Risk-based method for substantiating reduction of pressure of hydraulic strength tests and its application on steam line of nuclear power plant with WWER (PWR) reactor plant

Hydraulic tests are used in various sectors of the national economy to check the strength and tightness of vessels and pipelines, their parts and assembly units loaded with pressure. The hydraulic test pressure is a calculated value and is determined on the basis of regulatory documentation for the relevant control objects. Analysis of current trends in the field of hydraulic testing both in the Russian Federation and abroad has shown a trend to reduce the damageability of test objects by choosing the most optimal hydraulic test pressure. The main purpose of the research was to reduce the operational damage to equipment and pipelines of nuclear power plants by reducing the pressure of hydraulic strength tests during maintenance. The research is based on probability theory, mathematical statistics, strength physics and fracture mechanics, taking into account the possibility of occasional discontinuities or defects that might be observed in operation. The method is based on a risk-based approach, which makes it possible to determine the permissible risk variation based on recommendations on the safety of nuclear power plants in the Russian Federation. The objects of research are the equipment and pipelines of nuclear power plants. The result of the research is the development of a method substantiating the reduction of the pressure of hydraulic strength tests for equipment and pipelines of nuclear power plants based on a risk-based approach. The developed method can be used by organizations involved in the production of electricity (at nuclear or thermal power plants), transportation of oil, gas or other substances, at facilities where pipelines are an essential part of their structures, affecting the reliability and efficiency of operation of these facilities. 

1. Getman A. F. Theories and technologies for ensuring the strength of technical objects. Nestor-Istoriya 2019; 632. (In Russ.)

2. Federal norms and rules in the field of nuclear energy use «Rules for the design and safe operation of equipment and pipelines of nuclear power plants» (NP-089-15). Rostechnadzor 2015. (In Russ.)

3. Kuzmin D. A., Kuzmichevskiy A. Yu., Vertashenok M. V. Investigation of the probability of existence of defects with a size exceeding the allowed value. Structural Mechanics of Engineering Constructions and Buildings 2020; 16 (5): 414 – 423. (In Russ.)

4. Kuzmin D. A., Kuzmichevskiy A. Yu. The method for calculating the probability of brittle destruction of NPP equipment in different operating modes with postulated defectiveness. Safety and Reliability of Power Industry. 2021; 14 (1): 34–39. (In Russ.)

5. Kuzmin D. A. Study of the residual imperfections using methods of probability theory. Industrial laboratory. Diagnostics of materials. 2021; 87 (9): 44–49. (In Russ.)

6. Federal norms and rules in the field of nuclear energy use «Rules for control of base metal, welded joints and deposited surfaces during the operation of equipment, pipelines and other elements of nuclear power plants» (NP-084-15). Rostechnadzor 2015. (In Russ.)

7. Kuzmin D. A., Vertashenok M. V., Tolkachev O. S. Determining the non-destructive testing frequency of the metal of slightly defective NPP equipment and pipelines based on a risk-oriented approach. Bulletin of MPEI 2023; 5: 122–128. (In Russ.)

8. Safety guide for the use of nuclear energy «Recommendations for the use of the risk-informative method when justifying risk-informative decisions related to the safety of a nuclear power plant unit” (RB-101- 16). Scientific and Engineering Centre for Nuclear and Radiation Safety 2016. (In Russ.)