Kucera J.,Research Center Rez Ltd. |
Kofronova K.,Police of the Czech Republic
Journal of Radioanalytical and Nuclear Chemistry | Year: 2011
Autopsy of 29-year old woman suspicious of committing suicide by the ingestion of As2O3 yielded contradictory findings. All pathological findings as well as clinical symptoms suggested acute poisoning, while a highly elevated As level of 26.4 μg g-1 in her hair collected at the autopsy, which was determined with inductively coupled plasma mass spectrometry indicated chronic poisoning. To elucidate this discrepancy, instrumental neutron activation analysis (INAA) with proven accuracy was performed of another set of sectioned hair samples. Levels of As found by INAA in the range of 0.16-0.26 μg g-1 excluded chronic poisoning, because the person died after approximately 14 h after the As2O 3 ingestion. Two reasons for the discordant As results obtained by ICP-MS and INAA are considered: (1) accidental, non-removed contamination of hair on the As2O3 ingestion; (2) erroneous performance of ICP-MS. © 2010 Akadémiai Kiadó, Budapest, Hungary. Source
Mikus J.M.,Research Center Rez Ltd.
Nuclear Engineering and Design | Year: 2014
Neutron flux non-uniformity and gradients of neutron current resulting in corresponding power (fission rate) distribution changes can represent root causes of the fuel failure. Such situation can be expected in vicinity of some core heterogeneities and construction materials. Since needed data cannot be obtained from nuclear power plant (NPP), results of some benchmark type experiments performed on light water, zero-power research reactor LR-0 were used for investigation of the above phenomenon. Attention was focused on determination of the spatial power distribution changes in fuel assemblies (FAs):Containing fuel rods (FRs) with Gd burnable absorber in WWER-440 and WWER-1000 type cores,Neighboring the core blanket and dummy steel assembly simulators on the periphery of the WWER-440 standard and low leakage type cores, resp.;Neighboring baffle in WWER-1000 type cores, andNeighboring control rod (CR) in WWER-440 type cores, namely (a) power peak in axial power distribution in periphery FRs of the adjacent FAs near the area between CR fuel part and butt joint to the CR absorbing part and (b) decrease in radial power distribution in FRs near CR absorbing part. An overview of relevant experimental results from reactor LR-0 and some information concerning leaking FAs on NPP Temelín are presented. Obtained data can be used for code validation and subsequently for the fuel failure occurrence investigation. © 2013 Elsevier B.V. Source
Zhu X.-K.,Research Center Rez Ltd. |
Leis B.N.,Research Center Rez Ltd.
International Journal of Pressure Vessels and Piping | Year: 2012
Accurate prediction of burst pressure plays a central role in engineering design and integrity assessment of oil and gas pipelines. Theoretical and empirical solutions for such prediction are evaluated in this paper relative to a burst pressure database comprising more than 100 tests covering a variety of pipeline steel grades and pipe sizes. Solutions considered include three based on plasticity theory for the end-capped, thin-walled, defect-free line pipe subjected to internal pressure in terms of the Tresca, von Mises, and ZL (or Zhu-Leis) criteria, one based on a cylindrical instability stress (CIS) concept, and a large group of analytical and empirical models previously evaluated by Law and Bowie (International Journal of Pressure Vessels and Piping, 84, 2007: 487-492). It is found that these models can be categorized into either a Tresca-family or a von Mises-family of solutions, except for those due to Margetson and Zhu-Leis models. The viability of predictions is measured via statistical analyses in terms of a mean error and its standard deviation. Consistent with an independent parallel evaluation using another large database, the Zhu-Leis solution is found best for predicting burst pressure, including consideration of strain hardening effects, while the Tresca strength solutions including Barlow, Maximum shear stress, Turner, and the ASME boiler code provide reasonably good predictions for the class of line-pipe steels with intermediate strain hardening response. © 2011 Elsevier Ltd. Source
Kost'Al M.,Research Center Rez Ltd. |
Cvachovec F.,University of Defence at Brno |
Rypar V.,Research Center Rez Ltd. |
Juricek V.,Research Center Rez Ltd.
Annals of Nuclear Energy | Year: 2012
The neutron fluence load on a reactor pressure vessel is an important physical quantity affecting material degradation and consequently reliable assessment of pressure vessel integrity and lifetime prolongation beyond designed conditions. This degradation is influenced by mixed neutron-photon source from the core periphery as well as by material parameters of the reactor pressure vessel. Computational procedures and experimental determination of neutron fluxes in the VVER-1000 mock-up internal structures as well as the results achieved are described in this paper. The calculation were performed with the MCNPX code with different nuclear data libraries. Nuclear data were processed using NJOY code. The neutron spectra measurements were performed with a two-parameter stilbene spectrometer. © 2011 Elsevier Ltd. All rights reserved. Source
Kostal M.,Research Center Rez Ltd. |
Kostal M.,Nuclear Research Institute Rez |
Rypar V.,Research Center Rez Ltd. |
Svadlenkova M.,Research Center Rez Ltd.
Nuclear Engineering and Design | Year: 2012
The pin power density distribution in reactor is an important quantity, necessary for the adequate assessment of fuel conditions and of core structures and pressure vessel radiation embrittlement as well. The paper shows the detailed comparison of calculated and experimentally determined pin by pin power distribution. To verify the reliability of measured data used for comparison with calculated data, the symmetrically located pins were measured. The calculations have been done with deterministic and Monte Carlo approach. The effect of different data libraries used for calculations are discussed as well. © 2011 Elsevier B.V. All rights reserved. Source