Krško Nuclear Power Plant embarks on Safety Upgrade Program

The Krško Nuclear Power Plant or Nuklearna elektrarna Krško (NEK), is located in Slovenia, and generates about 40 percent of the country’s electricity production. It has decided to implement a Safety Upgrade Program to address the safety concerns highlighted by the Fukushima event. The three-phase program represents one of the most extensive responses of the nuclear industry to the Japanese incident which occurred eight years ago.

In the framework of the design modification “1024-BS-L Construction BB2 building” that is part of the “Safety Upgrade Project Phase 3” of NEK, Tractebel (TEF) requested technical assistance from Dynamis in carrying out the seismic SSI analyses of the BB2 building using SASSI 2010 software.

Dynamis Mission

The mission was to perform the seismic analyses of the BB2 building located in the Krško NPP, while taking into consideration soil-structure interaction. For this purpose, specialized software, SASSI2010 v.1.0, a system for analysis of soil-structure interaction developed by Farhang Ostadan, was used. SASSI consists of a number of interrelated computer program modules which can be used to solve a wide range of dynamic soil-structure interaction problems in two or three dimensions.  The soil consists of semi-infinite viscoelastic horizontal layers on a semi-infinite viscoelastic half-space.  The structure is modeled by a standard 3D finite element connected at nodal points.  The excavated soil for deeply embedded structures are modeled by standard 3D solid elements. The structure and the excavated soil have common nodes at the boundaries.

Before running the calculations, Dynamis was required to draw up a Project Quality Plan (PQP) in compliance and in alignment with Tractebel’s Project Quality Plan PQP) for this project. In particular, Tractebel audited Dynamis for conformity to the PQP to identify deviations and correctives actions and received approval from Ansaldo Nuclear, the Main Contractor of the Global EPC contract. Dynamis provided evidence of validation of SASSI2010 in accordance with the applicable QA standards of the project (ASME – NQA 1).