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Technical Investigation of NTEK’s CHPP-3 Accident Completed


The commission formed by Rostechnadzor to investigate the technical causes of the accident at the hazardous production facility Fuel Facilities of CHPP-3 of JSC Norilsk and Taimyr Energy Company has completed its work.

Based on the examination of the design and technical documentation, inspection of the scene, interviews of eyewitnesses and officials, as well as the conclusion of the expert group, the commission has established the following causes of the accident.

Technical causes:
- the cause of the depressurization of the vertical welded steel tank RVS-30000 (tech. No. 5) with the subsequent outflow of diesel fuel in the amount of 25,324.567m3 (21,163.300 t at the accepted density of 812.5 kg/m3) was the insufficient bearing capacity of the raft foundation and reinforced concrete piles, which caused an excess of the permissible forces with the subsequent chain destruction of 33 piles located along the contour and inside the pile space, as well as the destruction of the monolithic reinforced concrete base and its subsidence up to 1.5 m under the bottom of the tank.

Organizational causes:
- flaws in the design of the reinforced concrete pile foundation due to the low level of design work;

- defects in the construction process: beyond-design centering errors of transferring the load from the grillage to the piles, the absence of transverse reinforcement in the monolithic capping of the pile heads, the presence of dry sludge at the bottom of the well under the end of the pile, and the fact that up to 30% of the piles did not rest upon the rock base significantly worsened the stress-strain state of the reinforced concrete piled substructure. The presence of “weak” soils under the end of the piles caused a redistribution of efforts in the structures of the piled substructure, and the load on a number of the piles significantly exceeded their bearing capacity.

Other causes:
- poor quality control of the reliable and safe operation of the structures (the pile substructure of the tank tech. No. 5) by the responsible persons: failure to assess the actual state of the foundation (pile substructure) to determine the compliance of the building structures with the design documentation and requirements of the regulatory documents, and failure to conduct an examination to assess the strength, stability and operational reliability, taking into account specific operating conditions;

- failure to observe the requirements when conducting the industrial safety review, namely: when conducting the industrial safety review No. 1495/2018-EPB in 2018, the expert organization LLC Safety in Industry did not assess the actual state of the foundation (pile substructure) of the RVS-30000 tank (tech. No. 5) to determine the compliance of the building structures with the design documentation and the requirements of the regulatory documents of the structures.

The results of the technical investigation are recorded in the report, which indicates the causes and circumstances of the accident, the violations of industrial safety requirements and the persons who committed the violations. The report describes the measures taken to confine and mitigate the consequences, and contains proposals for the prevention of similar accidents. The report was signed by the members of the commission, handed over to them, and submitted to state authorities on November 13, 2020.

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