Analysis by RELAP4/MOD6 code of the reference transient in the design of PIPER-ONE loop" (in Italian), University of Pisa Report, IIN - RP 492(81), Pisa (I),

The document (in Italian) constituted the first of a series dealing with the application of RELAP code to the design and the operation of the PIPER-ONE loop installed at the Scalbatraio Laboratory managed by IIN (Istituto di Impianti Nucleari) and later on by DCMN (Dipartimento di Costruzioni Meccaniche e Nucleari) of University of Pisa. PIPER-ONE was built in Italy as a consequence of the Three-Mile accident (1979): it aims 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 results of the research documented in the concerned report allowed the best (as far as possible) demonstration of compliance between the loop features (geometry and thermal-hydraulic conditions) and the expected evolution of events in the prototype. A pioneering scaling procedure was adopted and results from the application (shown here) provided a green light to the construction of the facility. 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