METHODS AND MEANS FOR CONTROL OF NUCLEAR MATERIALS STATE OF PROTECTIVE BARRIERS AT NUCLEAR POWER PLANTS
Ключові слова:algebraic reconstructive passive tomography, CdZnTe-detectors, radiation sensors, protective barriers
The key problem of nuclear power - radiation safety - is solved by ensuring the reliability of protective barriers main objects technological process of nuclear power plants (NPP) operation: fuel rods, fuel assemblies (fuel assemblies), coolant transfer circuits, etc.
Radiation sensors of new generation created in this work and measuring systems based on them open previously unknown possibilities in solving problems of analyzing nuclear fuel, increasing the accuracy and efficiency of monitoring technological parameters and the state of protective barriers in nuclear power plants.
When analyzing existing radiation sensors, it was found that, due to their iterative nature, they have several disadvantages: their rate of convergence is low (moreover, their convergence in the general case has not been proven at all), respectively, counting time can be so great that the algorithm can be inapplicable in real time when performing regular technological operations; all algorithms use empirical starting parameters of the iterative process, on which convergence also strongly depends; in some cases, an unsuccessful choice of the parameter iterative process may increase counting time to values that are unacceptable in practice, and may cause a divergence of iterative process. However, main disadvantage of such algorithms should be considered as unsuitability for solving tomography problem in the case of a large number conditionality matrix weights of fuel elements.
The use of algebraic reconstructive passive tomography (ART) methods for reconstructing the image internal structure of fuel assemblies was proposed for the first time. For this purpose, a new algorithm for passive tomography of nuclear fuel has been developed using the example of the WWPR-1000, which uses the angular projection method of the fuel assembly's own radiation. Computer experiments on the tomography of this object showed that measuring the radiation intensity at 360 points of detector location relative to fuel assembly axis for two or more energy values of the gamma radiation references 134Cs isotope is optimal. In this case, the proposed ART method allows identifying defective fuel elements with a leakage level of more than 30% on reconstructed tomograms, as well as the absence of fuel elements in the fuel assembly. It has been proposed to replace ionization sensors with CdZnTe-detectors in a modern coolant flow control system.