Project

Engineering Services and Support of QA: Application and enhancement of TRACE model.
Extension of the TRACE Model for NPP Gösgen for MSLB and MB LOCA.

Goals of the project

The main goals of this project are, as follows: 

• Implementation of plant models (Main and GUI models) improvements and optimizations. 
• To present results from the calculations of two MSLB scenarios (with and without reactivity void curves application), which have been performed with the TRACE V5.0 computer code by applying the KKG plant model, and to compare them with the respective S-RELAP5 calculations;
• To present results from the calculations of MB LOCA and MSLB scenarios with application of the modified and optimised containment model, and to compare the containment performance against the respective MELSIM calculations. The two analysed scenarios (MB LOCA and MSLB) have been selected in order to maximize the energy released to the containment, so that the containment pressure could rise fast. 
• To describe the chronology of the main events during the accident progression. 
• To analyse the results and draw conclusions. 
• To graphically represent the main parameters from the respective calculations for the selected scenarios.

Scope of the project

The scope of the calculations covers the following scenarios: 

• Scenario 1: Double ended break of main steam line 1 before MSIV without reactivity void curves activation – this scenario is compared against S-RELAP5 calculation and is documented in detail.
• Scenario 2: Double ended break of main steam line 1 before MSIV with reactivity void curves activation – this scenario is compared against S-RELAP5 calculation and is documented in detail.
• Scenario 3: MB LOCA inside the containment from cold leg 2 (380 cm2) – this scenario is performed only for assessment of the upgraded containment model which is developed in the frame of the current project (aim is only containment pressure and temperature assessment). The results for containment performance are compared against MELSIM calculation and are documented in detail.
• Scenario 4: Single ended break of main steam line 1 inside the containment with reactivity void curves activation – this scenario is performed only for assessment of the upgraded containment model which is developed in the frame of the current project (aim is only containment pressure and temperature assessment). The results for containment performance are compared against MELSIM calculation and are documented in detail.

Outputs of the project

• Gaining insights from the comparison between TRACE and S-RELAP5 predictions for Main steam line break before MSIV1 with (Scenario 1) and without (Scenario 2) void curves reactivity feedback option.
• Assessment of the results for MB LOCA and MSLB: TRACE vs. MELSIM comparison for the containment response. 

Presentation of the good agreement between the results predicted by TRACE_KKG model against the results from MELSIM and S-RELAP5 models for the considered IE (see Figure 7 ÷ Figure 11).