The Committee on Energy of the National Assembly held an extended meeting at the "Chaira" PSHP, where the representatives of the people were informed in detail about the state of the plant. The results of the report of the Swiss company AF-Consult Switzerland AG (AFRY Schweiz AG) on the root cause of the accident with hydro unit (HA) 4 from the beginning of 2022 were also presented.
The Swiss company has carried out analysis and verification of activities during the operation and rehabilitation of facilities at the plant, computer modeling of the processes and examination of metal samples in a German laboratory. This was announced today by the Ministry of Energy.
The report indicates strong depreciation of key facilities from the hydro unit, emphasizing that the damage is atypical for similar type of facilities in the world practice. The original turbine design*, which created high local stresses, and cavitation (partial surface breakdown of the metal), which led to fatigue build-up in the material, were cited as the main causes of the accident. The cumulative impact of the above factors led to the occurrence of the accident.
The people's representatives were also acquainted with the scenarios and the Roadmap for introducing the "Chaira" PSHP into regular operation.
The estimated repair of hydro units 2 and 3 has a planned period of 12 months for each of them, and due to the technical specifics of the plant, the repair must be carried out in stages. The renovation of XA2 will begin in early 2024.
Intensive negotiations are being conducted with the original manufacturer for the restoration of XA1, which was shut down as a precaution due to established damage to the turbine equipment even before the rehabilitation began. XA4 requires the replacement of the entire turbine and the restoration will take longer - approximately 36 months from the signing of a contract with a selected contractor. Tender documentation for the selection of a contractor is currently being finalized.
The Minister of Energy Rumen Radev and the executive director of NEC Martin Georgiev took part in the meeting, and they introduced the people's representatives to the facility and the plans for the repair works.
*- For its time (the eighties of the 20th century), this was the optimal design of the turbine for the so-called zero (pilot) project of high-pressure PSHP. With the subsequent development of technology, better technical solutions appear.