PSI - Issue 22

Yaroslav Dubyk / Procedia Structural Integrity 22 (2019) 275–282

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Yaroslav Dubyk / Structural Integrity Procedia 00 (2019) 000 – 000

analysis a simplified form of FAD is used (see Fig. 2 (right)), were we take ultimate strength as critical. To distinguish load case, and for sake of conservatism a different safety coefficient were used:  “2” – for Normal Operating conditions  “1.5” – for Hydraulic test and Safety Shutdown Earthquake  “1” – for LOCA accidents - blast loading due to rupture of pipelines that are connected to the considered ones;

Fig. 2. (left) Fracture toughness, experimental data taken from Timofeev et al. (2000); (right) FAD for different operational conditions.

2.2. Loads Loads for NPPs, are divided according to operation conditions on Normal operation, Safe shutdown earthquake, Accident situation. For Accident situation several LOCA scenarios are considered, related to breaks of piping connected with Main Circulation Line, which can cause blast loading (water hammer). Deterministic stress analysis for the whole WWER primary circuit was conducted using special piping software “3D PipeMaster” (see Fig. 3). Weight (including weight of coolant and insulation), pressure, thermal constrains as well as friction components of loading were considered. According to the deterministic calculations, a most loaded zones of MCP are selected, see Table 2. Analysis of Table 2. shows that SSE slightly affects MCP, Blast loading have some bigger impact, but if we compare the loads increment with the FAD for the corresponding operational condition, it is obvious, that Normal operation is most significant case for probabilistic analysis. Thus, in further probabilistic calculations only normal operation conditions will be considered.

Table 2. Loads for MCP.

Load conditions

Pressure, MPa

Temperature, ° C

F x , kN 7616.9 7644.2 8416.7

M y , kNm

M z , kNm

Normal operation (NO)

15.6 15.6 15.6

320 320 320

695.1 944.7

3671.4 3695.8 3493.4

Safe Shutdown Earthquake (SSE)

Blast loadings (BL)

1356.9