PSI - Issue 17

Salatiel Pérez Montejo et al. / Procedia Structural Integrity 17 (2019) 123–130 Salatiel Pérez Montejo et al / Structural Integrity Procedia 00 (2019) 000 – 000

127

5

IR K

26.777

−

T RT

68.999 ( ln

) 160 −

−  =

(7)

1.223

100 IR K ksi inch = . In this case, the reference temperature of

The fracture toughness, which was considered, was

the material was 122.36 T RT F − =  . It was considered that the temperature shift is 90°F during 60 years of operation and Extended Power Uprates. Under this scope, the minimum adjusted temperature of reference is T =142.2+90 = 232 °F and the fracture toughness, calculated with equation 1, is 124.46 IR K ksi inch = . Table 2 shows the minimum adjusted temperature of reference “T” in a range of internal pressure between 200 psi and 1000 psi. The resultant pressure-temperature relationship is illustrated in Fig. 6.

Table 2 Minimum adjusted temperature of reference for diverse internal pressures. Pressure (psi) Temperature (°F) Pressure (psi) Temperature (°F)

Pressure (psi)

Temperature (°F)

1000 950 900 850 800 750

232 228 225 221 217 212

700 650 600 550 500 450

208 203 198 192 185 179

400 350 300 250 200

171 162 152 141 127

In order to compare these analytical results against the values obtained with the FEM, the fracture toughness is 2 IR IP It K K FEM K FEM = + (8) Besides, the temperature limit is evaluated with the following relationship. 2 26.777 68.99 ( ) 160 90 1.223 IP It K K T ln + − = − + (9)

4. Analyzed cases

Two transient conditions were evaluated, start up and shut down. The first one takes place in 4.5 hours. At the beginning, the temperature increases at 100°F/hr rate. Once that the temperature is 546°F, it is kept constant during 60 minutes (Fig. 3). This transient take place every 18 months, at the beginning and the end of every refueling outage (López Grijalba, 2018).

Fig. 3. Variation of the pressure and temperature during the start-up of the reactor.

The second transient is related with the shut down and cool down of the reactor. There is a gradual variation of the