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Engineering Services and Support of QA: Application and enhancement of TRACE model


  • Employer:
    Gösgen Nuclear Power Plant
  • Implementation period:
    april 2019 – october 2019


The Gösgen Nuclear Power Plant (in German Kernkraftwerk Gösgen, abbreviated in KKG) is located in the Däniken municipality (canton of Solothurn, Switzerland) on a loop of the Aar river. It is operated by the public-private Kernkraftwerk Gösgen-Däniken AG.

The KKG has a pressurized water reactor designed by the German Kraftwerk Union AG, a then subsidiary of Siemens AG, then Areva NP and now part of Framatom. It contains 177 fuel assemblies, 48 of which are equipped with control elements. Each fuel assembly can hold up to 225 rods, but only 205 (204 for the MOX ones) are occupied by the fuel rods. The remaining 20 channels are reserved to the control rods. Rated parameters of the reactor installation are 324 ⁰C and 153 bars. The thermal power is 3002 MW (3062 MW for 104 % power).

The reactor installation has three primary side loops. The three steam generators of vertical type transfer the heat to the secondary coolant loop at 65 bar and 280 C. The turbine is composed of a high-pressure and three low-pressure units. It generates a net electric power of 970 MW that is delivered to the 400 kV power grid.


The main goal of the project is performance of series of deterministic safety analyses related to KKG TRACE model enhancement in different aspects. Three main tasks are included as follows:

  • Development and tests performance for 3 different core nodalization schemes. For each scheme different LOCA sizes are compared. 
  • Enhancement of Pressurizer model for simulation of scenarios with colling via Special Injection Boron System (TA81,82) with the performance of corresponding validation scenarios.
  • Enhancement of Secondary Side (steam generator) and Steam Dump to Condenser (SDC) models aiming better performance of steam parameters in case of SDC operation with the performance of corresponding validation scenarios.

All activities performed in the project aims at enhancement capabilities of the model to expand the model applicability.


The KKG model for design and beyond design (without core melt) basis accidents is developed with TRACE program and as for the purposes of this project are developed several case studies for core nodalization impact on the peak cladding temperature and the required CPU time. As an outcome of this task a core nodalization with 34 axial nodes and 7 channels has been adopted for the final model.

The Pressurizer model has been optimized in order to simulate scenario with injection of boron water from Special Injection Boron System (TA81,82) into the Pressurizer.

The changes in traduced in the Secondary Side and SDC models has enhanced significantly behaviour of the live steam in case of SDC operation.