Abstract
This paper describes the development of a new computer code called Leak Analysis of Piping – Oak Ridge (LEAPOR) which calculates estimates for the leakage rate of water escaping from postulated through-wall cracks in a piping segment of a nuclear power plant cooling water system. The ability of nuclear power plant control and safety systems to detect a piping leak prior to breakage is a fundamental requirement of the leak-before-break concept. The design and assessment of leak-detec¬tion systems, therefore, requires the determination of through-wall crack leakage rates covering a significant range of opera¬ting and flow conditions. For the primary use case of pressur¬ized water reactors, the coolant is subcooled liquid-phase water at high pressures and temp-eratures, and the leakage flow re¬gimes can range from adiabatic flow boiling (“flashing”) with non-equilibrium vapor generation inside the crack to orifice flow of a subcooled liquid with vapor generation occurring outside of the pipe. The thermohydraulic Henry-Fauske model (with extensions) for non-equilibrium flashing flow through “tight cracks” has been implemented into LEAPOR.
A primary driver in the development of LEAPOR has been that its Software Quality Assurance (SQA) requirements inclu-ded evaluations for correctness, consistency, complete¬ness, ac-curacy, source code readability, and testability. The new code should be prepared to successfully meet the criteria of formal SQA audits. The attributes of maintainability, portability, and extensibility also informed LEAPOR’s layered software archi-tectural design.
The paper presents the results of verification and validation studies carried out with LEAPOR where verification by bench¬mark comparisons to the results of an independently developed leak rate code and validation against experimental data are described.
