Increase of technical specification containment operating temperature

Virginia Power has experienced some difficulty in operating below the technical specification maximum allowable containment temperature at the North Anna power station during the hottest part of the summer season. This is primarily due to the high service water temperature that was used to cool the containment. Other reasons cited for the high containment temperature are inadequate insulation around the primary system piping and inadequate air flow paths within the containment. In order to elevate the current limit of the North Anna containment operating temperature, a comprehensive containment analysis needs to be performed. Some of the major goals that were obtained in this evaluation include the following: (1) initial operating temperature was higher; (2) service water temperature was higher; (3) containment peak pressure design limit was satisfied; (4) containment peak temperature was lowered; (5) net positive suction head requirements were satisfied; (6) containment depressurization time was shortened; and (7) subatmospheric peak pressure satisfied. The results of this work have shown that the technical specification containment temperature can be increased to provide operation during the hottest summer months with minimum impact on plant equipment