PIPER-ONE research: measured initial and boundary conditions for OECD CSNI International Standard Problem 21 (ISP 21)

The document was prepared within the framework of the PIPER-ONE research. PIPER-ONE loop was 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 describes the Boundary and Initial Conditions measured during the ISP-21 experiment and supplements the information provided to participants of the ISP 21 Workshop (held in Marina di Grosseto in 1985). . The International Standard Problem 21 (ISP 21) by Organization for Economic Cooperation and Development (OECD) / Nuclear Energy Agency (NEA) / Committee on the Safety of Nuclear Installations (CSNI) was managed by UNIPI. It constituted a milestone achievement in the area of nuclear thermal-hydraulics with main reference to the scaling