Evaluation of instability of the metrological characteristics of research reactors measuring channels
Research reactors are used for research trials in the field of nuclear and neutron physics, radiation chemistry, for the production of radioactive isotopes for the study of the properties of materials, devices and equipment, in the fields of irradiated neutrons and gamma rays, as well as for the preparation of the educational process specialists of the nuclear industry and nuclear power plants.
Measuring channels which used at research reactors for control the process parameters should provide high precision.
The parameter that determines the quality of the functioning of the measuring channels, reflecting the unchanged during the time of its metrological characteristics are stable. Stability is the parameter that determines the quality of the functioning of the measuring channels and reflecting the immutability during the time their metrological characteristics. The quantitative estimation of the stability of the measurement channels is the instability of their metrological characteristics [1–3].
However, to date there is no single methodology of the study and evaluation of the instability of the metrological characteristics of measuring channels. The patterns of trend of the metrological characteristics of measuring channels are scarcely explored. All this determines the need to develop approaches and methods of assessment and prediction of instability of metrological characteristics of measuring channels. The limit of error (D) is the one of the main metrological characteristics.
The article discusses the problem of estimating the instability of error of measuring channels neutron power research reactors. The purpose of the work is to study the general laws of the trend of instability characteristics of measuring channels during the time and determining the main components of the loss of the desired signal in the evaluation of the instability of the metrological characteristics of measuring channels neutron power.
In the technical literature  to estimate the instability of metrological characteristics of measuring instruments are encouraged to use mathematical modeling, and in the normative document  is recommended to evaluate the instability of measuring instruments by finding their sensitivity function. However, such approaches do not allow us to estimate the effect of each individual factor influencing on the measuring channel error. It is therefore advisable to apply Taguchi methodology, which is based on the determination of the loss by dint of finding values the ratio «useful signal / noise».
Measuring channels of neutron power is one of the most exposed to changes instability. On the basis of the analysis of the causes of failures of measuring channels in article  concluded that the most unstable part of the measuring channel to the effects of influencing factors is the sensor (transducer).
The article identifies factors affecting the instability of error measuring channel neutron power and areas of preventive control an instability of error of measuring channels neutron power. In the article proposed use the methods of the Taguchi theory for assessing the instability of metrological characteristics of measuring channels.
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