Analysis of Existing Approaches to the Calculated Substantiation of the Reactor Support Elements Safe Operation

V. V. Inyushev1, A. S. Koliadiuk1, V. O. Posokh1, V. O. Dubkovskyi2

1SE “State Scientific Engineering Center for Control System and Emergency Response”, 64/56, Heroiv Stalinhradu ave., Kyiv, 04213, Ukraine
2Odessa National Polytechnic University,
1, Shevchenko ave., Odesa, 65044, Ukraine

DOI: doi.org/10.31717/2311-8253.19.3.5

Abstract

The analysis of documentation for the calculated substantiation of the reactor support elements safe operation, which are presented in the design documents and in the reports on the lifetime extension of the reactor support elements at the Ukrainian NPPs, has been carried out to ensure compliance with the current regulatory requirements and the correctness of the applied initial conditions.
It is established that design strength calculations have typical deviations from the current regulatory requirements, since they were performed in accordance with the norms and rules, which were in force in the 1970s. In addition, the design strength calculations do not take into account all force factors acting on the reactor support elements. There is also a terminology conflict between terms used in the design documents and in the current regulatory requirements.
Analysis of current approaches to the strength calculations of the reactor support elements, in particular in the framework of the lifetime extension of the reactor support elements, showed that in practice, the strength assessment of the reactor support elements is performed in an axisymmetric formulation. Meanwhile, a complex asymmetrical load from the main circulation pipelines is not considered, which does not allow to calculate correctly the stress-strain state of the reactor support elements.
As a conclusion, for the calculated substantiation of the reactor support elements long term safe operation it is considered necessary to develop advanced approaches for solving the stress-strain state tasks taking into account all the force interactions and correct modeling of the interaction between the individual structural elements.

Keywords: reactor support elements, assessing the technical condition, lifetime extension, calculated substantiation, applied initial conditions.

References

1. NP 306.099-2004. General requirements for the extension oftheNPP units operation beyond the design lifetime based on the results of periodic safety review. Approved by the Order of the State Committee for Nuclear Regulation of Ukraine on 26.11.2004 no. 181. (in Ukr.)

2. 1162.01.02.100 RR. Support ring 1162.0.02.100. Strength analysis. Moscow: Atomenergoexport, 1980, 70 p. (in Russ.)

3. Standards for strength analysis of reactors elements, steam generators, vessels and pipelines of nuclear power plants, experimental and research nuclear reactors and installations. Moscow: Metallurgiya, 1973, 408 p. (in Russ.)

4. MT-T.0.03.155-14. Methodology for reassigning the allowable number of loading cycles and assessing the technical condition based on strength analysis of thermomechanical equipment and pipelines under cyclic loads. Kyiv, NNEGC “Energoatom”, 2014, 30 p. (in Russ.)

6. МТ-Т.0.03.326-13. Methodology for calculational seismic analysis of operating NPPs elements within the seismic margin assessment method. Kyiv: NNEGC «Energoatom», 2013, 51 p. (in Russ.)

8. RG-B.0.03.179-13. Typical technological regulation for safe operation ofNPP units with WWER-1000 reactors. Kyiv, NNEGC “Energoatom”, 2014, 257 p. (in Russ.)

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Published
2019-11-31

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