A considerable amount of resources have been devoted at international level for establishing and conducting experimental programs in scaled down Integral Test Facilities (ITFs). These were aimed at solving open issues for current Nuclear Power Plant (NPP) types, demonstrating the technical feasibility of innovative designs, and generating reference databases to support code development and assessment. Since the end of the nineties, the maintenance of the competences, including the creation of a new generation of professionals in the area of the nuclear safety, is also a priority objective.

Tens of ITF have been built and operated so far all over the world. Few of them, related to existing water reactor technology, are currently in operation (e.g., ATLAS, PMK, PKL-III, and ROSA IV) or under refurbishment (e.g., PACTEL, PSB-VVER). Some others are constructed or under design and are focused on innovative water reactor concepts (e.g., MASLWR, SPES-3).

The experimental data from such facilities are applicable to full-scale NPP conditions, provided that the test facilities and the initial and boundary conditions of experiments are properly scaled. They are also fundamental for supporting the development and for demonstrating the reliability of computer codes, which is, in general, a regulatory requirement. However, often the results from test facilities cannot be directly applied to a plant, including the “reference” plant for the facility design. Applications of computer codes to accident analyses require the implicit assumptions that these codes have the capabilities to scale up phenomena and processes from test facilities to full-scale plant conditions; this is not ensured a priori.

In view of the above, it has been decided to bring out this special issue which aimed at documenting the present scientific and technical status and recent advances in relation to the subject.

The special issue will include a few, invited, overview papers plus scientific and technical contributions, not limited in numbers. All papers will be subject to the usual reviewing procedure. Potential topics include, but are not limited to:

• New or refurbished ITF design and construction
• Recent ITF experimental program
• Experimental investigations in ITF
• Design of experimental facilities
• Scaling issue related to both the representativeness of the phenomena in the facility as well as the applicability of the codes
• Standard problems and benchmarks
• Code assessment and validation

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/stni/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: