS) in operation at the power level of 100% Nnom and the reactor plant safety assessment in the context of the reactor core thermal reliability; – turbine generator (TG) load shedding to the auxiliary level with assessments for the behavior of the key reactor plant characteristics. The paper presents records for transients and safety-related process parameters, and describes the operation of the unit components and essential controls in the dynamic test process. A conclusion is made based on an analysis of the test results that the VVER-1200 unit has a high dynamic stability. The results of the dynamic stability studies for unit 1 of Novovoronezh II make it possible to provide a number of recommendations for further designs, including specifically the following: – accelerated warning protection (AWP) should be used instead of power reduction and limiting for modes with tripped main feedwater pumps; – generator-grid timing devices should be used for modes with the unit operating for auxiliary power supply; – Russian-developed software and hardware tools should be fully switched to in implementing both normal operation and safety control systems, since the adjustment of protection and interlocking algorithms used in the AREVA software and hardware package introduced at Novovoronezh II requires the developer's authorization which involves substantial time and financial expenditures

New generation first-of-the kind unit – VVER-1200 design features

The paper is concerned with the commissioning of the new generation NPP-2006 power unit with the VVER-1200 reactor. A comparison is made between the characteristics of the new NvNPP II-1 and commercial VVER-1000 power units (B-320). Some design and circuit solutions used in the NPP-2006 project were described, which made it possible to increase the installed capacity of the power unit, which was achieved, in particular, by increasing the pressure of the primary circuit by 0.5 MPa and the pressure in the steam generators by 0.6 MPa, and also by increasing the capacity of the main circulation pumps by 2000 m3/h. The main differences in the equipment and composition of passive and active safety systems of the NPP-2006 power unit are considered. A brief description of the safety systems first applied at Russian power units is given, e.g., a two-channel structure of active safety systems with redundant emergency pumps in each channel, a double containment, a core melt localization device, a passive heat removal system, etc. Due to the increased number of BRU-Ks, it was possible to increase their performance from 15 to 3 s, which significantly improved the maneuverability of the power unit in abnormal conditions. The structure of the APCS is considered, which is applied in the NPP-2006 project, using programmable technology based on the TELEPERM XS platform. The peculiarities of the power unit commissioning are analyzed, problematic issues that have arisen at various stages of the construction are revealed, some data on the tests carried out and the results of these tests are given. Finally, an analysis is made of some design drawbacks revealed during the construction and commissioning of the power unit, an evaluation of the project was made, and proposals were formulated to finalize the VVER-1200 project for consideration in the subsequent NPP projects