Structure Level Design

DOESTD107393

Design Requirement: Relief valve abc pressure setting of 165 psig and flow rate of I

gpm.

Design Basis: Parameters must meet ASME Section III, Section 7000 code requirements.

Per code, pressure equals piping design pressure (ref. ef). Flow rate must be sufficient to

prevent a pressure greater than 110 percent of the design pressure due to thermal

expansion and leakage through the reactor vessel isolation valves. (ref. yz)

Design Requirement: Miniflow bypass valve pqr must open in 4 seconds.

Design Basis: 4 seconds is the desired opening time. The valve is designed to open as

fast as practicable to minimize the time that the pump operates deadheaded. Valve and

bypass piping are specified as 4 inch to pass pump miniflow requirement (ref. st). Past

experience has demonstrated that vendors can supply fast opening valves with stem

stroke rates of I inch per second. Hence, a 4 second stroke time for this 4 inch valve was

selected. The engineering analysis indicates that up to 8 seconds is acceptable (i.e., 4

seconds of design margin is built into the design requirement). (Note: ref. pq).

Structure Level Design

Design Requirement: Lateral load resisting system elements must be designed to

withstand 100 mph wind pressures.

Design Basis: The lateral load resisting system provides stability to the structure under

wind loading. A 100 mph wind velocity was selected according to ANSI A58.1 based on a

review of the geographical location of the structure. (ref. bc)

II-B-8