Thermal-hydraulic design of PIPER-ONE loop", University of Pisa Report, DCMN - RL 003(82), Pisa (I)

The document constituted the second of a series of reports dealing with the design, the construction and the operation of the PIPER-ONE loop installed at the Scalbatraio Laboratory managed by DCMN (Dipartimento di Costruzioni Meccaniche e Nucleari – previously IIN, Istituto di Impianti Nucleari) of University of Pisa. PIPER-ONE was built in Italy as a consequence of the Three-Mile accident (1979): it aimed at simulating the Boiling Water Reactor (BWR) performance following Small Break Loss of Coolant Accidents (SBLOCA). The natural circulation which occurs between down-comer and core into the vessel constitutes the reference thermal-hydraulic phenomenon which needed to be simulated. The concerned document allowed the finalization of the thermal-hydraulic design which was consistent with the available budget. At the end of the process documented in the current report, a 4X4 fuel bundle full height was confirmed (following the initial evaluation) leading to an about 15 m high loop. Full pressure, full temperature and full linear heat power (for the nuclear fuel rod simulators) scales were also confirmed. The PIPER-ONE loop was used for an International Standard Problem (ISP) by Organization for Economic Cooperation and Development (OECD) / Nuclear Energy Agency (NEA) / Committee on the Safety of Nuclear Installations (CSNI) during the middle of 80’s. The design and the operation of the loop constituted a milestone achievement in the area of nuclear thermal-hydraulics with main reference to the scaling.